Abstract
Hallux valgus (HV), the bunion of the first metatarsophalangeal joint (MTPJ), bothers many adults. No consensus has been reached about the causes of HV, be it a hereditary, or acquired, or multifactorial disease. Nor has agreement been reached using MTPJ angle to assess HV based on X-ray because in most cases the assessment of MTPJ is not reliable as it depends on the posture during scanning. In this study, we assume that HV is predominately acquired and that shoe wearing per se is an important player in HV pathogenesis. To verify our hypothesis, a CT-based finite element (FE) model of the first MTPJ of fossil remains of bear-footed Homo naledi was created and compared to that of five contemporary shoe-wearing wrestlers (10 models from two scans at an interval of about 18 months) because Homo naledi's first MTPJ is an ideal model for non-shoe wearing with parallel sesamoid grooves. We developed the first MTPJ structure transformation method and created MTPJ joint capsule model for both Homo naledi and wrestlers. Constraint on the medial side of the first MTPJ capsule was set to simulate shoe-wearing conditions compared to the lack of medial constraint for barefooted conditions. Analysis of eight FE models of different angles for the first MTPJ of Homo naledi was performed by the first MTPJ transformation method and results showed that stress concentrated on the medial capsule of the first MTPJ in simulated shoe-wearing conditions, even at MTPJ angle of 0°. Increase in the first MTPJ angle further increased stress concentration on the medial side, and stress-growth relationship might reveal the causes of HV. We further developed a method to position the first MTPJ in wrestlers and created CT-based models at two time points. It was evident that the first MTPJ angle increased in all but one athlete, with a maximal increase of 4.03 degrees. This verifies our hypothesis that HV might be developed by wearing shoes. Further longitudinal studies with larger sample sizes are needed to additionally validate our results and determine the magnitude of the effects of shoe wearing on development and progression of HV.
Highlights
Hallux valgus (HV), the bunion of the first metatarsophalangeal joint (MTPJ), is the most common foot deformity leading patients to visit a podiatric specialist in Europe (Crevoisier et al, 2016)
This is important to consider in modern population having in mind that footwear plays an instrumental role in our daily life by providing us with safety and comfort, foot protection, prevention of slipping, and absorbing ambulatory shock, but wearing ill-fitting shoes was shown to lead to foot deformities among 60% adults (Klein et al, 2009)
It is obviously shown that when wearing shoes, comparing the angle of 21 and zero, the maximum, minimum and Von Mises stress difference is 2.26, 2.55, and 1.51 times, suggesting that as the HV angle increases, the maximum and minimum principal stress increase at the angle of 21
Summary
Hallux valgus (HV), the bunion of the first metatarsophalangeal joint (MTPJ), is the most common foot deformity leading patients to visit a podiatric specialist in Europe (Crevoisier et al, 2016). Despite the numerous studies the mechanism behind the HV remains controversial (Nix et al, 2010; Crevoisier et al, 2016), with agreement that the leading causes could be heredity (genetic) and environmental (ill-fitting shoe wearing) (Piqué-Vidal et al, 2007; Nguyen et al, 2010). The association of HV with shoe wearing is not investigated in detail This is important to consider in modern population having in mind that footwear plays an instrumental role in our daily life by providing us with safety and comfort, foot protection, prevention of slipping, and absorbing ambulatory shock, but wearing ill-fitting shoes was shown to lead to foot deformities (including HV) among 60% adults (Klein et al, 2009). No fossil footprint was reported with HV Taken together, these might suggest that ill-fitting shoe wearing is the leading cause in the pathogenesis of HV. Longitudinal follow-up of the contemporary wrestlers’ MTPJ was undertaken to follow the real-life effect of footwear on HV development
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