Isolated medial column stabilization surgery does not benefit adult acquired flatfoot stage IIa nor IIb by three-dimensional finite element biomechanical analysis.

The surgical treatment for stage II adult acquired flat foot deformity (AAFD) remains controversial. Biomechanical effects of medial column stabilization remain unclear. No study has biomechanically assessed the effect of medial column arthrodesis on the whole foot. Our study aimed to mechanically analyze the advantages and disadvantages of this. Stage IIa and IIb AAFD three-dimensional finite element models were established. The application of Geomagic software, Solidwork software, and Abaqus software was used to simulate a medial column stabilization operation (navicular-cuneiform joint fusion, metatarsal-cuneiform joint fusion, or both). The maximum pressure on plantar soft tissue, medial column bone, and medial ligaments was compared before and after simulated single-foot weight loading. Several data were measured to carry out a comprehensive comparison. The maximum plantar stress was located under the first metatarsal head after the simulated medial column stabilization operation. It increased significantly after medial column stabilization in a stage IIa flatfoot model, but did not change significantly after medial column stabilization in stage IIb model. Therefore, after medial column fusion, the stress of the corresponding joint was reduced, but it was increased in the adjacent joints of the medial column. The stresses on medial ligaments and plantar fascia were also not alleviated after medial column fusion. Our results showed isolated medial column stabilization surgery cannot help patients with stage IIa nor IIb flatfoot from the biomechanical point of view, and such stabilization increases stress on the sole, the joints around the fusion sites, medial soft tissue, and ligaments. It can only be used as a combined surgery to stabilize joints with excessive motion and correct the deformity of supination of the forefoot.