WRIST INJURIES

I. Fracture of the scaphoid (aka navicular)

  1. Most common fracture of wrist
  1. This is probably because it's the only carpal bone to cross the mid-carpal joint, where most wrist motion takes place
  2. Usual mechanism is "FOOSH" (fall on outstretched hand)
  1. Divided into 3 parts: distal pole, waist (where blood supply enters), proximal pole
  2. High index of suspicion is necessary because x-ray may be negative for up to 2wks after fx; avascular necrosis can occur with untreated fx
  3. Px features:
  1. Snuffbox tenderness is sensitive but nonspecific
  2. Pain with axial compression of thumb sensitive but nonspecific
  3. Pain at tuberosity (extend wrist and press at prox. wrist crease)
  4. Pronation and supination of wrist against resistance, e.g. while shaking hands: will usually be painful with fracture
  1. If clinically suspicious and x-rays negative, still immobilize & re-check at 2wks; if still clinically suspicious and x-ray neg, do bone scan, CT, or MRI
  2. If unstable (> 1mm displacement or fragments are angled, or lat. x-ray shows malalignment of carpal bones, vertical or transverse fx), may need ORIF
  3. If waist or proximal, may need ORIF
  4. Healing time depends on location of fracture: the more proximal the fracture; the more delayed the healing. Short- or long-arm thumbe spica cast until healing is complete; re-evaluate every 3-4wks with x-rays to confirm non-displacement.
  1. Distal 1/3: 8wks to heal
  2. Waist 1/3: 12 wks
  3. Proximal 1/3: 16 wks or more

II. Lunate

  1. The most commonly dislocated wrist bone but only 3rd most commonly fractured
  2. Xrays almost always negative in fx
  3. If suspect fx, immobilize and re-xray in 2-3wks; if x-rays still negative and still tender, may need tomogram, CT, or MRI
  4. Median nerve runs volar to lunate; be alert to possibility of median nerve injury
  5. Kienbock's disease (avascular necrosis of the lunate) can occur after fracture, especially with the anatomic variant of "negative ulnar variance" (see below)

III. Triquetrum

  1. Distal to ulnar styloid and posterior to pisiform; may be difficult to palpate (easier with radial deviation of wrist
  2. Second most common carpal fracture
  3. Chip or avulsion fractures should be treated with short-arm cast for 4-6 wks
  4. Non-union may require surgical excision

IV. Pisiform

  1. Fractures may be treated with short arm cast in slight flexion for 3-6 wks. Communited fractures may need surgery

V. Capitate

  1. As with scaphoid and lunate, capitate fractures ass'd with significant risk of avascular necrosis; ortho consult should be considered

VI. Hamate

  1. Fractures of hook are more common than fractures of body; standard views may not show it; carpal tunnel views usually will
  2. Check ulnar nerve status; ulnar nerve injury may occur as a complication of healing secondary to fibrosis, etc.
  3. Nondisplaced hook or body fractures treated with casting with wrist in flexion & 4th and 5th MCP joints in slight flexion for 3-4 wks; consult ortho for displaced fx

VII. TFCC

  1. Includes triangular fibrocartilage, ulnar collateral ligament, and distal radioulnar ligament.
  2. In TFCC tears, x-rays often nl; arthrography may show injury

VIII. Wrist x-rays

  1. Radial styloid extends about 11mm distal to ulnar styloid
  2. Distal radius is slanted about 22' relative to distal ulna
  3. "Ulnar variance" is when ulna is longer ("positive") or shorter ("negative") than ulnar sider of the radius. It exists in about 50% of people and can be normal but is associated with increased risk for TFCC injury (if positive) or Kienbock's avascular necrosis of the lunate (if negative)
  4. Intercarpal bone spacing is usually constant (2mm); variation in spacing implies subluxation, arthritis, or fx. Most common dislocation is scapholunate; this can be accentuated by AP clenched-fist view.
  5. On lateral x-ray; distal radius should have 11' palmar slant