Stephen P. Kingwell

Factors affecting neurological outcome in traumatic conus medullaris and cauda equina injuries

The purpose of this review was to describe the relevant factors that influence neurological outcomes in patients who sustain traumatic conus medullaris injuries (CMIs) and cauda equina injuries (CEIs). Despite the propensity for spinal trauma to affect the thoracolumbar spine, few studies have adequately characterized the outcomes of CMIs and CEIs. Typically the level of neural axis injury is inferred from the spinal level of injury or the presenting neurological picture because no study from the spinal literature has specifically evaluated the location of the conus medullaris with respect to the level of greatest canal compromise. Furthermore, the conus medullaris is known to have a small but important variable location based on the spinal level. Patients with a CMI will typically present with variable lowerextremity weakness, absent lower-limb reflexes, and saddle anesthesia. The development of a mixed upper motor neuron and lower motor neuron syndrome may occur in patients with CMIs, whereas a CEI is a pure lower motor neuron injury. Many treatment options exist and should be individualized. Posterior decompression and stabilization offers at least equivalent neurological outcomes as nonoperative or anterior approaches and has the additional benefits of surgeon familiarity, shorter hospital stays, earlier rehabilitation, and ease of nursing care. Overall, CEIs and CMIs have similar outcomes, which include ambulatory motor function and a variable persistence of bowel, bladder, and potentially sexual dysfunctions.

Relationship of Neural Axis Level of Injury to Motor Recovery and Health-Related Quality of Life in Patients with a Thoracolumbar Spinal Injury

BACKGROUND Outcomes following traumatic conus medullaris and cauda equina injuries are typically predicted on the basis of the vertebral level of injury. This may be misleading as it is based on the assumption that the conus medullaris terminates at L1 despite its variable location. Our primary objective was to determine whether the neural axis level of injury (the spinal cord, conus medullaris, or cauda equina) as determined with magnetic resonance imaging is better than the vertebral level of injury for prediction of motor improvement in patients with a neurological deficit secondary to a thoracolumbar spinal injury. METHODS Patients diagnosed with a motor deficit secondary to a thoracolumbar spinal injury, and who met the inclusion criteria, were contacted. Each patient had a magnetic resonance imaging scan that was reviewed by a spine surgeon and a neuroradiologist to determine the termination of the conus medullaris and the neural axis level of injury. Patient demographic data were collected prospectively at the time of admission. Admission and follow-up neurological assessments were performed by formally trained dedicated spine physiotherapists. RESULTS Fifty-one patients were evaluated at a median of 6.2 years (range, 2.7 to 12.3 years) postinjury. The final motor scores differed significantly according to whether the patient had a spinal cord injury (mean, 62.8 points; 95% confidence interval, 55.4 to 70.2), conus medullaris injury (mean, 78.6 points; 95% confidence interval, 70.3 to 86.9), or cauda equina injury (mean, 88.8 points; 95% confidence interval, 78.9 to 98.7) (p = 0.0007). A univariate analysis showed the improvement in the motor scores after the cauda equina injuries (mean, 17.1 points; 95% confidence interval, 8.3 to 25.9) to be significantly greater than that after the spinal cord injuries (mean, 7.7 points; 95% confidence interval, 3.1 to 12.3) (p = 0.03). A multivariate analysis showed that an absence of initial sacral sensation had a negative effect on motor recovery by a factor of 13.2 points (95% confidence interval, 4.2 to 22.1). When compared with classifying our patients on the basis of the neural axis level of injury, reclassifying them on the basis of the vertebral level of injury resulted in a misclassification rate of 33%. CONCLUSIONS The motor recovery of patients with a thoracolumbar spinal injury and a neurological deficit is affected by both the neural axis level of injury as well as the initial motor score. The results of this study can help the clinician to determine a prognosis for patients who sustain these common injuries provided that he or she evaluates the precise level of neural axis injury utilizing magnetic resonance imaging.

Pediatric Noncontiguous Spinal Injuries: The 15-Year Experience at 1 Pediatric Trauma Center

Study Design. Retrospective review. Objective. To determine the incidence and clinical characteristics of noncontiguous spinal injuries (NCSI) in a pediatric population. The secondary objective is to identify high-risk patients requiring further imaging to rule out NCSI. Summary of Background Data. NCSI can add significant complexity to the diagnosis, management, and outcome of children. There is very little in the pediatric literature examining the nature, associated risk factors, management, and outcomes of NCSI. Methods. All children up to 18 years of age with a spinal injury, as defined by International Classification of Diseases, Ninth Revision codes, at one pediatric trauma hospital were included (n = 211). Data for patient demographics, mechanism of injury, spinal levels involved, extent of neurological injury and recovery, associated injuries, medical complications, treatment, and outcome were recorded. Results. Twenty-five (11.8%) of 211 patients had NCSI, with a median age of 13.0 years (interquartile range = 8–15). The most common pattern of injury was a double thoracic noncontiguous injury. Sixteen percent of the cases of NCSI were initially missed, with no clinical deterioration due to missed diagnosis. Associated injuries occurred in 44% of patients with NCSI. Twenty-four percent of patients with multiple NCSI had a neurological injury compared with 9.7% in patients with single-level or contiguous injuries (P = 0.046). Conclusion. There is a high incidence of children with multiple NCSI who are more likely to experience neurological injuries compared with patients with single-level or contiguous spinal injuries. Patients with a single-level spinal injury on existing imaging with an associated neurological injury should undergo at least plain films of the entire spine to exclude noncontiguous injuries. In patients without neurological injury and a single spinal fracture, radiography showing at least 4 levels above and below the fracture should be performed. All children with spinal injury should have associated injuries carefully excluded.

Enhancing pedicle screw fixation in the aging spine with a novel bioactive bone cement: an in vitro biomechanical study.

Study Design. A paired biomechanical study of pedicle screws augmented with bone cement in a human cadaveric and osteoporotic lumbar spine model. Objectives. To evaluate immediate strength and stiffness of pedicle screw fixation augmented with a novel bioactive bone cement in an osteoporotic spine model and compare it with polymethylmethacrylate (PMMA) cement. Summary of Background Data. A novel bioactive bone cement, containing nanoscale particles of strontium and hydroxyapatite (Sr-HA), can promote new bone formation and osteointegration and provides a promising reinforcement to the osteoporotic spine. Its immediate mechanical performance in augmenting pedicle screw fixation has not been evaluated. Methods. Two pedicle screws augmented with Sr-HA and PMMA cement were applied to each of 10 isolated cadaveric L3 vertebrae. Each screw was subjected to a toggling test and screw kinematics were calculated. The pedicle screw was subjected to a pullout test until failure. Finally, the screw coverage with cement was measured on computed tomographic images. Results. Screw translations in the toggling test were consistently larger in the Sr-HA group than in the PMMA group (1.4 ± 1.2 mm vs. 1.0 ± 1.1 mm at 1000 cycles). The rotation center was located closer to the screw tip in the Sr-HA group (19% of screw length) than in the PMMA group (37%). The only kinematic difference between Sr-HA and PMMA cements was the screw rotation at 1000 cycles (1.5° ± 0.9° vs. 1.3° ± 0.6°; P = 0.0026). All motion parameters increased significantly with more loading cycles. The pullout force was higher in the PMMA group than the Sr-HA group (1.40 ± 0.63 kN vs. 0.93 ± 0.70 kN), and this difference was marginally significant (P = 0.051). Sr-HA cement covered more of the screw length than PMMA cement (79 ± 19% vs. 43 ± 19%) (P = 0.036). Conclusion. This paired-design study identified some subtle but mostly nonsignificant differences in immediate biomechanical fixation of pedicle screws augmented with the Sr-HA cement compared with the PMMA cement.

Load transfer characteristics between posterior spinal implants and the lumbar spine under anterior shear loading: an in vitro investigation.

Study Design. A biomechanical human cadaveric study. Objective. To determine the percentage of shear force supported by posterior lumbar spinal devices of varying stiffnesses under anterior shear loading in a degenerative spondylolisthesis model. Summary of Background Data. Clinical studies have demonstrated beneficial results of posterior arthrodesis for the treatment of degenerative spinal conditions with instability. Novel spinal implants are designed to correct and maintain spinal alignment, share load with the spine, and minimize adjacent level stresses. The optimal stiffness of these spinal systems is unknown. To our knowledge, low-stiffness posterior instrumentation has not been tested under an anterior shear force, a highly relevant force to be neutralized in the clinical case of degenerative spondylolisthesis. Methods. The effects of implant stiffness and specimen condition on implant load and intervertebral motion were assessed in a biomechanical study. Fifteen human cadaveric lumbar functional spinal units were tested under a static 300 N axial compression force and a cyclic anterior shear force (5–250 N). Implants (high-stiffness [HSI]: ø 5.5-mm titanium, medium-stiffness [MSI]: ø 6.35 × 7.2-mm oblong PEEK, and low-stiffness [LSI]: ø 5.5-mm round PEEK) instrumented with strain gauges were used to calculate loads and were tested in each of 3 specimen conditions simulating degenerative changes: intact, facet instability, and disc instability. Intervertebral motions were measured with a motion capture system. Results. As predicted, implants supported a significantly greater shear force as the specimen was progressively destabilized. Mean implant loads as a percent of the applied shear force in order of increasing specimen destabilization for the HSI were 43%, 67%, and 76%; mean implant loads for the MSI were 32%, 56%, and 77%; and mean implant loads for the LSI were 18%, 35%, and 50%. Anterior translations increased with decreasing implant stiffness and increasing specimen destabilization. Conclusion. Implant shear stiffness significantly affected the load sharing between the implant and the natural spine in anterior shear ex vivo. Low-stiffness implants transferred significantly greater loads to the spine. This study supports the importance of load-sharing behavior when designing new implants.

An ex vivo biomechanical comparison of a novel vertebral compression fracture treatment system to kyphoplasty

BACKGROUND Vertebral compression fracture repair aims to relieve pain and improve function by restoring vertebral structure and biomechanics, but is still associated with risks arising from polymethylmethacrylate cement extravasation. The Kiva® Vertebral Compression Fracture Treatment System, a stacked coil implant made of polyetheretherketone and delivered over a guide-wire, is a novel device designed to provide height restoration and mechanical stabilization, while improving cement containment and minimizing disruption of cancellous bone. The objective of this study was to determine whether the Kiva system is as effective as balloon kyphoplasty at restoring mechanical properties in osteoporotic vertebral compression fractures. METHODS Wedge fractures were created in the middle vertebra of fourteen osteoporotic three-vertebra spine segments and then repaired with either the Kiva or kyphoplasty procedure. Height, stiffness and displacement under compression of the spine segments were measured for four conditions: intact, fractured, augmented, and post-cyclic eccentric loading (50,000cycles, 200-500N, 30mm anterior lever arm). FINDINGS No significant differences were seen between the two procedures for height restoration, stiffness at high or low loads, or displacement under compression. However, the Kiva System required an average of 66% less cement than kyphoplasty to achieve these outcomes (mean 2.6 (SD 0.4) mL v. mean 7.5 (SD 0.8) mL 0; P<0.01). Extravasations and excessive posterior cement flow were also significantly lower with Kiva (0/7 v. 4/7; P<.05). INTERPRETATION Kiva exhibits similar biomechanical performance to balloon kyphoplasty, but may reduce the risk of extravasation through the containment mechanism of the implant design and by reducing cement volume.

An in vitro model of degenerative lumbar spondylolisthesis.

Study Design. A biomechanical human cadaveric study. Objective. To create a biomechanical model of low-grade degenerative lumbar spondylolisthesis (DLS), defined by anterior listhesis, for future testing of spinal instrumentation. Summary of Background Data. Current spinal implants are used to treat a multitude of conditions that range from herniated discs to degenerative diseases. The optimal stiffness of these instrumentation systems for each specific spinal condition is unknown. Ex vivo models representing degenerative spinal conditions are scarce in the literature. A model of DLS for implant testing will enhance our understanding of implant-spine behavior for specific populations of patients. Methods. Four incremental surgical destabilizations were performed on 8 lumbar functional spinal units. The facet complex and intervertebral disc were targeted to represent the tissue changes associated with DLS. After each destabilization, the specimen was tested with: (1) applied shear force (−50 to 250 N) with a constant axial compression force (300 N) and (2) applied pure moments in flexion-extension, lateral bending and axial rotation (±5 Nm). Relative motion between the 2 vertebrae was tracked with a motion capture system. The effect of specimen condition on intervertebral motion was assessed for shear and flexibility testing. Results. Shear translation increased, specimen stiffness decreased and range of motion increased with specimen destabilization (P < 0.0002). A mean anterior translation of 3.1 mm (SD 1.1 mm) was achieved only after destabilization of both the facet complex and disc. Of the 5 specimen conditions, 3 were required to achieve grade 1 DLS: (1) intact, (3) a 4-mm facet gap, and (5) a combined nucleus and annulus injury. Conclusion. Destabilization of both the facet complex and disc was required to achieve anterior listhesis of 3.1 mm consistent with a grade 1 DLS under an applied shear force of 250 N. Sufficient listhesis was measured without radical specimen resection. Important anatomical structures for supporting spinal instrumentation were preserved such that this model can be used in future to characterize behavior of novel instrumentation prior to clinical trials.

Activities performed and treatments conducted before consultation with a spine surgeon: are patients and clinicians following evidence-based clinical practice guidelines?

BACKGROUND CONTEXT Clinical practice guidelines (CPGs) are designed to ensure that evidence-based treatment is easily put into action. Whether patients and clinicians follow these guidelines is equivocal. PURPOSE The objectives of this study were to examine how many patients complaining of low back pain (LBP) underwent evidence-based medical interventional treatment in line with CPG recommendations before consultation with a spine surgeon, and to evaluate any associations between adherence to CPG recommendations and baseline factors. STUDY DESIGN/SETTING This is a cross-sectional cohort analysis at a tertiary care center. PATIENT SAMPLE A total of 229 patients were referred for surgical consultation for an elective lumbar spinal condition. OUTCOME MEASURES The outcome measures include the number of CPG-recommended treatments undertaken by patients at or before the time of referral, the validated pain score, the EuroQol-5D (EQ-5D) health status, and the Oswestry Disability Index (ODI) score. METHODS Questionnaires assessing demographic and functional characteristics as well as overall health care use were sent to patients immediately after their referral was received by the surgeons office. RESULTS Medications were the most common modality before consultation (74.2% of patients), of which 46.3% received opioids. The number of medications taken was significantly related to a higher ODI score (R=0.23, p=.0004), a higher pain score (R=0.15, p=.026), and a lower EQ-5D health status (R=-0.15, p=.024). In contrast, a lower pain score (7.2 vs. 7.7, p=.037) and a lower ODI score (26.6 vs. 29.9, p=.0023) were associated with performing adequate amounts of exercise. There was a significant association between lower numbers of treatments received and higher numerical pain rating scores (R=-0.14, p=.035). The majority (61.1%) of patients received two or less forms of treatment. CONCLUSIONS Evidence-based medical interventional treatments for patients with LBP are not being taken advantage of before spine surgery consultation. If more patients were to undertake CPG-endorsed conservative modalities, it may result in fewer unnecessary referrals from primary care physicians, and patients might not deteriorate as much while lingering on long wait lists. Further studies incorporating knowledge translation or health system pathway changes are necessary.

Increased Prevalence of Chronic Disease in Back Pain Patients Living in Car-dependent Neighbourhoods in Canada: A Cross-sectional Analysis

Objectives Chronic diseases, including back pain, result in significant patient morbidity and societal burden. Overall improvement in physical fitness is recommended for prevention and treatment. Walking is a convenient modality for achieving initial gains. Our objective was to determine whether neighbourhood walkability, acting as a surrogate measure of physical fitness, was associated with the presence of chronic disease. Methods We conducted a cross-sectional study of prospectively collected data from a prior randomized cohort study of 227 patients referred for tertiary assessment of chronic back pain in Ottawa, ON, Canada. The Charlson Comorbidity Index (CCI) was calculated from patient-completed questionnaires and medical record review. Using patients’ postal codes, neighbourhood walkability was determined using the Walk Score, which awards points based on the distance to the closest amenities, yielding a score from 0 to 100 (0-50: car-dependent; 50-100: walkable). Results Based on the Walk Score, 134 patients lived in car-dependent neighborhoods and 93 lived in walkable neighborhoods. A multivariate logistic regression model, adjusted for age, gender, rural postal code, body mass index, smoking, median household income, percent employment, pain, and disability, demonstrated an adjusted odds ratio of 2.75 (95% confidence interval, 1.16 to 6.53) times higher prevalence for having a chronic disease for patients living in a car-dependent neighborhood. There was also a significant dose-related association (p=0.01; Mantel-Haenszel chi-square=6.4) between living in car-dependent neighbourhoods and more severe CCI scores. Conclusions Our findings suggest that advocating for improved neighbourhood planning to permit greater walkability may help offset the burden of chronic disease.

Treatment Options for Back Pain Provided Online in Canadian Magazines: Comparison against Evidence from a Clinical Practice Guideline.

Background: Evidence-based treatments for adult back pain have long been confirmed, with research continuing to narrow down the scope of recommended practices. However, a tension exists between research-driven treatments and unsubstantiated modalities and techniques promoted to the public. This disparity in knowledge translation, which results in unsupported treatments continuing to be performed, may be linked to the information dispensed by the mass media. Objectives: The aim of this study was to review the top 20 most circulated Canadian-produced general-interest and health-specific magazines to determine whether featured treatment options align with recommendations for back pain management in a Canadian clinical practice guideline (CPG). Methods: Online electronic searches of magazine websites were performed using the following terms: ‘back pain’, ‘low back pain’ (English); ‘mal au dos’, ‘lombalgie’, ‘mal de dos’ and ‘maux de dos’ (French). Independent reviewers screened for articles focusing on treatment, abstracted recommendations from included articles and then compared featured treatments with those outlined in the CPG. Results: A total of 1,775 articles were screened, with 82 articles from 15 magazines included. Articles cited scientific studies or consulted spine-care professionals in 7/15 and 9/15 magazines, respectively. There were 18 categories of treatments reported with 4/18 (22%) treatment options in agreement with CPG recommendations for acute/sub-acute and chronic back pain. Yoga/Stretching/Tai Chi/Pilates and Exercise/Physical activity were the most commonly reported treatment categories. Conclusion: Encouragingly, the majority of treatment options reported for low back pain were non-surgical. Overall, few articles recommended reassurance, back pain education or back-specific postural/strengthening/flexibility exercises. Popular magazines should provide details on article authors, cite scientific reports, consult spine-care professionals and provide relevant links to literature for readers to access more scientific information.