Femoral bicondylar angle is defined as the angle between femoral shaft axis and a line perpendicular to the infracondylar plane. Modern human skeleton has many key traits for bipedal locomotion and bicondylar angle is one of them.[1] Ontogenetically, bicondylar angle forms when the femur grows in early childhood. At birth, the shaft axis of femur is perpendicular to the methaphyseal growth plate. The angle is formed when the child first starts to walk and reaches a stable value of eight to ten degrees by the age of eight years.[2] Bicondylar angle does not form in bedridden children (neuromuscular disorders, paraplegic) who cannot walk in early stage of childhood.[3] In contrast, quadrupedal apes have small bicondylar angles.[4]

Bicondylar angle unambiguously implies bipedalism so a fossil femur is sufficient for paleoanthropologist to determine the human lineage. Besides, determining bicondylar angle is useful for both the anatomist as well as orthopedic surgeons for their clinical practices.

This study aims to determine femoral bicondylar angle and observe any variation on right and left side, and also to assess its relation with length of femur and length of neck of femur available at Anatomy Department.

A cross-sectional study was carried out in all dry adult human femurs available in the Department of Anatomy, Institute of Medicine, Kathmandu. Fully ossified bones irrespective of age, sex, and races were included. Bones with gross asymmetry or deformity were rejected.

A total of 102 dry adult human femur were available for the study. There were 51 (50%) right femur and 51 (50%) left femur. The morphometric parameters of dry femurs (maximum, minimum, mean and standard deviation) are presented in Table 1. The difference of bicondylar angle of two sides was not statistically significant (t = -1.75, df = 100, p = 0.08).

Pearson correlations were measured to determine the relationship among bicondylar angle and femoral dimensions (Fig 3A, Fig 3B, Fig 3C, Fig 3D). None of the parameters were statistically significantly correlated as shown in Table 2.

We conducted this study to determine femoral bicondylar angle and observe any variation on right and left side, and also to assess its relation with femur dimensions. We found that right bicondylar angle was higher than left but the difference was not statistically significant (p = 0.08). There were no significant relationships between bicondylar angle with other femur dimensions (length and neck length).

Various studies had been carried out on assessment of femoral bicondylar angle and its correlation with various femoral dimensions. Table 3 shows the comparison of mean bicondylar angle of present study with other studies.

Mean bicondylar angle of left femur was found to be slightly higher than that of right side in most of the studies. Similar was the case in our study with mean bicondylar angle on left femur 9.35°, slightly higher than that of right femur 8.65°. But the side difference of bicondylar angle was not proved to be statistically significant in any of the study.[6,7,8,9,10,11]

Pandya et al., Ukoha et al., and Jyothi et al. found the bicondylar angle to be statistically higher in female compared to that of male on both sides which they believed to be because of wider pelvis in female.[6,8,10] Whereas, the studies carried by Mahajan et al., Sharma et al., and Biswas et al. did not find the gender difference of bicondylar angle.[7,9,11]

Jyothi et al. found bicondylar angle to have strong negative correlation with femur length hypothesizing that larger the bicondylar angle, lesser will be the femoral length.[10] Likewise, in this study bicondylar angle of left femur was negatively correlated with the femur length and femoral neck length although the finding was not statistically significant.

Although this study comply with other studies on having greater but not significant bicondylar angle in left femur compared to right, further research has to be undertaken on larger sample size, different race, regions, age, and sex. With further workup, bicondylar angle may be developed as a tool for sex determination.

Mean bicondylar angle was 8.65° (SD = 2.03) and 9.35° (SD = 2.05) in right and left femur respectively and the difference was not statistically significant. There was no significant correlations between bicondylar angle and other femoral parameters.