Scaphoid Fractures: The Comprehensive Master Guide

The scaphoid (from the Greek skaphos, meaning "boat") is the keystone of the carpus. It links the proximal and distal carpal rows, coordinating their motion like a mechanical tie-rod. However, this critical biomechanical role, combined with a precarious blood supply, makes the scaphoid one of the most problematic bones in the human body when injured.

This guide serves as a comprehensive reference for the diagnosis, classification, and management of scaphoid fractures.

Visual Element: A detailed 3D exploded view of the carpus, highlighting the scaphoid's articulation with the radius, lunate, capitate, trapezium, and trapezoid.

1. Functional Anatomy and Biomechanics

The scaphoid is unique. It is 80% covered in articular cartilage, leaving very little surface area for ligamentous attachment or vascular entry.

The Blood Supply: A Retrograde Problem

The vascularity is the single most important factor determining the prognosis of a scaphoid fracture.

• Radial Artery: The primary supply comes from the dorsal carpal branch.
• Entry Point: The vessel enters the dorsal ridge at the waist and distal pole.
• The Flow: Blood flows in a retrograde fashion (distal to proximal) to supply the proximal pole.
• Clinical Consequence: A fracture at the waist cuts off the blood supply to the proximal pole. The proximal fragment effectively becomes avascular, relying solely on healing across the fracture site to revascularize. This explains the 100% rate of AVN in displaced proximal pole fractures.

Biomechanics

The scaphoid flexes during wrist flexion and radial deviation, and extends during wrist extension and ulnar deviation.

• The Flexion Moment: The scaphoid has a natural tendency to flex due to loading from the trapezium/trapezoid.
• The Humpback Deformity: When fractured, the distal fragment flexes (palsy-walsy) and the proximal fragment extends (with the lunate - DISI). This collapse creates the "humpback" deformity, which leads to dorsal carpal instability and eventual arthritis.

2. Epidemiology and Mechanism

Scaphoid fractures account for 60-70% of all carpal fractures.

• Patient Profile: Young males (15-30 years) are the highest risk group.
• Mechanism: Fall on an Outstretched Hand (FOOSH). The wrist is typically in extension (>95°) and radial deviation.
• Associated Injuries: Always check for perilunate instability, distal radius fractures, and radial head fractures.

3. Clinical Evaluation

The "Clinical Scaphoid Fracture" is a diagnosis that commands respect. Even if X-rays are normal, high clinical suspicion necessitates treatment.

The "Triad" of Signs:

1. Anatomical Snuffbox Tenderness: (Sensitivity 90%, Specificity 40%). Palpate with the wrist in ulnar deviation.
2. Scaphoid Tubercle Tenderness: Palpate volarly.
3. Axial Compression / Telescoping: Pain on compressing the thumb metacarpal towards the radius.

Clinical Pearl: Pain on resisted supination and pronation can also indicate a scaphoid fracture or scapholunate ligament injury.

4. Imaging Strategy

Radiography

The standard "Wrist Series" is insufficient. You need a dedicated Scaphoid Series:

• PA and Lateral.
• Ziter View (PA with ulnar deviation and 20° tube angulation): Elongates the scaphoid to view the waist.
• Semi-pronated oblique (45°).

Advanced Imaging

• MRI: The Gold Standard. Approaches 100% sensitivity and specificity. It also identifies bone bruising and ligamentous injury. Ideally performed within 3-5 days of injury if X-rays are negative but clinical suspicion remains.
• CT: The best modality for assessing displacement and union. It is mandatory for preoperative planning to assess the "humpback" deformity.
• Bone Scan: Largely obsolete due to MRI, but still highly sensitive after 72 hours.

5. Classification Systems

Understanding the classification guides the treatment.

Russe Classification (Direction of Fracture Line)

• Horizontal Oblique: Compressive forces, stable.
• Transverse: Shear forces, potentially unstable.
• Vertical Oblique: High shear forces, inherently unstable. Hard to fix with a screw.

Herbert Classification (Type)

• Type A: Stable Acute Fractures (A1 Tubercle, A2 Incomplete waist).
• Type B: Unstable Acute Fractures (B1 Distal oblique, B2 Complete waist, B3 Proximal pole, B4 Trans-scaphoid perilunate).
• Type C: Delayed Union.
• Type D: Non-Union.

6. Treatment Strategies

Non-Operative Management

• Indication: Stable, non-displaced fractures (Herbert A2).
• Technique: Cast immobilization.
• Duration: 8-12 weeks. Union must be confirmed on CT, not just clinical lack of pain.
• Colles vs Spica: Evidence suggests a below-elbow cast (excluding the thumb) is sufficient for waist fractures. However, many surgeons still prefer a thumb spica for proximal pole fractures to minimize micromotion.

Operative Management

• Indications: Displacement >1mm, Proximal Pole, Vertical Oblique, Comminuted, Perilunate injury.
• Technique: Percutaneous or Open reduction and Internal Fixation (ORIF).
• Hardware: Headless Compression Screw (Acutrak, Herbert). These screws are buried beneath the cartilage.

Surgical Approaches:

1. Volar Approach (FCR approach):
   • Best for: Waist and Distal Pole fractures. Correcting Humpback deformity.
   • Advantage: Avoids the dorsal blood supply.
   • Technique: Between FCR and Radial Artery.
2. Dorsal Approach:
   • Best for: Proximal Pole fractures.
   • Advantage: Allows perpendicular screw placement for proximal pole (which is technically difficult from the volar side).
   • Risk: Damage to the tenuous blood supply entering the dorsal ridge.

Visual Element: Surgical illustration comparing the Volar vs Dorsal screw trajectory.

7. Complications

Avascular Necrosis (AVN)

• Incidence: 30-40% of proximal pole fractures.
• X-ray Appearance: Sclerosis (increased density) of the proximal pole relative to the surrounding osteopenic bone.
• MRI: Loss of signal on T1 and T2.

Non-Union

• Definition: Failure to heal by 6 months.
• Consequence: Leads to abnormal carpal mechanics and SNAC wrist.
• Treatment: Revision fixation + Bone Graft (Matti-Russe inlay, or vascularized graft from 1,2 ICSRA or Medial Femoral Condyle).

SNAC Wrist (Scaphoid Non-Union Advanced Collapse)

The natural history of a non-union is predictable arthritis.

• Stage I: Radiostyloid arthritis.
• Stage II: Scaphocapitate arthritis.
• Stage III: Periscaphoid arthritis (Lunocapitate).
• Stage IV: Pancarpal arthritis (Radiolunate preserved usually).

8. Summary

The scaphoid is unforgiving. A missed diagnosis or inadequate treatment can lead to a lifetime of wrist dysfunction for a young patient.

• Suspect it: Treat clinical tenderness as a fracture until MRI proves otherwise.
• Respect it: Understand the retrograde blood supply.
• Fix it: If displaced or proximal pole.
• Follow it: Ensure union is achieved before discharging.