Trabecular mapping of the human distal femur: Leveraging geometric morphometrics for studies of bone microstructure

Abstract

Trabecular microstructure of limb bone epiphyses have been used to elucidate the relationship between skeletal form and locomotor behaviors among mammals. Such studies have often relied on the analysis of a single volume of interest (VOI) placed within the trabecular structure. Trabecular structure likely varies across continuous regions of bone and a single VOI will miss this variation, and much of the functional signal will be lost.Here I present a method for evaluating variation in bone microstructure across articular surfaces by leveraging sliding landmarks to sample multiple VOIs. 1007 sliding semi‐landmarks were distributed across the articular surface of 10 human distal femora using standard geometric morphometric procedures. Landmarks were then used to locate the positions of 1007 VOIs in the trabecular structure immediately deep to the cortical shell. VOIs were extracted and trabecular properties were measured for each VOI using BoneJ. Two questions are addressed: 1) are microstructural variables homogeneous across the articular surface? and 2) if microstructure is not homogeneous, are values of microstructural variables patterned on the condyles in a way that reflects human walking?Results suggest that trabecular microstructural variables are not homogenous across human femoral condyles. Bone volume fraction and trabecular thickness were greatest on the most inferior portions of the condyles, suggesting these areas reflect loading of the joint during normal walking. The technique presented here may have applications for reconstructing locomotion behavior of extinct animals as well as evaluating bone strength in clinical practice.