Hyaluronan in synovial fluid of patients with loose total hip prosthesis. Comparison with hyaluronan in patients with hip osteoarthritis and idiopathic osteonecrosis of femoral head

The concentration and molecular weight of hyaluronan (HA) in the synovial fluid of the hip joint were determined in 13 patients (aged 62.8 ± 9.4 years) who had undergone prior total hip arthroplasty(THA), 23 patients (aged 65.0 ± 8.2 years) with osteoarthritis of the hip joint (OA), and 13 patients (aged 40.2 ± 2.7 years) with idiopathic osteonecrosis of the femoral head (ION). A sample of synovial fluid was obtained during revision THA because of loosening of the total hip prosthesis for the THA group, and during the first replacement surgery or osteotomy for the OA and ION groups. The concentration of HA in the synovial fluid was 0.64 ± 0.42 mg/ml in the THA group, 1.07 ± 0.28 mg/ml in the OA group, and 1.30 ± 0.56 mg/ml in the ION group. The concentration of HA in the synovial fluid of the THA patients was significantly lower than that of the OA and ION patients (P = 0.0156 vs OA, P = 0.003 vs ION). The molecular weight of HA was 309 ± 88.3 x 10⁴ Da in the THA group, 377 ± 201 x 10⁴ Da in the OA group, and 240 ± 148 x 10⁴ Da in the ION group; these values do not differ significantly (P = 0.259 vs OA, P = 0.174 vs ION). Among the THA patients, there was no relation between the concentration of HA and the age of the patient, length of time since the first operation, or type of prosthesis fixation; there was also no relation between the molecular weight of HA and each of these factors. These results suggest that a pseudosynovial membrane is regenerated after THA, and that it produces HA of the same molecular weight as that in patients with OA and ION, although in smaller quantities.