Acute Traumatic Swan Neck Deformity: A Case Report of the Oblique Retinacular Ligament Lesion.

Swan neck deformity (SND) can be the manifestation of an acute trauma. We present a case report of a young basketball player with an acute traumatic SND determined by the single ulnar oblique retinacular ligament rupture. The patient caught a ball directly upon the tip of his right's hand middle finger into extension. He immediately presented a SND with impossibility to actively flex the proximal interphalangeal joint (PIPJ), while preserving active flexion and extension of the distal interphalangeal joint (DIPJ). Hyperextension of PIPJ was reducible with passive mobilization, thus allowing full passive range of motion. The SND was seen to be caused by the lesion of the ulnar oblique retinacular ligament (ORL) on its distal insertion, with consequent dorsomedial migration of the ulnar lateral band. The early surgical distal reinsertion of the ORL allowed the restoration of the original kinematics of the finger flexion-extension.