Analysis of biomechanical stresses caused by hindfoot joint arthrodesis in the treatment of adult acquired flatfoot deformity: A finite element study

•Biomechanical stress generated by the hindfoot joints arthrodesis was calculated.•Subtalar arthrodesis is the procedure that contributes least to stress reduction.•Talonavicular arthrodesis generates a significant stress reduction in hindfoot.•Calcaneocuboid arthrodesis reduces both the soft tissue and metatarsals stresses.•Triple arthrodesis generates the least tissue stresses in all the evaluated cases. Treatments of adult acquired flatfoot deformity in early stages (I–IIa–IIb) are focused on strengthening tendons, in isolation or combined with osteotomies, but in stage III, rigidity of foot deformity requires more restrictive procedures such as hindfoot joint arthrodesis. Few experimental studies have assessed the biomechanical effects of these treatments, because of the difficulty of measuring these parameters in cadavers. Our objective was to quantify the biomechanical stress caused by both isolated hindfoot arthrodesis and triple arthrodesis on the main tissues that support the plantar arch. An innovative finite element model was used to evaluate some flatfoot scenarios treated with isolated hindfoot arthrodesis and triple arthrodesis. When arthrodeses are done in situ, talonavicular seems a good option, possible superior to subtalar and at least equivalent to triple. Calcaneocuboid arthrodesis reduces significantly both fascia plantar and spring ligament stresses but concentrates higher stresses around the fused joint.