Arthroplasty-associated malignant fibrous histiocytoma: two case reports.

AIMS: Sarcoma localized to the site of an arthroplasty procedure is a rare occurrence, and detailed histological depictions and descriptions are limited. We report the clinicopathological findings in two cases of arthroplasty-associated malignant fibrous histiocytoma (MFH) and review the literature. METHODS AND RESULTS: The patients were an elderly man and woman. Medical histories, radiographs and slides were reviewed. Immunohistochemistry, electron microscopy, cytogenetics, and electron dispersion spectroscopy were performed in one case. Both were destructive femoral bone tumours that appeared 2 and 8 years post-total hip arthroplasty, and pursued aggressive clinical courses. The histology was similar in both tumours, consisting of high-grade, pleomorphic sarcoma with numerous osteoclastic giant cells, prominent phagocytic activity, and entrapped particles of bone cement. Literature review disclosed 14 previous reports of arthroplasty-associated MFH, representing the most common phenotype. A number of materials and factors related to arthroplasty procedure, such as metal corrosion, wear debris, osteonecrosis, and chronic inflammation, have been implicated as causative agents. CONCLUSIONS: Arthroplasty-associated MFH is a rare and aggressive tumour. Although the aetiology remains unclear, the small number of arthroplasty-associated sarcomas compared with the large number of joint replacement operations performed over the past four decades suggests a coincidental as opposed to a causal relation.

Extensively coated femoral components in young patients.

A review of 174 hips in 154 patients younger than 50 years of age who underwent primary total hip arthroplasty with a cementless acetabular component and an extensively coated femoral component done by one surgeon was performed to determine whether this method of fixation improves the results of previously reported comparable series using different methods of fixation. The average age was 37.6 years. The average followup was 8.3 years (range, 2-13 years). Eighty-eight hips had at least 10 years followup. Sixteen (9%) hips had severe stress shielding. There were 13 (7.5%) acetabular failures. Of 144 porous coated cups, three were revised for wear and one for dislocation. Another was revised 11 years postoperatively for late loosening secondary to catastrophic acetabular lysis. Excluding the bipolar and threaded components (30 hips), five (3.4%) porous coated cups were revised for failure. Of the 174 fully coated stems, 99.4% had stable fixation, 167 (96%) were ingrown, six (3.4%) had stable fibrous fixation, and one (0.6%) was unstable. Two (1.1%) femoral stems were revised. The total rate of osteolysis was 4%. Cementless extensively porous coated stems and porous coated acetabuli give excellent lasting results in young patients.

Total joint arthroplasty and the immune response.

Total joint replacement arthroplasty has proved highly successful in the management of osteoarthritis and rheumatoid arthritis. The cause of aseptic loosening of prosthetic joint replacement components is unclear. Early experience with total joint arthroplasty was plagued by a number of problems that no longer exist as major impediments to long-term success. Improvement in the operating room environment and the use of prophylactic antibiotics have substantially reduced the high incidence of infection to less than 1%. Implant materials have long been considered biologically inert, but recent studies indicate that inflammatory reactions directed against the implanted materials may contribute to aseptic loosening. Currently, particulate debris from cement or polyethylene causing loosening of the prosthesis is the major problem in total joint arthroplasty. Significant data suggest a progression from a simple inflammatory reaction to complex immune responses against the biomaterials. The cellular responses to particles of polymethylmethacrylate, ultra-high-molecular-weight polyethylene, and alloys of cobalt-chromium and titanium have been assayed in vitro in patients with osteoarthritis, rheumatoid arthritis, and avascular necrosis who had total joint replacement. Elevated immunologic cell proliferation responses to both acrylic and cobalt chromium were observed in patients with aseptically loosened prostheses. These findings suggest that the development of a cellular response to particulate debris may be significant in the pathogenesis of aseptic loosening.