3D-Printed Arch Supports Combined with Toe Spreaders Modulate Phase-Specific Ankle Alignment and Muscle Activity in...

Area of Science:

• Biomechanics
• Orthotics
• Sports Medicine

Background:

• Functional flat foot (FF) is linked to poor lower limb biomechanics, inefficient load transfer, and overuse injuries.
• The combined effects of 3D-printed insoles and toe spreaders on FF biomechanics and neuromuscular control are not well understood.

Purpose of the Study:

• To investigate the immediate effects of 3D-printed insoles (SI), toe spreaders (Toe), and their combination (SI+Toe) on gait, center of force (COF), ankle alignment, and muscle activation in young adults with FF.
• To compare biomechanical and neuromuscular responses between FF individuals and healthy controls.

Main Methods:

• Ten FF individuals and ten controls walked under four conditions: shoe-only, SI, Toe, and SI+Toe.
• Gait parameters were assessed using OptoGait, COF trajectory with F-Scan, ankle angles with Kinovea, and muscle activity via surface EMG.

Main Results:

• FF individuals showed medial COF deviation, increased ankle eversion, and altered muscle activity compared to controls.
• The SI+Toe intervention in FF individuals reduced medial COF deviation, decreased ankle eversion, prolonged the stance phase (foot flat), and shortened the propulsive phase.
• SI+Toe increased semitendinosus and tibialis anterior activity while maintaining reduced gastrocnemius and soleus activity during propulsion.

Conclusions:

• The combination of 3D-printed insoles and toe spreaders led to immediate improvements in foot alignment and muscle activation patterns in individuals with FF.
• Integrating customized orthotics with toe spreader elements presents a viable non-invasive strategy for enhancing lower limb biomechanics and potentially reducing injury risk in clinical settings.