• Lingyun Hu, Jianying Zhang, Hao Liu, Yang Meng, Yi Yang, Guangzhou Li, Chen Ding, and Beiyu Wang.
• Department of Orthopedic Surgery, West China Hospital, Sichuan University, No. 37 Guo Xue Xiang, Chengdu, 610041, Sichuan, China.
• Eur Spine J. 2019 Oct 1; 28 (10): 2359-2370.

PurposeTo investigate the influence of the immediate post-operative change in disc space angle relative to preoperation on heterotopic ossification (HO) occurrence following cervical disc arthroplasty (CDA) and on clinical and radiographic outcomes.MethodsEighty-four patients with single-level Prestige-LP arthroplasty were retrospectively reviewed. HO was assessed based on McAfee classification. Radiological parameters, including index disc space angle (DSA), functional spinal unit angle, cervical lordosis, segmental range of motion (SROM), migration and subsidence of the prosthesis, prosthesis-endplate coverage ratio, and complications, were evaluated. Clinical features and outcome scores were also evaluated.ResultsA significant association between immediate post-operative DSA change and HO occurrence was found. Patients with a more than 5° increase in immediate post-operative DSA lordosis had a significantly higher incidence of HO and more severe HO than patients with a less than 5° DSA increase after CDA. No correlation was observed between clinical outcomes and post-operative DSA increase or HO occurrence. Both groups maintained cervical sagittal alignment. However, patients with a more than 5° DSA increase exhibited larger anterior migration amount and lower prosthesis-endplate coverage ratio compared to a less than 5° increase in DSA, and more lordotic DSA and less SROM at the final follow-up compared with those at preoperation. No significant difference in other complications was found between the groups.ConclusionPatients with a more than 5° increase in immediate post-operative DSA showed adverse effects on HO formation. Overcorrected DSA was associated with poor prosthesis stability, inadequate endplate coverage, and limited SROM, although it did not affect the clinical outcomes. These slides can be retrieved under Electronic Supplementary Material.

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