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AN8.1-4 | Features of individual bones (Upper Limb) — Gate Quiz
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The surgical neck of the humerus is the site of fracture that most commonly injures which nerve?
Correct! The axillary nerve winds around the surgical neck of the humerus. A fracture at the surgical neck can injure the axillary nerve, causing deltoid paralysis and loss of sensation over the regimental badge area.
Surgical neck fracture → axillary nerve injury → deltoid paralysis + loss of skin sensation over upper lateral arm ('regimental badge area'). Midshaft fracture → radial nerve injury (spiral groove) → wrist drop.
Incorrect. The axillary nerve is closely related to the surgical neck of the humerus. Radial nerve is injured at the midshaft (spiral groove).
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Which bone forms the bony point of the elbow (olecranon)?
Correct! The olecranon is a process of the ulna that projects posteriorly and forms the bony point of the elbow. It fits into the olecranon fossa of the humerus during full extension.
The ulna has two important proximal processes: (1) Olecranon — the posterior bony point of the elbow. (2) Coronoid process — the anterior projection. Between them is the trochlear notch which articulates with the trochlea of the humerus.
Incorrect. The olecranon is part of the ulna. It is the proximal posterior projection of the ulna that forms the point of the elbow.
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Which styloid process extends more distally in the anatomical position and can be felt on the lateral side of the wrist?
Correct! The radial styloid process extends more distally than the ulnar styloid (approximately 1 cm lower) and is palpable on the lateral (thumb) side of the wrist. This fact is used to determine forearm rotation and detect Colles' fracture displacement.
Radial styloid: lateral/thumb side, more distal, palpable as a bony prominence. Ulnar styloid: medial/little finger side. In Colles' fracture, the radial styloid may be displaced proximally, reversing the normal relationship.
Incorrect. The radial styloid is more distal (lower) and on the lateral (thumb/radial) side. The ulnar styloid is on the medial (little finger/ulnar) side and is less prominent.
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How many carpal bones are present in the wrist?
Correct! There are 8 carpal bones arranged in two rows of four. Proximal row: scaphoid, lunate, triquetrum, pisiform. Distal row: trapezium, trapezoid, capitate, hamate.
8 carpal bones: Proximal row (lateral to medial) — Scaphoid, Lunate, Triquetrum, Pisiform. Distal row — Trapezium, Trapezoid, Capitate, Hamate. The scaphoid is the most commonly fractured carpal bone (fall on outstretched hand).
Incorrect. There are 8 carpal bones in two rows of 4 each. Mnemonic: 'Some Lovers Try Positions That They Can't Handle' (Scaphoid, Lunate, Triquetrum, Pisiform, Trapezium, Trapezoid, Capitate, Hamate).
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A 22-year-old medical student in Mangalore falls on his outstretched hand. X-ray appears normal but there is tenderness in the anatomical snuffbox. The most likely injured bone is:
Correct! The scaphoid (navicular) bone lies in the anatomical snuffbox and is the most commonly fractured carpal bone. X-rays may appear normal acutely; MRI or CT confirms the fracture. Risk of avascular necrosis is significant due to its blood supply entering distally.
Anatomical snuffbox boundaries: Laterally — Abductor pollicis longus + Extensor pollicis brevis; Medially — Extensor pollicis longus; Floor — Scaphoid + Trapezium. Scaphoid fracture: tenderness here + FOOSH → suspect scaphoid fracture even with normal X-ray.
Incorrect. Tenderness in the anatomical snuffbox + normal X-ray after FOOSH is the classic presentation of a scaphoid fracture. Treat as scaphoid fracture until proven otherwise.
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The thumb (first digit) has how many phalanges?
Correct! The thumb has only 2 phalanges: a proximal and a distal phalanx. It lacks a middle phalanx. Digits 2–5 each have 3 phalanges (proximal, middle, distal).
Digits 1 (thumb): 2 phalanges — proximal + distal (no middle). Digits 2–5: 3 phalanges each — proximal, middle, distal. Total phalanges in hand = 2 + (4×3) = 14.
Incorrect. The thumb has 2 phalanges (proximal + distal) — no middle phalanx. This gives it a wider range of opposition movement.
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The greater tubercle of the humerus is the insertion point for which group of rotator cuff muscles?
Correct! The greater tubercle has three facets for the three rotator cuff muscles: (1) Supraspinatus (superior facet), (2) Infraspinatus (middle facet), (3) Teres minor (inferior facet). Subscapularis inserts into the lesser tubercle.
Rotator cuff (SITS): Supraspinatus (abducts), Infraspinatus (lateral rotation), Teres minor (lateral rotation), Subscapularis (medial rotation). SIT → greater tubercle. Subscapularis → lesser tubercle.
Incorrect. Greater tubercle: SIT muscles (Supraspinatus, Infraspinatus, Teres minor). Lesser tubercle: Subscapularis. Mnemonic: 'SIT on the greater tubercle.'
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The long head of biceps brachii tendon passes through which groove on the humerus?
Correct! The intertubercular (bicipital) groove lies between the greater and lesser tubercles of the humerus. The long head of biceps brachii tendon passes through this groove, held in place by the transverse humeral ligament.
Intertubercular groove contents (lateral to medial): Greater tubercle → Latissimus dorsi (lateral lip), Biceps long head (floor), Pectoralis major (medial lip) → Lesser tubercle. The groove is bridged by the transverse humeral ligament.
Incorrect. The long head of biceps brachii runs in the intertubercular (bicipital) sulcus between the two tubercles of the humerus.
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A cyclist in Bengaluru fractures the hook of hamate after falling on his outstretched hand. Which motor deficit is most likely?
Correct! The ulnar nerve passes through Guyon's canal (ulnar tunnel) between the pisiform and the hook of hamate. A fracture of the hook of hamate can injure the deep branch of the ulnar nerve, causing weakness of the hypothenar muscles and interossei (ring and little finger intrinsics).
Hook of hamate fracture → Guyon's canal compression → ulnar nerve injury → hypothenar + interossei weakness + ring/little finger clawing. Scaphoid fracture = most common carpal fracture; hook of hamate = second most common (cyclists, golfers).
Incorrect. The hook of hamate is adjacent to Guyon's canal which transmits the ulnar nerve. Fracture here typically injures the deep branch of the ulnar nerve.
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The clavicle is unique among long bones because it:
Correct! The clavicle is the only long bone in the body that ossifies primarily by intramembranous ossification (not endochondral ossification). It is also the first bone to ossify in the embryo (at 5–6 weeks of intrauterine life).
Clavicle: (1) Only long bone ossifying by intramembranous ossification. (2) First bone to ossify (5–6 weeks IUL). (3) Last long bone to complete ossification (medial epiphysis fuses at ~25 years). (4) Most frequently fractured bone in the body.
Incorrect. The clavicle is unique because it undergoes intramembranous ossification, unlike other long bones which ossify by endochondral ossification. It is also the first bone to ossify in the body.
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