EXPRESSION OF TENASCIN-C IN ASEPTIC LOOSENING OF TOTAL HIP-REPLACEMENT

Objective - To assess if the bonding interlayer between the implant an d bone in aseptic loosening of total hip, replacement (THR) is qualita tively deteriorated by excessive accumulation of anti-adhesive glycopr otein, tenascin-C. Methods - Alkaline phosphatase-antialkaline phospha tase (APAAP) method was used for immunohistochemical staining of tenas cin-C in interface tissue and control synovial tissue. Results - Tenas cin-C was found to be a major component of the extracellular matrix at a hitherto unrecognised site, namely the synovial membrane-like inter face tissue between implant and bone in aseptic loosening of THR. The overall tenascin-C staining (median score 4.0) was greatly increased i n aseptic loosening compared with synovial membrane (median score 2.0; p < 0.001) and fibrous capsule (median score 2.0; p < 0.001) from pri mary THR operations. Topological analysis disclosed that tenascin-C wa s also found at the critical implant-interface and interface-bone surf aces. Conclusion - Local tenascin-C expression is increased as a resul t of a chronic foreign body type reaction associated with excessive cy tokine production and tissue injury mediated by microtrauma and neutra l endoproteinases. This qualitative and topological deterioration of t he bonding interlayer by an increase of anti-adhesive tenascin-C expre ssion may inadvertantly contribute to loosening.