title: Changes in length of the plantar aponeurosis during the stance phase of gait--an in vivo dynamic fluoroscopic study.
abstract: In locomotion, ligaments and muscles have been recognized to support the arch of the foot. However, it remains unclear to what extent the passive and active structures of the lower extremity support the longitudinal arch of the foot during walking. In this study, the mechanical function of the plantar aponeurosis (PA) is investigated by elongation measurements in vivo during the stance phase of gait, in combination with measurements of the mechanical properties of the PA in vitro. Fluoroscopy was used to measure the dynamic changes in PA length and the angular motion of the metatarsophalangeal joint of the first ray, measured during the stance phase (StPh) in 11 feet. Simultaneously, ground forces were measured. Additionally, four cadaver feet delivered topographic information relating to the PA, and three autopsy specimens of PA served to determine the in vitro mechanical properties of PA. The present study revealed a non-significant peak average PA shortening of 0.48% at about 32.5% StPh, followed by a significant average peak elongation of 3.6% at 77.5% StPh. This average peak elongation of 3.6% corresponds to a force of 292N, as estimated by mechanical testing of the autopsy PA specimens. Considering the maximum peak elongation measured in one volunteer of 4.8% at 76% StPh, a peak PA load of 488N might be expected. Hence, with an average body weight of 751N, as allocated to the 11 investigated feet, this maximum peak force would correspond to about 0.65×body weight. As far as we are aware, this is the first report on a dynamic fluoroscopic study of the PA in gait with an appreciable number of feet (11 feet). In conclusion, muscles contribute to support of the longitudinal arch of the foot and can possibly relax the PA during gait. The 'windlass effect' for support of the arch in this context is therefore questionable.
authors.affiliation: Institute for Biomechanics, ETH & University of Zurich, Balgrist, Forchstrasse 340, CH-8008 Zurich, Switzerland. Electronic address: gfessel@ethz.ch.
authors.forename: G
authors.initials: G
authors.lastname: Fessel
authors.affiliation: Consultant in Orthopaedic Biomechanics, Gernstrasse 128, CH-8409 Winterthur, Switzerland. Electronic address: hilaire.jacob@bluewin.ch.
authors.forename: H A C
authors.initials: HA
authors.lastname: Jacob
authors.affiliation: Head of Laboratory for Movement Analysis University Children's Hospital Basel, University of Basel, Spitalstrasse 33, CH-4056 Basel, Switzerland. Electronic address: christian.wyss@unibas.ch.
authors.forename: Ch
authors.initials: Ch
authors.lastname: Wyss
authors.affiliation: Department of Traumatology and Reconstructive Surgery, University of Rostock, Schillingallee 35, D-18055 Rostock, Germany. Electronic address: thomas.mittlmeier@med.uni-rostock.de.
authors.forename: Th
authors.initials: T
authors.lastname: Mittlmeier
authors.affiliation: Institute of Anatomy, University of Basel, Pestalozzistrasse 20, CH-4056 Basel, Switzerland. Electronic address: m.mueller-gerbl@unibas.ch.
authors.forename: M
authors.initials: M
authors.lastname: Müller-Gerbl
authors.affiliation: Institute of Forensic Medicine, University of Rostock, St. -Georg-Strasse 108, D-18055 Rostock, Germany. Electronic address: andreas.buettner@med.uni-rostock.de.
authors.forename: A
authors.initials: A
authors.lastname: Büttner
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D055119:Elastic Modulus / Q000502:physiology; D005205:Fascia / Q000033:anatomy & histology* / Q000000981:diagnostic imaging / Q000502:physiology*; D005260:Female; D005471:Fluoroscopy / Q000379:methods*; D005528:Foot / Q000033:anatomy & histology* / Q000000981:diagnostic imaging / Q000502:physiology*; D005684:Gait / Q000502:physiology*; D006801:Humans; D008297:Male; D008875:Middle Aged; D013718:Tensile Strength / Q000502:physiology; D016138:Walking / Q000502:physiology*; D055815:Young Adult
keywords: Anatomical study; Biomechanics; Plantar fascia; Stress–strain; Windlass effect