Posterior tibial tendon force requirement in early heel rise after calcaneal osteotomies.

Posterior tibial tendon insufficiency leads to decreased inversion strength. The purpose of this study was to measure the posterior tibial tendon force required to achieve early heel rise, defined as 7 degrees of calcaneal plantar flexion and 5 degrees of calcaneal inversion, in the intact foot and compare it to the requirements following medial displacement calcaneal osteotomy and following posterior distraction osteotomy. Thirteen cadaver specimens were loaded in a custom testing apparatus. The force required of the posterior tibial tendon to achieve early heel rise decreased from 399 +/- 50 N in the intact foot to 328 +/- 78 N (p < 0.001) after medial displacement osteotomy and 206 +/- 122 N (p < 0.001) after posterior distraction. Therefore, both the medial displacement and the posterior distraction osteotomies reduced the inversion demand at the posterior tibial tendon, with the distraction osteotomy being more effective in this reduction. Interestingly, these osteotomies also reduced the Achilles force required to achieve the heel rise position.