Contributions of active and passive toe flexion to forefoot loading

Area of Science:

• Biomechanics
• Human Locomotion
• Anatomy

Background:

• Toe flexion during terminal stance involves both active (muscles) and passive (plantar fascia) components.
• Understanding the interplay between these components is key to analyzing foot function during gait.

Purpose of the Study:

• To determine the relative contributions of toe flexor muscles and the plantar fascia to force distribution in the foot during terminal stance.
• To investigate how the absence of these structures affects plantar pressure and force transmission.

Main Methods:

• Utilized a dynamic gait simulator with thirteen cadaver feet to replicate human locomotion kinematics and kinetics.
• Measured plantar pressure distribution during terminal stance under three conditions: intact plantar fascia with normal muscle activity, intact plantar fascia without toe flexor activity, and after plantar fasciotomy with normal muscle activity.

Main Results:

• Absence of toe flexor muscles or plantar fasciotomy led to reduced toe contact area and a shift in force towards the metatarsal heads.
• Plantar fasciotomy resulted in lateral and posterior shifts in pressure distribution under the metatarsal heads.
• The plantar fascia facilitates efficient force transmission through the "high gear" axis during locomotion.

Conclusions:

• The plantar fascia plays a critical role in enabling toes to bear significant loads and generate plantar-directed force during push-off.
• This passive structure is essential for optimal force sharing and efficient locomotion, more so than active toe flexion alone.