Background: Within the scope of the EU project EUPHORIC a methodology for direct comparison of different datasets was developed and applied on a sample of implants, among them the Oxford Unicompartmental Knee Arthroplasty (Oxford Uni). The aim was to identify potential bias factors inherent in the datasets and evaluate the outcome achieved with this implant.

Materials and Methods: A structured comparison was performed of data published on the revision rate of the Oxford Unicompartmental prosthesis. Both clinical follow-up studies published in Medline-listed journals and worldwide Register data were included. The data were stratified with regard to potential influence factors like the individual research groups or the geographical origin of the papers.

Results: A major proportion of the published data, between 50 and 75%, depending on the method of calculation, comes from studies including the developing institution in Oxford. The results published by this group deviates statistically significantly from the reference datasets from Register data or independent research groups. Data from the developing hospital show mean revision rates that are 4.4 times lower than those based on worldwide Register data, and 2.74 times lower than in independent studies. As opposed to this, independent studies on average publish data that are reproducible in Register data.

Conclusion: A conventional meta-analysis of clinical studies is significantly affected through the influence of the developing institution and is therefore subject to a bias. Neither through arthroplasty Register outcome data nor by other research groups that have disclosed outcome information on the Oxford Uni can the excellent results be reproduced that were published by the inventors.

Compared to other implants for unicompartmental knee arthroplasty in worldwide arthroplasty Registers, the Oxford Uni shows good results.

For the assessment of the outcome of implants, register data are to be rated superior and, in terms of reference data for the detection of potential bias factors in the clinical literature, can provide an essential contribution for scientific meta-analyses.

Study Design. Retrospective clinical and radiographic review of patients after Bernese periacetabular osteotomy for symptomatic congenital hip dysplasia. Introduction. The Bernese periacetabular osteotomy for the treatment of symptomatic congenital hip dysplasia is known to be a complex operative procedure. Several authors reported significant percentages of peri- and postoperative complications.

Objective.The aim of our study was to reveal whether the incidence as well as the grade of complications affect the postoperative outcome which was determined by the short form (SF) 36 and the Western Ontario McMasters osteoarthritis (WOMAC) questionnaires.

Methods. A consecutive series of 50 patients with 60 hips operated between 1988 and 2000 were investigated retrospectively with a mean follow up period of 32 months.

Results. With an incidence of 30% a lesion of the lateral cutaneus nerve occurred. In 10% a peroneal nerve palsy was diagnosed immediate postoperatively, with 4% persistent neurological deficit presented at one year follow up. Several other minor and major complications occurred with an overall complication rate of 68%. According to the severity of complications two groups of patients were identified. Statistical analysis did not reveal any difference between the results of the SF-36 (p=0.2) and WOMAC (p=0.09) questionnaires. Radiological analysis revealed a deterioration of osteoarthritis in 32% of our patients. These patients predominantly judged their postoperative results poor to fair (r=0.71). 76% rated the operation as successful and 64% would have surgery again. The subjective estimation of patients health status postoperatively was significantly reduced compared to an age matched healthy reference group (p=0.0001).

Conclusion. Despite the high incidence of complications 76% of the patients rated the operation as successful. 32% of the patients faced a deterioration of osteoarthritis. The postoperative results after Bernese periacetabular osteotomy are rather more influenced by the progression of osteoarthritis than by the occurrence of perioperative complications.