The Sagittal Balance of Cervical Spine after Posterior Open-Door Laminoplasty: Comparison between the Modification by Preserving Unilateral Musculoligament Complex and Anchor Method

Abstract

Introduction A balanced sagittal alignment of the spine has been shown to strongly correlate with less pain, less disability, and greater health status scores. The profile of sagittal balance after posterior laminoplasty of cervical spine has not been evaluated extensively. The aim of this study is to investigate parameters of cervical spine sagittal balance after posterior open-door laminoplasty and compare the difference between modified surgery with preservation of unilateral musculo-ligament complex (PUMLC) and anchor method (AM) operation. Materials and Methods A retrospective review of 96 patient records from January 2008 to July 2011 was performed. All patients were diagnosed cervical spondylotic myelopathy (CSM) and underwent C3-7 posterior open-door laminoplasty with preservation of unilateral musculo-ligament complex (5 cases) and anchor method (40 cases). Cervical digital radiographs showed all the important skeletal landmarks necessary for accurate measurement. The radiographs were measured using standard techniques to obtain the following parameters both pre- and postoperation: C2-C7 sagittal vertical axis (C2-C7 SVA), C0-2 lordosis (Cobb angle formed between Occiput-C2), C2-7 lordosis (Cobb angle formed between C2-C7), T1 slope (angle between a horizontal line and the superior end plate of T1), range of motion from C2-C7 (C2-C7 ROM). The status of neurologic function was evaluated by modified JOA score (mJOA). Comparisons of these radiological and neurological assessments before and after surgery and difference between two surgical manipulations were under analysis. Results With an average follow-up period of 16.7 months, there was a significant increase ( p < 0.05) in C2-C7SVA (22.99 ± 1.23 mm), C0-2 lordosis (22.89 ± 0.75 degrees), and T1 slope (25.13 ± 0.67 degrees) postoperatively compared with preoperation (C2-C7SVA 20.82 ± 1.05 mm, C0-2 lordosis 19.56 ± 0.78 degrees, T1 slope 26.22 ± 0.71 degrees). The alignment of lower cervical spine (C2-7 lordosis) did not change significantly after the surgery ( p = 0.09). Both C0-2 lordosis and T1 slope positively correlated with increased C2-C7SVA ( r = 0.44, p < 0.001, and r = 0.27, p < 0.05). All patients experienced an improvement of mJOA (12.23 ± 0.31) compared with pre-op (14.56 ± 0.21). PUMLC had a smaller loss of C2-7 lordosis and C2-7 ROM than AM, but parameters of sagittal balance (C2-C7SVA, C0-2 lordosis, and T1 slope) did not show any statistical significant difference. Conclusion There was a positive sagittal malalignment trend after posterior open-door laminoplasty expressed by enlargement of T1 slope and compensated by increased C0-2 lordosis. Two surgical methods, PUMLC and AM, did not show any statistical significant difference of sagittal balance parameters, but PUMLC had the advantage of maintaining the alignment and range of motion of lower cervical spine. Disclosure of Interest None declared