Faculty Bibliography

We reviewed the clinical and radiographic results of a series of 215 consecutive hip arthroplasties in which a normalized, proportionalized, cemented femoral component was implanted. This component design may encourage more efficient force transmission from prosthesis to cement to bone and lessen hoop stresses and resultant interface failure. A total of 127 hips in 103 patients with a follow-up of 13 to 17 years (average, 14.8 years) were available for evaluation, which included survivorship analysis. An aseptic failure loosening rate of 3.9% at 15 years for this stem favorably compares with other reported series of first-generation and second-generation stems at similar follow-up. Excluding the 8 stems placed in varus, of which 3 required revision (failure rate, 37.5%), the series has a failure rate of 1.6%

The effect of implant-bone bonding and the effect of implant surface roughness on bone remodeling near the bone-implant interface were studied by using a surface remodeling theory and the boundary element method. The study has shown that implant attachment plays an important role in bone remodeling near the implant. It has been observed in animal experiments and in clinical situations that the remodeled trabecular bone architecture around a cylindrical implant could vary, on one hand, from a hub surrounding the implant with a set of external spokes to, on the other hand, a hubless situation in which a set of spokes attach directly to the implant. It is shown here that the difference in these structures may be attributed to differences in implant attachment. The results show that the bone with perfect bonding or roller boundary condition without a gap remodeled to a hubless spoke trabecular bone architecture. On the other hand, the roller boundary condition with a specified gap yielded a spoke trabecular architecture with a hub or ring surrounding the implant. These quantitative results mirror the experimental and clinical observations. It is concluded that the hub is a consequence of the gap and not a consequence of the lack of friction between the implant and the bone.

Thirty patients (60 hips) who underwent simultaneous bilateral total hip arthroplasty with hydroxyapatite components were followed from 24 to 78 months (mean: 49 months). All patients showed improvement in postoperative hip score rating compared to preoperative for pain, function, and range of motion. Postoperative complications were minimal compared to other series. There were no thromboembolic complications. Heterotopic bone was noted in 18 hips (30%). At latest follow up no patients had radiographic evidence of component loosening

Uncemented porous-coated cobalt-chrome femoral stems have produced satisfactory short-term clinical results, although slightly inferior to the results of cemented total hip arthroplasty. Proximal femoral bone resorption, osteolysis and fibrous ingrowth have been reported with porous-coated stems. Hydroxyapatite-coated stems and titanium stems have been introduced to avoid these findings through improved fixation. Dual-energy x-ray absorptiometry allows quantitative examination of bone density changes after uncemented total hip arthroplasty. This study examines the host-bone response to hydroxyapatite-coated titanium and porous-coated cobalt-chrome stems of identical geometry in three paired bilateral cases at 5 to 7 years. Distinctly different patterns of femoral bone mineral density changes were observed with the two stem designs. The authors conclude that dual-energy x-ray absorptiometry is a promising technique allowing noninvasive analysis of uncemented stem fixation, and that the data from this study suggest improved fixation and stress transfer with hydroxyapatite-coated titanium stems.

A retrospective study was undertaken to determine the intraoperative blood loss and the subsequent need for blood transfusion in primary total knee arthroplasty. Fifty-six patients were operated on with the use of an arterial tourniquet (group 1), and 50 patients, without the use of a tourniquet (group 2). The mean intraoperative blood loss was significantly different between the two groups (P = 0.001). The 1-hour postoperative hemoglobin decrease was also significantly different between the two groups (P = 0.006). Thirty-four patients (61%) in group 1, and 32 patients in group 2 (64%) required a blood transfusion prior to discharge from the hospital. This difference was not significantly different. Although intraoperative blood loss was increased in the group when no tourniquet was used, the overall incidence of transfusion was the same between the two groups. It may therefore be justified to question the routine use of a tourniquet during total knee arthroplasty.

Two hundred fifteen cemented total hip arthroplasties were performed in 184 patients using normalized and proportionalized femoral stems. Normalization or stepped tapering of the stem minimizes development of tensile hoop stresses by altering force transmission from the femoral stem to the cement mantle. The proportionality of the stem was based on an anatomic study that resulted in the development of a series of prostheses achieving a more complete femoral canal fill. Patients were followed clinically and radiographically from 8 to 12 years or until revision. Average hip scores (d'Aubigne and Postel) improved for pain (3.0-5.9), function (2.9-5.5), and motion (3.3-5.5). Radiographic results demonstrated a 4% incidence of loosening, a 16% incidence of cortical hypertrophy, and no femoral stem fractures. Revision rate was 3%. These results support use of this device.

Tissue specimens retrieved from four regions adjacent to hip implants during revision surgery were subjected to a novel treatment to make possible the quantitative separation of residual metal particulates and metal reaction products (metal ions and metal-protein complexes). The tissues were exposed to sodium hypochlorite solution that degraded and solubilized them, liberating metal reaction product and leaving behind metal wear particles, which were separated by centrifugation. Atomic absorption spectrophotometry was used to analyze the concentrations of the separated metal ions and wear particles. Co ion concentrations were 0.05 to 0.9 mM, Cr ion concentrations were 0.04 to 2.1 mM, and of Ti ion concentrations were 0.30 to 0.60 mM. The weight of Co metal particles was 0.1 to 4.9 mg/100 mg tissue, of Cr metal particles 0.07 to 2.2 mg/100 mg of tissue, and Ti particles 0.09 to 5.2 mg/100 mg tissue; one black tissue sample contained 3333 mg Ti/100 mg tissue. No correlation was found between the concentrations of these two entities in the samples examined, probably due to the complex and varied processes creating them. The procedures discussed here will result in data that can help elucidate the separate contributions of metal reaction products and metal particulates to implant loosening.

Although the long-term clinical results of cemented total hip arthroplasty are quite good, there is a significant problem with failure after approximately 10 years, especially with younger patients. Uncemented total hip arthroplasty has been developed in response to prosthesis loosening due to cement fragmentation and osteolysis. Porous-coated hip stems have been used, with generally promising results. However, clinical studies of porous-coated prostheses have revealed findings of concern such as thigh pain, subsidence of the femoral prosthesis, and radiographic lucencies at the bone-prosthesis interface. Hydroxyapatite coatings were developed to improve the fixation of uncemented prostheses. This article discusses the chemical, mechanical, and biological properties of hydroxyapatite coatings, and reviews the biologic behavior of experimental hydroxyapatite-coated implants. The clinical and radiographic results of a 4-year prospective trial are presented. The authors conclude that the reported experimental evidence, as well as the early clinical experience of this series and others, support the continued clinical evaluation of hydroxyapatite-coated titanium for total hip arthroplasty in younger, active patients.