Use of anthropometric data from the medial tibial and femoral condyles to design unicondylar knee prostheses in the Chinese population.

Anthropometric data on medial tibial condyles and medial femoral condyles of 172 normal knees (94 male knees, 78 female knees) were obtained using three-dimensional computer tomographic measurements. In the medial tibial condyle, we measured the anteroposterior (AP) and widest dimension (WD), and compared the measurements with the similar dimensions of five tibial unicondylar knee prostheses conventionally used in China. In the femur, we used best-fit two-circular arcs to measure the morphology of the sagittal plane of the medial femoral condyle. We found that three of the prostheses showed WD overhang for all ranges of the AP dimension, while two of them showed WD underhang. We also found a progressive decrease in the condylar aspect ratio (WD/AP%) in parallel with an increase in the AP dimension in the medial tibial condyle. However, none of the conventional tibial prosthesis showed a similar change. Furthermore, males had larger values in aspect ratio than females with the same values for AP dimension. There were definite correlations between the radius of the curvature for the posterior part (R1) and distal part (R2) in the sagittal plane of medial femoral condyle. Both of these values were smaller than in the Caucasian population. Both radiuses of curvature for the posterior and distal components showed definite correlations with the AP dimension. The results of this study may provide guidelines for designing unicondylar knee prostheses suitable for the Chinese population.