Differences in characteristic morphological variability among distal femurs based on sex and ethnicity

The morphology of the distal femur varies widely among individuals and has a direct impact on knee joint mechanics and function. Understanding this variability is essential in improving surgical planning and implant design, especially as current tools and approaches move toward more anatomically informed and personalized technique. This study sought to characterize the major modes of morphological variability in the adult human distal femur and to examine morphometric differences based on sex and ethnicity.

A dataset of 1,686 distal femurs from a CT scan-based database was analyzed. A total of 15 morphometric dimensional and angular variables were assessed, and principal component analysis (PCA) was employed to identify key modes of variability. Morphological differences were examined between male and female femurs and among self-identified Caucasian and Asian ethnic groups.

Five principal components (PCs) explained over 90% of the total variance in the original morphometric variables. Male and Caucasian femurs were significantly larger than female and Asian femora respectively (PC1; 58.3% variability explained). There were characteristic variations in the trochlear anatomy, with female and Asian femurs exhibiting more elevated anterior distal femora (PC2; 13.6%). Variability in the intercondylar notch (PC3 11%) and femoral aspect ratio (PC5; 4.9%) were sex-specific, with female femora having relatively less anteriorly elevated medial condyles, larger AP height, and relatively narrower in the AP direction than male femora. However, variability in the condylar twist angles (PC4; 6.2%) was not different based on sex or ethnicity.

This study characterized morphological variability in a large sample of distal femora, with key differences noted based on sex and ethnicity. The results support further consideration of this variability in knee arthroplasty implant design options and surgical approaches.