COMPARISON BETWEEN DIFFERENT IMPLANT DIMENSIONS IN RELATION TO KNEE ANTHROPOMETRY

Background The knee joint morphology varies according to gender and morphotype of the patients. Objectives To measure the dimensions of the proximal tibia and distal femur of osteoarthritic knees in a group of patients from the same ethnic group (Arabs) and to compare these measurements with the dimensions of six total knee implants. Patients and methods Three-dimensional CT reconstructions were used to collect morphologic data from 124 osteoarthritic knees. Anteroposterior and mediolateral measurements were obtained from tibial and femoral bony resection surfaces planned for patient-specific instrumentation (Figures 1 and 2). These measurements were compared to the dimensions for six different types of knee implants. Results The average tibial mediolateral (tML) and tibial anteroposterior (tAP) measurement for the study group were 74.36±6 mm and 48.94±4.57 mm, respectively; the medial tibial plateau was larger than lateral. The average femur mediolateral (fML) and femur anteroposterior (fAP) measurements for the same group were 72.04±6.6 and 68.1±7.75, respectively. For implant matching, the average tibial aspect ratio was 152.62±12.66 and the femoral average aspect ratio was 106.37±14.34. Differences were found between morphometric measurements of males and females with significantly higher parameters for males when compared to female when compared in AP and mediolateral dimensions. Also, 22.5% of the operated knees had mismatch within 2 size of the same implant. Conclusion There is significant asymmetry of proximal tibial plateau and femur condyles. Our data suggest mismatch between osteoarthritic Arabian knees and implant designs. These ethnic differences should be considered when designing knee implants.