What differentiates posterior interosseous nerve entrapment from radial tunnel syndrome?

The key differentiator between posterior interosseous nerve entrapment and radial tunnel syndrome lies in the presence of motor weakness associated with the posterior interosseous nerve entrapment. The posterior interosseous nerve primarily innervates the extensor muscles of the forearm, and entrapment of this nerve typically leads to weakness in wrist and finger extension, without sensory loss since it is a purely motor branch.

In contrast, radial tunnel syndrome is characterized by pain, primarily in the forearm, that occurs with activities that involve repetitive wrist motions, yet it usually does not cause significant motor weakness. Therefore, while both conditions may present with pain, the definitive presence of motor weakness with posterior interosseous nerve entrapment is a hallmark feature that distinguishes it from radial tunnel syndrome.

This understanding is crucial for clinicians when diagnosing and managing upper extremity nerve entrapments, ensuring that appropriate interventions are provided based on the underlying cause of the symptoms.