Perilunate Dislocation Trauma Case for FRCS (Tr & Orth) Oral Examination

This is a lateral radiograph of the wrist that shows a perilunate dislocation. The dorsal view shows a dorsal dislocation of the capitate and distal carpal row. The lunate remains in the lunate fossa of the radius due to strong ligamentous attachments from the short and long radiolunate ligaments. The PA view would reveal gingival line disruption with capitate overlapping the lunate. There are no obvious fractures, but closely examine for any of the more commonly associated bony injuries, including fractures to the radial styloid, scaphoid, capitate, trapezoid, hamate, and ulnar styloid.

There are three in total: the first line follows a smooth curve outlining the proximal convex surfaces of the scaphoid, lunate, and triquetrum; the second line traces the distal concave surfaces of the same bones; and the third line follows the proximal curvatures of the capitate and hamate.

This is a potentially high-energy injury, and the patient needs concurrent assessment and treatment according to ATLS guidelines. For the affected limb, I would perform a circumferential examination to ensure it is a closed injury and assess the neurovascular status of the hand, particularly the median nerve. I would provide the patient with suitable analgesia and arrange for a closed reduction in the emergency department, utilising the Tavernier’s manoeuvre (traction, wrist extension with direct thumb pressure on the lunate, followed by wrist flexion) and place the patient in a plaster of Paris below elbow backslab. I would assess for congruent reduction with AP and lateral radiographs before discussing definitive operative management with the patient.

There are two broad classifications for this injury: greater arc and lesser arc injuries. This injury would be classified as a lesser arc, as it is purely ligamentous. There are typically four stages of lesser arc injuries, with this particular case being classified as a Mayfield stage III perilunate dislocation. Stage I involves the failure of the scapholunate ligament. Stage II involves stage I and lunocapitate joint disruption. Stage III involves stage I, II, and perillunate dislocation. Stage IV involves lunate dislocation (usually volar through the space of Poirier, which has a high rate of carpal tunnel syndrome).