Radiological and clinical long-term results of heterotopic ossification following lumbar total disc replacement

BACKGROUND: The long-term results of heterotopic ossification (HO) following lumbar total disc replacement (TDR) and the corresponding clinical and radiological outcomes are unclear. PURPOSE: This study aimed to report the long-term results of HO following lumbar TDR and to analyze the clinical and radiological outcomes. STUDY DESIGN/SETTING: A retrospective case review was performed for the consecutive patients who underwent lumbar TDR. PATIENT SAMPLE: The study included 48 patients (60 segments) who underwent lumbar TDR. OUTCOME MEASURES: The time and location of HO development, segmental range of motion (ROM) of index level, the visual analog scale (VAS), and the Oswestry Disability Index (ODI) were analyzed. METHODS: Forty-eight patients (60 segments) were divided into HO and non-HO groups, and radiographs were used to measure the time and location of HO development. We compared segmental ROM between two groups using flexion-extension radiographs. Clinical outcomes were assessed using the VAS and the ODI. Furthermore, the segmental ROM, VAS, and ODI scores of each HO class were compared with those of the non-HO group. RESULTS: The mean follow-up duration was 104.4 months. Heterotopic ossification was detected in 30 of 60 segments following lumbar TDR, and HO progression was noted in six segments. The mean segmental ROM was significantly lower in the HO group than in the non-HO group. The mean VAS and ODI scores were not significantly different between the two groups. Segmental ROM was significantly lower in the class III and IV of the HO group than in the non-HO group. The VAS and ODI scores were not significantly different among the different classes. CONCLUSIONS: We found that the incidence of HO is the highest within 12 months after lumbar TDR, and the incidence might increase 5 years after surgery. Furthermore, HO progressed over time. Segmental ROM was decreased in the HO groups; however, the limitation in motion might have little clinical influence. (C) 2017 Elsevier Inc. All rights reserved.