Repetitive high-pressure loading under the metatarsal heads and hallux often cause foot complications like diabetic ulceration, metatarsalgia, and rheumatoid arthritis. While footwear and its interventions like rocker shoes and metatarsal pads have been shown to be effective in reducing these high-pressures under the forefoot when used individually, the potential of the combination to reduce peak pressures under the forefoot has not been quantified. Also, sensitivity analysis of critical parameters like optimal in-shoe placement and size of metatarsal pad and effect of various insole materials using computational modeling remains unstudied. This methodology would reduce the high volume experimentation and enhance the scientific basis of orthotic design and testing of footwear.

The objectives of this work were i) to explore first ray complications like hallux rigidus and arthrodesis, and investigate footwear intervention by creating a partial finite element model of the forefoot, Chapter 2, ii) explore the pressure reduction properties of such a combined prescription against the sole use of a rocker shoe or a metatarsal pad using a forefoot model, Chapter 3, iii) devise a computational platform to perform footwear simulation solely based on barefoot plantar pressure measurements, and perform a sensitivity analysis of in-shoe placement and size of MT pad on plantar pressure reduction, Chapter 4.

A validated finite element model of a partial foot was created from magnetic resonance images and first ray complications like hallux rigidus, arthrodesis, and design of footwear was conducted to meet the first goal. Barefoot and footwear experiments using rocker shoes and metatarsal pads were conducted to test their individual effectiveness and in combination. A representative subject from this study was selected and a finite element model of that subject’s forefoot and shoes and metatarsal pads used for the study were created. Using interactions between finite element modeling and optimization techniques, second and third goals of this work were tested.

The partial model of the foot was successfully able to simulate first ray complications and test various insole materials for its effectiveness in reducing peak pressures under the forefoot. The model was also able to simulate the push-off phase of walking which demonstrated the occurrence of peak hallux and metatarsal head pressures. The experiments conducted on human subjects showed that rocker shoes and metatarsal pads were effective in reducing hallux and metatarsal head pressures respectively. The experiments further showed that their combination was able to reduce both hallux and metatarsal head pressures effectively. Sensitivity of in-shoe metatarsal pad placement and size of the forefoot showed that a larger size metatarsal pad placed at 5 mm proximal to peak metatarsal head pressure was most effective in reducing plantar pressures under the forefoot. This collection of studies demonstrated the role of computational modeling and optimization techniques to predict in-shoe plantar pressures and use them for design of therapeutic footwear interventions.