Anthropometry of the medial tibial condyle to design the tibial component for unicondylar knee arthroplasty for the Korean population

Unicondylar knee arthroplasty (UKA) has gained popularity in the recent years for treating medial compartment osteoarthritis of the knee joint in the Asian population. There is little information about the anthropometry of the resected bony surfaces of the knee joint in these population groups for designing the appropriate size-matched UKA components. We studied the anthropometry of the resected medial tibial condyles in 50 male and 50 female Korean cadavers by using three-dimensional computer tomography. We measured the anteroposterior dimension, the mediolateral dimension at defined points and the condylar aspect ratio. These measurements were compared with similar dimensions of the tibial components from five conventionally used UKA designs. Statistical analysis was performed using Student's t-test, Paired t-test and Pearson's correlation coefficient. We found that three of the tibial component designs showed mediolateral overhang for the whole range of measured anteroposterior dimensions of the resected medial tibial condyles, whereas one of the designs (DePuy) showed mediolateral undersizing for the smaller AP dimensions and overhang for the larger AP dimensions of the resected medial tibial condyles. Another design (Smith and Nephew) showed mediolateral undersizing for the whole range of measured anteroposterior dimensions of the resected medial tibial condyle. We found a decrease in the condylar aspect ratio with increasing AP dimension for our cadaver population data. However, the majority of the conventional tibial prosthesis showed either a constant condylar aspect ratio or an increasing aspect ratio (DePuy) with the increasing AP dimension of the resected medial tibial condyle. Our study may provide guidelines for designing appropriate tibial UKA components for a majority of Asian sub-populations and encourage similar studies in other population groups.