The time course of cervical alignment after cervical expansive laminoplasty: Determining optimal cut-off preoperative angle for predicting postoperative kyphosis.

Retrospective Cohort studyTo analyze cervical lordosis angle (CLA) change after cervical expansive laminoplasty (CEL) over time, and to determine optimal cut-off angle for predicting postoperative kyphosisPostoperative development of sagittal malalignment after laminoplasty is associated with neurological dysfunction and neck pain. However, there is no information on the serial CLA change over time and cut-off angle for predicting postoperative kyphosisThe Cobb angle between C2 and C7 in a series of lateral cervical X-rays in the neutral position was retrospectively reviewed for 36 months. And, the effect of time on CLA after CEL and the risk factors associated with postoperative cervical kyphosis (Cobb's angle ≤0°) were analyzed. Also, the optimal cut-off angle for predicting postoperative kyphosis was determined.A total of 110 cases of CEL for cervical myelopathy were enrolled from February 2005 to May 2010. The mean cervical alignment changed from 12.3 ± 10.4° (mean ± standard deviation [SD]) at the preoperative evaluation to 8.2 ± 11.6°, 10.6 ± 10.1°, 9.1 ± 10.0°, 8.4 ± 11.2°, 8.5 ± 10.5°, 8.1 ± 9.9°, and 8.7 ± 10.1° at 1, 3, 6, 12, 18, 24, and 36 postoperative months, respectively. The cervical lordosis showed statistically significant decreased at the 1st month, then the lordotic angle was partially restored at the 3rd, and 6th, and then no significant changes after the 6th. The only risk factor for kyphosis development was the preoperative CLA. The optimal cut-off preoperative angle for predicting postoperative kyphosis was 8.5°.The decrease of CLA after expansive laminoplasty peaked in the 1st month. Some of the lordotic angles were restored in the 3rd and 6th months, before reaching a plateau after the 6th month. The optimal cut-off preoperative angle for predicting postoperative kyphosis was 8.5°.Level of Evidence of their study: Level 4.