Clinical and radiological outcomes of single-level cervical disc arthroplasty in the patients with preoperative reversible kyphosis: A matched cohort study.

OBJECTIVE

The performance of cervical disc arthroplasty (CDA) in the spine with malalignment was unclear. The purpose of the study was to report the clinical and radiological outcomes of single-level CDA in the patients with preoperative reversible kyphosis (RK) and compare these results with a matched cohort of preoperative lordosis.

PATIENTS AND METHODS

From 2014 to 2018, 36 patients with preoperative RK were matched with 229 patients with preoperative lordosis. The Japanese Orthopedic Association score, Neck Disability Index, Visual Analog Scale were used to evaluate clinical outcomes. Radiological evaluations included range of motion (ROM), C2-7 Cobb angle, shell angle (SA) at surgical level, functional spinal unit (FSU) angle and heterotopic ossification (HO).

RESULTS

The mean follow-up was 40.1 months. Both groups achieved significant improvements in clinical outcomes without significant intergroup differences. Before surgery, lordosis group had significantly greater C2-7 angle (9.5° vs -8.4°), SA (1.6° vs -3.7°), and FSU (2.9° vs -3.7°). After surgery, RK group experienced significant improvements in C2-7 angle and SA compared with preoperative data. In lordosis group, C2-7 angle, SA, and FSU were maintained. At the last follow-up, the intergroup difference of C2-7 angle, SA, and FSU remained significant. ROMs were preserved in both groups. The ROM of RK group was slightly lower than that of lordosis group but failing to reach a significance. Eleven patients in lordosis group and 21 patients in RK group developed HO (P = 0.127). There was a significant greater incidence of high-grade HO (grade Ⅲ, Ⅳ) in RK group (33.3 % vs 11.1 %, P = 0.034).

CONCLUSION

Both groups achieved satisfactory and comparable clinical outcomes after CDA. Despite the remarkable improvements compared with preoperative values, the cervical alignment of RK group was still significantly inferior to that of lordosis group. More HO formation occurred in RK group. Based on these results, we did not recommend CDA to the patients with preoperative RK.