Perilunate dislocations are severe and disabling injuries that are generally associated with poor outcomes.1,2 They account for 7-10% of all carpal injuries3,4 but are the most frequently seen carpal dislocation.5 In most cases, perilunate dislocations result from high-energy trauma such as a motor vehicle crash or fall from a height, and the typical mechanism of injury is wrist hyperextension, ulnar deviation, and intercarpal supination with an axial load.2 This force displaces the lunate from the carpus—starting with disruption of the scapholunate ligament—but the radiolunate articulation remains preserved. Perilunate dislocations and perilunate fracture-dislocations are part of the same injury pattern in which the final stage is a lunate dislocation, but purely ligamentous perilunate (lesser arc) dislocations are challenging injuries in their own right.6 The examination of a patient with a lunate dislocation will show a deformed wrist with limited wrist motion. The fingers will be in a flexed posture and extension causes pain. Frequently, there will be signs of acute carpal tunnel syndrome.16,17,18 Routine PA X-ray should be evaluated for loss of carpal height, carpal gaps and overlapping carpal bones, disruption of Gilula's arcs and a triangular appearing lunate.
Although purely conservative methods were traditionally used to treat these injuries, most experts currently prefer a surgical approach that begins with closed reduction and is followed by open reduction and internal fixation (ORIF) that includes ligamentous and bony repair/reconstruction.2,7,16,17,18
Definitions
- A perilunate dislocation occurs when the articular surface of the carpus is displaced off the articular surface of the lunate, which remains in normal alignment with the distal radius. The capitate will be displaced dorsally or palmarly.
Hand Surgery Resource’s Dislocation Description and Characterization Acronym
D O C S
D – Direction of displacement
O – Open vs closed dislocation
C – Complex vs simple
S – Stability post reduction
D – Direction of displacement
- The primary description and characterization of perilunate dislocations are done by noting the direction of the displacement of the carpus relative to the lunate. The three possible directions of displacement are dorsal, lateral, and volar.8
- The majority of perilunate dislocations are dorsal, while only ~3% are volar.7,9
- The degree of displacement further characterizes perilunate dislocations. In a true complete dislocation, the articular surface of the carpus is no longer in contact with the articular cartilage of the lunate. If there is partial contact of the cartilaginous surfaces, then this is not a true dislocation but rather a joint subluxation.8
O – Open vs closed
- The majority of perilunate dislocations are closed; the skin is intact, and there is no route for bacteria to contaminate the joint space.
- Open perilunate dislocations are rare and only account for ~10% of these injuries. When present, these cases always require urgent irrigation, debridement, open reduction, and ligament repair.2
- Open perilunate dislocations have a worse prognosis than closed injuries.2
C – Complex vs simple
- Most perilunate dislocations are simple, meaning that reduction is technically feasible under anesthetic block and sedation and is not blocked by soft tissue being interposed in the joint between the carpal and radial joint surfaces; however, closed reduction alone is associated with poor outcomes and is not typically advised for these injuries.
- Complex (irreducible) perilunate dislocations are rare but do occasionally occur and may involve interposition of the dorsal joint capsule or some other soft tissue.4
S – Stability
- A completely dislocated perilunate can usually be reduced into the lunate facet but will not stay anatomically aligned without internal fixation (K-wires or screws).
Related anatomy2
- Extensor tendons
- Flexor tendons
- Radial collateral ligament
- Radioscaphocapitate ligament
- Radiolunate ligament (short and long)
- Radioscapholunate ligament
- Radioscaphoid ligament
- Ulnocapitate ligament
- Ulnotriquetral ligament
- Ulnolunate ligament
- Scaphotrapeziotrapezoid ligament
- Scaphocapitate ligament
- Triquetrohamatecapitate ligament
- Dorsal radiocarpal ligament
- Dorsal intercarpal ligament
- Space of Poirer
- Osteology of the carpals
- The scapholunate and lunotriquetral ligaments are the lunate’s two major intercarpal attachments, which maintain a state of balance between the opposing forces. When one of these ligaments is disrupted, the balance is lost and the lunate is dominated by the remaining intercarpal relationship.
Overall incidence
- Because lunate dislocations and perilunate dislocations are part of the same injury pattern, many statistics group the two entities together, and it may therefore be difficult to distinguish individual characteristics of each.
- Perilunate dislocations account for 7-10% of all carpal injuries,3,4 but they are the most frequently occurring carpal dislocation.5
- Between 16-25% of perilunate dislocations are not accurately diagnosed upon initial evaluation.5,10
- Up to 10% of perilunate injuries are open, 26% are associated with polytrauma, and 11% have ipsilateral concomitant upper extremity injuries.2
Related Injuries/Conditions
- Axial carpal fracture-dislocations which disrupt the distal carpal row and the metacarpal arch can be associated with lunate and perilunate dislocations
- Fractures of the scaphoid, lunate, and/or triquetrum
- Fractures of the distal radius
- Perilunate fracture-dislocation
- Lunate dislocation and fracture-dislocation
- Extrinsic ligament injuries
- Intrinsic ligament injuries
- Extensor tendon ruptures
- Flexor tendon ruptures
NOTE: For additional information see also carpal fractures adult - lunate fracture