Characteristics of bone turnover markers in rapidly destructive coxopathy

The purpose of this study was to clarify bone turnover marker levels in rapidly destructive coxopathy (RDC). Twenty patients with RDC (mean age, 72 ± 11 years; 3 men, 17 postmenopausal women), 111 with osteoarthritis (OA) (age, 60 ± 10 years; 15 men, 13 premenopausal women, 83 postmenopausal women), and 18 with osteonecrosis of femoral head (ON) (55 ± 14 years; 11 men, 3 premenopausal women, 4 postmenopausal women), and 100 patients with femoral neck fracture (FNF) (81 ± 10 years; 27 men, 73 postmenopausal women) were included. Serum tartrate-resistant acid phosphatase 5b (TRACP-5b), bone alkaline phosphatase (BAP), matrix metalloproteinase-3 (MMP-3) levels, and bone mineral density (BMD) of proximal femur and lumbar spine were investigated. TRACP-5b levels were significantly higher in RDC than in OA and ON, whereas BAP levels were higher in RDC than in OA (P < 0.05). MMP-3 levels were higher in RDC and ON than in OA (P < 0.05). TRACP-5b were higher in RDC than OA (P < 0.05) and FNF (P < 0.05) in performing propensity score matching; there were no differences in BMD between RDC and OA. TRACP-5b showed the largest area under the curve (AUC, 0.82) according to receiver operating characteristic (ROC) curve analysis for diagnosing RDC against OA and ON. AUCs of BAP and MMP-3 were 0.78 and 0.74. The respective sensitivities and specificities were 70.0 % and 85.3 % for TRACP-5b (cutoff, 623 mU/dl), 95.0 % and 57.1 % for BAP (13.8 U/l), and 70.0 % and 76.4 % for MMP-3 (52.7 ng/ml). The lack of differences in BMD suggested that high bone turnover marker levels may reflect osteoclast cell activation in RDC hips. Serum TRACP-5b and BAP could be RDC markers.