Vertebral Motion Research Articles

Instantaneous centers of rotation for lumbar segmental extension in vivo

The study aimed to map instantaneous centers of rotation (ICRs) of lumbar motion segments during a functional lifting task and examine differences across segments and variations caused by magnitude of weight lifted. Eleven healthy participants lifted loads of three different magnitudes (4.5, 9, and 13.5kg) from a trunk-flexed (~75°) to an upright position, while being imaged by a dynamic stereo X-ray (DSX) system. Tracked lumbar vertebral (L2-S1) motion data were processed into highly accurate 6DOF intervertebral (L2L3, L3L4, L4L5, L5S1) kinematics. ICRs were computed using the finite helical axis method. Effects of segment level and load magnitude on the anterior-posterior (AP) and superior-inferior (SI) ICR migration ranges were assessed with a mixed-effects model. Further, ICRs were averaged to a single center of rotation (COR) to assess segment-specific differences in COR AP- and SI-coordinates. The AP range was found to be significantly larger for L2L3 compared to L3L4 (p=0.02), L4L5 and L5S1 (p<0.001). Average ICR SI location was relatively higher – near the superior endplate of the inferior vertebra – for L4L5 and L5SI compared to L2L3 and L3L4 (p≤0.001) – located between the mid-transverse plane and superior endplate of the inferior vertebra – but differences were not significant amongst themselves (p>0.9). Load magnitude had a significant effect only on the SI component of ICR migration range (13.5kg>9kg and 4.5kg; p=0.049 and 0.017 respectively). The reported segment-specific ICR data exemplify improved input parameters for lumbar spine biomechanical models and design of disc replacements, and base-line references for potential diagnostic applications.

Effects of whole spine alignment patterns on neck responses in rear end impact

ABSTRACTObjective: The aim of this study was to investigate the whole spine alignment in automotive seated postures for both genders and the effects of the spinal alignment patterns on cervical vertebral motion in rear impact using a human finite element (FE) model.Methods: Image data for 8 female and 7 male subjects in a seated posture acquired by an upright open magnetic resonance imaging (MRI) system were utilized. Spinal alignment was determined from the centers of the vertebrae and average spinal alignment patterns for both genders were estimated by multidimensional scaling (MDS). An occupant FE model of female average size (162 cm, 62 kg; the AF 50 size model) was developed by scaling THUMS AF 05. The average spinal alignment pattern for females was implemented in the model, and model validation was made with respect to female volunteer sled test data from rear end impacts. Thereafter, the average spinal alignment pattern for males and representative spinal alignments for all subjects were implemented in the validated female model, and additional FE simulations of the sled test were conducted to investigate effects of spinal alignment patterns on cervical vertebral motion.Results: The estimated average spinal alignment pattern was slight kyphotic, or almost straight cervical and less-kyphotic thoracic spine for the females and lordotic cervical and more pronounced kyphotic thoracic spine for the males. The AF 50 size model with the female average spinal alignment exhibited spine straightening from upper thoracic vertebra level and showed larger intervertebral angular displacements in the cervical spine than the one with the male average spinal alignment.Conclusions: The cervical spine alignment is continuous with the thoracic spine, and a trend of the relationship between cervical spine and thoracic spinal alignment was shown in this study. Simulation results suggested that variations in thoracic spinal alignment had a potential impact on cervical spine motion as well as cervical spinal alignment in rear end impact condition.

Biomechanical Analysis of Intervertebral Cement Extravasation in Vertebral Motion Segments.

Kyphoplasty is a therapeutic option for pain relief in the setting of compression fractures. Cement extravasation into adjacent disks is a common occurrence. The biomechanical and clinical consequences of cement in the disks currently are unknown. This study investigated the biomechanical effects of cement extravasation into the intervertebral disk in a human cadaveric model. Seven thoracolumbar and lumbar embalmed human cadaveric motion segments were evaluated in axial rotation, right and left lateral bending, and flexion and extension. Stiffness was calculated at baseline and following injection of 1 mL of cement into the intervertebral disk. There was a 13.4% (P=.041) increase in stiffness in axial rotation compared with preinjection motion segments. No significant difference was observed in lateral bending or flexion and extension. In this model, cement extravasation into the disk space increased stiffness in axial rotation. [Orthopedics. 2017; 40(2):e300-e304.].

Structural and functional characteristics of the thoracolumbar multifidus muscle in horses.

The multifidus muscle fascicles of horses attach to vertebral spinous processes after crossing between one to six metameres. The fascicles within one or two metameres are difficult to distinguish in horses. A vertebral motion segment is anatomically formed by two adjacent vertebrae and the interposed soft tissue structures, and excessive mobility of a vertebral motion segment frequently causes osteoarthropathies in sport horses. The importance of the equine multifidus muscle as a vertebral motion segment stabilizer has been demonstrated; however, there is scant documentation of the structure and function of this muscle. By studying six sport horses postmortem, the normalized muscle fibre lengths of the the multifidus muscle attached to the thoracic (T)4, T9, T12, T17 and lumbar (L)3 vertebral motion segments were determined and the relative areas occupied by fibre types I, IIA and IIX were measured in the same muscles after immunohistochemical typying. The values for the normalized muscle fibre lengths and the relative areas were analysed as completely randomized blocks using an anova (P≤0.05). The vertebral motion segments of the T4 vertebra include multifidus bundles extending between two and eight metameres; the vertebral motion segments of the T9, T12, T17 and L3 vertebrae contain fascicles extending between two and four metameres The muscle fibres with high normalized lengths that insert into the T4 (three and eight metameres) vertebral motion segment tend to have smaller physiological cross-sectional areas, indicating their diminished capacity to generate isometric force. In contrast, the significantly decreased normalized muscle fibre lengths and the increased physiological cross-sectional areas of the fascicles of three metameres with insertions on T9, T17, T12, L3 and the fascicles of four metameres with insertions on L3 increase their capacities to generate isometric muscle force and neutralize excessive movements of the vertebral segments with great mobility. There were no significant differences in the values of relative areas occupied by fibre types I, IIA and IIX. In considering the relative areas occupied by the fibre types in the multifidus muscle fascicles attached to each vertebral motion segment examined, the relative area occupied by the type I fibres was found to be significantly higher in the T4 vertebral motion segment than in the other segments. It can be concluded that the equine multifidus muscle in horses is an immunohistochemically homogeneous muscle with various architectural designs that have functional significance according to the vertebral motion segments considered. The results obtained in this study can serve as a basis for future research aimed at understanding the posture and dynamics of the equine spine.

Regeneration of intervertebral disc by way using of allogeneic chondrocytes cultivated in vitro in the light of concept for restabilization of the spine(experimental investigation)

The intervertebral disc (ID) has low reparative capacity. In this regard, researcher aimed at improving the capacity of the re­parative structures are carried out. A variety of growth factors, mesenchymal stem cells, autologous and allogenic chondrocytes, etc are used for this purposes. Objective: to study the structure of the traumatized intervertebral disc after transplantation of allogenic chondroсуtes in combination with spinal restabiliza­tion using method of dynamic spine neutralization of vertebral motion unit (VMU). Methods for optimizing ID regeneration in the rat tail vertebral segment we selected high-density culture of chondrocytes obtained from the limb bud 7–10 day old rat embryos in which cells retain cartilaginous phenotype and gen­otype was confirmed by electron microscopy. Performed four se­ries of experiments: I — intact animals, II — ID injury (control), III — traumatic ID injury with dynamic neutralization (method G. Dubois et al, 1999), IV — ID injury with dynamic neutraliza­tion and transplantation of chondrocytes. One month the opera­tion the animals were euthanized, and a comparative morpho­logical analysis with morphometry was carried out. Results: it found that uncontrolled movements in the injured VMU lead to destructive changes in the ID. In terms of restabilization and dy­namic neutralization of the vertebral motor segment ID has been replaced by connective tissue, its height reduced. Chondrocyte culture is different from the fibrous ring and nucleus pulposus cells. However, with the introduction of chondrocytes in the in­jured ID and maintaining the controlled mobility of the VMU the proliferation of hyaline cartilage in its peripheral parts has been noted. Conclusion: combination of allogeneic chondro­cytes transplantation into disk and dynamic neutralization leads to the formation of hyaline cartilage territories and maintains the height of the injured ID.

Time course of osteoporotic vertebral fractures by magnetic resonance imaging using a simple classification: a multicenter prospective cohort study.

Magnetic resonance imaging (MRI) is useful in diagnosing osteoporotic vertebral fractures (OVFs). This study investigated the time course of OVFs by MRI using a simple classification. This multicenter cohort study was performed from 2012 to 2015. Consecutive patients with ≤2-week-old OVFs were enrolled in 11 institutions. MRI was performed at enrollment and at 1-, 3-, 6-, and 12-month follow-up. Signal changes on T1-weighted imaging (T1WI), T2WI, and short τ inversion recovery (STIR) were classified according to signal intensity. Height and angular motion of vertebral bodies were also measured. The 6-month follow-up was completed by 153 patients. At enrollment, fractured vertebrae signal changes were 43% diffuse and 57% confined low on T1WI; on T2WI, 56, 24, and 5% were confined low, high, and diffuse low, respectively; on STIR, 100% were high. On T1WI, diffuse low remained most common (90% at 1month and 60% at 3months) until 6 and 12months, when most were confined low (54 and 52%, respectively). On T2WI, confined low remained most common (decreasing to 41% at 12months). On STIR, high signal change was shown in 98, 87, and 64% at 3, 6, and 12months, respectively. At 3, 6, and 12months, diffuse low signal change was associated with significantly lower vertebral height, and high signal change was associated with significantly greater angular motion. MRI signal changes were associated with the compression degree and angular motion of fractured vertebrae. This classification showed sufficient reliability in categorizing MRI findings of OVFs.

Effects of conventional and slanted ventral slot procedures on the biomechanical behavior of the C5-C6 vertebral motion unit in dogs

OBJECTIVE To compare the effects of conventional and slanted ventral slot procedures on the biomechanical behavior of the C5-C6 vertebral motion unit (VMU) in dogs. SAMPLE 14 vertebral columns (C4 through C7) from canine cadavers. PROCEDURES Specimens were assigned to a conventional or slanted ventral slot group (n = 7/group). For each specimen, the C5-C6 VMU was tested in ventral and dorsal bending and positive and negative axial torsion before and after surgery. Range of motion (ROM), stiffness, and energy absorption were compared between the 2 groups. RESULTS Both procedures significantly increased the ROM and stiffness and significantly decreased the energy absorption of the C5-C6 VMU in ventral and dorsal bending. Both procedures also increased the ROM in positive and negative axial torsion. In negative torsion, total stiffness and stiffness over the maximum ROM tested decreased less for the slanted slot procedure than for the conventional slot procedure. There were no significant differences between procedures for any of the other biomechanical outcomes examined. CONCLUSIONS AND CLINICAL RELEVANCE Results suggested that the biomechanical response of the C5-C6 VMU to the conventional and slanted ventral slot procedures was not significantly different, especially when considering postsurgical instability induced by both procedures. This was most likely due to disruption of the nucleus pulposus and dorsal annulus fibrosus of the disk with both procedures. On the basis of these findings, neither procedure appeared biomechanically superior. Comparative clinical studies are warranted to further evaluate the 2 procedures.

Predicting delayed union in osteoporotic vertebral fractures with consecutive magnetic resonance imaging in the acute phase: a multicenter cohort study.

The purpose of the present study is to determine predictive radiological findings for delayed union by magnetic resonance imaging (MRI) and plain X-rays at two time points in the acute phase of OVFs. This multicenter cohort study was performed from 2012 to 2015. A total of 218 consecutive patients with OVFs ≤2weeks old were enrolled. MRIs and plain X-rays were performed at the time of enrollment and at 1- and 6-month follow-ups. Signal changes on T1-weighted imaging (T1WI) were classified as diffuse low-, confined low-, or no-signal change; those on T2WI were classified as high (similar to the intensity of cerebrospinal fluid), confined low-, diffuse low-, or no-signal change. The angular motion of the fractured vertebral body was measured with X-rays. A total of 153 patients completed the 6-month follow-up. A high-signal change on T2WI was most useful in predicting delayed union. Sensitivity, specificity, and positive predictive values were 53.3, 87.8, and 51.6% at enrollment and 65.5, 84.8, and 51.4% at the 1-month follow-up, respectively. The positive predictive value increased to 62.5% with observation of high- or diffuse low-signal changes at both enrollment and the 1-month follow-up. The cutoff value of vertebral motion was 5 degrees. Sensitivity and specificity at enrollment were 52.4 and 74.1%, respectively. This study demonstrated the radiological factors predicting delayed union after an OVF. T2 high-signal changes showed the strongest association with delayed union. Consecutive MRIs were particularly useful as a differential tool to predict delayed union following OVFs.

The clinical efficacy of pathologic vertebral surgery for thoracic and lumbar tuberculosis

Objective To discuss the clinical efficacy of surgical treatment of pathologic vertebral surgery for thoracic and lumbar tuberculosis. Methods All of 322 cases of thoracic and lumbar spinal tuberculosis patients from December 2003 to June 2014 were retrospectively analyzed in our department. All patients were underwent debridement, fusion and nerve decompression surgery. According to different fixed methods, patients were divided into pathologic vertebral surgery group (fixation completed within lesions invaded motion unit) including 91 males and 100 females, with an average age of 41.53 years, and non-pathologic vertebral surgery group (long segments or short segment fixation) including 61 males and 70 females, with an average age of 42.72 years. We observed the tuberculosis cure rate, degrees of deformity, pain and neurological recovery, operative time, blood loss and complications by follow-up. Results The average follow-up time was 75.52 months in pathologic vertebral surgery group and 76.21 months in non-pathologic vertebral surgery group. The total number of pathologic vertebras in pathologic vertebral surgery group and non-pathologic vertebral surgery group were 277 and 218 respectively, and the average was 1.45 and 1.66. The total number of fixed segments was 277 in pathologic vertebral surgery group and 485 in non-pathologic vertebral surgery group, and the average fixed segments was 1.45 and 3.70. The cure rate was 85.86% in pathologic vertebral surgery group and 85.49% in non-pathologic vertebral surgery group at 6 months postoperatively, and 98.95% and 98.47% at the last follow-up time, with no significant difference between groups. Graft fusion rate was 89.00% in pathologic vertebral surgery group and 89.31% in non-pathologic vertebral surgery group 6 months postoperatively, 98.38% and 98.47% at the last follow-up time, without significant difference. In lumbar spine, the average correction of Cobb's angle was 12.4° in pathologic vertebral surgery group and 13.1° in non-pathologic vertebral surgery group, and the average angle loss was 1.3 and 1.4°, with no significant difference. In thoracolumbar, the average correction of Cobb's angle was 10.9°in pathologic vertebral surgery group and 11.1°in non-pathologic vertebral surgery group, and the average angle loss was 1.7°and 1.5° respectively, without significant difference. However, in thoracic, the average correction of Cobb's angle was 10.2° in pathologic vertebral surgery group and 12.7° in non-pathologic vertebral surgery group, and the average angle loss was 3.6° and 2.5°respectively, with significant difference. The mean operation time was 210.45 min in pathologic vertebral surgery group and 210.45 min in non-pathologic vertebral surgery group, with significant difference. The average blood loss was 726.12 ml in pathologic vertebral surgery group and 726.12 ml in non-pathologic vertebral surgery group, with significant difference. The complication rate was 11.51% in pathologic vertebral surgery group and 11.45% in non-pathologic vertebral surgery group, with no significant difference. Conclusion Pathologic vertebral surgery surgery is a safe, effective and feasible method of operation for treatment of thoracic and lumbar tuberculosis, which can effectively preserve adjacent normal vertebral motion unit features. The thoracic surgery was less satisfactory than the lumbar and thoracolumbar surgery. Key words: Thoracic vertebrae; Lumbar vertebrae; Tuberculosis, spinal; Bone transplantation; Treatment outcome

BIOMECHANICAL STUDY ON ADJACENT UPPER AND LOWER AND UNILATERAL FRACTURED VERTEBRAL PEDICLE SCREW FIXATION IN TREATMENT OF THORACOLUMBAR FRACTURE

To investigate the stability of unilateral fractured vertebral pedicle screw fixation in the treatment of thoracolumbar fracture. Eighteen fresh calf thoracolumbar spine specimens (T11-L3) were obtained to establish the L1 burst fracture models with Panjabi's high speed trauma apparatus, and were divided into 3 groups:pedicle fixation for adjacent upper and lower vertebrae of fractured vertebra (4 pedicle screws in group A), combined with pedicle screw fixation for unilateral fractured vertebrae (5 pedicle screws in group B), and three-level 6 pedicle fixation (group C). Under normal, fractured, and reconstructed conditions, the range of motion (ROM) of adjacent upper and lower vertebrae of fractured vertebra were measured in flexion, extension, bilateral bending, and axial rotation. Axial stiffness under flexion-compression was measured on the MTS-858 testing system. There was no significant difference in ROM and axial stiffness under normal and fractured conditions in all directions among groups (P<0.05), indicating load balance in the groups. ROM of groups B and C were significantly less than that of group A under reconstructed condition in all directions (P<0.05), but no significant difference was found between group B and group C (P>0.05). Biomechanical test showed that group B was significantly higher than group A in the axial stiffness value (P<0.05), but difference was not significant between group B and group C (P>0.05). Transpedicular fixation of fractured vertebrae can enhance the stability of the spine. Both unilateral and bilateral fractured vertebral pedicle screw fixations have the same stability.

Mini Anterior Lumbar Interbody Fusion: One Year Follow up for a Novel Device

Introduction This study is a prospective cohort observational trial, to evaluate the ROI-A (Radiolucent Open Implant-ALIF) and VerteBRIDGE plate construct, in the treatment of symptomatic lumbar degenerative disc disease. The principal advantage of anterior approach is that the risks associated with exploration of the spinal canal through a posterior approach can be avoided and damage to the muscles of the back is eliminated. The anterior approach offers superior visualization of the disc space itself, and can be done without disruption of the otherwise healthy posterior elements. The Mini ALIF retroperitoneal approach facilitates rapid patient recovery. Materials and Methods The ROI-A (Radiolucent Open Implant-ALIF) is made from PEEK (Polyetheretherketone), a medical grade plastic, and two metallic anchoring plates, marketed as VerteBridge, which provide both stability at the site of desired bony fusion and fixation of the implant to the vertebrae adjacent to the interbody device. Inclusion Criteria: 18 patients between the ages 31 and 65 years of age; Disc disease between L2-S1; Patients may have up to grade I spondylolisthesis or retrolesthesis at the involved site; Maximum two diseased vertebral motion segments to be instrumented; Has had no more than two previous non-fusion surgeries to the lumbar soine at the same level(s); Has failed to respond to an appropriate attempt at conservative treatment. Exclusion Criteria: More than two vertebral motion segments involved; Prior anterior, retroperitoneal approach; Has had previous anterior instrumented fusion at the proposed operative level; Higher than grade I spondylolisthesis or retrolisthesis at the involved level(s); Has reported active malignancy, localized or systemic infection; Morbid obesity, as defined by NIH Clinical Guidelines Body Mass Index (BMI &gt; 40); Patients with a diagnosis of osteoporosis, osteopenia, Paget's or other metabolic bone disease; Patients who smoke more than 1 pack per day; Has an active workers compensation claim relative to the involved part. Outcome Measures: Subjects are evaluated clinically pre-operatively, 6 weeks and 12 months post op by the pain questionnaire (VAS), and function questionnaire (ODI); The radiological measures included the segmental lordosis, integrity of the construct, and presence of bridging bone; Fusion success is defined as presence of bridging bone, and postoperative intervertebral motion at 12 months which is less than 5 degrees, via manual radiographic angular measurements (Cobb Method) of the implanted level(s) on flexion and extension radiographs at the 12 month follow up visit. Results The VAS has improved from an average of 9 preop to an average of 2 postop. ODI score has reduced an average 30 points from preop measurement. 83% (15 patients) went on bony fusion at the radiological assessment 12 month post op. None of the patients underwent revision, removal of implant, supplemented fixation, or re-operation. One patient developed mechanical ileus for 48 hours postop, resolved with NG tube. Conclusion Mini anterior inter-body fusion is a valid option when treating degenerative/discogenic back pain, the ROI-A implant is a safe and simple, with satisfactory results up to 12 month, according to our pilot study.

The effect of disc degeneration on anterior shear translation in the lumbar spine: Still more problems lie ahead

Letter to Dr. Linda Sandell: Low back pain is the single most common cause for disability in individuals aged 45 years or younger and as a result carries tremendous weight in socioeconomic considerations. Undoubtedly, numerous factors are contributed to low back pain; mechanical causes of low back pain include degenerative spinal pathologies such as spondylolisthesis, disc herniation, discogenic pain, and so on. Although the study by Melnyk et al.1 has dramatically improved our knowledge about the effect of disc degeneration on anterior translation of the lumbar spine under shear loading, we do not completely agree with the conclusion indicating that disc degeneration, as classified with the Pfirrmann scale, does not predict lumbar spinal motion in shear. First, recent biomechanical studies have revealed distinct behavior at the different lumbar levels2; and the study of lumbar intervertebral disc morphology using MR images has shown segment-dependent geometric features.3 Moreover, different clinical outcomes following surgical treatment at the different lumbar levels have been reported.4 Various factors could influence segment-dependent function of the lumbar spine, such as the surrounding ligaments and muscles, vertebral geometries, the orientation of facet joints, and so on. Notably, the segment-dependent discrepancy may be an inherent factor on the effect of disc degeneration on anterior translation of the lumbar spine under shear loading, which specifically compared at different segment levels are necessary. Further, lumbar disc degeneration is found most often at the L5-S1 level.5 We believe that the study by Melnyk et al.1 has some important limitations. For example, the study only investigated the L3-4 and L4-5 levels that they did not take the other lumbar levels into account, especially the L5-S1 level. Finally, the in-vitro study applied shear loading conditions could be quite different from in-vivo shear loading conditions, which the surrounding ligaments and muscles are not considered. In addition, the in-vivo studies have reported that different abnormal vertebral motions are closely associated with different lumbar disc degenerations graded by Pfirrmann's criteria.6 The conclusion of Melnyk et al.1 may mislead the surgeons on the operative treatment options of lumbar disc degeneration. In the end, we unanimously applaud Melnyk et al. for their significant work and the diligence with which they handled this controversial topic. Currently, it is still more problems waiting to be solved. Therefore, substantial work to determine the effect of disc degeneration on anterior translation of the lumbar spine under shear loading is essential in the near future. YS made substantial contributions to manuscript drafting and approval. DP made substantial contributions to revising the manuscript critically for important intellectual content and approval. ZD made substantial contributions to manuscript revision and approval. WZ made substantial contributions to Conception and design of the manuscript; manuscript revision and approval for the final version submitted. Yi Shen, Dan Peng, Zhihui Dai, Weiye Zhong Department of Orthopaedic Surgery Second Xiangya Hospital and Central South University 139 Middle Renmin Road, Changsha, Hunan 410011, P.R. China

Dimensions of the cervical neural foramen in conditions of spinal deformity: an ex vivo biomechanical investigation using specimen-specific CT imaging.

Patients with cervical spondylosis commonly present with neck pain, radiculopathy or myelopathy. As degenerative changes progress, multiple factors including disc height loss, thoracic kyphosis, and facetogenic changes can increase the risk of neural structure compression. This study investigated the impact of cervical deformity including forward head posture (FHP) and upper thoracic kyphosis, on the anatomy of the cervical neural foramen. Postural changes of 13 human cervical spine specimens (Occiput-T1, age 50.6years; range 21-67) were assessed in response to prescribed cervical sagittal malalignments using a previously reported experimental model. Two characteristics of cervical sagittal deformities, C2-C7 sagittal vertical alignment (SVA) and sagittal angle of the T1 vertebra (T1 tilt), were varied to create various cervical malalignments. The postural changes were documented by measuring vertebral positions and orientations. The vertebral motion data were combined with specimen-specific CT-based anatomical models, which allowed assessments of foraminal areas of subaxial cervical segments as a function of increasing C2-C7 SVA and changing T1 tilt. Increasing C2-C7 SVA from neutral posture resulted in increased neural foraminal area in the lower cervical spine (largest increase at C4-C5: 13.8±15.7%, P<0.01). Increasing SVA from a hyperkyphotic posture (greater T1 tilt) also increased the neural foraminal area in the lower cervical segments (C5-C6 demonstrated the largest increase: 13.4±9.6%, P<0.01). The area of the cervical neural foramen decreased with increasing T1 tilt, with greater reduction occurring in the lower cervical spine, specifically at C5-C6 (-8.6±7.0%, P<0.01) and C6-C7 (-9.6±5.6%, P<0.01). An increase in thoracic kyphosis (T1 tilt) decreased cervical neural foraminal areas. In contrast, an increase in cervical SVA increased the lower cervical neural foraminal areas. Patients with increased upper thoracic kyphosis may respond with increased cervical SVA as a compensatory mechanism to increase their lower cervical neural foraminal area.

Transient pressure changes in the vertebral canal during whiplash motion – A hydrodynamic modeling approach

In vehicle collisions, the occupant׳s torso is accelerated in a given direction while the unsupported head tends to lag behind. This mechanism results in whiplash motion to the neck. In whiplash experiments conducted for animals, pressure transients have been recorded in the spinal canal. It was hypothesized that the transients caused dorsal root ganglion dysfunction. Neck motion introduces volume changes inside the vertebral canal. The changes require an adaptation which is likely achieved by redistribution of blood volume in the internal vertebral venous plexus (IVVP). Pressure transients then arise from the rapid redistribution. The present study aimed to explore the hypothesis theoretically and analytically. Further, the objectives were to quantify the effect of the neck motion on the pressure generation and to identify the physical factors involved. We developed a hydrodynamic system of tubes that represent the IVVP and its lateral intervertebral vein connections. An analytical model was developed for an anatomical geometrical relation that the venous blood volume changes with respect to the vertebral angular displacement. This model was adopted in the hydrodynamic tube system so that the system can predict the pressure transients on the basis of the neck vertebral motion data from a whiplash experiment. The predicted pressure transients were in good agreement with the earlier experimental data. A parametric study was conducted and showed that the system can be used to assess the influences of anatomical geometrical properties and vehicle collision severity on the pressure generation.

Variability in Flexion Extension Radiographs of the Lumbar Spine: A Comparison of Uncontrolled and Controlled Bending.

While low back pain is one of the most prevalent, if not the most prevalent reasons for visits to physicians, a majority of patients with low back pain cannot be given a definitive diagnosis. While there have been substantial advances in imaging technologies over the past 30 years, relatively little has changed in the methodologies for evaluating functionality of the lumbar spine. The current standard of care for function assessment of the lumbar spine focuses on uncontrolled patient directed motion which results in increased inter-patient variability. Recent advancements in functional lumbar spine testing utilize controlled bending and computerized imaging evaluation. To compare the measurement variability of lumbar spine motion when diagnosed using measurements of intervertebral motion taken from standard bending flexion/extension radiographs (FE) between uncontrolled and controlled motion. One-hundred nine patients (57 asymptomatic, 52 symptomatic) were consented in the prospective investigation. The research was designed to compare studies involving FE to controlled motion bending radiographs using the Vertebral Motion Analysis (VMA), (Ortho Kinematics, Inc) within the same patient. Each patient agreed to undergo fluoroscopic still imaging to capture FE data and to undergo cine fluoroscopic imaging to capture VMA data. Measurement variability was determined by the mean and standard deviation of intervertebral rotation when evaluated by 5 independent observers evaluating each of the 109 patients FE and VMA. The resulting standard deviation of the intervertebral rotation determinations was used as the measure of variability. The VMA measurements for assessing intervertebral motion were characterized by the use of: (1) a handling device that assists patients through a standard arc of lumbar bending in both an upright and recumbent posture (70 degree flexion/extension arcs; 60 degree left/right bending arcs); (2) video fluoroscopy imaging of the lumbar spine during bending (capturing images at 8 frames per second); and (3) image processing software capable of automatic frame-to-frame registration and tracking of vertebral bodies across the sequence of video-fluoroscopic images to derive measurements of intervertebral rotation and translation. The FE data were assessed from voluntary bending by the patient. There was statistical greater measurement variability in intervertebral rotation in FE when compared to VMA (both standing and lying). When comparing measurement variability between FE and VMA, results indicate between a 26% to 46% decrease in measurement variability under VMA compared to FE. These findings are consistent across asymptomatic and symptomatic patients. The current standard of care for functional testing of the lumbar spine utilizes uncontrolled FE with a manual data evaluation process. Recent developments in using computerized imaging processes has improved, however there remains variability in patient bending due to the self-selected rate and position of the bending. VMA results in a significant reduction in measurement variability of intervertebral rotation measurements.

Dimensional changes of the neuroforamina in subaxial cervical spine during in vivo dynamic flexion-extension

Background ContextNeuroforaminal stenosis is one of the key factors causing clinical symptoms in patients with cervical radiculopathy. Previous quantitative studies on the neuroforaminal dimensions have focused on measurements in a static position. Little is known about dimensional changes of the neuroforamina in the cervical spine during functional dynamic neck motion under physiological loading conditions. PurposeThis study aimed to investigate the in vivo dimensional changes of the neuroforamina in human cervical spine (C3–C7) during dynamic flexion-extension neck motion. Study DesignA case-control study was carried out. MethodsTen asymptomatic subjects were recruited for this study. The cervical spine of each subject underwent magnetic resonance image scanning for construction of three-dimensional (3-D) vertebrae models from C3 to C7. The cervical spine was then imaged using a dual fluoroscopic system while the subject performed a dynamic flexion-extension neck motion in a sitting position. The 3-D vertebral models and the fluoroscopic images were used to reproduce the in vivo vertebral motion. The dimensions (area, height, and width) were measured for each cervical neuroforamen (C3/C4, C4/C5, C5/C6, and C6/C7) in the following functional positions: neutral position, maximal flexion, and maximal extension. Repeated measures analysis of variance and post hoc analysis were used to examine the differences between levels and positions. ResultsCompared with the neutral position, almost all dimensional parameters (area, height, and width) of the subaxial cervical neuroforamina decreased in extension and increased in flexion, except the neuroforaminal area at C5/C6 (p=.07), and the neuroforaminal height at C6/C7 (p=.05) remained relatively constant from neutral to extension. When comparisons of the overall change fromextension to flexion were made between segments, the overall changes of the neuroforaminal area and height revealed no significant differences between segments, and the width overall change of the upper levels (C3/C4 and C4/C5) was significantly greater than the lower levels (C5/C6 and C6/C7) (p<.01). ConclusionsThe dimensional changes of the cervical neuroforamina showed segment-dependent characteristics during the dynamic flexion-extension. These data may have implications for diagnosis and treatment of patients with cervical radiculopathy.

Morphological and functional changes in the vertebral column with increasing aquatic adaptation in crocodylomorphs.

The lineage leading to modern Crocodylia has undergone dramatic evolutionary changes in morphology, ecology and locomotion over the past 200+ Myr. These functional innovations may be explained in part by morphological changes in the axial skeleton, which is an integral part of the vertebrate locomotor system. Our objective was to estimate changes in osteological range of motion (RoM) and intervertebral joint stiffness of thoracic and lumbar vertebrae with increasing aquatic adaptation in crocodylomorphs. Using three-dimensional virtual models and morphometrics, we compared the modern crocodile Crocodylus to five extinct crocodylomorphs: Terrestrisuchus, Protosuchus, Pelagosaurus, Steneosaurus and Metriorhynchus, which span the spectrum from terrestrial to fully aquatic. In Crocodylus, we also experimentally measured changes in trunk flexibility with sequential removal of osteoderms and soft tissues. Our results for the more aquatic species matched our predictions fairly well, but those for the more terrestrial early crocodylomorphs did not. A likely explanation for this lack of correspondence is the influence of other axial structures, particularly the rigid series of dorsal osteoderms in early crocodylomorphs. The most important structures for determining RoM and stiffness of the trunk in Crocodylus were different in dorsoventral versus mediolateral bending, suggesting that changes in osteoderm and rib morphology over crocodylomorph evolution would have affected movements in some directions more than others.

Моделювання дегенеративних змін у хребтових рухових сегментах поперекового відділу хребта в експериментальних тварин

Доведено, що щільність кісткової тканини тіл хребців у поперековому відділі хребта вівці, свині й теляти в чотири рази вища, ніж у людини, що вказує на значно більше навантаження на поперековий відділ хребта в цих тварин порівняно з людиною. Існуючі експериментальні роботи доводять, що переважним об’єктом для моделювання дегенеративних змін у хребті є кролі, а також дрібні лабораторні тварини — щури та миші. Використовуючи їх, можна простежити розвиток вікових дегенеративних змін у міжхребцевих дисках у відносно короткі терміни, а також вивчити зміни в розташованих краніально і каудально суміжних хребтових рухових сегментах. У статті описано спосіб відтворення дегенеративних змін LV-LVI хребтових рухових сегментів поперекового відділу хребта у кролів.

The biological basis of degenerative disc disease: proteomic and biomechanical analysis of the canine intervertebral disc.

IntroductionIn the present study, we sought to quantify and contrast the secretome and biomechanical properties of the non-chondrodystrophic (NCD) and chondrodystrophic (CD) canine intervertebral disc (IVD) nucleus pulposus (NP).MethodsWe used iTRAQ proteomic methods to quantify the secretome of both CD and NCD NP. Differential levels of proteins detected were further verified using immunohistochemistry, Western blotting, and proteoglycan extraction in order to evaluate the integrity of the small leucine-rich proteoglycans (SLRPs) decorin and biglycan. Additionally, we used robotic biomechanical testing to evaluate the biomechanical properties of spinal motion segments from both CD and NCD canines.ResultsWe detected differential levels of decorin, biglycan, and fibronectin, as well as of other important extracellular matrix (ECM)-related proteins, such as fibromodulin and HAPLN1 in the IVD NP obtained from CD canines compared with NCD canines. The core proteins of the vital SLRPs decorin and biglycan were fragmented in CD NP but were intact in the NP of the NCD animals. CD and NCD vertebral motion segments demonstrated significant differences, with the CD segments having less stiffness and a more varied range of motion.ConclusionsThe CD NP recapitulates key elements of human degenerative disc disease. Our data suggest that at least some of the compromised biomechanical properties of the degenerative disc arise from fibrocartilaginous metaplasia of the NP secondary to fragmentation of SLRP core proteins and associated degenerative changes affecting the ECM. This study demonstrates that the degenerative changes that naturally occur within the CD NP make this animal a valuable animal model with which to study IVD degeneration and potential biological therapeutics.Electronic supplementary materialThe online version of this article (doi:10.1186/s13075-015-0733-z) contains supplementary material, which is available to authorized users.

Apportionment of lumbar L2–S1 rotation across individual motion segments during a dynamic lifting task

Segmental apportionment of lumbar (L2–S1) rotation is a critical input parameter for musculoskeletal models and a candidate metric for clinical assessment of spinal health, but such data are sparse. This paper aims to quantify the time-variant and load-dependent characteristics of intervertebral contributions to L2–S1 extension during a dynamic lifting task. Eleven healthy participants lifted multiple weights (4.5, 9.1, and 13.6kg) from a trunk-flexed to an upright position while being imaged by a dynamic stereo X-ray system at 30frames/s. Vertebral (L2–S1) motion was tracked using a previously validated volumetric model-based tracking method that employs 3D bone models reconstructed from subject-specific CT images to obtain high-accuracy (≤0.26°, 0.2mm) 3D vertebral kinematics. Individual intervertebral motions as percentages of the total L2–S1 extension were computed at each % increment of the motion to show the segmental apportionment. Results showed L3–L4 (25.8±2.2%) and L4–L5 (31±3.1%) together contributed a larger share (∼60% combined) compared to L2–L3 (21.7±3.7%) and L5–S1 (22.6±4.7%); L4–L5 consistently provided the largest contribution of the measured segments. Relative changes over time in L3–L4 (6±12.5%) and L4–L5 (0.5±10.2%) contribution were minimal; in contrast, L2–L3 (18±20.1%) contribution increased while L5–S1 (−33±22.9%) contribution decreased in a somewhat complementary fashion as motion progressed. No significant effect of the magnitude of load lifted on individual segmental contribution patterns was detected. The current study updated the knowledge regarding apportionment of lumbar (L2–S1) motion among individual segments, serving both as input into musculoskeletal models and as potential biomechanical markers of low back disorders.