2General 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
3Mechanism 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
4Diagnosis 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
5Management ABC Splint immobilization or backslab Analgesia Elevation IV antibiotics if open fractureRefer to hand surgeon- Closed reduction or ORIF
6Stages 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.
7Stage 1 – Scapholunate dissociation Widening of scapholunatejoint > 2mm on PA viewTerry Thomas sign
8Stage II - Capitate dislocation Dislocation or subluxation of capitateBest seen on lateral viewLunate remains in normal position in relation to distal radius, capitate is dislocated. ( usually dorsally )Scaphoid fracture or subluxation can also occur.
9Stage III – Triquetrum dislocation Perilunate dislocationTriquetral and scaphoid malrotationLunate remains normal position, other carpal bones dislocated posteriorlyMay be associated with triquetrial fracture
10Stage IV - Lunate dislocation Most severe of carpal instabilitiesMost commonly associated with trans scaphoid fractureProduces volar dislocation and forward rotation of lunate. Capitate drops into place vacated by lunateLunate appears triangular in shape on frontal view ( piece of pie sign )Spilled tea cup sign
24Lunate 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
25Dislocation 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).