Biochemical markers of bone turnover and development of heterotopic ossification after total hip arthroplasty

We studied biochemical markers of bone turnover markers in 20 men and women over 26 weeks after total hip arthroplasty (THA) in order to characterize the changes in bone metabolism associated with developing heterotopic ossification (HO). Transient increases in biochemical markers of both osteoclast and osteoblast activity occurred after surgery. Subjects developing HO (n=9) had greater rises in the osteoclast marker C-telopeptide of type-I collagen (CTX-I; ANOVA P=0.004), and the osteoblast markers N-terminal propeptide of type-I procollagen (PINP; ANOVA P=0.01) and osteocalcin (OC; ANOVA P=0.02) than those who did not develop HO. A rise of >42% in CTX-I at one week after surgery had a sensitivity of 89% and a specificity of 82% for predicting HO development at week 26 (P<0.05). Rises of >57% in PINP and >13% in OC at week 6 had sensitivities of 89% and 56%, and specificities of 82% and 91%, respectively for development of HO. Transient increases in osteoblast and osteoclast activity occur after THA. These changes are greater in patients developing HO than in those who do not develop HO. The potential applications of these markers are as a non-invasive, radiation-free tool for investigating the pathogenesis of HO, and as an early surrogate outcome marker for HO development in clinical trials of novel prophylaxis regimes for its prevention.