Assessment of subtalar joint neutral position: a cadaveric study

Area of Science:

• Biomechanics
• Orthopedics
• Anatomy

Background:

• The subtalar joint (STJ) neutral position is critical for fabricating custom orthotics.
• Current methods for determining STJ neutral position lack proven accuracy and reproducibility.
• This study aimed to define the STJ neutral position in cadaveric feet.

Purpose of the Study:

• To investigate and define the subtalar joint (STJ) neutral position in normal feet using cadavers.
• To challenge the traditional clinical understanding of STJ neutral position.
• To provide a more accurate reference for orthotic fabrication.

Main Methods:

• Utilized twelve fresh-frozen human lower leg specimens.
• Inserted pressure-sensitive films into the anterior and posterior STJ articulations.
• Determined contact areas under axial load (600 N) and various foot positions using digitized film analysis.

Main Results:

• The maximum STJ contact area in the traditional neutral position was 2.79 cm².
• Maximum contact areas were achieved at 10° abduction (3.00 cm²), 20° dorsiflexion (3.61 cm²), and 10° eversion (3.14 cm²).
• These positions significantly differed from the traditional neutral ankle-foot position (P < 0.05).

Conclusions:

• The subtalar joint (STJ) neutral position does not align with the traditional clinical ankle-foot neutral position.
• The most accurate STJ neutral position was determined to be 10° abduction, 20° dorsiflexion, and 10° eversion.
• These findings necessitate a re-evaluation of current methods for STJ assessment in orthotic practice.