What injury results in winging of the scapula after mastectomy?

NORCET 3 - 2022 (Shift-1)

Applied Anatomy

Hard

Appeared in: NORCET 3 - 2022 (Shift-1)

Explanation

thoracic nerve injury, specifically referring to the long thoracic nerve.
The long thoracic nerve innervates the serratus anterior muscle, which is responsible for holding the scapula against the ribcage (protraction).
This nerve follows a long, superficial path along the chest wall, making it highly susceptible to injury during axillary lymph node dissection, a procedure often done with mastectomy.
Damage to this nerve leads to paralysis of the serratus anterior muscle, resulting in the characteristic 'winging' of the scapula, as seen in the image.

Option A: The medial scapular muscles (rhomboids and levator scapulae) are responsible for scapular retraction and elevation. Injury to them or their nerve supply (dorsal scapular nerve) causes a different, less dramatic form of scapular instability, not the classic winging seen here.
Option C: The triceps brachii muscle is located in the posterior compartment of the arm and its primary function is extension of the elbow joint. It has no direct role in stabilizing the scapula.
Option D: This is a close distractor. While the serratus anterior muscle is indeed the muscle that is non-functional, the primary injury during the surgical procedure is to the nerve that controls it. The muscle dysfunction is a secondary consequence of the nerve damage.

Visual 1: Anatomical Diagram - A diagram showing the course of the long thoracic nerve from the brachial plexus, down the lateral chest wall, to the serratus anterior muscle. This would help visualize its vulnerability during axillary surgery.
Visual 2: Flowchart - A simple flowchart illustrating the causal chain: Mastectomy → Long Thoracic Nerve Injury → Serratus Anterior Paralysis → Scapular Winging.

Clinical Relevance

Nursing practice connection: Safe nursing care depends on performing Etiology of Scapular Winging Post-Mastectomy in the correct sequence, documenting the action clearly, and monitoring for the expected response.
A key nursing role post-mastectomy is to assess for complications, including nerve damage. Observing for scapular winging during patient movement and reporting it is crucial for early intervention.
Patient education is vital. Nurses should instruct patients on signs of nerve injury and teach them to avoid heavy lifting or strenuous arm movements on the affected side until cleared by a doctor or physiotherapist.
What if the winging was present but the patient did not have a mastectomy? In that case, the nurse should inquire about other potential causes, such as heavy weightlifting, repetitive overhead arm movements, or direct trauma to the neck or chest wall, as these can also injure the long thoracic nerve.

How to Approach the Question

First, identify the key clinical sign in the question and image: 'winging of the scapula'.
Recall the primary muscle responsible for preventing scapular winging. This is the serratus anterior muscle, which protracts the scapula and holds it to the thoracic wall.
Next, recall the nerve that innervates the serratus anterior muscle. This is the long thoracic nerve.
Consider the clinical context: 'after mastectomy'. This procedure, especially with axillary dissection, puts the long thoracic nerve at high risk of injury.
Evaluate the options based on this chain of logic. 'Thoracic nerve injury' is the option that correctly identifies the primary cause (long thoracic nerve) in this specific clinical scenario.

Concept Tested & Keywords

Concept Tested: Etiology of Scapular Winging Post-Mastectomy
Stem keywords: injury, winging of the scapula, mastectomy
Lead-in keywords: What
Clinical cues: The image provided shows a classic presentation of scapular winging, which is a key diagnostic sign.

Ql7dANVo-b3A0Xck66xIEx