Wear at the Tibio-Femoral articulation of the Total Knee Replacement

Background: Despite improvements in manufacture, sterilization and storage of tibial inserts, polyethylene wear continues to restrict the survivorship of total knee replacements. The problem is particularly evident in the young population undergoing knee arthroplasty. Aims and Methods: The objectives of the thesis were to ascertain: • If polyethylene wear may be reduced by utilizing scratch resistant femoral coats. • The timing of significant femoral scratching in the laboratory setting • If retrieved femoral components exhibited scratches and whether the roughening of the components is significant Results: • Both zirconium oxide and titanium niobium nitride femoral coats provided scratch resistance. However, no polyethylene wear benefit was conferred by the titanium niobium coat. • Significant scratching was noted as early as 100 cycles. • Retrieval specimens exhibited femoral scratching which were of the same orientation of those noted from the simulator studies. Not all condyles had significant roughening. Conclusions: Improving the scratch resistance of femoral components has the potential to improve the longevity of total knee replacements. However, alternate bearing surfaces should be used with caution, as the standard modern day knee replacement allows reproducibility and good mid to long term results which are lacking for alternate bearings. Improvements in polyethylene wear may be achieved by engineering a femoral coat that reduces abrasive, adhesive wear and delamination or by optimizing the ultra high molecular weight polyethylene components

Custom prosthetic replacement for distal radial tumours

We analysed the results of 24 cases of aggressive benign and malignant tumours of the distal radius treated by resection and prosthetic replacement between 1995 and 2006. Patient ages ranged from 18 to 74 years, averaging 33 years; 18 were males. Recurrent giant cell tumour was the most common tumour. The prosthesis used was a bipolar hinge custom mega prosthesis manufactured locally. Average follow-up was 78 months. The average Musculoskeletal Tumor Society (MSTS) functional score achieved was 75%. The ten-year prosthesis survival was rate 87.5%. Infection was the most common complication