What predicts the best 24-month outcomes following surgery for cervical spondylotic myelopathy? A QOD prospective registry study
Authors: Chan Andrew K. , Park Christine , Shaffrey Christopher I. , Gottfried Oren N. , Than Khoi D. , Bisson Erica F. , Bydon Mohamad , Asher Anthony L. , Coric Domagoj , Potts Eric A. , Foley Kevin T. , Wang Michael Y. , Fu Kai-Ming , Virk Michael S. , Knightly John J. , Meyer Scott , Park Paul , Upadhyaya Cheerag D. , Shaffrey Mark E. , Buchholz Avery L. , Tumialán Luis M. , Turner Jay D. , Michalopoulos Giorgos , Sherrod Brandon A. , Agarwal Nitin , Chou Dean , Haid Regis W. , Mummaneni Praveen V. 
Published: January 2024

OBJECTIVE
The aim of this study was to identify predictors of the best 24-month improvements in patients undergoing surgery for cervical spondylotic myelopathy (CSM). For this purpose, the authors leveraged a large prospective cohort of surgically treated patients with CSM to identify factors predicting the best outcomes for disability, quality of life, and functional status following surgery.

METHODS
This was a retrospective analysis of prospectively collected data. The Quality Outcomes Database (QOD) CSM dataset (1141 patients) at 14 top enrolling sites was used. Baseline and surgical characteristics were compared for those reporting the top and bottom 20th percentile 24-month Neck Disability Index (NDI), EuroQol-5D (EQ-5D), and modified Japanese Orthopaedic Association (mJOA) change scores. A multivariable logistic model was constructed and included candidate variables reaching p ≤ 0.20 on univariate analyses. Least important variables were removed in a stepwise manner to determine the significant predictors of the best outcomes (top 20th percentile) for 24-month NDI, EQ-5D, and mJOA change.

RESULTS
A total of 948 (83.1%) patients with 24-month follow-up were included in this study. For NDI, 204 (17.9%) had the best NDI outcome and 200 (17.5%) had the worst NDI outcome. Factors predicting the best NDI outcomes included symptom duration less than 12 months (OR 1.5, 95% CI 1.1–1.9; p = 0.01); procedure other than posterior fusion (OR 1.5, 95% CI 1.03–2.1; p = 0.03); higher preoperative visual analog scale neck pain score (OR 1.2, 95% CI 1.1–1.3; p < 0.001); and higher baseline NDI (OR 1.06, 95% CI 1.05–1.07; p < 0.001). For EQ-5D, 163 (14.3%) had the best EQ-5D outcome and 169 (14.8%) had the worst EQ-5D outcome. Factors predicting the best EQ-5D outcomes included arm pain–only complaints (compared to neck pain) (OR 1.9, 95% CI 1.3–2.9; p = 0.002) and lower baseline EQ-5D (OR 167.7 per unit lower, 95% CI 85.0–339.4; p < 0.001). For mJOA, 222 (19.5%) had the best mJOA outcome and 238 (20.9%) had the worst mJOA outcome. Factors predicting the best mJOA outcomes included lower BMI (OR 1.03 per unit lower, 95% CI 1.004–1.05; p = 0.02; cutoff value of ≤ 29.5 kg/m2); arm pain–only complaints (compared to neck pain) (OR 1.7, 95% CI 1.1–2.5; p = 0.02); and lower baseline mJOA (OR 1.6 per unit lower, 95% CI 1.5–1.7; p < 0.001).

CONCLUSIONS
Compared to the worst outcomes for EQ-5D, the best outcomes were associated with patients with arm pain–only complaints. For mJOA, lower BMI and arm pain–only complaints portended the best outcomes. For NDI, those with the best outcomes had shorter symptom durations, higher preoperative neck pain scores, and less often underwent posterior spinal fusions. Given the positive impact of shorter symptom duration on outcomes, these data suggest that early surgery may be beneficial for patients with CSM.