Ulnar Gutter Splint Application for Nondisplaced Transverse 4th Metacarpal Fracture
Apply an ulnar gutter splint immobilizing the wrist, 4th and 5th metacarpals, and the 4th and 5th fingers in the "intrinsic plus" position (MP joints at 70-90° flexion, IP joints in extension), extending from below the elbow to the fingertips.
Splint Configuration and Positioning
The ulnar gutter splint is the standard immobilization method for 4th and 5th metacarpal fractures 1. For your nondisplaced transverse 4th metacarpal fracture specifically:
Key Positioning Elements:
- Wrist position: Neutral to slight extension (approximately 20-30°)
- MP joints: 70-90° of flexion (intrinsic plus position)
- PIP and DIP joints: Full extension or near-full extension
- Forearm: Include from just below the elbow to the fingertips
Critical Technical Point for 4th Metacarpal Fractures
Include the middle (3rd) finger in your splint, not just the ring and small fingers. This is crucial for 4th metacarpal fractures. Recent cadaveric evidence demonstrates that traditional ulnar gutter splints incorporating only the 4th and 5th fingers can cause iatrogenic rotational displacement of the distal fragment in ring finger metacarpal fractures 2. When pressure is applied during splint molding (simulating typical clinical application), the 2-finger configuration allows significantly more rotation (2.8 mm vs 1.8 mm at 10 lbs pressure, p<0.05) compared to including the middle finger 2. This rotational displacement can result in crossover deformity where the ring finger overlaps the small finger.
Splint Application Technique
Materials and Construction:
- Use plaster or fiberglass splinting material
- Apply along the ulnar aspect of the forearm and hand
- Width should cover from the ulnar border extending to include the middle finger
- Thickness: 8-10 layers of plaster or equivalent fiberglass
Molding Strategy:
- Avoid overzealous molding over the fracture site, as this creates the rotational forces that displace the distal fragment 2
- Mold gently along the ulnar border of the hand and forearm
- Ensure the three-point mold maintains the metacarpal arch without excessive pressure
- The intrinsic plus position itself provides stability; aggressive molding is counterproductive
Alternative Approach:
A functional metacarpal splint that immobilizes only the metacarpals while allowing IP joint motion has shown success in similar fractures 3, 4. This involves:
- Immobilizing the MP joints in flexion
- Allowing active IP joint mobilization
- Maintaining wrist immobilization
However, for initial management of a nondisplaced fracture, the traditional ulnar gutter with the 3-finger modification is more straightforward and proven.
Duration and Follow-up
- Initial immobilization: 3-4 weeks
- Radiographic follow-up: Obtain repeat films at 7-10 days to confirm maintained alignment 5
- Splint removal: Typically at 4 weeks if radiographs show adequate healing
- Rehabilitation: Begin range of motion exercises after splint removal, followed by strengthening at 6 weeks 4
Common Pitfalls to Avoid
Using only 2 fingers (ring and small) for 4th metacarpal fractures - this is the most critical error, leading to rotational malunion 2
Excessive molding pressure - creates iatrogenic displacement rather than maintaining reduction
Inadequate MP flexion - the intrinsic plus position is essential for fracture stability; insufficient flexion allows the fracture to angulate
Immobilizing IP joints in flexion - this leads to stiffness without added fracture stability; IP joints should be extended
Insufficient length - the splint must extend from below the elbow; shorter splints don't adequately control rotation
The nondisplaced nature of your fracture is favorable and should heal well with proper immobilization. The key is preventing displacement during the healing period through appropriate splint configuration, particularly the 3-finger inclusion for 4th metacarpal fractures.