See: [Commonly Missed or Mismanaged Wrist Injuries | EM Cases](cubox://card?id=7136984070055004739), [Schwarz radiology - wrist radiograph](x-devonthink-item://2A71AF1A-4715-4D5F-9841-03401D8E6C4E?page=258) see also: [[Distal radial ulnar joint dislocation]], [[Scaphoid wrist fracture]] #radiology > [!key points] > - Carpal dislocation injuries need **emergent** orthopedic consultation in the ED for **reduction and stabilization**. > - ED management of dissociations without evidence of dislocation or neurovascular injury consists of immobilization and urgent orthopedic follow up within one week. > - stage I is scapho-lunate dissociation ; stage IV is lunate dislocation # anatomical overview ![[Pasted image 20241102093952.png]] ![[Pasted image 20241102094058.png|normal alignment of carpal rows. astrisk is indentation of radial margin of scaphoid as a normal variant. arrow: pisiform. arrowhead: hook of hamate]] ![[Pasted image 20230826180150.png]] ![[Pasted image 20230826174430.png| Sequential stages of carpal dislocation. Each of four stages (I–IV) represents a sequential intercarpal ligament injury proceeding around the lunate.]] > stage I - scapho-lunate dissociation > stage II - perilunate dislocation > stage III - perilunate with triquetrium dislocation > stage IV - lunate dislocation ![[Pasted image 20241102094941.png]] # overview - usually caused by **wrist hyperextension**, ulnar deviation, and intercarpal supination - usually FOOSH # complications - median nerve injury - chronic carpal instability - degenerative arthritis # scapholunate dissociation - widening of scapholunate joint ("david letterman" or terry thomas sign) on PA view - distal pole of cortex of scaphoid seen as a ring "signet ring" - stress views (clenched fist and with ulnar deviation) can accentuate widening ![[Pasted image 20230826175533.png| Scapholunate Dissociation With Scaphoid Subluxation. black arrow: widening of the scapholunate joint (david letterman sign - prev Terry-Thomas sign). White arrow: a ring shadow over the scaphoid secondary to subluxation ( signet ring sign)]] ![[Pasted image 20241102093107.png|another subtle scapho-lunate dislocation / disassociation (I missed this on the practice test and called it a scaphoid fracture... )]] # perilunate dislocation - best seen on lateral view - capitate dorsally dislocated ![[Pasted image 20241102095640.png]] ![[Pasted image 20230826175914.png]] **Perilunate Dislocation.** (A) PA view of the wrist shows an ==abnormal-appearing lunate bone==, obvious disruption of the normal carpal arcs, and commonly associated and, in this case, displaced scaphoid fracture. (B). Lateral view shows a dislocated and dorsally displaced capitate bone in relation to the lunate. Of note, the lunate maintains its articular connection and alignment with the radius, suggesting a perilunate dislocation. # lunate dislocation - stage IV injury - triangular appearance ("piece of pie sign") of lunate on PA view, caused by rotation of the lunate in volar direction - on lateral view, lunate looks like cup tipped forward spilling its contents - capitate seen to lie posterior to the lunate ![[Pasted image 20241102095721.png]] ![[Pasted image 20230826180307.png]] **Lunate Dislocation.** (A). This posteroanterior view shows the characteristic ==triangular shape of the lunate bone== during dislocation. (B) Volar displacement of the lunate resembles a ==spilled teacup== on the lateral view. Note the disrupted articulation between the lunate and distal radius and realignment of the radius, capitate, and metacarpals, suggesting lunate dislocation.