What nerve injury causes winging of the scapula after a mastectomy?

Winging of the Scapula After Mastectomy: Nerve Injury Identification

The long thoracic nerve injury is the cause of winging of the scapula after mastectomy. This corresponds to answer choice (c) in the multiple-choice question.

Anatomical Basis for Scapular Winging

The long thoracic nerve innervates the serratus anterior muscle, which is crucial for proper scapular positioning and function. When this nerve is damaged:

• The serratus anterior muscle becomes paralyzed, unable to hold the medial border of the scapula against the thoracic wall
• This results in the characteristic "winging" appearance where the medial border of the scapula protrudes posteriorly, especially when pushing forward with the arms

Mechanism of Injury During Mastectomy

During mastectomy procedures, the long thoracic nerve is vulnerable to injury due to:

• Its anatomical course along the lateral chest wall, making it susceptible during axillary dissection 1
• The nerve runs superficially along the serratus anterior muscle, where it can be damaged during surgical manipulation
• Traction injuries can occur when excessive pulling is applied to the axillary tissues

Differential Diagnosis of Nerve Injuries

The other nerve options in the question can be ruled out for the following reasons:

1. Medial and lateral pectoral nerves (options a and b):

   • These nerves innervate the pectoral muscles
   • Injury would result in weakness of the anterior chest wall muscles, not scapular winging
   • While commonly encountered during mastectomy, their injury does not cause the described presentation

2. Thoracodorsal nerve (option d):

   • Innervates the latissimus dorsi muscle
   • Injury would cause weakness in shoulder extension and internal rotation
   • Should be preserved during axillary dissection as noted in surgical guidelines 1

3. Intercostal-brachial nerve (option e):

   • Primarily sensory in function
   • Injury causes numbness in the upper medial arm
   • Does not control any muscles responsible for scapular positioning

Clinical Significance and Management

Identification and preservation of the long thoracic nerve during mastectomy is critical:

• Surgical guidelines specifically mention that "the thoracodorsal and long thoracic nerves should be preserved" during axillary dissection 1
• Winging of the scapula can significantly impact quality of life through:
  • Pain and discomfort in the shoulder region
  • Limited range of motion
  • Difficulty with overhead activities
  • Cosmetic deformity

Treatment Options for Long Thoracic Nerve Injury

If long thoracic nerve injury occurs, treatment options include:

• Conservative management with physical therapy for mild cases
• Neurolysis and decompression of the long thoracic nerve, which has shown excellent results with 98% improvement in appropriate cases 2
• In chronic cases unresponsive to other treatments, muscle transfer procedures may be considered

Prevention

To prevent long thoracic nerve injury during mastectomy:

• Careful identification of anatomical structures during axillary dissection
• Separate breast and axillary incisions to improve visualization 1
• Avoidance of excessive traction on axillary tissues
• Preservation of all identified nerves in the surgical field

Understanding the anatomical basis of scapular winging and recognizing the long thoracic nerve as the critical structure involved is essential for both preventing this complication and managing it appropriately when it occurs.