Relationship between plantar pressure and soft tissue strain under metatarsal heads with different heel heights

Background: Metatarsalgia due to increased plantar pressure under the metatarsal head (MTH) is often seen with wearing high-heeled shoes. However, the concomitant soft tissue strain has not been well discussed. The objective of our study was to explore the standing plantar pressure and corresponding soft tissue strain under the metatarsal heads (MTHs) with different heel heights. Materials and Methods: Twenty-one healthy subjects (10 male and 11 female) participated. The plantar pressure and soft-tissue thicknesses were measured simultaneously with a load cell and a 10-MHz linear-array ultrasound (US) transducer respectively. The changes in plantar pressure and soft tissue strain under the MTHs were analyzed for different heel heights. Results: As hypothesized, plantar metatarsal pressure significantly increased and shifted to the first and second MTHs with increasing heel height from 2 cm to 4 cm(p <0.05). However, the change in soft tissue strain under the medial forefoot became insignificant when the heel height was greater than 2 cm (p = 0.473 and 0.517). Conclusions: Increased heel height resulted in increasing medial forefoot loading pressure; however, the soft tissue exhibited stationary compressibility when the heel height was greater than 2 cm. Clinical Relevance: Our finding provides an understanding of the biomechanical changes with wearing high-heeled shoes and suggests possible strategies to reducing discomfort and risk of injury, such as limiting heel height to no greater than 2 cm and using medial padding under MTHs.