Biomechanical consequences of plantar fascial release or rupture during gait - Part II: Alterations in forefoot loading

With a model using feet from cadavers, we tested the hypothesis that planta r fascial release or rupture alters the loading environment of the forefoot during the tatter half of the stance phase of gait. The model simulated th e position and loading environment of the foot at two instants: early in te rminal stance immediately after heel-off and late in terminal stance just p receding contralateral heel strike. Eight feet were loaded at both position s by simulated plantar flexor contraction, and the distribution of plantar pressure was measured before and after progressive release of the plantar f ascia. Strain in the diaphysis of the second metatarsal was also measured, from which the bending moments and axial force imposed on the metatarsal we re calculated. Cutting the medial half of the central plantar fascial band significantly increased peak pressure under the metatarsal heads but had li ttle effect on pressures in other regions of the forefoot or on second meta tarsal strain and loading. Dividing the entire central band or completely r eleasing the plantar fascia from the calcaneus had a much greater effect an d caused significant shifts in plantar pressure and force from the toes to beneath the metatarsal heads. These shifts were accompanied by significantl y increased strain and bending in the second metatarsal. Complete fasciotom y increased the magnitude of strain in the dorsal aspect of the second meta tarsal by more than 80%, suggesting that plantar fascial release or rupture accelerates the accumulation of fatigue damage in these bones. Altered for efoot loading may be a potential complication of plantar fasciotomy.