Functional Fusion Angle for Thumb Interphalangeal Joint Arthrodesis.

Area of Science:

• Orthopedic surgery
• Hand surgery
• Biomechanics

Background:

• Thumb interphalangeal (IP) joint arthrodesis is commonly performed at 0°–30° flexion.
• Optimal IP joint positioning is crucial for effective pinch and grip in daily activities.

Purpose of the Study:

• To evaluate preferred thumb IP joint angles for diverse daily living tasks.
• To determine a more functional fusion angle for thumb IP joint arthrodesis.

Main Methods:

• Twenty-eight volunteers performed standardized power, precision, pinch, and grip tasks with bilateral thumb orthotics at 0°, 15°, 30°, and 45°.
• Participants rated task ease and overall satisfaction using a 10-point Visual Analogue Scale (VAS).
• Statistical analysis used Wilcoxon signed rank tests (P < .05).

Main Results:

• Power tasks: 0° (non-dominant), 0°–30° (dominant). Precision tasks: 15° (both hands). Grip strength: 15° (non-dominant), 0° (dominant).
• Pinch strength was optimal between 0°–30° (non-dominant) and 15°–30° (dominant).
• VAS ratings indicated 15° and 30° were most satisfactory, closely mimicking baseline function.

Conclusions:

• A thumb IP joint fusion angle of 15°–30° is recommended for optimal function across various daily activities.
• This angle range provides a balance for both power and precision hand tasks.
• Findings suggest a revised standard for thumb IP joint arthrodesis positioning.