Cervical disc arthroplasty versus anterior cervical discectomy and fusion for the treatment of single-level disc degenerative disease with preoperative reversible kyphosis

Objective: Whether and when cervical disc arthroplasty (CDA) could be indicated for preoperative cervical spine kyphosis is unclear. The purpose of the study was to compare the clinical and radiological outcomes of single-level CDA and single-level anterior cervical discectomy and fusion (ACDF) in the patient with preoperative reversible kyphosis.

Patients and methods: From 2014-2018, patients who underwent single-level CDA and single-level ACDF were consecutively reviewed. The Japanese Orthopedic Association score, Neck Disability Index and VAS were used to evaluate clinical outcomes. Range of motion (ROM), C2-7 Cobb angle, functional spinal unit (FSU) angle, and heterotopic ossification (HO) were assessed.

Results: Thirty-eight CDA patients (a mean follow-up of 39.8 months) and 42 ACDF patients (37.6 months) with preoperative reversible kyphosis were included. Both groups had significant improvements in clinical outcomes, without statistically significant differences. Before surgery, there was no significant difference in cervical alignment and ROM between groups. After surgery, both groups had a significant increase in C2-7 angle and FSU without significant inter-group differences. At the last follow-up, CDA group consisted of 5 cases of lordosis, 11 cases of kyphosis and 22 cases of straight spine, while the corresponding case number in ACDF group was 4, 12 and 26 (P = 0.866). The C2-7 ROM was preserved in both groups. The segmental ROM of CDA group decreased mildly from 8.3° preoperatively to 5.1° finally, whereas the segmental ROM of ACDF group decreased significantly to nearly zero. 60.5 % (23/38) patients in CDA group developed HO with 9 levels of grade Ⅲ and 3 levels of grade Ⅳ.

Conclusion: For the patients with single-level disc degenerative disease and preoperative reversible kyphosis, both CDA and ACDF achieved satisfactory and comparable clinical results. CDA was non-inferior to ACDF regarding the radiological outcomes of cervical alignment. Patients in CDA group had a relatively high incidence of HO formation.

Keywords: ACDF; Cervical disc arthroplasty; Heterotopic ossification; Reversible kyphosis.