Ulnar claw

A 30-year-old man comes to the office to evaluate clumsiness and a pins-and-needles sensation in his right hand. The patient is worried that he won’t be able to participate in an upcoming road bicycle race due to his hand weakness. The patient suffered a fall while riding his bicycle four months ago. Vitals are within normal limits. Physical examination of the right hand demonstrates hypothenar eminence atrophy, decreased sensation over the 4th and 5th digits, diminished finger abduction, and weakness in adduction of the fingers and thumb adduction. Which of the following is the most likely site of nerve injury?