A patient who is unable to adduct all the digits in the hand may have damage to the ulnar nerve, which innervates the muscles responsible for this action. The ulnar nerve supplies the adductor pollicis muscle, which adducts the thumb, and the palmar interossei muscles, which adduct the index, ring and little fingers⁹ [^10^]. The ulnar nerve also innervates the dorsal interossei muscles, which abduct the digits, but these muscles are antagonized by the median nerve, which innervates the lumbricals⁶. Therefore, if the ulnar nerve is damaged, the median nerve can still produce some abduction of the digits, but not adduction. The ulnar nerve can be injured at various levels, such as the elbow, wrist or hand, depending on the cause of the trauma. Some common causes of ulnar nerve injury include fracture or dislocation of the elbow, compression of the nerve in the cubital tunnel or Guyon's canal, or laceration of the nerve by a sharp object⁵. The symptoms of ulnar nerve injury may include numbness, tingling, pain, weakness, or clawing of the hand. The diagnosis of ulnar nerve injury can be confirmed by nerve conduction studies and electromyography, which measure the electrical activity of the nerve and the muscles it innervates⁵. The treatment of ulnar nerve injury depends on the severity and location of the damage, and may include splinting, medication, physical therapy, or surgery⁵.

Source: Conversation with Bing, 20/11/2023

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