Midtarsal joint locking: new perspectives on an old paradigm.

Area of Science:

• Orthopaedic biomechanics
• Human locomotion analysis
• Foot and ankle anatomy

Background:

• The midtarsal joint locking mechanism is hypothesized to create a rigid lever during the push-off phase of gait.
• This locking is thought to involve specific coupled rotations of the calcaneocuboid and talonavicular joints.

Purpose of the Study:

• To investigate the existence and nature of a midtarsal joint locking mechanism during normal gait using cadaveric simulations.
• To examine the rotational behavior of the midtarsal joints (talonavicular and calcaneocuboid) and associated joints (cubonavicular and talocalcaneal) during the stance phase.

Main Methods:

• Utilized cadaveric specimens to simulate normal gait.
• Recorded three-dimensional kinematics of the talus, calcaneus, cuboid, and navicular bones.
• Analyzed finite helical axis parameters and joint angles, alongside muscle and ground reaction forces.

Main Results:

• Contrary to hypothesis, midtarsal joints remained compliant throughout stance, including during push-off.
• Observed eversion and changes in helical axis orientation during weight acceptance, followed by inversion and dorsiflexion late in stance.
• Cubonavicular and talocalcaneal joints exhibited complementary, non-coupled rotational behavior.

Conclusions:

• The concept of midtarsal joint locking creating a rigid lever for push-off is challenged by these findings.
• Joint rotations persist after weight acceptance, indicating continued compliance rather than a rigid locked state during the latter stance phase.