9 - Lateral Plantar Process Trabecular Structure Relative to Other Regions of the Calcaneus

Poster Board Number: 9
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Abstract Body : The calcaneal lateral plantar process (LPP) is unique to humans and is thought to be weight-bearing during heel strike, similar to the calcaneal tuberosity. Previous work on the LPP has focused on external morphology, but the internal structure has yet to be examined. Here, we compare LPP trabecular properties to the rest of the calcaneus in modern humans (n=20) to investigate how LPP internal structure varies relative to other weight-bearing portions of the calcaneus, such as the tuberosity.

Calcanei were micro-CT scanned (voxel size 36 microns). The output from a weighted spherical harmonic analysis was used to position 226 spherical volumes of interest (VOIs). Trabecular parameters (i.e., trabecular thickness (Tb.Th), trabecular spacing (Tb.Sp) , degree of anisotropy (DA), and bone volume fraction (BV/TV)) were calculated using the BoneJ plugin for ImageJ and MATLAB. Pairwise Wilcoxon Rank Sum tests were performed between average trabecular parameters of the LPP relative to different calcaneal regions (i.e., tuberosity, tuber, posterior talar facet (superficial and deep below analyzed separately), anterior calcaneus, and sustentaculum tali). Trabecular parameters were visualized using color maps.

There is no significant difference in BV/TV of the LPP and the tuberosity (p=0.561), which supports previous suggestions that the LPP is a weight-bearing structure. The plantar portion of the tuberosity and LPP do not significantly differ in DA (p=0.854), suggesting potentially similar directions of load transmission through both regions. The LPP has relatively higher Tb.Th than the tuberosity (p=0.024), but relatively lower Tb.Sp (p=0.049). These differences in LPP trabecular structure may be because forces experienced by the LPP are transmitted across a smaller surface area than those transmitted across the tuberosity. In all trabecular parameters, the LPP differs significantly with trabeculae in the anterior calcaneus and sustentaculum tali (p< 0.012 for pairwise comparisons), indicating different trabecular patterns between articular surfaces and structures contacting the substrate. Structural similarity of the LPP to other weight-bearing calcaneal structures expands our understanding of calcaneal functional adaptation, which is critical for enhancing approaches to gait pathologies.