Cervical Artificial Disc Replacement With Discover Prosthesis Does Not Reduce the Midterm Risk of Heterotopic Ossification: Results of a Cohort Study

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Study Design:A prospective cohort study with 79 patients.Objective:To analyze the midterm incidence of heterotopic ossification (HO) after cervical artificial disc replacement with Discover prosthesis in treatment of cervical degenerative disc disease.Materials and Methods:A cohort of 79 patients with 102 Discover prostheses (56 monosegment and 23 bisegments) was evaluated. Clinical and radiographic follow-up was performed. The performance of HO of the operative segments was assessed annually after the operation for 4 years.Results:Early follow-up at 2 years postsurgical treatment showed satisfactory clinical outcomes. No significant changes on the mean Japanese Orthopaedic Association and Visual Analog Scale scores were detected at 3 and 4 years postoperation. The occurrence rate of HO was 5.9% in 1-year follow-up and 17.6% in 2-year follow-up, and then the percentages increased to 49.2% in 3-year follow-up and 65.6% in 4-year follow-up, respectively. No association between the HO grades and the type of the surgical segment was detected by the Fisher exact test (P-value=0.56). No prosthesis subsidence or excursion was identified during the whole follow-up period.Conclusions:The use of Discover prosthesis resulted in satisfactory clinical outcomes after operation. However, the new prosthesis did not reduce the midterm risk of HO, despite the fact that the observed incidence was relatively low in the early follow-up.

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