Scaphoid fractures are the most common carpal fracture, representing 50% to 80% of all carpal injuries and a significant cause of long-term wrist morbidity. Understanding the anatomy, classification, and management principles is critical for optimal outcomes.
Etiology and Anatomy
The typical mechanism of injury is a fall onto the outstretched hand, resulting in an axial compressive force with the wrist in hyperextension, ulnar deviation, and intercarpal supination.
The scaphoid is a critical, oblique strut that spans both the proximal and distal carpal rows. It is divided into the proximal pole, waist, distal pole, and tubercle.
Classification and Incidence
Scaphoid fractures are classified by location, pattern (Russe), and displacement.
| Fracture Location | Incidence | Nonoperative Healing Rate | Time to Union | Risk of Nonunion/Osteonecrosis |
|---|---|---|---|---|
| Waist | 80% | 80% to 90% | 8 to 12 weeks | Moderate |
| Proximal Pole | 10% to 20% | 60% to 70% | 12 to 24 weeks | High |
| Distal Pole/Tuberosity | 5% | 100% | 6 to 8 weeks | Low |
Vascular Supply: The Key Determinant of Prognosis
The scaphoid's tenuous, retrograde blood supply dictates the high risk of nonunion and osteonecrosis, particularly for proximal fractures.
- The major supply is derived from scaphoid branches of the radial artery, entering the dorsal ridge.
- These dorsal branches supply the proximal 70% to 80% of the scaphoid.
- The volar scaphoid branches supply the distal 20% to 30%.
- Fractures at the waist or proximal third can disrupt the primary vascular supply to the proximal fragment.
Diagnosis and Imaging
Clinical Evaluation
- Well-localized tenderness is the most consistent sign.
- Tenderness is typically elicited in the anatomic snuffbox or volarly over the distal tubercle.
- Provocative tests, such as the Watson shift test, are used, although primarily for scapholunate ligament injuries.
Radiographic Evaluation
- Standard views include PA in ulnar deviation (to extend the scaphoid), lateral, supinated AP, and pronated oblique.
- Initial films are nondiagnostic in up to 25% of cases.
- Management of Suspected Fracture: If the clinical exam is positive but X-rays are normal, immobilization for 1 to 2 weeks (thumb spica) is indicated, followed by repeat X-rays.
- Advanced Imaging:
Management Principles
Nonoperative Treatment
Indications: Nondisplaced acute (less than 4 weeks) waist and distal third fractures.
- Immobilization: A long arm thumb spica cast for 6 weeks (wrist in slight flexion and slight radial deviation) is typically followed by a short arm cast until union.
Operative Treatment
Indications for Surgery (Unstable Fractures):
- Displacement >1 mm
- Angular angulation >10 degrees
- Fracture comminution
- Abnormal carpal angles (e.g., Radiolunate angle >15°; Scapholunate angle >60°; Intrascaphoid angle >35°)
- Proximal third fractures are generally considered for operative fixation due to the high nonunion rate.
- Nonunion
Surgical Technique:
- Fixation typically involves the insertion of screws.
- The screw must be inserted along the central axis of the scaphoid to maximize stability.
- The volar approach is often utilized for open reduction and internal fixation and is considered the least damaging to the vascular supply of the proximal pole.
Complications
- Delayed Union, Nonunion, and Malunion: Require aggressive operative fixation, often with bone grafting.
- Osteonecrosis: Occurs especially with proximal pole fractures due to the tenuous blood supply.
- Nerve Injury: Risk to the dorsal sensory branch of the radial nerve (dorsal approach) or the palmar cutaneous branch of the median nerve (palmar approach).
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