1. Perilunate dislocations
Dr. P Kruger

2. 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

3. Mechanism of injury Hyperdorsiflexion of wrist Hyperextension of wrist
Usually due to high-energy trauma to the wrist e.g.
- Fall on outstretched hand
- Motor vehicle and motorcycle accidents

4. Diagnosis Clinical history Index of suspicion Examination of hand
X-Ray + other views if indicated
- closed fist ulnar/radial stress view
- Scaphoid view
- Supination oblique view
- Carpal tunnel view

5. Management ABC Splint immobilization or backslab Analgesia Elevation
IV antibiotics if open fracture
Refer to hand surgeon
- Closed reduction or ORIF

6. Stages 4 stages Originally described by Mayfield.
Each stage represent a sequential intercarpal injury.
Can be associated with specific bony fractures including the radial styloid, scaphoid, capitate and triquetrum.

7. Stage 1 – Scapholunate dissociation
Widening of scapholunate
joint > 2mm on PA view
Terry Thomas sign

8. Stage II - Capitate dislocation
Dislocation or subluxation of capitate
Best seen on lateral view
Lunate remains in normal position in relation to distal radius, capitate is dislocated. ( usually dorsally )
Scaphoid fracture or subluxation can also occur.

9. Stage III – Triquetrum dislocation
Perilunate dislocation
Triquetral and scaphoid malrotation
Lunate remains normal position, other carpal bones dislocated posteriorly
May be associated with triquetrial fracture

10. Stage IV - Lunate dislocation
Most severe of carpal instabilities
Most commonly associated with trans scaphoid fracture
Produces volar dislocation and forward rotation of lunate. Capitate drops into place vacated by lunate
Lunate appears triangular in shape on frontal view ( piece of pie sign )
Spilled tea cup sign

11. Spilled tea cup
sign

12. Triangular shaped lunate

13. Volar lunate dislocation
                                       
Volar lunate dislocation

14. X-ray Examples

15. Normal X-rays

19. Stage I

20. Volar perilunate dislocation

21. Dorsal perilunate dislocation

22. Lunate dislocation

23. Perilunate dislocation

24. Lunate dislocations may be missed in the emergency room through failure to recognize the typical states are"spilled teacup" sign on the lateral wrist x-ray (1a), hand and abnormalities which are not dramatic on the PA film (1b). Examples of complete volar (2) and dorsal (3) lunate dislocations

25. Dislocation of bones in the wrist typically occurs when a person falls on his or her outstretched hand and account for 10% of all carpal injuries.  All the joint spaces at the wrist are normally of uniform width, each about 1-2 mm apart.
Three parallel curvilinear arcs can be drawn to assess carpal alignment (see figure below).  The first arc is drawn over the proximal articular surfaces of the scaphoid, lunate, and triquetrum; the second is drawn over the distal articular surfaces of these bones; and the third is drawn along the proximal articular surfaces of the hamate and capitate.  These arcs are normally smoothly curved and disruption of the arc's continuity implies ligamentous injury and malalignment. 
Although any of the carpal bones can become dislocated, the lunate is the most commonly dislocated bone in the wrist.  Lunate dislocations have been divided into pure lunate, perilunate, and midcarpal dislocations (see figure below).