Delayed Formation of Traumatic Ulnar Artery Pseudoaneurysm Presenting With Ulnar Nerve Palsy: A Case Report.

Ulnar artery pseudoaneurysm (UAP) is a rare occurrence after penetrating injury to the distal upper extremity and may lead to complications such as rupture, sensorimotor dysfunction, and compartment syndrome. We present the case of a 57-year-old man who developed delayed UAP after suffering a penetrating injury to the right forearm. UAP was diagnosed a week after the injury using CT angiography (CTA), which was indicated due to the onset of ulnar nerve palsy (mildly reduced hand-grip strength and fourth- and fifth-digit hypoesthesia and numbness) and growing swelling and tenderness of the right forearm. Due to concerns about UAP and hematoma formation, with resultant compression of the ulnar nerve and suspected hematoma infection, surgical intervention was performed wherein a moderate-size hematoma was evacuated and the ulnar artery was ligated. The decision to ligate rather than reconstruct was based on the suspected infected nature of the hematoma and adequate perfusion of the palmar arch by the radial artery. This case highlights the need for maintaining a strong index of suspicion for UAP after penetrating trauma to the distal upper extremity, due to the possibility of debilitating nerve deficits and compartment syndrome complicating late diagnosis. We also present an algorithm for the choice of management modality for UAP, which is a valuable addition to the existing literature.