A winged scapula is a condition where the shoulder blade, or scapula, visibly protrudes from the back, rather than lying flat against the chest wall. This abnormal positioning occurs when the muscles responsible for anchoring and controlling the scapula become weakened or paralyzed due to damage to their specific supply nerves. The resulting imbalance in the shoulder’s muscular system disrupts the smooth, coordinated movement of the arm and shoulder, often leading to pain and reduced range of motion. Understanding which nerve has been compromised is the first step in diagnosing and treating this physical finding.
The Primary Nerve and Muscle Responsible
The nerve most commonly implicated in scapular winging is the Long Thoracic Nerve (LTN), damage to which causes paralysis of the Serratus Anterior muscle. This large muscle originates on the first eight or nine ribs and inserts along the medial border of the scapula. Its primary role is to protract the scapula, pulling it forward around the chest wall, and holding it firmly against the rib cage, preventing winging.
When the Long Thoracic Nerve is injured, the Serratus Anterior can no longer perform its stabilizing function. Its paralysis causes the most classic and pronounced form of the condition, known as medial winging, and impairs the upward rotation necessary to raise the arm above shoulder height.
In medial winging, the inner edge of the shoulder blade, particularly the inferior angle, becomes prominent. The loss of the Serratus Anterior’s forward pull allows the opposing Rhomboid muscles to pull the scapula backward and inward toward the spine. This protrusion is often most noticeable when the affected person pushes against a wall or attempts to lift their arm forward.
Identifying Other Nerve-Muscle Combinations
While the Long Thoracic Nerve is the most frequent culprit, a winged scapula can also result from injury to two other nerves, creating different visual presentations. The Dorsal Scapular Nerve supplies the Rhomboid muscles, which retract the scapula and pull it toward the spine. Injury to this nerve causes Rhomboid weakness, resulting in the scapula resting farther away from the midline of the back.
This presentation is typically more subtle than medial winging. The third nerve involved is the Spinal Accessory Nerve, which controls the Trapezius muscle. The Trapezius elevates, retracts, and depresses the scapula, contributing to shoulder stability.
Damage to the Spinal Accessory Nerve, often due to its superficial course in the neck, leads to Trapezius muscle paralysis. The resulting winging causes the shoulder to droop, and the scapula is translated outward and rotated downward. The difference in the specific nerve and muscle affected determines the direction in which the scapula protrudes.
Common Mechanisms of Nerve Damage
The nerves responsible for stabilizing the scapula are vulnerable due to their anatomical paths. The Long Thoracic Nerve is susceptible to blunt trauma, such as a direct blow or a fall on the shoulder. Its long, relatively superficial course also makes it prone to traction injuries from sudden or repetitive overstretching, common in sports involving overhead arm movements like pitching or weightlifting.
Iatrogenic injury, or damage during medical procedures, is another recognized mechanism. The Long Thoracic Nerve can be injured during surgeries on the chest wall or axilla, including mastectomy or lymph node dissection. The Spinal Accessory Nerve is highly vulnerable during neck surgeries, such as lymph node biopsies, due to its superficial location.
Nerve damage can also result from non-traumatic causes, including viral illnesses that trigger an inflammatory condition known as neuralgic amyotrophy. Even prolonged or awkward body positioning, such as during general anesthesia or carrying a heavy backpack, can compress or stretch these nerves.
Diagnosis and Non-Surgical Rehabilitation
Diagnosis of a winged scapula is made through a physical examination and visual assessment. A doctor will ask the patient to perform specific movements, such as the wall push-up test, which accentuates the winging and helps identify the weakened muscle. Medial winging becomes more apparent when the patient pushes against a wall, while lateral winging is often visible during active arm abduction.
To confirm the specific nerve involvement and assess the extent of the damage, electrodiagnostic studies like electromyography (EMG) and nerve conduction studies (NCS) are utilized. These tests measure the electrical activity of the muscles and the speed of signal transmission along the nerve, providing objective evidence of nerve injury or paralysis.
Non-surgical rehabilitation is the standard initial approach, as many cases of Long Thoracic Nerve palsy spontaneously improve. Conservative management focuses on physical therapy, including targeted exercises to strengthen surrounding shoulder girdle muscles to compensate for the weakness. Bracing or supportive slings may also be used to stabilize the scapula and prevent further stretching of the damaged nerve while it recovers. Complete nerve recovery often ranges from six months up to two years.