A 20-year-old boy got severe pain due to hyperextension of shoulder while training in the gym. The trainer expected a probable disruption of the structure marked “A” in the image below. Which site is affected?
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Long head of triceps originates from the infraglenoid tubercle; long head of biceps originates from the supraglenoid tubercle.
Step 1: Understanding the Question:
The injury occurred during shoulder hyperextension.
The question asks for the bony attachment of the muscle marked "A", which is implied to be the long head of the triceps. Step 2: Detailed Explanation:
Mechanism of Injury: Forceful hyperextension of the glenohumeral joint stretches the structures on the inferior and anterior aspects of the joint. The long head of the triceps brachii is an extensor of the shoulder and is heavily stressed in this position.
Anatomy of the Triceps Brachii: The triceps muscle has three origins. The lateral and medial heads originate from the posterior humerus.
The Long Head of the Triceps is unique because it originates from the scapula, specifically the infraglenoid tubercle.
Differentiating from the Biceps: The long head of the \textit{biceps} originates from the supraglenoid tubercle. Because the biceps is a shoulder flexor, it would be more prone to injury during hyperflexion or distraction, rather than the hyperextension scenario described here.
Analyzing Options: The "infraglenoid tubercle" is the only option that correctly describes the scapular origin of the triceps long head.
Clinical Correlation: Avulsion or strain at the infraglenoid tubercle causes pain in the axillary region and posterior shoulder, worsened by shoulder extension or elbow extension.
Step 3: Final Answer:
The structure "A" (long head of triceps) originates from the infraglenoid tubercle of the scapula.
