Perilunate dislocations are severe, disabling injuries generally associated with poor outcomes.1,2 They only account for 7-10% of all carpal injuries,3,4 but are the most common of all carpal dislocations.5 The majority of these injuries involve a scaphoid fracture, with transscaphoid perilunate dislocations, accounting for 61-65% of all perilunate dislocations and fracture-dislocations.5-7 A high-energy force—such as from a motor vehicle collision or fall from a height—is required to produce this insult, and the scaphoid fractures frequently owing to this severe trauma.8 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.29,30 Routine PA X-ray should be evaluated for loss of carpal height, carpal gaps and overlapping carpal bones, disruption of Gilula's arcs and unusual shape of the proximal scaphoid fracture fragment. Traction x-ray views done with the fingers in finger traps and a counterweight at the elbow are very useful diagnostically. These traction views frequently show carpal gaps and other carpal malalignments that are not seen on routine x-rays.29,30,31 The typical mechanism of injury is wrist hyperextension, ulnar deviation, and intercarpal supination with an axial load, which displaces the lunate from the capitate—starting with disruption of the scapholunate ligament—while the radiolunate articulation remains preserved.2 Transscaphoid perilunate dislocations are considered greater arc injuries in the perilunate dislocation injury pattern because they include a fracture, which is the initial destabilizing factor of the carpus, with the final stage being the lunate dislocation.9 Although purely conservative methods were traditionally used to treat transscaphoid perilunate dislocations, most experts currently prefer a surgical approach beginning with closed reduction, followed by open reduction and internal fixation (ORIF) that includes repair of the scaphoid and any damaged ligament(s).2,10,29,30,31
Definitions
- A transscaphoid perilunate dislocation occurs when the articular surface of the capitate is displaced off the articular surface of the lunate—which remains in normal alignment with the distal radius—and the scaphoid is also fractured.
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 transscaphoid perilunate dislocations are done by noting the direction of the displacement of the capitate relative to the lunate. The three possible directions of displacement are dorsal, lateral, and volar.11
- The majority of transscaphoid perilunate dislocations are dorsal, while only ~3% are volar.10,12
- The degree of displacement further characterizes transscaphoid perilunate dislocations. In a true complete dislocation, the articular surface of the capitate 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.11
O – Open vs closed
- The majority of transscaphoid perilunate dislocations are closed: the skin is intact, and there is no route for bacteria to contaminate the joint space.
- Open transscaphoid perilunate dislocations are rare and only account for ~10% of these injuries. When present, these cases always require urgent irrigation, debridement, open reduction, ORIF of thye scaphoid fracture and ligament repair especially the L-T ligament.2
- Open transscaphoid perilunate dislocations have a worse prognosis than closed injuries.2
C – Complex vs simple
- Most transscaphoid perilunate dislocations are simple, meaning that reduction is easily achieved under digital anesthetic block and is not blocked by soft tissue being interposed in the joint between the capitate and lunate joint surfaces.
- Complex (irreducible) transscaphoid perilunate dislocations are extremely rare, but do occur on some occasions.
S – Stability
- A trans-scaphoid perilunate dislocation can usually be reduced into the lunate facet but will not stay anatomically aligned without internal fixation (K-wires or screws of the scaphoid fracture and L-T joint).
- Trans-scaphoid perilunate dislocations are often more stable than pure perilunate dislocations if the waist fracture is transverse, the scapholunate ligament remains intact and the L-T ligament is repaired.
Related anatomy13,14
- 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
- Transscaphoid perilunate dislocations are often associated with a significant amount of additional wrist trauma, including ruptures of the radioscaphocapitate, scapholunate interosseus, and/or lunotriquetral ligaments.15
Overall incidence
- Perilunate dislocations and fracture-dislocations account for 7-10% of all carpal injuries,3,4and they are the most common of all carpal dislocations.5
- The incidence of perilunate fracture-dislocations alone has not yet been defined, but it is clearly known that the scaphoid is involved more than any other bone.15,16
- Transscaphoid perilunate dislocations account for 61-65% of all perilunate dislocations and fracture-dislocations5-7—with most of these injuries being in the dorsal direction—and constitute ~3% of all carpal injuries.17
- 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
- Fractures of the capitate, lunate, and/or triquetrum
- Fractures of the distal radius
- Lunate dislocation and fracture-dislocation
- Extrinsic ligament injuries
- Intrinsic ligament injuries
- Extensor tendon ruptures
- Flexor tendon ruptures
- Acute carpal tunnel syndrome