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Interspinous Process Spacers
Abstract
The patient with neurogenic claudication resulting from lumbar spinal stenosis who fails to experience satisfactory relief from nonsurgical measures has limited treatment options. Lumbar epidural steroid injections and surgical laminectomy are generally accepted alternatives for the patient with moderate to severe symptoms. Interspinous process spacers, a relatively new class of technology, are proposed for use in the patient who prefers less invasive surgery or in whom medical comorbidities preclude a major surgical procedure. Early data from biomechanical and clinical studies support the short-term efficacy of interspinous process spacers in treating claudication related to spinal stenosis. Sufficient medium- and long-term data are lacking, however, particularly with respect to durability of symptomatic relief and the risk of device migration or dislocation. Although interspinous process spacers are a promising new technology, the results of longer-term clinical follow-up studies are needed to more clearly define their role in the management of lumbar spinal stenosis.
... 8 Interspinous spacers (IS) are implants that were proposed as a less invasive alternative to the surgical approaches, providing dynamic spinal stabilization with less risk of adjacent segment degeneration. 9,10,11 IS is eligible for all patients with symptoms due to LSS, patients with lower back pain with or without radicular involvement. 9,10,11 Some authors consider as an essential condition the failure of all conservative therapies for a considerable period: usually six months is accepted in literature. ...
... 9,10,11 IS is eligible for all patients with symptoms due to LSS, patients with lower back pain with or without radicular involvement. 9,10,11 Some authors consider as an essential condition the failure of all conservative therapies for a considerable period: usually six months is accepted in literature. 9,10,11 The presence of permanent motor deficit or degenerative spondylolisthesis are exclusion criteria. ...
... 9,10,11 Some authors consider as an essential condition the failure of all conservative therapies for a considerable period: usually six months is accepted in literature. 9,10,11 The presence of permanent motor deficit or degenerative spondylolisthesis are exclusion criteria. 9,10,11 In this study, we report multicentric data from patients implanted with Falena Õ and Aperius TM PerCLID TM IS during 1-year clinical follow-up. ...
Purpose:
Evaluation of the efficacy of the Falena® and Aperius™ PerCLID™ interspinous devices in the treatment of degenerative lumbar spinal stenosis with neurogenic intermittent claudication refractory to conservative treatment.
Materials and methods:
We retrospectively analyzed data from 24 patients (20 male and 4 female patients; 61 ± 7 years old), treated with an implantation of the AperiusTM PerCLID™ system, and from 35 patients (29 male and 6 female patients; 65 ± 9 years old) treated with the Falena® interspinous device.Patient pain intensity was evaluated by a 10-point visual analog scale (VAS), with a score (ranging from 0 = no pain to 10 = unbearable pain) that was collected before the procedure, at baseline; and at months 1, 6 and 12 after the interventional procedure. The assessment of quality of life (QOL) impairment was evaluated by the Oswestry Disability Index (ODI) questionnaire, which was administered beforehand at baseline; and at months 1, 6 and 12 after the interventional procedure. The vertebral canal area was measured by magnetic resonance imaging (MRI) scans before the treatment and at the one-year follow-up.
Results:
All patients completed the study with no complications. Both the Falena group and Aperius group of surgery patients showed a statistically significant reduction of their VAS and ODI scores at the 6- and 12-month follow-up (p < 0.0001). A statistically significant increase in the vertebral canal area was observed both in the group that received Falena (p < 0.0001) and in the group that received Aperius (p = 0.0003). At the 1-year follow-up, we observed that there was a higher increase of vertebral canal area in those patients whom were treated with the Falena device (p < 0.001).
Conclusions:
The implantation of Falena® and Aperius™ PerCLID™ interspinous devices is an effective and safe procedure, in the medium term.
... 20 IDD, requiring a minimally invasive procedure to insert, has, again, become an attractive option as the implant provides adequate stabilization of the respective pathologic vertebral segment while allowing adjacent segments to maintain their physiological range of movement. 1,21 In this study, a cadaveric lumbar spine model with L3-L4 instability was induced and the mechanical effect provided by the modified U-shape IDD was appraised. We confirmed the finding of Abumi et al 22 that a procedure involving a unilateral facetectomy and discectomy resulted in an increased motion of the respective spinal segment in all loading directions when compared with that of the intact specimen. ...
... 7,25 Other indications remain controversial due to the stability of the respective lumbar vertebrae created by the device. 1,2,8,21,28 Many experts recommend the use of this device as a mean of fixation in several clinical situations in which the stability of the lumbar segment may be of major concerns including patients with a large or recurrent discectomy, a degenerative disk disease adjacent to the fused level, and an isolated Modic type I disk lesion with chronic low back pain. 8,28 In contrast, segmental lumbar instability is considered to be a contraindication by others. ...
... 8,28 In contrast, segmental lumbar instability is considered to be a contraindication by others. 21 As our result shows that the modified Ushaped IDD restores the stability at destabilized lumbar vertebrae without disturbing the motion of adjacent segments, the indication of this modified U-shape IDD may extend to patients who suffer from the early stage of lumbar instability or disk problem and the modified Ushape IDD may delay the development of a more serious lumbar spinal pathology. 8,33 A cyclic loading test of the modified U-shape IDD is still required before a guideline for clinical use can be recommended. ...
Study design:
An experimental study.
Objective:
To analyze the effects of a modified U-shape interspinous distraction device (IDD) on the stability of a destabilized lumbar spine model.
Summary of background data:
The use of IDD for treatment of lumbar spine pathology remains a subject of debate. A modified design of an IDD consisted of a titanium (Ti) U-shape dynamic stabilizer and a Ti tensioning wire loop was biomechanically tested.
Materials and methods:
Six sets of cadaveric lumbar vertebrae levels 1-5 (L1-L5) were subjected to loads in flexion, extension, and lateral bending in the 4 following sequences: intact specimen, unilateral facetectomy and discectomy at L3-L4, insertion of the modified U-shape IDD at L3-L4, and pedicle screw fixation at L3-L4. The range of motion (ROM) of L3-L4 following modified U-shape IDD insertion was compared with that of the intact specimen. The ROM of the adjacent vertebrae (L2-L3 and L4-L5) following modified U-shape IDD insertion was compared with that after pedicle screw fixation. Statistical analysis was performed using the Wilcoxon signed-rank test.
Results:
The modified U-shape IDD decreased the ROM of a destabilized L3-L4 in all testing load (P<0.05). The stability of L3-L4 following the modified U-shape IDD insertion was restored to that of the intact specimen (P>0.05). The ROM at adjacent vertebrae after the modified U-shape IDD placement was similar to the ROM obtained after pedicle screw fixation at L3-L4.
Conclusions:
The modified version of a U-shape IDD is effective in stabilizing an unstable segment of the lumbar spine. The device does not create deleterious effects on the adjacent vertebrae.
... When conservative treatment is not effective, surgical decompression of nerve tissue with or without spinal fusion is usually indicated [6]. Recently, a procedure using an interspinous process spacer (IPS) has also been developed to maintain segmental flexion or prevent extension of the lumbar spine with relatively less invasion [2,9,17,18], and acceptable clinical outcomes for posture-dependent LSS using this method have been reported [10,13,17,19]. However, inserting IPS mostly requires open surgery including a relatively large skin incision as well as detaching muscle from bone. ...
... Additional problem of this technique is that the revision rate is relatively high. Follow up studies have revealed a 6-20% revision rate that has required decompressive surgery [2,9,10,13,19]. However when revision surgery for the implanted IPS is required, usually destructive procedures including cutting ligaments or bone are inevitable to remove it. Accordingly, if we need to replace the implant with one of a bigger or smaller size or remove it, a less invasive procedure is also desirable. ...
... Another approach has been to insert an IPS to maintain segmental flexion or prevent extension, thereby indirectly decompressing nerve tissues. The use of various IPSs has been reported with acceptable clinical outcomes [2,9,10,13,19]. However, most currently available IPSs require open surgery which includes detaching muscles from bone or cutting ligaments. ...
A procedure using an interspinous process spacer (IPS) was recently developed for the treatment of posture-dependent lumbar spinal-canal stenosis (LSS) patients. We developed a novel IPS which can be inserted with simpler procedures and removed percutaneously. The objectives of this study were: (1) to evaluate the feasibility and safety of this novel technique, and (2) to assess the effectiveness of this spacer in terms of preventing an increase of epidural pressure in lumbar extension using a porcine model.
Eight young pigs were used. Under general anesthesia and image guidance, the spacers were inserted. Three months after operation, MR images were taken and all spacers were removed. Blood samples were obtained before and 1, 3, 7 days after surgery. After killing the animals, the lumbar spines were observed macroscopically. Another six animals were used. Under general anesthesia and image guidance, a flexible pressure transducer was inserted into the epidural space and epidural pressure was measured in neutral and at maximum extension with and without spacer insertion.
Percutaneous insertion and removal of the spacer was successful for all animals through small skin incisions. MR images showed minimal damage to the muscle. No significant up-regulation of Interleukin-6 (IL-6) and CRP was detected. Macroscopic observation of the lumbar spine 3 months after the operation revealed that the area of the interspinous process contacting with the inserted spacer showed some bone erosion/remodeling. Insertion of the spacer did not affect the epidural pressure in neutral but significantly prevented an increase of epidural pressure in lumber extension.
This study demonstrated that the percutaneous insertion and removal of a novel IPS was feasible and safe using a simple technique. Furthermore, this procedure can be recognized as minimally invasive surgery from the viewpoint of skin incision, short insertion track, inflammatory mediators, and muscle damage. Improvements should be attempted in future studies using softer or more elastic materials for the spacer to lessen bone erosion/remodeling at contacting area of the inserted spacer.
... The surgical indications for lumbar interspinous process spacer in the United States of America are central and/or foraminal stenosis, neurogenic claudication, grade 1 degenerative spondylolisthesis, patients > 50 years [3]. In Europe, they also include: lateral recess stenosis, degenerative disc disease (DDD), facet syndrome, disc herniation, prevention and treatment for adjacent segment disease, DDD with reducible grade 1 retrolisthesis on the x-rays, kissing spine syndrome. ...
... In Europe, they also include: lateral recess stenosis, degenerative disc disease (DDD), facet syndrome, disc herniation, prevention and treatment for adjacent segment disease, DDD with reducible grade 1 retrolisthesis on the x-rays, kissing spine syndrome. Contraindications include: osteoporosis, listhesis grade 2 or greater, spondylolysis, fracture on the pars interarticularis or in the spinous process, ankylosis, infection, cauda equina, moderate to severe scoliosis [3][4][5][6]. ...
... 16,26,24,28,29,31,39 They can be categorized as static or dynamic, and material compositions include titanium, polyetheretherketone (PEEK), and elastomeric compounds. 1,13,15,17,25,27,31,35,36,45 Surgical indications have been extended, ranging from degenerative spinal stenosis, discogenic low-back pain, facet syndrome, disc herniations, and low-grade instability. These devices are used either as "stand-alone" implants or to augment open decompression by preventing instability. ...
... Over the past several years, IPDs have gained popularity for the treatment of degenerative lumbar diseases. 1,2,17,18,20,22,42 Recent clinical and radiological evidence has shown beneficial effects such as increased spinal canal and neural foramen dimensions with lowered intradiscal pressure at the level of the device and decreased pressure at the facets. 2,37 The surgical approach can be performed after inducing local spinal anesthesia with short procedures and hospitalizations. ...
OBJECT
Spacers placed between the lumbar spinous processes represent a promising surgical treatment alternative for a variety of spinal pathologies. They provide an unloading distractive force to the stenotic motion segment, restoring foraminal height, and have the potential to relieve symptoms of degenerative disc disease. The authors performed a retrospective, multicenter nonrandomized study consisting of 1108 patients to evaluate implant survival and failure modes after the implantation of 8 different interspinous process devices (IPDs).
METHODS
The medical records of patients who had undergone placement of an IPD were retrospectively evaluated, and demographic information, diagnosis, and preoperative pain levels were recorded. Preoperative and postoperative clinical assessments in the patients were based on the visual analog scale. A minimum of 3 years after IPD placement, information on long-term outcomes was obtained from additional follow-up or from patient medical and radiological records.
RESULTS
One thousand one hundred eight patients affected by symptomatic 1- or 2-level segmental lumbar spine degenerative disease underwent placement of an IPD. The complication rate was 7.8%. There were 27 fractures of the spinous process and 23 dura mater tears with CSF leakage. The ultimate failure rate requiring additional surgery was 9.6%. The reasons for revision, which always involved removal of the original implant, were acute worsening of low-back pain or lack of improvement (45 cases), recurrence of symptoms after an initial good outcome (42 cases), and implant dislocation (20 cases).
CONCLUSIONS
The IPD is not a substitute for a more invasive 3-column fusion procedure in cases of major instability and spondylolisthesis. Overdistraction, poor bone density, and poor patient selection may all be factors in the development of complications. Preoperatively, careful attention should be paid to bone density, appropriate implant size, and optimal patient selection.
... The decision to perform a microdiscectomy with or without dynamic spinal fusion in patients with a disc herniation is controversial [1][2][3]. Yet, the presence of low-back pain and degenerative disc disease can support the placement of an interspinous device (ISD) [4][5][6][7][8]. Although the insertion of dynamic devices has become a relatively common procedure for the treatment of lumbar stenosis and degenerative disc disease [9,10], its concomitant use with standard microdiscectomy is not clear given the lack of comparative studies [11][12][13][14]. ...
... Later, Taylor [18] developed a posterior interspinal dynamic stabilisation or balancing device. Since then, the use of soft dynamic techniques in lumbar spinal surgery has grown considerably [5,7,12,13], mainly for degenerative disc disease. ...
... The DIAM is an ISDD that acts as a dynamic stabilizer; it consists of an Xshaped silicone interspinous process bumper enveloped by a polyester fiber sack. 5 It is secured to the adjacent spinous processes by polyester implant tethers and fixed under tension. The DIAM has been promoted as a nonfusion alternative for managing a range of degenerative spinal conditions, including spinal stenosis, acute disc herniation, and degenerative disc disease. ...
... The DIAM has been promoted as a nonfusion alternative for managing a range of degenerative spinal conditions, including spinal stenosis, acute disc herniation, and degenerative disc disease. 5 By using the DIAM, the disc height can be restored, allowing more room at the foraminal level for nerve roots in the treatment of degenerative lumbar stenosis. The DIAM has also been known to unload the intervertebral disc, restore the posterior tension band, realign facet joints, and increase foraminal height, due to its insertion between the spinous processes ( Fig. 1). ...
Object:
The authors undertook this study to investigate the validity of the rationale for posterior dynamic stabilization using the Device for Intervertebral Assisted Motion (DIAM) in the treatment of degenerative lumbar stenosis.
Methods:
A cohort of 31 patients who underwent single-level decompression and DIAM placement for degenerative lumbar stenosis were followed up for at least 2 years and data pertaining to their cases were analyzed prospectively. Of these patients, 7 had retrolisthesis. Preoperative and postoperative plain lumbar radiographs obtained in all patients and CT images obtained in 14 patients were analyzed. Posterior disc heights; range of motion (ROM) of proximal, distal, and implant segments; lordotic angles of implant segments; percentage of retrolisthesis; and cross-sectional area and heights of intervertebral foramina on CT sagittal images were analyzed. Clinical outcomes were evaluated using visual analog scale scores and Oswestry Disability Index scores.
Results:
The mean values for posterior disc height before surgery, at 1 week after surgery, and at the final follow-up visits were 6.4 ± 2.0 mm, 9.7 ± 2.8 mm, and 6.8 ± 2.5 mm, respectively. The mean lordotic angles at the implant levels before surgery, at 1 week after surgery, and at the final follow-up visits were 7.1° ± 3.3°, 4.1° ± 2.7°, and 7.0° ± 3.7°, respectively. No statistically significant difference was found between the preoperative values and values from final follow-up visits for posterior disc height and lordotic angles at implant levels (p = 0.17 and p = 0.10, respectively). There was no statistically significant difference between the preoperative and final follow-up visit values for intervertebral foramen cross-sectional area and heights on CT images. The ROMs of proximal and distal segments also showed no significant decrease (p = 0.98 and p = 0.92, respectively). However, the ROMs of implant segments decreased significantly (p = 0.02). The average 31.4-month improvement for all clinical outcome measures was significant (p < 0.001).
Conclusions:
Based on radiological findings, the DIAM failed to show validity in terms of the rationale of indirect decompression, but it did restrict motion at the instrumented level without significant change in adjacent-segment ROM. The clinical condition of the patients, however, was improved, and improvement was maintained despite progressive loss of posterior disc height after surgery.
... However, fractures of spinous processes can occur during or after interspinous spacer implants, particularly in osteopenic patients [25]. Subsidence of the implant into the bone or dislocation may also be expected [26]. In the literature, several retrospective data on biomechanic, efficacy, and complications of Coflex implants are analysed and described. ...
... In the literature, several retrospective data on biomechanic, efficacy, and complications of Coflex implants are analysed and described. However, prospective studies concern only a small population, at this time [24,26272829. Heterotopic ossification is a widely investigated complication following total hip and knee arthroplasty3456789. ...
We present here a rare case of heterotopic ossification in interspinous/interlaminar Coflex device. The classical surgical indications for these implants are degenerative canal stenosis, discogenic low back pain, disk herniations, facet syndrome, and instability. However, fractures of spinous processes are a potential risk after interspinous/interlaminar devices' implantation. Recently, heterotopic ossification, a well-known complication of hip and knee arthroplasty, has been reported after cervical and lumbar prosthesis. We performed undercutting and implantation of the dynamic interspinous/interlaminar device to treat an adult male patient with L4-L5 stenosis. The patient underwent 45-day imaging and clinical followup, and we observed both a neurological and imaging improvement. A CT bone scan, performed 3 years after surgery for recurrence of neurogenic claudication, showed a new stenosis due to an abnormal ossification all over the device. To our knowledge, this is the first reported case of heterotopic ossification in an interspinous/interlaminar dynamic device. Accordingly, we aim to suggest it as a new complication of interspinous/interlaminar devices.
... Implantation of an interspinous spacer prevents motion at the implanted level41 and results in no progression of spondylolisthesis over time.33 Most studies of interspinous spacers allow enrolment of patients with grade I slip, and no compelling evidence exists to exclude these patients from treatment consideration.23,34 ...
... The X-STOP® Interspinous Process Decompression System (Medtronic, Inc, Minneapolis, MN) has been extensively studied in clinical trials,10–16 although reports with other spacers are less common.17–21 Despite overall favorable results with these devices in anatomically suitable patients, the clinical benefit of interspinous spacers is debatable given the paucity of available long-term data and the risk for device-related complications.22,23 This study was conducted to evaluate 2-year clinical outcomes in patients with moderate LSS who were treated with a novel, minimally invasive interspinous spacer. ...
To assess the safety and effectiveness of a novel, minimally invasive interspinous spacer in patients with moderate lumbar spinal stenosis (LSS).
A total of 53 patients (mean age, 70 ± 11 years; 45% female) with intermittent neurogenic claudication secondary to moderate LSS, confirmed on imaging studies, were treated with the Superion(®) Interspinous Spacer (VertiFlex, Inc, San Clemente, CA) and returned for follow-up visits at 6 weeks, 1 year, and 2 years. Study endpoints included axial and extremity pain severity with an 11-point numeric scale, Zurich Claudication Questionnaire (ZCQ), back function with the Oswestry Disability Index (ODI), health-related quality of life with the Physical Component Summary (PCS) and Mental Component Summary (MCS) scores from the SF-12, and adverse events.
Axial and extremity pain each decreased 54% (both P < 0.001) over the 2-year follow-up period. ZCQ symptom severity scores improved 43% (P < 0.001) and ZCQ physical function improved 44% (P < 0.001) from pre-treatment to 2 years post-treatment. A statistically significant 50% improvement (P < 0.001) also was noted in back function. PCS and MCS each improved 40% (both P < 0.001) from pre-treatment to 2 years. Clinical success rates at 2 years were 83%-89% for ZCQ subscores, 75% for ODI, 78% for PCS, and 80% for MCS. No device infection, implant breakage, migration, or pull-out was observed, although two (3.8%) patients underwent explant with subsequent laminectomy.
Moderate LSS can be effectively treated with a minimally invasive interspinous spacer. This device is appropriate for select patients who have failed nonoperative treatment measures for LSS and meet strict anatomical criteria.
... Such decompression operation frequently results in pain reduction in the legs and, to a lesser extent, in the low back [71].Even if pressure on nerve roots, dura, and blood vessels is properly relieved, the time and amount of recovery is uncertain. Laminectomy and hemilaminectomy, hemilaminotomy, fenestration, foraminotomy, and the implantation of interspinous distraction devices are all decompressive surgical treatments [72,73]. Decompression surgery has a complication rate of 14 percent (during and after the surgical treatment) 57 percent to 35 percent or more [74][75][76]. ...
The term lumbar spinal stenosis (LSS) refers to the narrowing of the spinal canal due to anatomical reasons, and it is linked to a variety of clinical symptoms.The onset of stenosis LSS can be unilateral or bilateral, monosegmental or multisegmental. The stenosis can be characterized as central, lateral, or foraminal anatomically.Neurogenic claudication is the most prevalent symptom of LSS, which is defined as limping or cramping lumbar pain that spreads into the legs primarily during walking.Typical patient symptoms include unilateral or bilateral (exertional) back and leg discomfort that develops over months, if not years.As people live longer and seek a better quality of life, as well as increased knowledge of the condition and the availability of improved imaging techniques, the number of people diagnosed with degenerative LSS has increased.
... It distracts the interspinous space and unloads the posterior annulus, resulting in indirect decompression without destabilizing or epidural scarring [2,6,17,18,26]. Despite these perceived advantages, complications include implant dislocation [4,24] and fractured spinous process (SP) [8,10]. If the implant is undersized, it may lead to implant migration and increased risk of SP fractures due to an oversized implant [27]. ...
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.
... Likewise, there is a compensatory buckling of the ligamentum flavum posteriorly and anterior bulge of the disc resulting in a decreased cross sectional canal diameter. 17 By interposing the device between adjacent spinous processes, the spinal segment is held in slight flexion without limitations on lateral bending or rotation. Computed tomography and magnetic resonance imaging studies have demonstrated an increase in cross-sectional spinal cord area by 11% to 22% with segmental flexion provided by an ID. ...
Study Design
Retrospective database study.
Objectives
Analysis of economic and demographic data concerning interspinous device (ID) placement throughout the United States to improve value-based care and health care utilization.
Methods
The National Inpatient Sample (NIS) database was queried for patients who underwent insertion of an interspinous process spinal stabilization device (ICD-9-CM 84.80) between 2008 and 2014 across 44 states. Demographic and economic data were obtained which included the annual number of surgeries, age, sex, insurance type, location, and frequency of routine discharge. The NIS database represents a 20% sample of discharges from US hospitals, which is weighted to provide national estimates.
Results
There was a 73% decrease in ID implanted from 2008 to 2014. The mean cost associated with insertion of the device increased 28% from $13 653 in 2008 to $17 515 in 2014. The mean length of stay (LOS) increased from 1.8 to 2.4 days. Patients aged 45 to 64 years increased from 14.1% to 34.3% while patients aged 65 to 84 years decreased from 74.4% to 60.6%. By region, 34% of ID placement occurred in the South followed by 19.7% that occured in the Northeast. When stratifying by median income for patient zip code, the procedure was performed more in cities designated as higher rather than lower income areas (74.2% and 19.5%, respectively).
Conclusions
Throughout the United States, there was a progressive decline in the insertion of interspinous spacers by 73% over the study period. The total costs for the procedure increased by 28% while the aggregate national charges decreased by 55.6% between 2008 and 2014.
... The DIAM is an interspinous distraction device that consists of an X-shaped silicone (dimethylsiloxane) interspinous process bumper enveloped by a polyethylene terephthalate (PET) fiber sack 8) . It acts as a dynamic stabilizer that preserves motion and provides segmental stabilization. ...
The device for intervertebral assisted motion (DIAM) is a dynamic implant that consists of a silicone bumper enveloped by a polyethylene terephthalate (PET) fiber sack. Silicone and PET were used because of their biological inertness, but repetitive motion of the spine can cause wear on the implant nonetheless. The purpose of this study is to report a case of foreign body reaction (FBR) against a DIAM. A 72-year-old female patient presented with lower back pain and both legs radiating pain. She had undergone DIAM implantation at L4–5 for spinal stenosis 5 years previously. The intervertebral disc space of L4–5, where the DIAM was inserted, had collapsed and degenerative scoliosis had developed due to left-side collapse. MRI showed L3–4 thecal sac compression and left L4–5 foraminal stenosis. The patient underwent removal of the DIAM and instrumented fusion from L3 to L5. During surgery, fluid and granulation tissue were evident around the DIAM. Histopathology showed scattered wear debris from the DIAM causing chronic inflammation due to the resulting FBR. A FBR due to wear debris of a DIAM can induce a hypersensitivity reaction and bone resorption around the implant, causing it to loosen.
... Estamos en una nueva era con una nueva visión para el problema del dolor bajo lumbar mecánico, «estabilizar pero no fusionar», los sistemas de estabilización dinámica influyen favorablemente en los movimientos y en las transmisiones de carga del segmento espinal móvil sin la intención de fusionar el segmento. 1,44,45 Consideramos que la técnica de estabilización facetaria tipo Mc Bride bajo el principio de la distracción interlaminar, es útil para el tratamiento de la enfermedad degenerativa discal, inestabilidad segmentaria, estenosis lumbar, considerando ahora que se ha incrementado la demanda por un sistema ideal de estabilización como una opción de trata- La estenosis lumbar e inestabilidad degenerativa puede ser manejada satisfactoriamente con la técnica de Mc Bride por las ventajas del principio de distracción interlaminar con la cual se restituye la subluxación facetaria, disminuye la presión intraforaminal, restituye la altura intersegmentaria, además de la ventaja mecánica del injerto circular que da un soporte inmediato, una estabilización y posteriormente una buena fusión. El injerto circular es perfecto, la compactación del injerto entre la faceta y la lámina es efectiva y directa en la circunferencia del bloque óseo, la firmeza de la impactación provee aproximación exacta en los bordes esponjosos de injerto y receptor, la revascularización es favorecida por la similitud de hueso cortico-esponjoso del receptor cuando es utilizado el proceso espinoso o de cresta ilíaca. ...
RESUMEN. Se realiza una evaluación y análi-sis de los resultados de descompresión lumbosacra y estabilización facetaria con técnica de Mc Bride para el tratamiento de la enfermedad lumbar de-generativa con inestabilidad en 340 pacientes (180 hombres y 160 mujeres) que fueron tratados du-rante el período de Mayo de 1996 a Mayo del 2003. El promedio de edad al momento de la ope-ración fue de 47 años (rango de 22 a 85 años) con rango de seguimiento de 3 a 8 años. Todos cum-plieron los criterios clínicos y de gabinete para lumbalgia crónica secundaria a enfermedad lum-bar degenerativa e inestabilidad segmentaria que no remitieron su sintomatología con tratamiento conservador. Se obtuvieron muy buenos resulta-dos en 114 pacientes (33.6%), buenos resultados en 203 pacientes (59.7%), regulares resultados en 16 pacientes (4.7%), pobres y malos resultados en 7 pacientes (2%). La técnica de Mc Bride permite si-multáneamente manejar la enfermedad degenera-tiva discal, la estenosis lumbar, la inestabilidad segmentaria y la artrodesis del segmento inestable mediante el principio de la distracción interlami-nar disminuyendo la compresión del foramen manteniendo una postura de extensión corrigien-do la subluxación articular y eliminando el punto estratégico de la movilidad facetaria interverte-bral, colocando un bloque óseo circular a contra-presión exacta dando un soporte y estabilización inmediata y una buena fusión. Palabras clave: fusión, columna, dolor, vérte-bra lumbar, técnica. ABSTRACT. We carried out a retrospective study of the clinical results of lumbosacral decom-pression with Mc Bride technique, in treatment of degenerative unstable lumbar stenosis. Three hun-dred and forty patients (180 male) were treated during May 1996 to May 2003. Mean age at sur-gery was 47 years old (22-85) with 3 to 8 years of follow up. All patients fulfilled clinical and image criteria for chronic lumbar pain due to degenera-tive lumbar stenosis and segmental instability that did not improve with conservative treatment. Re-sults: We found very good results in 114 patients (33.5%), good in 203 patients (59.7%) , regular in 16 patients (4.7%), and poor in 6 patients (2%). The Mc Bride technique is based in interlaminar distraction and permits managing lumbar stenosis and arthrodesis of an unstable segment simulta-neously. It diminishes compression in the foramen, maintains a position in extension, reduces facet joints subluxation and eliminates the strategic point of intervertebral mobility in facet joints. It allows immediate stabilization and later fusion by placing a bone block.
... Four-year results were obtained for the longest followed of these implants [5] and demonstrated an improved quality of life versus non-operative management [3]. The results of longer term follow-up studies are needed [4]. Basic science has provided some insights into the treatment mechanism of these implants. ...
The purpose of this study is to quantify the interspinous anatomy at the L4/5 and L5/S1 levels.
One hundred reconstructed computer tomography scans of the lumbosacral spine were reviewed by two separate surgeons. Data were collected from the midline sagittal reconstructed image at the L4-5 and L5-S1 levels. Measurements obtained included the disc angle, anterior and posterior disc height, and maximum interspinous space in both the anterior-posterior and cephalad-caudal directions. The disc height and disc angle were correlated with the interspinous height.
The mean age of the patients reviewed was 47 years (range: 16-91; standard deviation: 20). According to our data population, the average length of the interspinous space was larger at the L4-5 level (13 mm) than the L5-S1 level (9 mm). The interspinous height was similar between the two levels. A poor correlation existed between the disc height or disc angle and the interspinous height. There was no correlation between measurements and age.
The interspinous space available, as defined by computer tomography, at the L5/S1 level, is less able to accommodate current interspinous devices compared to the adjacent L4/5 level. The limiting factor is the length of the sacral part of the L5-S1 interspinous space.
... Third, longer term follow-up is required to definitively understand the safety and efficacy profile of this device. For example, theoretical concerns related to long-term device failure, device Device Profile Loguidice, Bini, Shabat, Miller & Block migration/dislocation, and erosion into the spinous process have been raised [22,23]. Finally, interspinous spacers may not be appropriate for patients with severe LSS and, therefore, laminectomy or similar decompressive procedures should be considered. ...
Lumbar spinal stenosis is a progressive degenerative condition that manifests as low back pain with neurogenic claudication as a cardinal clinical feature. Although mild radicular symptoms can often be successfully treated with conservative care, management of lumbar spinal stenosis grows increasingly difficult as symptoms worsen. No satisfactory nonsurgical treatments exist to manage moderate radicular symptoms and, therefore, these patients are faced with the decision of continuing ineffective conservative options or opting to undergo invasive decompressive spine surgery. The Superion(®) Interspinous Spacer (Vertiflex, Inc., CA, USA) was developed specifically to fill the therapeutic void between conservative care and surgical decompression. The Superion device is a titanium implant that is delivered percutaneously and deployed between the spinous processes at the symptomatic vertebral levels. The Superion device improves radicular symptoms by limiting spinal extension and, consequently, minimizing impingement of neural and vascular elements. This article describes the rationale for and the design of the Superion device and summarizes initial clinical results with this novel, minimally invasive interspinous spacer.
... Although lumbar spinal stenosis is one of the most common reasons for spinal intervention 8 , its clinical and radiological signs leading to an indication for surgery have not been clearly defined 9 implantation of interspinous distraction devices. The complication rates for decompression surgery (intra and postoperation) range from 14% to 35% or higher 11,12 . Fusion surgery, which is a more invasive procedure than decompression surgery, is associated with higher complication rates. ...
This study is a prospective, clinical study assessing the efficacy of selective decompression of the level responsible in a two-level stenosis in accordance with the neurological findings defined by the gait load test with a treadmill.
To clarify the clinical features of multilevel lumbar spinal stenosis (LSS) regarding the neurological level responsible for the symptoms, neurogenic claudication, and outcomes of selective decompression.
Most spine surgeons have reported that multilevel compression of the cauda equina induces a more severe impairment of the nerve function than a single-level compression. However, the clinical effects of multilevel LSS on the cauda equine and nerve roots are unknown.
A total of 21 patients with lumbar spinal canal stenosis due to spondylosis and degenerative spondylolisthesis were selected. The level responsible for the symptoms in the two-level stenosis was determined from the neurological findings on the gait load test and functional diagnosis based on a selective nerve root block. All patients underwent a prospective, selective decompression at the level neurologically responsible only. The average follow-up period was 2.6 years (range, 1 to 6 years). The postsurgical outcome was defined using the Visual Analogue Scale (VAS) at the post-gait load test, 2 weeks after surgery, 3 months after surgery and at the last follow up.
Before surgery, the mean threshold distance and mean walking tolerance was 34.3 m and 113 m, respectively. All patients had neurogenic claudication and 19 of the patients had cauda equina syndrome, including hypesthesia in 11 cases, muscle weakness in 5 cases and radicular pain in 7 cases. Selective nerve blocks to determine the level responsible for the lumbosacral symptoms in 2 cases revealed a mean VAS score of 7.1, 2.61, 3.04, and 3.47 at the post-gait load test, 2 weeks after surgery, 3 months after surgery and at the last follow up, respectively. All subjects underwent surgery. After the operation, neurogenic claudication with or without cauda equna syndrome subsided in all patients.
The gait load test allows an objective and quantitative evaluation of the gait characteristics of patients with lumbar canal stenosis and is useful for determining the appropriate level for surgical treatment.
... Decompressive surgical procedures include laminectomy and hemilaminectomy, hemilamino tomy, fenestration, foraminotomy and the implantation of inter spinous distraction devices. 11,69,72,73 The complication rates for decompression surgery (during and after the surgical reviews procedure) range from 14% 57 to 35% or more. [74][75][76] Fusion surgery, which is a more invasive procedure than decom pression surgery and is used in cases of instability, is associated with higher complication rates. ...
Lumbar spinal stenosis (LSS) comprises narrowing of the spinal canal with subsequent neural compression, and is frequently associated with symptoms of neurogenic claudication. To establish a diagnosis of LSS, clinical history, physical examination results and radiological changes all need to be considered. Patients who exhibit mild to moderate symptoms of LSS should undergo multimodal conservative treatment, such as patient education, pain medication, delordosing physiotherapy and epidural injections. In patients with severe symptoms, surgery is indicated if conservative treatment proves ineffective after 3-6 months. Clinically relevant motor deficits or symptoms of cauda equina syndrome remain absolute indications for surgery. The first randomized, prospective studies have provided class I-II evidence that supports a more rapid and profound decline of LSS symptoms after decompressive surgery than with conservative therapy. In the absence of a valid paraclinical diagnostic marker, however, more evidence-based data are needed to identify those patients for whom the benefit of surgery would outweigh the risk of developing complications. In this Review, we briefly survey the underlying pathophysiology and clinical appearance of LSS, and explore the available diagnostic and therapeutic options, with particular emphasis on neuroradiological findings and outcome predictors.
... Our sample size represented a relatively small number of subjects and the study focused on a narrow age range. However, it is important to note that the age range in this study closely reflects the demographics of the population most commonly treated for symptomatic spinal stenosis [6]. Another limitation of our findings is that we have yet to test individuals with spinal stenosis or those who have undergone ISPD implantation. ...
The study design included an in vivo laboratory study. The objective of the study is to quantify the kinematics of the lumbar spinous processes in asymptomatic patients during un-restricted functional body movements with physiological weight bearing. Limited data has been reported on the motion patterns of the posterior spine elements. This information is necessary for the evaluation of traumatic injuries and degenerative changes in the posterior elements, as well as for improving the surgical treatment of spinal diseases using posterior procedures. Eight asymptomatic subjects with an age ranging from 50 to 60 years underwent MRI scans of their lumbar segments in a supine position and 3D models of L2-5 were constructed. Next, each subject was asked to stand and was positioned in the following sequence: standing, 45 degrees flexion, maximal extension, maximal left and right twisting, while two orthogonal fluoroscopic images were taken simultaneously at each of the positions. The MRI models were matched to the osseous outlines of the images from the two orthogonal views to quantify the position of the vertebrae in 3D at each position. The data revealed that interspinous process (ISP) distance decreased from L2 to L3 to L4 to L5 when measured in the supine position; with significantly higher values at L2-3 and L3-4 compared with L4-5. These differences were not seen with weight-bearing conditions. During the maximal extension, the ISP distance at the L2-3 motion segment was significantly reduced, but no significant changes were detected at L3-4 and L4-5. During flexion the ISP distances were not significantly different than those measured in the MRI position at all segments. Going from the left to right twist positions, the L4-5 segment had greater amounts of ISP rotation, while all segments had similar ranges of translation in the transverse plane. The interspinous process distances were dependent on body posture and vertebral level.
... Estamos en una nueva era con una nueva visión para el problema del dolor bajo lumbar mecánico, «estabilizar pero no fusionar», los sistemas de estabilización dinámica influyen favorablemente en los movimientos y en las transmisiones de carga del segmento espinal móvil sin la intención de fusionar el segmento. 1,44,45 Consideramos que la técnica de estabilización facetaria tipo Mc Bride bajo el principio de la distracción interlaminar, es útil para el tratamiento de la enfermedad degenerativa discal, inestabilidad segmentaria, estenosis lumbar, considerando ahora que se ha incrementado la demanda por un sistema ideal de estabilización como una opción de trata- La estenosis lumbar e inestabilidad degenerativa puede ser manejada satisfactoriamente con la técnica de Mc Bride por las ventajas del principio de distracción interlaminar con la cual se restituye la subluxación facetaria, disminuye la presión intraforaminal, restituye la altura intersegmentaria, además de la ventaja mecánica del injerto circular que da un soporte inmediato, una estabilización y posteriormente una buena fusión. El injerto circular es perfecto, la compactación del injerto entre la faceta y la lámina es efectiva y directa en la circunferencia del bloque óseo, la firmeza de la impactación provee aproximación exacta en los bordes esponjosos de injerto y receptor, la revascularización es favorecida por la similitud de hueso cortico-esponjoso del receptor cuando es utilizado el proceso espinoso o de cresta ilíaca. ...
Unlabelled:
We carried out a retrospective study of the clinical results of lumbosacral decompression with Mc Bride technique, in treatment of degenerative unstable lumbar stenosis. Three hundred and forty patients (180 male) were treated during May 1996 to May 2003. Mean age at surgery was 47 years old (22-85) with 3 to 8 years of follow up. All patients fulfilled clinical and image criteria for chronic lumbar pain due to degenerative lumbar stenosis and segmental instability that did not improve with conservative treatment.
Results:
We found very good results in 114 patients (33.5%), good in 203 patients (59.7%), regular in 16 patients (4.7%), and poor in 6 patients (2%). The Mc Bride technique is based in interlaminar distraction and permits managing lumbar stenosis and arthrodesis of an unstable segment simultaneously. It diminishes compression in the foramen, maintains a position in extension, reduces facet joints subluxation and eliminates the strategic point of intervertebral mobility in facet joints. It allows immediate stabilization and later fusion by placing a bone block.
INTRODUCTION
Interspinous process devices (IPDs) were developed as minimally invasive alternatives to open decompression surgery for spinal stenosis. However, given high treatment failure and reoperation rates, there has been minimal adoption by the spine surgeons. This study leveraged a national claims database to characterize national IPD usage patterns and postoperative outcomes following IPD implantation.
METHOD
Using the PearlDiver database, we identified all patients who underwent 1- or 2-level IPD implantation between 2010 and 2018. Univariate and multivariable logistic regression was performed to identify predictors of the number of IPD levels implanted and reoperation up to 3 years after index surgery. Right-censored Kaplan-Meier curves were plotted for duration of reoperation-free survival and compared with log-rank tests.
RESULTS
4,865 patients received 1-level (n = 3,246) or 2-level (n = 1,619) IPDs. Patients who were older (aOR 1.02, 95% CI 1.01–1.03, p < 0.001), male (aOR 1.31, 95% CI 116–1.50, p < 0.001), and obese (aOR 1.19, 95% CI 1.05–1.36, p < 0.01) were significantly more likely to receive a 2-level IPD versus a 1-level IPD. The 3-year reoperation rate was 9.3% of patients when accounting for mortality during the follow-up period. Older age decreased (aOR 0.97, 95% CI 0.97–0.99, p = 0.0039) likelihood of reoperation while 1-level IPD (aOR 1.37, 95% CI 1.01–1.89, p = 0.048), CCI (aOR 1.07, 95% CI 1.01–1.14, p = 0.018) and performing concomitant open decompression increased the likelihood of reoperation (aOR 1.68, 95% CI 1.35–2.09, p = 0.0014).
CONCLUSION
Compared to one-level IPDs, two-level IPDs were implanted more frequently in older, male, and obese patients. The 3-year reoperation rate was 9.3%. Concomitant open decompression with IPD placement was identified as a significant risk factor for subsequent reoperation and warrants future investigation.
Contemporary Endoscopic Spine Surgery brings the reader the most up-to-date information on the endoscopy of the spine. Key opinion leaders from around the world have come together to present the clinical evidence behind their competitive endoscopic spinal surgery protocols. Chapters in the series cover a range of aspects of spine surgery including spinal pain generators, preoperative workup with modern independent predictors of favorable clinical outcomes with endoscopy, anesthesia in an outpatient setting, management of complications, and a fresh look at technology advances in a historical context. The reader will have a first-row seat during the illustrative discussions of expanded surgical indications from herniated disc to more complex clinical problems, including stenosis, instability, and deformity in patients with advanced degenerative disease of the human spine. Contemporary Endoscopic Spine Surgery is divided into three volumes: Cervical Spine, Lumbar Spine, and Advanced Technologies to capture an accurate snapshot in time of this fast-moving field. It is intended as a comprehensive go-to reference text for surgeons in graduate residency and postgraduate fellowship training programs and for practicing spine surgeons interested in looking for the scientific foundation for expanding their clinical practice towards endoscopic surgery.
This volume (Advanced Technologies) covers the following endoscopic spine surgery topics in 19 detailed chapters: endoscopic intradiscal therapy and foraminoplasty, evidence based medicine in spine surgery, artificial intelligence for spine surgery, postoperative management, transforaminal lumbar endoscopy and associated complications, laser applications in full endoscopy of the spine, high frequency surgery for the treatment of herniated discs, lumbar MRI, cost and maintenance management of endoscopic spine systems, regenerative medicine, interbody fusion, endoscopic intravertebral canal decompression after spinal fracture, treatment of lumbar tuberculosis, treatment of degenerative scoliosis, treatment of thoracic meningioma with spinal canal decompression, and cervical endoscopic unilateral laminotomy for bilateral decompression (CE-ULBD).
Interspinous process spacers fill a significant gap in the treatment algorithm for lumbar spinal stenosis between conservative treatment options, such as physical therapy, injections, and medications, and, at the other end of the spectrum, surgical treatments (e.g., open laminectomy). There is strong clinical evidence that, for properly selected patients with neurogenic intermittent claudication secondary to moderate lumbar spinal stenosis, such spacers can provide significant relief of pain and reductions in physical disability. Interspinous process spacers can be implanted in a minimally invasive procedure, reducing the risk of complications.
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.
Interspinous spacers used stand-alone preserve joint movement but provide little protection for diseased segments of the spine. Used as adjuncts with fusion, interspinous spacers offer rigid stability but may accelerate degeneration on adjacent levels. Our new device is intended to balance the stability and preserves motion provided by the implant. A new interspinous spacer was devised according to the results of topology optimization studies. Four finite element (FE) spine models were created that consisted of an intact spine without an implant, implantation of the novel, the device for intervertebral assisted motion (DIAM system), and the Dynesys system. All models were loaded with moments, and their range of motions (ROMs), peak disc stresses, and facet contact forces were analyzed. The limited motion segment ROMs, shielded disc stresses, and unloaded facet contact forces of the new devices were greater than those of the DIAM and Dynesys system at L3-L4 in almost all directions of movements. The ROMs, disc stresses, and facet contact forces of the new devices at L2-L3 were slightly greater than those in the DIAM system, but much lower than those in the Dynesys system in most directions. This study demonstrated that the new device provided more stability at the instrumented level than the DIAM system did, especially in lateral rotation and the bending direction. The device caused fewer adjacent ROMs, lower disc stresses, and lower facet contact forces than the Dynesys system did. Additionally, this study conducted topology optimization to design the new device and created a smaller implant for minimal invasive surgery.
Background:
There has been increasing interest in using the lumbosacral spinous processes for fixation as a less invasive alternative to transpedicular instrumentation. Though prior studies have described the appearance and biomechanics of lumbar spinous processes, few have evaluated the dimensions, morphology, or strength of the sacral spinous processes.
Purpose:
Goals of this study were to characterize the morphology of the S1 spinous process and biomechanical strength of the S1 spinous process when loaded in a cranial direction.
Study design:
This study was performed as both an analysis of radiographic data and biomechanical testing of cadaveric specimens.
Methods:
Lumbosacral spine radiographs and CT scans of twenty patients were evaluated for visibility and morphology of the S1 spinous process. S1 spinous process length, height, and size of the L5-S1 segment were measured. Additionally, thirteen cadaveric lumbosacral spinal segments were obtained for biomechanical testing and morphologic analysis. Specimens were loaded at the S1 spinous process in a cranial direction via a strap, simulating resistance to a flexion moment applied across the L5-S1 segment. Peak load to failure, displacement, and mode of failure were recorded.
Results:
The S1 spinous process was clearly visible on lateral radiographs in only 10% of patients. Mean spinous process length (anterior-posterior) was 11.6mm while mean spinous process height (cranial-caudal) was 23.1mm. We identified six different morphologic subtypes of the S1 spinous process: Fin, Lumbar, Fenestrated, Fused, Tubercle, and Spina Bifida Occulta. During tension loading of the S1 spinous process in the cephalad direction, mean peak load to failure was 439N, with 92% of specimens failing by fracture through the spinous process.
Conclusions:
This is the first study evaluating sacral spinous process morphology, visibility, and biomechanical strength for potential instrumentation. Compared to lumbar spinous processes, sacral spinous processes are smaller with more variable morphology but have similar peak load to failure. For ideal visualization of morphology and suitability for interspinous fixation, preoperative three-dimensional imaging may be a valuable tool over plain radiographs.
Despite interest in lumbar spinous process-based surgical innovation, there are no large published studies that have characterized morphometry of lumbar spinous processes.
To provide accurate level-specific morphometric data with respect to human lumbar spinous processes using a human cadaveric lumbar spine model and to describe morphometric variation of lumbar spinous processes with respect to gender, race and age.
Anatomic observational METHODS: This study utilized 2,955 cadaveric lumbar vertebrae from 591 adult spines at the Hamann-Todd Human Osteological Collection. Specimens were ages 20-79 years. Each vertebra was photographed in standardized positions and measured using ImageJ software. Direct measurements were made for spinous process (SP) length, width, height, slope and caudal morphology. Gender, race and age were recorded and analyzed.
SP length was 24.8±4.6 mm (L5) to 33.9±3.9 mm (L3). Effective length varied from 19.5±2.6 mm (L1) to 24.6±3.3 mm (L4). Height was shortest at L5 (18.2±2.7 mm). Caudal width was greater than cranial width. Slope, caudal morphology and radius measures showed large inter-specimen variation. Slope at L5 was steeper than other levels (23.7±10.5 degrees, p<0.0001). Most specimens demonstrated convex caudal morphology. L4 had the highest proportion of convexity (80.7%). L1 was the only level with predominantly concave morphology. Measurements for female SPs were smaller, but slope was steeper. Anatomic and effective SP lengths were longer for specimens from white individuals. Specimens from black individuals had larger width and height, as well as steeper slope. Black specimens had more convex morphology at L4 and L5. With increasing age, SP length, effective length and width increased. Height increased with age only at L4 and L5. Slope and caudal radius of curvature decreased with age and increasingly convex morphology was noted at most levels.
This large cadaveric study provides level-specific morphometric data regarding the osseous dimensions of lumbar spinous processes relevant to techniques and devices targeting lumbar spinous processes or the interspinous space. Of particular importance is the recognition that L5 has relatively different morphology when compared to more cranial levels. Potentially important differences were noted comparing female to male, black to white and aging populations.
Copyright © 2015 Elsevier Inc. All rights reserved.
Purpose:
This prospective randomised control study is to demonstrate whether or not there is a clinical benefit from inserting a Wallis implant on the functional recovery of patients who have undergone lumbar decompression surgery.
Method:
Sixty consecutive patients with an average age of 58 years (34-81) who were selected for primary lumbosacral decompression were randomly assigned into two groups with equal number of patients, decompression alone or decompression with Wallis implant. The patients had an average follow-up of 40 months. Patients were assessed by visual analogue scale (VAS) (Boonstra et al., Int J Rehabil Res 31:165-169, 2008; Price et al., Pain 17:45-56, 1983) pain score for back and leg pain, and the Oswestry Disability Index questionnaire (ODI) (Smeets et al., Arthritis Care Res (Hoboken) 63:S158-S173, 2011).
Results:
The results in both the groups did not reveal a significant difference in the clinical outcome assessment of back pain score or ODI. With the Wilcoxon two-sample test, no difference in median values was achieved (p value 0.0787 for ODI and p value 0.1926 for back pain). The average ODI in the Wallis group dropped from 50.93 to 29.11. The average VAS for the Wallis group back pain dropped from 7.79 to 4.22.
Conclusion:
The Wallis implant is a safe medical device. This study revealed a reduction in pain and functional disability in patients treated with decompression surgery for lumbar stenosis, with or without Wallis. The Wallis group improved more, but it was not statistically significant. The risk of complications is lower than other interspinous devices.
Lumbar spinal stenosis continues to be an important cause of low back pain and neurogenic claudication. As the population ages and life expectancy increases, both the incidence and prevalence of spinal stenosis will present a significant challenge to spine surgeons. Both interspinous and interbody fusion techniques have demonstrated the ability to decrease low back pain and provide clinically significant pain relief from neurogenic claudication through indirect means. While direct decompression of the spine has been well documented in the literature and the gold standard, new interest in minimally invasive techniques and indirect decompression has led to new devices and clinical studies with promising results.
Zusammenfassung Das interspinöse DIAM™- („device for interspinous assisted motion“) Implantat ermöglicht mit einer kleinen, reversiblen Operation
eine viskoelastische Unterstützung des lumbalen Bewegungssegments. Es wurde 2004 in Deutschland eingeführt und soll nach einer
Bandscheibenoperation restabilisieren, die Überlastung des Facettengelenks vermeiden und das Nachbarsegment nach einer Fusion
mechanisch entlasten. Biomechanische Arbeiten weisen eine Wirkung in Extension und Flexion, kaum jedoch in Rotation und Seitneigung
nach. Obwohl häufig in der Klinik eingesetzt, gibt es nur eine vergleichsweise geringe Zahl an klinischen, hauptsächlich retrospektiven
Arbeiten, die den Erfolg des Implantats belegen. Sichere wissenschaftliche Daten fehlen bisher. Mehrere prospektive, randomisierte
und kontrollierte Studien werden zur Zeit durchgeführt, um diese Lücke zu schließen. Letztlich wird der Wert des Implantats
in der Behandlung der degenerativen Kaskade der Lendenwirbelsäule erst nach deren Fertigstellung zu beurteilen sein.
Neurogenic claudication secondary to lumbar spinal stenosis (LSS) generally responds to conservative measures, but individuals with persistent symptoms or significant functional disability often require surgical intervention. Interspinous spacers (ISSs) have been introduced as a novel method for reproducing the postural relief that these individuals typically experience with lumbar flexion, which may avoid much of the morbidity of other operative procedures, such as a laminectomy. By distracting the interspinous space, ISSs have been shown to increase the dimensions of the spinal canal and foramina, thereby bringing about an “indirect” decompression of the neural elements. There is only one implant currently approved by the Food and Drug Administration for the treatment of intermittent neurogenic claudication arising from 1 or 2 levels of LSSs confirmed by appropriate imaging studies. As part of the surgical technique, the patient must be maintained in maximum flexion to facilitate the safe placement of the implant, and care must be taken to adequately preserve the interspinous ligament. Multiple in vitro and clinical investigations have established the safety and efficacy of ISS, but these devices are known to be associated with a number of complications, including spinous process and neurologic sequelae. Although additional prospective clinical trials are necessary to establish the long-term durability and cost-effectiveness of ISS, this strategy remains a viable, less invasive option for the treatment of symptomatic LSS compared with posterior decompression.
Ein 77-jähriger Patient war wegen manifester neurogener Claudicatio spinalis bei bekannter lumbaler Spinalkanalstenose in 3 Segmenten an einer auswärtigen Institution mit perkutanen interspinösen Implantaten versorgt worden, wonach sich die klinische Symptomatik nicht änderte. Erst die mikrochirurgische Dekompression und die Entfernung der Platzhalter führten zu einer deutlichen Besserung der Beschwerden und Verlängerung der schmerzfreien Gehstrecke. Anhand dieses Falles wird die Verwendung von interspinösen Platzhaltern beleuchtet. In der bisherigen klinischen Anwendung fehlen noch die Langzeitergebnisse. Eine korrekte Indikationsstellung zur Intervention bei Spinalkanalstenose ist Voraussetzung für ein zufriedenstellendes postoperatives Ergebnis.
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One of the potential allures of nonrigid stabilization of the spine is the possibility that adjacent level disease could be
eliminated or reduced. We explore whether this prospect is myth or fact. For spinal fusion, it is generally recognized that
there is a definite risk of adjacent level degeneration. Ghiselli et al. have estimated that the rate of surgery for adjacent
level disease was 3.9% for the 10 years following a primary lumbar fusion. Thus, at 10 years, the survivorship analysis predicted
that 36.1% of lumbar fusion patients would have further operative intervention. Interestingly, their study also showed that
the risk of adjacent level degeneration was significantly less for a multiple level fusion compared to a single segment arthrodesis.
There is a limited amount of data available on the influence of pedicle screw-based stability/nonfusion technologies. Several
authors have addressed the influence of disk arthroplasty on adjacent levels. Cunningham [31] looked at the biomechanics of
TDA and found that the normal centrode of rotation was relatively maintained with TDA. In terms of motion, this would give
TDA a favorable mechanical profile compared to fusion regarding shifting mechanical stresses to adjacent levels. Chang [32]
performed disk pressure studies of adjacent levels in the cervical spine comparing TDA and fusion. Pressures were slightly
lower at adjacent levels compared to fusion, except in flexion where pressures were higher with ProDisc–C. Longer-term follow-up
is more available for lumbar TDA. David [34] has reported a 13.2-year follow-up of Charite. Lemaire [33] has an 8.7-year follow-up
of ProDisc. Rates of symptomatic ASD varied between 1.9 and 2.6% for fusion, adjacent level disease is certainly Fact. One
could argue this for lumbar TDA as well. For pedicle screw-based nonfusion technologies and cervical TDA, further time and
studies will be required to bring issues out of the realm of myth.
Spinous process fracture is a recognized complication associated with interspinous process spacer (IPS) surgery. Although occasionally identified by plain radiographs, computed tomography (CT) appears to identify a higher rate of such fractures. Although osteoporotic insufficiency fracture is considered a contraindication for IPS surgery, a formal risk factor analysis for this complication has not previously been reported.
To identify risk factor(s) associated with early spinous process fracture after IPS surgery.
Prospective cohort study of 39 consecutive patients with lumbar stenosis and neurogenic claudication undergoing IPS surgery at a single institution.
Patients underwent preoperative dual-energy X-ray absorptiometry (DXA) scans, lumbar spine CT, and plain radiographs. Postoperatively, patients underwent repeat CT imaging within 6 months of surgery and serial radiographs at 2 weeks, 6 weeks, 3 months, 6 months, and 1 year. Preoperative CT scans were analyzed by calculating average Hounsfield units for a 1 cm(2) area of the midsagittal reconstructed image for four separate locations: midvertebral body, subcortical bone subjacent to the superior margin of the midspinous process, subcortical bone above the inferior margin of the midspinous process, and the midspinous process.
Thirty-eight patients underwent IPS surgery at a total of 50 levels (38 L4-L5, 12 L3-L4; 26 one-level, 12 two-level). One patient underwent laminectomy at index surgery and was excluded from the analysis. Implants included 34 titanium X-STOP (Medtronic, Memphis, TN, USA), 8 polyaryletheretherketone X-STOP (Medtronic, Memphis, TN, USA), and 8 Aspen (Lanx, Broomfield, CO, USA) devices. Eleven spinous process fractures were identified by CT in 11 patients (22.0% of levels). No fractures were apparent on plain radiographs. The rate of spondylolisthesis observed on preoperative radiographs was 100% (11 of 11) among patients with fractures compared with 33.3% (9 of 27) of patients without fracture (p=.0001). Overall, 21 of 39 patients in this series had spondylolisthesis, and the rate of fracture in this group was 52%. Among patients without spondylolisthesis, the fracture rate was 0%. A trend was observed toward decreased DXA lumbar spine and hip T-scores among fracture patients versus nonfracture patients (0.2 ± 1.7 vs. 0.8 ± 1.7; p=.389; -1.1 ± 1.4 vs. -0.3 ± 1.4; p=.201), but these differences were not significant. Similarly, bone density based on CT measurements at four different locations revealed a trend toward decreased density among fracture patients, but these differences were not significant.
Degenerative spondylolisthesis appears strongly associated with the occurrence of spinous process fracture after IPS surgery. There is a trend toward increased fracture risk in patients with decreased bone mineral density as measured by both DXA scan and CT-based volume averaging of Hounsfield units, but osteoporosis appears to be a relatively weaker risk factor. The association between spondylolisthesis and fracture observed in this study may account for the relatively poorer outcome of IPS surgery in patients with spondylolisthesis that has been reported in previous series.
There has been increasing interest in spinous process tension band devices, as distinct from spinous process spacers and plates. The purpose of this study was to load spinous processes caudally at L-4 and cranially at L-5 parallel to the long axis of the spine in a biomechanical model of tension band loading. The goal was to provide normative data for the design of a spinous process tension band device after varying degrees of surgical decompression and across varying bone mineral densities (BMDs).
Fresh-frozen L4-5 lumbar vertebrae pairs were divided into 3 surgical groups: intact, midline-sparing decompression (laminotomy and medial facetectomy), and midline decompression with foraminotomy (one-half of spinous process resected, laminotomy, and medial facetectomy). After decompression, specimens were disarticulated into isolated L-4 and L-5 vertebrae. Each vertebra was loaded to failure in a caudal (L-4) or cranial (L-5) direction parallel to the long axis of the spine via a 6-mm-wide strap looped around the spinous process. Failure strength and mode were recorded.
Seventeen L-4 and L-5 lumbar vertebrae were tested from 17 cadavers. There were 10 male (59%) and 7 female (41%) cadavers, with a mean age of 66.6 ± 16.5 years (range 41-100 years) and a mean BMD of 1 ± 0.23 g/cm(2) (range 0.66-1.34 g/cm(2)); the mean is expressed ± SD throughout. For data analysis, specimens were grouped into those with no or midline-sparing decompression (Group 1: 11 of 17) and those with midline decompression (Group 2: 6 of 17). At L-4, the mean failure strength for Group 1 was 453 ± 162 N, and for Group 2 it was 264 ± 99 N (p = 0.02; Cohen's d = 1.4). At L-5, the mean failure strength for Group 1 was 517 ± 190 N, and for Group 2 it was 269 ± 184 N (p = 0.02; Cohen's d = 1.3). There was no significant difference in failure strength between the intact and midline-sparing decompression groups at L-4 (p = 0.91) or L-5 (p = 0.41).
Across specimens with a wide range of BMDs, midline-sparing decompression was not found to decrease the mean failure strength of the L-4 and L-5 spinous processes (453 and 517 N, respectively), whereas midline surgical decompression decreased the failure strength of these processes (264 and 269 N, respectively) in a biomechanical model of tension band loading relevant to the design of a tension band device.
The interspinous distraction devices are used to treat variable pathologies ranging from facet syndrome, diskogenic low back pain, degenerative spinal stenosis, diskopathy, spondylolisthesis, and instability. The insertion of a posterior element with an interspinous device (ISD) is commonly judged responsive to a relative kyphosis of a lumbar segment with a moderate but persistent increase of the spinal canal and of the foraminal width and area, and without influence on low-grade spondylolisthesis. The consequence is the need of shared specific biomechanical concepts to give for each degenerative problem the right indication through a critical analysis of all available experimental and clinical biomechanical data. We reviewed systematically the available clinical and experimental data about kyphosis, enlargement of the spinal canal, distraction of the interspinous distance, increase of the neural foramina, ligamentous structures, load of the posterior annulus, intradiskal pressure, strength of the spinous processes, degeneration of the adjacent segment, complications, and cost-effectiveness of the ISD. The existing literature does not provide actual scientific evidence over the superiority of the ISD strategy, but most of the experimental and clinical data show a challenging potential. These considerations are applicable with different types of ISD with only few differences between the different categories. Despite-or because of-the low invasiveness of the surgical implantation of the ISD, this technique promises to play a major role in the future degenerative lumbar microsurgery. The main indications for ISD remain lumbar spinal stenoses and painful facet arthroses. A clear documented contraindication is the presence of an anterolisthesis. Nevertheless, the existing literature does not provide evidence of superiority of outcome and cost-effectiveness of the ISD strategy over laminectomy or other surgical procedures. At this time, the devices should be used in clinical randomized independent trials in order to obtain more information concerning the most advantageous optimal indication or, in selected cases, to treat tailored indications.
Objective:
To analyze the interspinous distance and the height, length, and thickness of the lumbar spinous process for interspinous device implantation in Korean patients.
Methods:
Morphometric data obtained from plain radiographs of the lumbar and sacral spine were analyzed. The study included 60 matched subjects who visited an outpatient clinic for back pain. Exclusion criteria included collapsed intervertebral disc, lumbarization, and sacralization. There were 34 men and 26 women; age range was the 20s to 70s, with 10 subjects in each decade. The interspinous distance and height, length, and thickness of the lumbar spinous process were obtained on lateral radiographs using an image analysis program (M-view 5.4; Marotech).
Results:
The largest interspinous distance was at L2-3, with a mean of 12 mm (range 6-22 mm), and the smallest distance was at L5-S1, with a mean of 8 mm (range 3-16 mm). The interspinous distance became shorter from L1-2 to L5-S1. A negative correlation was noted between age and interspinous distance in the L1-5 levels (L1-2, y=-0.11x+17.27, r2=0.34, P<0.0001; L2-3, y=-0.07x+15.68, r2=0.12, P=0.0058; L3-4, y=-0.08x+14.39, r2=0.27, P<0.0001; L4-5, y=-0.05x+11.65,r2=0.096, P=0.0158; L5-S1, y=-0.02x+9.25, r2=0.028, P=0.1982).
Conclusions:
There is a decreasing trend in the interspinous distance in the L1-5 levels with advancing years. Taking progressive collapse of the interspinous distance with the aging process into consideration, interspinous implants should be carefully selected in younger patients.
This study was designed to evaluate the feasibility of the implantation of a new interspinous device (Falena) in patients with lumbar spinal stenosis. The clinical outcomes and imaging results were assessed by orthostatic MR during an up to 6-month follow-up period.
Between October 2008 and February 2010, the Falena was implanted at a single level in 26 patients (17 men; mean age, 69 (range, 54-82) years) who were affected by degenerative lumbar spinal stenosis. All of the patients were clinically evaluated before the procedure and at 1 and 3 months. Furthermore, 20 patients have completed a 6-month follow-up. Pain was assessed before and after the intervention using the Visual Analogue Scale score and the Oswestry Disability Index questionnaire. Orthostatic MR imaging was performed before the implantation and at 3 months to assess the correlation with the clinical outcome.
The mean ODI score decreased from 48.9 before the device implantation to 31.2 at 1 month (p < 0.0001). The mean VAS score decreased from 7.6 before to 3.9 (p < 0.0001) at 1 month and 3.6 at 3 months after the procedure (p = 0.0115). These values were stable at 6 months evaluation. No postimplantation major complications were recorded. MRI evaluation documented in most cases an increased size of the spinal canal area. Similarly a bilateral foraminal area improvement was found. The variation of the intervertebral space height measured on the posterior wall was not significant.
In our preliminary experience with the Falena in a small cohort of patients, we obtained clinical and imaging results aligned to those reported with similar interspinous devices.
Prospective observational study.
To provide a more accurate estimate of the rate of acute spinous process fractures associated with IPS surgery.
Biomechanical cadaveric studies have suggested adequate spinous process strength to support placement of interspinous process spacers (IPS). Postoperative spinous process fractures have been reported in one%-to 5.8% of patients in previous series based on routine biplanar radiographic evaluation. However, most fractures occur between the base and midportion of the spinous process in an area that is typically difficult to visualize on plain radiographs due to device design.
All patients underwent preoperative biplanar plain radiographs and computed tomography (CT) of the lumbar spine to confirm anatomy favorable for IPS placement and rule out fracture or spondylolysis. Postoperatively, all patients underwent repeat CT imaging within six months of surgery, biplanar radiographs at two weeks, six weeks, three months, six months, and one year. All studies were reviewed independently by a neuroradiologist and two orthopedic spine surgeons.
Fifty implants (38 L4-5, 12 L3-4) were placed in 38 patients who completed follow-up and were included in final analysis. Three IPS designs were included (34 Medtronic X-STOP titanium, 8 X-STOP PEEK, 8 Lanx Aspen). Postoperative CT revealed 11 nondisplaced spinous process fractures in 11 patients (28.9% of patients, 22% of levels). Five fractures were associated with mild to moderate lumbar back pain and six fractures were asymptomatic. No patient reported a traumatic incident. No fracture was identifiable on plain radiographs. One fracture displaced during follow-up evaluation. Three patients underwent IPS removal and laminectomy. Three fractures healed by CT in one year. Overall, patients with fractures tended toward poorer outcomes by Zurich Claudication Questionnaire (ZCQ) (28.5% vs. 34.8% improvement in symptom severity, P = 0.496; 21.4% vs. 30.7% improvement in physical function, P = 0.199) and tended toward lower satisfaction rates (50% vs. 73.7%, P = 0.24) at one year compared to patients without fracture.
Interspinous process spacer surgery appears associated with a higher rate of early postoperative spinous process fracture than previously reported. In all cases, in this series, plain radiographs were inadequate to identify fractures because all fractures were initially minimal or nondisplaced, many patients were osteopenic, and the metallic wings of the devices often obscured fractures. Moreover, in most patients, fractures were associated with mild or no acute localized pain. This study suggests that unrecognized spinous process fracture may be responsible for a significant number of patients who experience unsatisfactory outcome after IPS surgery. CT imaging is required to identify the vast majority of such fractures.
Indirect decompression of the spinal canal and the neuroforamina by means of interspinous process distraction and limitation of extension movements. Reduction of forces acting on the posterior joint structures of a functional spinal unit (posterior anulus, facet joints, intervertebral discs).
Primary indication: Spinal claudication with improvement of the clinical symptomatology upon taking an inclined position. Secondary indication: Low back pain in the presence of accompanying retrolisthesis. Hyperlordosis Facet joint complaints Annulus lesions with high intensity zones (HIZ) M. Baastrup ("kissing spine"). Adjacent segment preservation (e.g. prophylaxis of recurrent disc herniation after discectomy or topping-off following previous fusion).
Spinal instabilities which prohibit a solid fixation of the implant (e.g. spondylolysis, isthmus fractures, condition following previous (hemi-) laminectomy) Degenerative spondylolisthesis ffl 1st degree. Severe structural narrowing of the spinal canal. Absent dynamic aspect without improvement upon inclination, segmental ankylosis.
Positioning of the patient in an inclined position. Approximately 4 cm median skin incision, bilateral access with preservation of the supraspinous ligament. Perforation of the interspinous ligament. Following interspinous distraction the adequate size implant is established. Insertion of the interspinous process distraction device (IPD) unit and fixation of the mobile wing unit from the contralateral side. Medial positioning and solid fixation of the implant by connecting the two implant units.
Lumbar orthosis (optional), otherwise no further support required. Daily living activities immediately after the operation. Physiotherapeutic exercises (optional). Low impact sporting activities from 2nd week after operation, intense/ high impact sporting activities from 6 months postoperatively.
Previous studies have reported satisfactory results for interspinous distraction devices for the treatment of dynamic spinal canal stenosis. However, the majority of these previously published studies are based on data with only shortterm follow-up or small patient numbers. In particular, the results of interspinous spacers for the treatment of different indications have not been evaluated separately. Complications and long-term results still need to be established.
The DIAM (Device for Interspinous Assisted Motion) interspinous device offers the possibility of a viscoelastic supplementation of the lumbar motion segment with a small, reversible operation. It is intended as a restabilisation procedure after a discectomy to avoid facet joint overload and as a topping of procedure for the segment adjacent to a fusion. The device has been on the German market since 2004. There are several biomechanical studies available showing an effect mainly in extension and flexion, but hardly any in rotation and lateral inclination. Despite frequent clinical use, there have only been a few, mainly retrospective clinical studies indicating the success of the implant; however, sound scientific data are missing. Several prospective, randomised, controlled studies are now underway to fill that gap. Only then will it be possible to assess whether this implant is of true value to improve clinical results and to slow down the degenerative cascade or not.
In an attempt to fill a gap between simple decompression alone and fusion in the spectrum of surgical treatment for degenerative lumbar spinal stenosis (DLSS), the authors sought to demonstrate the efficacy and reproducibility of soft stabilization with interspinous artificial ligament after microsurgical fenestration to prevent post-decompression segmental instability for mildly unstable DLSS.
Clinical outcomes from 556 patients treated with soft stabilization with artificial ligament following microdecompression for mildly unstable DLSS from March 1998 to June 2006 were retrospectively obtained from three institutions in three countries. Outcomes were measured at a mean of 48.9 months after surgery using MacNab criteria. Peri- and postoperative complications and revision surgery cases were also analyzed.
Follow-up was achieved in 391 (70.3%) of the 556 patients. Clinical outcomes were excellent in 43.7%, good in 36.7%, fair in 12.2%, and poor in 7.4% of the patients. The overall clinical success rate was 80.4%. No major complications except postoperative hematoma and wound infection (6/391 cases, 1.5%) were observed, and few revision surgeries (2.3%) were done during follow-up.
We found favorable and reproducible results with soft stabilization with artificial ligament after microdecompression for mildly unstable DLSS from three institutions in three countries. Soft stabilization with artificial ligament may be concluded to represent an effective prevention of increased post-decompression instability with reliable reproducibility for mildly unstable DLSS in carefully selected patients.
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.
In vivo creep of human lumbar motion segments and discs subject to pure centric tension is presented, in terms of aging, sex and disc level. Time-related elongations of segments L3-4, L4-5 and L5-S1 were measured during the usual 20 min long traction hydrotherapy of patients, by using a computerized subaqual ultrasound measuring method [Kurutz et al., 2002a. Orvosi Hetilap 143 (13), 673-684; Kurutz et al., 2003. Journal of Bioengineering and Biomechanics 5 (1), 67-92]. Elongation of segments was considered as a change of the distance between two adjacent spinous processes. Based on these experiments, in vivo creep of human lumbar FSUs was investigated in centric tension, in terms of sex, age and disc level. Three-parameter rheological models were used to determine viscoelastic tensile moduli of human lumbar FSUs and discs. From three time-related measured elongation values, in vivo damping constants with creep functions were calculated for each segment, in terms of sex, aging and disc level. It has been demonstrated that initial elastic elongations decrease, concerning stiffness increase with aging. Similarly, tensile creep elongations decrease, damping properties increase with aging. Former observations concerning the difference in deformation propagation of men and women in time, have been verified by means of creep analysis: although males have higher initial elastic deformability, due to a smaller damping of females, the deformation propagation of women overtakes men in creep process. This tendency is more significant with aging. Increasing damping was observed in distal direction, both for males and females.
A meta-analysis was undertaken to determine the effects of surgery for lumbar spinal stenosis on pain and disability. Seventy-four journal articles met inclusion criteria and were independently reviewed by two readers. On average, 64% of patients treated surgically for lumbar spinal stenosis were reported to have good-to-excellent outcomes. However, there was wide variation across studies in the percentage with good outcomes. Few patient characteristics were found to predict outcome. Major deficits in study design, analysis, and reporting were common, and these precluded firm conclusions.
Ceramic interspinous block (CISB) assisted anterior fusion system was developed. The system is recommended for patients with symptomatic disc degeneration and destructive lesions of the lumbar spine. One hundred and six patients who underwent CISB-assisted anterior fusion by one doctor (H.T.) from 1981 to 1987 were followed-up 2-6 years after the operation. A comparative study of the results between the CISB-assisted group and the CISB-unassisted anterior fusion group, performed by the same doctor during 1979-1981 for deranged disc, was also done. Satisfactory relief of back and leg pains, marked ADL recovery and early bone union were obtained in all of the CISB-assisted anterior fusion cases. The union rate was 98.9% in the CISB-assisted anterior fusion group, whereas in the CISB-unassisted group, it averaged 79%. The efficacy of CISB for anterior interbody fusion was also verified using a computer simulation. CISB implementation appears to create equalization of stress distribution on the graft-vertebra interface.
Posteriorly directed load to failure testing of four different types of spinal implants was performed in individual T5 to S1 vertebra harvested from seven fresh-frozen human cadaveric spines. The implants tested were: 1) Drummond spinous process wires, 2) Harrington laminar hooks, 3) Cotrel-Dubousset transpedicular screws, and 4) Steffee VSP transpedicular screws. The ultimate failure of each implant was compared with the bone mineral density of each vertebra to determine which implants, if any, were particularly advantageous in osteoporotic vertebrae. Before biomechanical testing, the spines were analyzed in vitro by dual photon absorptiometry to determine the bone mineral densities (gm/cm2) of each vertebra. The mean tensile loads to failure for each of the implants tested were as follows: Cotrel-Dubousset transpedicular screws: 345 Newtons; spinous process wire/button: 382 Newtons; Steffee transpedicular screws: 430 Newtons; and laminar hooks: 646 Newtons. The difference between the loads to failure for laminar hooks and the other implants was significant (P less than 0.05) using one-way analysis of variance. The overall correlation coefficient for bone mineral density with ultimate load to failure was 0.30 (P less than 0.001). The correlation coefficients were 0.47 (P less than 0.001) for spinous process wires alone; 0.096 (not significant) for laminar hooks alone; 0.37 (P less than 0.001) for Cotrel-Dubousset pedicle screws; and 0.48 (P less than 0.001) for Steffee pedicle screws. Of the four different implants tested, laminar hooks were most resistant to failure from posteriorly directed forces.(ABSTRACT TRUNCATED AT 250 WORDS)
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 the present work, the load-bearing role of the facet joints in a lumbar I2–3 segment is quantitatively determined by means of a three dimensional nonlinear finite element program. The analysis accounts for both material and geometric nonlinearities and treats the facet articulation as a nonlinear moving contact problem. The disc nucleus is considered as an inviscid incompressible fluid and the annulus as a composite of collagenous fibres embedded in a matrix of ground substance. The spinal ligaments are modelled as a collection of nonlinear axial elements. The loadings consist of axial compression and sagittal plane shears and bending moments, acting alone or combined.
Low-back pain has a complex and multi-faceted etiology. The articular facets have been shown to be load-bearing structures and may be a site for low-back pain. The aim of this paper is to establish the mechanism for the transmission of axial load across a facet joint and to propose a facet-related hypothesis for low-back pain. The mechanism of load transmission was studied by two methods. Lumbar segments were instrumented with an intervertebral load cell (IVLC) to measure disc load so that facet load could be deduced. The applied load was moved 10 mm anteriorly and 12.5 mm posteriorly from the center of the vertebral body. The facets then were separated from the body and loaded axially to determine their stiffness in tension and compression and to observe the failure mode of the joint. It was shown optically that compressive loading of the isolated facet joints was equivalent to spinal extension and tensile loading to spinal flexion. Lastly, a finite element model of a lumbar motion segment was developed to simulate the transmission of facet load and to study the effects of disc degeneration on facet loads. Results of the study on six lumbar segments revealed that the normal facets carried 3-25%. If the facet joint was arthritic, the load could be as high as 47%. Experiments on isolated facet joints revealed that they behaved as a stiffening spring in compression and were weak in tension.(ABSTRACT TRUNCATED AT 250 WORDS)
From a retrospective study of 412 thoracolumbar injuries, the author introduces the concept of middle column or middle osteoligamentous complex between the traditionally recognized posterior ligamentous complex and the anterior longitudinal ligament. This middle column is formed by the posterior wall of the vertebral body, the posterior longitudinal ligament and posterior annulus fibrosus. The third column appears crucial, as the mode of its failure correlates both with the type of spinal fracture and with its neurological injury. Spinal injuries were subdivided into minor and major. Minor injuries are represented by fractures of transverse processes, facets, pars interarticularis, and spinous process. Major spinal injuries are classified into four different categories: compression fractures, burst fractures, seat-belt-type injuries, and fracture dislocations. These four well-recognized injuries have been studied carefully in clinical terms as well as on roentgenograms and computerized axial tomograms. They were then subdivided into subtypes demonstrating the very wide spectrums of these four entities. The correlation between the three-column system, the classification, the stability, and the therapeutic indications are presented.
An experimentally validated simple standardized method for making precise measurements of the spinal canal directly from the video display of a CT scanner is described. Using this method, normal values for anteroposterior diameter, interpediculate distance, and cross-sectional area of the lumbar spinal canal have been determined in a series of 60 adults. A careful study of canal configuration combined with the prudent use of the normal values should allow the CT diagnosis of lumbar spinal stenosis to be made with a high level of confidence.
A basic science and clinical review of low back pain due to the lumbar zygapophysial (facet) joints was performed based on a literature search of scientific journals and textbooks. Recent studies estimate that 15% to 40% of chronic low back pain is due to the zygapophysial joints. The histological basis for zygapophysial joint pain has been scientifically established, but the precise clinical etiology remains undetermined. There are no unique identifying features in the history, physical examination, and radiological imaging of patients with pain of lumbar zygapophysial joint origin. Spine physicians diagnose zygapophysial joint pain based on analgesic response to anesthetic injections into the zygapophysial joints or at their nerve supply. Studies on treatment of isolated zygapophysial joint pain are limited. This review summarizes current understanding of lumbar zygapophysial joint disorders while highlighting the need for additional research.
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.
Lumbar motion segments were tested in vitro to examine biomechanical changes after posterior fixation by a flexible device.
To assess changes in load distribution and conformation of vertebral structures after a flexible stabilization. This should provide the foundations for a scientific understanding of the immediate effects of this surgical procedure.
Hooks were placed over the proximal spinous process and the distal laminas of a motion segment and connected by a polyester braid. Tension applied to the braid then generated a compression of the posterior elements. The force between the articular facets, the displacement of the posterior anulus fibrosus of the intervertebral disc, and the change in the relative position of the adjacent vertebrae were measured as the applied tension was increased.
Facet joint force, disc bulge, and vertebral angulation increased with applied tension until a position of "locking" was achieved, apparently when the bony margin of the superior half of the facet joint contacted the inferior pars interarticularis. A tension of between 50 to 100 N in the braid was required for this. Facet joint force was less than 40% of this, and disc bulge was only 0.15 mm. The extension of the motion segment was between 2 degrees and 8 degrees.
The results suggest that if such a system is applied surgically, stabilization is produced by compaction of the bony margins of the facet joints. Only a relatively small proportion of the posteriorly applied load is carried by the facet joints themselves, and little angulatory change is expected with minimal disc bulge.
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.
A porcine model was used to study whether muscular activation in the paraspinal muscles caused by nerve stimulation in the anulus fibrosus of a lumbar intervertebral disc could be altered by saline injection into the zygapophysial (facet) joint.
To elucidate possible mechanisms regarding the nerve pathways and interactions between the intervertebral disc, zygapophysial joints, and the paraspinal musculature.
The physiologic basis for chronic low back pain, including muscular spasm, is uncertain. Although extensive research involving the lumbar motion segments and the surrounding tissues has been performed, the neuromuscular connection has not been sufficiently investigated.
Twenty-three adolescent pigs were used to measure the electromyographic response in the paraspinal musculature to electrical stimulation of the posterolateral L3-L4 anulus fibrosus, before and after introduction of physiologic saline into the zygapophysial joint. Motor unit action potentials were recorded using three sets of needle electrodes placed into the deepest fascicles of the multifidus, bilateral to the L4 and L5 spinous processes, and into the central longissimus musculature, bilateral to the L4 spinous process.
Stimulation of the nerves within the posterolateral anulus of the disc elicited reactions in the paraspinal muscles, namely the lumbar multifidus and longissimus. Introduction of physiologic saline into the zygapophysial joint resulted in a reduction in the motor unit action potential amplitude. This reduction was manifested as an immediate and constant reduction, a graded reduction, or a delayed reaction, during which the reduction occurred an average of 5 minutes after the saline injection.
Introduction of physiologic saline into the zygapophysial joint reduced the stimulation pathway from the intervertebral disc to the paraspinal musculature. The zygapophysial joints may therefore have a regulating function, controlling the intricate neuromuscular balance in the lumbar motion segment.
Mechanical testing of cadaveric lumbar spines and dual energy radiograph absorptiometry scanning were performed.
To devise a technique to measure the strength of lumbar spinous processes and to determine the bone mineral density of the vertebrae used.
The spinous process has been identified as the weakest part of the anatomy to which a flexible fixation device can be attached. It was unknown if the spinous processes could withstand the forces applied by the device.
A hook was fitted to the spinous process of 32 lumbar vertebrae. A custom-built rig was designed to secure a vertebra to a materials testing machine. A loop of cord was passed over a bar mounted on the crosshead of the machine and around the two bollards of the hook. As the crosshead was raised, a tension was applied to the cord. Each vertebra was tested to failure. The bone mineral density of each vertebra was then measured using dual energy radiograph absorptiometry.
Failure of the specimens occurred by failure of the spinous process, pedicles, or vertebral body. The logarithm (base 10) of the load (N) at which failure occurred was 2.53 +/- 0.3, which corresponded to a mean failure load of 339 N. The bone mineral density of each vertebral body varied between 0.263 and 0.997 g/cm2. A significant linear correlation was found between bone strength and bone mineral density (P < 0.0001).
Specimens with a bone mineral density in the range of 0.263-0.997 g/cm2 failed at a mean load of 339 N when the load was applied through the spinous process hook of a flexible fixation device.
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.
The zygapophyseal joints in the lumbar spine are important structural components contributing to the stability of the lumbar motion segments. Pathology of the zygapophyseal joints in the lumbar spine may be a significant cause of low back pain and segmental instability within the lumbar spine. Management of pathology related to the zygapophyseal joints remains a difficult challenge for the physician caring for patients with spinal disorders. Future investigations with tissue engineering, ligamentous reconstructions, and intervertebral disc replacement or regeneration may have useful applications in the treatment of zygapophyseal joint pathology.
Measurement of intradiscal pressure was performed after placement of an interspinous implant in a cadaver model.
To understand the likelihood of accelerated adjacent-level disc degeneration as a result of the implant.
An interspinous implant has been developed to treat lumbar neurogenic claudication secondary to spinal stenosis that places the stenotic segment in slight flexion and prevents extension. Previous biomechanical studies demonstrated that fusing one level may significantly increase the intradiscal pressures at adjacent levels. Moreover, clinical studies have reported an increased incidence of adjacent-level degeneration after lumbar spinal fusion.
Eight cadaver lumbar specimens (L2-L5) were loaded in flexion, neutral, and extension. A pressure transducer measured intradiscal pressure and annular stresses during each of the three positions at each of the three disc levels. An appropriately sized implant was placed at L3-L4, and the pressure measurements were repeated.
The pressures at the adjacent discs were not significantly affected by the interspinous implant insertion. There was a significant decrease in intradiscal pressure at the L3-L4 disc in the posterior annulus and nucleus in the neutral and extended positions.
The implant does not significantly change the intradiscal pressures at the adjacent levels, yet it significantly unloads the intervertebral disc at the instrumented level in the neutral and extended positions. On the basis of the current findings, it does not appear that the implant causes accelerated disc degeneration at the adjacent levels.
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.
The ligaments consist of collagen bands intermingled with elastic fibers that support hundreds of pounds of stress per square inch. In the spine the basic functional unit comprises vertebrae, intervertebral disc and ligament tissues. The interspinous ligaments with the function of limiting the spine flexion are exposed to a traumatic and degenerative process that promotes pain or instability. It has been shown that aging induces structural changes to capsular, fascial and ligamentous structures, mainly to the elastic and collagen fibers. However, the relative changes with age in elastic and collagen fibers have not been quantified.
Examine the changes in the arrangement and amount of the elastic and collagen fibers of the human cervical interspinous ligament and attempt to correlate them with age.
Histomorphometric analysis of ligament samples harvested during surgery.
We studied the dorsal portion of this ligament from 17 patients aged 16 to 69 years.
Fraction of collagen and elastic fibers with linear regression analysis correlating fraction versus age.
The elastic and collagen fibers were identified by selective staining methods, and a blinded investigator using an image analysis system performed the histomorphometry.
There is an age-related progressive increase in collagen and mature and elaunin elastic fibers responsible to elasticity. However, these elastic fibers showed structural degenerative changes with aging. Furthermore, there is an age-related decrease of oxytalan elastic fibers responsible to resistance.
The aged interspinous ligament showed loss of elasticity that could alter the flexion limiting of the vertebral column.
Lumbar spinal stenosis (LSS) is often a position-dependent condition that is aggravated in extension and relieved in flexion.
Ten consecutive elderly patients with LSS were assessed postoperatively by magnetic resonance imaging and the Swiss Spinal Stenosis Questionnaire. Cross-sectional areas of the dural sac and intervertebral foramina at the stenotic level were measured postoperatively and compared with the preoperative values.
Postoperatively the cross-sectional area of the dural sac increased 16.6 mm2 or 22.3% and intervertebral foramina increased 22 mm2 or 36.5%. The intervertebral angle and the posterior disc height changed significantly. Seventy percent of the patients were satisfied with the surgical outcome.
This new surgical method is effective in elderly LSS patients.
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 authors report a series of 43 patients suffering from lower limb pain, almost constantly associated with chronic or acute backpain, treated by microsurgical nerve root decompression and by implantation of a soft intervertebral prothesis (DIAM). Satisfying results were obtained in 97% of cases, inducing the authors to consider the device a reliable tool for curing low-back pain and sciatica. Selection criteria are exposed and discussed.
Facet loading parameters of lumbar cadaver spines were measured during extension before and after placement of an interspinous process implant.
The study was undertaken to quantify the influence of an interspinous implant on facet loading at the implanted and adjacent levels during extension.
Facet loading is increased during extension and decreased during flexion. Previous studies have demonstrated that interspinous process decompression relieves disc pressure at the implanted level and does not alter disc pressure at the adjacent levels. Facet joints are believed to play a key role in back pain, especially in patients with collapsed discs and increased motion segment mobility resulting in increased facet loading.
Seven cadaver spines (L2-L5) were loaded to 15 Nm of extension and 700 N compression with and without an interspinous process implant (X STOP) placed between the L3-L4 spinous processes. Pressure-sensitive film was placed in the facet joints of the implanted and adjacent levels. After loading, the film was digitally analyzed for peak pressure, average pressure, contact area, and force. These values were compared between the intact and implanted specimens at the adjacent and implanted levels using a paired t test (P < 0.05).
The implant significantly reduced the mean peak pressure, average pressure, contact area, and force at the implanted level. The mean peak pressure, average pressure, contact area, and force at the adjacent levels were not significantly different between the intact and implanted specimens with the exception of contact area at the L2-L3 level.
Interspinous process decompression will unlikely cause adjacent level facet pain or accelerated facet joint degeneration. Furthermore, pain induced from pressure originating in the facets and/or posterior anulus of the lumbar spine may be relieved by interspinous pro-cess decompression. Clinical results from patients with a component of lower back pain suggest that this is a valid conclusion.
In this paper, we report on the development of a three-dimensional model of human lower lumbar spine based on actual geometry of L4-L5 motion segment. The simulation is performed on the model extracted from 2 mm slices of CT-Scan data of a healthy subject. The finite element model includes different parts, such as, cortical shell, cancellous core, endplates, pedicle, lamina, transverse process, and spinous process. Additionally, it takes into account the intervertebral disc including the nucleus pulposus and annulus fibrosus. The seven ligamentous structures of the L4-L5 motion segment, such as, anterior longitudinal ligament, posterior longitudinal ligament, and supraspinous ligament, were also incorporated. Various biomechanical characteristics of the computer generated model are studied under different physiological loadings. The focus of this study is on the role of posterior elements on load sharing of the lower lumbar region. The simulation yields data on the stress distribution inside the vertebrae and the amount of resulting deformation that takes place. Different simulated models of an injured lumbar spine are also being analyzed for two cases of facetectomy and degraded nucleus disorders. It is shown that the inclusion of the posterior elements along with the ligamentous tissues lead to an increase in the stiffness and stability of the L4-L5 motion segment.
The range of motion (ROM) of lumbar cadaver spines was measured during flexion, extension, axial rotation, and lateral bending following graded facetectomies and implantation of an X STOP interspinous spacer implant.
The study was performed undertaken to understand better the influence of the interspinous spacer implant on the kinematics of the lumbar spine following graded facetectomies.
Lateral lumbar spinal stenosis is often treated with a unilateral or bilateral facetectomy procedure. Previous biomechanical research has shown that a facetectomy may increase the ROM during flexion and axial rotation.
Seven cadaver spines (L2-L5) were tested in flexion, extension, axial rotation, and lateral bending, and the individual ROM of each motion segment was measured. Specimens were tested intact and following 3 graded facetectomies (i.e., unilateral medial facetectomy [UMF], unilateral total facetectomy [UTF], and bilateral total facetectomy [BTF]), with and without the X STOP.
A BTF caused a significant increase in ROM during flexion and axial rotation but not extension and lateral bending. The UMF and UTF did not affect the ROM during any of the 4 motions. The interspinous implant: (1) significantly decreased the flexion ROM for the intact, UMF, UTF, and BTF treatments; (2) significantly decreased the extension ROM for the intact, UMF, and BTF treatments but not the UTF (P < 0.13); (3) had no significant effect on the axial rotation ROM; and (4) significantly increased the lateral bending ROM for the UMF, UTF, and BTF treatments.
The results suggest that the implant may be used in conjunction with a UMF or UTF. However, the X STOP should not be used in conjunction with BTF.
A randomized, controlled, prospective multicenter trial comparing the outcomes of neurogenic intermittent claudication (NIC) patients treated with the interspinous process decompression system (X STOP) with patients treated nonoperatively.
To determine the safety and efficacy of the X STOP interspinous implant.
Patients suffering from NIC secondary to lumbar spinal stenosis have been limited to a choice between nonoperative therapies and decompressive surgical procedures, with or without fusion. The X STOP was developed to provide an alternative therapeutic treatment. METHODS.: 191 patients were treated, 100 in the X STOP group and 91 in the control group. The primary outcomes measure was the Zurich Claudication Questionnaire, a patient-completed, validated instrument for NIC.
At every follow-up visit, X STOP patients had significantly better outcomes in each domain of the Zurich Claudication Questionnaire. At 2 years, the X STOP patients improved by 45.4% over the mean baseline Symptom Severity score compared with 7.4% in the control group; the mean improvement in the Physical Function domain was 44.3% in the X STOP group and -0.4% in the control group. In the X STOP group, 73.1% patients were satisfied with their treatment compared with 35.9% of control patients.
The X STOP provides a conservative yet effective treatment for patients suffering from lumbar spinal stenosis. In the continuum of treatment options, the X STOP offers an attractive alternative to both conservative care and decompressive surgery.
- Swanson