Three-dimensional analysis of flatfoot deformity: cadaver study.

Eleven fresh-frozen cadaver foot specimens were tested to define changes in tarsal alignment associated with flatfoot, or pes planus, a common clinical problem. The three-dimensional position of four bones (talus, calcaneus, navicular, and first metatarsal) relative to the fixed tibia was determined with a magnetic tracking system in the intact foot and flatfoot conditions. In the flatfoot, the average metatarsal-to-talar position difference was 11.7 degrees +/-4.4 degrees in abduction (P < 0.0001), 10.4 degrees +/-3.6 degrees in dorsiflexion (P < 0.0001), and 10.9 degrees +/-6.0 degrees in eversion (P < 0.0001) compared with the intact foot. The average calcaneal-to-talar position difference was 2.2 degrees +/-2.6 degrees in abduction (P=0.0171) and 2.7 degrees+/-2.0 degrees in eversion (P=0.0012) compared with the intact foot. The average navicular-to-talar position difference was 13.6 degrees +/-5.0 degrees in abduction (P < 0.0001), 10.5 degrees +/-6.6 degrees in dorsiflexion (P=0.0004), and 8.1 degrees +/-3.8 degrees in eversion (P < 0.0001) compared with normal. The average talar-to-tibial position difference was -8.2 degrees +/-3.2 degrees in dorsiflexion (P < 0.001) compared with the intact foot. The average arch height difference was 6.0+/-2.7 mm (P < 0.0001) less than the normal condition. The deformity associated with flatfoot is complex and occurs in multiple joints and in all three planes. An understanding of the normal and pathologic (flatfoot) conditions is necessary to surgically restore appropriate alignment and function in hindfoot reconstruction operations.