Winging of scapula is caused due to injury to which of the following parts?

AIIMS Bhuvneshwar NO- 2018

Applied Anatomy

Easy

Appeared in: AIIMS Bhuvneshwar NO- 2018

Explanation

Winging of the scapula, as shown in the image, is the classic sign of serratus anterior muscle paralysis.
The serratus anterior muscle is responsible for protracting the scapula and holding it against the rib cage.
This muscle is exclusively innervated by the long thoracic nerve of Bell (C5, C6, C7).
Therefore, an injury to the long thoracic nerve leads to paralysis of the serratus anterior and subsequent winging of the scapula.

Option A: The thoracodorsal nerve innervates the latissimus dorsi muscle. Injury to this nerve weakens shoulder adduction and extension but does not cause the medial winging of the scapula seen in the image.
Option C: The ulnar nerve primarily supplies the intrinsic muscles of the hand and some forearm flexors. Its injury results in hand deformities like 'claw hand' and sensory deficits, which are unrelated to scapular movement.
Option D: The dorsal scapular nerve supplies the rhomboid muscles, which retract the scapula. While its injury can cause some scapular instability, it does not produce the classic medial winging associated with serratus anterior palsy.

Visual 1: Anatomical Diagram - A diagram illustrating the path of the long thoracic nerve from the brachial plexus down the lateral chest wall to innervate the digitations of the serratus anterior muscle.
Visual 2: Action Illustration - An image comparing a normal person and a person with a winged scapula both performing the 'wall push test'. This highlights the prominence of the scapula under resistance.
Visual 3: Flowchart - A flowchart showing: Injury (e.g., trauma, surgery) → Long Thoracic Nerve Damage → Serratus Anterior Paralysis → Loss of Scapular Stabilization → Medial Winging of Scapula.

Clinical Relevance

Nursing practice connection: Knowing Etiology of scapular winging based on nerve injury helps nurses interpret findings accurately and avoid errors in routine assessment, medication administration, and patient teaching.
Nurses must be vigilant for scapular winging in post-operative patients, especially after procedures in the axilla, such as mastectomy with lymph node dissection, or after chest tube insertion, as the long thoracic nerve is vulnerable.
Assessment involves having the patient push against a wall with outstretched arms and observing for any prominence or 'winging' of the scapula.
Early identification is crucial. If winging is noted, the nurse should document the finding, inform the physician, and anticipate a referral to physical therapy to prevent long-term shoulder dysfunction and pain.

How to Approach the Question

Step 1: Analyze the image to identify the clinical sign. The image clearly shows the medial border of the scapula protruding from the back, which is known as 'winging of the scapula'.
Step 2: Recall the primary muscle responsible for preventing this sign. The serratus anterior muscle holds the scapula against the chest wall.
Step 3: Identify the nerve that innervates this specific muscle. The long thoracic nerve is the motor nerve to the serratus anterior.
Step 4: Correlate the nerve with the given options. The 'Long thoracic nerve of Bell' is listed as an option.
Step 5: Eliminate the other options by recalling the functions of the other nerves listed. The thoracodorsal, ulnar, and dorsal scapular nerves control different muscle groups and result in different clinical deficits.

Concept Tested & Keywords

Concept Tested: Etiology of scapular winging based on nerve injury.
Stem keywords: Winging of scapula, injury, nerve
Lead-in keywords: caused due to
Clinical cues: The visual presentation of a winged scapula is a key clinical sign.

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