Deterioration after Surgery for Degenerative Cervical Myelopathy: An Observational Study from the Canadian Spine Outcomes and Research Network.

Abstract

Prospective cohort study. To investigate the incidence, etiology, and outcomes of patients who experience neurological deterioration after surgery for Degenerative Cervical Myelopathy (DCM). Post-operative neurological deterioration is one of the most undesirable complications that can occur after surgery for DCM. We analyzed data from the Canadian Spine Outcomes and Research Network (CSORN) DCM prospective cohort study. We defined post-operative neurological deterioration as any decrease in modified Japanese Orthopaedic Association (mJOA) score by at least one point from baseline to 3 months after surgery. Adverse events were collected using the Spinal Adverse Events Severity (SAVES) protocol. Secondary outcomes included patient-reported pain, disability, and health-related quality of life. Among a study cohort of 428 patients, 50 (12%) deteriorated by at least one mJOA point after surgery for DCM (21 by 1 point, 15 by 2 points, and 14 by three points or more). Significant risk factors included older age, female sex, and milder disease. Among those who deteriorated, 13 experienced contributing intra- or post-operative adverse events, 6 had alternative non-DCM diagnoses, and 31 did not have an identifiable reason for deterioration. Patients who deteriorated had significantly lower mJOA scores at one year after surgery (13.5 (SD 2.7) versus 15.2 (SD 2.2), P<0.01) and those with larger deteriorations were less likely to recover their mJOA to at least their pre-operative baseline, but most secondary measures of pain, disability, and health-related quality of life were unaffected. The incidence of deterioration of mJOA scores after surgery for DCM was approximately one in ten, but some deteriorations were unrelated to actual spinal cord impairment and most secondary outcomes were unaffected. These findings can inform patient and surgeon expectations during shared decision-making, and they demonstrate that interpretation of mJOA scores without clinical context can sometimes be misleading.