Correlation study between the reason of heterotopic ossification after cervical artificial disc replacement and the degeneration of cervical facet joints

Abstract

Objective To investigate the correlation between the reason of heterotopic ossification after cervical artificial disc replacement and the degeneration of cervical facet joints. Methods From May 2009 to May 2012, 133 patients who had undergone cervical artificial disc replacement were included into this study. There were 74 males and 59 females with an average age of 42.63±4.15 years old (range, 23-56 years old). There were 109 patients who had undergone single level implant, and 24 patients double level implant. Cervical spine A-P and the flexion-extension X-rays were taken to assess the range of motion (ROM) of the surgical level. Degeneration degree of patients' cervical facet joints were evaluated by Park grading standards with the preoperative cervical CT scan images on GE-PACS system. Heterotopic ossification (HO) situation were evaluated by McAfee classification through cervical lateral X-ray film. Patients were divided into two groups (HO group and non-HO group) according to whether heterotopic ossification appeared during the follow-up period. The data were collected before surgery to the latest follow-up. Results The average follow-up time was 2.9 years (range, 2.0-4.8 years). HO was detected in 25 patients (18.80%, 25/133) at latest follow-up. The ROM of surgical level of patients in HO group was significantly lower than non-HO group (6.8°±3.9° vs 9.1°±2.4°). In addition, the degeneration degree of cervical facet joints of patients in HO group was significantly higher than that in non-HO group. There was a significant correlation between preoperative cervical facet joint degeneration and the occurrence of HO after CDR (r=0.683, P=0.033). Conclusion There was a significant correlation between preoperative cervical facet joint degeneration and the occurrence of HO after CDR. Patients present HO after surgery have significantly higher degeneration degree of cervical facet joints than patients without HO. Patients with higher degree of HO may have a higher level of cervical facet joints degeneration. Key words: Cervical vertebrae; Total disc replacement; Ossification, heterotopic