Biomechanical Analysis of the Change of the Metatarsophalangeal Joint's Center of Rotation After Weil and Triple Weil Osteotomies: A Comparative Cadaveric Study.

Background The aim of the present biomechanical study on cadavers was to determine both the center of rotation of the metatarsophalangeal joints and the position of the tendons of the interosseous muscles after the Weil and triple Weil osteotomies, and to compare these parameters in order to clarify the pathogenesis of dorsal stiffness and floating toe. Materials and methods Seven fresh-frozen cadaveric feet were utilized. After completing the preparation of both the plantar and the dorsal surface, we performed the dissection of the entire second, third and fourth rays, and each ray was fixed to a wooden wall mounted on a movable frame. The biomechanical analysis was based on an equilibrium system made of pulleys, threads, and variable weights. Geometrical analysis of both osteotomies and fluoroscopy was used to determine the initial and final metatarsophalangeal joint's center of rotation, as well as the change of interosseous muscles position. Results On comparing the results of the findings, we noticed that after Weil osteotomy, the metatarsophalangeal joint's center of rotation was proximally and plantarly displaced by 3.5 mm compared to the control group, and by 3.7 mm in comparison to the triple Weil osteotomy group. In the latter, the center of rotation was displaced by 0.817 mm compared to the control group. Furthermore, after the Weil osteotomy, the position of the interossei tendon was above the metatarsal longitudinal axis. Conclusion In cases where a metatarsal shortening of 5 mm or greater is desired, the Weil osteotomy causes a statistically significant plantar displacement of the metatarsophalangeal joint's center of rotation, compared to cases where triple Weil osteotomy is performed.