Biomechanical study of foot with hallux valgus deformity

Abstract

Background: Hallux valgus (HV) is one of the most common foot deformities. Considering the fact that 23% of adults develop such condition during their lifetime, understanding HV is badly needed. Plantar pressure technologies are used widely for determination of biomechanical changes in foot during walking. There are already published claims relating to the pressure distribution of HV condition. Association of HV to sole pressure widely presented as a means of identifying such condition. Methods: plantar pressure patterns can be linked to the deformity progression or existence, extracting some patterns out of force measurements can be beneficial in recognizing the patients with and without deformity. The dynamic changes of the forces that applied to the fore-foot in volunteers with and without HV when they walked at self-selected and fast speeds were examined. Furthermore, Markovian chain transfer matrices were used to obtain the transfer coefficient of the force among five metatarsals. Another method was to measure the lateral flexibility of the 1st metatarsal joint as an indication of HV deformity by Motion Capture cameras. Finally, two 3D feet models of HV and non-HV volunteers were made in Mimics software and then in FEA (finite element analysis) the stress distribution under the foot was validated with the experiments. Results: The higher forces were observed under the 2nd, 3rd and 1st metatarsal heads in both speeds but the results obtained were significantly different among groups and in fast speed and under 3rd and 1st metatarsals in self-selected speed. In this study the use of Markovian transfer matrices as a means of characterising the gait pattern is new and novel. It was intended that highest coefficients of the matrix would indicate the existence of HV, however studies showed that the biggest difference between HV and non HV patients was the scatter of the coefficients which shown to give very strong indication of the existence of HV. It was shown by kinematic studies and also it was found that the 1st metatarsal joint was significantly more flexible in HV patients compared to non–HV individuals. Finally FEA studies has shown that in the 3D feet models of both volunteers (with and without HV), the highest stress was under the heal area and then transfers towards fore-foot area. In patient with HV the higher force were seen under the 1st to 3rd metatarsal heads compare to non-HV individual and each model was validated its related experiments. Conclusion: it was observed that there was a significant variability of pressure distribution of the same individual from one trial to another indicating that getting consistent pressure pattern is an important hurdle to overcome in our studies, raised loading is observed on Metatarsal 2, 3 and 1 in HV patients and it was possible to give statistical significance to these findings. In this thesis, it was intended to obtain early diagnostics of HV condition and much work was put in this, however outcome was not conclusive. However it was possible to distinguish HV form non-HV volunteers from the scatter characteristics of the transfer pattern. Investigation of the 1st metatarsal joint laxity of non-HV and HV patients revealed that HV individuals were significantly higher compared to non–HV volunteers and this can be used as an indication of HV existence. Finally, the 3D models show that FEA is a reliable tool as the FEA study showed good correlation with the experimental results.