RADIOGRAPHIC ANALYSIS OF AN INVESTIGATIONAL HYDROXYAPATITE-COATED TOTAL HIP-REPLACEMENT

RATIONALE AND OBJECTIVES. The impetus to discover cement-less techniques for fixing implants to bone is the result of the high failure rates of cemented arthroplasty in young, active patients. The application of hydroxyapatite (HA) to implants represents an alternative. The purpose of this investigation is to define the early radiographic pattern of an HA femoral stem and compare this definition with an identical stem without the HA treatment. METHODS. Radiographic analysis was performed on 98 hips: 63 HA stems and 35 non-HA stems, with a 1-year follow-up. Radiographic parameters analyzed included: 1) radiolucent line formation; 2) endosteal bone formation; 3) calcar response; 4) periosteal bone formation; 5) heterotopic bone formation; 6) stem subsidence; and 7) quality of fit. RESULTS. The HA stem demonstrated greater proximal endosteal sclerosis and distal radiolucency (P < .001). The non-HA (control) stem demonstrated greater proximal and distal radiolucency (P < .02) and distal endosteal sclerosis (P < .001). CONCLUSION. The HA pattern suggests proximal load transference and bony fixation. The control pattern suggests distal loading and fixation, in addition to motion between the stem and native femur. These patterns indicate an advantage of the HA fixation over traditional implants.