Gender-based differences in the dimensions of the femoral trochlea and condyles in the Chinese population: correlation to the risk of femoral component overhang.

BACKGROUND: Femoral component overhang has been observed in total knee arthroplasty with different prostheses. The purpose of this study is to assess gender-based anatomical differences of the distal femur and femoral trochlea in the Chinese population and analyze the risk sites of femoral component overhang in relation to any significant anatomical differences.
METHODS: Measurements of distal condylar and femoral trochlea were made through three-dimensional computed tomographic modeling of 200 normal Chinese knees; the anatomical differences between genders and its relations to the femoral component overhang were analyzed. Four implants were also measured and compared.
RESULTS: The ML/AP ratios of the femoral condyles showed statistically significant gender-based variation (Men:Women=1.06:1.03, P<0.0001). Both the proximal and distal ML widths of the trochlea were generally larger in the men than those of the women. Regression analysis of the morphological data showed that as the measuring level moves distally along the femur, the coronal width deviation between genders progressively increases to peak at the distal condyles. Female subjects had a smaller aspect ratio than those of four implants and a smaller trochlear ML width than those of three implants.
CONCLUSIONS: The males show significantly greater coronal dimensions of the trochlea than women which are likely to contribute to the higher prevalence of prosthetic overhang in women with some standard implants. CLINICAL RELEVANCE: The overhang is most likely to occur in the distal femoral condyle and the distal region of the femoral trochlea when a standard knee prosthetic system is used in the Chinese women.