Osteoprotegerin, sRANKL and sRANKL /OPG ratio in pseudosynovial fluid from patients with aseptic loosening of total hip prosthesis

Abstract

Background. Total hip replacement is the final solution in advanced osteoarthritis. The survival time of the implant significantly depends on the condition of the bone in which it has been located. Upsetting the balance in the RANK/RANKL/OPG system can lead to the development of bone metabolic disorders leading to bone loss. The aim of this study was to evaluate the osteoprotegerin (OPG) and soluble RANKL (sRANKL) concentrations in the pseudosynovial fluid in women with aseptic loosening of total hip prosthesis.

Methods. OPG and sRANKL concentrations were assayed in the pseudosynovial fluid collected from 20 women during the revision total hip arthroplasty (THA) (group R), and in the synovial fluid of 13 women in the end-stage of idiopathic osteoarthritis collected during primary THA (group P). OPG and sRANKL were measured using commercially available ELISA kits.

Results. OPG concentration was significantly lower, and sRANKL concentration was significantly higher, in group R than in group P. The sRANKL/OPG ratio in group R was significantly higher than in group P. The average total joint endoprosthesis survival time was 8.6 (SD 3.9) years. The OPG concentration was slightly lower in patients with a time interval shorter than 8.6 years. The sRANKL/OPG ratio was higher in women with a shorter implant survival time.

Conclusion. Higher sRANKL/OPG ratio in the pseudosynovial fluid contributes to increased resorption of bone tissue surrounding total hip endoprosthesis, leading to its aseptic loosening.