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.

中文翻译：

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颈椎间盘置换术与颈前路椎间盘切除融合术治疗单节段椎间盘退行性疾病合并术前可逆性脊柱后凸

目的 颈椎间盘置换术 (CDA) 是否以及何时可用于术前颈椎后凸畸形尚不清楚。本研究的目的是比较单节段 CDA 和单节段颈前路椎间盘切除融合术 (ACDF) 在术前可逆性后凸畸形患者中的临床和影像学结果。患者与方法 2014-2018 年，连续回顾了接受单层 CDA 和单层 ACDF 的患者。日本骨科协会评分、颈部残疾指数和 VAS 用于评估临床结果。评估了运动范围 (ROM)、C2-7 Cobb 角、功能性脊柱单位 (FSU) 角和异位骨化 (HO)。结果 38 名 CDA 患者（平均随访 39.8 个月）和 42 名 ACDF 患者（37. 6个月）术前可逆性后凸畸形被包括在内。两组的临床结果都有显着改善，没有统计学上的显着差异。术前，各组颈椎对线和ROM无显着差异。手术后，两组C2-7角和FSU均显着增加，无显着组间差异。末次随访时，CDA组前凸5例，后凸11例，脊柱直22例，ACDF组相应病例数为4、12、26例（P=0.866）。两组都保留了 C2-7 ROM。CDA组的节段ROM从术前的8.3°轻度下降到最终的5.1°，而ACDF组的节段ROM明显下降到接近于零。60. CDA组5%（23/38）患者发生HO，Ⅲ级9个，Ⅳ级3个。结 在颈椎对线的放射学结果方面，CDA 不劣于 ACDF。CDA组患者HO形成率相对较高。