Age / Sex : 19 / M

Age / Sex : 19/Male

Chief complaint : Left wrist pain after pedestrian traffic accident

Transscaphoid perilunate dislocation

Discussion

Findings:
Fracture at left scaphoid on AP view
Posterior dislocation of capitate head from lunate distal surface on lateral view

Diagnosis: Transscaphoid perilunate dislocation

Discussion:

Carpal dislocations

1. General points:

- Can be missed easily

- If left untreated lead to high incidence of long term functional disability and chronic pain.

- Perilunate dislocations more common than lunate dislocations

2. Mechanism of injury

- Hyperextension (dorsiflextion) of wrist

- Fall on the outstretched hand followed by motor vehicle crash

3. Stages by Mayfields.

- Each stage represent a sequential intercarpal injury.

- Can be associated with specific bony fractures including the radial styloid, scaphoid, capitate and triquetrum.

1) Stage 1 - Scapholunate dissociation

- Widening of scapholunate (joint space > 2mm on PA view)

- Terry Thomas sign

2) Stage II – Posterior perilunate dislocation

- Dislocation of capitate head from lunate distal surface

- Best seen on lateral view

- Lunate remains in normal position in relation to distal radius, capitate is dislocated.

- Scaphoid fracture (75%) or subluxation can also occur.

3) Stage III - Stage II + triquetrum dislocation

- Triquetral and scaphoid malrotation

- Lunate remains normal position, other carpal bones dislocated posteriorly

- May be associated with volar triquetrial fracture

4) Stage IV – Anterior lunate dislocation

- Most severe of carpal instabilities

- Most commonly associated with transscaphoid fracture

- Involves all the intercarpal joints and disruption of most of the major carpal ligaments

- Capitate drops into place vacated by lunate

- Lunate appears triangular in shape on frontal view (piece of pie sign)

- Spilled tea cup sign

References:

1.     Wrist Fractures: What the Clinician Wants to Know. Charles A. Goldfarb, Yuming Yin, et al. Radiology 2001; 219:11–28

2.     Orthopedic Pitfalls in the ED: Lunate and Perilunate Injuries. Andrew D, et al. Am J Emerg Med 2001;19:157–162