Effect of different fusion types on kinematics of midfoot lateral column: a comparative biomechanical study

This study aimed to compare the biomechanical outcomes of the isolated 4^th or 5^th tarsometatarsal (TMT) joint arthrodesis with the whole lateral TMT joints arthrodesis.

Ten cadaveric lower legs underwent isolated 4^th TMT joint arthrodesis, 5^th TMT joint arthrodesis, and whole lateral TMT joints arthrodesis in sequence. Texson F-scan and K-scanTM joint sensor were used to test the medial and lateral plantar pressure and the pressure of calcaneocuboid joint.

Compared with the intact foot, the lateral forefoot pressure increased significantly (P<0.05) after 4^th TMT joint fusion. The medial forefoot pressure was significantly lower in the 5^th TMT joint fusion than that in the intact foot (P<0.05) and the 4^th TMT joint fusion (P<0.05), but higher than that in the whole lateral TMT joints fusion (P<0.05). On the contrary, the lateral forefoot pressure was significantly higher in the 5^th TMT joint fusion than that in the intact foot and the 4^th TMT joint fusion, but lower than that in the whole lateral TMT joints fusion (P<0.05). The medial forefoot pressure was the lowest (P<0.05) and lateral forefoot pressure was the highest (P<0.05) in the whole lateral TMT joints fusion. The calcaneocuboid joint pressure increased respectively with the intact foot being the lowest, followed by the isolated 4^th TMT joint arthrodesis, the isolated 5^th TMT joint arthrodesis, and the whole lateral TMT joints arthrodesis (P<0.05).

The isolated 4^th or 5^th TMT joint arthrodesis has less impact on the pressure of forefoot and adjacent joints than the whole lateral TMT joints arthrodesis. The isolated 4^th TMT joint arthrodesis has the lowest influence on the pressure of forefoot and adjacent joints.