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The Treatment Mechanism of an Interspinous Process Implant for Lumbar Neurogenic Intermittent Claudication
Abstract
The spinal canal and neural foramina dimensions of cadaver lumbar spines were quantified during flexion and extension using magnetic resonance imaging before and after placement of an interspinous process implant.
To quantify the effect of the implant on the dimensions of the spinal canal and neural foramina during flexion and extension.
Lumbar neurogenic intermittent claudication symptoms are typically exacerbated during extension and relieved during flexion. It is understood that the dimensions of the spinal canal and neural foramen increase in flexion and decrease in extension. The authors hypothesized that an interspinous process implant would significantly prevent narrowing of the canal and foramina in extension and have no significant effect in flexion.
Eight L2-L5 specimens were positioned to 15 degrees of flexion and 15 degrees of extension using a positioning frame. Each specimen was magnetic resonance imaged with and without an interspinous implant (X STOP) placed between the L3-L4 spinous processes. Canal and foramina dimensions were compared between the intact and implanted specimens using a repeated measures analysis of variance with a level of significance of 0.05.
In extension, the implant significantly increased the canal area by 18% (231-273 mm), the subarticular diameter by 50% (2.5-3.7 mm), the canal diameter by 10% (17.8-19.5 mm), the foraminal area by 25% (106-133 mm), and the foraminal width by 41% (3.4-4.8 mm).
The results of this study show that the X STOP interspinous process implant prevents narrowing of the spinal canal and foramina in extension.
... The narrowed spinal canal and general spondylosis are the source of neurogenic claudication, radicular and low back pain. 2 Surgical techniques for spinal canal decompression are aimed to decompress subsequent nerve roots within the vertebral recesses and foramina. These procedures have demonstrated effectiveness in reducing chronic pain and claudication. ...
... These procedures have demonstrated effectiveness in reducing chronic pain and claudication. 2 One possible alternative to mild-to-moderate lumbar stenosis is the use of an interspinous process device (IPD), known as a "Knowles plug" which was first introduced by Knowles in 1950. 3 Existing evidence supports the application of IPDs as an acceptable strategy in the management of patients with lumbar spondylosis and stenosis. ...
... 4 Compared to decompression and fusion, IPD surgery has better pain relief and higher improvements in disability with a lower incidence of complications. 5 Biomechanically, IPDs ensure dynamic stabilization and prevent the protrusion of the yellow ligament into the spinal canal during extension. 2 Various manufactured IPDs have different degrees of range of motion restriction and stress over the disc at the instrumented level. 6 Even though IPDs have been used in many centers around the world, there is still no clear consensus or protocol to use them as a first-choice treatment for foraminal stenosis. ...
Aim
Interspinous process device (IPD) placement is an attractive treatment option for lumbar spinal and foraminal stenosis. The goal of the treatment is to release the stress on facets joints as well as decompress the nerve roots by enlarging the intervertebral foramina and narrowed canal recesses.
Purpose
To evaluate possible structural changes in the lumbar spine after implantation of an IPD on operated and adjacent segments.
Patients and Methods
Twenty-two patients were enrolled in the study. Preoperative MRI scans of the lumbar spine evaluated recess and foraminal stenosis prior to the application of an IPD. CT exams were performed and morphometric measurements were made to assess the size of intervertebral foramina after implantation on the operated and adjacent segments.
Results
Statistically significant enlargements in diameter and surface area of the intervertebral foramen were seen at the operating level. On the right and left sides, foraminal enlargement after the procedure was 1 mm in diameter. The average enlargement of the foramina surface area at the level of implantation was 10 mm². The median interspinous distance was significantly enlarged by 3.5 mm. No significant changes in adjacent segments were observed. Clinical improvement was confirmed by the Oswestry Disability Index (ODI) and visual analog scale (VAS). Preoperative disability was reduced (mean ODI from 70.5 (12.25) to 49.5 (23.75)), as well as back pain (mean VAS from 8.0 (1.7) to 4.4 (2.6)) and pain in lower limbs (mean VAS from 7.4 (1.9) to 3.8 (2.9)).
Conclusion
Decompression surgery using an IPD is effective in the treatment of lumbar foraminal and canal stenosis. It provides relief of symptoms in short-term observation through enlargement of intervertebral foramina and decompression of neural roots. It reduces overload of facet joints of the operated segment and does not decrease the size of the intervertebral foramina and disc heights of adjacent segments.
... Interspinous process devices (IPD) are minimally invasive interspinous process implants that can provide symptom relief in LCS (4). Despite increasing use, the efficacy and safety of ISS over open decompression techniques are still debated. ...
... The principle behind surgically treating LCS is decompression of central canal and foramen by preventing lordosis, and providing distraction of posterior elements (4). NC secondary to LCS is shown to be posture-dependent, where symptoms such as lower limb paraesthesia, pain and hypoesthesia are exacerbated in extension and relieved in flexion, known as the "shopping cart sign" (12). ...
... By doing so, ligamentum flavum is stretched and its thickness reduced. Eventually, diameter of spinal canal is enlarged whilst allowing flexion to relieve the compression of nerve roots (4,15). It is noted that motion preservation at instrumented levels alleviate the stress concentrated at adjacent levels, thus reducing risk of adjacent level spondylosis (4,15,16) (Figure 1). ...
Minimally invasive interspinous process devices (IPD), including interspinous distraction devices (IDD) and interspinous stabilizers (ISS), are increasingly utilized for treating symptomatic lumbar canal stenosis (LCS). There is ongoing debate around their efficacy and safety over traditional decompression techniques with and without interbody fusion (IF). This study presents a comprehensive review of IPD and investigates if: (I) minimally invasive IDD can effectively substitute direct neural decompression and (II) ISS are appropriate substitutes for fusion after decompression. Articles published up to 22nd January 2020 were obtained from PubMed search. Relevant articles published in the English language were selected and critically reviewed. Observational studies across different IPD brands consistently show significant improvements in clinical outcomes and patient satisfaction at short-term follow-up. Compared to non-operative treatment, mini-open IDD was had significantly greater quality of life and clinical outcome improvements at 2-year follow-up. Compared to open decompression, mini-open IDD had similar clinical outcomes, but associated with higher complications, reoperation risks and costs. Compared to open decompression with concurrent IF, ISS had comparable clinical outcomes with reduced operative time, blood loss, length of stay and adjacent segment mobility. Mini-open IDD had better outcomes over non-operative treatment in mild-moderate LCS at 2-year follow-up, but had similar outcomes with higher risk of re-operations than open decompression. ISS with open decompression may be a suitable alternative to decompression and IF for stable grade 1 spondylolisthesis and central stenosis. To further characterize this procedure, future studies should focus on examining enhanced new generation IPD devices, longer-term follow-up and careful patient selection.
... The increased prevalence of degenerative lumbar diseases has been well discussed in the past few years as life expectancy has increased. In addition to decompressive lumbar surgery and minimally invasive techniques, implantation of IPDs can act as an adjunct since they are designed under the idea of restoring the foraminal and disc height, unloading axial pressure on the facet joints, and preserving partial sagittal mobility [17]. While Caserta et al. first proposed that DIAM could benefit a certain group of patients suffering from low back pain, the indications for DIAM implantation varied [18]. ...
... Our study also recorded changes in the neuroforamen during extension on radiographs because bulging of the ligamentum flavum in this posture could easily cause NIC. The enlarged extensional foraminal area in our study was compatible with the results of previous literature, showing that DIAM can prevent narrowing of the foramina at the instrumented level [17]. ...
... The increase in MRI disc height and foraminal volume suggests that DIAM was capable of preventing disc degeneration and relieving nerve compression. This result was in accordance with the results of previous in vivo studies [8,17]. In contrast, disc volume in 3D assessments did not reach a similar effect at the implanted level. ...
Background and objectives: The prevalence of degenerative lumbar spine diseases has increased. In addition to standard lumbar decompression and/or fusion techniques, implantation of interspinous process devices (IPDs) can provide clinical benefits in highly selected patients. However, changes in spinal structures after IPD implantation using magnetic resonance imaging (MRI) have rarely been discussed. This volumetric study aimed to evaluate the effect of IPD implantation on the intervertebral disc and foramen using three-dimensional assessment. Materials and Methods: We retrospectively reviewed patients with lumbar degenerative disc diseases treated with IPD implantation and foraminotomy and/or discectomy between January 2016 and December 2019. The mean follow-up period was 13.6 months. The perioperative lumbar MRI data were processed for 3D-volumetric analysis. Clinical outcomes, including the Prolo scale and visual analog scale (VAS) scores, and radiographic outcomes, such as the disc height, foraminal area, and translation, were analyzed. Results: Fifty patients were included in our study. At the one-year follow-up, the VAS and Prolo scale scores significantly improved (both p < 0.001). The disc height and foraminal area on radiographs also increased significantly, but with limited effects up to three months postoperatively. MRI revealed an increased postoperative disc height with a mean difference of 0.5 ± 0.1 mm (p < 0.001). Although the mean disc volume difference did not significantly increase, the mean foraminal volume difference was 0.4 ± 0.16 mm3 (p < 0.05). Conclusions: In select patients with degenerative disc diseases or lumbar spinal stenosis, the intervertebral foramen was enlarged, and disc loading was reduced after IPD implantation with decompression surgery. The 3D findings were compatible with the clinical benefits.
... The concept behind the use of ISS is to avoid pathological movement of the segment and avoid the complications of fusion [19]. ISS have been used for a variety of indications including, stabilizing of mild instability, facet unloading, improving sagittal profile, decompression of neural foramen, improving disc load [20,21]. These devises have been known to be useful in cases of mild to moderate lumbar stenosis ISS results in expansion of the spinal canal between 18% and 23%, with differences between the standing and seated neutral position at 23 and 21%, respectively [21][22][23]. ...
... ISS have been used for a variety of indications including, stabilizing of mild instability, facet unloading, improving sagittal profile, decompression of neural foramen, improving disc load [20,21]. These devises have been known to be useful in cases of mild to moderate lumbar stenosis ISS results in expansion of the spinal canal between 18% and 23%, with differences between the standing and seated neutral position at 23 and 21%, respectively [21][22][23]. The foraminal area and width also increases by average 25% and 40% respectively [21,24]. ...
... These devises have been known to be useful in cases of mild to moderate lumbar stenosis ISS results in expansion of the spinal canal between 18% and 23%, with differences between the standing and seated neutral position at 23 and 21%, respectively [21][22][23]. The foraminal area and width also increases by average 25% and 40% respectively [21,24]. ...
Study design:
Observational Study.
Objective:
The primary objective was to determine if there were differences in spine structure measures between experimental postures and standard supine posture MRIs.
Methods:
Thirty-four low back pain patients were included. MRI was taken in 6 experimental postures. The dependent measures includes sagittal view anterior (ADH), middle and posterior disc heights, thecal sac width, left/right foraminal height (FH). In the axial view: disc width, left and right foraminal height. Measures were done L3/L4, L4/L5 and L5/S1. Each subject served as their own control. Spine measurements in the experimental posture were compared to the same measures in the standard supine posture.
Results:
94% inter-observer reliability was seen. In the sagittal and axial view, 55 of the 108 and 11 of the 18 measures were significantly different. In sagittal view: a) ADH was significantly smaller in the sitting flexed posture by 2.50 mm ± 0.63 compared to the supine posture; b) ADH in sitting neutral posture was significantly smaller than the standard posture by 1.97 mm ± 0.86; c) sitting flexed posture showed that bilateral FH measures were significantly different; d) Bilateral FH was larger in the sitting neutral posture compared to the standard supine posture by 0.87 mm ± 0.17.
Conclusions:
This research quantifies the differences in spine structure measures that occur in various experimental postures. The additional information gathered from an upright MRI may correlate with symptoms leading to an accurate diagnosis and assist in future spine research.
... If a patient only has localized back pain or mild lateralized symptoms without neurologic findings or neurogenic claudication, and does not have confirmatory elevated scores on the ZCQ, surgically invasive procedures may not be indicated, but rather physical therapy or epidural steroid blocks. A minimum of six months of conservative treatment is the norm before surgical intervention is considered [10][11][12][13][14]. Different physicians are now being trained to perform procedures for LSS including interventional pain physicians and neuro-interventional radiologists who may not be as aware of the significance of the different radiologic findings in LSS, the evaluation of instability, and clinical variables and how the clinical testing must be integrated in evaluating patients with LSS before any surgical procedure is considered or performed. ...
... Movement and especially alignment in extension greater than 3-5 mm or 50% of the existing listhesis is felt to be indicative of instability [7][8]. Clinical symptoms in patients with lumbar spinal stenosis are typically aggravated by standing and spinal extension, and it is hypothesized that spinal extension causes 'buckling' of the ligamentum flavum into the posterior lumbar canal, that is already anatomically narrowed, positionally aggravating the compression and symptoms [9,11]. Standing flexion and extension MRI scans show worsening of posterior ligamentous compression with spinal extension giving support to these clinical observations [6][7]. ...
... Previously, spinal decompression with or without fixation was performed only by neurological surgeons or orthopedic spine surgeons. Less invasive procedures have been developed that in selected cases have equivalent outcomes with good five year followup, using specific radiologic and clinical criteria [11][12][13][14]. Now, these minimally invasive procedures are being taught to and performed by pain physicians, anesthesiologists and interventional neuro-radiologists. ...
Radiologic findings in combination with clinical symptoms are critical in the diagnosis and evaluation of the severity of lumbar spinal stenosis (LSS) as well as the need for surgical treatment. Dynamic radiographs, computerized tomography (CT), and magnetic resonance imaging (MRI) each provide different but interrelated pieces of information in the patient with lumbar spinal stenosis. Making a treatment decision based only on one of the radiographic studies may negatively affect the treatment outcome. Minimal procedures are predicated on identifying and performing surgery on a limited segment of the lumbar spinal canal affected by the stenosis compared to what occurs during open surgery where the judgment of the spine surgeon often expanded the decompression area based on real-time intra-operative findings correlated with radiologic findings of stenosis. As newer, less invasive procedures are gaining acceptance for surgical treatment of spinal stenosis with symptomatic claudication, radiologic studies become more critical in selecting the correct procedure since there may be no or minimal surgical visual confirmation of the pathology. This article will review how the finding of spinal deformity and motion, canal dimensions, viewed in multiple planes and the presence of facet fluid impact treatment decisions. Differences in these abnormal radiologic findings can affect the selection of surgical procedures ranging from open decompression with pedicle fixation, decompression with interlaminar stabilization, minimally invasive lumbar decompression, and percutaneous interspinous implants providing distraction without decompression. With the development of less invasive procedures, lumbar spinal stenosis is being evaluated and treated not only by spine surgeons but also by interventional pain and neuroradiology physicians that may not be totally familiar with the complexity of the pathology and neuro-radiology of LSS. Each radiologic study provides different information. The goal of this report is to provide a framework for the use of studies such as plain X-rays, dynamic films, MRI, and CT scans as well as the importance of different views, and how to use them in evaluating the abnormal radiologic anatomy seen with LSS and in selecting the most appropriate procedure.
... Interspinous fixation devices have been studied to show advantages over transpedicular screw fixation such as reduced postoperative back pain from less lateral muscle dissection, short operative time, and reduced cephalad ASD (20). ISP devices placed between the spinous process can increase the central canal area up to 18%, the foraminal area by 25% and the foraminal width by 43% in cadaveric spine studies (32). ISPs were approved for patient use for over a century (32) and the evolution to new designs have resulted in IFD devices that are contoured to be lamina and provide extension block in addition to fixation of the spinous processes and stabilization of the facets. ...
... ISP devices placed between the spinous process can increase the central canal area up to 18%, the foraminal area by 25% and the foraminal width by 43% in cadaveric spine studies (32). ISPs were approved for patient use for over a century (32) and the evolution to new designs have resulted in IFD devices that are contoured to be lamina and provide extension block in addition to fixation of the spinous processes and stabilization of the facets. These novel IFD devices such as InSpan in this study are designed to provide relief for patients suffering from LSS worse on extension but also who have back pain from degenerative disc and facets and who may have facet tropism due to difference in angulation of the facets on either side (33). ...
Background
Spinal stenosis treatment includes laminectomies with or without fusion or with interspinous distraction with or without fixation. Lack of published data on interspinous fixation devices (IFD) at L5–S1 is less considered as an option due to the smaller anatomical S1 spinous process and the higher stresses from the immobile sacrum. Our objective was to evaluate the outcomes of an IFD used as a stand-alone treatment for spinal stenosis at L5–S1 and L4–5 compared to historical data on open laminectomies.
Methods
Prospective comparative cohort study (Level 2) looking at collected preoperatively and postoperatively Visual Analog Scores (VAS) and Oswestry Disability Index (ODI) data, complications, and revision rates on 100 consecutive patients with spinal stenosis treated with midline decompression and InSpan (InSpan LLC, Malden, MA, USA) IFD, at L5–S1 and L4–5, up to five-year follow-up. All patients were treated by a single surgeon in an academic private practice. Historical published outcome data for open laminectomies were compared.
Results
Among the 100 patients, 45 underwent surgery at L5–S1 with a mean VAS pain score that decreased by 75% and ODI improved by 63% (P<0.001). Fifty-five patients had surgery at L4–5 with mean VAS and ODI scores improved by 80% and 66% (P<0.001) respectively. Preoperative and postoperative ODI and preoperative VAS scores were similar at L5–S1 and L4–5, however, postoperative VAS scores were significantly less for L4–5 versus L5–S1 (P<0.01). All surgeries were completed in less than one hour. There was a total of one L4–5 revision (1.8%) and two L5–S1 revisions (4.4%). Comparable laminectomy data showed decrease in VAS and ODI scores by 51% and 62% (P<0.05). The reoperation rate for laminectomies at five to ten years varied up to 24%.
Conclusions
Spinal stenosis patients treated with midline decompression and InSpan IFD, used as a stand-alone treatment for interspinous-interlaminar fixation, at L4–5 and L5–S1, showed improved outcome scores and low complication and revision rates at five years and were comparable to historical open laminectomy data. InSpan is a successful substitute for laminectomies in selected patients and was performed in less than 60 minutes. We recommend choosing the appropriately sized implant to achieve adequate distraction decompression to avoid recurrent symptoms.
... Considering the age of the population affected by this pathology, interspinous process spacers (IPS) have been proposed as an intermediate treatment between medical and surgical treatment [7], or as an alternative to surgery in patients with major contraindications [8]. These devices take many forms, but fundamentally are all based on spacing out the interspinous processes in order to stretch the ligamentum flavum, enlarge the vertebral foramina and reduce posterior discal protrusion, thereby reducing the degree of vertebral canal stenosis [9]. They were first introduced as a less invasive form of open surgery, but in the last few years, new percutaneous IPS have emerged in the market, proposing a further minimally invasive procedure. ...
... Our finding is in accordance with another previous study that assessed these variations on CT or radiographs [11,20]. These measures were acquired in decubitus and the IPS effect may be even more evident in upright and extended positions, where it receives part of the posterior column load and maintains a relative local flexion, reducing flavum ligament protrusion and foraminal stenosis [9,21]. ...
Purpose
To evaluate clinical and radiological outcomes of a series of patients treated with a removable percutaneous interspinous process spacer (IPS) (LobsterProject® Techlamed®) for symptomatic degenerative lumbar spinal stenosis (DLSS).
Methods
All patients treated in two centres with this IPS during 2019 were retrospectively reviewed. Procedures were performed under deep sedation or general anaesthesia by two interventional radiologists. Patients were clinically evaluated before intervention and at 3-month follow-up with Visual Analog Scales for pain (VAS), Oswestry Disability Index (ODI) and radiologically with MRI or CT scans. Neural foramina were independently measured for each patient on pre- and post-procedural CT scans by two radiologists.
Results
Fifty-nine patients were treated in the selected period of which fifty-eight had complete documentation (mean age 71.2 ± 9.2 years [55–92], 32 males, 26 females). Forty-eight interventions were performed under deep sedation and ten under general anaesthesia, without procedural complications. Clinical follow-up at 3 months showed a significant reduction of pain (VAS from 83 ± 9 to 29 ± 19, − 65%; p < 0.001) and an improvement in functional outcomes (ODI from 31 ± 12 to 13 ± 10%, − 58%; p < 0.001). There was one case of unsatisfactory positioning post procedure, two cases of posterior migration at 3-month follow-up and one case of spinous process fracture. Mean neural foramina area increased from 77 ± 23 to 95 ± 27 mm² (+ 26%; p < 0.001) with very good inter-observer reliability (Cronbach’s alpha = 0.899).
Conclusion
Percutaneous minimally invasive insertion of a removable IPS device demonstrates a favourable safety profile, good clinical outcomes at 3 months, and apparent anatomical increase in foraminal dimensions.
Trial registration
ClinicalTrials.gov Identifier: NCT05203666—Release Date: 21st January 2022, retrospectively registered.
... Previous studies regarding SP morphometry have focused essentially on age-related bony changes [1,2], gender discrepancy, and the differences between lumbar levels [3][4][5]. Others have investigated SP biomechanical properties [6,7] and their morphology regarding the spine devices and surgical techniques [8][9][10]. ...
... The interspinous process decompression devices (e.g., XSTOP) provide a minimally invasive technique for DLSS patients with mild symptoms [27]. These devices reduce extension at the symptomatic level(s), intrathecal pressure, and facet load; stretch the ligamentum flavum; and enlarge the neural foramens, thus improving spinal stenosis symptoms [10,28,29]. In 2012, Kim et al. have previously reported a strong association between degenerative spondylolisthesis and SP fractures in patients who underwent X-stop devices [9]. ...
The aim of this study is to determine the sagittal inclination of lumbar spinous processes (SPs) in individuals with degenerative lumbar spinal stenosis (DLSS). It is a retrospective computerized tomography (CT) study including 345 individuals divided into two groups: control (90 males, 90 females) and stenosis (80 males and 85 females. The SP inclination was measured in the midsagittal plane from L1 to L5 levels. Stenosis males (L3-L5) and females (L1, L4) manifested significantly greater SP inclination compared to their counterparts in the control group. Males had significantly horizontal SP orientation compared to females (L1, L2). We also found that SP inclination became steeper as we descend caudally. This study indicates that SP inclinations are significantly associated with DLSS.
... The symptoms of neurogenic claudication are exacerbated upon extension and are relieved on resting or flexion of the lumbar spine [25]. The use of interspinous process spacers between the spinous processes allows flexion, axial rotation, and lateral bending but prevents extension of the stenotic levels of the spine [26]. ...
... Richards et al. [26] performed a study to quantify the effects of interspinous process spacer implants (X-STOP) on the dimensions of the spinal canal and neural foraminal during flexion and extension. Canal and foramina dimensions were compared with intact and implanted specimens positioned at 15 flexion and 15 extension. ...
Objective:
Objective Interspinous process spacers are used in the treatment of lumbar spinal stenosis by preventing extension at the implanted level and reducing claudication, which is a common symptom of lumbar spinal stenosis. This review assessed the current safety and performance of lumbar spinal stenosis treatments and the biomechanical effects of spinal position, range of motion, and the use of interspinous process spacers.
Method:
Method EMBASE and PubMed were searched to find studies reporting on the safety and performance of nonsurgical treatment, including physical therapy and pharmacological treatment, and surgical treatment, including direct and indirect lumbar decompression treatment. Results were supplemented with manual searches to include studies reporting on the use of interspinous process spacers and the review of biomechanical testing performed on the Superion device.
Results:
Results The effects of spinal position in extension and flexion have been shown to have an impact in the variation in dimensions of the spinal canal and foramina areas. Overall studies have shown that spinal positions from flexion to extension reduce the spinal canal and foramina dimensions and increase ligamentum flavum thickness. Biomechanical test data have shown that the Superion device resists extension and reduces angular movement at the implantation level and provides significant segmental stability.
Conclusions:
Conclusions Superion interspinous lumbar decompression is a minimally invasive, low-risk procedure for the treatment of lumbar spinal stenosis, which has been shown to have a low safety profile by maintaining sagittal alignment, limiting the potential for device dislodgment or migration, and to preserve mobility and structural elements.
... Cadaveric spine studies suggested that an interspinous process device (IPD) could improve the central canal area in up to 18% [6]. At the beginning of this century, IPDs were approved for patient use [6] and introduced as a less invasive surgical alternative. ...
... Cadaveric spine studies suggested that an interspinous process device (IPD) could improve the central canal area in up to 18% [6]. At the beginning of this century, IPDs were approved for patient use [6] and introduced as a less invasive surgical alternative. Questions regarding safety, efficacy, and cost-effectiveness are still unanswered. ...
Background
Degenerative lumbar spinal stenosis is a condition related to aging in which structural changes cause narrowing of the central canal and intervertebral foramen. It is currently the leading cause for spinal surgery in patients over 65 years. Interspinous process devices (IPDs) were introduced as a less invasive surgical alternative, but questions regarding safety, efficacy, and cost-effectiveness are still unanswered.
Objectives
The aim of this study was to provide complete and reliable information regarding benefits and harms of IPDs when compared to conservative treatment or decompression surgery and suggest directions for forthcoming RCTs.
Methods
We searched MEDLINE, EMBASE, Cochrane Library, Scopus, and LILACS for randomized and quasi-randomized trials, without language or period restrictions, comparing IPDs to conservative treatment or decompressive surgery in adults with symptomatic degenerative lumbar spine stenosis. Data extraction and analysis were conducted following the Cochrane Handbook. Primary outcomes were pain assessment, functional impairment, Zurich Claudication Questionnaire, and reoperation rates. Secondary outcomes were quality of life, complications, and cost-effectiveness. This systematic review was registered at Prospero (International prospective register of systematic reviews) under number 42015023604.
Results
The search strategy resulted in 17 potentially eligible reports. At the end, nine reports were included and eight were excluded. Overall quality of evidence was low. One trial compared IPDs to conservative treatment: IPDs presented better pain, functional status, quality of life outcomes, and higher complication risk. Five trials compared IPDs to decompressive surgery: pain, functional status, and quality of life had similar outcomes. IPD implant presented a significantly higher risk of reoperation. We found low-quality evidence that IPDs resulted in similar outcomes when compared to standard decompression surgery. Primary and secondary outcomes were not measured in all studies and were often published in incomplete form. Subgroup analysis was not feasible. Difficulty in contacting authors may have prevented us of including data in quantitative analysis.
Conclusions
Patients submitted to IPD implants had significantly higher rates of reoperation, with lower cost-effectiveness. Future trials should improve in design quality and data reporting, with longer follow-up periods.
... By distracting the spinous processes with a spacer or implant at the stenotic level, local kyphosis is created, leading to an increase in the diameter of the spinal canal at that level by 18%-22%. 21,30,37,40 Interspinous implants are hypothesized to exert their bio-mechanical effect by preventing hyperextension without limiting other spinal motions. 23,26 In extension, the spinal canal is compressed by the posterior annulus fibrosis anteriorly and by the ligamentum flavum posteriorly. ...
... Richards et al. obtained MRI scans of 8 lumbar spine specimens before and after interspinous spacer placement to investigate the ef- fect of distraction on spinal and foraminal dimensions. 30 They found that after IPD insertion, the canal area was increased by 18% and the foraminal area by 25% during extension. However, this study should be interpreted with caution, as others have found "a weak correlation between the magnitude of radiographic improvement and the extent of pain relief (VAS) and clinical signs or symptoms." ...
Interspinous process devices (IPDs) have been developed as less-invasive alternatives to spinal fusion with the goal of decompressing the spinal canal and preserving segmental motion. IPD implantation is proposed to treat symptoms of lumbar spinal stenosis that improve during flexion. Recent indications of IPD include lumbar facet joint syndrome, which is seen in patients with mainly low-back pain. Long-term outcomes in this subset of patients are largely unknown. The authors present a previously unreported complication of coflex (IPD) placement: the development of a large compressive lumbar synovial cyst. A 64-year-old woman underwent IPD implantation (coflex) at L4-5 at an outside hospital for low-back pain that occasionally radiates to the right leg. Postoperatively, her back and right leg pain persisted and worsened. MRI was repeated and showed a new, large synovial cyst at the previously treated level, severely compressing the patient's cauda equina. Four months later, she underwent removal of the interspinous process implant, bilateral laminectomy, facetectomy, synovial cyst resection, interbody fusion, and stabilization. At the 3-month follow-up, she reported significant back pain improvement with some residual leg pain. This case suggests that facet arthrosis may not be an appropriate indication for placement of coflex.
... Retrospective research has shown that interspinous fixation/fusion devices can reduce pain, painrelated disability, and LSS symptoms, and improve quality of life in patients with LSS. [17][18][19][20][21][22][23][24][25] Interspinous devices have demonstrated the ability to enlarge the spinal canal and neural foraminal areas, 5,30,[32][33][34][35][36] while the proposition that posterior element distraction can unload the posterior annulus is more speculative. 5 In addition to potentially reducing posterior disc bulging, posterior disc unloading may reduce mechanical stimulation of imbedded nociceptive nerve endings in the posterior portion of the disc. ...
Purpose
An early-stage, multi-centre, prospective, randomised control trial with five-year follow-up was approved by Health Research Authority to compare the efficacy of a minimally invasive, laterally implanted interspinous fixation device (IFD) to open direct surgical decompression in treating lumbar spinal stenosis (LSS). Two-year results are presented.
Patients and Methods
Forty-eight participants were randomly assigned to IFD or decompression. Primary study endpoints included changes from baseline at 8-weeks, 6, 12 and 24-months follow-ups for leg pain (visual analogue scale, VAS), back pain (VAS), disability (Oswestry Disability Index, ODI), LSS physical function (Zurich Claudication Questionnaire), distance walked in five minutes and number of repetitions of sitting-to-standing in one minute. Secondary study endpoints included patient and clinician global impression of change, adverse events, reoperations, operating parameters, and fusion rate.
Results
Both treatment groups demonstrated statistically significant improvements in mean leg pain, back pain, ODI disability, LSS physical function, walking distance and sitting-to-standing repetitions compared to baseline over 24 months. Mean reduction of ODI from baseline levels was between 35% and 56% for IFD (p<0.002), and 49% to 55% for decompression (p<0.001) for all follow-up time points. Mean reduction of IFD group leg pain was between 57% and 78% for all time points (p<0.001), with 72% to 94% of participants having at least 30% reduction of leg pain from 8-weeks through 24-months. Walking distance for the IFD group increased from 66% to 94% and sitting-to-standing repetitions increased from 44% to 64% for all follow-up time points. Blood loss was 88% less in the IFD group (p=0.024) and operating time parameters strongly favoured IFD compared to decompression (p<0.001). An 89% fusion rate was assessed in a subset of IFD participants. There were no intraoperative device issues or re-operations in the IFD group, and only one healed and non-symptomatic spinous process fracture observed within 24 months.
Conclusion
Despite a low number of participants in the IFD group, the study demonstrated successful two-year safety and clinical outcomes for the IFD with significant operation-related advantages compared to surgical decompression.
... PID is placed between adjacent spinous processes at the level or levels of symptomatic DLSS under local anesthesia and mild/deep sedation using fluoroscopic guidance [8]. Cadaveric studies demonstrate a shift of the forces to the posterior column with a reduction of the discal pressure [9]; segmental enlargement of the spinal canal unloads the facet joints and posterior annulus, resulting in restoration of normal foraminal height [10,11]. ...
Purpose
To evaluate safety and efficacy of the novel percutaneous interspinous device (PID) for the treatment of symptomatic degenerative lumbar spinal stenosis (DLSS) in 3 different centers.
Methods
From November 2016 to March 2020, 255 patients (male 125, mean age 71.2 years old range 49–91 years old) with neurogenic claudication, confirmed by electromyography, related to mono or bi-segmental lumbar central canal and/or foraminal stenosis were enrolled in the study. Magnetic resonance (MR) and/or computer tomography (CT), physical exam, and Visual Analogue Scale (VAS) and Zurich Claudication Questionnaire (ZCQ) were performed before and 6 months after the procedure. All treatments were performed under fluoroscopic guidance with local anesthesia and mild sedation. Technical success was defined as correct placement of the Lobster® (Demetrios Medical, Firenze, Italy) PID as demonstrated by computer tomography (CT) performed immediately after treatment; spinoplasty was performed in selected patients.
Results
PID placement was accomplished with a 99.6% success rate (257/258). The one device that was not implanted was due to a spinous process fracture. In 28 patients, more than 1 device was implanted in the same session (max 3 PIDs); 6 patients required a second implant in different session. A total of 172 prophylactic spinoplasties were performed (59.3%). No major complications occurred; 3 device misplacements were successfully treated with percutaneous retrieval and new device deployment. 99.6% of patients experienced clinical improvement.
Conclusion
Lobster PID is an effective and safe minimally invasive decompression method for central canal and neural foraminal stenosis when patients are correctly selected.
... Year of publication Total citations 1 Zucherman et al [12] A multicenter, prospective, randomized trial evaluating the X STOP interspinous process decompression system for the treatment of neurogenic intermittent claudication-two-year follow-up results Spine Article 2005 330 2 Chou et al [13] Surgery for low back pain a review of the evidence for an American Pain Society Clinical Practice Guideline Spine Review 2009 306 3 Wilke et al [14] Biomechanical effect of different lumbar interspinous implants on flexibility and intradiscal pressure European Spine Journal Article 2008 251 4 Sénégas et al [15] Mechanical supplementation by nonrigid fixation in degenerative intervertebral lumbar segments: the Wallis system European Spine Journal Article 2002 234 5 Richards et al [16] The treatment mechanism of an interspinous process implant for lumbar neurogenic intermittent claudication Spine Article 2005 229 6 Zucherman et al [17] A prospective randomized multi-center study for the treatment of lumbar spinal stenosis with the X STOP interspinous implant: ...
In recent years, with the introduction of the concept of lumbar non-fusion, the interspinous device has emerged. The purpose of this study is to bibliometrically analyze the state, areas of interest, and emerging trends in the usage of interspinous devices for the treatment of lumbar degeneration disease, as well as related research fields. Between January 1, 2000 and June 14, 2023, a comprehensive collection of publications on the topic of interspinous devices in the treatment of lumbar degenerative disease (IDTLDD) was procured from the Web of Science. A bibliometric analysis and visualization were subsequently conducted, utilizing various tools including HisCite, VOSviewer, CiteSpace, and bibliometrix package. This process involved the gathering of data on the country, institution, author, journal, reference, and keywords. A comprehensive analysis of 401 publications sourced from 149 journals was conducted, with 1718 authors affiliated with 1188 institutes across 240 countries/regions. Notably, the United States emerged as the leading contributor with 134 published articles on interspinous devices in the treatment of lumbar degenerative disease (33.42%). The most productive institution was Capital Medical University, with (10, 2.49%) publications. The author with the highest publication output was Block, Jon E, with 10 publications. European Spine Journal demonstrated the highest level of productivity, with a publication of (n = 39, 9.73%). The term "X-Stop" was the most frequently utilized keyword, followed by "Lumbar spinal stenosis." The study identified various topics of current interest, such as "Invasive decompression" and "Coflex." The present study provides a comprehensive survey of research trends and developments in the application of interspinous device for the treatment of lumbar degenerative diseases, including relevant research findings and collaborative efforts among authors, institutions, and countries.
... The interspinous process system (ISPS) has been widely used as a non-fusion procedure and has achieved good results. The procedure can open the spinous process gap and limit the extension of the corresponding segment to a certain extent, thereby increasing the spinal canal and intervertebral foramen and reducing the stress on the posterior facet joints and anterior foramina 65 . The overall lumbar ROM in the Coflex group was relatively good. ...
Multi-segmental lumbar degenerative disease, including intersegmental disc degeneration, is found in clinical practice. Controversy still exists regarding the treatment for cross-segment degeneration. Oblique Lateral Interbody Fusion (OLIF) with several internal fixations was used to treat cross-segment lumbar degenerative disease. A whole lumbar spine model was extracted from CT images of the whole lumbar spine of patients with lumbar degeneration. The L2-3 and L4-5 intervertebral spaces were fused with OLIF using modeling software, the Pedicle screws were performed on L2-3 and L4-5, and different internal fixations were performed on L3-4 in Finite Element (FE) software. Among the six 10 Nm moments of different directions, the L3-4 no surgery (NS) group had the relatively largest Range of Motion (ROM) in the whole lumbar spine, while the L2-5 Long segmental fixation (LSF)group had the smallest ROM and the other groups had similar ROM. The ROM in the L1-2 and L5-S1 was relatively close in the six group models, and the articular cartilage stress and disc stress on the L1-2 and L5-S1 were relatively close. In contrast, the L3-4 ROM differed relatively greatly, with the LSF ROM the smallest and the NS ROM the largest, and the L3-4 Coflex (Coflex) group more active than the L3-4 Bacfuse (Bacfuse) group and the L3-4 translaminar facet screw fixation (TFSF) group. The stress on the articular cartilage and disc at L3-4 was relatively greater in the NS disc and articular cartilage, and greater in the Coflex group than in the Bacfuse and TFSF groups, with the greatest stress on the internal fixation in the TFSF group, followed by the Coflex group, and relatively similar stress in the Bacfuse, LSF, and NS groups. In the TFSF group, the stress on the internal fixation was greater than the yield strength among different directional moments of 10 Nm, which means it is unsuitable to be an internal fixation. The LSF group had the greatest overall ROM, which may lead to postoperative low back discomfort. The NS group has the greatest overall ROM, but its increased stress on the L3-4 disc and articular cartilage may lead to accelerated degeneration of the L3-4 disc and articular cartilage. The Coflex and Bacfuse groups had a reduced L3-4 ROM but a greater stress on disc compared to the LSF group, which may lead to disc degeneration in the long term. However, their stress on the articular cartilage was relatively low. Coflex and Bacfuse can still be considered better surgical options.
... However, the indications for PDS are still to be identified. Regarding IDD they are mostly used additionally to decompressive procedures in order to prevent iatrogenic instability and to keep the spine in a rather flexed position and the spinal canal and neural foramina open [2][3][4][5][6]. Several surgeons use IDD as "stand alone" implants without decompression because of the possibility of enlargement of the spinal canal by stretching the ligamentum flavum and the posterior longitudinal ligament [7,8]. ...
Introduction: Posterior dynamic stabilization (PDS) can be based on interspinous distraction devices (IDD). The goals of these implants are maintaining or restoring intervertebral range of motion (ROM) in a controlled fashion and avoiding a complete restriction of mobility. Clinical and radiological data with the Wallis® spacer as one type of IDD have been rarely reported. The goal of this study was to present clinical and radiological data including roentgen stereophotogrammetric analysis (RSA) after a short- to mid-term follow-up period. Patients and Methods: 10 patients were included in this prospective monocentric study and had PDS of the lumbar spine with an IDD (Wallis® spacer). Before and soon after operation and 3, 6, and 12 months later clinical and radiological evaluations were performed. Pain and disability were analyzed by use of visual analog scale for back and leg pain, Oswestry Disability Index, Roland-Morris Disability Questionnaire and Short-Form-36 Health Survey. The ROM of the operated levels and the total lumbar spine was determined by use of lateral functional x-ray images with calculation of the differences of the segmental and total lumbar spine angles in flexion and extension. Furthermore, RSA was used to measure the segmental ROM. Results: After a follow-up of 12 months, the results of the pain intensity and the disability and health related quality of life scores showed statistical significant improvement. The segmental angles of the operated levels demonstrated statistical significant reduction in ROM during the different follow-up examinations. The discrepancy of the conventionally determined segmental angles and the data measured by RSA were low with a mean of 1.77°. The mean total lumbar spine angles did not change statistically significantly during the postoperative controls. Conclusions: According to the radiological results of this study, the used implant leads to a posterior dynamic stabilization. The clinical findings are promising, but they are to be interpreted with caution because of the small number of patients and the lack of a control group.
... In a cadaver study, the authors [13] observed that distraction opens the canal and foramen. In a cadaveric study [14], the results showed that for a single segment fusion there was no difference in stability of the fusion between pedicle screw fixation and interspinal fixation. ...
Introduction:
Generally, interspinal distractor fixation devices are used for severe low back pain associated with neurogenic claudication, and radiculopathy with central or lateral recess stenosis and/or foraminal narrowing. In this paper, the authors result in cases of severe low back pain and lumbar radiculopathy in whom this device was used with excellent results.
Method:
This is a retrospective study. Patients were contacted via phone call and their pain score and other data were recorded at different timelines. The final data presented in this paper are the data collected at the final follow-up that ranges from 14 months to 24 months. Surgeries were performed in the outpatient setting and although no identifiable patient information is included in this paper, yet, patients were asked for their verbal consent. The patient data are only included if verbal consent was obtained.
Results:
Over the past 24 months, 13 patients with disc protrusion and/or central and/or foraminal spinal stenosis were treated with this procedure. Follow-up ranges from 14 months to 24 months with a median of 19 months, male/female ratio of 6/7, and a median age of 68 years. There were no complications or reoperation. Statistical analysis showed significant improvement in the Numeric Pain Rating Scale (NPRS) for back and radicular leg pain (p-value = 0.000552 for back pain and p-value = 0.000291 for radicular leg pain).
Conclusion:
The system reported in this paper is a solid fixation system that works both as a distractor and internal decompressor of the spinal canal. It is simple to use and safe. Though the number of patients is small, statistically significant improvement was reported at a median follow-up of 19 months.
... IPD is a minimally invasive indirect decompression implant for patients with LSS associated with or without low-grade DS. IPD insertion can expand the narrowed canals with an increment ranging from 18% to 23%, varying according to different positions [97,98]. Foramina expansion can be achieved in terms of area and width [99]. ...
Lumbar spinal stenosis (LSS), which often occurs concurrently with degenerative spondy-lolisthesis (DS), is a common disease in the elderly population, affecting the quality of life of aged people significantly. Notwithstanding the frequently good effect of conservative therapy on LSS, a minority of the patients ultimately require surgery. Surgery for LSS aims to decompress the narrowed spinal canals with preservation of spinal stability. Traditional open surgery, either pure decompression or decom-pression with fusion, was considered effective for the treatment of LSS with or without DS. However, the long-term clinical outcomes of traditional open surgery are still unclear. Moreover, the disadvantages of conventional open surgery are extensive, examples including tissue injuries or secondary instability, with Jun Zhang, Tang-Fen Liu, and Hua Shan contributed equally to the work.
... Non-fusion techniques use implants that can either function as an elastic tether which allows controlled motion, or as a rigid interspinous/interlaminar device that limits spinal extension, and, therefore, prevents central canal and foraminal narrowing. [65] Examples of the former are Dynesys ( there was a 47% incidence of radiographic ASD. [66] The comparative benefit of non-fusion techniques over other conventional methods is also not clear. ...
Degenerative spondylolisthesis is one of the commonest spinal pathologies encountered in the aging population. The clinical presentation of degenerative spondylolisthesis can be highly variable, and a large proportion of patients can be managed non-operatively. Operative treatment is reserved for patients with activity limiting disability. Decompression alone can be offered to patients with no radiological or clinical evidence of segmental instability. Fusion procedures have shown high rates of clinical success, although long-term effects such as adjacent segment degeneration have spurred the evolution of non-fusion technologies. These newer options have shown evidence of motion preservation, although long-term clinical benefits have yet to be confirmed.
... In case of the patient's symptoms being not alleviated through a flexed posture, the traditional decompression surgery must be performed. Therefore IPDs are designed as a spacer to offload facet joints and release the entrapped spinal root nerves and as the intralaminar stabilizer [3][4][5][6][7]. ...
Recently, various designs and material manufactured interspinous process devices (IPDs) are on the market in managing symptomatic lumbar spinal stenosis (LSS). However, atraumatic fracture of the intervening spinous process has been reported in patients, particularly, double or multiple level lumbar decompression surgery with IPDs. This study aimed to biomechanically investigate the effects of few commercial IPDs, namely DIAM TM , Coflex TM , and M-PEEK, which were implanted into the L2-3, L3-4 double-level lumbar spinal processes. A validated finite element model of musculoskeletal intact lumbar spinal column was modified to accommodate the numerical analysis of different implants. The range of motion (ROM) between each vertebra, stiffness of the implanted level, intra stress on the intervertebral discs and facet joints, and the contact forces on spinous processes were compared. Among the three implants, the Coflex system showed the largest ROM restriction in extension and caused the highest stress over the disc annulus at the adjacent levels, as well as the sandwich phenomenon on the spinous process at the instrumented levels. Further, the DIAM device provided a superior loading-sharing between the two bridge supports, and the M-PEEK system offered a superior load-sharing from the superior spinous process to the lower pedicle screw. The limited motion at the instrumented segments were compensated by the upper and lower adjacent functional units, however, this increasing ROM and stress would accelerate the degeneration of un-instrumented segments.
... In this study, the facet loads at adjacent levels of the TAU model increased marginally more than that of the SPIRE model during extension motion. The aim of the IPDs is to alleviate facet joint pain; therefore, surgeons should consider the facet loads at surgical and adjacent levels [29]. However, the facet loads at adjacent levels of the TAU model were lower than that of the PSF model. ...
Purpose
This study aimed to investigate the biomechanical effects of a newly developed interspinous process device (IPD), called TAU. This device was compared with another IPD (SPIRE) and the pedicle screw fixation (PSF) technique at the surgical and adjacent levels of the lumbar spine.
Materials and methods
A three-dimensional finite element model analysis of the L1-S1 segments was performed to assess the biomechanical effects of the proposed IPD combined with an interbody cage. Three surgical models—two IPD models (TAU and SPIRE) and one PSF model—were developed. The biomechanical effects, such as range of motion (ROM), intradiscal pressure (IDP), disc stress, and facet loads during extension were analyzed at surgical (L3-L4) and adjacent levels (L2-L3 and L4-L5). The study analyzed biomechanical parameters assuming that the implants were perfectly fused with the lumbar spine.
Results
The TAU model resulted in a 45%, 49%, 65%, and 51% decrease in the ROM at the surgical level in flexion, extension, lateral bending, and axial rotation, respectively, when compared to the intact model. Compared to the SPIRE model, TAU demonstrated advantages in stabilizing the surgical level, in all directions. In addition, the TAU model increased IDP at the L2-L3 and L4-L5 levels by 118.0% and 78.5% in flexion, 92.6% and 65.5% in extension, 84.4% and 82.3% in lateral bending, and 125.8% and 218.8% in axial rotation, respectively. Further, the TAU model exhibited less compensation at adjacent levels than the PSF model in terms of ROM, IDP, disc stress, and facet loads, which may lower the incidence of the adjacent segment disease (ASD).
Conclusion
The TAU model demonstrated more stabilization at the surgical level than SPIRE but less stabilization than the PSF model. Further, the TAU model demonstrated less compensation at adjacent levels than the PSF model, which may lower the incidence of ASD in the long term. The TAU device can be used as an alternative system for treating degenerative lumbar disease while maintaining the physiological properties of the lumbar spine and minimizing the degeneration of adjacent segments.
... Interspinous process device (IPD) could improve the central canal area in up to 18% in cadaveric spine studies (3). IPDs were approved for patient use at the beginning of the century (3) and introduced as a less invasive surgical alternative. ...
Background:
Lumbar spinal stenosis is treated with decompression directly such as laminectomies and indirectly with an interspinous device through distraction and extension block. Interspinous devices (IPD) have also been used as an adjunct to spinal fusion. However, the design for IPD to treat spinal stenosis does not fixate the spine while the design for spinal fusion is designed to fixate the spine. There is a paucity of data on a single device that has been used for both fusion and stenosis. Authors aim to demonstrate the long-term outcomes of interspinous fixation at L4-5 for degenerative spinal stenosis.
Methods:
We evaluated patients with spinal stenosis and degenerative disc disease who were treated with open decompression and distraction of the spinous processes at L4-L5 using an interspinous device. All patients complained of lower back pain and neurogenic claudication. This is a retrospective review of prospectively collected data (level 3) under an IRB approved study cohort. The charts of patient undergoing lumbar decompression with Interspinous Distraction, Fixation using InSpan device (INSPAN LLC) in an outpatient setting were reviewed with over a 5-year follow-up period.
Results:
122 surgical cases of lumbar decompression with interspinous fixation, spanning between the timeframe of September 2011 to October 2016. A total of 56 patients had instrumentation at L4-L5. Total female population was 46%. The median age of the patients included in the population was 50.9±10.7 years with a median BMI of 24.8±11.4 kg/m2. Two-year VAS and ODI showed significant improvement from 8.1±1.2 to 1.5±1.1 and 42.9±14.3 to 14.8±5.1. All surgeries were completed in less than one hour. There was a total of 1 revision case with removal of INSPAN and open hemilaminectomy decompression.
Conclusions:
Long term results demonstrated improved outcomes in patients who underwent Interspinous distraction decompression in an ambulatory surgery center using the INSPAN IPD at L4-L5 for Degenerative Spinal Stenosis. There was one revision converted to hemilaminectomy. There were no complications or blood transfusions.
... Interspinous process devices (IPD) are minimally invasive devices that are able to decrease facet join overload through a "shock-absorber" mechanism shifting forces to the posterior column with a reduction of discal pressure [11]; segmental enlargement of the spinal canal with the unloading of the facet joint and posterior annulus, resulting in the restoration of normal foraminal height, was reported in cadaveric studies after IPD placement [12,13]. ...
A comprehensive description of the literature regarding interspinous process devices (IPD) mainly focused on comparison with conservative treatment and surgical decompression for the treatment of degenerative lumbar spinal stenosis. Recent meta-analysis and articles are listed in the present article in order to establish IPD pros and cons.
... In contrast to an interspinous spacer, which acts more passively as a blocking device, the ISPF device can be utilized to actively increase focal lordosis through compression or focal kyphosis through distraction. Additionally, distraction can serve to relieve facet loads and open the spinal canal and neural foramens [25][26][27]. Interestingly, the distraction of the spinous processes using the ISPF device not only increased the compressive IB load but did so in exponential fashion. ...
Background
Rigid interspinous process fixation (ISPF) may serve as a minimally disruptive adjunct to lumbar interbody fusion. Previous biomechanical assessments of ISPF have demonstrated particularly advantageous outcomes in stabilizing the sagittal plane. However, ISPF has not been well characterized in regard to its impact on interbody load, which has implications for the risk of cage migration or subsidence, and sagittal alignment. The purpose of this study was to biomechanically assess in vitro the interbody load (IBL), focal lordosis (FL), and spinous process loading generated by in situ compression/distraction with a novel ISPF device capable of incremental in situ shortening/extension. Bilateral pedicle screw fixation (BPSF) was used as a control.
Methods
Two fresh frozen human lumbar spines were thawed and musculature was removed, leaving ligaments intact. Seven functional spinal units were iteratively tested, which involved a standard lateral discectomy, placement of a modified lateral cage possessing two load cells, and posterior fixation. BPSF and ISPF were performed at each level, with order of fixation was randomized. BPSF was first performed with maximum compressive exertion followed by 75% exertion to represent clinical application. The ISPF device was implanted at a neutral height and incrementally shortened/extended in situ in 1-mm increments. IBL and FL were measured under each condition. Loads on the spinous processes were estimated through bench-top mechanical calibration.
Results
No significant differences in IBL were observed, but the ISPF device produced a significantly greater change in FL compared to the clinically relevant BPSF compression. IBL, as a function of ISPF device height, expressed linear behavior during compression and exponential behavior during distraction.
Conclusions
The novel ISPF device produced clinically effective IBL and FL, performing well in comparison to BPSF. Additionally, incremental ISPF device manipulation demonstrated predictable and clinically safe trends regarding loading of the interbody space and spinous processes.
... With the development of minimally invasive spine surgery, interspinous devices have been used mostly for the treatment of moderate degenerative lumbar stenosis with neurogenic claudication [16,20] and in the presence of low-grade degenerative slips [7,14]. It may be further used to supplement other procedures such as lateral lumbar interbody fusion, transforaminal lumbar interbody fusion, or endoscopic surgery. ...
Purpose
To measure the morphological dimensions of the spinous process (SP) and interspinous space, and provide a basis for the development of interspinous devices for the Korean or East Asian populations.
Methods
We retrospectively analyzed the anatomical parameters of 120 patients. The parameters included height, length, and width of SP, interspinous distance (supine, standing, and dynamic), cortical thickness of SP, and spino-laminar (S-L) angle. Correlations between measurements, age, and gender were investigated.
Results
The largest height, length, and cortical thickness and S-L angle were noted at L3. The largest width was observed at S1. The interspinous distance decreased significantly from L2–3 to L5–S1 and was significantly larger in the supine than in standing posture for L5–S1. Cortical thickness was gradually tapered from the anterior to the posterior position. The S-L angle at L2 and L3 was similar and significantly decreased from L3 to S1. An increased trend in width with aging and a decreased trend in distance (supine) were noted. A significant increase in height, length, and distance in males compared with females was also observed.
Conclusions
The interspinous space is wider at the anterior, and the cortex is thicker anteriorly. Accordingly, it appears that the optimized implant position lies in the interspinous space anteriorly. The varying interspinous space with different postures and gradually narrowing with age suggest the need for caution when sizing the device. Gender differences also need to be considered when designing implantable devices.
... Interspinous implants are used for motion-preserving stabilization of primarily posterior lumbar spinal pathologies like spinal stenosis or facet joint arthritis [25][26][27]. In the interspinous "U" device, the height of the same distracts the foraminal opening; the "U" shape is designed to allow controlled movement in forward and backward bending [28][29][30]. ...
Introduction
Interspinous devices (ISDs) and interlaminar devices (ILDs) are marketed as alternatives to conventional surgery for degenerative lumbar conditions; comparisons with decompression alone are limited. The present study reviews the extant literature comparing the cost and effectiveness of ISDs/ILDs with decompression alone.
Methods
Articles comparing decompression alone with ISD/ILD were identified; outcomes of interest included general and disease-specific patient-reported outcomes, perioperative complications, and total treatment costs. Outcomes were analyzed at <6 weeks, 3 months, 6 months, 1 year, 2 years, and last follow-up. Analyses were performed using random effects modeling.
Results
Twenty-nine studies were included in the final analysis. ILD/ISD showed greater leg pain improvement at 3 months (mean difference, −1.43; 95% confidence interval, [−1.78, −1.07]; P < 0.001), 6 months (−0.89; [−1.55, −0.24]; P = 0.008), and 12 months (−0.97; [−1.25, −0.68]; P < 0.001), but not 2 years (P = 0.22) or last follow-up (P = 0.09). Back pain improvement was better after ISD/ILD only at 1 year (−0.87; [−1.62, −0.13]; P = 0.02). Short-Form 36 physical component scores or Zurich Claudication Questionnaire (ZCQ) symptom severity scores did not differ between the groups. ZCQ physical function scores improved more after decompression alone at 6 months (0.35; [0.07, 0.63]; P = 0.01) and 12 months (0.23; [0.00, 0.46]; P = 0.05). Oswestry Disability Index and EuroQoL 5 dimensions scores favored ILD/ISD at all time points except 6 months (P = 0.07). Reoperations (odds ratio, 1.75; [1.23, 2.48]; P = 0.002) and total care costs (standardized mean difference, 1.19; [0.62, 1.77]; P < 0.001) were higher in the ILD/ISD group; complications did not differ significantly between the groups (P = 0.41).
Conclusions
Patient-reported outcomes are similar after decompression alone and ILD/ISD; the observed differences do not reach accepted minimum clinically important difference thresholds. ISD/ILDs have higher associated costs and reoperation rates, suggesting current evidence does not support ILD/ISDs as a cost-effective alternative to decompression alone.
Türkiye’de Spinal Enstrümantasyonun Tarihi Sait NADERİ Mekanik ve Biyomekaniğin Temelleri Bozkurt Burak ÖZHAN Spinal İmplantların Elemanları Cumhur KILINÇER Lisa FERRARA Metalurji ve Alaşım Bilgisi Enver ATİK Klasik Üretim Yöntemleri Enver ATİK Katmanlı İmalat (Kİ) - Additive Manufacturing (AM) Cüneyt TEMİZ Peyker TEMİZ Cerrahide 3D Printer Destekli İmplant Üretimi ve Kaplama Yöntemleri Hasan Emre AYDIN Deniz AKKAYA Ali ARSLANTAŞ Biyouyumlu Malzemeler ve Mekanik Özellikleri Melis YURDDAŞKAL Hülya DURMUŞ Biyomalzemelerin Karakterizasyonu Hüseyin Erdem YALKIN Patoloji ve Enstruman Biyomekaniği Serdar ÇEVİK Hakan HANIMOĞLU Hakan BOZKUŞ Cerrahi Teknik - Enstruman İlişkisi Ömer AKÇALI Enstrüman, Füzyon, Psödoartroz Burak TAHMAZOĞLU Taha Şükrü KORKMAZ Murat HANCI Osteoporotik Omurga Cerrahisinde Kullanılan İmplantlar Varol AYDIN Kadir KOTİL Geçiş Bölgelerinde Enstrüman Sorunları, Yük Yoğunlaşması ve Proksimal Bileşke Sorunları Seymur NİFTALİYEV Erkan KAPTANOĞLU Spinal Enstrümantasyonda Yetmezlik Mehdi HEKİMOĞLU Ahmet Tulgar BAŞAK Ali Fahir ÖZER Enstrüman Kurgusunun Komplikasyonlarla İlişkisi Muhammed Taha ESER Süleyman Rüştü ÇAYLI Spinal İmplant Teknolojisi : Gelişmeler Cüneyt TEMİZ Peyker TEMİZ Mehmet EMİNOĞLU Ömer Emre YAĞLI Spinal Araştırma Geliştirme, Sertifikasyon ve İnovasyon Süreçleri Cüneyt TEMİZ Mehmet EMİNOĞLU Ömer Emre YAĞLI Burak TÜLÜ Spinal Cerrahide Yeni Teknolojik Gelişmeler; Teletıp, Robotik Sistemler ve Genişletilmiş Gerçeklik-Karma Gerçeklik Macit TERZİ Emre BAHİR METE Murat ZAİMOĞLU Yusuf Şükrü ÇAĞLAR Spinal Cerrahide Enstrümantasyon ile İlgili Hekim Sorumluluğu Serdar IŞIK
This chapter presents a comprehensive review of disk degeneration and lumbar stenosis disease, diagnosis, and percutaneous image-guided decompressive spinal techniques.
Spinal fusion is performed to eliminate motion at a degenerated or unstable segment. However, this is associated with loss of motion at the fused levels and increased stress on adjacent levels. Motion-preserving implants have been designed in effort to mitigate the limitations of fusion. This review will focus on posterior spinal motion-preserving technologies. In the cervical spine, laminoplasty is a posterior motion-preserving procedure used in the management of myelopathy/cord compression. In the lumbar spine, motion-sparing systems include interspinous process devices (also referred to as interspinous process spacers or distraction devices), posterior dynamic stabilization devices (also referred to as pedicle screw/rod fixation-based systems), and posterior element replacement systems (also referred to as total facet replacement devices). Knowledge of the intended physiologic purpose, hardware utilized, and complications is important in the assessment of imaging in those who have undergone posterior motion preservation procedures.
Objective:
Lumbar spinal stenosis (LSS) is a common and debilitating condition that is increasing in prevalence in the world population. Surgical decompression is often standard treatment when conservative measures have failed. Interspinous distractor devices (IDDs) have been proposed as a safe alternative; however, the associated cost and early reports of high failure rates have brought their use into question. The primary objective of this study was to determine the cost-effectiveness and long-term quality-of-life (QOL) outcomes after treatment of LSS with the X-Stop IDD compared with surgical decompression by laminectomy.
Methods:
A multicenter, open-label randomized controlled trial of 47 patients with LSS was conducted; 21 patients underwent insertion of the X-Stop device and 26 underwent laminectomy. The primary outcomes were monetary cost and QOL measured using the EQ-5D questionnaire administered at 6-, 12-, and 24-month time points.
Results:
The mean monetary cost for the laminectomy group was £2712 ($3316 [USD]), and the mean cost for the X-Stop group was £5148 ($6295): £1799 ($2199) procedural cost plus £3349 mean device cost (£2605 additional cost per device). Using an intention-to-treat analysis, the authors found that the mean quality-adjusted life-year (QALY) gain for the laminectomy group was 0.92 and that for the X-Stop group was 0.81. The incremental cost-effectiveness ratio was -£22,145 (-$27,078). The revision rate for the X-Stop group was 19%. Five patients crossed over to the laminectomy arm after being in the X-Stop group.
Conclusions:
Laminectomy was more cost-effective than the X-Stop for the treatment of LSS, primarily due to device cost. The X-Stop device led to an improvement in QOL, but it was less than that in the laminectomy group. The use of the X-Stop IDD should be reserved for cases in which a less-invasive procedure is required. There is no justification for its regular use as an alternative to decompressive surgery.Clinical trial registration no.: ISRCTN88702314 (www.isrctn.com).
Interspinous and interlaminar devices are a type of motion-preserving implant designed to provide symptomatic relief of claudicatory lumbar spinal stenosis. These devices work via indirect decompression by maintaining mild flexion of a stenotic spinal segment, subsequently increasing the cross-sectional area of the spinal canal. The distractive force applied by the device, and the subsequent height restoration, is believed to be the main mechanism through which it functions. While these devices may primarily indirectly decompress a spinal motion segment via distraction, they also serve as an alternative to fusion by providing “dynamic stabilization” of a motion segment after direct decompression. The dynamic stabilization and distraction via the use of these spacers may also serve to diminish discogenic back pain from degenerative disc disease and facet degeneration. Benefits of these devices are that they can be implanted with a minimal degree of destruction to the local anatomy, they are more motion preserving than fusion, and they can be easily removed in cases of implant failure.
Minimally invasive spine surgery (MISS) has evolved dramatically over the past several decades in an attempt to minimize approach-related trauma, expedite hospital discharge, and optimize clinical and functional outcomes. Although the goals of MISS are to perform an efficient target surgery with minimal iatrogenic injury, there are a variety of approaches and implant-related complications associated with this surgical strategy. This chapter will discuss the learning curve associated with MISS, in addition to exploring the various technical challenges and complications associated with some of the most common MISS procedures.
Objective:
The objective of this cadaveric biomechanical study was to compare the area of the foraminal space during motion in the intact condition, after direct decompression via foraminotomy, and after indirect decompression via anterior lumbar interbody spacer insertion.
Methods:
Eight (8) L5-S1 cadaver specimens were used for testing. Each specimen was tested in the intact state, after posterior foraminotomy, and after standalone anterior lumbar interbody fusion (ALIF). Each specimen was 3D imaged under neutral loading, flexion and extension. The 3D images were analyzed for changes in the foraminal area under each loading scenario. A repeat-measures design was utilized. Outcome measures from testing included the frequency in which an increase in cross-sectional area was observed, as well as the percent increase of the foraminal area for each surgical group and loading direction.
Results:
Direct foraminotomy and ALIF maintained the foraminal space during initial distraction under no loading with areas 99.7% and 96.5% of the native foraminal area, respectively (p=0.955 and p=0.455). Direct foraminotomy increased the foraminal area significantly during flexion to 112.2% of the area before motion (p=0.008) while ALIF did not. Direct foraminotomy significantly decreased the foraminal area during extension to 89.2% of the area before motion (p=0.006). ALIF, however, maintained its initial distraction during extension with 98.2% of the area before motion (p=0.808).
Conclusions:
ALIF maintains the foraminal area in extension while direct posterior foraminotomy does not.
Low back pain, radicular leg pain, and lumbar spinal stenosis are the most common of all chronic pain disorders. Discogenic pain is related to distress of annular fibers and tears, whereas spinal stenosis is related to reduction of the spinal canal dimensions and compression of the neural elements; radicular pain is mainly related to disc herniation and is initially managed conservatively. The percutaneous minimally invasive approach in discogenic and radicular pain is designed to reduce the volume of the nucleus pulposus in patients with failure of medical and physical treatment prolonged for at least 6 weeks.
The peculiarity of extreme lateral interbody fusion (LLIF) is the achievement of indirect neural decompression of the spinal canal while distracting the intervertebral disc space using an interbody cage. In this manuscript we will review the potentials and limitations of this technique when treating degenerative disc disease of the lumbar spine. A literature search of the PubMed-National Library of Medicine was performed. Only articles in English were included. The current available literature demonstrates that LLIF is an effective method to decompress foraminal and central canal stenosis. Based on the current available literature LLIF effects on lateral recess stenosis are less consistent. The aim of this review is to provide with a thorough overview of the latest literature available and provide the audience with targeted-oriented published results that will eventually improve the decision-making process when using the LLIF technique.
There is a growing impetus to treat aging as a disease in the quest to significantly extend the human life span through cellular regeneration methods. This approach, while promising, overlooks the fact that the evolutionary adaptation to bipedalism puts the human body in a distinctively vulnerable biomechanical and functional position. Orthograde human posture places unusually-high axial compressive loads on the weight-bearing joints of the skeleton, resulting in arthritic deterioration with aging. The effects are particularly robust in the lumbar spine were age-related degeneration, most commonly lumbar spinal stenosis (LSS), is ubiquitous among the elderly. It is postulated that re-establishing a favorable mechanical environment via interventions that unload the affected spinal joint complex may mitigate and potentially reverse the structural damage that is the cardinal pathoanatomical feature of this disease. The hypothesis of this paper is that a minimally-invasive surgical procedure, interspinous process decompression (IPD), which utilizes a stand-alone intervertebral spacer, effectively unloads the diseased spinal motion segment providing a healthy micro-environment to reverse and repair age-related and genetic deterioration of the spinal motion segment. Several lines of supporting evidence are provided from long-term follow-up results of a randomized controlled trial of IPD safety and effectiveness of the Superion® device including clinical outcomes, reoperation rates, opioid analgesic usage and advanced imaging utilization. All of these outcomes show uniquely-favorable trends with time that imply that the benefits of IPD are structural. The compendium of evidence suggests that IPD offers both a durable palliative effect due to direct blocking of back extension and a disease-modifying effect due to unloading of the spinal joint complex.
Degenerative lumbar stenosis can lead to symptoms of neurogenic claudication and lumbar radiculopathy. Lumbar stenosis can be caused by static compression of the neural elements in the central canal, along the lateral recess, and in the neuroforamen, as well as by dynamic changes to the total area of the central canal and neuroforamen. Previously, surgical options for the treatment of degenerative lumbar stenosis were primarily based on direct posterior open decompressions and fusions. However, novel techniques of indirect decompression have now been developed that restore disc height to increase the area of the central canal and neuroforamen and address the dynamic aspect of stenosis, while avoiding the extensive soft tissue injury involved in posterior open decompressions and fusions. Interbody fusions and interspinous devices are two methods of indirect decompression that are being commonly used.
In this study, we provide a broad overview of the advantages, disadvantages, indications, evidence, and complications of ALIF, LLIF, and OLIF, as well as interspinous devices including Coflex. Though there is limited comparative evidence demonstrating that one approach is superior to another in terms of clinical and radiographic outcomes, evidence does show that interbody techniques are effective at treating lumbar stenosis by increasing the total area of the central canal and neuroforamen while having high fusion rates. Though the newer generation of interspinous devices have lower failure rates than their predecessors, they still are not comparable to the interbody devices in terms of long term outcomes. The optimal approach for the indirect treatment of lumbar stenosis therefore depends on multiple variables, including but not limited to the spinal level of disease, the anatomy of the individual patient, the pathology being treated, and the familiarity of the surgeon.
Background:
Recently, interspinous stabilization with the interspinous process device (IPD) has become an alternative to treat lumbar spinal stenosis. The biomechanical influence of different design features of IPDs on intradiscal pressure (IDP) and facet joint force (FJF) has not been fully understood. The aim of this study was to investigate the biomechanical performance of different IPDs using finite element (FE) method.
Methods:
A FE model of the L1-5 segments was developed and validated. Four surgical FE models were constructed by inserting different implants at the L3-4 segment (Coflex-F, DIAM, Wallis, and pedicle screw system). The 4 motion modes were simulated.
Results:
The IPDs decreased range of motion (ROM) at the surgical level substantially in flexion and extension, but little influence was found in lateral bending and torsion. Compared with the DIAM and Wallis devices, the Coflex-F device showed advantages in stabilizing the surgical level, especially in flexion and extension, while it increased FJF at adjacent levels by 26%-27% in extension. Among the 3 IPDs, the DIAM device exhibited the most comparable ROM, IDP, and FJF at adjacent levels compared with the intact lumbar spine. The influence of the Wallis device was between that of the Coflex-F and DIAM devices.
Conclusions:
Compared with rigid fixation, the IPDs demonstrated less compensation at adjacent levels in terms of ROM, IDP, and FJF, which may lower the incidence of adjacent segment degeneration in the long term.
Introduction
To investigate the short- and medium-term efficacy of inter-spinal distraction fusion (ISDF) for lumbar disc herniation with a spinal internal fixation device, the BacFuse Spinous Process Fusion Plate.
Methods
Ninety-five patients who received ISDF between January 2014 and January 2015 were included for the current retrospective study. The symptoms and imaging results before surgery, immediately after surgery, at six months, and at the last follow-up were assessed using the leg visual analogue scale (VAS), Oswestry disability index (ODI), and 12-item short-form survey (SF-12). The intra-operative intervertebral angle (IA), anterior disk height (ADH), posterior disk height (PDH), foramina height (FH), foramina width (FW), and range of motion (ROM) were assessed using X-rays. The foramina and herniated disc area were assessed using computed tomography (CT).
Results
The leg VAS, ODI, and SF-12 were significantly improved after surgery. All indices except ADH were also significantly improved after surgery. PDH and FH increased by 15.5% (P < 0.001) and 9.7% (P < 0.001) at the last follow-up. ROM was statistically different from before surgery. CT images indicated that the herniated disc area decreased by 3.1%, while the foramina areas increased by 5.7% at the last follow-up. 92.6% patients demonstrated successful outcome.
Conclusions
ISDF significantly alleviated the clinical symptoms, improved spinal structure, and partially retracted the herniated disc. Our findings imply that ISDF is an effective minimally invasive procedure in the treatment of lumbar disc herniation.
Lumbar spinal stenosis is a disease in which degenerated discs, ligamentum flavum, facet joints, while aging, lead to a narrowing of the space around the neurovascular structures of the spine. This article presents a meta-analysis of literature data on epidemiology, causes, pathogenesis, diagnosis and various types of treatment of lumbar spinal stenosis.
Lumbar Spinal Stenosis (LSS) is becoming increasingly prevalent in the ageing population and surgery is regarded as the gold standard treatment after conservative measures have failed. Many patients do not improve however, and the complication rates are high. Interspinous distraction devices (IDDs) have been proposed as a safe alternative however their cost and their failure rate has made their use controversial. No UK data exists to date with regards to the cost-effectiveness of the surgical management of IDDs in LSS and there is a lack of long term follow up. Objective – To determine the cost-effectiveness and quality of life after the treatment of LSS with the X-Stop device and laminectomy. Method – A randomised control trial of 47 patients with LSS (26 laminectomy and 21 X-Stop). The primary outcome was cost and quality of life measured using EQ5D. Other clinical outcomes were measured using SF36, ZCQ, ODI and QBPDS. Secondary measures included, operating time, length of stay and complication rates. Patients were followed up at 6 months, 12 months and 24 months. Results – The mean cost of the Laminectomy group was £2,711.8 and the mean cost of the X-Stop group was £5,148 (£1,799 plus the cost of the device £2,605 per device). Using intention to treat analysis, the mean QALY gain for the laminectomy group was 0.92 and for the X-Stop group was 0.81. The incremental cost effectiveness ratio was £-22,247.27. The complication rate for the laminectomy group was 19.2% vs 9.5% for the X-Stop group. Conclusion – Laminectomy is more cost-effective than X-Stop insertion for the treatment of LSS, mainly due to the high cost of the device. The X-Stop device does not replace a laminectomy as gold standard treatment however it should be considered when a less invasive procedure is required.
The purpose of this study was to evaluate physiologic changes of the cross-sectional area of the spinal canal and neural foramina in young asymptomatic volunteers.
Twelve asymptomatic volunteers were examined in a 0.5-T open-configuration MR system. T2-weighted fast spin-echo sequences were obtained in upright neutral, upright flexed, upright extended, and supine extended positions. The cross-sectional area of the spinal canal and the thickness of the ligamentum flavum were measured on angled axial images at the L4-L5 level. The anteroposterior diameter of the spinal canal and cross-sectional areas of the neural foramina were measured on sagittal images from L1 to S1.
At disk level, the cross-sectional area of the spinal canal varied significantly between body positions, most notably between the upright flexed (mean, 268 mm2) and the upright extended (mean, 224 mm2) positions (p < .0001). The maximum thickness of the ligamenta flava increased in the extended positions (p < .0001). The cross-sectional area of the neural foramina underwent position-dependent variations of as much as 44.4%. The smallest cross-sectional areas were found in the extended positions.
In asymptomatic volunteers, MR imaging is able to show position-dependent changes in the cross-sectional areas of the spinal canal and the intervertebral foramina. The extended positions best reveal important findings.
The authors report their experience with the treatment of lumbar instability by a kind of spine stabilization. The elastic stabilization, which follows a new philosophy, is obtained by an interspinous device, and should be used alone in degenerative disc disease, recurrent disc herniation and in very low grade instability, or in association with rigid fusion for the prevention of pathology of the border area. In collaboration with bioengineers, we carried out an experimental study on a lumbar spine model in order to calculate stresses and deformations of lumbar disc during simulation of motion, in physiological conditions and when elastic stabilization is combined with rigid fusion. Results suggest that elastic stabilization reduces stresses on the adjacent disc up to 28 degrees of flexion. Based on this preliminary result, we began to use elastic stabilization alone or combined with fusion in 1994. To date, we have performed 82 surgical procedures, 57 using stabilization alone and 25 combined with fusion, in patients affected by degenerative disc disease, disc herniation, recurrence of disc herniation or other pathologies. Clinical results are satisfactory, especially in the group of patients affected by recurrent disc herniation, in whom the elastic device was used alone.
Patients suffering from neurogenic intermittent claudication secondary to lumbar spinal stenosis have historically been limited to a choice between a decompressive laminectomy with or without fusion or a regimen of non-operative therapies. The X STOP Interspinous Process Distraction System (St. Francis Medical Technologies, Concord, Calif.), a new interspinous implant for patients whose symptoms are exacerbated in extension and relieved in flexion, has been available in Europe since June 2002. This study reports the results from a prospective, randomized trial of the X STOP conducted at nine centers in the U.S. Two hundred patients were enrolled in the study and 191 were treated; 100 received the X STOP and 91 received non-operative therapy (NON OP) as a control. The Zurich Claudication Questionnaire (ZCQ) was the primary outcomes measurement. Validated for lumbar spinal stenosis patients, the ZCQ measures physical function, symptom severity, and patient satisfaction. Patients completed the ZCQ upon enrollment and at follow-up periods of 6 weeks, 6 months, and 1 year. Using the ZCQ criteria, at 6 weeks the success rate was 52% for X STOP patients and 10% for NON OP patients. At 6 months, the success rates were 52 and 9%, respectively, and at 1 year, 59 and 12%. The results of this prospective study indicate that the X STOP offers a significant improvement over non-operative therapies at 1 year with a success rate comparable to published reports for decompressive laminectomy, but with considerably lower morbidity.
1. A clinical condition is described in which there are symptoms of compression of the caudal nerve roots on standing or walking, but not at rest. Seven cases are reported.
2. Myelography showed a block in the lumbar region in every case.
3. At operation narrowing of the spinal canal in part of its lumbar course was found.
4. The nature of the abnormality is discussed. It is suggested that the narrowing is due to encroachment on the spinal canal by the articular processes.
Objective. To define the possible mechanism of posture-dependent symptoms of spinal stenosis by measuring the effect of low back posture on morphologic changes of the intervertebral discs and spinal canal in healthy young people. Design. Twenty healthy young volunteers underwent magnetic resonance imaging while supine with their spine in neutral, flexed, extended, and right and left rotational positions. The axial MR images at the middle of the intervertebral discs of L3-4 and L4-5 were analyzed to measure the difference in the size and shape of the intervertebral discs and spinal canal in each posture. Results. Extension or rotation decreased the sagittal diameters and cross-sectional areas of the dural sac and spinal canal and increased the thickness of the ligamentum flavum, whereas flexion had the opposite effects. The gap between the convex posterior disc margin and the anterior margin of the facet joint on each side, represented as the subarticular sagittal diameter, increased with flexion and decreased with extension or rotation. The direction of rotation did not result in asymmetry of the subarticular sagittal diameter, but right rotation caused thickening of the right ligamentum flavum, and vice versa. The shape and dimensions of the disc did not change significantly according to the positions of the low back. Conclusions. With extension or rotation, the thickness of the ligamentum flavum increased and the posterior margin of the intervertebral disc was approximated to the facet joint without any change in shape and size of the disc. These phenomena result in a decrease in the size of the spinal canal and dural sac in extension or rotation postures in young healthy people without disc degeneration, and may explain the posture-dependent symptom of spinal stenosis.
Study Design. A cohort of 100 patients with symptomatic lumbar spinal stenosis, characterized in a previous article, were given surgical or conservative treatment and followed for 10 years. Objectives. To identify the short- and long-term results after surgical and conservative treatment, and to determine whether clinical or radiologic predictors for the treatment result can be defined. Summary of Background Data. Surgical decompression has been considered the rational treatment. However, clinical experience indicates that many patients do well with conservative treatment. Methods. In this study, 19 patients with severe symptoms were selected for surgical treatment and 50 patients with moderate symptoms for conservative treatment, whereas 31 patients were randomized between the conservative (n = 18) and surgical (n = 13) treatment groups. Pain was decisive for the choice of treatment group. All patients were observed for 10 years by clinical evaluation and questionnaires. The results, evaluated by patient and physician, were rated as excellent, fair, unchanged, or worse. Results. After a period of 3 months,relief of pain had occurred in most patients. Some had relief earlier, whereas for others it took 1 year. After a period of 4 years, excellent or fair results were found in half of the patients selected for conservative treatment, and in four fifths of the patients selected for surgery. Patients with an unsatisfactory result from conservative treatment were offered delayed surgery after 3 to 27 months (median, 3.5 months). The treatment result of delayed surgery was essentially similar to that of the initial group. The treatment result for the patients randomized for surgical treatment was considerably better than for the patients randomized for conservative treatment. Clinically significant deterioration of symptoms during the final 6 years of the follow-up period was not observed. Patients with multilevel afflictions, surgically treated or not, did not have a poorer outcome than those with single-level afflictions. Clinical or radiologic predictors for the final outcome were not found. There were no dropouts, except for 14 deaths. Conclusions. The outcome was most favorable for surgical treatment. However, an initial conservative approach seems advisable for many patients because those with an unsatisfactory result can be treated surgically later with a good outcome.
Study Design. In patients with sciatica or neurogenic claudication, the structures in and adjacent to the lumbar spinal canal were observed by computed tomographic myelography or magnetic resonance imaging in psoas‐relaxed position and during axial compression in slight extension of the lumbar spine. Objectives. To determine the mechanical effects on the lumbar spinal canal in a simulated upright position. Summary of Background Data. For years, functional myelographic investigation techniques were shown to be of value in the evaluation of suspected encroachment of the spinal canal. Since the advent of computed tomography and magnetic resonance imaging, there have been few clinical and experimental attempts that have imitated these techniques. The data indicate that the space within the canal is posture dependent. Methods. Portable devices for axial loading of the lumbar spine in computed tomographic and magnetic resonance examinations were developed. Fifty patients (94 sites) were studied with computed tomographic myelography, and 34 patients (80 sites) with magnetic resonance in psoas‐relaxed position followed by axial compression in slight extension. The dural sac cross‐sectional area at L2 to S1, the deformation of the dural sac and the nerve roots, and the changes of the tissues surrounding the canal were observed. Results. In 66 of the investigated 84 patients, there was a statistically significant reduction of the dural sac cross‐sectional area in at least one site during axial compression in slight extension. Of the investigated patients, 29 passed the borderlines for relative (100 mm2) or absolute stenosis (75 mm2) in 40 sites. In 30 patients, there was deformation of the dural sac in 46 sites. In 11 of the patients investigated with magnetic resonance imaging, there was a narrowing of the lateral recess in 13 sites, during axial compression in slight extension. Conclusions. Axial loading of the lumbar spine in computed tomographic scanning and magnetic resonance imaging is recommended in patients with sciatica or neurogenic claudication when the dural sac cross‐sectional area at any disc location is below 130 mm2 in conventional psoas‐relaxed position and when there is a suspected narrowing of the dural sac or the nerve roots, especially in the ventrolateral part of the spinal canal in psoas‐relaxed position. The diagnostic specificity of the spinal stenosis will increase considerably when the patient is subjected to an axial load.
Low back pain with or without radiation into one or both lower extremities has been studied with increasing interest in recent years. That many factors may be involved in the production of this group of symptoms is attested by a voluminous literature.1 Many recent authors have considered ligamentous strain about the lumbosacral and sacro-iliac regions from faulty posture to be the chief etiologic factor.2 Intraspinal pathologic changes have, however, received scant attention.When this syndrome occurs in conjunction with objective neurologic changes, such as sensory or motor loss about the buttock, sexual impotence and possibly sphincteric disturbances, the lesion must be intraspinal, for bony disease peripheral to the neural canal simply cannot produce such a neurologic pattern. Any low intraspinal lesion, herniation of a nucleus pulposus, neoplasm or inflammatory disease may, of course, produce this clinical picture. Our purpose in this report is to discuss an intraspinal lesion
The fallacies of the term stenosis are discussed. Propositions for a more precise definition of the stenotic conditions are given, based on the distinction between transport stenosis and compressive stenosis and their different properties. Uncertainties in the present nomenclature of the various forms of stenosis of the lumbar vertebral canal are discussed. Measuring the diameters of the lumbar vertebral canal, not only in roentgenograms but also during surgery, is an important aid to more precision in nomenclature.
(C) Lippincott-Raven Publishers.
Twenty-two patients with intermittent claudication of the cauda equina have been followed up from 1 to 20 yr. Two patients were not operated upon and their histories are described in detail. The remainder had decompressive laminectomies: 3 of these required further operations and their histories are also described. The post-operative prognosis of this syndrome was very good, total relief occurring in more than half the patients; the remainder were symptom-free for a number of years when they developed either recurrence or other symptoms of lumbar disc disease. The still disputed pathogenesis is discussed, but the authors favour a vascular mechanism operating in a constricted spinal canal, the latter arising on a degenerative basis.
Intermittent claudication from peripheral vascular disease is sometimes difficult to distinguish from similar claudication due to degenerative disease of the lumbar spine. In the present study 26 patients with vascular disease were compared with 23 patients with lumbar degenerative disease. Assessment was by clinical and radiological examination. In the vascular group characteristic distinguishing features were: abnormal foot pulses, arterial bruits, relief of symptoms by standing, a constant claudicating distance and stocking sensory loss. In the lumbar group typical findings were: discomfort on lifting, bending, coughing or sneezing, pain on standing, history of back injury, variable claudicating distance and segmental sensory loss.
Study of autopsy specimens of the lumbar spine makes it possible to construct a spectrum of pathologic change. Progressive degenerative changes in the posterior joints lead to marked destruction and instability. Similar changes in the disc result in herniation, internal disruption, and resorption. Combined changes in posterior joint and disc sometimes produce entrapment of a spinal nerve in the lateral recess, central stenosis at one level, or both of these conditions. Changes at one level often lead, over a period of years, to multilevel spondylosis and/or stenosis. Developmental stenosis is an enhancing factor in the presence of a small herniation or moderate degenerative stenosis. Lesions such as major trauma, spondylolisthesis, those following spinal fusion, Paget's disease, and fluorosis, on occasion act directly to produce central or lateral stenosis.
Neurogenic intermittent claudication is briefly reviewed and correlated with twenty consecutive cases of lumbar spinal canal stenosis. Irreversible damage may occur if surgical decompression is unduly delayed. A unilateral decompression may be sufficient in carefully selected cases.
The authors undertook a morphometric study of the intervertebral foramina in anatomic specimens of spines unaffected by degenerative lesions. They studied the variations in shape and size of 38 intervertebral foramina during flexion-extension movements and following an isolated disc collapse. The cast technique takes into account the bony prominences, the bulge of the disc anteriorly and of the capsulo-ligamentous structures posteriorly. In flexion, all the diameters of the foramina are maximal. In full extension all the diameters decrease significantly: the pedicles come closer together, the disc bulges posteriorly and the ligamentum flavum is pushed forward by the superior articular process of the underlying vertebra. A disc collapse of 4 mm decreases all the diameters, and in this case lumbar extension results in a sufficient decrease of foraminal diameter to threaten the nerve root.
In 12 patients with myelographic evidence of bilateral root involvement at the L3-L4 or L4-L5 levels postmyelographic computerized tomography (CT) studies were performed in flexion and extension. They showed concentric narrowing of the spinal canal in extension and widening with relief of nerve root involvement in flexion. This could be attributed to the presence of marked degenerative hypertrophy of the facet joints, narrowing the available space for dural sac and emerging root sleeves. In extension of the lumbar spine, bulging of the disc toward the hypertrophic facets causes a pincers mechanism at the anterolateral angles of the spinal canal with the risk of bilateral root compression. This mechanism is enhanced in these cases by marked dorsal indentation of the dural sac because of anterior movement of the dorsal fat pad in extension. The authors believe that the radiologically described mechanism forms the anatomic basis of neurogenic claudication and posture-dependent sciatica.
1. The syndrome of spinal stenosis is due to compression of the cauda equina from structural narrowing of the lumbar spinal canal.
2. Patients with this syndrome present symptoms of cauda equina claudication or of unremitting bizarre back pain and sciatica.
3. The compression of the cauda equina is always posterior and postero-lateral and is caused by narrowing of the lateral recesses and of the dorso-ventral diameter of the spinal canal.
4. The diagnosis can be made only by myelography. The only form of successful relief of the nerve root compression in spinal stenosis is adequate lateral and longitudinal decompression.
Ten patients who underwent operation for compression of spinal nerve roots by the ligamentum flavum were followed for five years. Seven patients were completely cured, and definite improvement resulted in three. Diagnosis was made on the basis of duration (5 to 25 years' back pain) and evidence of root compression. Myelography revealed a large posterior indentation under the neural arch resulting in a partial or complete block. The ligamentum flavum seems to be the major cause of root compression in a limited number of patients. The surgical therapy recommended is a total laminectomy with wide resection of the ligamentum flavum and complete disk removal when indicated.
The clinical and radiographic results of lumbar isthmic spondylolisthesis were compared between interspinous block-assisted anterior interbody fusion (block-assist group, n = 16) and anterior interbody fusion with no use of the block (nonassist group, n = 17) with an average follow-up of 7 years (range 1 1/3-13 years). Satisfactory relief of low-back pain, significantly early interbody union (union rate 88%, p < 0.05), and spontaneous fusion of pars defect (fusion rate 44%, p < 0.05) were obtained in the block-assist group. In the nonassist group, interbody union was markedly delayed (p < 0.05), the union rate was 53%, and spontaneous fusion of the pars was found in 12% of patients. The overall clinical results at final follow-up in both groups did not show a statistically significant difference, but the results tended to be superior in the block-assist group.
A prospective cohort study of patients with lumbar spinal stenosis recruited from the practices of orthopedic surgeons and neurosurgeons throughout Maine.
To assess 1-year outcomes of patients with lumbar spinal stenosis treated surgically or nonsurgically.
No randomized trials and few nonexperimental studies have compared surgical and nonsurgical treatment of patients with lumbar spinal stenosis. The authors' goal was to assess 1-year outcomes of patients with lumbar spinal stenosis treated surgically or nonsurgically.
Eligible, consenting patients participated in baseline interviews and were then mailed follow-up questionnaires at 3, 6, and 12 months. Clinical data were obtained from a physician questionnaire. Outcomes included patient-reported symptoms of leg and back pain, functional status, disability, and satisfaction with care.
One hundred forty-eight patients with lumbar spinal stenosis were enrolled, of whom 81 were treated surgically and 67 treated nonsurgically. On average, patients in the surgical group had more severe imaging findings and symptoms and worse functional status than patients in the nonsurgical group at entry. Few patients with mild symptoms were treated surgically, and few patients with severe symptoms were treated nonsurgically. However, of the patients with moderate symptoms, a similar percent were treated surgically or nonsurgically. One year after study entry, 28% of nonsurgically and 55% of surgically treated patients reported definite improvement in their predominant symptoms (P = 0.003). For patients with moderate symptoms, outcomes for surgically treated patients were also improved compared with those of nonsurgically treated patients. Surgical treatment remained a significant determinant of 1-year outcome, even after adjustment for differences between treatment groups at entry (P = 0.05). The maximal benefit of surgery was observed by the time of the first follow-up evaluation, which was at 3 months. Although few nonsurgically treated patients experienced a worsening of their condition, there was little improvement in symptoms and functional status compared with study entry.
At a 1-year evaluation of patient-reported outcomes, patients with severe lumbar spinal stenosis who were treated surgically had greater improvement than patients treated nonsurgically. Comparisons of outcomes by treatment received must be made cautiously because of differences in baseline characteristics. A determination of whether the outcomes observed persist requires long-term follow-up.
A cadaveric study was done to analyze the dimensional changes in the spinal canal and intervertebral foramen of the lumber spine with flexion and extension movements.
To investigate the relationship between flexion and extension movements and morphologic changes in the spinal canal and the intervertebral foramen.
Previous studies have reported that the dimensions of the spinal canal and the intervertebral foramen may change significantly with motion. The purpose of this study was to assess the quantitative changes in the spinal canal and the intervertebral foramen with segmental flexion-extension movements.
Nineteen fresh cadaveric spines yielding 25 motion segments were used. The lumbar motion segments were frozen and then imaged in axial and sagittal projections by a computed tomography scanner. They were thawed then, and the motion segments were loaded to 5.7 Nm in flexion (13 motion segments) and in extension (12 motion segments) specimens. While in flexion or extension, the specimens again were frozen and imaged by computed tomography scan. The frozen specimens than were sliced using a cryomicrotome in the sagittal plane to study the dimensions of the intervertebral foramen. Eighteen other fresh cadaveric spines were sliced sagittally for study in the neutral position.
The axial computed tomography scans showed that extension significantly decreased the canal area, midsagittal diameter, and subarticular sagittal diameter, whereas flexion had the opposite effects. The sagittal computed tomography scans showed that extension decreased all the foraminal dimensions significantly, whereas flexion increased all the foraminal dimensions significantly. The translational changes were associated with the bulging of the disc and the presence of traction spurs. The cryomicrotome sections showed the cross-sectional area of the foramen to be 12% greater for the flexion group and 15% smaller for the extension group than the cross-sectional area of the neutral group. Nerve root compression in the foramen was found to be 21.0% in neutral, 15.4% in flexion, and 33.3% in extension groups.
The study supports the concept of dynamic spinal stenosis. In addition to static anatomic changes, careful dynamic studies may be required to evaluate better the central canal and the foramen.
A novel soft implant design for resisting the instability of the lumbar spine in the sagittal plane was mechanically tested.
To ascertain whether a soft preformed implant made of differing grades of silicone would contribute to stabilizing the lumbar spine in the sagittal plane.
Methods of stabilizing the lumbar spine in patients who present with chronic low back pain have usually concentrated on rigidly fixing the associated segment. This has many inherent problems with both the surgical methods and the long-term rigidity at and away from the stabilized site. To the authors knowledge, no "soft" interspinous spacer that would allow a certain amount of flexion but still stabilize the movements associated with instability at the level of the lesion has been investigated mechanically as an alternative to rigid fixation or prosthetic replacement.
The apparatus was designed to allow a cadaveric lumbar motion segment to be tested in compression at four angles of flexion with loads up to 700 N. The intradiscal pressure and sagittal plane stiffness were recorded during loading, with and without various sizes of the soft silicone implants placed between the spinous processes.
Insertion of the silicone implants between the spinous processes reduced the intradiscal pressure under load at the angles of flexion tested. The size of the interspinous space determines the optimal diameter of the implant that afforded sagittal stability, the load-bearing contribution of the implant, and the prevention of disc space narrowing at the level investigated.
A circular silicone spacer placed between the spinous processes appears to contribute to the stability of the cadaveric lumbar spine. There are many attractions to using a simple, soft implant that can be placed with minimal surgery between the spinous processes.
In patients with sciatica or neurogenic claudication, the structures in and adjacent to the lumbar spinal canal were observed by computed tomographic myelography or magnetic resonance imaging in psoas-relaxed position and during axial compression in slight extension of the lumbar spine.
To determine the mechanical effects on the lumbar spinal canal in a simulated upright position.
For years, functional myelographic investigation techniques were shown to be of value in the evaluation of suspected encroachment of the spinal canal. Since the advent of computed tomography and magnetic resonance imaging, there have been few clinical and experimental attempts that have imitated these techniques. The data indicate that the space within the canal is posture dependent.
Portable devices for axial loading of the lumbar spine in computed tomographic and magnetic resonance examinations were developed. Fifty patients (94 sites) were studied with computed tomographic myelography, and 34 patients (80 sites) with magnetic resonance in psoas-relaxed position followed by axial compression in slight extension. The dural sac cross-sectional area at L2 to S1, the deformation of the dural sac and the nerve roots, and the changes of the tissues surrounding the canal were observed.
In 66 of the investigated 84 patients, there was a statistically significant reduction of the dural sac cross-sectional area in at least one site during axial compression in slight extension. Of the investigated patients, 29 passed the borderlines for relative (100 mm2) or absolute stenosis (75 mm2) in 40 sites. In 30 patients, there was deformation of the dural sac in 46 sites. In 11 of the patients investigated with magnetic resonance imaging, there was a narrowing of the lateral recess in 13 sites, during axial compression in slight extension.
Axial loading of the lumbar spine in computed tomographic scanning and magnetic resonance imaging is recommended in patients with sciatica or neurogenic claudication when the dural sac cross-sectional area at any disc location is below 130 mm2 in conventional psoas-relaxed position and when there is a suspected narrowing of the dural sac or the nerve roots, especially in the ventrolateral part of the spinal canal in psoas-relaxed position. The diagnostic specificity of the spinal stenosis will increase considerably when the patient is subjected to an axial load.
A cohort of 100 patients with symptomatic lumbar spinal stenosis, characterized in a previous article, were given surgical or conservative treatment and followed for 10 years.
To identify the short- and long-term results after surgical and conservative treatment, and to determine whether clinical or radiologic predictors for the treatment result can be defined.
Surgical decompression has been considered the rational treatment. However, clinical experience indicates that many patients do well with conservative treatment.
In this study, 19 patients with severe symptoms were selected for surgical treatment and 50 patients with moderate symptoms for conservative treatment, whereas 31 patients were randomized between the conservative (n = 18) and surgical (n = 13) treatment groups. Pain was decisive for the choice of treatment group. All patients were observed for 10 years by clinical evaluation and questionnaires. The results, evaluated by patient and physician, were rated as excellent, fair, unchanged, or worse.
After a period of 3 months, relief of pain had occurred in most patients. Some had relief earlier, whereas for others it took 1 year. After a period of 4 years, excellent or fair results were found in half of the patients selected for conservative treatment, and in four fifths of the patients selected for surgery. Patients with an unsatisfactory result from conservative treatment were offered delayed surgery after 3 to 27 months (median, 3.5 months). The treatment result of delayed surgery was essentially similar to that of the initial group. The treatment result for the patients randomized for surgical treatment was considerably better than for the patients randomized for conservative treatment. Clinically significant deterioration of symptoms during the final 6 years of the follow-up period was not observed. Patients with multilevel afflictions, surgically treated or not, did not have a poorer outcome than those with single-level afflictions. Clinical or radiologic predictors for the final outcome were not found. There were no dropouts, except for 14 deaths.
The outcome was most favorable for surgical treatment. However, an initial conservative approach seems advisable for many patients because those with an unsatisfactory result can be treated surgically later with a good outcome.
To define the possible mechanism of posture-dependent symptoms of spinal stenosis by measuring the effect of low back posture on morphologic changes of the intervertebral discs and spinal canal in healthy young people.
Twenty healthy young volunteers underwent magnetic resonance imaging while supine with their spine in neutral, flexed, extended, and right and left rotational positions. The axial MR images at the middle of the intervertebral discs of L3-4 and L4-5 were analyzed to measure the difference in the size and shape of the intervertebral discs and spinal canal in each posture.
Extension or rotation decreased the sagittal diameters and cross-sectional areas of the dural sac and spinal canal and increased the thickness of the ligamentum flavum, whereas flexion had the opposite effects. The gap between the convex posterior disc margin and the anterior margin of the facet joint on each side, represented as the subarticular sagittal diameter, increased with flexion and decreased with extension or rotation. The direction of rotation did not result in asymmetry of the subarticular sagittal diameter, but right rotation caused thickening of the right ligamentum flavum, and vice versa. The shape and dimensions of the disc did not change significantly according to the positions of the low back.
With extension or rotation, the thickness of the ligamentum flavum increased and the posterior margin of the intervertebral disc was approximated to the facet joint without any change in shape and size of the disc. These phenomena result in a decrease in the size of the spinal canal and dural sac in extension or rotation postures in young healthy people without disc degeneration, and may explain the posture-dependent symptom of spinal stenosis.
A biomechanical and anatomic study with human cadaveric lumbar spine.
The purpose of this study is to examine the morphologic changes in the intervertebral foramen during flexion, extension, lateral bending, and axial rotation of the lumbar spine and to correlate these changes with the flexibility of the spinal motion segments.
Previous studies showed morphologic changes in the intervertebral foramen during flexion and extension; however, those changes during lateral bending and axial rotation were not well known.
There were 81 motion segments obtained from 39 human cadaveric lumbar spines (mean age 69 years). The motion segments were imaged with CT scanner with 1-mm thick consecutive sections. For biomechanical testing each motion segment was applied with incremental pure moments of flexion, extension, lateral bending, and axial rotation. Rotational movements of the motion segment were measured using VICON cameras. After application of the last load, the specimens were frozen under load, and then CT was performed with the same technique described above. Six parameters of the intervertebral foramen were measured, including foraminal width (maximum and minimum), foraminal height, disc bulging, thickness of ligamentum flavum, and cross-sectional area of the foramen.
Flexion increased the foraminal width (maximum and minimum), height, and area significantly while significantly decreasing the disc bulging and thickness of ligamentum flavum (P < 0.05). However, extension decreased the foraminal width (maximum and minimum), height, and area significantly. Lateral bending significantly decreased the foraminal width (maximum and minimum), height, and area at the bending side, whereas lateral bending significantly increased the foraminal width (minimum), height, and area at the opposite side of bending. Likewise, axial rotation decreased the foraminal width (minimum) and area at the rotation side significantly while significantly increasing the foraminal height and foraminal area at the opposite side. The percent change in the foraminal area was found significantly correlated with the amount of segmental spinal motion except for the extension motion.
This study showed that the intervertebral foramen of the lumbar spine changed significantly not only on flexion-extension but also on lateral bending and axial rotation. The percent change in cross-sectional foraminal area was correlated with the amount of segmental motion except for extension motions. Further studies are needed to assess the morphologic changes in the intervertebral foramen in vivo and to correlate clinically.
A first-generation implant for non-rigid stabilization of lumbar segments was developed in 1986. It included a titanium interspinous blocker and an artificial ligament made of dacron. Following an initial observational study in 1988 and a prospective controlled study from 1988 to 1993, more than 300 patients have been treated for degenerative lesions with this type of implant with clinical and mechanical follow-up. After careful analysis of the points that could be improved, a second-generation implant called the "Wallis" implant, was developed. This interspinous blocker, which was made of metal in the preliminary version, is made of PEEK (polyetheretherketone) in the new model. The overall implant constitutes a "floating" system, with no permanent fixation in the vertebral bone, to avoid the risk of loosening. It achieves an increase in the rigidity of destabilized segments beyond normal values. The clinical trials of the first-generation implant provided evidence that the interspinous system of non-rigid stabilization is efficacious against low-back pain due to degenerative instability and free of serious complications. The first-generation devices achieved marked, significant resolution of residual low-back pain. These results warrant confirmation. A randomized clinical trial and an observational study of the new implant are currently underway. Non-rigid fixation clearly appears to be a useful technique in the management of initial forms of degenerative intervertebral lumbar disc disease. This method should rapidly assume a specific role along with total disc prostheses in the new step-wise surgical strategy to obviate definitive fusion of degenerative intervertebral segments. At present, the Wallis system is recommended for lumbar disc disease in the following indications: (i) discectomy for massive herniated disc leading to substantial loss of disc material, (ii) a second discectomy for recurrence of herniated disc, (iii) discectomy for herniation of a transitional disc with sacralization of L5, (iv) degenerative disc disease at a level adjacent to a previous fusion, and (v) isolated Modic I lesion leading to chronic low-back pain.
1.A clinical condition is described in which there are symptoms of compression of the caudal nerve roots on standing or walking, but not at rest. Seven cases are reported.2.Myelography showed a block in the lumbar region in every case.3.At operation narrowing of the spinal canal in part of its lumbar course was found.4.The nature of the abnormality is discussed. It is suggested that the narrowing is due to encroachment on the spinal canal by the articular processes. Reproduced with permission and copyright © of the British Editorial Society of Bone and Joint Surgery: Verbiest H. A radicular syndrome from developmental narrowing of the lumbar vertebral canal. J Bone Joint Surg Br.1954;36-B:230-237.
Measurement of the kinematics of the lumbar spine after insertion of an interspinous spacer in vitro.
To understand the kinematics of the instrumented and adjacent levels due to the insertion of this interspinous implant.
An interspinous spacer (X Stop, SFMT, Concord, California) has been developed to treat neurogenic intermittent claudication by placing the stenotic segment in slight flexion and preventing extension. This restriction of motion by the interspinous implant may affect the kinematics of levels adjacent to the instrumented level.
Seven lumbar spines (L2-L5) were tested in flexion-extension, lateral bending, and axial rotation. Images were taken during each test to determine the kinematics of each motion segment. The interspinous implant was placed at the L3-L4 level, and the test protocol was repeated.
The flexion-extension range of motion was significantly reduced at the instrumented level. Axial rotation and lateral bending ranges of motion were not affected at the instrumented level. The range of motion in flexion-extension, axial rotation, and lateral bending at the adjacent segments was not significantly affected by the implant.
The implant does not significantly alter the kinematics of the motion segments adjacent to the instrumented level.
Intermittent claudication of the cauda equina
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Neurogenic and vascular claudication Kirkaldy-Willis WH, Wedge JH, Yong-Hing K, et al. Pathology and pathogenesis of lumbar spondylosis and stenosis
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Posture-dependentbilateralcompressionofL4orL5 nerve roots in facet hypertrophy. A dynamic CT-myelographic study
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Neurogenic Intermittent Claudication: With Special Reference to Stenosis of the Lumbar Vertebral Canal
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Verbiest H. Neurogenic Intermittent Claudication: With Special Reference
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The interspinous 'U': A new stabilization device for the lumbar spine Spinal Restabilization Procedures: Diagnostic and Therapeutic Aspects of Intervertebral Fusion Cages, Artifical Discs, and Mobile Implants
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Kaech D, Fernandez C, Lombardi-Weber D. The interspinous 'U': A new
stabilization device for the lumbar spine. In Kaech D, Jinkins J, eds. Spinal
Restabilization Procedures: Diagnostic and Therapeutic Aspects of Intervertebral Fusion Cages, Artifical Discs, and Mobile Implants.1st ed. Boston,
MA: Elsevier Science, 2002:xiii, 390.