Purpose of the study: Because of the growing number of aseptic loosening of total hip arthroplasty (THA), a reliable biological marker would be useful to diagnosis osteolysis early and non-invasively while avoiding the risk of false positives. The purpose of this study was to analyse the value of the interleukin-10(IL10)-alphaTNF ratio in serum and synovial fluid as a marker of THA aseptic loosening.

Material and methods: Blood synovial fluid samples were collected in 27 volunteers with a cemented THA (group THA) and 30 healthy subjects comparable for age and gender who were programmed for total hip arthroplasty because of primary osteoarthritis (group OA). We analysed: locally by the level of alphaTNF and IL10 in the supernate of differentiated THP-1 with and without adjunction of synovial fluid (SF); in the bloodstream the production of alphaTNA and IL10 by monocytes; the correlation between serum and SF levels and the presence or not of loosening.

Results: In the THA group, SF induced a relative decrease in IL10 strangly not associated with an increase in alphaTNF. However, the IL10/alphaTNF ratio was significantly lower in the OA group. Circulating monocytes produced more alphaTNF in the THA group while there was no significant difference in the production of IL10 by the two groups. However, the IL10/alphaTNF ratio was significantly higher (2-fold) in the THA group. Regarding serum cytokine levels, there was a local accumulation of alphaTNF in the THA group and IL10 in the OA group.

Discussion: The IL10/alphaTNF ratio alone was significantly correlated with aseptic loosening, locally and in the general bloodstream. IL10 or alphaTNF did not alone correlate in all conditions. These results show that use of this ratio appears to be more effective than assay of a single proinflammatory cytokine for the early diagnosis of aseptic loosening. The validity of this ratio is supported by its local and general correlation. A comparative prospective study in healthy subjects using a non-invasive method (except for the blood samples) should be conducted to confirm the clinical pertinence of this marker.