Scaphoid fractures


Introduction

Anatomy

See Scaphoid
Recall basics of scaphoid kinematics, which are disrupted in scaphoid fractures as follows:

  • After a fracture the proximal pole rotates into extension via triquetral-hamate articulation
  • After a fracture the distal pole pulled into flexion by scaphotrapeziotrapezoid articulation
  • Reverse manipulations create angulation, which has a deleterious effect carpal kinematics and fracture healing

Classification

Scaphoid fractures can be classified by pattern/Russe

  • Horizontal oblique
  • Transverse
  • Vertical oblique

Or by location:

  • Distal articular: 2%
  • Distal pole: 8%
  • Tubercle: 8%
  • Waist 65%
  • Proximal pole: 15%

Presentation

The mechanism of injury is often a fall on the outstretched hand (FOOSH). This causes dorsiflexion and ulnar deviation of the wrist and intercarpal supination

Diagnosis

Physical examination of a patient with a scaphoid fracture will show typically swelling, a radially deviated posture and so called “anatomic snuff box” tenderness. Tests to perform include:

Radiographs

  • PA and lateral views of the hand/wrist
  • Oblique views: 45 degrees supination and pronation
  • Clinched fist view
  • Scaphoid view: ulnar deviation/wrist extension

Plain radiographs may be falsely negative in 35-75% of cases

If fracture of the scaphoid is suspected and the films are negative, immobilize the wrist in a cast or splint for 2 weeks and obtain follow-up radiographs. The surgeon may consider additional imaging:

Triple Phase Bone Scan

  • Should be positive within 24 hours and always positive within 48 hours
  • Dynamic flow images are most reliable in acute fractures of the scaphoid
  • Useful in shortening the duration of immobilization without fracture, decreasing complication rate in fracture unrecognized by plain films
  • Problems
    • Time for study to complete
    • Images not as reliable as CT and MRI (false positive rate 25%)

CT Scan

  • Must be obtained in the scaphoid’s plane and with thin cuts
  • Best for surgical planning and accurate assessment of fracture, displacement, angulation
  • Greater sensitivity and specificity than bone scan
  • Less sensitivity but greater specificity than MRI (MRI edema may be over-read as trabecular microfracture)

MRI

  • Sensitivity: 100%; allows early exclusion of occult fracture
  • Accurately detects presence of other occult fractures about the wrist
  • Deemed “the gold standard investigation”
  • May be over-read

Treatment

Non-operative Management

  • Indications: Stable fractures with displacement < 1mm and normal angulation
  • Cast must always include the thumb (thumb motion is transmitted through the scaphoid via ligamentous attachments leading to shear across the fracture site)
  • Length of cast (short arm vs long arm) and length of immobilization (8 weeks vs 12 weeks) debatable
    • Exception: Proximal fractures require ~18 weeks of immobilization

Non-operative Healing Rates

  • Tuberosity and distal third: ~ 100%
  • Waist: 80-90%
  • Proximal: 60-70%

Surgical Management

Indications

  • Displaced fractures: >1mm
  • Instability
  • Fracture angulation (scapholunate angulation <60 degrees)
  • Proximal pole fractures
  • Nonunions: No healing after 20 weeks closed treatment
  • Unrecognized/untreated fracture: 4 weeks

Surgical Options

  • Closed reduction with percutaneous pinning
  • Closed reduction with percutaneous compression screw
  • Open reduction with compression screw

Open Approaches

  • Dorsal approach: Proximal pole and waist
  • Volar approach: Distal pole

Surgical Technique Pearls

  • 1.0 mm guide-wire through center of scaphoid
  • Guide-wire inserted volar; direct proximally, dorsally and ulnar
  • May place anti-rotation wire parallel to guide-wire
  • Drive to level of subchondral bone in proximal pole
  • Err toward shorter screw size
  • After measurement, drive wire into distal radius to prevent displacement
  • Importance of central third placement of screw: 43% greater stiffness; 39% greater load at failure
  • ORIF techniques
    • Avoid violating the RSCL; preservation maintains the proximal pole within the fossa of distal radius
    • If fracture does not reduce with extension and ulnar deviation extend incision to level of RSCL; landmark for realignment is scaphoid articular border with capitate
    • Pack corticocancellous bone graft into areas of comminution

Complications

  • Non-union

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