Gliding resistance of the posterior tibial tendon

Background: Abnormal gliding of the posterior tibial tendon may lead to mechanical trauma, degeneration, and eventually posterior tibial tendon dysfunction. Our study analyzed the gliding resistance of the posterior tibial tendon in intact feet and in feet with simulated flatfoot deformity. Methods: An experimental system was developed that allowed direct measurement of gliding resistance at the tendon-sheath interface. Seven normal fresh-frozen cadaver foot specimens were studied, and gliding resistance between the posterior tibial tendon and sheath was measured. The effects of ankle and hind-foot position and the effect of flatfoot deformity on gliding resistance were analyzed. Gliding resistance was measured for 4.9 N applied load to the tendon. Results: Mean gliding resistance for the neutral position was 77 ± 13.1 (×10 ^-2 N). Compared to neutral position, dorsiflexion increased gliding resistance and averaged 130 ± 38.9 (×10^-2 N), and plantarflexion decreased gliding resistance and averaged 35 ± 12.6 (×10^-2 N). Flatfoot deformity increased gliding resistance compared to normal feet, averaging 104 ± 17.0 (×10^-2N) for neutral, 205 ± 55.0 (×10^-2 N) for dorsiflexion, and 58 ± 21.3 (×10^-2N) for plantarflexion. Conclusions: The findings indicate that patients with a preexisting flatfoot deformity may be predisposed to develop posterior tibial tendon dysfunction because of increased gliding resistance and trauma to the tendon surface.