Radiographic analysis of an investigational hydroxyapatite-coated total hip replacement.

RATIONALE AND OBJECTIVES: The impetus to discover cementless 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.

Early clinical experience with hydroxyapatite-coated femoral implants.

As part of a multi-center study, 238 titanium stems that were proximally coated with hydroxyapatite were implanted in 220 patients between January 1988 and December 1989. Ninety-two of these stems in eighty-three patients had a minimum of two years of follow-up, including analysis of the clinical and radiographic data. Clinically, the patients were essentially pain-free before six months and had a low (4 per cent) prevalence of pain in the thigh and a very high composite Harris hip-score (mean, 95 points) at two years. Radiographically, subsidence was detected in 8 per cent of the implants; no implant had more than three millimeters of subsidence. Radiolucencies were characteristically seen around the uncoated distal part of the stem, in 70 per cent of the implants. Contrastingly, radiolucencies were rare in the hydroxyapatite-coated proximal zones and were most often found anteriorly, in only 5 per cent of the implants. Areas of increased formation of cancellous bone were seen beneath femoral cortical bone at the interface between the hydroxyapatite-coated and uncoated parts of the stem, in 67 per cent of the implants. Calcar resorption was found in 49 per cent of the implants. Cortical thickening was present in 17 per cent of the implants at the uncoated distal part of the stem. Two of the 238 femoral implants were revised: one because of infection and one because of aseptic loosening associated with non-union of a subtrochanteric osteotomy.

Topical hemostatic agents for bone bleeding in humans. A quantitative comparison of gelatin paste, gelatin sponge plus bovine thrombin, and microfibrillar collagen.

The three topical hemostatic agents--gelatin paste, microfibrillar collagen, and gelatin sponge soaked in thrombin--individually were effective in reducing bleeding from cancellous bone, as tested on the femoral surface of trochanteric osteotomies during total hip replacement. During a three-minute interval, the spontaneous reduction in bleeding in eight control hips to which no agent was applied was 11 per cent. Gelatin paste gave a reduction of 85 per cent; gelatin sponge soaked in thrombin, a reduction of 75 per cent; and microfibrillar collagen, a reduction of 47 per cent. None of these agents interfered with healing of the trochanteric osteotomy.

Reattachment of the greater trochanter in total hip-replacement arthroplasty. A new technique.

For certian total hip-replacement operations osteotomy of the greater trochanter is essential, and for others it is advantageous. A system of management of trochanter reattachment is described that takes into account multiple factors, such as the need to remove large or small amounts of the trochanter depending on the patient's anatomy and on the style of the femoral component used, the need in some cases to advance the trochanter to lie against the cortex of the femur, the need in other instances to deal with markedly porotic trochanters, and the fact that a small number of the wires will fatigue, regardless of the technique used. The basic technique has one horizontal and two separate vertical wires, all passing medial to the femoral stem and each tied to itself in a square knot; All wires pass through the trochanter to prevent rotation. Wire mesh is used prophylactically if the trochanter is porotic. All patients use two crutches for two months postoperatively; In a consecutive series of 136 total hip replacements in which the trochanter was reattached using this technique, none of the trochanters migrated and all united.