Early failure of hydroxyapatite-coating in total knee arthroplasty. A case report

We observed early loosening of a hydroxyapatite-coated tibial component in a total knee arthroplasty in a randomized study comparing HA-coating with cement fixation. Symptoms of loosening started 8 weeks after surgery. Roentgen stereophotogrammetric analysis revealed stability during the initial 6 weeks followed by a pronounced subsidence up to 6 months after surgery when revision was done. At revision, the HA-coating was found to have separated from the medial part of the tibial component. The synovium was abundant with macrophages and multinucleated giant cells containing HA-crystals. Overloading of the prosthesis and suboptimal quality of the HA-coating was believed to have caused the loosening process.