What is the most likely physical examination abnormality in a patient with a humeral mid-shaft fracture?

In the context of a humeral mid-shaft fracture, the most likely physical examination abnormality is the inability to extend the wrist against resistance. This is due to the proximity of the radial nerve, which runs along the humeral shaft and is often injured in mid-shaft fractures. When the radial nerve is compromised, it results in weakness of the muscles responsible for wrist extension, such as the extensor carpi radialis and extensor digitorum. This leads to a classic presentation known as wrist drop, where the patient cannot extend the wrist or fingers.

The other options present conditions that do not typically arise from a mid-shaft humeral fracture. Numbness over the deltoid muscle is more indicative of an axillary nerve injury, which is usually associated with proximal humeral fractures. Winging of the scapula occurs due to injury of the long thoracic nerve, affecting the serratus anterior muscle and is not a common consequence of mid-shaft fractures. Weakness of the rotator cuff suggests problems related to the shoulder's rotator cuff muscles, which are not typically directly impacted by a fracture in the mid-shaft of the humerus. Overall, the implications of radial nerve injury highlight why inability to extend the wrist is