Lessons learned from early clinical experience and results of 300 ASR hip resurfacing implantations

Between August 2003 and April 2005, 300 ASR metal-on-metal resurfacing hip endoprostheses were implanted by the first author and a fellow surgeon. The mean age at surgery was 56.8 years (18-75.9 years) and mean body mass index was 27.6 kg/m2 (range, 19-41 kg/m2). The mean follow-up time was 202 days. The mean Harris hip score improved from 44 pre-operatively to 89 at 3 months post-operatively. In total, eight (2.7 per cent) cases [five neck fractures (1.66 per cent) and three cup revisions (1 per cent)] were revised. Two neck fractures occurred within a group of seven cases of femoral neck notching detected postoperatively; one neck fracture occurred out of two cases of incomplete seating of the femoral implant. A significantly higher (p < 0.001) failure rate was observed for patients who had undergone a previous osteosynthesis of the proximal femur (three revisions in a group of 15 patients). Revision cases had a significantly greater body mass index (p = 0.031). A learning curve was evident from the reduction in revisions from 5 in the first 100 surgical procedures to 2 in the next 100 and 1 in the last 100. These results show the importance of accurate surgical technique and careful patient selection for fourth-generation hip resurfacing implants

Comparison of the elution properties of commercially available gentamicin and bone cement containing vancomycin with 'home-made' preparations

Introduction Vancomycin is commonly added to acrylic bone cement during revision arthroplasty surgery. Proprietary cement preparations containing vancomycin are available but significantly more expensive. We investigated whether the antibiotic elution and mechanical strength of ‘home-made’ vancomycin containing bone cement was comparable to commercial vancomycin-impregnated cement. Methods A total of 18 cement discs of constant size, containing either proprietary CopalG+V®; or ‘home-made’ CopalR+G® with vancomycin added by hand, were made. Each disc contained the same antibiotic quantities (0.5g gentamycin, 2g vancomycin) and was immersed in ammonium acetate buffer in a sealed container. Fluid from each container was sampled at eight time points over a two week period. The concentration of gentamicin and vancomycin in the fluid was analysed using high performance liquid chromatography mass spectrometry. The impact strength of each PMMA cement preparation was measured using a Charpy-type impact tester. Results Highest peak antibiotic concentrations were observed from the ‘home-made’ vancomycin containing cement, added as in the operating theatre. Overall antibiotic elution was, five-fold (vancomycin) and two-fold (gentamicin), greater from the ‘home-made’ mix compared to commercially mixed cement. However the ‘home-made’ cements showed greater variation in elution kinetics compared to the commercial mix. Use of a vacuum during mixing had no significant effect on antibiotic elution in any of the samples. Impact strength testing showed no significant differences between the groups. Discussion Our findings suggest the addition of 2g vancomycin powder to gentamicin-impregnated bone cement in theatre, significantly increases elution of both antibiotics, with no significant loss of strength, compared to commercially prepared cement. Conclusion We have found no significant advantages of expensive off-the-shelf vancomycin-impregnated bone cement and recommend the addition of vancomycin powder by hand when making cement beads and spacers