In vitro determination of midfoot motion.

Midfoot motion was determined using an in vitro model. Ten fresh-frozen below-the-knee amputation specimens were instrumented by inserting reference pins into each of the bones of the hindfoot, midfoot and metatarsals. Dorsiflexion-planatar flexion and supination-pronation were simulated and the reference pin location in three dimensional space was determined. Comparing the location of the reference pins at each simulated position, motion was determined. Motion occurring through each articulation (dorsiflexion-plantar flexion/supination-pronation) in degrees was: talonavicular (7.0/17.7), calcaneocuboid (2.3/7.3), naviculo-medial cuneiform (5.0/7.3), naviculo-middle cuneiform (5.2/3.5), naviculo-lateral cuneiform (2.6/2.1), medial cuneiform-first metatarsal (3.5/1.5), middle cuneiform-second metatarsal (0.6/1.2), lateral cuneiform-third metatarsal (1.6/2.6), cuboid-fourth metatarsal (9.6/11.1), and cuboid-fifth metatarsal (10.2/9.0).