STABILITY OF THE ARCH OF THE FOOT

We defined the relative contributions of six ligaments in stabilizing the arch of the foot: plantar aponeurosis, long-short plantar ligament s, plantar calcaneonavicular ligament (spring ligament), medial taloca lcaneal ligament, talocalcaneal interosseous ligament, and tibionavicu lar portion of the deltoid ligament. Nineteen fresh-frozen human foot specimens were used. A load of 445 N was applied axially to simulate s tanding-at-ease posture. Three-dimensional positions of tarsal bones b efore and after ligament sectioning were determined with the use of a magnetic tracking device. The motions were presented in the form of sc rew axis displacements, quantitating rotation, and axis of rotation or ientation. After sectioning one structure, the arch did not collapse o n any specimen and there was no obvious change by visual inspection. T here were, however, measurable changes in tarsal bone position. Metata rsal-to-talus total rotation difference was greatest with spring ligam ent and deltoid ligament sectioning, with an average of 2.1 degrees +/ - 1.7 degrees and 2.0 degrees +/- 0.2 degrees difference, respectively . Calcaneus-to-talus rotation difference was greatest with talocalcane al interosseous ligament sectioning, with an average of 1.7 degrees +/ - 1.5 degrees. The spring ligament, deltoid ligament, and talocalcanea l interosseous ligament were most important for arch stability.