Heterotopic ossification (HO) is a potential and severe complication of cervical disc replacement (CDR). However, the underlying mechanism of CDR and its association with preoperative disc height loss (DHL) and postoperative degree of distraction (PDD) remain unclear. We hypothesized that DHL and PDD could predict HO after CDR.
Data were obtained from 127 patients who underwent single-level CDR with a minimum follow up of two years. DHL and adjusted degree of distraction (ADD) were obtained from lateral radiographs and HO was evaluated at the last follow up appointment. Receiver operating characteristic (ROC) curves were calculated to verify the diagnostic value of DHL and ADD in predicting HO.
Both DHL and ADD were significantly larger in the HO group than the non-HO group (P<0.05). DHL ≥ 24.97% increased the risk of HO by 5 times (P=0.003, 95% CI: 1.62-15.49), and ADD ≥ 36.67% increased the risk of HO by 3.87 times (P<0.001, 95% CI: 1.81-8.27). A combined DHL and ADD (combined parameter) cut-off of 60.36 had a sensitivity of 87.18%, specificity of 67.35%, and area under the curve of 0.77 for predicting HO.
DHL and ADD are associated with the development of HO after CDR. The cut-off value of DHL may narrow the criteria for CDR with the aim of reducing HO formation. The combined parameter may help surgeons to select the most suitable implant height to reduce the prevalence of HO.

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