A dynamic model of the windlass mechanism of the foot: evidence for early stance phase preloading of the plantar aponeurosis

Abstract

In the present study we have estimated the temporal elongation of the plantar aponeurosis (PA) during normal walking using a subject-specific multi-segment rigid-body model of the foot. As previous studies have suggested that muscular forces at the ankle can pre-load the PA prior to heel-strike, the main purpose of the current study was to test, through modelling, whether there is any tension present in the PA during early stance phase. Reflective markers were attached to bony landmarks to track the kinematics of the calcaneus, metatarsus and toes during barefoot walking. Ultrasonography measurements were performed on three subjects to determine both the location of the origin of the PA on the plantar aspect of the calcaneus, and the radii of the metatarsal heads. Starting with the foot in a neutral, unloaded position, inverse kinematics allowed calculation of the tension in the five slips of the PA during the whole duration of the stance phase. The results show that the PA experienced tension significantly above rest during early stance phase in all subjects (P<0.01), thus providing support for the PA-preloading hypothesis. The amount of preloading and the maximum elongation of the slips of the PA decreased from medial to lateral. The mean maximum tension exerted by the PA was 1.5 BW (body weight) over the three subjects.

Biomechanical Analysis of Achilles Tendon Stretch And Plantar Fascia Stretch In Plantar Fasciitis Treatment

“…Plantar fascia stretch generated a larger deformation so the stimulation on plantar fascia was supposed to be better. Meanwhile, the 1st ray of plantar fascia both had larger deformation than the rest four rays in two stretching simulation, which complies with previous research [24].…”

“…Plantar fascia have been modelled as five rays corresponding to the order of five metatarsal. One special structure in plantar fascia model were four spheres locating beneath each metatarsal head which had contact with metatarsal so to simulate the interaction of plantar fascia with metatarsal in vivo [24]. Stiffness and damping ratio were defined according to previous researches [25].…”

Kinematic correlates of walking cadence in the foot

“…1), according to Leardini et al (2007). Before starting the walking trials, in order to define the neutral position of the foot, a 1 s static acquisition was taken with the subject standing still in a right-leg support (Caravaggi et al, 2009), the left foot in contact with the floor but with minimum load, i.e. no-weight bearing for the analysed leg.…”

Arboreality, terrestriality and bipedalism

“…Perhaps most importantly, we can optimize muscle properties during rapid changes in speed and changes in incline in both running and walking (Lichtwark & Wilson 2006, 2007. We have suggested that increased stiffness results from pre-tension applied to the plantar aponeurosis (PA) by heel-strike or earlystance muscle activity (in triceps, tibialis anterior and the digital dorsiflexors; Pataky et al 2008;Caravaggi et al 2009). The windlass mechanism created as the PA wraps round the heads of the metatarsals (figure 1a) is known to contribute to stiffen the foot in late stance (Hicks 1954) by pulling on the calcaneus, causing inversion of the subtalar joint and hence 'locking' the midtarsal joint (Tansey & Briggs 2001).…”