The effect of orthotics onin vivoaxial tibial and second metatarsal strains

Background: In a previous military study a custom-made tri-layer polyurethane shoe orthotic was shown to be effective in lowering the incidence of stress fractures in infantry recruits. Stress fractures are caused by repetitive high strains. Objective: To compare the effect of tri-layer polyurethane orthotics with other types of orthotics on in vivo strains at sites where stress fractures are common. Design: Subjects underwent surgical implantation of strain gauged staples to the dorsal surface of the midshaft 2nd metatarsal and to the medial surface of the midshaft tibia. Setting: University Hospital. Patients: Two male members of the research staff aged 40 and 54. Measurements: In vivo simultaneous peak-to-peak axial compression-tension strains during treadmill walking at 5 km/h while wearing standard army boots and Nike Air Max running shoes with and without either a non custom pre-fabricated orthotic with a three-quarter length thermocork module, a semirigid custom-made orthotic, with a three-quarter ...