IMPACTS OF FOOT STRUCTURE, TASK DEMAND, FLOORING, AND FOOTWEAR ON METATARSOPHALANGEAL JOINT CONTACT FORCES AND METATARSAL BONE STRESS

Abstract

Forefoot injuries in athletes and tactical athletes commonly include metatarsalgia, sesamoiditis, Morton’s neuroma, and metatarsal stress injuries that occur due to the accumulation of tissue damage from repetitive cyclic loading during training and competition. The high incidence of forefoot injuries and metatarsal bone stress injuries (BSI) among athletes and tactical athletes is a concerning issue in need of further study. Hence, the overarching goal of this dissertation project was to investigate the role of internal as well as external modifiable factors on forefoot bone and joint forces, the proximate cause of tissue damage and injury, using a novel musculoskeletal modelling approach. When we examined the effects of exertion during prolonged walking and rucking tasks on the second metatarsophalangeal (MTP) joint loading and second metatarsal bone stresses, the peak MTP JCF reduced after exertion due to a reduction in peak toe flexor force. However, there was a compensatory increase in the bending moment with exertion that prevented the reduction of metatarsal stresses. As a result, the reduction of muscle forces with exertion increased loading on the static structures like bones, increasing the injury risk. The effects of task demand, flooring surface, and arch stiffness on the second MTP JCF and metatarsal stresses were also observed. The JCF and the bone stresses increased with increasing task demands, with the highest forces and stresses observed during sprinting, followed by running, and then by walking. The cushioned sports-court flooring reduced the metatarsal stresses only during sprinting, while there was no reduction in the JCF. Lastly, the arch stiffness did not show any association with higher bone stresses. This suggests that the individuals participating in activities with higher task demand are at a higher risk of getting forefoot injuries, irrespective of their arch stiffness. Furthermore, participating in such activities on a sports-court flooring may lower the peak bone stresses at the 2nd metatarsal. Finally, the effects of footwear, running speed, and dynamic arch function on 2nd MTP JCF and 2nd metatarsal stresses were observed in the last study. Consistent with previous findings, running at faster speeds increased the MTP JCF and the metatarsal bone stresses with the highest peak stresses and JCF observed at 40% faster running speeds, followed by 20% faster speed, and then at the preferred running speed. The carbon-fiber shoes reduced peak metatarsal stresses as well as peak MTP JCF during running at all speeds. Additionally, consistent with a previous study, there was no correlation between arch rise and peak dorsal stresses. This suggested that stiffer arches do not reflect increased peak metatarsal stresses. In conclusion, forefoot injury prevention efforts should target athletes and tactical athletes participating in prolonged, repetitive gait tasks and at faster speeds. This includes military service members, cross-country runners, as well as marathon runners. Furthermore, muscle endurance training, training over cushioned sports-court flooring, and use of stiffer shoes with advanced footwear technology could have a place in forefoot injury prevention and treatment efforts.