• Masaaki Machino, Kei Ando, Kazuyoshi Kobayashi, Masayoshi Morozumi, Satoshi Tanaka, Shunsuke Kanbara, Sadayuki Ito, Taro Inoue, Keigo Ito, Fumihiko Kato, Naoki Ishiguro, and Shiro Imagama.
• Department of Orthopedic Surgery, Nagoya University Graduate School of Medicine, Nagoya, Japan.
• Spine. 2020 May 15; 45 (10): 641-648.

Study DesignA prospective cohort study.ObjectiveThis study aimed to investigate the relationship between preoperative cervical sagittal alignment and postoperative kyphosis in patients with cervical spondylotic myelopathy (CSM) and to determine the cut-off angle for predicting the postlaminoplasty kyphosis.Summary Of Background DataThere have been several reports describing a cervical kyphosis after laminoplasty. However, there has been no study on the cut-off angle for predicting the postoperative kyphosis in a large series of patients with CSM.MethodsA total of 1025 consecutive patients with CSM (642 men and 383 women; mean age, 64.4 yr; range, 23-93 yrs) who underwent laminoplasty were included. The average follow-up period was 30.0 months. Radiography was performed before the surgery and at final follow-up. The cervical alignment with neutral view was measured by using the Cobb method. An alignment of C2-7 lordotic angle more than 0° was defined as lordosis and C2-7 lordotic angle less than 0° was defined as kyphosis. The incidence of postoperative kyphosis was evaluated on lateral radiographs.ResultsIn all patients, the mean C2-7 alignment in the neutral position was 11.5° lordotic before surgery and 14.2° lordotic at final follow-up. In the patient without preoperative kyphotic alignment, receiver operating characteristic curve of preoperative C2-7 lordotic angle showed 7° as a predictor for the postlaminoplasty kyphosis (area under the curve  = 0.75, P < 0.0001). Among the preoperatively 720 patients with lordosis more than 7°, postoperative kyphosis was observed in 20 patients (2.8%), whereas in the preoperatively 191 patients with lordosis less than 7°, postoperative kyphosis was seen in 28 patients (14.7%).ConclusionThe cut-off value of preoperative C2-7 lordotic angle for predicting the postlaminoplasty kyphosis was 7° in CSM patient without preoperative kyphotic alignment.Level Of Evidence3.

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