When fabricating a dynamic MCP flexion splint, what is the correct angle of pull for a finger loop?

• A. 30°
• B. 60°
• C. 90°
• D. 100°

Answer: (C)

The key idea is that the effectiveness of a dynamic MCP flexion splint depends on the direction of the pull. To flex the MCP joint efficiently, the line of pull should be a right angle to the finger (a perpendicular pull). When the force is perpendicular to the finger, the moment arm about the MCP axis is maximized, producing the strongest flexion moment for a given tension. This orientation centralizes the assist at the MCP and helps avoid unwanted movement at the PIP or DIP joints, making the splint more effective and predictable.

In practice, you route the finger loop so the cord exits at a right angle to the finger, ensuring the pull aligns perpendicularly with the finger’s long axis. If the angle were less than a right angle, the moment arm would be shorter and the flexion torque weaker; angles greater than a right angle reduce control and can introduce unintended forces.