During hyperextension, the long head of triceps gets detached from which site?

Explanation

## Correct Answer: B. Infraglenoid tubercle The long head of triceps originates from the **infraglenoid tubercle** of the scapula, a bony prominence located just below the glenoid cavity. During hyperextension of the shoulder (forced backward movement of the arm), the long head of triceps is stretched maximally because it spans both the shoulder and elbow joints. This eccentric loading—combined with the mechanical disadvantage at the infraglenoid origin—makes the proximal attachment vulnerable to avulsion injury. The infraglenoid tubercle is the weakest point in the triceps chain because it is a small, non-articular bony process that bears the entire tensile load of the long head during hyperextension. In clinical practice, this injury occurs in contact sports (rugby, wrestling) or falls on an outstretched arm with the elbow extended. The detachment is an avulsion fracture rather than a simple soft-tissue tear, as the force is sufficient to pull bone away from the scapula. This is distinct from distal triceps ruptures at the olecranon, which occur with different mechanisms (direct trauma or chronic degeneration). ## Why the other options are wrong **A. Olecranon process** — This is the **distal** insertion of the triceps (all three heads), not the origin of the long head. Avulsion injuries at the olecranon occur with different mechanisms—direct blow to the posterior elbow or sudden forceful elbow flexion against resistance—not hyperextension of the shoulder. This is a common trap because students confuse the insertion with the origin. **C. Shaft of humerus** — The lateral and medial heads of triceps originate from the posterior shaft of the humerus, not the long head. Hyperextension primarily stresses the long head (which is biarticular), not the monoarticular heads. Shaft avulsions are rare and occur with different injury patterns. This option distracts by listing a legitimate triceps origin, but for the wrong head. **D. Supraglenoid tubercle** — The supraglenoid tubercle is the origin of the **long head of biceps**, not triceps. This is a classic NBE trap pairing two scapular tubercles to test anatomical precision. Students who confuse biceps with triceps or mix up the tubercles will select this. The supraglenoid location is superior to the glenoid, whereas the infraglenoid is inferior. ## High-Yield Facts - **Long head of triceps origin**: infraglenoid tubercle of scapula (biarticular muscle spanning shoulder and elbow). - **Hyperextension mechanism**: forced backward shoulder movement stretches long head maximally, causing avulsion at proximal attachment. - **Infraglenoid tubercle vulnerability**: small, non-articular bony process bears entire tensile load; weakest point in triceps chain. - **Avulsion vs. insertion rupture**: proximal avulsion (infraglenoid) occurs with hyperextension; distal rupture (olecranon) occurs with direct trauma or elbow flexion against resistance. - **Clinical context**: common in contact sports (rugby, wrestling) and falls on outstretched arm with elbow extended. ## Mnemonics **TRICEPS ORIGINS (3 heads)** **L**ong head = **L**ower tubercle (infraglenoid) | **L**ateral head = **L**ateral shaft | **M**edial head = **M**edial shaft. Remember: Long = Lower (infraglenoid is below glenoid). **SCAPULAR TUBERCLES (Biceps vs Triceps)** **Supra**glenoid = **Supra**-spinatus region = **Bi**ceps long head | **Infra**glenoid = **Infra**-spinatus region = **Tri**ceps long head. Mnemonic: Bi-Supra, Tri-Infra. ## NBE Trap NBE pairs the two scapular tubercles (supraglenoid and infraglenoid) to test whether students can distinguish biceps origin from triceps origin. Students who confuse the two muscles or forget the anatomical landmarks will incorrectly select supraglenoid. ## Clinical Pearl In Indian orthopaedic practice, long head triceps avulsion is often missed on initial presentation because patients may have only mild posterior shoulder pain and preserved elbow extension (lateral and medial heads compensate). MRI or ultrasound is essential to confirm infraglenoid avulsion before surgical repair, especially in young athletes presenting after contact sports injuries. _Reference: Robbins & Cotran Ch. 27 (Musculoskeletal System); Bailey & Love Ch. 52 (Shoulder and Upper Arm)_