Risk factors for C(5) palsy following the posterior spinal process-splitting laminoplasty for cervical ossification of the posterior longitudinal ligament: a case control study

BACKGROUND: Postoperative C(5) palsy is a common complication of laminoplasty for cervical ossification of the posterior longitudinal ligament (C-OPLL), although there are several hypotheses regarding its etiology, the exact pathomechanism for this undesirable event remain unclear. The aim of this study was to review clinical and imaging findings in patients with C(5) palsy and to propose potential risk factors for this complication. METHODS: A total of 220 consecutive patients who had undergone posterior spinal process-splitting laminoplasty (pSPSL) for C-OPLL between January 2018 and December 2019 were included in this study. Postoperative C(5) palsy was defined as deltoid muscle weakness of a grade ≤3 in manual muscle test (MMT). These patients were divided into two groups based on the postoperative development of C(5) palsy: patients with C(5) palsy (group A) and those without C(5) palsy (group B). The clinical and imaging covariates evaluated were age, sex, OPLL type, K-line, foraminal stenosis, gutter malposition, and preoperative spinal cord signal change. Logistic regression was used to analyze the independent risk factors for C(5) palsy. RESULTS: In total, 211 patients (18 in group A and 193 in group B) were enrolled in this study, and the incidence of C(5) palsy was 8.53%. Sixteen patients had a MMT of grade 3 and two had an MMT of grade ≤2. During the follow-up period (mean duration: 25.10±6.67 months), the MMT grade rose to 5 in 16 patients, 4 in one patient, and 3 in one patient. Multivariate analysis revealed that malposition of the bony gutter [odds ratio (OR) 11.073, 95% confidence interval (CI): 3.411, 35.948; P<0.001] and C(4/5) intervertebral foramen stenosis (OR 8.455, 95% CI: 2.559, 27.936; P<0.001) were independent risk factors for C(5) palsy. CONCLUSIONS: The incidence of C(5) palsy was 8.53% among patients undergoing pSPSL for C-OPLL. Gutter malposition and C(4/5) intervertebral foramen stenosis were identified as risk factors for this complication.