A Method for Weightbearing Assessment of Plantar Fascia Thickness and Stiffness

The plantar fascia of the foot is complex in both its structure and function. Previous research using ultrasound-based techniques has focused on nonweightbearing assessment of plantar fascia thickness (PFT) and plantar fascia stiffness (PFS). However, weightbearing assessment (closed chain) has not previously been performed in a way to demonstrate the response of the plantar fascia to load. This study aimed to develop a protocol that enables precise and consistent measurement of the PFT and PFS while bearing weight in a fixed calcaneal stance position.

An ultrasound probe capable of shear wave elastography was integrated into a bespoke three-dimensional printed platform incorporating a window to allow positioning of the ultrasound probe. This allowed a closed-chain assessment of the plantar fascia in which a standardized protocol was developed for measurement of the PFT and PFS. The images produced were composed of clips, which were then subdivided into multiple frames.

A total of 13 participants (26 feet) had PFT and PFS assessed using the protocol. The results showed a low coefficient of variation (CV) in frame analysis for PFT (CV, 0) and PFS (CV, 0.01). One-clip analysis also demonstrated a low CV for PFT (CV, 0.02) and PFS (CV, 0.01). In addition, a cluster analysis indicated two distinct groups that demonstrated a strong correlation between PFT and PFS (group 1 and group 2 correlation coefficients, 0.83 and 0.98, respectively).

The protocol reported in this study was shown to be a valid and reliable method for assessing PFT and PFS in a weightbearing position, which has many clinical and research implications.