Cervical spine range of motion (ROM) is a critical factor in changes in cervical sagittal alignment (CSA) and clinical outcomes after cervical laminoplasty (LMP). However, the impact of postoperative cervical ROM on CSA after cervical LMP is still unclear.Evaluating the imaging and symptomatic data from patients with cervical spondylotic myelopathy (CSM) to identify the influence of postoperative cervical ROM on post-LMP CSA and surgical outcomes.Retrospective study.Eighty-six patients undergoing LMP due to multilevel CSM OUTCOME MEASURES: Radiographic parameters were measured before surgery and at follow-up: cervical lordosis (CL), T1 slope (T1S), cervical sagittal vertical axis (cSVA), CL in flexion (Flex CL), CL in extension (Ext CL), total cervical spine range of motion (ROM), cervical spine range of flexion (Flex ROM), and cervical spine range of extension (Ext ROM). Japanese Orthopedic Association (JOA) and visual analog score (VAS) were used to assessed clinical outcomes. Other parameters included age, gender, body mass index (BMI), follow-up time, number of surgical segments, proximal level, distalis level, and collar wear time.We divided patients according to the changes in CSA (loss of cervical lordosis (LCL)>10°, or ≤10°; an increase in cervical sagittal vertical axis (I-cSVA) > 10mm, or ≤10mm). A receiver-operating characteristic curve (ROC) analysis was constructed to identify the optimal cut-off value to discriminate the patients with and without postoperative deterioration of CSA.The postoperative total and Flex ROM were significantly lower in the LCL>10° and I-cSVA>10mm groups. Multivariate logistic regression analysis showed that low post-Flex ROM was significant risk factor for postoperative deterioration of CSA. ROC showed that the cut-off value for postoperative Flex ROM was 15.60°. Improvements in JOA recovery rate and neck pain were more significant in the flexibility group (post-Flex ROM ≥ 15.6°) after surgery. Patients in the stiffness group (post-Flex ROM < 15.6°) wore a collar longer.The preservation of cervical flexibility can maintain CSA after cervical LMP. Postoperative cervical stiffness is related to poor surgical outcomes because significant cervical kyphotic change and sagittal imbalance are likely to occur after surgery. Prolonged wearing of cervical collar is correlated with cervical stiffness following cervical LMP.Copyright © 2024. Published by Elsevier Inc.