Acceptable Angulation for PIP Joint Arthrodesis
For optimal hand function, proximal interphalangeal (PIP) joint arthrodesis should be performed at 40° of flexion for index finger, 40-45° for middle and ring fingers, and 50-55° for little finger. This positioning provides the best balance between grip strength and functional capabilities while minimizing complications 1, 2.
Optimal Arthrodesis Angles by Digit
The recommended angles for PIP joint arthrodesis vary by finger:
- Index finger: 40° of flexion
- Middle finger: 40-45° of flexion
- Ring finger: 40-45° of flexion
- Little finger: 50-55° of flexion
Evidence-Based Rationale
Research demonstrates that intermediate angles of flexion provide the best functional outcomes:
- For the index finger, 40° was significantly faster than 25° for lifting large, light objects and faster than 55° for writing tasks 1
- For the little finger, 55° was significantly faster than 30° or 70° for multiple functional tasks 1
- The difference in grip strength between 40° and 20° fusion is minimal, suggesting that slightly less flexion may be acceptable when aesthetics are a concern 2
Functional Considerations
When determining the optimal angle for PIP joint arthrodesis, consider:
- Grip strength: While all fusion angles reduce grip strength compared to normal joints, intermediate angles (40-45°) generally preserve the most strength 1, 2
- Hand function: The Jebsen Hand Function Test shows that intermediate angles allow better performance in daily activities 1
- Border digits: The index and little fingers have specific functional requirements, with the little finger requiring more flexion (50-55°) to maintain proper grip 1
Surgical Technique Considerations
When performing PIP joint arthrodesis:
- The guide wire angle during minimally invasive techniques is the most critical step as it determines the final fusion angle 3
- Careful attention must be paid to avoid malrotation during screw insertion 3
- Flat surfaces should be obtained during articular surface preparation to ensure proper fusion 3
Pitfalls and Caveats
- Avoid excessive flexion: Angles greater than recommended can impair certain hand functions and create aesthetic concerns
- Avoid insufficient flexion: Angles less than 20° significantly reduce grip strength due to the quadriga effect 2
- Consider individual needs: While 40° is generally optimal, patients with specific functional or aesthetic concerns may benefit from slightly less flexion (20-30°) with minimal impact on grip strength 2
- Border digits require special attention: The index and little fingers have unique functional requirements that necessitate specific fusion angles 1
By adhering to these evidence-based recommendations for PIP joint arthrodesis angulation, optimal hand function can be preserved while addressing the underlying pathology requiring fusion.