title: Predicting the minimum clinically important difference in patients undergoing surgery for the treatment of degenerative cervical myelopathy.
abstract: OBJECTIVE The minimum clinically important difference (MCID) is defined as the minimum change in a measurement that a patient would identify as beneficial. Before undergoing surgery, patients are likely to inquire about the ultimate goals of the operation and of their chances of experiencing meaningful improvements. The objective of this study was to define significant predictors of achieving an MCID on the modified Japanese Orthopaedic Association (mJOA) scale at 2 years following surgery for the treatment of degenerative cervical myelopathy (DCM). METHODS Seven hundred fifty-seven patients were prospectively enrolled in either the AOSpine North America or International study at 26 global sites. Fourteen patients had a perfect preoperative mJOA score of 18 and were excluded from this analysis (n = 743). Data were collected for each participating subject, including demographic information, symptomatology, medical history, causative pathology, and functional impairment. Univariate log-binominal regression analyses were conducted to evaluate the association between preoperative clinical factors and achieving an MCID on the mJOA scale. Modified Poisson regression using robust error variances was used to create the final multivariate model and compute the relative risk for each predictor. RESULTS The sample consisted of 463 men (62.31%) and 280 women (37.69%), with an average age of 56.48 ± 11.85 years. At 2 years following surgery, patients exhibited a mean change in functional status of 2.71 ± 2.89 points on the mJOA scale. Of the 687 patients with available follow-up data, 481 (70.01%) exhibited meaningful gains on the mJOA scale, whereas 206 (29.98%) failed to achieve an MCID. Based on univariate analysis, significant predictors of achieving the MCID on the mJOA scale were younger age; female sex; shorter duration of symptoms; nonsmoking status; a lower comorbidity score and absence of cardiovascular disease; and absence of upgoing plantar responses, lower-limb spasticity, and broad-based unstable gait. The final model included age (relative risk [RR] 0.924, p < 0.0001), smoking status (RR 0.837, p = 0.0043), broad-based unstable gait (RR 0.869, p = 0.0036), and duration of symptoms (RR 0.943, p = 0.0003). CONCLUSIONS In this large multinational prospective cohort, 70% of patients treated surgically for DCM exhibited a meaningful functional gain on the mJOA scale. The key predictors of achieving an MCID on the mJOA scale were younger age, shorter duration of symptoms, nonsmoking status, and lack of significant gait impairment.
authors.affiliation: Division of Neurosurgery, Toronto Western Hospital, University Health Network, Toronto;
authors.forename: Lindsay
authors.initials: L
authors.lastname: Tetreault
authors.affiliation: Division of Neurosurgery, Toronto Western Hospital, University Health Network, Toronto;
authors.forename: Jefferson R
authors.initials: JR
authors.lastname: Wilson
authors.affiliation: Division of Neurosurgery, Toronto Western Hospital, University Health Network, Toronto;
authors.forename: Mark R N
authors.initials: MR
authors.lastname: Kotter
authors.affiliation: Division of Neurosurgery, Toronto Western Hospital, University Health Network, Toronto;
authors.forename: Aria
authors.initials: A
authors.lastname: Nouri
authors.affiliation: University of Ontario Institute of Technology, Faculty of Health Sciences, Oshawa, Ontario, Canada;
authors.forename: Pierre
authors.initials: P
authors.lastname: Côté
authors.affiliation: Department of Health Services, School of Public Health, University of Washington, Seattle, Washington; and.
authors.forename: Branko
authors.initials: B
authors.lastname: Kopjar
authors.affiliation: Department of Neurosurgery, University of Kansas, Kansas City, Kansas.
authors.forename: Paul M
authors.initials: PM
authors.lastname: Arnold
authors.affiliation: Division of Neurosurgery, Toronto Western Hospital, University Health Network, Toronto;
authors.forename: Michael G
authors.initials: MG
authors.lastname: Fehlings
mesh_terms: D000328:Adult; D000368:Aged; D000704:Analysis of Variance; D015331:Cohort Studies; D019299:Decompression, Surgical / Q000379:methods*; D004185:Disability Evaluation; D005260:Female; D014943:Global Health; D006801:Humans; D008297:Male; D008875:Middle Aged; D019636:Neurodegenerative Diseases / Q000150:complications / Q000601:surgery*; D011237:Predictive Value of Tests; D012044:Regression Analysis; D012720:Severity of Illness Index; D013122:Spinal Diseases / Q000150:complications / Q000601:surgery*; D016896:Treatment Outcome
keywords: DCM = degenerative cervical myelopathy; MCID; MCID = minimum clinically important difference; cervical spondylotic myelopathy; degenerative cervical myelopathy; mJOA = modified Japanese Orthopaedic Association; minimum clinically important difference; outcome prediction; surgical outcomes