Kinematics of primate midfoot flexibility

Area of Science:

• Primate locomotion
• Paleoanthropology
• Biomechanics

Background:

• The "midtarsal break" describes reduced midfoot flexibility in primates.
• Human evolution is often assumed to have reduced midfoot flexibility.
• Primate foot joint kinematics are crucial for understanding locomotion and evolution.

Purpose of the Study:

• To assess primate intrinsic foot joint kinematics using bone pin rigid cluster tracking.
• To challenge the assumption of reduced midfoot flexibility in human evolution.
• To compare midfoot flexibility and joint function across humans, chimpanzees, baboons, and macaques.

Main Methods:

• Bone pin rigid cluster tracking was employed on cadaveric human, chimpanzee, baboon, and macaque feet.
• Plantarflexion-dorsiflexion movement cycles were monitored to analyze joint kinematics.
• Flexion-extension patterns and rotational axes of the talonavicular, calcaneocuboid, and lateral cubometatarsal joints were resolved.

Main Results:

• Midfoot flexibility is primarily concentrated in the talonavicular and cubometatarsal joints.
• Rotational magnitudes at these joints show similarities between humans and chimpanzees.
• While the lateral cubometatarsal joint shows similarity across evaluated primates, the talonavicular joint exhibits greater rotation in hominines compared to monkeys.

Conclusions:

• The human foot possesses the capability for a midtarsal break.
• Functional similarities in midfoot kinematics exist between humans and chimpanzees.
• The kinematic capabilities of the human foot may not be as unique as previously believed, with potential for similar locking mechanisms observed in chimpanzees.