A patient with a humeral fracture presents with wrist drop. What nerve injury should be suspected?

In the case of a patient with a humeral fracture presenting with wrist drop, the most likely nerve injury to suspect is a radial nerve injury. The radial nerve runs along the humerus and is particularly vulnerable to damage at the mid-shaft level during a humeral fracture. When the radial nerve is compromised, it leads to weakness or paralysis of the extensors of the wrist and fingers, which results in the characteristic "wrist drop" phenomenon.

Wrist drop refers to the inability to extend the wrist and fingers, which is directly related to the function of the radial nerve. This nerve is responsible for innervating the muscles that extend the elbow, wrist, and fingers, allowing for the normal functioning of these movements. When there's an injury to the radial nerve, the patient's ability to extend their wrist is compromised, leading to the wrist being flexed and unable to be held in a neutral or extended position.

While other nerve injuries, such as those involving the median or ulnar nerves, can cause various upper limb dysfunctions, they are not typically associated with wrist drop. The median nerve affects the ability to oppose the thumb and flex the fingers, while the ulnar nerve primarily impacts the innervation of the intrinsic muscles of the hand