Impact of Cervical Spine Deformity on Preoperative Disease Severity and Postoperative Outcomes Following Fusion Surgery for Degenerative Cervical Myelopathy: Sub-analysis of AOSpine North America and International Studies.

STUDY DESIGN: Sub-analysis of the prospective AOSpine CSM North America and International studies.

OBJECTIVE: The aim of this study was to investigate the impact of cervical spine deformity on pre- and postoperative outcomes in fusion surgeries for degenerative cervical myelopathy.

SUMMARY OF BACKGROUND DATA: The associations between cervical alignment and patient outcomes have been reported but are not well established in a myelopathy cohort. The impact of deformity correction in this population also needs to be elucidated.

METHODS: A total of 757 patients were enrolled in two prospective international multicenter AOSpine studies. Among those who underwent anterior or posterior fusion surgeries, pre- and 1-year postoperative upright neutral lateral radiographs of cervical spine were investigated to measure C2-7 Cobb angle and C2-7 sagittal vertical axis (SVA). Patient outcome measures included the modified Japanese Orthopedic Association score for myelopathy severity, Neck Disability Index (NDI), and Short-form 36 (SF-36). These scores were compared between patients with and without cervical deformity, which was defined as C2-7 Cobb >10° kyphosis and/or SVA >40 mm.

RESULTS: A total of 178 patients were included with complete pre- and postoperative radiographs. SVA significantly increased postoperatively (27.4 vs. 30.7 mm, P = 0.004). All outcome measurement showed significant improvements above minimal clinically important differences. 23.6% of the patients had cervical deformity preoperatively; preoperative deformity was associated with worse preoperative NDI scores (45.7 vs. 38.9, P = 0.04). Postoperatively, those with deformity exhibited significantly lower SF-36 physical component scores (37.2 vs. 41.4, P = 0.048). However, when focusing on the preoperatively deformed cohort, we did not find any significant differences in the postoperative outcome scores between those with and without residual deformity.

CONCLUSION: There was a significant association between cervical deformity and both preoperative disease severity and postoperative outcomes; however, no impact of deformity correction was shown.

LEVEL OF EVIDENCE: 2.