Monocyte chemoattractant protein 1 expression in synovial fluid of patients with total hip arthroplasty

Monocyte chemoattractant protein 1 (MCP-1) is a member of the chemokines family that stimulates monocyte chemotaxis and whose expression is induced during osseous inflammation. Total hip arthroplasty (THA) now uses ceramic-on-ceramic (cer-cer) or metal-on-metal (met-met) coupling that is considered the bearing of new generation, with improved performance compared with the previous polyethylene bearings. While the ceramic on ceramic is universally considered highly biocompatible, met-met coupling can induce hypersensitivity correlated to immunological response. This study aimed at quantifying the MCP-1 levels in synovial fluid of THA patients with these two articular couplings; synovial fluid of osteoarthritic patients who underwent primary THA was used as a control. The presence of wear particles originating from the prostheses was also assessed in the synovial fluid by scanning electron microscopy and energy dispersive X-ray spectroscopy. The MCP-1 levels in the synovial fluid of 17 patients with met-met coupling were significantly higher than in 13 patients with cer-cer coupling and in seven controls; median MCP-1 level was 919 pg/mL in the cer-cer group, 4274 pg/mL in the met-met group, and 326 pg/mL in the control group. No correlation was found between MCP-1 levels and the presence of wear particles in the synovial fluid, time from surgery, or periprosthetic osteolysis. We conclude that the presence of the prosthesis is responsible for an increase in the level of MCP-1; moreover, the significantly higher level of this chemokine in met-met coupling can be related to inflammatory and possibly hypersensitivity processes induced by metal ions.