Which muscle function is retained in cases of posterior interosseous nerve injury?

In cases of posterior interosseous nerve injury, the muscle functions that are retained include those innervated by the branches of the radial nerve that remain intact, specifically the triceps brachii and the supinator muscle.

The posterior interosseous nerve primarily innervates the extensors of the wrist and fingers, so when this nerve is injured, the ability to extend the wrist and fingers is compromised. However, the triceps muscle, which is responsible for elbow extension, and the supinator muscle, which allows for forearm supination, will continue to function properly because they are supplied by the radial nerve, which is not affected by the posterior interosseous nerve injury.

Thus, while wrist and finger extension is impaired due to the injury, the actions governed by the triceps and supinator remain intact, allowing for residual functionality in the affected limb despite the nerve injury. This distinctive preservation of certain muscle functions highlights the anatomical pathways of nerve supply within the forearm and upper arm, emphasizing the functional compartmentalization of nerve innervation.