A device for characterising the mechanical properties of the plantar soft tissue of the foot

Abstract

The plantar soft tissue is a highly functional viscoelastic structure involved in transferring load to the human body during walking. A Soft Tissue Response Imaging Device was developed to apply a vertical compression to the plantar soft tissue whilst measuring the mechanical response via a combined load cell and ultrasound imaging arrangement. Accuracy of motion compared to input profiles; validation of the response measured for standard materials in compression; variability of force and displacement measures for consecutive compressive cycles; and implementation in vivo with five healthy participants. Static displacement displayed average error of 0.04 mm (range of 15 mm), and static load displayed average error of 0.15 N (range of 250 N). Validation tests showed acceptable agreement compared to a Houndsfield tensometer for both displacement (CMC > 0.99 RMSE > 0.18 mm) and load (CMC > 0.95 RMSE < 4.86 N). Device motion was highly repeatable for bench-top tests (ICC = 0.99) and participant trials (CMC = 1.00). Soft tissue response was found repeatable for intra (CMC > 0.98) and inter trials (CMC > 0.70). The device has been shown to be capable of implementing complex loading patterns similar to gait, and of capturing the compressive response of the plantar soft tissue for a range of loading conditions in vivo.

Micropipette force sensors for in vivo force measurements on single cells and multicellular microorganisms

“…the flexible part of the micropipette) and elastic property of the glass, MFS spans about 8 orders of magnitude in the force sensitivity (tens of pN to several mN) and about 3 orders of magnitude in the size of the object (µm to several mm). The MFS technique thus fills an intriguing mesoscopic gap that manifests itself between conventional microscopic force measurement techniques such as AFM, optical tweezers and magnetic tweezers that can be used to study single molecules and cells [15,16,17,18], and macroscopic force probes such as dynamometers and load cells that are used to study bulk properties of tissue [19,20], for example. The micro-to mesoscopic regime covered by the MFS technique and its adaptability to the experimental system allows for versatile studies of micro-and millimeter-sized soft and biological samples.…”

On the Relationship between Foot Pressure Distribution and Sole Hardness during Long-Time Standing

“…Through the spine and waist and then the legs, the body weight is divided into three pressure forces in each foot -one force is transferred to the heel, one to the forefoot and one to the buffer zone between the arch and the ground. Figure 1 shows the foot area map [5]. In the weight transfer process, foot pressure distribution is affected by various factors.…”

The potential of ultrasonography in the evaluation of foot orthotics therapy

“…ulceration, heel pain or plantar fasciitis) [27][28][29]. US indentation methods were used for evaluating the mechanical properties of the plantar soft tissue (thickness, stiffness), providing useful information regarding mechanical behavior under vertical loading and an indication for the selection of the properties of the orthotic devices materials [30][31][32]. The influence of tissue's properties (as bulk modulus and density) on the speed of the axial transmission of ultrasound waves [33,34] was used for the study of the human Achilles' tendon tension as an effect of wearing footwear and orthotic heel lifts [34,35].…”