Custom endoprostheses for limb salvage: a historical perspective and imaging evaluation.
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A new technique for cement removal is presented where bone cement is added to the cavity after removal of a femoral component. The old and new segments of cement are then removed together by using a threaded extractor. In 16 of 20 patients, the method was successful; the entire cement mass was extracted in 35 (25-50) min without complications or bone loss. In 4 of the patients, the technique had to be combined with traditional methods for cement removal.
The fibrous interface tissue between hip prostheses and surrounding bone is often morphologically and functionally synovial-like. The fibroblast is the major cell type; but also giant cells and macrophages are present, and their numbers are increased in the occasional adverse-type host reaction to the prosthesis. Adverse lytic reactions are often associated with methylmethacrylate debris, whereas in cementless cases, polyethylene and metallic (titanium) wear debris seem to cause adverse reactions. Osteoblasts, osteoclasts, and mesenchymal collagenase secreted by fibroblasts and macrophages play an important role in the process of prosthetic loosening. Methylmethacrylate is immunologically relatively inert, while it induces inflammatory mononuclear-cell migration. Both cemented and cementless prostheses cause a foreign-body type host response, including adaptive and reactive processes. This response includes the formation of fibroblast-like B-type lining cells, which are able to synthesize and secrete hyaluronate. Material surfaces of hip arthroplasty components also provide a unique environmental niche to which staphylococcal strains adhere and colonize. Antibiotic resistance is related to the material colonized rather than to the presence of an exopolysaccharide barrier; organisms bound to polyethylene and methylmethacrylate are more resistant than organisms that are bound to stainless steel. An understanding of prosthetic biocompatibility requires an appreciation of tissue cell, bacterial cell and host defense-system response to biomaterials. The site of implantation is a stage on which the "players" (bacteria, host cells, and organic moieties) interact and compete, and before which the host is a "responsive audience."
A prospective, national multi-center study of all reoperations after total hip replacement (THR) was started by the Swedish Orthopedic Association in 1979. The material comprises all THR performed in Sweden, presently more than 10,000 yearly or 130 THR per 100,000 inhabitants; uncemented implants have been used in less than 2 percent. The main reasons for revision have been aseptic loosening 79 percent, infection 10 percent, technical error 6 percent, and dislocation 2 percent. The cumulative rate of revision for deep infection has dropped from 0.9 percent to < 0.5 percent for implants inserted 1979 and 1983, respectively. With the Charnley prosthesis as the gold, standard the performance of other prostheses was analyzed. Improved cementation techniques and anti-infection measures have continuously reduced the revision risk. The register demonstrates that the average orthopedic surgeon cannot match the results achieved by experts. However, the vast majority of THR, worldwide, are not performed by experts. Quality-assurance in this sector of orthopedics demands a continuous analysis of the outcome of these operations.
The Swedish Knee Arthroplasty Register has data on 4,381 primary operations performed 1985-1995 for rheumatoid arthritis. Of these, 192 were performed with unicompartmental prostheses and 4143 with tricompartmental. 77% were women and the mean age was 66 years. There were 126 first, 20 second, and 1 third revision in tricompartmental arthroplasties, mainly for loosening, infection and patellar problems. There were 38 first, 3 second, and 1 third revision in unicompartmental arthroplasties, mainly for progression of RA and loosening. Cumulative revision rates (Kaplan-Meier) were calculated. Tricompartmental knees had a 10-year cumulative revision rate of 5% and uni-knees 25%. Patients treated before 1990, men and patients younger than 55 had higher revision rates than patients treated after 1990, women and older patients, respectively. Cemented tibial components resulted in lower revision rates than uncemented ones. There was no significant difference in revision rates between patellar replaced and unreplaced knees or between the 9 commonest implant types.
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We analyzed the cumulative revision rate in 1,474 patients (1,660 hips) operated on with a cemented Scan Hip Classic I prosthesis from November 1983 to January 1994 at Lund University Hospital. The revision rate was analyzed for 3 diagnoses--arthrosis, rheumatoid arthritis and complication after a hip fracture--and for 2 head diameters--22 and 32 mm. Until January 1996, 36 hips were revised: 31 because of aseptic loosening, 3 because of dislocation and 2 because of infection. The overall revision rate was 5.6% after 10 years and was similar in arthrosis, rheumatoid arthritis and fracture cases. Due to revisions because of dislocation in the 22 mm group, the total revision rate was lower in the 32 mm group (p = 0.03).
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We have six choices in selecting treatment for infected TKA. My preference is two-stage revision arthroplasty combined with appropriate parenteral antibiotic therapy. This treatment provides a success rate of approximately 90% for cure of infection and good function in most instances.
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Although the host tissue response to debris is rarely symptomatic, the clinical manifestations of implant wear are profound. Even the most experienced orthopedic surgeon can be challenged in managing this sometimes silent disease.
Thirteen patients with failed total knee arthroplasty (TKA) due to infection (12 patients) or aseptic loosening (1 patient) underwent arthrodesis using the Ilizarov external fixator. Solid fusion was achieved in all patients with an average healing time of 27.6 weeks. Patients spent an average 18.8 weeks in the fixator followed by an average 8.8 weeks in a plaster cylinder cast. Five patients had a pin tract infection and one a superficial wound infection. One patient had 15 degrees recurvatum after surgery that was gradually corrected by adding a hinge system to the fixator. Average shortening of the affected limb was 3.7 cm (range: 1-6 cm). The Ilizarov fixator for knee arthrodesis after failed TKA produced favorable results and should be considered for use by surgeons familiar with the technique.
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Revision hip arthroplasty will be performed with frequency in the future. A successful outcome depends on careful preoperative planning, and a key component of that plan is the surgical approach. The choice of the approach should be based on the indication for revision, the particular implant to be removed, the presence of acetabular or femoral bone loss, previous surgical approaches used, and the preferences and training of the surgeon. For simple revision procedures, one of the standard approaches used in primary hip arthroplasty may be adequate. More complex cases may necessitate an extended exposure or one of the techniques developed specifically for revision arthroplasty. No single approach is suitable for all revision procedures, and the surgeon must be familiar with a range of exposures if the clinical result is to be optimized.