Reconstructing the First Metatarsophalangeal Joint of Homo naledi

Abstract

The aim of the present study was to develop a new method to reconstruct damaged metatarsophalangeal joint (MTPJ) of Homo naledi 's fossil and to deepen the understanding of the first metatarsal head (FMH) morphological adaptation in different gait patterns. To this purpose three methods were introduced. The first served to compare the anthropometric linear and volumetric measurements of Homo naledi 's MTPJ to that of 10 various athletes. The second was employed to measure curvature diameter in FMH's medial and lateral grooves for sesamoid bones. The third was used to determine the parallelism between medial and lateral FMH grooves. The anthropometric measurements of middle-distance runner to the greatest extent mimicked that of Homo naledi . Thus, it was used to successfully reconstruct the damaged Homo naledi 's MTPJ. The highest curvature diameter of medial FMH groove was found in Homo naledi , while in lateral FMH groove it was the highest in volleyball player, suggesting their increased bear loading. The parallelism of medial and lateral FMH grooves was observed only in Homo naledi , while in investigated athletes it was dis-parallel. Athletes' dis-paralleled structures make first MTPJ simple flexion movement a complicated one: not rotating about one axis, but about many, which may result in bringing a negative effect on running. In conclusion, the presented method for the reconstruction of the damaged foot bone paves the way for morphological and structural analysis of modern population and fossil hominins' gait pattern.

Asymptomatic foot and ankle structural injuries: a 3D imaging and finite element analysis of elite fencers

“…Thresholding, region growing, and morphology operations were used to reconstruct the tibia, fibula, tarsus, metatarsals, and sesamoids of participants in Mimics. A previously described method [ 20 ] was used to measure the curvature diameter of the sesamoid groove (SG) of the first metatarsal bone (Fig. 1 ).…”

The Role of Footwear in the Pathogenesis of Hallux Valgus: A Proof-of-Concept Finite Element Analysis in Recent Humans and Homo naledi

“…To simulate the pathological process, we created 8 FE models of Homo naledi in shoe-wearing and bare-footed conditions. a) To standardize the body coordinate system of the repaired first metatarsal, first proximal and distal phalange (Fan et al, 2019) and the mirrored medial cuneiform, i.e., to calculate PAE for first metatarsal by using the PAE as its own body coordinate and setting the origin on its centroid. Rate the standardized body coordinate of the first metatarsal along the long axis by percentage, thus standardize the first metatarsal, the great toe proximal and distal phalanx geometrically.…”

“…Simulation was performed as follows: in barefooted condition, no geometric constraint was applied to the medial side of the first MTPJ capsule while in shoe-wearing condition, constraint was applied (Sousa et al, 2012 ). To build the geometric model of MTPJ that has no experience of wearing shoes, we chose the MTPJ (Fan et al, 2019 ) and mirrored medial cuneiform (Li et al, 2019 ) of Homo naledi to build 8 geometric models. This is not a complete reverse reconstruction model, but eight FE models of different angles.…”

“…Therefore, parallel first MTPJ grooves are important. Shoe-wearing stress might lead to structural change, i.e., unparalleled first MTPJ grooves (Fan et al, 2019 ).…”

“…Another issue is to include the joint capsule in the finite element (FE) analysis of the first MTPJ, which was missing in previous studies (Yu et al, 2008 ). Therefore, to address the question whether shoe wearing contributes to the occurrence of HV in this study, we developed geometric and FE model of the first MTPJ in Homo naledi (Berger et al, 2015 ) [an extinct hominine species who had no experience of shoe wearing, with parallel sesamoid grooves (Fan et al, 2019 )] and of the first MTPJ of contemporary wrestlers, and evaluated their biomechanical characteristics in simulated shoe-wearing and barefooted conditions (Sousa and Tavares, 2014 ). Longitudinal follow-up of the contemporary wrestlers' MTPJ was undertaken to follow the real-life effect of footwear on HV development.…”