ABSTRACT
Mild, temporary reduction of symptoms from plantar fasciitis have been reported with the use of high heeled shoes (i.e. cowboy boots, ladies pumps). However, little is known on how heel elevation may contribute to a decrease in the pain and inflammation. The aim of this study was to quantify strain in the plantar aponeurosis in cadaveric feet with the use of various heel elevation configurations. An in vitro method that simulated "static" stance was used to determine the loading characteristics of the plantar aponeurosis (n = 12). Heel elevation was evaluated with blocks placed beneath the heel and with a contoured platform that simulated the arch profile of a shoe at three different heel heights (2.0, 4.0, 6.0 cm) with a level plane serving as the control. Strain in the plantar aponeurosis decreased with elevations of the heel that simulated the arch profile of a shoe at load levels (337, 450 N) (P < 0.05). Elevations of the heel with blocks did not significantly affect strain in the plantar aponeurosis (P < 0.05). Contrasting results of some specimen limbs compared with the overall means suggests that the influence of heel elevation on loading of the plantar aponeurosis may be dependent on individual variation and foot structure differences. Therefore, clinicians should be cautious in recommending heel elevation as a treatment for plantar fasciitis since some subjects may not achieve the desired decrease in plantar aponeurosis strain.
Subject(s)
Fascia/physiology , Fasciitis/therapy , Foot Diseases/therapy , Foot/physiology , Heel/physiology , Orthotic Devices , Shoes , Adult , Aged , Biomechanical Phenomena , Cadaver , Female , Humans , In Vitro Techniques , Male , Middle Aged , Models, Biological , Reproducibility of Results , Weight-BearingABSTRACT
BACKGROUND: Repetitive trauma and overuse of the plantar aponeurosis are believed to be causal factors of plantar fasciitis. Therefore, it is important to know how an orthosis influences loading of the plantar aponeurosis. The aim of this study was to quantify strain in the plantar aponeurosis in cadaveric feet with the use of various combinations of orthotic wedges. METHODS: An in vitro test that simulated static stance was used to determine the loading characteristics of the plantar aponeurosis. A differential variable reluctance transducer was operatively implanted into the plantar aponeurosis of nine fresh-frozen cadaveric lower limbs. Each specimen was mounted in an electromechanical testing machine that applied an axial load of as much as 900 newtons to the tibia. Eight different combinations of test conditions, in which wedges (each with a 6-degree incline) were or were not positioned under the medial and lateral aspects of the forefoot and hindfoot, were evaluated, with the plantigrade foot used as a neutral control. RESULTS: Each of the test conditions that involved a wedge under the forefoot resulted in strain that was significantly different from that in the neutral control. A wedge under the lateral aspect of the forefoot decreased strain in the plantar aponeurosis, and a wedge under the medial aspect increased strain (p < 0.05). The test conditions that involved a wedge under the hindfoot but not under the forefoot resulted in strains that were not significantly different from those in the neutral control (p > 0.05). CONCLUSIONS: A wedge under the lateral aspect of the forefoot transmits loads through the lateral support structures of the foot, locking the calcaneocuboid joint and decreasing strain in the plantar aponeurosis. A wedge under the medial aspect of the forefoot transmits loads through the medial support structures of the foot, which produces a truss-like action that increases strain in the plantar aponeurosis.
