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The plantar aponeurosis (PA), in spanning the whole length of the plantar aspect of the foot, is clearly identified as one of the key structures that is likely to affect compliance and stability of the longitudinal arch. A recent study performed in our laboratory showed that tension/elongation in the PA can be predicted from the kinematics of the segments to which the PA is attached. In the present investigation, stereophotogrammetry and inverse kinematics were employed to shed light on the mechanics of the longitudinal arch and its main passive stabilizer, the PA, in relation to walking speed. When compared with a neutral unloaded position, the medial longitudinal arch underwent greater collapse during the weight-acceptance phase of stance at higher walking speed (0.1 degrees +/-1.9 degrees in slow walking; 0.9 degrees +/-2.6 degrees in fast walking; P = 0.0368). During late stance the arch was higher (3.4 degrees +/-3.1 degrees in slow walking; 2.8 degrees +/-2.7 degrees in fast walking; P = 0.0227) and the metatarsophalangeal joints more dorsiflexed (e.g. at the first metatarsophalangeal joint, 52 degrees +/-5 degrees in slow walking; 64 degrees +/-4 degrees in fast walking; P < 0.001) during fast walking. Early-stance tension in the PA increased with speed, whereas maximum tension during late stance did not seem to be significantly affected by walking speed. Although, on the one hand, these results give evidence for the existence of a pre-heel-strike, speed-dependent, arch-stiffening mechanism, on the other hand they suggest that augmentation of arch height in late stance is enhanced by higher forces exerted by the intrinsic muscles on the plantar aspect of the foot when walking at faster speeds.
Re: Dynamics of longitudinal arch support in relation to walking speed: contribution of the plantar aponeurosis
Relative contributions of plantar fascia and ligaments on the arch static stability: a finite element study.
Tao K, Ji WT, Wang DM, Wang CT, Wang X. Biomed Tech (Berl). 2010 Sep 15.
The plantar fascia (PF) and major ligaments play important roles in keeping the static foot arch structure. Their functions and relative contributions to the arch stability have not been well studied. A three-dimensional finite element foot model was created based on the reconstruction of magnetic resonance images. During balanced standing, four cases after individual releases of the PF, spring ligament (SL), and long and short plantar ligaments (LPL and SPL) were simulated, to compare their biomechanical consequences with the normal predictions under the intact structure. Although the predictions showed the arch did not collapse obviously after each structure sectioning, the internal mechanical behaviors changed considerably. The PF release resulted in the maximal increases of approximately 91%, 65% and 47% in the tensions of the LPF, SPL and SL, produced the largest changes in all bone rotations, and brought an obvious shift of high stress from the medial metatarsals to the lateral metatarsals. The SL release mainly enhanced bone rotation angles and weakened the joint stability of the arch structure. The LPL and the SPL performed the roles of mutual compensation as either one was released. The influence of the LPL on the load distribution among metatarsals was greater than for the SPL and the SL.