X-Ray CT-Based Evaluation of Dorsal Rotation Angles and Axes of the 1st–5th Tarsometatarsal Joints

The tarsometatarsal (TMT) joints play crucial roles in walking and slow running. Some studies have treated the 1st to 5th TMT joints collectively as a single joint. However, few studies have examined each individual joint within the 1st to 5th TMT joints separately. This study sought to determine the rotation angles and axes of the 1st–5th TMT joints as each metatarsal head was dorsally displaced in vivo. CT imaging was conducted on 11 subjects under six conditions: a basic posture and isolated metatarsal movement postures in which one of the 1st to 5th metatarsals was dorsally displaced with a load of 55 N. The helical axis parameters (rotation angle and rotation axis) of the metatarsal were calculated by transitioning from the basic posture to each isolated metatarsal movement posture. Multiple comparison testing on the dorsal rotation angles showed significant differences between all TMT joints, except between the 1st and 4th TMT joints and between the 1st and 5th TMT joints (p < 0.01). The 2nd TMT joint exhibited a significantly lower dorsal rotation angle than the other TMT joints. By transitioning from the 1st to the 5th TMT joints, the transversal plane rotation axis shifted from lateral-anterior to -posterior, while that of the sagittal plane shifted from anterior- to posterior-inferior. This study provided the rotation angles and axes of the 1st–5th TMT joints in vivo. The data provide a useful reference dataset for selecting diseased feet and developing new foot orthoses.