Assessment of mechanical strain in the intact plantar fascia

Background: A method of measuring tri-axial plantar fascia strain that is minimally affected by external compressive force has not previously been reported. Objective: The purpose of this study was to assess the use of micro-strain gauges to examine strain in the different axes of the plantar fascia. Method: Two intact limbs from a thawed, fresh-frozen cadaver were dissected, and a combination of five linear and one three-way rosette gauges were attached to the fascia of the foot and ankle. Strain was assessed during two trials, both consisting of an identical controlled, loaded dorsiflexion. Results: An ICC analysis of the results revealed that the majority of gauge placement sites produced reliable measures (ICC > 0.75). Strain mapping of the plantar fascia indicates that the majority of the strain is centrally longitudinal, which provides supportive evidence for finite element model analysis. Conclusion: Although micro-strain gauges do possess the limitation of calibration difficulty, they provide a repeatable measure of fascial strain and may provide benefits in situations that require tri-axial assessment or external compression.