Explanation
The correct option is a. In a classic perilunate dislocation (lesser arc injury), the strong volar radiolunate ligaments remain intact. As a result, the lunate maintains its normal anatomic alignment within the articular concavity of the distal radius. The entire remainder of the carpus (led by the capitate) violently strips away from the lunate and dislocates dorsally. This is in direct contrast to a 'lunate dislocation', where the dorsal ligaments fail, the capitate pushes the lunate out of the joint volarward, and the capitate drops down to articulate directly with the radius. Reference: Mayfield JK. Mechanism of carpal injuries. Clin Orthop Relat Res.