What type of splint is recommended for a typical non‑displaced fracture of the first metacarpal (thumb)?

Thumb Spica Splint for First Metacarpal Fracture

For a non-displaced first metacarpal fracture, immobilize with a thumb spica splint that holds the thumb in an intrinsic-plus (balanced) position while allowing full wrist flexion-extension, and maintain rigid immobilization for 3–6 weeks. 1

Splint Configuration

• The splint must lock the metacarpophalangeal (MCP) joint but allow interphalangeal (IP) joint motion to reduce the risk of joint stiffness 1
• Position the thumb in a balanced (intrinsic-plus) position with volar abduction 1, 2
• Allow full wrist flexion and extension – do not immobilize the wrist 1, 2
• Use rigid (non-removable) immobilization rather than removable splints to preserve reduction 1

The key distinction here is that first metacarpal fractures require thumb spica immobilization, not the ulnar gutter or radial gutter splints used for other metacarpal fractures. The thumb spica specifically stabilizes the thumb ray while preserving wrist motion, which prevents forearm muscle atrophy and maintains functional capabilities during healing 2.

Immediate Management

• Obtain three-view radiographs (postero-anterior, lateral, and oblique) immediately to evaluate fracture displacement, articular involvement, and malrotation 1
• Do not rely on only two-view radiographs, as they may miss displacement or malrotation 1
• Apply the splint after confirming adequate alignment on imaging 3

Active Rehabilitation During Immobilization

• Initiate active IP-joint range-of-motion exercises immediately while the MCP joint remains splinted 1
• Instruct the patient to move the IP joint through complete range of motion regularly throughout the immobilization period 1
• This prevents stiffness of the distal thumb joints, which is one of the most functionally disabling complications 4

Follow-Up Protocol

• Obtain repeat radiographs at 10–14 days to confirm that fracture alignment is maintained 1
• Continue radiographic monitoring at 3 weeks and again at the end of immobilization 1
• Total immobilization time for stable, minimally displaced fractures should be 3–6 weeks 1

Indications for Surgical Referral

Refer for orthopedic consultation if any of the following are present: 1

• Fracture displacement greater than 3 mm
• Involvement of more than one-third of the articular surface
• Interfragmentary gap exceeding 3 mm
• Clinical malrotation (e.g., scissoring of the thumb when the patient makes a fist)

These criteria are based on radiographic and clinical assessment and indicate fracture instability requiring surgical fixation 1.

Common Pitfalls

• Avoid immobilizing the wrist – this leads to unnecessary forearm muscle atrophy and prolonged functional limitation without improving fracture outcomes 2
• Do not use removable splints for displaced fractures – they fail to maintain reduction 1
• If the patient experiences persistent or worsening pain during immobilization, advise immediate re-evaluation 1
• Immobilization-related complications occur in approximately 14.7% of cases and include skin irritation and muscle atrophy 4

The modified thumb spica cast (allowing wrist motion) has been shown in prospective studies to provide reliable immobilization with improved functional capabilities, good patient acceptance, and no residual loss of position or malunion 2.