Subtalar Joint Kinematics in Frontal-Plane Inversion-Eversion Using Weightbearing Cone-Beam CT.

Area of Science:

• Orthopedics
• Biomechanics
• Radiology

Background:

• Subtalar joint kinematics are crucial for foot and ankle function.
• Understanding frontal plane motion (inversion-eversion) is essential for diagnosing and treating foot pathologies.
• 3D weightbearing cone beam computed tomography (CBCT) offers a novel approach to assess joint motion.

Purpose of the Study:

• To quantify the translational and angular range of motion of the subtalar joint in the frontal plane.
• To utilize 3D weightbearing CBCT for kinematic assessment.
• To establish baseline data for normal subtalar joint motion.

Main Methods:

• A cohort of 41 subjects underwent weightbearing CBCT scans.
• Images were acquired under specific inversion (20 degrees) and eversion (10 degrees) stress.
• Interobserver and intraobserver reliability were evaluated using intraclass correlation coefficients.

Main Results:

• Normal subtalar joint motion values were generally small, with greater range in eversion than inversion.
• Translational range of motion differed between facets: anterior (4.9 mm) > middle (1.4 mm).
• Good to excellent reliability was observed for most parameters, though some measures showed poor interobserver agreement.

Conclusions:

• This study provides normative data for subtalar joint inversion-eversion kinematics under weightbearing conditions.
• The defined ranges are based on bony structures of normal subtalar joints.
• Further investigation is recommended to explore the method's utility in diverse patient populations.