Hoop Stress Elicited at Medial Tibial Crural Fascia Attachment During Passive Dorsiflexion: A Proof-of-Concept Study for Medial Tibial Stress Syndrome Causation.

Background: Identification of a specific causal mechanism for medial tibial stress syndrome has been elusive, although there is a consensus that it may be caused by traction on the tibial periosteum elicited by soft tissues. The crural fascia (CF) attaches directly to the tibia throughout the length of the leg, encircling it in a grossly cylindrical fashion, and the leg may thus be viewed as a type of fluid-filled cylinder, subject to both longitudinal and hoop stresses. Prior researchers have not considered the possibility that strain on the medial tibia could be produced by the CF during gait and passive stretching, secondary to fluid pressure increases in the fascial compartments of the leg. The purpose of the present research was to verify the existence of measurable hoop strain in the CF of a cadaver donor at the medial tibial border during a heel cord stretch.

Methods: Strain gauges were affixed to the CF of a cadaver donor to measure hoop and longitudinal strain during repeated heel cord stretches applied manually, and with measurements taken from each strain gauge separately.

Results: Passive heel cord stretches produced 182.96 × 10-3 mV/V and 138.00 × 10-3 mV/V hoop strain in the CF, in the distal third and middle third of the leg, respectively. A maximum longitudinal strain in the CF of the superficial posterior compartment of 75.00 × 10-3 mV/V was also produced.

Conclusions: A heel cord stretch applied to a cadaver donor can elicit a measurable hoop strain within the CF attachment to the medial border of the tibia, in a grossly 2-to-1 manner consistent with the ratio of hoop to longitudinal strain seen with gases and liquids in a closed cylinder. Further research is indicated to replicate these results in multiple subjects, with variation in cadaver fixative and experimental set-up.