An Analysis of the Relationship between the Morphometry of the Distal Femur, and Total Knee Arthroplasty Implant Design

Abstract

Current available implants for total knee replacement are based on the mormphometry of the Caucasian knee. We believe there are significant morphometric differences in the Asian knee that will be relevant in future implant designs. Sixty-nine consecutive patients (80 knees) underwent computer navigated primary total knee arthroplasty. The anterior-posterior (AP) length, and the medial-lateral (ML) width of the distal femur, were analyzed, with respect to the final sizing details of four implants (femoral component) commonly used locally. The mean AP length was 59.9 (SD 4.8) mm, and the mean ML width was 65.0 (SD 5.0) mm. The overall mean aspect ratio (ML/AP) was 1.09 (SD 0.07). The mean aspect ratio for females was 1.08 (SD 0.07). Both were smaller than the aspect ratio of the implants - which ranged from 1.11 to 1.13. All four implants tend to ‘overhang’ at the medial-lateral width of the distal femur. This is more obvious in females. Future implant designs should provide more ‘ML w›dth’ sizes for a given ‘AP length’, in addition to gender differences, for th›s population.