The influence of flatfoot deformity on the gliding resistance of tendons about the ankle

Background: Various tendinopathies occur about the ankle, but there are few publications investigating their etiology or pathoanatomy. The purpose of this investigation was to determine the gliding resistance of the tendons about the posteromedial ankle: the posterior tibial (PT), flexor digitorum longus (FDL), and flexor hallucis longus (FHL) tendons. Materials and Methods: The gliding abilities of the posterior tibial, flexor digitorum longus, and flexor hallucis longus tendons at the ankle-hindfoot level were compared, in terms of gliding resistance, with use of a system that was developed in this laboratory. Six cadaveric specimens were used and tested in a dorsiflexed position, then in simulated flatfoot in a dorsiflexed position. Results: The gliding resistance was found to be significantly greater in the simulated flatfoot in dorsiflexion compared to the dorsiflexed position with an intact arch for the PT, FDL, and FHL tendons. The gliding resistance was significantly higher in the PT tendon than FDL or FHL tendons in the flatfoot/dorsiflexion condition. There was no significant difference between the FDL and FHL tendons in resistance in either condition. Conclusion: We concluded that the gliding ability of the PT tendon was inferior to that of the FDL and FHL tendons in a simulated flatfoot model. Clinical Relevance: The findings of the present study are consistent with the clinical observations that tendinitis and rupture of the PT tendon commonly occurs at the malleolar level, whereas FDL and FHL ruptures do not. A pre-existing flexible flatfoot deformity may be associated with PT tendon dysfunction in the adult due to poor gliding ability of the PT tendon.