Biomechanical consequences of plantar fascial release or rupture during gait: Part I - Disruptions in longitudinal arch conformation

To examine whether conformational changes induced by plantar fascial divisi on may progress during gait, we loaded the feet of seven cadavers using an apparatus that simulates the actions of the extrinsic plantarflexors. We me asured the effects of plantar fasciotomy at two instants in the terminal-st ance phase of gait. Radiographic measurements of height of the arch, base l ength of the arch, and tate first-metatarsal angle were used to assess cont ributions to arch support made by the plantar fascia, tibialis posterior, p eroneus longus and brevis, and digital flexor muscles. Complete fasciotomy caused significant collapse of the arch in the sagittal plane. Early in ter minal stance, at the instant after heel-off, mean height of the arch decrea sed from 47 to 45 mm. Late in terminal stance, at the instant preceding con tralateral heel strike, mean height of the arch decreased from 46 to 43. Ef fects of division of the central band, though significant, were mild. Media l base length of the arch increased from 163 to 167 mm in the absence of ti bialis posterior contraction at late terminal stance. Arch-supporting abili ties of the other extrinsic muscles were insignificant.