Does an ulnar gutter splint cover the middle finger?

Ulnar Gutter Splint Coverage

No, a traditional ulnar gutter splint does not cover the middle finger—it immobilizes only the ring and small fingers along with the wrist. However, recent evidence suggests that including the middle finger may be beneficial in specific clinical scenarios, particularly for ring finger metacarpal fractures 1.

Standard Ulnar Gutter Splint Configuration

• The conventional ulnar gutter splint immobilizes the ring and small fingers only, extending from the forearm to the fingertips 2, 3.
• This splint is primarily used for fourth and fifth metacarpal fractures (boxer's fractures) and other ulnar-sided hand injuries 3, 4.
• The middle finger remains free to move in standard applications 2.

When to Include the Middle Finger

For ring finger (4th metacarpal) fractures specifically, including the middle finger in the ulnar gutter splint is recommended to prevent iatrogenic rotational deformity 1.

Evidence for Three-Finger Immobilization:

• A 2022 cadaveric study demonstrated that traditional two-finger ulnar gutter splints (ring and small fingers only) can cause iatrogenic pronation of the distal ring finger metacarpal fragment during splint molding 1.
• This rotation can result in crossover deformity where the ring finger overlaps the small finger 1.
• Including the middle finger significantly reduced rotational displacement at all weight levels tested, reaching statistical significance at 10 pounds (2.8 mm vs 1.8 mm displacement) 1.
• The three-finger configuration provides better rotational control and prevents malrotation of ring finger metacarpal shaft fractures 1.

Clinical Application Algorithm

For 5th metacarpal fractures:

• Use standard two-finger ulnar gutter splint (ring and small fingers only) 2, 3, 4.

For 4th metacarpal fractures:

• Include the middle finger in addition to ring and small fingers to prevent rotational deformity 1.

For 3rd metacarpal fractures:

• Consider alternative splinting that immobilizes the fracture site while allowing finger motion 5.

Common Pitfall

The most critical error is using a standard two-finger ulnar gutter splint for ring finger metacarpal fractures without recognizing the risk of iatrogenic rotation 1. Overzealous molding of the splint material can inadvertently pronate the distal fracture fragment, creating a crossover deformity that may require surgical correction 1.