The Long Thoracic nerve is a branch of the brachial plexus that arises directly from the cervical nerve roots C5, C6, and C7. It lies dorsal to the spinal nerves and it innervates the serratus anterior. It is called the Long Thoracic Nerve because the nerve is long and it lies over the chest. The long thoracic nerve travels in a distal direction behind the brachial plexus between the anterior and middle scalene muscles. It also passes under the clavicle and over the first rib. The nerve runs along the midaxillary line for 22-24cm to reach the serratus anterior muscle. Due to the length of the nerve, it is susceptible to traction related injuries. Injury may occur due to axilla dissection or by aggressive retraction of the middle scalene muscle. If the nerve is injured, it can cause weakness or paralysis of the serratus anterior muscle which causes medial winging of the scapula.
The serratus anterior muscle pulls the scapula away from the midline and forward (scapular abduction). It also rotates the scapula upwards. The most important function of the serratus anterior is that it helps to stabilize the scapula so that the other muscles attached to the scapula can work properly.
With medial winging of the scapula, there will be a prominence of the scapular inferomedial edge with medial displacement and downward rotation. The position of the resting scapula is upwards and medial because the trapezius muscle dominates the motion of the scapula. If the trapezius is involved because of the accessory nerve then there will be lateral winging of the scapula so the longer thoracic is medial winging of the scapula.
When diagnosing injury of the long thoracic nerve, the patient will complain of dull shoulder aches, pain, and weakness in association with scapular winging. Especially when the arms push against resistance like you push against the wall. Medial winging of the scapula is checked by having the patient perform the wall push-up test for serratus anterior muscle weakness. This test may be useful for minor cases, but for more severe cases, the winging would be very apparent.
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