Talonavicular joint fixation: a biomechanical comparison of locking compression plates and lag screws

Fusion of the talonavicular (TN) joint is an effective treatment for hindfoot pain and deformity. Nonunion in hindfoot fusion procedures is most common in the TN joint. The purpose of this study was to evaluate and compare the mechanical stability of 2 different forms of fixation for isolated fusion of the TN joint.

13 fresh-frozen cadaver foot and ankles were procured and mounted vertically in a robotic biomechanical testing platform and tested before and after operative fixation; 7 specimens received 2 retrograde lag screws (2S), and 6 specimens received a locked compression plate with 1 retrograde lag screw (PS). A constant Achilles tendon load was initially applied followed by internal or external rotation (ER) of the foot and axial compression through the tibia. The relative motion of the talus and navicular bones was tracked using 3-dimensional optoelectric targets. Motion data were recorded in the traditional anatomical reference frame and then transformed into the TN joint frame.

In the TN joint frame, relative to the intact (preoperative) state, the plate fixation group PS showed a significant reduction in separation along the long axis of the talus in 3 out of the 4 loading scenarios (P values = .007, .02, and .05). The PS construct also significantly restricted the flexion-extension motion at the joint compared with the 2S construct, during the ER tests (P values = .002 and .001).

In our simulated weight-bearing model, a dorsal locked compression plate with 1 retrograde screw was more effective at limiting the 3D motion across the TN joint compared with the traditional construct of 2 retrograde screws.