Concise report doi:10.1093/rheumatology/keu253 Bone and cartilage metabolism markers in synovial fluid of the hip joint with secondary osteoarthritis

Objective. The aim of this study was to compare the levels of bone and cartilage metabolism markers in the synovial fluid of the hip joint between patients with secondary OA due to osteonecrosis of the femoral head (ONFH), rapidly destructive arthrosis (RDA) and developmental dysplasia of the hip (DDH). Methods. We studied 70 synovial fluid samples obtained from 57 patients with ONFH (mean age 46 years, 34 males, 23 females), 21 samples obtained from 21 patients with RDA (mean age 70 years, 2 males, 19 females) and 20 samples obtained from 20 patients with DDH (mean age 56 years, 2 males, 18 females). The levels of bone alkaline phosphatase (BAP) and tartrate-resistant acid phosphatase 5b (TRACP-5b), as bone metabolism markers, and matrix metalloproteinase 3 (MMP-3) and keratan sulphate (KS), as cartilage metabolism markers, were analysed. Results. The levels of BAP, MMP-3 and KS were significantly higher in the ONFH group than in the RDA and DDH groups. The levels of TRACP-5b were highest in the RDA group. The levels of BAP in the ONFH group after the development of osteoarthritic changes were significantly lower than those observed in earlier stages. In comparisons between the samples obtained from each group with a terminal condition, the ONFH samples exhibited significantly higher MMP-3 and KS levels, while the TRACP-5 levels were highest in the RDA group. Conclusion. The ONFH patients showed a relatively bone formative condition before the osteoarthritic stage and maintained a higher rate of cartilage turnover throughout several stages compared with the RDA and DDH patients. RDA patients were characterized by a significantly high osteoclast activity. Key words: hip osteoarthritis, osteonecrosis of the femoral head, rapidly destructive arthrosis, developmental dysplasia of the hip, synovial fluid analysis, bone metabolism marker, cartilage metabolism marker