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Characterization of Lumbar Spinous Process Morphology: A Cadaveric Study of 2,955 Human Lumbar Vertebrae.
Abstract
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.
... Somites are organized in pairs following the same organization as in the adult human spine but with additional components that will eventually disappear or fuse. The region and number of somite pairs include occipital (4), cervical (8), thoracic (12), lumbar (5), sacral (5) and coccygeal (5)(6)(7). During the sixth week of development, chondrification centers appear in the mesenchymal vertebra. ...
... The focus of existing literature is predominantly in the areas of vertebral malformation [4,5], interspinous space dimensions [6] and spinous process height [7]. While some literature exists specific to spinous process length [8], there is no documented literature investigating the right-left asymmetry of SP and TP lengths or the implications of age and sex on process length and asymmetry. ...
... Regarding TP lengths, neither the right nor the left was found to be associated with age or sex. The studies by Lin and Shaw correlated increasing process length with increasing age and the male sex [6,8]. Upon examination of the findings of this study, the question of what could cause the asymmetry from the right side to the left side of the SP and TP becomes valid. ...
Background:
Some manual therapy schools of thought rely on palpation of vertebral position via bony processes prior to the application of directional manual interventions. It is feasible that malformation or asymmetry of the spinous processes (SPs) or transverse processes (TPs), if unknown, may influence the outcome of a diagnostic palpatory exam and the application of directional manual interventions. This study provides morphometric data for the lumbar spine, to assess the occurrence of length differences in lumbar SPs and TPs occurring between the right and left sides.
Methods:
The lumbar processes were measured bilaterally in 16 adult cadaveric specimens, 9 females and 7 males ranging in age from 68 to 89 years. A measurable difference in SP length, defined as ≥ 0.1 cm, was found in 72.4% of the population, and for TP lengthin 90.6% of the population. A mean SP length difference of 0.2 ± 0.2 cm and a mean TP length difference of 0.4 ± 0.3 cm were observed. Process length was longer on average for males, and the magnitude of process length difference increased with age.
Conclusion:
These results indicate that a finding of a clinical positional fault of a vertebra through palpatory exam may be flawed.
... Common complications with implanting interspinous devices include slipping of the device from the ISS if the implanted interspinous device is too small, or fracture of the SP if it is too large [8,12,13]. The morphometric values of SP and ISS should be known in order to design and implant interspinous devices in appropriate sizes [4,14,15]. It has been reported that the morphometric values of SP and ISS correlate with sex [14][15][16][17], age [16][17][18], weight and height [4]. ...
... The morphometric values of SP and ISS should be known in order to design and implant interspinous devices in appropriate sizes [4,14,15]. It has been reported that the morphometric values of SP and ISS correlate with sex [14][15][16][17], age [16][17][18], weight and height [4]. ...
... Attention should also be paid to the bone density of patients undergoing the procedure [12]. There is a need for more information about the morphometry of SP and ISS so that complications such as SP fractures or slipping of the interspinous device due to incorrect device size can be eliminated, and implanted devices can function more safely and effectively [4,14,15]. ...
Background and objective
The aim of this study was the examination of morphometry of the spinous process (SP) and interspinous space (ISS) of the lumbar region to help provide a basis for the design and implantation of interspinous devices.
Methods
Between 2017 and 2019, 215 individuals underwent magnetic resonance imaging of the lumbar region for various reasons. No pathology was detected in these images, and the participants' age, height, and weight information when available were included in the study. From these images, the height and length of the SP and ISS in the lumbar region were noted. The heights of the SP and ISS were measured at three levels as anterior, middle, and posterior (respectively, anterior height of the spinous process [AHSP], middle height of the spinous process [MHSP], as well as posterior height of the spinous process [PHSP] for the height of SP, and anterior ISS, middle ISS and posterior ISS for the height of ISS). All measurements were compared according to the gender, age, weight, height, and body mass index of the individuals.
Results
The level with the lowest SP height and length was L5 vertebra. The ISS height and length were lowest at L4-L5. In addition, we observed a statistically significant difference at multiple levels with age, weight, height, and body mass index of the reference ranges.
Conclusion
We think that these changes should be considered when designing and implanting interspinous devices. Since there are few studies examining all these correlations, we think that the results of this study will make a unique contribution to the literature.
... Surgical procedures associated with the SPs are supposed to be easy and quick, with minimal blood loss and soft-tissue disturbance. Previous studies regarding SP morphometry have focused essentially on age-related bony changes [1,2], gender discrepancy, and the differences between lumbar levels [3][4][5]. Others have investigated SP biomechanical properties [6,7] and their morphology regarding the spine devices and surgical techniques [8][9][10]. ...
... One study has recently reported that disc degeneration and fusion intervention correlate with district kinematic alterations of interspinous processes at the involved level [26]. Moreover, spinous process slope has a direct bearing on the efficacy of interspinous process devices to achieve indirect decompression of the canal and neuroforamina [5]. Accordingly, we assume that variations in SP Table 1: Age, BMI, and SP inclination of the study groups (control vs. stenosis) for each gender separately by lumbar level. ...
... Our finding in the control group showed that the lumbar SP inclination angle became smaller from L1 to L5. This result is supported by a previous study in which measurements were based on dry skeletal cadavers (2955 human lumbar vertebrae) and found that SP slope became steeper as we descend caudally [5]. We also believe that this result partially supports the notion that the maximal slope of the L5 SP in the general population makes the surgery at the L4 and L5 levels less effective compared to horizontal SPs (L1 through L4) [5]. ...
The aim of this study is to determine the sagittal inclination of lumbar spinous processes (SPs) in individuals with degenerative lumbar spinal stenosis (DLSS). It is a retrospective computerized tomography (CT) study including 345 individuals divided into two groups: control (90 males, 90 females) and stenosis (80 males and 85 females. The SP inclination was measured in the midsagittal plane from L1 to L5 levels. Stenosis males (L3-L5) and females (L1, L4) manifested significantly greater SP inclination compared to their counterparts in the control group. Males had significantly horizontal SP orientation compared to females (L1, L2). We also found that SP inclination became steeper as we descend caudally. This study indicates that SP inclinations are significantly associated with DLSS.
... Recently, the anatomical parameters of lumbar spine process have been well described [14][15][16], and previously studies have provided information regarding thoracic spinous processes [17][18][19][20][21]. There are only few reports on the measurement of lamina space. ...
... At present, lumbar spine process related indicators have been reported [14][15][16], and there are a few reports on the measurement of thoracic spinous processes [17][18][19][20][21]. ...
... Kiranpreet Kaur M.D. [17] only reported the inclination angle of the thoracic spine. Jeremy D.Shaw et al [16] analyzed the length, width, height, slope and tail morphology of lumbar spine, but did not measure the distance between spinous processes spacing. In our study, more relevant indicators of thoracolumbar spine and lamina space were measured based on intact corpses, which include distance of spinous processes spacing, spinous process length, width, thickness, and inclination angle of the spinous process, and width, height(center, left and right) of the lamina space. ...
Background:
To analyze the anatomical parameters of the thoracolumbar spine spinous process and lamina space for Chinese anatomic study, and provide an anatomical reference for its clinical operation.
Materials and methods:
Samples from 24 adult autopsy subjects were obtained from the thoracolumbar spine spinous process and lamina space at levels T1 through L5. Direct measurements were made for the spinous process spacing distance, spinous process length, width, thickness and inclination angle, and the lamina space width, height.
Results:
1.Distance of the spine spinous process spacing: Thoracic part: The maximum tip distance was observed at T4~T5 level, and the minimum tip distance was observed at T9~T10 level. The maximum center distance and root distance were observed at T11~T12 level, and the minimum were observed at T5~T6 level separately. Lumbar part: distance of spinous process spacing in lumbar part showed an decreasing pattern from L1～L2 to L5～S1. 2.Length, width, thickness of the spine spinous process: 1)The length of the spinous process: The upper border gradually increased from T1 to T6 and then decreased till T12 region. The center region is T8 maximum, T11 minimum. The lower border length showed a decreasing trend from T1 to T12. Lumbar part: The length increased from L1 and reached maximum value at L3. Then, the length decreased gradually to reach minimum value at L5. 2)The width of the spinous process: The width showed a increasing trend from T1 to T12. Lumbar part: Maximum width was seen at L3 and a minimum L5. 3)The thickness of the spinous process: Tip thickness > center thickness > Root thickness in each thoracic and lumbar vertebra. Thoracic part: the maximum tip thickness is T1, T7 minimum, The maximum center thickness is T12, T7 minimum. The maximum root height is T6, T9 minimum. Lumbar part: Maximum tip thickness was seen at L1, and a minimum L3. Maximum center thickness was seen at L5, and a minimum L2. Maximum root thickness was seen at L2, and a minimum L1. 3.Inclination angle of the spine spinous process: The inclination angle gradually decreased from T1 to T7 to minimum value at T7 and then increased till T12 region. 4.Width and height of lamina space: 1)The width of lamina space: For thoracic part, the data became shorter gradually from T1~T2 to T5~T6, and then increased till to T11~T12. For lumbar part, the width of lamina space increased from T12~L1 to L5~S1. 2)The height of lamina space: In the thoracic vertebrae, the maximum height of center region was observed at T11~T12 and the minimum mean value was observed at T3~T4. In the lumbar vertebrae, the height of the lamina space was gradually increased from T12~L1 to L5~S1.
Conclusion:
This study reports morphometric data of the thoracolumbar spine spinous process and lamina space in the Chinese population, which provides an anatomic basis for thoracolumbar spine design of internal fixation, posterior surgery, puncture and epidural anaesthesia.
... Shunt valves were implanted for NPH. It had eight power settings (1)(2)(3)(4)(5)(6)(7)(8). A metal connector was connected to the spinal side of the shunt valve (Fig. 1A). ...
... The difference in distance was because of the thickness of the skin on the head and back. The anatomical length of the spinous process, measured from the spinolaminar line to the posterior tip of the spinous process, ranged from 24.86 mm at L5 to 33.96 mm at L3 (8). In our method, the valve placement position is L2-L3 high on the back (12). ...
Background:Adjustable shunt valves that have been developed for managing hydrocephalus rely on intrinsically magnetic components ; thus, artifacts with these valves on magnetic resonance imaging (MRI) are inevitable. No studies on valve-induced artifacts in lumboperitoneal shunt (LPS) surgery have been published. Therefore, this study aimed to evaluate valve-induced artifacts in LPS. Methods:We retrospectively reviewed all MRIs obtained between January 2023 and June 2023 in patients with an implanted Codman CERTAS Plus adjustable shunt valve (Integra Life Sciences, Princeton, New Jersey, USA). The valve was placed <1 cm subcutaneously on the paravertebral spinal muscle of the back, with its long axis perpendicular to the body axis. The scans were performed using a Toshiba Medical Systems 1.5 Tesla scanner. The in-plane artifact sizes were assessed as the maximum distance of the artifact from the expected region of the back. Results:All spinal structures or spinal cords can be recognized, even with valve-induced artifacts. The median maximum valve-induced artifact distance on T1-weighted axial imaging was 25.63 mm (mean, 25.98 mm ; range, 22.24-30.94 mm). The median maximum valve-induced artifact distance on T2-weighted axial imaging was 25.56 mm (mean, 26.27 mm ; range, 21.83-29.53 mm). Conclusion:LPS surgery with adjustable valve implantation on paravertebral muscles did not cause valve-induced artifacts in the spine and spinal cord. We considered that LPS could simplify the postoperative care of these patients. J. Med. Invest. 71 : 154-157, February, 2024
... For each participant, session-specific camera images containing the OST-HMD projected locations of the spinous processes and the criterion positions of these same spinous processes as determined by ultrasound were made semi-transparent then aligned to each other using the reference objects in each image via image processing software (Image-J, Fig. 4). The projected location of any spinous process was judged to be accurate or "on target" if its location was within known superior-inferior dimensions of the spinous process for that vertebral level (Shaw et al., 2015). If the assumed location of the spinous process fell outside these dimensions, the assumed position of the vertebra was judged to be "off-target." ...
... Overall, the mean error was 8.77 mm for all vertebrae and all sessions. Using our pre-established boundaries for on vs off-target localization (Shaw et al., 2015), the Hololens system identified the correct vertebral level 75.38% of the time in session 1 and 70.00% of the time in session 2 while ranging from 66.7% to 83.3% at different vertebral levels (Table 1). McNemar's Test demonstrated there was no statistically significant difference in on-target percentages between testing sessions at comparable vertebral levels (p > 0.05). ...
Objective
Since the discovery of ionizing radiation, clinicians have evaluated X-ray images separately from the patient. The objective of this study was to investigate the accuracy and repeatability of a new technology which seeks to resolve this historic limitation by projecting anatomically correct X-ray images on to a person’s skin.
Methods
A total of 13 participants enrolled in the study, each having a pre-existing anteroposterior lumbar X-ray. Each participant’s image was uploaded into the Hololens Mixed reality system which when worn, allowed a single examiner to view a participant’s own X-ray superimposed on the participant’s back. The projected image was topographically corrected using depth information obtained by the Hololens system then aligned via existing anatomic landmarks. Using this superimposed image, vertebral levels were identified and validated against spinous process locations obtained by ultrasound. This process was repeated 1–5 days later. The projection of each vertebra was deemed to be “on-target” if it fell within the known morphological dimensions of the spinous process for that specific vertebral level.
Results
The projection system created on-target projections with respect to individual vertebral levels 73% of the time with no significant difference seen between testing sessions. The average repeatability for all vertebral levels between testing sessions was 77%.
Conclusion
These accuracy and repeatability data suggest that the accuracy and repeatability of projecting X-rays directly on to the skin is feasible for identifying underlying anatomy and as such, has potential to place radiological evaluation within the patient context. Future opportunities to improve this procedure will focus on mitigating potential sources of error.
... A total of seven dependent parameters were used for the anterior column (six for each VB, one for the IVD) , Panjabi et al., 1991Panjabi et al., 1993, Kunkel et al., 2011, ten for the posterior column (i.e. VA) , Panjabi et al., 1991, Abuzayed et al., 2010, Kaur et al., 2016, Shaw et al., 2015, Cui et al., 2015, eleven for the posterior column (i.e. FJ) both for the thoracic and lumbar vertebrae (Panjabi et al.,1993), fourteen for each rib, which were described as planar logarithmic spirals, plus three for the sternum (Holcombe et al., 2017, Mohr et al., 2007. ...
The present paper describes a novel user-friendly fully-parametric thoraco-lumbar spine CAD model generator including the ribcage, based on 22 independent parameters (1 posterior vertebral body height per vertebra + 4 sagittal alignment parameters, namely pelvic incidence, sacral slope, L1-L5 lumbar lordosis, and T1-T12 thoracic kyphosis). Reliable third-order polynomial regression equations were implemented in Solidworks to analytically calculate 56 morphological dependent parameters and to automatically generate the spine CAD model based on
primitive geometrical features. A standard spine CAD model, representing the case-study of an average healthy adult, was then created and positively assessed in terms of spinal anatomy, ribcage morphology, and sagittal profile.
The immediate translation from CAD to FEM for relevant biomechanical analyses was successfully demonstrated,
first, importing the CAD model into Abaqus, and then, iteratively calibrating the constitutive parameters of one lumbar and three thoracic FSUs, with particular interest on the hyperelastic material properties of the IVD, and the spinal and costo-vertebral ligaments.
The credibility of the resulting lumbo-sacral and thoracic spine FEM with/without ribcage were assessed and validated throughout comparison with extensive in vitro and in vivo data both in terms of kinematics (range of motion) and dynamics (intradiscal pressure) either collected under pure bending moments and complex loading conditions (bending moments + axial compressive force).
... For a deeper evaluation of the spine biomechanics, various studies focused on alignment analysis (Laouissat et al. 2018;Yeh et al. 2021;Roussouly and Pinheiro-Franco 2011) and the analysis of the vertebral spine or single vertebra morphology (Keller et al. 2005;Lois Zlolniski et al. 2019;Casciaro and Massoptier 2007;Shaw et al. 2015). Their main drawback is using 2D images, which provide a limited visualisation of the spine. ...
Purpose
This work proposes 3D modelling and patient-specific analysis of the spine by integrating information on the tissues with geometric information on the spine morphology.
Methods
The paper addresses the extraction of 3D patient-specific models of each vertebra and the intervertebral space from 3D CT images, the segmentation of each vertebra in its three functional regions, and the analysis of the tissue condition in the functional regions based on geometrical parameters.
Results
Main results are the localisation, visualisation, quantitative, and qualitative analysis of possible damages for surgery planning and early diagnosis or follow-up studies.
Conclusions
The framework properties are discussed in terms of the spine’s morphology and pathologies on the spine district’s benchmarks.
... For a deeper evaluation of the spine's biomechanics, various studies focused on alignment analysis [37][38][39] and the study of the vertebral spine or a single vertebra's morphology [40][41][42][43]. The main drawback is the use of 2D images, which provide a limited visualisation of the spine. ...
This work addresses the patient-specific characterisation of the morphology and pathologies of muscle–skeletal districts (e.g., wrist, spine) to support diagnostic activities and follow-up exams through the integration of morphological and tissue information. We propose different methods for the integration of morphological information, retrieved from the geometrical analysis of 3D surface models, with tissue information extracted from volume images. For the qualitative and quantitative validation, we discuss the localisation of bone erosion sites on the wrists to monitor rheumatic diseases and the characterisation of the three functional regions of the spinal vertebrae to study the presence of osteoporotic fractures. The proposed approach supports the quantitative and visual evaluation of possible damages, surgery planning, and early diagnosis or follow-up studies. Finally, our analysis is general enough to be applied to different districts.
... These variations may have substantial clinical implications with respect to arthroscopic approaches to this already small area. Understanding the extent of population-and sex-dependent variation of certain anatomical parameters specifically considered during surgical techniques will benefit the surgical community by allowing customization of techniques that will optimize post-operative surgical outcomes (Eisenstein, 1977;Lee, Kim, Kim, & Chung, 1995;Shaw et al., 2015;Tan et al., 2004). Knowledge of the dimensional variations should be explored and if substantial differences are noted between populations and sex groups, these variations should be communicated with surgeons to include and consider during surgical planning. ...
Introduction
As a result of the increased utilization of neurosurgical arthroscopic techniques, investigations into population and sex‐specific trends of anatomical considerations have become increasingly important. This study aimed to investigate and describe aspects of the neuroanatomical morphometry of lumbar spines in a cadaveric and magnetic resonance imaging (MRI) sample.
Materials and Methods
Twenty white adult (>18 years) cadavers (9 males; 11 females) were obtained under Ethical clearance. The lumbar regions were dissected and the position of the dorsal root ganglion (DRG) and dimensions of Kambin's triangle were determined. Twenty‐six black adult (>18 years) MRI scans (17 males; 9 females) were obtained from an Academic Hospital and were used to determine the dimensions of the neural foramen and the DRGs within.
Results
The ganglia were mostly at the midline of the caudal pedicle. Similar to previous studies, the diagonal measurement from Kambin's triangle was the largest and the vertical measurement the shortest. Skeletal and soft‐tissue measurements indicated distinct trends when moving caudolaterally in the spine. Soft‐tissue parameters from the current study were within the upper limits of those from previous studies, whereas skeletal parameters were in agreement with those reported by previous authors.
Conclusions
Results from this study suggest a variation of certain parameters between studies with varying population groups and therefore supports the need for and the importance of possible population‐specific trends of anatomical parameters considered during surgical procedures.
... [14] The higher ICC values reported in Wong et al. study might arise from differences between the thoracic and the lumbar spine. Indeed, lumbar spinous processes are shorter and less angulated than thoracic spinous processes [36,37], and perhaps small differences in the indenter location between trials in the thoracic spine might have greater impact on the measurement than in the lumbar spine. This is also supported by Edmondston et al. (1999) study, the only other study reporting reliability of thoracic spinal stiffness assessed using a mechanical device, which reported an ICC 3,1 of 0.81 at T7 with a SEM of 1.1 N/mm for a mean spinal stiffness of 10.7 N/mm. ...
Objective
The objective was to compare thoracic spinal stiffness between healthy participants and participants with chronic thoracic pain and to explore the associations between spinal stiffness, pain and muscle activity. The reliability of spinal stiffness was also evaluated.
Material and methods
Spinal stiffness was assessed from T5 to T8 using a mechanical device in 25 healthy participants and 50 participants with chronic thoracic pain (symptoms had to be reported within the evaluated region of the back). The spinal levels for which spinal stiffness was measured were standardized (i.e. T5 to T8 for all participants) to minimize between-individual variations due to the evaluation of different spinal levels. The device load and displacement data were used to calculate the global and terminal spinal stiffness coefficients at each spinal level. Immediately after each assessment, participants were asked to rate their pain intensity during the trial, while thoracic muscle activity was recorded during the load application using surface electromyography electrodes (sEMG). Within- and between-day reliability were evaluated using intraclass correlation coefficients (ICC), while the effects of chronic thoracic pain and spinal levels on spinal stiffness and sEMG activity were assessed using mixed model ANOVAs. Correlations between pain intensity, muscle activity and spinal stiffness were also computed.
Results
ICC values for within- and between-day reliability of spinal stiffness ranged from 0.67 to 0.91 and from 0.60 to 0.94 (except at T5), respectively. A significant decrease in the global (F1,73 = 4.04, p = 0.048) and terminal (F1,73 = 4.93, p = 0.03) spinal stiffness was observed in participants with thoracic pain. sEMG activity was not significantly different between groups and between spinal levels. Pain intensity was only significantly and "moderately" correlated to spinal stiffness coefficients at one spinal level (-0.29≤r≤-0.51), while sEMG activity and spinal stiffness were not significantly correlated.
Conclusion
The results suggest that spinal stiffness can be reliably assessed using a mechanical device and that this parameter is decreased in participants with chronic thoracic pain. Studies are required to determine the value of instrumented spinal stiffness assessment in the evaluation and management of patients with chronic spine-related pain.
Introduction
We systematically describe the morphology and accessibility of interspinous spaces across age groups of patients. Our primary goal was to objectively estimate if the maneuver space for a virtual spinal needle changes with age. Our secondary goal was to estimate if the optimal site and angle for midline neuraxial puncture change with age.
Methods
Measurements were performed in mid-sagittal CT images. The CT images were retrospectively collected from the database of the Department of Radiology of our hospital. Three age groups were studied: 21–30 years (n=36, abbreviated Y(oung)), 51–60 years (n=43, abbreviated M(iddle-aged)) and older than 80 years (n=46, abbreviated Old).
A needle trajectory is defined by the chosen puncture point and by the angle at which the needle is directed to its target. We define a Spinal Accessibility Index (SAI) by numerically integrating for an interspace all possible combinations of puncture points and angles that lead to a successful virtual puncture. Successful in this context means that the needle tip reaches the spinal or epidural space without bone contact. Reproducible calculation of the SAI was performed with the help of custom-made software. The larger the value of the SAI, the more possible successful needle trajectories exist that the practitioner may choose from.
The optimal puncture point and optimal angle in an age group at a certain level of the spine are defined by the combination of these two, which generates the highest success rate of the entire sample of this age group.
Results
At all levels of the spine, the median SAI differed significantly between age groups (independent-samples Kruskal-Wallis test, p<0.001–0.047). The SAI consistently decreased with increasing age. Post-hoc analyses using pairwise comparisons showed a significantly higher SAI in group Y versus Old at all levels (p<0.001—0.006) except at level thoracic (Th)1–Th2 (p=0.138). The SAI was significantly higher in group M versus Old at all levels (p<0.001–0.028) except at level Th1–Th2 (p=0.061), Th4–Th5 (p=0.083), Th9–Th10 (p=1.00) and Th10–Th11 (p=1.00).
Conclusions
Needle maneuver space in midline neuraxial puncture significantly decreases with progressive age at all levels of the spine. Optimal puncture points and angles are similar between age groups.
The interspinous spacer (ISP) is a minimally invasive surgical device implanted into the interspinal space to treat lumbar degenerative diseases. Unfortunately, ISPs sometimes cause device breakage and spinal process fracture. Our aim was to elaborate the design of lumbar customized posterior fixation system (CISP system), encompassing a customized ISP body and transfacetopedicular screws, and examine its biomechanical effect on the lumbar spine using finite element (FE) analysis. We constructed the CISP system, based on the interspinal anatomical data at the surgical level. We generated the L3-S1 FE models, implanted with the polyetheretherketone (PEEK) CISP system, titanium alloy (TI) CISP system, and Coflex device at the L4/L5 segment, and determined the lumbar segmental range of motions (ROMs), intervertebral discs (IVD) peak stress, and implant stresses. The CISP system enhanced mobility restriction at the surgical level, compared to the Coflex device. Furthermore, the IVD peak stress reduction was more obvious in the CISP system than the Coflex device, particularly during extension. Under the same motion mode, the maximum stress on the TI CISP system was smaller than on the Coflex device, but larger than the PEEK CISP system. Given these evidences, PEEK appeared to be a better material for the CISP body.
Patient positioning and needle puncture site are important for lumbar neuraxial anesthesia. We sought to identify optimal patient positioning and puncture sites with a novel ultrasound registration. We registered a statistical model to volumetric ultrasound data acquired from volunteers (n = 10) in three positions: (i) prone; (ii) seated with thoracic and lumbar flexion; and (iii) seated as in position ii, with a 10° dorsal tilt. We determined injection target size and penetration success by simulating lumbar injections on validated registered models. Injection window and target area sizes in seated positions were significantly larger than those in prone positions by 65% in L2-3 and 130% in L3-4; a 10° tilt had no significant effect on target sizes between seated positions. In agreement with computed tomography studies, simulated L2-3 and L3-4 injections had the highest success at the 50% and 75% midline puncture sites, respectively, measured from superior to inferior spinous process. We conclude that our registration to ultrasound technique is a potential tool for tolerable determination of puncture site success in vivo.
A large number of interspinous process devices (IPD) have been recently introduced to the lumbar spine market as an alternative to conventional decompressive surgery in managing symptomatic lumbar spinal pathology, especially in the older population. Despite the fact that they are composed of a wide range of different materials including titanium, polyetheretherketone, and elastomeric compounds, the aim of these devices is to unload spine, restoring foraminal height, and stabilize the spine by distracting the spinous processes. Although the initial reports represented the IPD as a safe, effective, and minimally invasive surgical alternative for relief of neurological symptoms in patients with low back degenerative diseases, recent studies have demonstrated less impressive clinical results and higher rate of failure than initially reported. The purpose of this paper is to provide a comprehensive overview on interspinous implants, their mechanisms of action, safety, cost, and effectiveness in the treatment of lumbar stenosis and degenerative disc diseases.
Transpedicular screw fixation has some disadvantages such as postoperative back pain through wide muscle dissection, long operative time, and cephalad adjacent segmental degeneration (ASD). The purposes of this study are investigation and comparison of radiological and clinical results between interspinous fusion device (IFD) and pedicle screw.
From Jan. 2008 to Aug. 2009, 40 patients underwent spinal fusion with IFD combined with posterior lumbar interbody fusion (PLIF). In same study period, 36 patients underwent spinal fusion with pedicle screw fixation as control group. Dynamic lateral radiographs, visual analogue scale (VAS), and Korean version of the Oswestry disability index (K-ODI) scores were evaluated in both groups.
The lumbar spine diseases in the IFD group were as followings; spinal stenosis in 26, degenerative spondylolisthesis in 12, and intervertebral disc herniation in 2. The mean follow up period was 14.24 months (range; 12 to 22 months) in the IFD group and 18.3 months (range; 12 to 28 months) in pedicle screw group. The mean VAS scores was preoperatively 7.16±2.1 and 8.03±2.3 in the IFD and pedicle screw groups, respectively, and improved postoperatively to 1.3±2.9 and 1.2±3.2 in 1-year follow ups (p<0.05). The K-ODI was decreased significantly in an equal amount in both groups one year postoperatively (p<0.05). The statistics revealed a higher incidence of ASD in pedicle screw group than the IFD group (p=0.029).
Posterior IFD has several advantages over the pedicle screw fixation in terms of skin incision, muscle dissection and short operative time and less intraoperative estimated blood loss. The IFD with PLIF may be a favorable technique to replace the pedicle screw fixation in selective case.
For the past 25 years NIH Image and ImageJ software have been pioneers as open tools for the
analysis of scientific images. We discuss the origins, challenges and solutions of these two programs,
and how their history can serve to advise and inform other software projects.
Blinded radiographic analysis of CT scans reformatted for precise lumbar spinous process (LSP) measurement.
To investigate the effect of ageing on LSP morphology and influence of LSP morphology on lumbar spine sagittal alignment.
There is little data reporting the influence of ageing on spinous process size. There is data describing the increase in size of other body parts with age, such as the femur, ears, vertebral body, and nose. Several old cadaveric and radiographic studies have reported the formation of osseous spurs within the supraspinous and interspinous ligaments.
200 abdominal CT scans taken for trauma and vascular investigation were reformatted to allow precise bony measurement of the lumbar spine. Two observers were blinded from the age and demographics of the patients. Sagittal and coronal plane projections were used to measure the height and width of the spinous processes (L1-L5), respectively. The relationship between spinous process size, age, and supine lordosis was investigated.
LSP height increases by 0.03-0.07 mm/year (p < 10(-3) to 10(-8)) and width by 0.05-0.06 mm/year (p < 10(-11) to 10(-15)). Lumbar lordosis decreases with increasing LSP height (p < 0.0004) but is not related to increasing LSP width (p = 0.195). Supine lordosis increases by 0.1°/year (p = 0.004).
This study demonstrates that the dimensions of the LSP change with age. Increases in LSP height and even more impressive increases in LSP width occur with advancing age. There is an inverse relationship between lumbar lordosis and LSP height.
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.
An interspinous process implant has been developed to treat patients suffering from neurogenic intermittent claudication secondary to lumbar spinal stenosis. As most patients who suffer from spinal stenosis are over the age of 50 and may have weaker bones, it is imperative to know how bone mineral density (BMD) correlates with lateral spinous process strength. The study was undertaken to characterize the lateral failure loads of the spinous process, correlate the failure loads to BMD, and compare the failure loads to the loads required to insert an interspinous process implant. Spinous process lateral failure loads were assessed, correlated to BMD, and compared to the loads required to insert an interspinous process implant. Mean spinous process failure loads were significantly greater than the lateral insertion load of the interspinous process implant. There was a significant relationship between the BMD and spinous process failure load. The technique used to insert the interspinous implant poses little risk to spinous process failure. There is ample margin of safety between the insertion loads and spinous process failure loads. The significant relationship between BMD and spinous process failure load suggests that patients with lower BMD must be approached with more caution during the implant insertion procedure.
This study details the quantitative three-dimensional surface anatomy of human lumbar vertebrae based on a study of 60 vertebrae. The two lower vertebrae (L4 and L5) appeared to be transitional toward the sacral region, whereas the upper two vertebrae (L1 and L2) were transitional toward the thoracic region. Means and standard errors of the means for linear, angular, and area dimensions of vertebral bodies, spinal canal, pedicle, pars interarticularis, spinous and transverse processes were obtained for all lumbar vertebrae. This information provides a better understanding of the spine, and allows for a more precise clinical diagnosis and surgical management of spinal problems. The information is also necessary for constructing accurate mathematical models of the human spine.
Background Context
While multiple mechanisms of device attachment to the spinous processes exist, there is a paucity of data regarding lumbar spinous process morphology and peak failure loads.
Purpose
Using an in-vitro human cadaveric spine model, the primary objective of the current study was to compare the peak load and mechanisms of lumbar spinous process failure with variation in spinous process hole location and pullout direction. A secondary objective was to provide an in-depth characterization of spinous process morphology.
Study Design
Biomechanical and anatomical considerations in lumbar spinous process fixation using an in-vitro human cadaveric model.
Methods
A total of 12 intact lumbar spines were utilized in the current investigation. The vertebral segments (L1-L5) were randomly assigned to 1 of 5 treatment groups with variation in spinous process hole placement and pullout direction: 1) Central hole placement with superior pullout (n=10), 2) Central hole placement with inferior pullout (n=10), 3) Inferior hole placement with inferior pullout (n=10), 4) Superior hole placement with superior pullout (n=10) and 5) Intact spinous process with superior pullout (n=14). A 4mm diameter pin was placed through the hole followed by pullout testing using a material testing system (MTS). As well, the bone mineral density (BMD) (g/cm3) was measured for each segment. Data were quantified in terms of anatomic dimensions (mm), peak failure loads (Newtons) and fracture mechanisms, with linear regression analysis would identify relationships between anatomic and biomechanical data.
Results
Based on anatomic comparisons, there were significant differences between the anteroposterior and cephalocaudal dimensions of the L5 spinous process versus L1 through L4 (p<0.05). Statistical analysis of peak load at failure of the 4 reconstruction treatments and intact condition demonstrated no significant differences between treatments (range 350 to 500 Newtons) (p>0.05). However, a significant linear correlation was observed between peak failure load and anteroposterior and cephalocaudal dimensions (p<0.05). Correlation between BMD and peak spinous processes failure load was approaching statistical significance (p=0.08). 30/54 specimens failed via direct pullout (plow through), while 8/54 specimens demonstrated spinous process fracture. The remaining cases failed via plow through followed by fracture of the spinous process 16/54 (29%).
Conclutions
The current study demonstrated that variation in spinous process hole placement did not significantly influence failure load. However, there was a strong linear correlation between peak failure load and the anteroposterior and cephalocaudal anatomic dimensions. From a clinical standpoint, the findings of the current study indicate that attachment through the spinous process provides a viable alternative to attachment around the spinous processes. In addition, the anatomic dimensions of the lumbar spinous processes have a greater influence on biomechanical fixation than either hole location or bone mineral density.
COMMENTARY ON: Kim DH, Shanti N, Tantorski ME, et al. Association between degenerative spondylolisthesis and spinous process fracture after interspinous process spacer surgery. Spine J 2012;12:466-72 (in this issue).
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.
The X-Stop Interspinous Process Decompression System (St. Francis Medical Technologies, Concord, CA) is an interspinous device used with increasing frequency in the treatment of degenerative lumbar spine conditions. To date, limited data are available on complications observed in association with X-Stop procedures, and even less information exists on their underlying causes. The aim of this study was to analyze a series of complications occurring at a single institution and their potential causes and propose an anatomic scoring system that may help to classify patients and prevent complications.
Sixty-nine patients were treated with the X-Stop. Forty-six single-level and 23 double-level operations (92 devices) were performed according to recommended indications. The mean follow-up duration was 23 months.
Eight complications were recorded: 4 device dislocations and 4 spinous process (SP) fractures, including 2 spontaneous fractures of the L4 SP in patients treated at L3-L4 and L4-L5. The following anatomic variants were demonstrated: markedly decreased interspinous distance (kissing spine-like), with concomitant facet joint hypertrophy, a posterior V-shaped interspinous area, limited accessibility of the space between the base and the tip of the SP because of facet joint hypertrophy and variations in the shape of the inferior surface of the cranial SP.
This is the first study focusing on interspinous distractor complications and the anatomic features of the SP and interspinous areas of the patients, which could potentially be the underlying causes for those complications. The X-Stop can be an effective treatment option, but it is not a panacea for all patients with degenerative lumbar spine conditions. Not only do the clinical indications deserve attention, but also, and most importantly, the patient's anatomic characteristics.
Unlabelled:
In this study, we developed a complete description of the morphology of the proximal femur. Then, using this framework, we (1) determined normal population means, standard deviations, and ranges; (2) established differences among subpopulations; and (3) showed correlations among the various measurements. To accomplish these objectives, we analyzed 375 adult femurs. Specimens were digitally photographed in standardized positions, measurements being obtained using ImageJ software. Three parameters of the head-neck relationship were assessed. Translation was examined through four raw offset measurements (anterior, posterior, superior, inferior) used to calculate anterior-posterior and superior-inferior ratios. Rotation was investigated through anteroposterior (AP) and lateral physeal angles. Concavity was examined using alpha, beta, gamma, and delta angles. Two parameters of the neck-shaft relationship were assessed, neck version and angle of inclination. Average anterior-posterior and superior-inferior ratios were 1.14 and 0.90. Average AP and lateral physeal angles were 74.33 degrees and 81.83 degrees , respectively. Averages for alpha, beta, gamma, and delta angles were 45.61 degrees , 41.85 degrees , 53.46 degrees , and 42.95 degrees , respectively. Average neck version and angle of inclination were 9.73 degrees and 129.23 degrees , respectively. Differences existed between males and females and between those younger and older than 50 years. Correlations were observed between translation and concavity, and translation and the neck-shaft relationships.
Level of evidence:
Level II, prognostic study. See the Guidelines for Authors for a complete description of levels of evidence.
This paper presents a general statistical methodology for the analysis of multivariate categorical data arising from observer reliability studies. The procedure essentially involves the construction of functions of the observed proportions which are directed at the extent to which the observers agree among themselves and the construction of test statistics for hypotheses involving these functions. Tests for interobserver bias are presented in terms of first-order marginal homogeneity and measures of interobserver agreement are developed as generalized kappa-type statistics. These procedures are illustrated with a clinical diagnosis example from the epidemiological literature.
This study details the quantitative three-dimensional surface anatomy of human lumbar vertebrae based on a study of 60 vertebrae. The two lower vertebrae (L4 and L5) appeared to be transitional toward the sacral region, whereas the upper two vertebrae (L1 and L2) were transitional toward the thoracic region. Means and standard errors of the means for linear, angular, and area dimensions of vertebral bodies, spinal canal, pedicle, pars interarticularis, spinous and transverse processes were obtained for all lumbar vertebrae. This information provides a better understanding of the spine, and allows for a more precise clinical diagnosis and surgical management of spinal problems. The information is also necessary for constructing accurate mathematical models of the human spine.
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)
Starting from about the 40th year of life the lumbar spinous processes of man undergo morphological changes, which mainly affect their posterior edges. These changes consist of asymptomatic osseous appositions or spurs radiologically visible in the lateral view, with a major incidence in the elderly. Spondyloarthritis is a constant accompanying finding. Histologically the condition corresponds' to a process of substitution by Haversian bone of a layer of calcified fibrocartilage, which constantly occupies the ligamentous and tendinous attachments for a variable distance. While in the young adult fibrocartilaginous metaplasia is limited to the bony attachments of the spinous ligaments, in the elderly it spreads to the greater part or to all of their thickness. The author believes that such a phenomenon is due to a reduced flexibility of the vertebral column as a whole and to exaggerated lumbar lordosis with ageing. The elongation of the lumbar spinous processes secondary to osseous appositions increases the posterior arm of the lever and favours the "extensores spinae" m.
The results of a morphometric study of selected human vertebrae undertaken to provide data for implant design are presented in this report. Twenty-seven dimensions were measured from thoracic (T2, T7, T12) and lumbar (L1-L5) vertebrae using prepared spinal columns from 30 skeletons belonging to the Hamann-Todd Osteological Collection. Maximum and minimum pedicle dimensions indicated that the pedicles are less symmetric cephalad than they are caudal. Vertebral body height increases caudally except posteriorly where, after an initial increase, it decreases in the lower lumbar region. Major and minor body diameters and the major spinal canal diameter slightly increase caudally, whereas minor spinal canal diameter exhibits little or no change.
A radiologic-pathologic correlative investigation of the normal age-related alterations in the spinous processes and intervening soft tissues was performed using cadaveric spines and both ancient and modern macerated vertebral specimens. Extreme lordosis in the cervical or lumbar spine results in spinous process apposition, formation of interspinous bursae, eburnation with osteophytosis, and creation of synovial articulations. A concomitant degenerative enthesopathy involves the supraspinous or interspinous ligamentous attachments in any spinal segment. The differential diagnosis of this phenomenon, the clinical significance of which in a given patient is controversial, includes rheumatoid and other inflammatory arthritides as well as crystal deposition disease.
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.
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 prototype flexible fixation system for the lumbar spine was subjected to tensile testing to failure and cyclic tensile testing in order to determine any regions of weakness. The system consisted of a spinous process hook and two laminar hooks made of stainless steel (316L). Each laminar hook was attached to the spinous process hook by a loop of polyester braid secured by a crimped metal sleeve. In five tensile tests, the system failed by irreversible deformation of the spinous process hook at 2.5 +/- 0.3 kN (mean +/- standard deviation). In three cyclic tests, in which the applied tension varied sinusoidally between 0.04 and 0.4 kN at a frequency of 5 Hz, failure occurred after less than 400,000 loading cycles. This occurred as a result of fatigue crack initiation and propagation in the spinous process hook. A finite element model showed a stress concentration in the region where the crack occurred, which raised the applied stress above the tensile fatigue strength of this stainless steel. The spinous process hook was redesigned for manufacture in a titanium alloy (Ti-6AI-4V ELI) to minimize artefacts in magnetic resonance imaging. Further finite element models showed no unacceptable stress concentrations.
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 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.
A growing number of interspinous process devices have been introduced to the lumbar spine implant market. Implant designs vary from static spacers to dynamized devices. Furthermore, they are composed of a range of different materials including bone allograft, titanium, polyetheretherketone, and elastomeric compounds. The common link between them is the mechanical goal of distracting the spinous processes to affect the intervertebral relationship. In contrast, the purported clinical goals are more variable, ranging from treatment of degenerative spinal stenosis, discogenic low back pain, facet syndrome, disk herniations, and instability. Though some clinical data exist for some of these devices, defining the indications for these minimally invasive procedures will be crucial. Indications should emerge from thoughtful consideration of data from randomized controlled studies.