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AN13.1-8 | General Features, Joints, radiographs & surface marking (Upper Limb) — Gate Quiz
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The glenohumeral (shoulder) joint is classified as which type of synovial joint?
Correct! The glenohumeral joint is a ball and socket (spheroidal) joint where the rounded head of the humerus articulates with the shallow glenoid fossa of the scapula. This allows movement in all planes (multiaxial) — flexion/extension, abduction/adduction, and medial/lateral rotation.
Joint types: Ball & socket (shoulder, hip) — multiaxial. Hinge (elbow, ankle) — uniaxial. Condylar (wrist, MCP) — biaxial. Saddle (1st carpometacarpal) — biaxial. Pivot (proximal radioulnar) — uniaxial. The shoulder sacrifices stability for mobility.
Incorrect. The shoulder is a ball and socket joint — the most mobile type of synovial joint. The hinge joint (e.g., elbow) allows only flexion/extension.
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The elbow joint is a compound joint. Which three articulations make up the elbow joint?
Correct! The elbow joint is a compound joint enclosed within a single capsule comprising three articulations: (1) Humeroulnar — hinge joint for flexion/extension; (2) Humeroradial — ball and socket component; (3) Superior (proximal) radioulnar — pivot joint for pronation/supination.
Elbow joint: Humeroulnar (trochlea–trochlear notch) + Humeroradial (capitulum–radial head) + Proximal radioulnar (radial notch–radial head + annular ligament). Enclosed in one capsule. The inferior radioulnar joint is at the wrist, not the elbow.
Incorrect. Elbow = humeroulnar + humeroradial + superior (proximal) radioulnar joints. The inferior radioulnar joint is at the wrist.
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A 65-year-old woman falls on an outstretched hand. Her wrist radiograph shows a distal radius fracture with dorsal angulation of the distal fragment. This is a classic description of:
Correct! Colles' fracture is a fracture of the distal radius (within 2.5 cm of the wrist) with dorsal displacement and angulation of the distal fragment, producing the 'dinner fork deformity.' It is the most common fracture in elderly women due to osteoporosis.
Colles' fracture: Distal radius fracture + dorsal displacement + radial shortening. 'Dinner fork deformity.' Most common fracture in post-menopausal women. Smith's fracture: same site but palmar/volar displacement. Galeazzi: radial shaft + distal radioulnar dislocation. Monteggia: proximal ulna + radial head dislocation.
Incorrect. Colles' fracture: distal radius + dorsal displacement = dinner fork deformity. Smith's fracture: distal radius + volar (palmar) displacement = reverse dinner fork/garden spade deformity.
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The carrying angle of the elbow is normally greater in women than men. What is the approximate normal range for the carrying angle?
Correct! The normal carrying angle of the elbow is approximately 10–15° of valgus (lateral deviation of the forearm). It is slightly greater in women (approximately 13–16°) compared to men (approximately 11–14°). It is the angle between the long axis of the humerus and the forearm in the anatomical position.
Carrying angle: The valgus angle at the elbow in the anatomical position. Men ~11°, Women ~13°. Abnormal: Cubitus valgus (>15° — tardy ulnar nerve palsy risk), Cubitus varus (<normal — gunstock deformity after supracondylar fracture). The carrying angle disappears in full elbow flexion.
Incorrect. Normal carrying angle: 10–15°. Greater in women. Cubitus valgus: >15° (angle exceeds normal). Cubitus varus ('gunstock deformity'): angle less than normal (varus), typically due to malunited supracondylar fracture.
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The anatomical landmark for locating the wrist (radiocarpal) joint on the dorsum of the hand is the proximal skin crease of the wrist. Deep to this, the joint space is located at the level of:
Correct! The wrist (radiocarpal) joint lies approximately at the level of Lister's tubercle on the dorsum of the radius — the proximal wrist crease corresponds to the level of the radiocarpal joint. The styloid processes are distal to the joint.
Radiocarpal joint: between distal radius/articular disc (proximal) and proximal row of carpals (distal). Surface: dorsal wrist crease = level of joint. Lister's tubercle marks the dorsal midline at joint level. The radial styloid is ~1 cm more distal than the ulnar styloid.
Incorrect. The radiocarpal joint is at the level of Lister's tubercle (dorsal aspect). The styloid processes are distal to the joint line, not at it.
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The brachial artery can be palpated along a surface line from which landmark to which?
Correct! The surface marking of the brachial artery is a line drawn from the coracoid process (when the arm is abducted 60°) to the midpoint of the cubital fossa (where it divides). This line runs along the medial aspect of the arm.
Surface marking for brachial artery (arm abducted 60°): Coracoid process → midpoint of cubital fossa. The artery lies medial to the biceps tendon in the cubital fossa. Clinical: blood pressure auscultation site, venous access for cardiac catheterization, brachial artery cannulation.
Incorrect. Brachial artery surface marking: coracoid process → midpoint of the cubital fossa. The artery runs in the medial bicipital groove.
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On an AP radiograph of the elbow, three bony landmarks form an equilateral triangle in the normal elbow when the joint is flexed to 90°. Loss of this triangle suggests a supracondylar fracture. These three landmarks are:
Correct! When the elbow is flexed to 90°, the medial epicondyle, lateral epicondyle, and the tip of the olecranon form an equilateral triangle on the posterior view (Hueter's triangle). In a supracondylar fracture, this triangle is disrupted. On the AP view, the medial and lateral epicondyles and olecranon form a straight line in extension.
Hueter's triangle: In 90° elbow flexion — medial epicondyle, lateral epicondyle, and olecranon tip form an equilateral triangle. In full extension, these form a straight line. Clinical: Disrupted in supracondylar fracture or elbow dislocation; used to assess elbow joint integrity on plain radiograph.
Incorrect. Hueter's triangle: medial epicondyle + lateral epicondyle + tip of olecranon (90° flexion). Disruption suggests supracondylar fracture.
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A child presents with a supracondylar fracture of the humerus. On examination, he is unable to make the 'OK sign' (circular ring with thumb and index finger). The most likely nerve injury is:
Correct! The anterior interosseous nerve (AIN) — the deep motor branch of the median nerve — is the nerve most commonly injured in supracondylar fractures. AIN supplies FPL, lateral FDP (index/middle FDP), and pronator quadratus. Loss of AIN = inability to make the OK sign (cannot flex IP of thumb + DIP of index finger).
Anterior interosseous nerve (AIN) injury: Cannot flex IP joint of thumb (FPL) + DIP joint of index finger (FDP lateral head). Cannot make OK sign. No sensory loss (purely motor nerve). Test: ask patient to make OK sign — if cannot, AIN injury. Most common nerve injured in supracondylar fractures.
Incorrect. AIN injury = cannot make OK sign. The AIN is the most commonly injured nerve in supracondylar fractures. The radial nerve may also be injured but causes wrist drop, not inability to make the OK sign.
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A young man presents with an injury where the proximal third of the ulna is fractured and the radial head is dislocated. This combination is called:
Correct! The Monteggia fracture-dislocation consists of a fracture of the proximal third of the ulna combined with dislocation of the radial head at the proximal radioulnar joint. The deep branch of the radial nerve (posterior interosseous nerve) is at risk.
Forearm fracture-dislocations: Monteggia = ulna fracture + proximal radial head dislocation. Galeazzi = radius fracture + distal radioulnar dislocation. Mnemonic: 'MUGR' = Monteggia Ulna Galeazzi Radius. Both require ORIF — simple immobilization fails.
Incorrect. Monteggia = proximal ulna fracture + radial head dislocation. Galeazzi = radial shaft fracture + distal radioulnar joint dislocation. These are reverse lesions in terms of which bone fractures.
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A child develops a 'gunstock deformity' after a poorly reduced supracondylar fracture. This deformity involves which abnormality of the carrying angle?
Correct! Cubitus varus (gunstock deformity) means the carrying angle is decreased or reversed (varus = the forearm deviates medially). It is the most common complication of a malunited supracondylar fracture. The elbow looks like the stock of a gun when viewed from the front.
Carrying angle deformities: Cubitus valgus (>15°): increased angle, risk of tardy ulnar nerve palsy. Cubitus varus (gunstock): decreased/reversed angle, most common complication of malunited supracondylar fracture in children. Neither causes immediate nerve palsy, but cubitus valgus can cause delayed ulnar nerve injury.
Incorrect. Gunstock deformity = cubitus varus = decreased/reversed carrying angle. Cubitus valgus = increased carrying angle (>15°).
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