A Vivo Study Of Hindfoot Three-dimensional Kinetics In Stage Ⅱ Adult Acquired Flatfoot Deformity

Objective:To study the rotation and translation of talocalcaneal joint, talonavicular joint and calcanocuboid joint in the hindfoot of stage II adult acquired f latfoot deformity and to evaluate the correlation between the medial arch angle and three-dimensional motion of hindfoot joint. In order to provide a new method for the selection of surgical procedures and the evaluation of the outcomes clinically.Methods:Firstly, CT scans of 15 healthy volunteers (20 feet) and 15 stage Ⅱ adult acquired flatfoot deformity (20 feet) were taken in various foot positions such as maximal dorsiflexion and plantarflexion, maximal inversion and eversion, maximal adduction and abduction. Secondly, CT scans of 15 healthy volunteers (20 feet)and 15 stage Ⅱ adult acquired flatfoot deformity(20 feet) were taken in non-weightbearing condition followed by full-body weightbearing condition. All the images of the hindfoot bones were imported into the Mimics and Geomagic software and reconstructed into three-dimensional models. The twice registration method in three planes was used to calculate the position of the talus relative to the calcaneus in the talocalcaneal joint, the navicular relative to the talus in talonavicular joint, and the cuboid relative to the calcaneus in the calcanocuboid joint. The obtained data was analyzed with t-test, one-way analysis of variance and Pearson linear correlation.Results:Three-dimensional position changes in talocalcaneal joint, talonavicular joint and calcanocuboid joint of both healthy foot and adult acquired flatfoot deformity during the various foot and ankle positions as well as full-body-weightbearing condition. From maximal plantarflexion to maximal dorsiflexion, the calcaneus position difference relative to the talus in the talocalcaneal joint was more dorsiflexed (p=0.001), more anterior (p=0.004) and more distal (p=0.04) in stage Ⅱ adult acquired flatfoot deformity compared to that in healthy foot. The navicular position difference relative to the talus in the talonavicular joint was more everted (p=0.02), more lateral (p=0.02), more anterior (p=0.01) and more proximal(p=0.004). The cuboid position difference relative to the calcaneus in the calcanocuboid joint didn’t change significantly in rotation and translation(all p>0.05). From maximal inversion to maximal eversion condition, the calcaneus position difference relative to the talus in the talocalcaneal joint was more everted (p=0.046), more abducted(p=0.01), more lateral(p=0.04) in stage Ⅱ adult acquired flatfoot deformity compared to that in healthy foot. The navicular position difference relative to the talus in the talonavicular joint was more everted(p=0.04), more abducted(p=0.01), more lateral(p=0.04), more proximal(p=0.02). The cuboid position difference relative to the calcaneus in the calcanocuboid joint didn’t change significantly in rotation and translation(all p>0.05). From maximal adduction to maximal abduction, the calcaneus position difference relative to the talus in the talocalcaneal joint was more abducted(p=0.02), more lateral (p=0.04), more anterior (p=0.005) in stage II adult acquired flatfoot deformity compared to that in healthy foot. The navicular position difference relative to the talus in the talonavicular joint was more everted(p=0.03), more abducted (p=0.04), more lateral (p=0.003). The cuboid position difference relative to the calcaneus in the calcanocuboid joint didn’t change significantly in rotation and translation (all p>0.05).From non-weightbearing condition to full-body-weightbearing condition, the calcaneus position difference relative to the talus in the talocalcaneal joint was more dorsiflexed(p=0.002), more everted (p=O.001), more posterior(p=0.001) and more proximal (p=0.002) in stage II adult acquired flatfoot deformity compared to that in healthy foot. The navicular position difference relative to the talus in the talonavicular joint was more dorsiflexed (p=0.001), more everted(p=0.001), more lateral (p=0.001), more anterior (p=0.001) and more proximal (p=0.001). The cuboid position difference relative to the calcaneus in the calcanocuboid joint didn’t change significantly in rotation and translation(all p>0.05). During weightbearing condition, the eversion of the talocalcaneal joint (r=0.5099, p=0.0413), the proximal translation of the calcaneus relative to the talus (r=0.5711, p=0.0085) and the dorsiflexion of talonavicular joint (r=0.6999, p=0.0006) have a significant correlation with the medial arch angle change in stage Ⅱ adult acquired flatfoot deformity.Conclusion:Both the motion range of the talocalcaneal joint and the talonavicular joint were increased during various foot and ankle position and the joint instability occurred in the hindfoot in patients with stage Ⅱ adult acquired flatfoot deformity. From non-weightbearing condition to full-body-weightbearing condtion, the calcaneus position difference relative to the talus in the talocalcaneal joint was more dorsiflexed, more everted, more posterior and more proximal in stage Ⅱ adult acquired flatfoot deformity compared to that in healthy foot. The navicular position difference relative to the talus in the talonavicular joint was more dorsiflexed, more everted, more lateral, more anterior and more proximal. The cuboid position difference relative to the calcaneus in the calcanocuboid joint didn’t change significantly in rotation and translation. During weightbearing condition, the eversion of the talocalcaneal joint, the proximal translation of the calcaneus relative to the talus and the dorsiflexion of talonavicular joint have a significant positive correlation with the medial arch angle change.