Introduction: To our knowledge there are no published data comparing the actual anteroposterior (AP) and mediolateral (ML) dimensions of the medial and lateral tibial plateau with tibial dimensions of current available tibial designs of unicompartimental arthroplasies (UKA). Inter- and intra-gender specific dimensions may not match current designs.

Methods: Medial and lateral tibial plateaus of 42 CTs of cadaveric knees were measured in its AP and ML dimension. There were 25 male and 17 female knees. The results of the measurements were compared to current in the US available UKA systems.

Results: Wide variations in all observed articular femoral and tibial surfaces were observed. There are gender and side differences between medial and lateral in respect to the aspect ratio AP/ML:AP length of the female medial tibial plateau is 4.9 cm (Std Dev 0.38, n=25), AP length lateral tibial plateau is 4.5 cm (Std Dev 0.5, n=25), ML width medial plateau is 2.9 cm (Std Dev 0.27, n=25), ML lateral tibial plateau is 3.1 cm (Std Dev 0.21, n=25), AP length of the male medial tibial plateau is 5.5 cm (Std Dev 0.30, n=26), AP length lateral tibial plateau is 4.95 cm (Std Dev 0.34, n=26), ML width medial plateau is 3.3 cm (Std Dev 0.20, n=26), ML width lateral tibial plateau is 3.48 cm (Std Dev 0.24, n=26), All measurements comparing female and male data for medial and lateral surfaces were different (Student-t, p< 0.005). All current available observed UKA match best the female medial plateau, less the male tibial plateau and very poor the male and female lateral tibial plateau.

Discussion/Conclusion: Intra- and inter gender differences of morphologic data are shown for all articular surfaces, medial and lateral femur, as well as medial and lateral tibia. Best matches between AP/ML ratio and implants were seen for the medial tibial components and the female medial plateau. Poor matches were observed for the lateral female and male tibial plateau. The common practice of using a right medial tibial implant for the lateral side should be reconsidered. The question if the poor match of current medial tibial components in larger males has a relationship to the inferior clinical results of males undergoing UKA requires more investigation.