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Adequate endplate coverage by cervical disc prosthesis may reduce risk of heterotopic ossification
WASHINGTON — Data presented here at the American Association of Neurological Surgeons Annual Meeting showed endplate coverage by a cervical disc prosthesis was related to the grade of heterotopic ossification patients developed. Less endplate coverage was also statistically significantly correlated to a higher grade of heterotopic ossification.
According to the study findings Philip A. Utter, MD, FAANS, presented, these results persisted through 5 years of follow-up.
“Less endplate coverage results in higher endplate HO (heterotopic ossification),” Utter said.
The study involved an analysis of HO rates in 389 patients, of whom 164 underwent one-level cervical total disc replacement (CTDR) and 225 underwent two-level CTDR from C3 to C7. The levels treated needed to be contiguous for patients to be included in the study.
Findings were compared with those of control patients who underwent anterior cervical discectomy and fusion (ACDF) at contiguous levels performed with an anterior plate and allograft.
Utter and colleagues at the Spine Institute of Louisiana used the typical HO grading system described by Paul McAfee, MD, in which grades 1 to 2 meant no restricted motion and grades 3 to 4 mean restricted motion due to the presence of HO.
The analysis showed patient age was not related to increases in HO; however, patient BMI was found to have a correlation in certain cases, according to Utter.
“For BMI with one-level total disc replacement, we did find that patients who had a higher BMI were more likely to have heterotopic ossification that caused a restriction of range of motion, but we did not see that in two-level patients.”
By the 5-year follow-up, the researchers found patients’ median HO grade was 2, and endplate coverage was significantly correlated with HO grade, with less endplate coverage correlating to a higher grade of HO. Additionally, median endplate coverage was found to be significantly greater for patients who underwent one-level procedures with HO grades 0, 1 and 2. Although patients who underwent two-level CTDR with HO grades of 0, 1 and 2 were found to have higher endplate coverage, this was not considered significant, according to the researchers.
HO grade was not found to have a significant correlation to Neck Disability Index, VAS for neck pain or SF-12 Physical Composite Scale scores.
Preoperatively, Utter said he often tells his patients about their HO risk so that it is not a surprise.
“For men, the likelihood [they are] going to get clinically significant HO is 10%, and for women it is 5% for one- and two-level. Patient outcome is unaffected by HO for grade 3 and grade 4,” Utter said. – by Susan M. Rapp
Reference:
Utter PA, et al. Paper #734. Presented at: American Association of Neurological Surgeons Annual Meeting. May 2-6, 2015; Washington, D.C.
Disclosure: Utter reports no relevant financial disclosures.