“…2 The ulnar artery is the most common site of aneurysm formation in the upper extremity as it has little protection in Guyon's canal, making the vessel wall prone to trauma when compressed against the hook of hamate. 3 Repetitive hand pounding with manual labour or sport is the most common cause, predominantly affecting right hand dominant men. 4 This may manifest as hypothenar hammer syndrome, whereby patients experience pain and digital ischaemia when striking the ulnar palm.…”