In the dog, injury to which nerve is most likely responsible for walking on the dorsum of the front paw?

The radial nerve is responsible for extending the elbow, carpus, and digits. If this nerve is injured, it can result in the inability to extend these structures, leading to a condition known as "dropped elbow." In dogs, this can manifest as the animal walking on the dorsum (top) of the paw because the affected limb cannot maintain the paw in a normal extended position. Instead, the dog compensates for the lack of extension by allowing the top of the paw to come into contact with the ground as it walks.

In contrast, other nerves listed have different functions. The lateral thoracic nerve primarily innervates the cutaneous trunci muscle and does not have a significant role in the movement of the forelimb's paw. The median nerve primarily affects the flexors of the carpus and digits, while the musculocutaneous nerve innervates flexor muscles of the shoulder and elbow. Neither of these nerves is primarily responsible for the extension required for normal walking on the paw. Thus, injury to the radial nerve is the most likely cause for the specific clinical sign of walking on the dorsum of the front paw.