Which condition impairs flexion of the 4th and 5th digits?

The condition that impairs flexion of the 4th and 5th digits is Guyon canal syndrome. This condition occurs when the ulnar nerve is compressed or trapped in Guyon's canal, a fibro-osseous tunnel located at the wrist. As a result of this compression, the ulnar nerve loses its ability to effectively innervate the flexor muscles responsible for flexing the 4th and 5th fingers, particularly the flexor digitorum profundus muscle. This leads to weakness or inability to flex these digits, which is a hallmark sign of this syndrome.

Cubital tunnel syndrome primarily affects the ulnar nerve at the elbow but can also lead to symptoms in the 4th and 5th digits. However, in this context, the direct compression of the ulnar nerve in Guyon's canal more specifically relates to the impairment of flexion in those digits.

Carpal tunnel syndrome involves compression of the median nerve and primarily affects the thumb, index, middle, and part of the ring finger, sparing the 5th digit. Similarly, median nerve compression impacts the first three digits and does not affect the ulnar-innervated digits.

Therefore, Guyon canal syndrome is