Patient demographics of cervical spine surgery in Japan: Prospective multicenter cohort study

Degenerative cervical spine disorders, including cervical spondylotic myelopathy (CSM), ossification of the posterior longitudinal ligament (OPLL), and cervical disc herniation (CDH), are common surgical indications in aging populations. OPLL is more prevalent in East Asians, likely due to genetic and metabolic factors, yet large-scale prospective data from Asia remain limited. To characterize diagnosis-specific and age-related clinical features in Japanese patients undergoing cervical spine surgery for degenerative conditions, with a focus on frailty, body mass index (BMI), and neurological status. This prospective multicenter study enrolled 1,482 patients undergoing surgery for degenerative, non-traumatic cervical spine disorders at 10 Japanese institutions between 2019 and 2022. Diagnoses included CSM, OPLL, CDH, cervical radiculopathy (CSR), cervical spondylotic amyotrophy (CSA), and atlantoaxial instability (AAI). Baseline variables included age, sex, BMI, comorbidities, and Japanese Orthopaedic Association (JOA) score. Frailty was assessed using the 11-item modified frailty index (mFI-11), with scores ≥0.27 indicating frailty. Statistical comparisons used ANOVA and chi-square tests. CSM was the most frequent diagnosis (58.7%), followed by OPLL (15.9%) and CDH (14.6%). CDH patients were younger (mean age 53.3), while CSM and AAI predominated in older age groups. Frailty increased with age, from 2.7% in patients aged 40–59 to 30.5% in those ≥80 years. OPLL patients had the highest BMI (26.3 kg/m 2 ) and diabetes prevalence (22.1%). CSM patients showed the lowest mean JOA scores (9.6). This large cohort reveals distinct age- and diagnosis-specific patterns in cervical spine surgery, underscoring the importance of frailty-aware.