Causes / typical injury mechanism: Lunate dislocation arises as a result of trauma, typically axial loading with wrist extension, supination, and ulnar deviation following a fall, motor vehicle collision, or sports injury. It is important to maintain a high index of suspicion for this injury in high-energy trauma and also to ensure that adequate imaging is obtained, as this injury is often missed.

Classic history and presentation: Lunate dislocation presents as pain over the palmar or dorsal wrist and may be associated with stiffness and deformity. Delayed diagnosis may occur in up to 25% of cases. Approximately 10% of cases involve open injuries, and 26% occur in the setting of polytrauma.

The typical patient is an individual with a history of trauma from a fall, motor vehicle collision, or sports injury with associated examination findings and x-rays showing perilunate dislocation or lunate dislocation.

Grade / classification system (if any):
The Mayfield classification is used to stage the injury.

• Stage I injury may show a widened scapholunate interval due to either a disrupted scapholunate ligament or transscaphoid fracture.
• Stage II injury presents with dorsal dislocation of the capitate (due to lunocapitate articulation disruption) as well as the findings seen in stage I injury.
• Stage III injury presents with overlap of the triquetrum on the lunate (due to lunotriquetral ligament disruption).
• Stage IV injury presents as lunate dislocation (due to circumferential disruption of the ligamentous attachments of the lunate).