Winging of scapula is due to paralysis of (FMGE Dec 2018)
First, the core concept. Winging of the scapula is a clinical sign, so the underlying principle here is the anatomy and function of the muscles involved in stabilizing the scapula. The main muscles are the serratus anterior and the trapezius. The question is about which muscle's paralysis causes this.
The correct answer is likely the serratus anterior because it's the primary stabilizer. The long thoracic nerve innervates it, and damage there leads to winging. The trapezius is innervated by the spinal accessory nerve, and its paralysis leads to a different type of scapular winging, usually more noticeable when pushing against resistance.
Now, the wrong options. Let's assume the options are common distractors. For example, if one option is the rhomboids, they might be incorrect because the rhomboids retract the scapula but aren't the main stabilizers. The pectoralis minor could be another distractor, but it's more involved in pulling the scapula downward, not stabilization. The levator scapulae is involved in elevation, so its paralysis wouldn't cause winging.
The clinical pearl here is to remember the nerves involved. Serratus anterior and long thoracic nerve are key for medial border stabilization, while trapezius and spinal accessory nerve affect the upper part. Also, differentiating between the two types of winging based on the position of the arm.
I need to structure the explanation with the required sections, making sure each part is concise and covers all points. Check for medical accuracy, like the correct nerves and muscles. Also, keep the language clear and suitable for a postgraduate student. Avoid any markdown except the specified bold and line breaks. Let me verify each section again to ensure nothing's missed.
**Core Concept**
Winging of the scapula results from dysfunction of the muscles responsible for stabilizing the scapula against the thoracic wall. The **serratus anterior** (innervated by the long thoracic nerve) and **trapezius** (innervated by the spinal accessory nerve) are the primary stabilizers; their paralysis leads to scapular winging during arm elevation or abduction.
**Why the Correct Answer is Right**
The **serratus anterior** is the most common cause of scapular winging. It protracts the scapula and prevents medial border winging by pulling the scapula forward against the ribcage. Paralysis (e.g., due to long thoracic nerve injury) causes the medial border to "wing" when the arm is raised. The trapezius, though important for upward rotation, typically causes winging at the superomedial angle, often secondary to spinal accessory nerve palsy. However, serratus anterior palsy is more commonly tested in exams.
**Why Each Wrong Option is Incorrect**
**Option A:** Rhomboids major/minor – These retract the scapula but are not primary stabilizers; their paralysis causes minimal winging.
**Option B:** Pectoralis minor – Involved in downward rotation, not scapular stabilization.
**Option C:** Levator scapula