Abstract
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
Theses abstracts were prepared by Professor Dr. Frantz Langlais. Correspondence should be addressed to him at EFORT Central Office, Freihofstrasse 22, CH-8700 Küsnacht, Switzerland.
