What is the consequence of a long thoracic nerve injury?

A long thoracic nerve injury primarily affects the serratus anterior muscle, which is crucial for proper scapular function. The serratus anterior is responsible for holding the scapula against the thorax and allowing for upward rotation during arm elevation. When the long thoracic nerve is compromised, it causes weakness in the serratus anterior, leading to a characteristic sign known as scapular winging. This occurs because the scapula is no longer stabilized against the rib cage, resulting in the scapula protruding away from the back during shoulder movement.

Understanding this mechanism highlights the significance of the long thoracic nerve in upper extremity movements, specifically how it contributes to shoulder stability and functionality. The presence of scapular winging can often be visually observed during physical examination when the patient is asked to push against a wall or perform similar activities, further underscoring the impact of this nerve injury.