Closed kinetic chain tarsal mechanics of subtalar joint arthroereisis.

The weightbearing biomechanics of the tarsus with and without subtalar joint arthroereisis was investigated in 11 fresh frozen cadaver specimens using a three-dimensional (3-D) radiowave tracking system. Specimens, consisting of the distal half of the tibia and fibula and the intact ankle and foot, were mounted on a nonmetallic loading frame test system that allowed positioning of the foot to simulate midstance position of gait. The tibia was axially loaded to 756 N (one bodyweight) with 15% of the total load diverted through the fibula. Receiving transducers were attached to the talus, navicular, calcaneus, and cuboid bones. Tarsal movements were monitored as the specimen was loaded with and without subtalar joint arthroereisis. Three-dimensional data sets of osseous positions and orientations were collected and analyzed. Significant rotational differences were detected with and without subtalar joint arthroereisis for all four tarsal bones (p < or = 0.05). Tarsal translational position changes were small and not statistically significant.