The goal of this study was to analyse the biomechanical behavior of the second metatarsal bone after flexor digitorum brevis tendon transfer (FDBT), flexor digitorum longus tendon transfer (FDLT), or proximal interphalangeal joint arthrodesis (PIPJA) on the second toe to determine whether these operations relieve traction, compressive stresses, and strain at that site.
The authors sought to determine whether these surgical interventions represent an improvement from a biomechanical point of view.
The foot geometry was obtained from 93 tomographic images from a healthy 36-year-old man.
The connections among the different bones were modeled as cartilaginous joints.
The ligaments were modeled using a set of 483 incompressible, unidimensional elements.
The osseous tissue was modeled, differentiating the cortical part from the spongy part, and both parts were considered elastic and isotropic.
The stance phase of gait is divided into different positions: initial contact, heel strike, midstance, forefoot contact, push-off, and toe-off. For the purpose of this study, the push-off or toe-off was reproduced.
Finally, using data from the literature for a patient with a mass of 60 kg, a load of 180.5 kg was established and divided into 180 kg of normal force to the joint surface and 12 kg of tangential component of force to this surface.
PIPJA showed a higher increase in traction and compression stresses and strains at the medial aspect of the shaft of the second metatarsal bone compared with FDLT or FDBT, and increased traction strain at the dorsal aspect of the second metatarsal bone.
Based on these findings, the authors recommend surgical correction using FDLT or FDBT rather than PIPJA to reduce traction stress on the second metatarsal bone.
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