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A Clinical Prediction Model to Determine Outcomes in Patients with Cervical Spondylotic Myelopathy Undergoing Surgical Treatment: Data from the Prospective, Multi-Center AOSpine North America Study

Tetreault, Lindsay A. BSc; Kopjar, Branko MD, PhD; Vaccaro, Alexander MD, PhD; Yoon, Sangwook Tim MD, PhD; Arnold, Paul M. MD; Massicotte, Eric M. MD, MSc, FRCSC; Fehlings, Michael G. MD, PhD, FRCSC

Journal of Bone & Joint Surgery - American Volume: 18 September 2013 - Volume 95 - Issue 18 - p 1659–1666
doi: 10.2106/JBJS.L.01323
Scientific Articles
Supplementary Content

Background: Cervical spondylotic myelopathy is a progressive spine disease and the most common cause of spinal cord dysfunction worldwide. The objective of this study was to develop a prediction model, based on data from a prospective multi-center study, relating a combination of clinical and imaging variables to surgical outcome in patients with cervical spondylotic myelopathy.

Methods: Two hundred and seventy-eight patients diagnosed with cervical spondylotic myelopathy treated surgically were enrolled at twelve different sites in the multi-center AOSpine North America study. Univariate analyses were performed to evaluate the relationship between outcome, assessed with the modified Japanese Orthopaedic Association (mJOA) score, and various clinical and imaging predictors. A set of important candidate variables for the final model was selected on the basis of author consensus, literature support, and statistical findings. Logistic regression was used to formulate the final model.

Results: Univariate analyses demonstrated that the odds of a successful outcome decreased with a longer duration of symptoms (odds ratio [OR] = 0.80, 95% confidence interval [CI] = 0.65 to 0.98, p = 0.030); a lower baseline mJOA score (OR = 0.74, 95% CI = 0.65 to 0.84, p < 0.0001); the presence of psychological comorbidities (OR = 0.51, 95% CI = 0.29 to 0.92, p = 0.024); the presence of broad-based, unstable gait (OR = 2.72, 95% CI = 1.47 to 5.06, p = 0.0018) or other gait impairment (OR = 3.56, 95% CI = 1.75 to 7.22, p = 0.0005); and older age (OR = 0.96, 95% CI = 0.93 to 0.98, p = 0.0004). The dependent variable, the mJOA score at one year, was dichotomized for logistic regression: a “successful” outcome was defined as a final score of ≥16 and a “failed” outcome was a score of <16. The final model included age (OR = 0.97, 95% CI = 0.94 to 0.99, p = 0.0017), duration of symptoms (OR = 0.78, 95% CI = 0.61 to 0.997, p = 0.048), smoking status (OR = 0.46, 95% CI = 0.21 to 0.98, p = 0.043), impairment of gait (OR = 2.66, 95% CI = 1.17 to 6.06, p = 0.020), psychological comorbidities (OR = 0.33, 95% CI = 0.15 to 0.69, p = 0.0035), baseline mJOA score (OR = 1.22, 95% CI = 1.05 to 1.41, p = 0.0084), and baseline transverse area of the cord on magnetic resonance imaging (OR = 1.02, 95% CI = 0.99 to 1.05, p = 0.19). The area under the receiver operator characteristic curve was 0.79, indicating good model prediction.

Conclusions: On the basis of the results of the AOSpine North America study, we identified a list of the most important predictors of surgical outcome for cervical spondylotic myelopathy.

Level of Evidence: Prognostic Level II. See Instructions for Authors for a complete description of levels of evidence.

1Toronto Western Hospital, 399 Bathurst Street, Toronto, ON M5T 2S8, Canada. E-mail address for M.G. Fehlings: Michael.Fehlings@uhn.on.ca

2Department of Health Sciences, University of Washington, 4333 Brooklyn Avenue N.E., Suite 1400/#315, Seattle, WA 98195

3Thomas Jefferson University, 925 Chestnut Street, Philadelphia, PA 19107-4216

4Emory Orthopaedics & Spine Center, Emory University, 59 Executive Park South, Suite 3000, Atlanta, GA 30329

5Department of Neurosurgery, University of Kansas Medical Center, 3901 Rainbow Boulevard, Mail Stop 3021, Kansas City, KS 66160

Copyright 2013 by The Journal of Bone and Joint Surgery, Incorporated
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