Identification of Optimal Candidates for Operative Management of Mild Degenerative Cervical Myelopathy: A Novel trajectory-based Analysis of Postoperative Recovery.

Study design: Retrospective cohort study using prospectively accrued data.

Objective: To describe the functional recovery trajectories after surgery for mild degenerative cervical myelopathy (DCM) and identify trajectory-associated preoperative factors.

Summary of background data: Indications for surgical intervention of mild DCM remain a topic of discussion and uncertainty. We sought to address the hypothesis that optimal surgical candidates with mild DCM could be identified based on their predicted postoperative functional recovery after surgery.

Methods: We identified patients that underwent surgical decompression for mild DCM (modified Japanese Orthopedic Association score 15 - 17) enrolled in the prospective, multicenter AO Spine CSM-NA and CSM-I trials. Patients were classified using trajectory modelling into distinct recovery trajectories for their mJOA and Short Form 36, version 2 Physical Component Summary (SF36-PCS) scores over 2yr follow up. Predictors of recovery trajectories were identified using multivariate logistic regression.

Results: Of 198 patients with mild DCM, two distinct functional recovery trajectories for mJOA and two trajectories for SF36-PCS were identified. The good recovery trajectory for mJOA included 138 patients (69.7%) that achieved clinically important improvements in their function through two-year follow up while 60 patients (30.3%) followed a marginal recovery trajectory, whereas the SF36-PCS good recovery trajectory group captured 166 patients (59.5%), and 79 patients (40.5%) in the marginal recovery group. Achieving good recovery in both mJOA and SF36-PCS was associated with higher self-reported baseline physical functioning. Patients who were older or current or former tobacco smokers were less likely to have a good postoperative recovery.

Conclusion: Most mild DCM patients achieve clinically important recoveries of their function and selfreported physical function after surgery. However, there is a heterogenous group of patients that do not improve after surgical management. Further prospective studies are needed to evaluate clinically relevant factors associated with varying postoperative trajectories.

Level of evidence: 3.