Preoperative Range of Motion in Extension May Influence Postoperative Cervical Kyphosis After Laminoplasty

Study Design. Retrospective observational study. Objective. The objective of this study was to investigate factors associated with cervical kyphosis after laminoplasty. Summary of Background Data. Many factors are reportedly associated with the deterioration of cervical curvature after laminoplasty, including cervical lordosis angle, cervical spine range of motion (ROM), T1 slope, and C2-C7 sagittal vertical axis. Postlaminoplasty kyphosis or deterioration of cervical curvature is likely caused by multiple factors. There is currently no consensus on these issues. Materials and Methods. Data of patients treated with laminoplasty for degenerative cervical myelopathy at our institution during 2008-2018 were reviewed. The following variables were collected for each patient: age and sex; follow-up time; surgery involving C3 (yes or no); surgery involving C7 (yes or no); distribution of segments operated on; number of laminae operated on; flexion, extension, and total ROM; cervical lordotic angle; longitudinal distance index; curvature index; C2-C7 sagittal vertical axis; and T1 slope. Logistic regression analysis was used to assess possible risk factors for postoperative kyphosis. Receiver operating characteristic curves were constructed to determine the cutoff values of risk factors. Results. The study cohort comprised 151 patients. Logistic regression analysis indicated that sex, number of laminae operated on, and preoperative extension ROM were significantly associated with postoperative cervical kyphosis (P< 0.05). There was significantly greater postoperative kyphosis in women than in men; the more segments operated on, the greater the risk of postoperative kyphosis, and the larger the preoperative extension ROM, the lower the risk of postlaminoplasty kyphosis. Receiver operating characteristic curve analysis showed that the cutoff value for preoperative extension ROM is 22.1 degrees. Conclusions. Preoperative extension ROM may be associated with the development of postoperative kyphosis. The cutoff value of preoperative extension ROM that suggested the prospect of postoperative kyphosis in our sample was 22.1 degrees.