Hydroxyapatite-coated femoral stems - Histology and histomorphometry around five components retrieved at post mortem

We performed a histological and histo-morphometric examination in five cada ver specimens of the femoral and acetabular components and the associated t issue which had been recovered between 3.3 and 6.2 years after primary tota l hip arthroplasty (THA) using a proximal hydroxyapatite HA)-coated titaniu m alloy implant. All had functioned web during the patients' life. All the stems were fixed in the femur and showed osseointegration of both t he proximal and distal parts. The amount of residual HA was greatest. in th e distal metaphyseal sections, indicating that the rate of bone remodelling may be the main factor causing loss of HA. The level of activity of the pa tient was the only clinical factor which correlated with loss of coating. T he percentage of bone-implant osseointegration was almost constant, regardl ess of the amount of HA residue, periprosthetic bone density or the time of implantation. HA debris was seldom observed and if present did not cause a ny adverse or inflammatory reaction. Partial debonding did occur in one cas e as a result of a polyethylene-induced inflammatory reaction.