EARLY FAILURE OF HYDROXYAPATITE-COATING IN TOTAL KNEE ARTHROPLASTY - A CASE-REPORT

We observed early loosening of a hydroxyapatite-coated tibial componen t in a total knee arthroplasty in a randomized study comparing HA-coat ing with cement fixation. Symptoms of loosening started 8 weeks after surgery. Roentgen stereophotogrammetric analysis revealed stability du ring the initial 6 weeks followed by a pronounced subsidence up to 6 m onths after surgery when revision was done. At revision, the HA-coatin g was found to have separated from the medial part of the tibial compo nent. The synovium was abundant with macrophages and multinucleated gi ant cells containing HA-crystals. Overloading of the prosthesis and su boptimal quality of the HA-coating was believed to have caused the loo sening process.