Third Trochanter of Femur: Evolutionary and Biomechanical Significance

Abstract

Introduction: The third trochanter (TT) is a conical, oblong or rounded bony prominence present on the upper margin of the gluteal tuberosity in some femurs. Variable prevalence of TT has been reported by different investigators. It has also been studied as a non-metric (qualitative) trait in the study of the appendicular skeletal system in mammals. The presence of TT has a known effect on alteration of break lines in cases of pertrochanteric femoral fractures. Present study aims to examine the prevalence of the third trochanter along with morphometric assessment in dry human femur and a discussion on its evolutionary and biomechanical significance. Material and Methods: 86 dry human femurs were studied for the presence of TT, their location, extent and relationship to the greater and lesser trochanter using digital vernier calliper and non-stretchable measuring tape. Results: The TT was observed in 8 % of the studied bones. The mean maximum length and width of all TT of femurs were 2.25 cm and 0.80 cm respectively. The mean distance of TT from greater and lesser trochanter were 5.34 cm and 2.50 cm respectively. Though a right sided preponderance was noted in its occurrence, it was not found statistically significant. Conclusion: The findings of the present study corroborate well with the existing literature. These findings might be a useful dataset for studying the anthropology and evolution of mammalian femur. The evolutionary and probable biomechanical significance of TT was also highlighted. High quality clinical studies need to be conducted to provide strong evidence for its association with pathological condition and exact role in biomechanics.