Body Mass Index and Surgical Outcomes in Degenerative Cervical Myelopathy: Findings From a Prospective Multicenter Cohort of 935 Patients

Abstract

Study design: Prospective multicenter cohort study.

Objectives: To clarify the relationship between body mass index (BMI) and surgical outcomes in degenerative cervical myelopathy (DCM).

Summary of background data: Obesity is a growing global health concern and has been implicated in DCM. However, evidence on whether BMI affects postoperative neurological and patient-reported outcomes remains inconsistent, with limited prospective multicenter data.

Methods: We prospectively analyzed 935 patients with DCM who underwent surgery at 10 high-volume spine centers in Japan. Patients were categorized as underweight (<18.5), normal weight (18.5-24.9), overweight (25.0-29.9), or obesity (≥30.0) per World Health Organization criteria. Demographics, comorbidities, radiographic parameters, operative variables, and outcomes-Japanese Orthopaedic Association (JOA) score, visual analog scale (VAS) pain scores, Short Form-36 physical (PCS) and mental (MCS) component scores, and Neuropathic Pain Symptom Inventory (NPSI)-were compared across BMI groups over a 2-years follow-up.

Results: Obese patients were younger (mean 60.2 y, P<0.001) and had a higher prevalence of OPLL (47.7%, P<0.001). They required longer operative time (128.3 min) and greater blood loss (91.2 mL) (both P<0.001) but did not have higher perioperative complication rates. Obesity was associated with smaller C2-7 lordosis and reduced cervical range of motion preoperatively and at 2-years (both P<0.05). Underweight patients had the largest mean MCS improvement (+6.0), but differences among BMI groups were not statistically significant (P=0.117). Across all groups, JOA score improvement, recovery rate, PCS change, pain reduction, and NPSI improvement were comparable.

Conclusions: Higher BMI in DCM was associated with greater operative demands, higher OPLL prevalence, and persistent postoperative alignment and motion deficits. However, neurological recovery and patient-reported outcomes were comparable across BMI categories. In patients with surgical indications based on symptoms and imaging findings, surgery can be performed appropriately regardless of BMI, with favorable outcomes achievable through thorough preoperative assessment and strategic surgical planning.

Level of evidence: II.

Keywords: Body mass index; Cervical alignment; Degenerative cervical myelopathy; Neuropathic pain; Obesity; Patient-reported outcome measures; Quality of life; Surgical outcomes; Underweight.