Introduction: Stress shielding has been found to cause cortical thinning and loss of trabecular bone in the proximal femur due to stiff steam and elastic bone. To avoid these problems a prosthesis was developed according to the concept of isoelasticity. Its aim was to ensure the implant and the bone to deform as one unit loading the bone in a more physiological way. Methods: From 1984 Ð1987 we performed 149 total hip replacements using third generation Mathys isoelastic polyacetal stem with stainless-steel heads and polyethylene cementless acetabular cups. Average patient age was 47 years (21–82). Eleven patients (12 hips) has died before revision and fourteen (15 hips) were lost to follow up. Results: Hitherto 69 hips were revised, þve due to infection. The 10 years revision rate for any reason was 68.7%. The remaining 48 patients (53 hips) have been clinically and radiologically assessed or reviewed by a questionnaire. In these patients the average HHS was 80 points. Thirteen among them had failed radiologically, many without a poor subjective result. Conclusions: The performance of this prosthesis was unacceptably poor but nevertheless the concept of isoelasticity should not be completely disregarded. Future trends may reconsider and reintroduce some new materials or implant designs which would be able to achieve the aim of isoelasticity without former problems. Long term total hip loosenings are still all but solved.

Introduction: Standard therapy for orthopedic device infections includes a two-stage exchange and prolonged antimicrobial therapy. In a subgroup of patients, retention of the device seems to be an effective alternative. Methods: In a prospective study we evaluated treatment efþcacy of orthopedic device infections with implant retention. Inclusion criteria were: early manifestation, stable implant, known pathogen, susceptibility of staphylococci to quinolones and rifampin, good condition of soft tissue. Initially, intravenous antimicrobial therapy was given for 2 weeks, followed by oral treatment for 10 weeks (knee prostheses for 6 months). Results: From January 1999 through June 2002, 19 patients were included: hip prosthesis (9), knee prostheses (6) and internal þxation devices (4). Isolated pathogens were: staphylococci (14), streptococci (4), enterococci (1), and Propionibacterium acnes (1). Open debridement with device retention was performed in 13 patients; the remaining 6 patients were treated with antibiotics only. After initial 2-week intravenous therapy, staphylococcal infections were treated with oral ciproßoxacin 750 mg bid + rifampin 450 mg bid, streptococcal and enterococcal infections with oral amoxicillin 750 mg tid and the P. acnes-infection with oral clindamycin 600 mg tid. 12 of 16 patients were followed for at least 24 months. 10 (83%) had no symptoms or signs of infection at follow-up, 2 (17%) had a relapse Conclusion: In carefully selected patients, device retention with antimicrobial treatment for 3–6 months may be an effective approach.