Femoral bowing in the coronal plane: A computed tomography analysis of 1313 femurs

Appreciation of femoral bowing in the sagittal plane has led to optimization of implant design and placement techniques. However, little is known about femoral bowing in the coronal plane. The objective of this study was to describe coronal bowing of the femur and how demographic characteristics were associated with bowing.

Three-dimensional models of 1313 left femurs taken from the Stryker Orthopaedic Modeling and Analytics database were analyzed. Coronal bowing was measured via radius of curvature in centimeters (cm) and classified as straight (>300 cm), mild-to-moderate (150 to 300 cm), and severe (<150 cm). Univariable analyses were performed to detect associations between demographics and coronal bowing. Multivariable analyses including sex-specific Spearman correlation coefficients were also undertaken.

In total, 236 femurs (18 %) had mild-to-moderate lateral bowing, 46 (4 %) had severe lateral bowing, 35 (3 %) had mild-to-moderate medial bowing, and 2 (<1 %) had severe medial bowing. Univariable analyses revealed coronal bowing had significant associations with age (p < 0.001), sex (p < 0.001), and ethnicity (p = 0.002) but not with body mass index (p = 0.54). Multivariable analyses found the correlation of age with coronal bowing to be moderate positive in females (Spearman's Rho = 0.42, p < 0.001) compared to weak positive in males (Spearman's Rho = 0.21, p < 0.001).

Three-dimensional analysis of 1313 femurs demonstrated that 24 % of femurs had coronal bowing which had significant associations with age, sex, and ethnicity. Coronal bowing had a positive correlation with age that was stronger in females. By acknowledging variations in femoral morphology, these findings highlight the utility of examining radiographs of the injured and uninjured femurs in multiple planes during preoperative planning.