Intervertebral Motion Research Articles

Physical therapist clinical reasoning and classification inconsistencies in headache disorders: a United States survey

ABSTRACTObjective: The purpose of this study was to investigate the decision-making processes of physical therapists relating to evaluation and categorization of patients with headaches, including consistency with criteria proposed by the International Headache Society (IHS).Methods: A national online survey was distributed in cooperation with the Academy of Orthopaedic Physical Therapy of the American Physical Therapy Association. Three hypothetical patient case vignettes featuring headache disorders were used as assessment instruments. Additionally, data on physical therapist education, clinical experience, manual therapy training, self-efficacy, and familiarity & consistency with IHS criteria were collected. Physical therapist identification and valuation of clinical features of headache disorders were also examined in the decision-making processes.Results: Among the 384 respondents, 32.3% classified the tension-type headache case consistent with IHS criteria. The cervicogenic and migraine headache cases were classified at 54.8% and 41.7% consistent with IHS categories, respectively. Experienced clinicians and those with formal manual training categorized patient presentations with greater consistency. Clinician familiarity with IHS classification criteria was low with 73.6% collectively somewhat and not familiar, while 26.4% of physical therapists were self-described as very or moderately familiar.Discussion: Clinicians’ headache categorization was significantly affected by symptom misattribution and weighting of individual examination findings. Weighting by practitioners of clinical features varied markedly with greatest emphasis being placed on detailed manual examination procedures, including passive intervertebral movements. Inconsistencies in valuation of clinical features in headache categorization suggest a need for further formal education in physical therapy educational curricula and in post-graduate education, including of IHS criteria and classification.Level of Evidence: 2a

A comparative analysis of intensity-based 2D-3D registration for intraoperative use in pedicle screw insertion surgeries.

Although multiple algorithms have been reported that focus on improving the accuracy of 2D-3D registration techniques, there has been relatively little attention paid to quantifying their capture range. In this paper, we analyze the capture range for a number of variant formulations of the 2D-3D registration problem in the context of pedicle screw insertion surgery. We tested twelve 2D-3D registration techniques for capture range under different clinically realistic conditions. A registration was considered as successful if its error was less than 2mm and 2° in 95% of the cases. We assessed the sensitivity of capture range to a variety of clinically realistic parameters including: X-ray contrast, number and configuration of X-rays, presence or absence of implants in the image, inter-subject variability, intervertebral motion and single-level vs multi-level registration. Gradient correlation + Powell optimizer had the widest capture range and the least sensitivity to X-ray contrast. The combination of 4 AP + lateral X-rays had the widest capture range (725mm2). The presence of implant projections significantly reduced the registration capture range (up to 84%). Different spine shapes resulted in minor variations in registration capture range (SD 78mm2). Intervertebral angulations of less than 1.5° had modest effects on the capture range. This paper assessed capture range of a number of variants of intensity-based 2D-3D registration algorithms in clinically realistic situations (for the use in pedicle screw insertion surgery). We conclude that a registration approach based on the gradient correlation similarity and the Powell's optimization algorithm, using a minimum of two C-arm images, is likely sufficiently robust for the proposed application.

Assessment of In Vivo Lumbar Inter-Vertebral Motion: Reliability of a Novel Dynamic Weight-Bearing Magnetic Resonance Imaging Technique Using a Side-Bending Task.

Study DesignBetween-session reliability of a magnetic resonance imaging (MRI) based experimental technique to quantify lumbar inter-vertebral motion in humans.PurposeWe have developed a novel, dynamic, MRI-based approach for quantifying in vivo lumbar inter-vertebral motion. In this study, we present the protocol’s reliability results to quantify inter-vertebral spine motion.Overview of LiteratureMorphometric studies on intervertebral displacements using static, supine MRI and quantification of dynamic spine motion using different X-ray based radiography techniques are commonly found in the literature. However, reliability testing of techniques assessing real-time lumbar intervertebral motion using weight-bearing MRI has rarely been reported.MethodsTen adults without a history of back pain performed a side-bending task on two separate occasions, inside an open-MRI, in a weight-bearing, upright position. The images were acquired during the task using a dynamic magnetic resonance (MR) sequence. The MRI imaging space was externally calibrated before the study to recreate the imaging volume for subsequent use in an animation software. The dynamic MR images were processed to create side-bending movement animations in the virtual environment. Participant-specific three-dimensional models were manually superimposed over vertebral image silhouettes in a sequence of image frames, representing the motion trials. Inter-vertebral axes and translation and rotational displacements of vertebrae were quantified using the animation software.ResultsQuantification of inter-vertebral rotations and translations shows high reliability. Between-session reliability results yielded high values for the intra-class correlation coefficient (0.86–0.93), coefficient of variation (13.3%–16.04%), and Pearson’s correlation coefficients (0.89–0.98).ConclusionsThis technique may be developed further to improve its speed and accuracy for diagnostic applications, to study in vivo spine stability, and to assess outcomes of surgical and non-surgical interventions applied to manage pathological spine motion.

Muscle That Influence the Lumar Spine, Smallest Yet Most Powerful: Lumbar Multifidus

It is well known that the lumbar multifidus muscle helps to stabilize and control of the lumbar spine. Some studies indicate a role of this muscle in spinal stiffness and control of intervertebral motion, particularly in the sagittal and frontal planes. Because the deep and superficial fibers of the multifidus are near the center of lumbar joint rotation, the superficial fibers are help to control spine orientation and the deep fibers helps to control intervertebral movement. If ligaments are insufficient than spinal movement is controlled by activity of multifidus.

Intrasubject repeatability of in vivo intervertebral motion parameters using quantitative fluoroscopy

PurposeIn vivo quantification of intervertebral motion through imaging has progressed to a point where biomarkers for low back pain are emerging. This makes possible deeper study of the condition’s biometrics. However, the measurement of change over time involves error. The purpose of this prospective investigation is to determine the intrasubject repeatability of six in vivo intervertebral motion parameters using quantitative fluoroscopy.MethodsIntrasubject reliability (ICC) and minimal detectable change (MDC) of baseline to 6-week follow-up measurements were calculated for six lumbar spine intervertebral motion parameters in 109 healthy volunteers. A standardised quantitative fluoroscopy (QF) protocol was used to provide measurements in the coronal and sagittal planes using both passive recumbent and active weight-bearing motion. Parameters were: intervertebral range of motion (IV-RoM), laxity, motion sharing inequality (MSI), motion sharing variability (MSV), flexion translation and anterior disc height change during flexion.ResultsThe best overall intrasubject reliability (ICC) and agreement (MDC) were for disc height (ICC 0.89, MDC 43%) and IV-RoM (ICC 0.96, MDC 60%), and the worst for MSV (ICC 0.04, MDC 408%). Laxity, MSI and translation had acceptable reliability (most ICCs > 0.60), but not agreement (MDC > 85%).ConclusionDisc height and IV-RoM measurement using QF could be considered for randomised trials, while laxity, MSI and translation could be considered for moderators, correlates or mediators of patient-reported outcomes. MSV had both poor reliability and agreement over 6 weeks.Graphical abstractThese slides can be retrieved under Electronic Supplementary Material.

The effect of axial compression and distraction on cervical facet mechanics during anterior shear, flexion, axial rotation, and lateral bending motions

The subaxial cervical facets are important load-bearing structures, yet little is known about their mechanical response during physiological or traumatic intervertebral motion. Facet loading likely increases when intervertebral motions are superimposed with axial compression forces, increasing the risk of facet fracture. The aim of this study was to measure the mechanical response of the facets when intervertebral axial compression or distraction is superimposed on constrained, non-destructive shear, bending and rotation motions. Twelve C6/C7 motion segments (70 ± 13 yr, nine male) were subjected to constrained quasi-static anterior shear (1 mm), axial rotation (4°), flexion (10°), and lateral bending (5°) motions. Each motion was superimposed with three axial conditions: (1) 50 N compression; (2) 300 N compression (simulating neck muscle contraction); and, (3) 2.5 mm distraction. Angular deflections, and principal and shear surface strains, of the bilateral C6 inferior facets were calculated from motion-capture data and rosette strain gauges, respectively. Linear mixed-effects models (α = 0.05) assessed the effect of axial condition. Minimum principal and maximum shear strains were largest in the compressed condition for all motions except for maximum principal strains during axial rotation. For right axial rotation, maximum principal strains were larger for the contralateral facets, and minimum principal strains were larger for the left facets, regardless of axial condition. Sagittal deflections were largest in the compressed conditions during anterior shear and lateral bending motions, when adjusted for facet side.

Relationships between muscle electrical activity and the control of inter-vertebral motion during a forward bending task

Muscle strengthening exercises are commonly used in primary care for the treatment of chronic, non-specific low back pain (CNSLBP) as it has been theorised that increased muscle activity contributes to the stabilisation of inter-vertebral motion segments during bending and other spinal movements, however this has never been demonstrated in vivo.This study used contemporaneous quantitative fluoroscopy (QF) and surface electromyography (sEMG) to investigate relationships between continuous inter-vertebral motion variables and muscle electrical activity in the lumbar multifidus (LMU), lumbar and thoracic erector spinae (LES and TES) during standardised lumbar flexion and return in 18 healthy male human subjects.Our results demonstrated that the variability in the sharing of angular motion (i.e. Motion Share Variability MSV) and motion segment laxity during a bending task were significantly (p < 0.05) negatively correlated (Spearman) with muscle electrical activity throughout the participant bend for both locally and globally acting muscle groups. MSV was also strongly correlated with L2-3 laxity.The former suggests a damping mechanism reducing irregular displacements (i.e. less variability in the sharing of segmental motion) during bending and an action of spinal stabilisation by muscles at segmental levels, and the latter a synergy between laxity at L2-3 and MSV. While this has previously been theorised, it has never been shown in vivo at the inter-vertebral level. These assessments may be considered for use in validation studies of exercise programs for CNSLBP, however further replication is required.

Chromium and Nickel Concentrations in Subjects with a Stainless Steel Metal-on-Metal Cervical Disc Arthroplasty: Results from a Prospective Longitudinal Study with 7 Years Follow-Up.

Cervical disc arthroplasty (CDA) has emerged as an alternative to anterior cervical discectomy and fusion for degenerative cervical disc disease. The artificial discs provide intervertebral motion using multicomponent articulation and thus tend to generate particulate debris and soluble metal ions. Limited information is available on the long-term metal concentrations and associated systemic adverse events observed in metal-on-metal CDA. Serum chromium (Cr) and nickel (Ni) concentrations were assessed in patients implanted with ball-in-trough stainless steel-based cervical disc through 7 years. A prospective, nonrandomized longitudinal study was conducted that included 25 patients following rigorous exclusion criteria that included no previous permanent metal implants and no professional exposure to metal particles. Blood serum Cr and Ni concentrations were assayed preoperatively and at 3, 6, 12, 24, 36, 60, and 84 months postoperatively using high-resolution inductively coupled plasma-mass spectrometry. Longitudinal statistical comparisons were made using the Friedman test with statistical significance at P < .05. Median serum concentrations determined preoperatively and at 3, 6, 12, 24, 36, 60, and 84 months postoperatively were 0.074, 0.106, 0.132, 0.170, 0.172, 0.274, 0.192, and 0.203 ng/mL for Cr and 0.085, 0.178, 0.222, 0.175, 0.205, 0.284, 0.181, and 0.194 ng/mL for Ni. The serum Cr concentrations were statistically higher for all postoperative time periods compared to preoperative concentration (Friedman P <.01), whereas serum Ni concentration was statistically higher at the 84-month postoperative time period than the preoperative concentration (Friedman P <.01) and then the concentration at 3, 12, 24, and 60 months postoperatively (Friedman P < .03). The Cr concentrations detected at all postoperative times were statistically higher than preoperative concentrations, whereas Ni concentration was statistically higher than the preoperative concentration only at 84 months.

Wednesday, September 26, 2018 7:35 AM–9:00 AM ePosters: P122. Cervical interbody spacer with passive radiographic fusion status indicator

BACKGROUND CONTEXT Pseudarthrosis or nonunion of the cervical spine is the result of failed attempted fusion and is a leading cause of postoperative axial pain and radiculopathy. Reported rates of failed cervical fusion range from 4.4 to 50%, generally higher with multilevel procedures, and pseudarthrosis accounts for 45%–56% of revision surgeries. Nonunion is difficult to detect clinically and diagnosis is based solely on symptomatology (neck pain, radiculopathy) and imaging studies. The gold standard approach to define fusion status involves surgical exploration, a last resort option. Radiographic tools are commonly used first, with computed tomography (CT) considered the most reliable method. However, CT scans are expensive and expose patients to large radiation doses (hundreds of times more than standard X-ray). The status of anterior cervical fusion can also be determined using interspinous motion analysis; the goal is to detect any movement between adjacent vertebra using dynamic radiographs. This may be accomplished by measuring the distance between the tips of adjacent spinous processes on lateral flexion and extension films. However, the technique is subjective and affected by parallax, and studies have found wide interobserver differences. This makes it difficult to accurately apply the method to assess pseudarthrosis using the proposed cutoff values (1 or 2 mm). Other literature similarly suggests that current radiographic methods do not reliably provide clinical information about abnormalities of intervertebral motion. Therefore quantitative and standardized methods for defining spinal fusion or instability are needed. PURPOSE Our hypothesis is that intervertebral motion can be more accurately detected using a simple passive implantable device that responds to the pressure differential or vertebral body endplate motion within the index disc space between the flexed and extended positions of the cervical spine. Conceptually, this dynamic motion sensor could detect and potentially prevent pseudarthrosis, a leading cause of postoperative pain and radiculopathy STUDY DESIGN/SETTING This desktop and benchtop research was conducted primarily in a chemistry laboratory. Manufacturing of prototypes and other materials was performed on-site. Radiographic images were taken at a centralized animal research facility. METHODS A cervical interbody spacer with integrated fluidic pressure sensor was developed using CAD modeling software and prototyped with 3D printing. The working principal involves a fluid well and indicator channel. The spacer was placed between Sawbones vertebra analogs and loads applied to simulate dynamic spinal positions. Previous work with a similar fluidics device used a single-column compression tester to apply loads comparable to those experienced by vertebra in the cervical region. Radiographs were also taken of a device loaded with radio-dense fluid (cesium acetate) and channel diameter of 0.5mm. RESULTS Computer simulations suggested that the device would fit and function well between cervical vertebra in the flexed and extended spinal positions. Prototypes placed between cervical bone analogs under load demonstrated that the signal would be apparent clinically. Previous work showed that fluid displacement into the indicator portion was in the appropriate scale (0–6.9 mm) under applied loads in the range experienced clinically (0–110 N); this relationship was linear and repeatable. The imaging resolution of the device with a radiocontrast agent as the indicator fluid was also within the clinical range, and the signal was apparent on radiographs. CONCLUSIONS Based on these results it appears that an interbody device with fluidic sensor is potentially a viable option for assessing fusion status in the cervical spine.Prior literature gives the range of loads expected in the cervical spine (up to ≈100N). Articles describing interspinous motion analysis suggest sufficient bone growth (fusion) occurs when the distance between the tips of adjacent cervical spinous processes changes by less than 1 mm or 2 mm between flexion and extension. Our concept offers two primary advantages over existing techniques. First, the indicator channel provides a clear and distinct signal or marker that can be plainly read on radiographs, simplifying comparisons between the flexed, neutral and extended positions and enabling monitoring over time. Second, the device introduces gain proportional to the ratio of the cross-sectional areas of the fluid well and channel, providing amplification and enabling detection of smaller changes. While a priori research demonstrated that an implantable fluidic device responded appropriately under the range of applied physiologic loads, if needed additional gain could be introduced by increasing this ratio. Future work involving finite element analysis and mechanical testing is underway and ultimately a cadaveric study will be conducted to verify the loads and characterize the device in vitro.Limitations of this work include the material choice as all prototypes were created using 3D printing. The flexural modulus of the material is important, and the device may potentially be formed with polycarbonate urethane, a stiffer and tougher flexible material commonly used in cervical disc replacements.

Open-design collar vs. Conventional Philadelphia collar regarding user satisfaction and cervical range of motion in asymptomatic adults

Cervical collars are often prescribed to minimize physiologic loads and movements between the head and thorax by limiting cervical motion; they are also used for supporting a patient's head and reducing the risk of cervical injury resulting from additional spinal movements. One of the problems in orthotic treatment is the unpleasant appearance of the orthosis, which could impede the patient from continuing treatment. Currently, it is essential to consider the importance of the psychologic effect of rehabilitative treatment. The current study aimed to compare the Philadelphia collar and an open-design cervical collar with regard to user satisfaction and cervical range of motion in asymptomatic adults. Seventy-two healthy subjects (36 women, 36 men) aged 18 to 29 years were recruited for this study. Neck movements, including active flexion, extension, right/left lateral flexion, and right/left axial rotation, were assessed in each subject under 3 conditions—without wearing a collar and while wearing 2 different cervical collars—using a dual digital inclinometer. Subject satisfaction was assessed using a 5-item self-administered questionnaire. Both Philadelphia and open-design collars significantly reduced cervical motions ( P < 0.05). Compared with the Philadelphia collar, the open-design collar more greatly reduced cervical motions in three planes and the differences were statistically significant expects for limiting flexion. Satisfaction scores for Philadelphia and open-design collars were 15.89 ± 3.87 and 19.94 ± 3.11, respectively. This study demonstrated that the open-design collar is more cosmetically acceptable as a semirigid cervical collar compared with the Philadelphia collar, at least for subjects aged under forty years, while it also has optimal restriction potential. Further studies are needed to investigate its effectiveness in restricting cervical intervertebral motion and long-term compliance.

Aberrant intervertebral motion in patients with treatment-resistant nonspecific low back pain: a retrospective cohort study and control comparison

PurposeIntervertebral kinematic assessments have been used to investigate mechanical causes when back pain is resistant to treatment, and recent studies have identified intervertebral motion markers that discriminate patients from controls. However, such patients are a heterogeneous group, some of whom have structural disruption, but the effects of this on intervertebral kinematics are unknown.MethodsThirty-seven patients with treatment-resistant back pain referred for quantitative fluoroscopy were matched to an equal number of pain-free controls for age and sex. All received passive recumbent flexion assessments for intervertebral motion sharing inequality (MSI), variability (MSV), laxity and translation. Comparisons were made between patient subgroups, between patients and controls and against normative levels from a separate group of controls.ResultsEleven patients had had surgical or interventional procedures, and ten had spondylolisthesis or pars defects. Sixteen had no disruption. Patients had significantly higher median MSI values (0.30) than controls (0.27, p = 0.010), but not MSV (patients 0.08 vs controls 0.08, p = 0.791). Patients who received invasive procedures had higher median MSI values (0.37) than those with bony defects (0.30, p = 0.018) or no disruption (0.28, p = 0.0007). Laxity and translation above reference limits were not more prevalent in patients.ConclusionPatients with treatment-resistant nonspecific back pain have greater MSI values than controls, especially if the former have received spinal surgery. However, excessive laxity, translation and MSV are not more prevalent in these patients. Thus, MSI should be investigated as a pain mechanism and for its possible value as a prognostic factor and/or target for treatment in larger patient populations.Graphical abstractThese slides can be retrieved under Electronic Supplementary Material.

Spinal PA movements behave ‘as if’ there are limitations of local segmental mobility and are large enough to be perceivable by manual palpation: A synthesis of the literature

BackgroundPosterio-anterior (PA) movements are one type of passive intervertebral movement used to assess and treat perceived deficits in localized segmental mobility. ObjectivesTo describe: 1) The specific effects that reductions in segmental mobility would be expected to have on PA movements; 2) How differences in PA movements in clinical situations compare to what would be expected with reduced segmental mobility; and 3) Whether such differences in PA movements are likely to be perceivable by manual palpation. MethodsMultiple modelling studies and in vivo measurements of PA movements are described. ResultsThe findings indicate the differences in PA movements present in clinical conditions corresponds with the differences that would be expected with decreased segmental mobility. The differences both predicted from the modelling and found in clinical conditions were greatest at low levels of force. Additionally, the differences are large enough that individuals with training are likely to be capable of 1) consistently producing controlled movements with sufficiently small magnitudes of force to assess the movements, and 2) detecting the differences in stiffness expected from modelling and found in clinical situations. ConclusionsImplications for clinical practice and teaching include the need to attend to the stiffness of PA movements at lower levels of force than those typically described. The authors recommend a three tiered approach to assessment of PA movements which may assist in both clinical practice and teaching manual therapy skills.

Mild (not severe) disc degeneration is implicated in the progression of bilateral L5 spondylolysis to spondylolisthesis

BackgroundSpondylolytic (or lytic) spondylolisthesis is often associated with disc degeneration at the index-level; however, it is not clear if disc degeneration is the cause or the consequence of lytic spondylolisthesis. The main objective of this computed tomography based finite element modelling study was to examine the role of different grades of disc degeneration in the progression of a bilateral L5-lytic defect to spondylolisthesis.MethodsHigh-resolution computed tomography data of the lumbosacral spine from an anonymised healthy male subject (26 years old) were segmented to build a 3D-computational model of an INTACT L1-S1 spine. The INTACT model was manipulated to generate four more models representing a bilateral L5-lytic defect and the following states of the L5-S1 disc: nil degeneration (NOR LYTIC), mild degeneration (M-DEG LYTIC), mild degeneration with 50% disc height collapse (M-DEG-COL LYTIC), and severe degeneration with 50% disc height collapse(S-COL LYTIC). The models were imported into a finite element modelling software for pre-processing, running nonlinear-static solves, and post-processing of the results.ResultsCompared with the baseline INTACT model, M-DEG LYTIC model experienced the greatest increase in kinematics (Fx range of motion: 73% ↑, Fx intervertebral translation: 53%↑), shear stresses in the annulus (Fx anteroposterior: 163%↑, Fx posteroanterior: 31%↑), and strain in the iliolumbar ligament (Fx: 90%↑). The S-COL LYTIC model experienced a decrease in mobility (Fx range of motion: 48%↓, Fx intervertebral translation: 69%↓) and an increase in normal stresses in the annulus (Fx Tensile: 170%↑; Fx Compressive: 397%↑). No significant difference in results was noted between M-DEG-COL LYTIC and S-COL LYTIC models.ConclusionsIn the presence of a bilateral L5 spondylolytic defect, a mildly degenerate index-level disc experienced greater intervertebral motions and shear stresses compared with a severely degenerate index-level disc in flexion and extension bending motions. Disc height collapse, with or without degenerative changes in the stiffness properties of the disc, is one of the plausible re-stabilisation mechanisms available to the L5-S1 motion segment to mitigate increased intervertebral motions and shear stresses due to a bilateral L5 lytic defect.

Analysis of reason for postoperative axial pain caused by unilaterally open-door cervical laminoplasty

To explore the reason of postoperative axial pain (PAP) complication caused by unilaterally open-door cervical laminoplasty with Centerpiece mini-plate fixations for the treatment of multilevel cervical spondylotic myelopathy(CSM). The clinical data of 79 patients with CSM who underwent unilaterally open-door cervical laminoplasty from January 2010 to December 2013 were retrospectively analyzed. There were 45 males and 34 females, aged from 48 to 75 years old with an average of (58.7±4.4) years, complicated with ossified posterior longitudinal ligament(OPLL) of 42 cases. Courses of disease were from 2.1 to 3.9 years with an average of (3.0±0.4) years. Decompression segment occurred in C₃-C₆ of 31 cases, C₃-C₇ of 9 cases, C₄-C₇ of 39 cases. The condition of PAP was record. Cervical curvature index, cervical lordosis angle, the rate of cervical instability, the motion of flexion and extension between PAP group and non-PAP group were compared preoperatively. Multivariate non-linear regression analysis was used to verify relationship between aforementioned parameters and incidence of PAP. JOA score of preoperative, postoperative 6 months and initial onset of PAP, the improvement rate of JOA score and Odom criteria at final follow-up were used to evaluate curative efficacy. All the patients were followed up from 26 to 44 months with an average of (36±9) months. Among them, 12 patients occurred PAP who receive the conservative treatment. The rate of preoperative cervical instablility of PAP group were higher than that of non-PAP group(P<0.05). Preoperative cervical instability was the only independent risk factor in predicting occurrence of PAP. There were no significant differences in cervical curvature, cervical lordosis index, the motion of flexion and extension between PAP and non-PAP group before operation. There were no significant differences in the improvement of nerve function and clinical effect between PAP and non-PAP group after operation(P>0.05). Preoperative cervical instability is prone to inducing the respectively intervertebral motion disorder and imbalance of stress redistribution, which results in PAP after cervical unilateral laminoplasty. Correct treatment of preoperative cervical instability is a key factor to prevent the occurrence of PAP after cervical laminoplasty, which would not affect long-term nerve functional recovery pronouncedly.

Biomechanical comparison of lumbar spine stability after laminectomy versus bilateral laminotomy: An experimental study in porcine model

Background: Rationality of the lumbar spine is inferable to many structures in the practical spinal unit. The alliance of lumbar spine unreliability between laminectomy and laminotomy had been clinically studied, but the corresponding in vitro biomechanical studies are very limited. We explored the hypothesis that the uprightness of the posterior complication plays a vital role on the post-operative spinal rationality in decompressive surgery. Methods: Twenty porcine lumbar spine samples had been studied. Each sample was tested as a whole & after two decompression mechanism. All posterior elements were upheld in Group I (Intact). In Group II (Bilateral laminotomy), the subservient margin of the L4 lamina and predominent margin of the L5 lamina were detached, however the L4 and L5 supraspinous ligament was upheld. Fenestrations design was made on either side. In Group III (Laminectomy) lamina and the spinous activities of lower L4 & upper L5 were detached. Ligamentum flavum & supraspinous ligaments of L4 and L5 were detached. Hydraulic machine for testing was used for the generation of an increasing moment up-to 9000 N-mm in bending of limb and extension. Intervertebral movement at the decompressive level L4 and L5 was evaluated by Extensometer. Results: In extension motion, intervertebral movement between the specimen in complete form and at two dissimilar decompression levels did not remarkably differ (P>0.05). However, In flexion motion, intervertebral movement of laminectomy specimens at the decompression level L4 and L5 was significantly more than in intact or the bilateral laminotomy specimens (P=0.392 and P = 0.0001, P =0.00001). No significance difference was established between intact and the bilateral laminotomy groups (P>0.05). Conclusion: In this experimental study we concluded that Bilateral laminotomy is a more stable surgical procedure as compared to laminectomy in the decompressive surgery of lumbar spine.

Is the Interspinous Device (Coflex) Outdated in the Treatment of Lumbar Spinal Stenosis? A Seven-Year Follow-up

Background: Coflex, a kind of dynamic interspinous spacer, has been widely used for the treatment of lumbar spinal stenosis in the past a few years. However, controversy remains as to whether dynamic interspinous spacer use is superior to traditional decompression and fusion surgery. High complication, reoperation rate, and costs with poor outcomes were also mentioned in the literature. The aim of the present study is to evaluate whether Coflex implantation following spinal decompression provided better clinical outcomes compared with traditional decompression and fusion for symptomatic lumbar spinal stenosis through midterm follow-up. Methods and findings: A total of 100 patients who were confirmed L4/5 lumbar spinal stenosis was surveyed from June 2007 to June 2010. They were randomly and equally divided into two groups: 50 cases underwent spinal decompression with Coflex implantation, and 50 cases were treated with spinal decompression with fixation and fusion. The operation time, intraoperative blood loss, ambulation time, and hospitalization days, Japanese Orthopedic Association scores, visual analogue scale scores, Oswestry disability index and SF-36 scores were compared between the two groups. The ranges of motion and the height loss at adjacent segments (L3/4 and L5/S1) were measured preoperative and postoperative, respectively. Adjacent segment degeneration at L3/4 and L5/Sl was assessed by Pfirrmann classification. Complications were also recorded. The average age was 57.6 ± 5.9 years old in Coflex implantation group and 59.0 ± 6.7 years old in fusion group, respectively. The average follow-up period was 7.12 ± 1.1 year in Coflex implantation group and 7.31 ± 1.6 year in fusion group, respectively. JOA, ODI, VAS and SF-36 scores were improved at the last follow-up in all the two groups with significant differences (P 0.05). The intervertebral heights of adjacent segments were decreased at the last follow-up and the ranges of intervertebral motions were increased in both groups. The height loss and the range of motion increase of adjacent segments were greater in fusion group than those in Coflex group with statistical significant difference (P<0.01). At the last follow-up, adjacent segment disc Pfirrmann grade progressed more obviously in fusion group compared with that in Coflex group, and there was significant difference (P<0.05) between the two groups. Conclusion: Based on the present study, it showed that Coflex implantation and fusion after spinal decompression had the same clinical outcomes and satisfaction in treatment of symptomatic lumbar spinal stenosis after 7 years follow-up. Nevertheless, Coflex implantation had the advantages of less bleeding loss, less trauma and quick recovery. Compared with fusion surgery, Coflex implantation had also advantages in maintaining intervertebral height and delaying intervertebral disc degeneration of adjacent segments.

Intubation biomechanics: validation of a finite element model of cervical spine motion during endotracheal intubation in intact and injured conditions.

OBJECTIVE Because of limitations inherent to cadaver models of endotracheal intubation, the authors' group developed a finite element (FE) model of the human cervical spine and spinal cord. Their aims were to 1) compare FE model predictions of intervertebral motion during intubation with intervertebral motion measured in patients with intact cervical spines and in cadavers with spine injuries at C-2 and C3-4 and 2) estimate spinal cord strains during intubation under these conditions. METHODS The FE model was designed to replicate the properties of an intact (stable) spine in patients, C-2 injury (Type II odontoid fracture), and a severe C3-4 distractive-flexion injury from prior cadaver studies. The authors recorded the laryngoscope force values from 2 different laryngoscopes (Macintosh, high intubation force; Airtraq, low intubation force) used during the patient and cadaver intubation studies. FE-modeled motion was compared with experimentally measured motion, and corresponding cord strain values were calculated. RESULTS FE model predictions of intact intervertebral motions were comparable to motions measured in patients and in cadavers at occiput-C2. In intact subaxial segments, the FE model more closely predicted patient intervertebral motions than did cadavers. With C-2 injury, FE-predicted motions did not differ from cadaver measurements. With C3-4 injury, however, the FE model predicted greater motions than were measured in cadavers. FE model cord strains during intubation were greater for the Macintosh laryngoscope than the Airtraq laryngoscope but were comparable among the 3 conditions (intact, C-2 injury, and C3-4 injury). CONCLUSIONS The FE model is comparable to patients and cadaver models in estimating occiput-C2 motion during intubation in both intact and injured conditions. The FE model may be superior to cadavers in predicting motions of subaxial segments in intact and injured conditions.

Restriction of Cervical Intervertebral Movement With Different Types of External Immobilizers: A Cadaveric 3D Analysis Study.

Cadaveric radiostereometric analysis study. To quantify the ability of five commonly used immobilizers to restrict cervical spine movement, including intervertebral movement, in three directions. Evidence about the ability of many clinically used cervical immobilizers to restrict cervical movement is limited. Furthermore, their effect on intervertebral movement is unknown. Radiographic inert beads were implanted in the cervical vertebral bodies of five fresh-frozen human cadavers. After application of different immobilizers (Stifneck, Sternal Occipital Mandibular Immobilizer (SOMI), halo-traction, spineboard, halo-vest) and controlled flexion-extension, lateral bending, and rotation torques, radiostereometric analysis was used to determine the overall and intervertebral three-dimensional movement of each vertebral level. Restriction of cervical movement was described as a mean restriction percentage (MRP) and classified on an arbitrary basis (poor: <20%, fair: 20%-40%, moderate: 40%-60%, substantial: 60%-80%, nearly complete: >80%). Most of the restriction of flexion/extension was observed at C0-C1, while most rotational restriction was seen at C1-C2. Lateral bending was restricted at C1 to C7.The Stifneck provided the least immobilization with a moderate restriction of flexion-extension (MRP: 41%, SD: 14%), fair restriction of lateral bending (MRP: 29%, SD: 13%), and substantial restriction of rotation (MRP: 64%, SD: 15%). The halo-vest was the most restrictive immobilizer and reduced movement of the cervical spine substantially for flexion-extension (MRP: 70%, SD: 11%), substantially for lateral bending (MRP: 77%, SD: 14%), and nearly complete for rotation (MRP: 92%, SD: 3%). The restriction of movement from lowest to highest was: Stifneck, SOMI, halo-traction, head blocks on a spine board, and halo-vest. Notably, the standard deviations of the restrictions were smaller for the cranio-thoracic devices than for the cervico thoracic devices. With this new knowledge of external immobilizers and their ability to restrict intervertebral cervical movement, their indication and application in clinical practice can be improved for all patients with (suspected) cervical injury. N/A.

Kinematics of the Cervical Spine After Unilateral Facet Fracture: An In Vitro Cadaver Study.

Biomechanical study utilizing human cadaveric cervical spines. To quantitatively assess the effects on intervertebral motion of isolated unilateral cervical facet fracture, and after disruption of the intervertebral disc at the same level. Clinical evidence has indirectly suggested that cervical facet fractures involving 40% of the height of the lateral mass can cause instability of the involved segment. No study to date has demonstrated the kinematic effects of such an injury in a cadaveric model of the cervical spine. Nine six-segment cervical spines were defrosted and fixated to a spine motion simulator capable to apply unconstrained bending moments in the three anatomical planes. The spines were subjected to a maximum torque of 2 N · m in flexion, extension, left and right lateral bending, and of 4 N · m in left and right axial rotation. Each spine was tested in the intact configuration (INTACT), and following two increasing degrees of injury at C4-C5: fracture of the facet (CF1), and CF1 with disruption of the intervertebral disc at the same level (CF2). Intervertebral kinematics was tracked via clusters of active markers fixated on each vertebra. Differences in kinematics between INTACT and the two injured configurations were assessed via one-way Analysis of Variance (P < 0.05). No significant differences were detected between INTACT and CF1 across all kinematic parameters (P > 0.05) at C4-C5. CF2, however, resulted in significant increase of flexion, left axial rotation, and left lateral bending with respect to INTACT (flexion at C4-C5: INTACT = 8.7° ± 3.5°; CF2 = 14.3 ± 5.7; P < 0.05). Our findings suggest that superior articular facet fractures alone involving 40% of the lateral mass may not necessarily result in intervertebral instability under physiologic loading conditions. The addition of partial injury to the intervertebral disc, however, resulted in statistically significant increase in angular displacement. N /A.

Lumbar subtotal corpectomy non-fusion model produced using a novel prosthesis.

In this study, we aimed to design a movable artificial lumbar complex (MALC) prosthesis for non-fusion reconstruction after lumbar subtotal corpectomy and to establish an in vitro anterolateral lumbar corpectomy non-fusion model for evaluating the biomechanical stability, preservation of segment movements and influence on adjacent inter-vertebral movements of this prosthesis. Imaging was performed on a total of 26 fresh goat lumbar spine specimens to determine which of the specimens did not meet the requirements (free of deformity and fractures); the residual specimens were randomly divided into an intact group, a fusion group and a non-fusion group. Bone mineral density (BMD) was tested and compared among the three groups. Biomechanical testing was conducted to obtain the range of motion (ROM) in flexion-extension, lateral bending at L2-3, L3-4 and L4-5 and axial rotation at L2-5 in the three groups. Two specimens were excluded due to vertebral fractures. BMD showed no statistical significance among three groups (P>0.05). The stability of the prosthesis did not differ significantly during flexion, extension, and lateral bending at L2-3, L3-4, and L4-5 and axial torsion at L2-5 between the intact group and the non-fusion group (P>0.05). Segment movements of the specimens in the non-fusion group revealed significantly decreased L2-3 ROM and significantly increased L3-4 and L4-5 ROM in flexion and lateral bending compared with the fusion group (P<0.05). Reconstruction with a MALC prosthesis after lumbar subtotal corpectomy not only produced instant stability but also effectively preserved segment movements, without any abnormal gain of mobility in adjacent inter-vertebral spaces. However, additional studies, including in vivo animal experiments as well as biocompatibility and biomechanical tests of human body specimens are needed.