Discussion

Introduction: There is a lack of data examining the effects of peri-operative adverse events (AEs) on long-term outcomes for patients undergoing surgery for degenerative cervical myelopathy (DCM). We aimed to investigate associations between the occurrence of perioperative AEs and co-primary outcomes: 1) modified Japanese Orthopedic Association (mJOA) score and 2) neck disability index (NDI) score.

Methods: We analyzed data from 800 consecutive patients prospectively enrolled in the Canadian Spine Outcomes and Research Network multicenter observational study. The Spine AdVerse Events Severity system was used to collect intra- and post-operative AEs. Patients were assessed at up to 2 years post-surgery using the NDI and the mJOA scale. We used a linear mixed effect regression to assess the influence of AEs on longitudinal outcome measures as well as multivariable logistic regression to assess factors associated with meeting minimal clinically important difference (MCID) thresholds at 1 year.

Results: There were 167 (20.9%) patients with minor AEs and 36 (4.5%) patients with major AEs. The occurrence of major AEs was associated with an average increase in NDI of 6.8 points (95% CI: 1.1 – 12.4, p=0.019) and reduction of 1.5 points for mJOA scores (95% CI: -2.3 to -0.8, p< 0.001) up to 2 years after surgery. Occurrence of major AEs reduced the odds of patients achieving MCID targets at 1-year post-surgery for mJOA (OR 0.23, 95% CI: 0.086 - 0.53, p=0.001) and for NDI (OR 0.34, 95% CI: 0.11 – 0.84, p=0.032).

Conclusion : Major AEs were associated with reduced functional gains and worse recovery trajectories for patients undergoing surgery for DCM. Occurrence of major AEs reduced the probability of achieving mJOA and NDI MCID thresholds at 1 year. Both minor and major AEs significantly increased health resource utilization by reducing the proportion of discharges home and increasing length of stay.