Scaphoid Fractures: To Fix or Cast?

The scaphoid is often described as the "Ferrari" of the carpal bones: complex, high-performance, and expensive to fix when broken. It links the proximal and distal carpal rows, acting as the primary load-bearing strut of the wrist. However, its evolutionary design left it with a critical flaw: a precarious blood supply.

Scaphoid fractures are the most common carpal bone fracture, typically occurring in young males after a fall on an outstretched hand (FOOSH). While displaced fractures universally require surgery, the management of non-displaced scaphoid waist fractures remains one of the most debated topics in orthopaedics. Do we cast them for months, risking stiffness, or fix them early, risking surgical complications?

Visual Element: Cover image showing a retrograde screw fixation illustration within a translucent scaphoid bone, highlighting the 3D complex shape.

1. The Anatomy of Ischemia: Why is the Scaphoid Special?

To understand the treatment, you must respect the anatomy.

• Retrograde Blood Supply: The scaphoid is supplied primarily (80%) by the dorsal carpal branch of the radial artery. This vessel enters the bone at the distal pole and waist, then flows backward to supply the proximal pole.
• The Watershed: The waist is a vascular watershed area.
• The Risk: A fracture at the waist can disrupt blood flow to the proximal fragment. A fracture at the proximal pole almost certainly does.
  • Proximal Pole: 100% AVN risk if displaced; high non-union risk.
  • Waist: Moderate non-union risk (10-15% if untreated).
  • Distal Pole: excellent blood supply, rarely requires surgery.

Visual Element: Internal SVG diagram showing the retrograde blood supply of the scaphoid, with color-coded "Risk Zones" (Green=Distal, Amber=Waist, Red=Proximal).

2. Diagnosis: The "Clinical Scaphoid"

X-rays are notoriously unreliable immediately after injury. Up to 20% of fractures are not visible on initial films. The "Clinical Scaphoid Fracture" Protocol: If a patient has snuffbox tenderness and pain on axial loading but normal X-rays:

1. Immobilize: Place in a splint.
2. Advanced Imaging: MRI is the gold standard (nearly 100% sensitivity/specificity) and should be obtained early (within 3-5 days) to avoid unnecessary casting of soft tissue sprains. CT is excellent for defining fracture geometry (displacement) but can miss occult trabecular lines.

3. The Treatment Dilemma: Cast vs Screw

For a confirmed, stable, non-displaced waist fracture (Herbert Type A2 or B2), we have two paths.

Option A: Conservative Management (Casting)

• The Protocol: Immobilization for 8-12 weeks.
• Cast Type: The "Colles vs. Scaphoid" debate. Traditional teaching mandated a thumb spica cast including the thumb IP joint. However, multiple randomized trials suggest that a well-molded below-elbow cast (leaving the thumb free) is equally effective for waist fractures and improves patient function.
• Success Rate: ~90-95% union rate.
• The Cost: Stiffness, muscle atrophy, hygiene issues, and "cast disease." 12 weeks is a long time for a young, active person.

Option B: Surgical Fixation (Percutaneous Screw)

• The Protocol: Minimally invasive placement of a headless compression screw (e.g., Herbert, Acutrak) via a volar or dorsal approach.
• The Benefit: Immediate stability. Allows for early mobilization (often within 1-2 weeks).
• Success Rate: ~95-98% union rate.
• The Cost: Surgical risks—infection, scar tenderness, prominent hardware, and iatrogenic cartilage damage (trapeziotrapezoid joint arthritis).

4. The Evidence: The SWIFFT Trial

The debate was largely settled for the general population by the SWIFFT Trial (2020). This massive multi-center RCT compared surgery vs. casting for non-displaced waist fractures.

• Results: No significant difference in pain or function (PRWE score) at 1 year.
• Return to Work: No significant difference.
• Complications: Significantly higher in the surgical group (as expected).
• Economics: Surgery was vastly more expensive.

The Verdict: For the average patient, routine surgery for non-displaced waist fractures is not indicated. Casting is safer and equally effective.

5. The Algorithm: When to Operate?

Despite SWIFFT, we do not cast everyone. Surgery is indicated for:

Absolute Indications

1. Displacement: Any step-off >1mm or gap >1mm.
2. Instability: Scapholunate angle >60° (DISI deformity) or capitolunate angle >15° (Humpback deformity).
3. Proximal Pole Fractures: Due to the tenuous blood supply, these require rigid compression to heal. Fixation should be dorsal (perpendicular to the fracture line).
4. Associated Carpal Instability: Perilunate injuries.

Relative Indications ("The SWIFFT Exceptions")

1. The Elite Athlete: A professional footballer cannot miss a season. Surgery offers a predictable, faster return to contact (with protection), even if long-term union rates are the same.
2. Delayed Presentation: If the fracture is diagnosed >4 weeks post-injury, the biology of the non-union process has begun. Fixation + bone graft might be needed.
3. Patient Preference: The "can't cast" patient (e.g., surgeon, musician, pilot) who accepts the surgical risk to avoid immobilization.

6. Surgical Technique Pearls

• Volar Approach: Best for waist fractures. Preserves the dorsal blood supply. Easier to correct "humpback" flexion deformity by using the screw as a joystick.
• Dorsal Approach: Best for proximal pole fractures. The screw is inserted down the central axis of the scaphoid. Danger: The screw head can bury into the cartilage if not countersunk deeply.
• The Screw: Headless, variable pitch (wider pitch distally, tighter proximally) to generate compression.

Trap: Screw Length. A screw that is too long will penetrate the subchondral bone and destroy the radioscaphoid joint. Always verify with 360° fluoroscopy ("pronate/supinate" views) before leaving the OR.

7. Complications: When it fails

A scaphoid non-union is a disaster. It leads to SNAC (Scaphoid Non-Union Advanced Collapse) wrist—a predictable pattern of progressive arthritis requiring salvage procedures (4-corner fusion, PRC, or total wrist fusion).

• Clinical Pearl: If a patient has persistent pain at 12 weeks despite casting, get a CT scan. "Clinical union" is not enough. You must prove bridging trabeculae.

Summary

• Non-displaced Waist: Cast (Below elbow is fine).
• Proximal Pole: Fix (Dorsal approach).
• Displaced: Fix (Restore anatomy).
• Athlete: Discuss Fixation (Risk vs Benefit).

Treat the patient, not the X-ray. The goal is a united bone with a mobile wrist, and for most, the plaster room is safer than the operating room.