Andrew Nataraj

Pedicle screw insertion in the thoracolumbar spine: comparison of 4 guidance techniques in the intact cadaveric spine.

OBJECT Pedicle screw fixation is a mainstay of thoracolumbar stabilization. Screw insertion using anatomical landmarks and fluoroscopy is common but can be technically challenging and generally involves substantial exposure to ionizing radiation. Computerized navigation has been reported to improve accuracy but is expensive and complex. The authors undertook this study to evaluate these 3 methods in comparison with a fourth technique using standard cervical distractor screws to mark the entry point and trajectory. METHODS Four cadaveric human spines were used for this study. After an initial CT scan, 34 pedicle screws were inserted in each intact spine from T-1 to L-5 using the following 4 screw insertion guidance techniques (1 technique per specimen): use of anatomical landmarks, use of cervical distractor screws and spot fluoroscopy, fluoroscopy-based navigation, and fluoroscopy- and CT-based navigation (using merged imaging data). Postprocedural CT and anatomical dissection were then performed to evaluate screw position for site and degree of breach. RESULTS The cervical distractor screw method had a breach rate of 5.9% versus 29.4%, 32.4%, and 20.6% for use of anatomical landmarks, fluoroscopic navigation, and fluoroscopic-CT navigation, respectively (p < 0.05). There is also a significant association between degree of medial and distal breach and the method of screw insertion (p < 0.05). CONCLUSIONS Cervical distractor screws as pedicle markers offer favorable insertion accuracy and reduction of radiation exposure compared with the other 3 methods used in clinical practice.

Lumbar Fusion for Degenerative Disease: A Systematic Review and Meta-Analysis

BACKGROUND: Due to uncertain evidence, lumbar fusion for degenerative indications is associated with the greatest measured practice variation of any surgical procedure. OBJECTIVE: To summarize the current evidence on the comparative safety and efficacy of lumbar fusion, decompression‐alone, or nonoperative care for degenerative indications. METHODS: A systematic review was conducted using PubMed, MEDLINE, EMBASE, and the Cochrane Central Register of Controlled Trials (up to June 30, 2016). Comparative studies reporting validated measures of safety or efficacy were included. Treatment effects were calculated through DerSimonian and Laird random effects models. RESULTS: The literature search yielded 65 studies (19 randomized controlled trials, 16 prospective cohort studies, 15 retrospective cohort studies, and 15 registries) enrolling a total of 302 620 patients. Disability, pain, and patient satisfaction following fusion, decompression‐alone, or nonoperative care were dependent on surgical indications and study methodology. Relative to decompression‐alone, the risk of reoperation following fusion was increased for spinal stenosis (relative risk [RR] 1.17, 95% confidence interval [CI] 1.06‐1.28) and decreased for spondylolisthesis (RR 0.75, 95% CI 0.68‐0.83). Among patients with spinal stenosis, complications were more frequent following fusion (RR 1.87, 95% CI 1.18‐2.96). Mortality was not significantly associated with any treatment modality. CONCLUSION: Positive clinical change was greatest in patients undergoing fusion for spondylolisthesis while complications and the risk of reoperation limited the benefit of fusion for spinal stenosis. The relative safety and efficacy of fusion for chronic low back pain suggests careful patient selection is required (PROSPERO International Prospective Register of Systematic Reviews number, CRD42015020153).

Magnetic resonance imaging artifact following anterior cervical discectomy and fusion with a trabecular metal cage

OBJECT This study was undertaken to evaluate the impact of postoperative MRI artifact on the assessment of ongoing spinal cord or nerve root compression after anterior cervical discectomy and fusion (ACDF) using a trabecular tantalum cage or bone autograft or allograft. METHODS The authors conducted a retrospective review of postoperative MRI studies of patients treated surgically for cervical disc degenerative disease or cervical instability secondary to trauma. Standard ACDF with either a trabecular tantalum cage or interbody bone graft had been performed. Postoperative MR images were shown twice in random order to each of 3 assessors (2 spine surgeons, 1 neuroradiologist) to determine whether the presence of a tantalum interbody cage and/or anterior cervical fixation plate or screws imparted MRI artifact significant enough to prevent reliable postoperative assessment of ongoing spinal cord or nerve root compression. RESULTS A total of 63 patients were identified. One group of 29 patients received a tantalum interbody cage, with 13 patients (45%) undergoing anterior plate fixation. A second group of 34 patients received bone auto- or allograft, with 23 (68%) undergoing anterior plate fixation. The paramagnetic implant construct artifact had minimal impact on visualization of postoperative surgical level spinal cord compression. In the cage group, 98% (171/174) of the cases were rated as assessable versus 99% in the bone graft group (201/204), with high intraobserver reliability. In contrast, for the assessment of ongoing surgical level nerve root compression, the presence of a tantalum cage significantly decreased visualization of nerve roots to 70% (121/174) in comparison with 85% (173/204) in the bone graft group (p < 0.001). When sequences using turbo spin echo (TSE), a T2-weighted axial sequence, were acquired, nerve roots were rated as assessable in 88% (69/78) of cases; when only axial T2-weighted sequences were available, the nerve roots were rated as assessable in 54% (52/96) of cases (p < 0.01). The presence of anterior plate fixation had minimal impact on visualization of the spinal cord (99% [213/216] for plated cases vs 98% [159/162] for nonplated cases; p = 1.0) or nerve roots (79% [170/216] for plated cases vs 77% [124/162] for nonplated cases; p = 0.62). CONCLUSIONS Interbody fusion with tantalum cage following anterior cervical discectomy imparts significant paramagnetic artifact, which significantly decreases visualization and assessment of ongoing surgical level nerve root, but not spinal cord, compression. Anterior plate constructs do not affect visualization of these structures. TSE T2-weighted sequences significantly improve nerve root visualization and should be performed as part of a standard postoperative protocol when imaging the cervical spine following interbody implantation of materials with potential for paramagnetic artifact.

Foot drop resulting from degenerative lumbar spinal diseases: clinical characteristics and prognosis.

Foot drop is a condition that can substantially add to the disability of patients with degenerative lumbar spinal disorders. The most common degenerative conditions associated with foot drop are lumbar disc herniation and lumbar spinal stenosis. The level most commonly affected is the L4/5 spinal level. Most patients are treated with surgery, although there is insufficient evidence to support that surgery is superior to conservative therapy. In most surgical patients, foot dorsiflexion will improve to some degree. The preoperative power of foot dorsiflexion is the key factor associated with prognosis.

Nonfusion Does Not Prevent Adjacent Segment Disease: Dynesys Long-term Outcomes With Minimum Five-year Follow-up.

Study Design. Case series. Objective. The aim of this study was to determine the relationship between fusion and adjacent segment disease via Dynesys long-term outcomes. Summary of Background Data. Dynesys is a dynamic stabilization system meant to improve symptoms by stabilizing the spine without fusion and avoiding the development of adjacent segment disease. However, few studies have evaluated long-term outcomes. Methods. All patients were operated on with Dynesys from 2006 to 2009 by a single surgeon at a single institution. We prospectively collected 18 variables among the following categories: patient characteristics, comorbidities, surgical indications, and OR variables. We analyzed two primary endpoints: solid fusion on X-ray and clinical adjacent segment disease (ASD) both at 5 years. Secondary endpoints were time to fusion, time to ASD, reoperation, Oswestry disability index (ODI), and visual analogue scale (VAS) leg pain. We conducted a multivariate analysis via the random forest method. Mann-Whitney U test and Fisher exact test were then used to qualify relationship between variables. Results. We had 52 patients to review in the database. Eight had preexisting ASD. Mean follow-up was 92 months (median 87 months). Fifteen had ASD (29%) during follow-up at a mean 45 months (Median 35 months). Nine had a solid fusion (17%), 2 of which also had ASD. Mean time to fusion was 65 months (median 71 months). Differences in improvement of ODI (P = 0.005) and VAS leg pain (P = 0.002) were significant favoring patients without ASD. The multivariate analysis revealed four variables associated with ASD: prior ASD (OR 11.3, P = 0.005), neurological deficit (OR 8.5, P = 0.018), revision OR (OR 8.5, P = 0.018), and multilevel degeneration (OR 0.184, P = 0.026). No variable was associated with fusion. Conclusion. Dynesys was associated with a high rate of ASD over long-term follow-up despite maintaining a low fusion rate. Prior ASD was the strongest predictor of progressive ASD. Level of Evidence: 3

Patient Reported Outcomes Following Surgery for Degenerative Spondylolitshtesis: Comparison of a Universal and Multi-Tier Health Care System

STUDY DESIGN Retrospective review of results from a prospectively collected Canadian cohort in comparison to published literature. OBJECTIVES (1) To investigate whether patients in a universal health care system have different outcomes than those in a multitier health care system in surgical management of degenerative spondylolisthesis (DS). (2) To identify independent factors predictive of outcome in surgical DS patients. SUMMARY OF BACKGROUND DATA Canada has a national health insurance program with unique properties. It is a single-payer system, coverage is universal, and access to specialist care requires referral by the primary care physician. The United States on the other hand is a multitier public/private payer system with more rapid access for insured patients to specialist care. METHODS Surgical DS patients treated between 2013 and 2016 in Canada were identified through the Canadian Spine Outcome Research Network (CSORN) database, a national registry that prospectively enrolls consecutive patients with spinal pathology from 16 tertiary care academic hospitals. This population was compared with the surgical DS arm of patients treated in the Spine Patients Outcome Research Trial (SPORT) study. We compared baseline demographics, spine-related, and health-related quality of life (HRQOL) outcomes at 3 months and 1 year. Multivariate analysis was used to identify factors predictive of outcome in surgical DS patients. RESULTS The CSORN cohort of 213 patients was compared with the SPORT cohort of 248 patients. Patients in the CSORN cohort were younger (mean age 60.1 vs. 65.2; p<.001), comprised fewer females (60.1% vs. 67.7%; p=.09), and had a higher proportion of smokers (23.3% vs. 8.9%; p<.001). The SPORT cohort had more patients receiving compensation (14.6% vs. 7.7%; p<.001). The CSORN cohort consisted of patients with slightly greater baseline disability (Oswestry disability index scores: 47.7 vs. 44.0; p=.008) and had more patients with symptom duration of greater than 6 months (93.7% vs. 62.1%; p<.001). The CSORN cohort showed greater satisfaction with surgical results at 3 months (91.1% vs. 66.1% somewhat or very satisfied; p<.01) and 1 year (88.2% vs. 71.0%, p<.01). Improvements in back and leg pain were similar comparing the two cohorts. On multivariate analysis, duration of symptoms, treatment group (CSORN vs. SPORT) or insurance type (public/Medicare/Medicaid vs. Private/Employer) predicted higher level of postoperative satisfaction. Baseline depression was also associated with worse Oswestry disability index at 1-year postoperative follow-up in both cohorts. CONCLUSIONS Surgical DS patients treated in Canada (CSORN cohort) reported higher levels of satisfaction than those treated in the United States (SPORT cohort) despite similar to slightly worse baseline HRQOL measures. Symptom duration and insurance type appeared to impact satisfaction levels. Improvements in other patient-reported health-related quality of life measures were similar between the cohorts.

Thirty-day readmission rate as a surrogate marker for quality of care in neurosurgical patients: a single-center Canadian experience

OBJECTIVEReadmission to the hospital within 30 days of discharge is used as a surrogate marker for quality and value of care in the United States (US) healthcare system. Concern exists regarding the value of 30-day readmission as a quality of care metric in neurosurgical patients. Few studies have assessed 30-day readmission rates in neurosurgical patients outside the US. The authors performed a retrospective review of all adult neurosurgical patients admitted to a single Canadian neurosurgical academic center and who were discharged to home to assess for the all-cause 30-day readmission rate, unplanned 30-day readmission rate, and avoidable 30-day readmission rate.METHODSA retrospective review was performed assessing 30-day readmission rates after discharge to home in all neurosurgical patients admitted to a single academic neurosurgical center from January 1, 2011, to December 31, 2011. The primary outcomes included rates of all-cause, unplanned, and avoidable readmissions within 30 days of discharge. Secondary outcomes included factors associated with unplanned and avoidable 30-day readmissions.RESULTSA total of 184 of 950 patients (19.4%) were readmitted to the hospital within 30 days of discharge. One-hundred three patients (10.8%) were readmitted for an unplanned reason and 81 (8.5%) were readmitted for a planned or rescheduled operation. Only 19 readmissions (10%) were for a potentially avoidable reason. Univariate analysis identified factors associated with readmission for a complication or persistent/worsening symptom, including age (p = 0.009), length of stay (p = 0.007), general neurosurgery diagnosis (p < 0.001), cranial pathology (p < 0.001), intensive care unit (ICU) admission (p < 0.001), number of initial admission operations (p = 0.01), and shunt procedures (p < 0.001). Multivariate analysis identified predictive factors of readmission, including diagnosis (p = 0.002, OR 2.4, 95% CI 1.4-5.3), cranial pathology (p = 0.002, OR 2.7, 95% CI 1.4-5.3), ICU admission (p = 0.004, OR 2.4, 95% CI 1.3-4.2), and number of first admission operations (p = 0.01, OR 0.51, 95% CI 0.3-0.87). Univariate analysis performed to identify factors associated with potentially avoidable readmissions included length of stay (p = 0.03), diagnosis (p < 0.001), cranial pathology (p = 0.02), and shunt procedures (p < 0.001). Multivariate analysis identified only shunt procedures as a predictive factor for avoidable readmission (p = 0.02, OR 5.6, 95% CI 1.4-22.8).CONCLUSIONSAlmost one-fifth of neurosurgical patients were readmitted within 30 days of discharge. However, only about half of these patients were admitted for an unplanned reason, and only 10% of all readmissions were potentially avoidable. This study demonstrates unique challenges encountered in a publicly funded healthcare setting and supports the growing literature suggesting 30-day readmission rates may serve as an inappropriate quality of care metric in neurosurgical patients. Potentially avoidable readmissions can be predicted, and further research assessing predictors of avoidable readmissions is warranted.

Cortical electrical stimulation in female rats with a cervical spinal cord injury to promote axonal outgrowth

Electrical stimulation (ES) to promote corticospinal tract (CST) repair after spinal cord injury (SCI) is underinvestigated. This study is the first to detail intracortical ES of the injured CST. We hypothesize that cortical ES will promote CST collateralization and regeneration, prevent dieback, and improve recovery in an SCI rat model. The CST was transected at the the fourth cervical level in adult female Lewis rats trained in a stairwell grasping task. Animal groups included (a) ES333 (n = 14; 333 Hz, biphasic pulse for 0.2‐ms duration every 500 ms, 30 pulses per train); (b) ES20 (n = 14; 20 Hz, biphasic pulse for 0.2‐ms duration every 1 s, 60 pulses per train); (c) SCI only (n = 10); and (d) sham (n = 10). ES of the injured forelimbs motor cortex was performed for 30 min immediately prior to SCI. Comparisons between histological data were performed with a 1‐way ANOVA or Kruskal–Wallis test, and grasping scores were compared using repeated‐measures 2‐way ANOVA.

Spinal Intradural Aneurysmal Bone Cyst: A Case Report

Aneurysmal bone cyst (ABC) is anexpanding osteolytic benign lesion accounting for approximately 1%e2% of all bone tumors (1). ABCs often occur within the first 2 decades of life, predominately located in the long bones and spine (2). Despite their benign nature, patients with spinal ABCs often present with pain and neurologic deficits caused by local obstruction and invasion into the surrounding tissue (2). To our knowledge, we report the first presentation of an extraosseous ABC involving the intradural extra-medullary spinal canal.

Validation of the Calgary Spine Severity Score

BACKGROUND CONTEXT The Calgary Spine Severity Score (CSSS) is a published triage score reported in the Spine Journal in 2010. It separates spine referrals into four time categories of urgency. It stratifies patients according to clinical, radiologic, and pathologic findings. The CSSS however still requires external validation at another institution and in an unselected sample of patients. PURPOSE The aim was to validate the CSSS. STUDY DESIGN/SETTING This was a validation study. PATIENT SAMPLE The sample included a total of 316 consecutive patients undergoing spinal surgery between April 2014 and September 2014 at a tertiary care hospital in Canada. OUTCOME MEASURES The outcome was validity of the CSSS via its predicted time to operating room (OR) to predict actual time to OR. METHODS We applied the CSSS to an unselected sample of consecutive patients from a tertiary care hospital between April 2014 and September 2014. Demographic and clinical data were collected. The CSSS was determined. We compared the time with OR predicted by the CSSS in one of four categories (routine>6 months=CSSS 3-5, priority<6 months=CSSS 6-8, urgent<1 month=CSSS 9-11, and emergent<1 week=CSSS 12-15) with the actual time to OR. We used Kaplan-Meier survival analysis to assess the CSSS predictive ability. Cox proportional hazard models were built and compared via analysis of variance to determine whether the models differed in their ability to fit the data. RESULTS Three hundred sixteen patients were eligible. Two hundred eighty-nine had sufficient data. One hundred eighteen were a mismatch with the actual time to OR yielding an accuracy of 63%. The CSSS overestimated the urgency in 68 cases and underestimated it in 50 cases. Notably, seven cauda equina syndrome cases were classified as priority (<6 months) instead of emergent. The concordance was 0.70 and the R-square 0.33. We proposed several adjustments to the CSSS to increase its accuracy. The modified CSSS had an accuracy of 96%, overestimating nine cases and underestimating one case. The concordance was 0.77, and the R-square 0.70. CONCLUSIONS The modified CSSS is an easy-to-use triage score, which represents a substantial improvement as compared with the original CSSS. It now requires further external validation.