Background and purpose —Due to the relative lack of reports on the medium- to long-term clinical and radiographic results of modular femoral cementless revision, we conducted this study to evaluate the medium- to long-term results of uncemented femoral stem revisions using the modular MRP-TITAN stem with distal diaphyseal fixation in a consecutive patient series.Patients and methods —We retrospectively analyzed 163 femoral stem revisions performed between 1993 and 2001 with a mean follow-up of 10 (5–16) years. Clinical assessment included the Harris hip score (HHS) with reference to comorbidities and femoral defect sizes classified by Charnley and Paprosky. Intraoperative and postoperative complications were analyzed and the failure rate of the MRP stem for any reason was examined.Results —Mean HHS improved up to the last follow-up (37 (SD 24) vs. 79 (SD 19); p < 0.001). 99 cases (61%) had extensive bone defects (Paprosky IIB–III). Radiographic evaluation showed stable stem anchorage in 151 cases (93%) at the last follow-up. 10 implants (6%) failed for various reasons. Neither a breakage of a stem nor loosening of the morse taper junction was recorded. Kaplan-Meier survival analysis revealed a 10-year survival probability of 97% (95% CI: 95–100).Interpretation —This is one of the largest medium- to long-term analyses of cementless modular revision stems with distal diaphyseal anchorage. The modular MRP-TITAN was reliable, with a Kaplan-Meier survival probability of 97% at 10 years.
More and more megaprostheses are being implanted - not just injuries or primary and secondary bone tumors, but also the increase in extended bone defects in revision arthroplasty call for the more frequent use of megaimplants. Underlying disease, medication, age, and frequency of surgical procedures give rise to infections which occur in more than 10% of the patients receiving megaprostheses. Size, surface, and design of the implants themselves increase the infection rate.Every year we treat more than 45 patients with periprosthetic infections of megaimplants and large revision prostheses, many of them infected with multi-resistant germs. MRSE and MRSA have been shown to increase the rate of relapses (19%). The treatment strategy continues to consist of multiple steps, and temporary stabilization is achieved either externally with external fixation devices or orthoses or internally with spacers (PMMA, interim implants). To avoid relapsing infections surgeons must rely on anti-infective surface coatings (silver), local drug carriers (collagen, PMMA), and especially soft tissue coverage with local muscle flaps and radical treatment of the bone infection. Amputations, however, cannot be avoided completely; 5% of our patients had to undergo amputations above the knee after infections of megaimplants.Surgery will be required more frequently to treat infections of megaprostheses and increase the medical, nursing, logistic, technological, and financial burden on the patients, surgeons, clinics, and insurance companies.
The effects of preservation and sterilization on the structural properties of cortical bone were investigated. Specimens of cortical bone from rat tibiae were frozen (-70 degrees C for 28 days), freeze-dried, irradiated (1, 5, 25 and 50 kGy) or autoclaved (at 134 degrees C for 3 or 5 min), and examined by scanning electron microscopy. Cryopreservation and irradiation had no deleterious effects on the surface structure of the cortical bone. Freeze-drying caused microcracks running parallel to the mineralized fiber bundles. After autoclaving, a time-dependent distension, swelling and amalgamation of the fibrillary matrix was observed. This denaturation of the organic matrix was more pronounced after 5 min than 3 min autoclaving. The alterations of the fibrillary structure described above might be due to a preservation- and sterilization-induced decrease of the biological and biomechanical potential of bone grafts.
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