Restoration of the mechanical axis is thought to be a critical factor in determining the outcome of knee replacement surgery. There is strong theoretical evidence that reproduction of this axis improves mechanical loading and hence longevity of the implant. Per operative use alignment jigs help to determine the bony cuts. Studies have shown large margins of error using the standard jigs. On this basis computer navigation systems are being introduced. No study has shown conclusively that accurately reproducing the mechanical axis of the lower limb improves survivorship of the implant. Prior to investing in these systems we felt it would be prudent to investigate how critical reproduction of the mechanical axis was in the primary total knee replacement.

We assessed 100 primary total knee replacements performed in 1990. All case notes were reviewed looking for basic demographics, pathology, and clinical outcome. All cases had a long leg þlm weight bearing alignment þlm taken post operatively. These were digitised and then analysed using CAD software. From this the mechanical axis calculated.

Using this data the patients were divided into two groups. The þrst were within 3 degrees varus/valgus of the mechanical axis. The second were outside this range. These two groups were then correlated to clinical outcome.

Our results suggest that accurate reproduction of the mechanical axis improves clinical outcome and survi-vorship of the implant. Our data would support the use of intra operative computer navigation systems

In 1999 a statement of best practice in primary total hip replacement was approved by the Council of the British Orthopaedic Association and by the British Hip Society to provide a basis for regional and national auditable standards. We have compared practice in the North West of England to this document to ascertain adherence to this guide to best practice.

86 surgeons from 26 hospitals were included in the study. A mean of 93.3% of operations were performed in the surgeon’s usual theatre. All of these theatres had vertical laminar air flow systems. 42.2% of respondents routinely used exhaust suits. 68.1% of respondents routinely used impermeable disposable gowns, 26.1% used impermeable reusable gowns. The Charnley femoral and acetabular prostheses were the most commonly used prostheses.

All surgeons use some form of anti-thromboembolic prophylaxis. 66.2% use a combination of both mechanical and chemical means. All surgeons used antibiotic prophylaxis. The most popular choice of antibiotic was a cephalosporin. 70.7% used a three-dose regime over 24 hours. 2.6% of surgeons continued antibiotic prophylaxis for 48 hours after surgery. 93.7% of surgeons routinely use antibiotic-loaded cement.All surgeons routinely cleaned, irrigated and dried the acetabulum and femur before cement insertion. Only one surgeon did not use any form of femoral canal occlusion. 69.4% used an intramedullary bone block. Retrograde filling of the femoral shaft by means of a cement gun was practised by 65.1%.

This study has demonstrated considerable variation of practice in THA across the North West region and significant divergence from the statement of best practice approved by the BOA and BHS. The introduction of a properly funded national hip register will surely help to clarify the effect of such diverse practice on patient outcome. We would recommend that all trusts locally audit their practices and correlate them to these nationally agreed guidelines.