Fixation and loosening of the cemented Muller straight stem: a long-term clinical and radiological review.

The original forged Müller straight stem (CoNiCr) has shown excellent ten- to 15-year results. We undertook a long-term survival analysis with special emphasis on radiological changes within a 20-year period of follow-up. In all, 165 primary total hip replacements, undertaken between July 1984 and June 1987 were followed prospectively. Clinical follow-up included a standardised clinical examination, and radiological assessment was based on a standardised anteroposterior radiograph of the pelvis, which was studied for the presence of osteolysis, debonding and cortical atrophy. Survival of the stem with revision for any reason was 81% (95% confidence interval (CI), 76 to 86) at 20 years and for aseptic loosening 87% (95% CI, 82 to 90). At the 20-year follow-up, 15 of the surviving 36 stems showed no radiological changes. Debonding (p = 0.005), osteolysis (p = 0.003) and linear polyethylene wear (p = 0.016) were associated with aseptic loosening, whereas cortical atrophy was not associated with failure (p = 0.008). The 20-year results of the Müller straight stem are comparable to those of other successful cemented systems with similar follow-up. Radiological changes are frequently observed, but with a low incidence of progression, and rarely result in revision. Cortical atrophy appears to be an effect of ageing and not a sign of loosening of the femoral component.

EBRA migration patterns of the Plasmacup with ceramic or polyethylene inserts: a randomised study.

AIM: In this prospective randomised study, the influence of different bearing materials on migration and wear was measured and their effect on the function of the artificial joint and the patient outcome was investigated. Mid-term results were recorded so that recommendations can be made on the use of certain bearings, which minimise wear and thus the danger of subsequent aseptic loosening. METHOD: Sixty-six patients met the inclusion criteria and were willing to take part in the study. These patients were randomised to 2 groups. All of them had total hip arthroplasty with implantation of a cementless Bicontact stem and Plasmacup using a cementless press-fit technique. Thirty-five of these patients were given a ceramic-ceramic bearing and 31 patients a ceramic-polyethylene bearing (gamma sterilised/nitrogen environment). At the most recent follow-up, they underwent detailed clinical and radiological examination and evaluation by means of the Harris Hip Score, Hannover function questionnaire and single-film X-ray analysis (EBRA). RESULTS: The overall follow-up rate was 65.2 % (43 of 66) and the mean follow-up period was 8.1 (7.1 - 9.2) years. The median Harris Hip Score at the time of follow-up was 90.1 (58.7 - 99.9) points. The average Hannover function score was 87.14 % (63.9 - 100). In 4 of 66 cases (6.1 %) there was a tendency for the Plasmacup to subsidence in the first postoperative months that was slight but detectable by EBRA; however, this stopped subsequently. This primary subsidence was independent of the chosen bearing material. No significant difference in the clinical and radiological parameters was found between the two groups. CONCLUSION: The very good results with regard to the rate of loosening confirm the press-fit cup fixation concept. The study shows a similar medium-term result for the ceramic-ceramic and ceramic-polyethylene bearing so that use of both bearings can continue to be recommended. Only long-term studies with sufficiently large numbers of patients will be able to show whether significant differences can be detected between the two slide bearings with regard to wear and migration behaviour and so that a recommendation can be given to the surgeon.

Five-year results of two cemented hip stem models each made of two different alloys.

INTRODUCTION: The aim of this study was to compare the influence of two different cemented hip stems each made of two different alloys concerning survival and outcome. MATERIALS AND METHODS: The 5-year results with 161 Mueller straight stems made of cobalt chromium (SS CoCr), 272 Mueller straight stems made of titanium (SS Ti), 233 Mueller SL stems made of titanium (SL Ti) and 255 SL stems made of cobalt chromium (SL CoCr) implanted consecutively in this order were compared. All patients were followed up prospectively during the first 5 years after implantation. The evaluation of the results was retrospective. RESULTS: The survival rates for aseptic loosening were 100% (SS CoCr), 92.8% (SS Ti), 81.6% (SL Ti) and 97.8% (SL CoCr). Clinical and radiological outcomes like pain occurrence, use of pain medication, ability to climb stairs, amount of stem subsidence and osteolysis correlated statistically significantly with the results of the survival rates. Concerning the two alloys, chromium cobalt showed better results, and concerning the two designs, the straight stem had a better outcome. For the four prostheses being compared, the results were influenced more by the alloy than by the design, and the small-sized titanium stems were more susceptible to undergoing revision than the large-sized prostheses. CONCLUSION: Stem design and even more alloy may influence the survival rate and clinical outcome. Evaluating the results, we recommend the use of the classic straight stem prosthesis made of cobalt chromium.

[The value of the Wagner SL revision prosthesis for bridging large femoral defects]. / Der Wert der SL-Revisionsprothese nach Wagner zur Uberbrückung grosser Femurdefekte. Technik und Resultate.

Between 1988 and 1999 we used the Wagner SL revision prosthesis in 99 cases. The indications were aseptic and septic loosening, periprosthetic fractures, and Girdlestone situations. These were mostly Paprosky types 2 and 3 meta- and metadiaphyseal femoral bone defects. The intervention was the first revision in 49 cases and the second or up to the sixth revision in 50 cases. A transgluteal or transfemoral approach was usually chosen. We gradually reduced the anchorage area to a length of 8-12 cm. If after the first few postoperative months an osseous integration without radiolucency is achieved, a long-lasting integration can be expected. Due to considerable subsidence during the 1st year, six stems had to be replaced. Seven additional revisions were done because of hematoma and three because of seroma. According to the survival analysis, 92% of the stems remained in place after 10 years. No revision was executed between the 5th and 10th year. At the 1-year control, 96% of the patients were pain free and 90% were satisfied. Nevertheless, 80% limped and 33% used at least one crutch. Mainly because of deterioration of general health, the walking distance was considerably reduced between the 1st and the 5th postoperative year. There is little difference in the results after revision between a relatively small and an extended defect. At present, we limit the use of the SL revision stem mainly to extended defects. Careful planning of the operation is mandatory.