Weightbearing CT Analysis of the Transverse Tarsal Joint During Eversion and Inversion

Area of Science:

• Orthopedics
• Biomechanics
• Medical Imaging

Background:

• The transverse tarsal joint (TTJt) is crucial for foot function, but its movement is not fully understood.
• Previous studies often used cadavers or nonphysiologic conditions, limiting real-world applicability.
• Weightbearing computed tomography (WBCT) offers a potential method for studying TTJt dynamics in more natural positions.

Purpose of the Study:

• To investigate the three-dimensional motion of the transverse tarsal joint (TTJt) under simulated weightbearing conditions.
• To characterize normal TTJt kinematics in both hindfoot valgus and varus using WBCT.
• To provide a foundation for understanding hindfoot pathologies and their management.

Main Methods:

• Five healthy volunteers underwent bilateral WBCT scans with hindfeet positioned in 20° valgus and 20° varus.
• Individual foot bones (talus, calcaneus, cuboid, navicular) were segmented for detailed analysis.
• Joint surface orientations were used to calculate interosseous angles and distances in different hindfoot alignments.

Main Results:

• Hindfoot inversion from valgus to varus caused a 17.1° rotation between the talus and calcaneus in the coronal plane.
• The distance between talar and calcaneal centers decreased by 7.1 mm.
• The navicular rotated 25.4° into varus relative to the talus, while the cuboid translated medially 3.9 mm relative to the calcaneus.

Conclusions:

• The study demonstrates a complex interplay of four bones within the TTJt during hindfoot motion.
• Findings suggest that ligamentous and capsular tightening, rather than solely parallel or divergent joint axes, contribute to the TTJt locking mechanism.
• This research enhances understanding of normal TTJt function, aiding clinical diagnosis and treatment of hindfoot issues.