What injury involves compression of the ulnar nerve in the tunnel of Guyon?

The injury that involves compression of the ulnar nerve in the tunnel of Guyon is known as "Handlebar palsy." This condition typically occurs due to prolonged pressure on the ulnar nerve as a result of gripping, which is common among cyclists who rest heavily on the handlebars. This compression can lead to symptoms such as numbness, tingling, or weakness in the hand, particularly affecting the ring and little fingers, as these are the areas supplied by the ulnar nerve.

Understanding the mechanism behind Handlebar palsy highlights the importance of ergonomic positioning and the appropriate use of equipment during cycling to prevent nerve injuries. While the other options mention conditions that affect the hand and fingers, they do not specifically involve ulnar nerve compression in that anatomical location. For instance, Bowler's thumb relates to trauma from gripping a bowling ball, Dupuytren's contracture involves a thickening of tissue in the palm, and Mallet finger is a tendon injury that affects the ability to straighten a fingertip. Each of these conditions manifests differently and is rooted in different anatomical or functional issues in the hand.