Abstract
In Japan, osteoarthritis of the knee joint has been developing as the number of the elderly has been increasing recently. And the total knee replacement is expected to be indicated frequently. However, the total knee prosthesis does not always fit in with the shape of the Japanese osteoarthritic knee, due in part to the imported prostheses from U.S. or Europe. Therefore, the geometry of the Japanese osteoarthritic knee should be more characterized to achieve well coverage of prostheses onto the femur and tibia.
562 osteoarthritic knees rated as stage 1 or more according to Kellgren’s osteoarthritic knee classification were selected randomly and analyzed radiologically. The width of femur (FW) and the width of tibia (TW) were measured in the region 8mm from the articular surface. The distance from the anterior surface of the femur to the farthest backward of the femoral condyle was measured as FL. The anterior-posterior length of the tibia (TL) was measured by the 7 degree posterior slope of the tibial lateral image.
The AP/ML ratios of the femur and tibia were obtained by dividing FL by FW, and TL by TW. The mean value of AP/ML ratio of femur was 0.74å}0.07, and the mean value of AP/ML ratio of tibia was 0.68å}0.04. A statistically negative high correlation was found between FW and AP/ML ratio of femur, and between TW and AP/ML ratio of tibia. The larger FW and TW became, the smaller became the AP/ML ratios of femur and tibia.
Most of tatal knee prosthesises commercially available in Japan don’t follow the negative correlation between AP/ML ratio and the width of femur and tibia. We conclude that AP/ML ratio of femur and tibia should vary with the width of femur and tibia.
The abstracts were prepared by Nico Verdonschot. Correspondence should be addressed to him at Orthopaedic Research Laboratory, University Medical Centre, PO Box 9101, 6500 HB Nijmegen, The Netherlands.
