One concern about the fixation of HA-coated implants is the possible disintegration of the surface, with the migration of HA granules into the joint space, producing third-body wear. We report a study of six revisions of HA-coated polyethylene RM cups at 9 to 14 years after successful primary arthroplasty. In all six hips, we found HA granules embedded in the articulating surface of the polyethylene, with abrasive wear of the cup and the metal femoral head. The cup had loosened in four hips and three showed severe osteolysis of the proximal femur. Third-body wear due to HA particles from implant coating may produce severe clinical problems with few early warning signs. Further clinical, radiological and histological observations are needed to determine the possible incidence of this late complication in the various types of coating of a variety of substrates.
We reviewed the results of 545 consecutive total hip replacements using a cementless non-coated high-density polyethylene acetabular component combined with a cemented Muller stem at five to 10 years. In all, 421 patients (445 hips) were available for review, 118 by questionnaire and 303 by examination and radiography. Of these, 86% had a good or excellent result. We found a high rate of radiological loosening of the cup after the sixth year, and a high rate of clinical loosening after the eighth year. Loosening was commoner in women, in younger patients and where a smaller size of acetabulum had been used. Calcar resorption was significantly related to loosening of the acetabulum. Loosening appeared to be mainly due to polyethylene debris produced by micro-movement of the acetabulum against the bone, which had resulted in a giant cell foreign body reaction and subsequent bone erosion. We have abandoned the use of this prosthesis and suggest that direct contact between bone and polyethylene should be prevented by a coating of metal or some other material.
Sixty-two patients presented with an infected total hip arthroplasty. Their management depended on their general medical condition, the clinical signs of infection, the type of infection, the degree of fixation of the components and the available bone stock. Treatment consisted of one of the following: debridement and lavage without removing the prosthesis, one or two stage revision arthroplasty, or excision arthroplasty. There were 11 early and 51 late infections. The commonest bacterium isolated was Staphylococcus epidermidis (30%). Primary revision of the femoral component was slightly more successful with a cemented prosthesis than with an uncemented prosthesis. The overall success rates for cemented and uncemented femoral components were roughly comparable (91.5%:90%). We make various recommendations for the management of infected total hip arthroplasties based on our experience.
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