Quantitative analysis of the degeneration of cervical spine and the correlation to the heterotopic ossification after artificial cervical disc replacement

Abstract

Objective: To investigate parameters related to quantifying the amount of degeneration in preoperative patients to identify ideal indication of artificial cervical disc replacement (ACDR) in patient with a minimum of 10 years of follow-up data. Methods: From January 2004 to August 2008, a total of 44 patients underwent single level Bryan cervical disk replacement performed by the same group of surgeons were involved in this retrospective study, and all of the patients in this group had at least 10 years of follow-up data. Heterotopic ossification (HO) was graded in radiographic images by using the McAfee classification. Preoperative degeneration of cervical spine was evaluated in radiographs based on a quantitative"9 points"scoring system. Univariate analysis and multifactor logistic regression were made to identify significant factors. To determine the cut-off points for the significant factors, a receiver operating characteristic (ROC) curve analysis was conducted. Results: The incidence of HO in study group was 61.4%. Based on univariate analysis results, there were significant differences in the scores of disc height, the presence of anterior osteophytes and endplate sclerosis between the HO group and non-HO group (all P<0.05), and the indices were included in the multivariate analysis. According to the logistic regression results, disc height and endplate sclerosis were identified as the independent risk factors for HO(OR(95%CI): 10.801(1.202-97.064), 37.870(1.581-907.237), respectively, both P<0.05). ROC analysis showed the area under the curve (AUC) of disc height and endplate sclerosis were 0.822 and 0.792, respectively. According to the scoring system, the ROC curve indicated that both the optimal cutoff points were 1.5. Conclusion: The incidence of postoperative HO is relatively high among the patients who had more than 10 years follow-up, and the amount of degeneration in the target level before surgery correlated with the incidence of HO.