Clinical predictors of achieving the minimal clinically important difference after surgery for cervical spondylotic myelopathy: an external validation study from the Canadian Spine Outcomes and Research Network

Nathan Evaniew MD, PhD, FRCSC 1 , David W. Cadotte MD, PhD, FRCSC 1 , Nicolas Dea MD, MSc, FRCSC 2 , Christopher S. Bailey MD, MSc, FRCSC 3 , Sean D. Christie MD, FRCSC 4 , Charles G. Fisher MD, MHSc, FRCSC 2 , Jerome Paquet MD, FRCSC 5 , Alex Soroceanu MD, CM, MPH, FRCSC 1 , Kenneth C. Thomas MD, MHSc, FRCSC 1 , Y. Raja Rampersaud MD, FRCSC 6 , Neil A. Manson MD, FRCSC 4 , 7 , Michael Johnson MD, FRCSC 8 , Andrew Nataraj MD, MSc, FRCSC 9 , Hamilton Hall MD, FRCSC 6 , Greg McIntosh MSc 10 and W. Bradley Jacobs MD, FRCSC 1
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  • 1 University of Calgary Spine Program, University of Calgary, Alberta;
  • 2 Vancouver Spine Surgery Institute, University of British Columba, Vancouver, British Columbia;
  • 3 Department of Surgery, Western University, London, Ontario;
  • 4 Department of Surgery, Dalhousie University, Halifax, Nova Scotia;
  • 5 Département de chirurgie, Université Laval, Québec;
  • 6 Department of Surgery, University of Toronto, Ontario;
  • 7 Canada East Spine Centre, Saint John, New Brunswick;
  • 8 Department of Surgery, University of Manitoba, Winnipeg, Manitoba;
  • 9 Department of Surgery, University of Alberta, Edmonton, Alberta; and
  • 10 Canadian Spine Outcomes and Research Network, Markdale, Ontario, Canada
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Recently identified prognostic variables among patients undergoing surgery for cervical spondylotic myelopathy (CSM) are limited to two large international data sets. To optimally inform shared clinical decision-making, the authors evaluated which preoperative clinical factors are significantly associated with improvement on the modified Japanese Orthopaedic Association (mJOA) scale by at least the minimum clinically important difference (MCID) 12 months after surgery, among patients from the Canadian Spine Outcomes and Research Network (CSORN).


The authors performed an observational cohort study with data that were prospectively collected from CSM patients at 7 centers between 2015 and 2017. Candidate variables were tested using univariable and multiple binomial logistic regression, and multiple sensitivity analyses were performed to test assumptions about the nature of the statistical models. Validated mJOA MCIDs were implemented that varied according to baseline CSM severity.


Among 205 patients with CSM, there were 64 (31%) classified as mild, 86 (42%) as moderate, and 55 (27%) as severe. Overall, 52% of patients achieved MCID and the mean change in mJOA score at 12 months after surgery was 1.7 ± 2.6 points (p < 0.01), but the subgroup of patients with mild CSM did not significantly improve (mean change 0.1 ± 1.9 points, p = 0.8). Univariate analyses failed to identify significant associations between achieving MCID and sex, BMI, living status, education, smoking, disability claims, or number of comorbidities. After adjustment for potential confounders, the odds of achieving MCID were significantly reduced with older age (OR 0.7 per decade, 95% CI 0.5–0.9, p < 0.01) and higher baseline mJOA score (OR 0.8 per point, 95% CI 0.7–0.9, p < 0.01). The effects of symptom duration (OR 1.0 per additional month, 95% CI 0.9–1.0, p = 0.2) and smoking (OR 0.4, 95% CI 0.2–1.0, p = 0.06) were not statistically significant.


Surgery is effective at halting the progression of functional decline with CSM, and approximately half of all patients achieve the MCID. Data from the CSORN confirmed that older age is independently associated with poorer outcomes, but novel findings include that patients with milder CSM did not experience meaningful improvement, and that symptom duration and smoking were not important. These findings support a nuanced approach to shared decision-making that acknowledges some prognostic uncertainty when weighing the various risks, benefits, and alternatives to surgical treatment.

ABBREVIATIONS CSM = cervical spondylotic myelopathy; CSORN = Canadian Spine Outcomes and Research Network; IQR = interquartile range; MCID = minimum clinically important difference; mJOA = modified Japanese Orthopaedic Association; NDI = Neck Disability Index.

Supplementary Materials

    • Appendices 1 and 2 (PDF 433 KB)

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Contributor Notes

Correspondence Nathan Evaniew: University of Calgary, Calgary, AB, Canada.

INCLUDE WHEN CITING Published online April 10, 2020; DOI: 10.3171/2020.2.SPINE191495.

Disclosures Dr. Dea reports direct stock ownership in Medtronic, being a consultant for Stryker, and serving on the speakers bureau for Medtronic and Baxter. Dr. Christie reports being a consultant for Metronic Canada. Dr. Fisher reports being a consultant to Medtronic and NuVasive, receiving royalties from Medtronic, receiving clinical or research support for the study from AOSpine, and receiving fellowship support paid to institution from Medtronic and AOSpine. Dr. Rampersaud reports receiving royalties from and being a consultant to Medtronic. Dr. Manson reports being a consultant to Medtronic Canada and receiving support of non–study-related clinical or research effort from Medtronic Canada. Dr. Johnson reports receiving financial support from Stryker to help fund his research department, which collects data for the CSS Registry. Dr. Jacobs reports being a consultant to Medtronic, Stryker, and DePuy-Synthes.


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