Hydroxyapatite granules interposed at bone-cement interface in total hip replacements: Histological study of retrieved specimens

The effect of hydroxyapatite (HA) granules interposed between bone and poly methy methylmethacrylate (PMMA) bone cement in total hip replacement was hi stologically evaluated, The technique consisted of smearing 2-5 g of HA, gr anules (phi = 100-300 mu m) onto the hone surface just before cementing. Fo ur specimens containing well-fixed bone-cement interface were retrieved at 1, 2, 6, and 10 years postoperatively and examined with back-scattered elec tron microscopy and light microscopy. The majority of HA granules were inco rporated into remodeled trabeculae and highly convoluted bane-cement interf ace was maintained up to 10 years. The presence of active remodeling in the adjacent bone was observed. There was no significant inflammatory or forei gn body reactions against interposed HA granules, In one specimen retrieved from a patient with rheumatoid arthritis, bone formation around HA granule s was limited after 1 year. These results have provided histological eviden ce for the significantly reduced incidence of radiolucent lines in total hi p replacement with this cementing technique, reported elsewhere. (C) 2000 J ohn Wiley & Sons, Inc.