Lateral Column Overload in Modified Double vs Triple Arthrodesis: A Biomechanical Study

Abstract

Category: Hindfoot; Basic Sciences/Biologics Introduction/Purpose: There are few comparative studies investigating differences between the modified double and triple arthrodesis of the hindfoot. Previous studies have suggested that stiffening the lateral column of the hindfoot can increase lateral plantar pressures, potentially precipitating lateral column pain. We sought to characterize the difference in forefoot plantar pressures between the native state, after talonavicular (TN)/subtalar (ST) arthrodesis and triple arthrodesis. Methods: Ten fresh-frozen cadaver legs were tested in 4 positions: neutral, dorsiflexion, inversion and eversion. Testing was done in a native state, after TN/ST arthrodesis then after triple arthrodesis for all 4 positions. Forefoot plantar pressures were recorded. Results: Peak pressures increased from the native state laterally underneath the 5th metatarsal (MT) head after TN/ST arthrodesis and triple arthrodesis respectively by 247% and 164% and fell medially underneath the 1st MT head to 38% and 41% in axially loaded legs at neutral (p < 0.025) without a difference between arthrodesis groups. Similarly, 5th MT head pressures were significantly increased from the native state after TN/ST and triple arthrodesis in the legs mounted in eversion by 129% and 109% respectively (p < 0.025), without differences between the two arthrodesis groups. Conclusion: In our cadaveric model of native, non-deformed legs, both a modified double (TN/ST) and triple arthrodesis led to increased lateral forefoot plantar pressures compared to the native state without a difference between the arthrodesis groups.