Changes in the range of motion of the cervical spine and adjacent segments at ≥ 24 months after uninstrumented corpectomy for cervical spondylotic myelopathy

Abstract

Background: Few clinical studies have described the changes in the range of motion (ROM) of the cervical spine and adjacent segments following central corpectomy. We aimed to quantify the changes in range of motion (ROM) of the cervical spine and the adjacent segments at ≥24 months following uninstrumented central corpectomy (CC) for cervical spondylotic myelopathy (CSM) and to determine the contribution of the adjacent segments to the compensation for loss of motion of the cervical spine following CC. Methods: Preoperative and follow-up lateral cervical spine radiographs of 36 patients who underwent CC for CSM between 2001 and 2007 were compared for the ROM of the subaxial cervical spine, superior and inferior adjacent segment. Anterior osteophytes as seen on the radiographs were classified according to Nathan's grading system. Results: The mean duration of follow-up was 48.5 months. At follow-up, the total cervical spine ROM decreased by 18.3^° ± 2.2^° (p < 0.001), the superior adjacent segment ROM increased by 2.3^° ± 0.9^° (p = 0.01) and the inferior adjacent segment ROM, measured in 20 cases, increased by 6.2^° ± 1.7^° (p = 0.01). The superior adjacent segment showed a 70% increase, whereas the inferior adjacent segment showed a 110% increase in mobility. Nathan's grade at the superior or inferior adjacent segment increased in 12 cases. Conclusions: CC significantly reduces the motion of the cervical spine and increases the adjacent segment mobility at intermediate follow-up. The inferior adjacent segment shows greater compensation of motion as compared to the superior adjacent segment in our series. Adjacent segment degeneration as estimated by Nathan's grade was seen in one-third of the cases.