2. Methods – Institutional Cohort

In the institutional cohort, all consecutive adult patients undergoing CDR by a single surgeon during the study period of March 2017 and September 2018 were included. Patients were identified using a prospectively collected registry of spine surgery patients. All patients were consented for inclusion in the registry and local investigational review board approval was obtained prior to creation of the registry (IRB No. 2019-1126). This population was divided into 2 cohorts based the presence or absence of a preoperative diagnosis of cervical myelopathy. The diagnosis of myelopathy is made based on a combination of both radiological findings of spinal cord compression and clinical symptoms of hyperreflexia, ataxia, or loss of fine motor skills. Patients who had both radiographic and clinical findings documented in the preoperative medical chart were given a diagnosis of myelopathy. The severity of preoperative myelopathy was quantified based on the modified Japanese Orthopaedic Association score (mJOA).

Patient demographics including age, body mass index, American Society of Anesthesiologists (ASA) physical status classification, Charlson Comorbidity Index, and smoking status were collected. Operative data including number of disc levels treated (1 or 2), operative time, estimated blood loss, postoperative length of stay, postoperative transfusions, maximum postanesthesia care unit pain score within 3 hours postoperatively, and complications including neurological injury, surgical site infection, and incidental durotomy were recorded. Patient-reported outcomes measures (PROMs) were collected for patients preoperatively and at 2-, and 6-week postoperative visits. The PROMs collected include visual analogue scale (VAS)-arm pain, VAS-neck pain, Neck Disability Index (NDI), and mJOA.