Upper Limb — MCQs

Upper Limb Indian Medical PG Practice Questions and MCQs

Question 431: The axis of abduction and adduction of digits passes through the center of which metacarpal bone?

A. 2nd metacarpal
B. 3rd metacarpal (Correct Answer)
C. 4th metacarpal
D. 5th metacarpal

Explanation: ### Explanation **1. Why the 3rd Metacarpal is Correct:** In the hand, the functional axis for movements of the fingers (digits 2–5) is defined by the **3rd digit (middle finger)** and its corresponding **3rd metacarpal**. * **Abduction** is defined as movement away from this central axis. * **Adduction** is defined as movement toward this axis. Because the 3rd digit *is* the axis, it can abduct to both the radial and ulnar sides (via the two dorsal interossei attached to it) but cannot technically "adduct" in the same way other fingers do, as it is already at the midline. **2. Why Other Options are Incorrect:** * **2nd Metacarpal (Index Finger):** This digit abducts away from the 3rd digit (radially) and adducts toward it. It serves as a boundary but not the reference axis. * **4th and 5th Metacarpals (Ring and Little Fingers):** These digits abduct away from the 3rd digit (ulnarly) and adduct toward it. The 5th digit has its own specific abductor (Abductor digiti minimi), but the reference point remains the 3rd metacarpal. **3. High-Yield Clinical Pearls for NEET-PG:** * **Muscle Mnemonics:** * **DAB:** **D**orsal interossei **AB**duct (4 muscles). * **PAD:** **P**almar interossei **AD**duct (3 muscles; the 3rd digit lacks a palmar interosseous because it is the axis). * **Nerve Supply:** All interossei (DAB and PAD) are supplied by the **Deep branch of the Ulnar Nerve (C8, T1)** [1]. * **Thumb Exception:** The axis for the thumb is different; its abduction/adduction occurs in a plane perpendicular to the palm (at the 1st CMC joint). * **Foot Comparison:** In the foot, the axis of abduction/adduction passes through the **2nd toe/metacarpal**, not the 3rd. This is a frequent point of confusion in exams.

Question 432: What nerve innervates the short head of the biceps brachii?

A. Musculocutaneous nerve (Correct Answer)
B. Radial nerve
C. Axillary nerve
D. Median nerve

Explanation: The **Musculocutaneous nerve (C5–C7)** is the primary nerve of the anterior compartment of the arm. It arises from the lateral cord of the brachial plexus and pierces the coracobrachialis muscle. It provides motor innervation to all three muscles in this compartment: the **Coracobrachialis**, the **Brachialis** (along with the radial nerve), and both the long and short heads of the **Biceps Brachii**. Therefore, Option A is correct. **Analysis of Incorrect Options:** * **B. Radial Nerve:** Primarily innervates the posterior compartment of the arm (Triceps brachii) and the forearm extensors. While it provides a small sensory/proprioceptive branch to the lateral part of the Brachialis, it does not supply the Biceps. * **C. Axillary Nerve:** Innervates the Deltoid and Teres minor muscles. It does not extend into the anterior compartment of the arm. * **D. Median Nerve:** While it travels through the arm, it gives off **no motor branches** in the arm. Its motor function begins in the forearm (flexor compartment) and the hand. **High-Yield NEET-PG Pearls:** 1. **The "BBC" Nerve:** A common mnemonic for the musculocutaneous nerve distribution is **B**iceps, **B**rachialis, and **C**oracobrachialis. 2. **Sensory Continuation:** After supplying the muscles, the musculocutaneous nerve continues as the **Lateral Cutaneous Nerve of the Forearm**, supplying the skin of the lateral forearm. 3. **Biceps Reflex:** Testing the biceps reflex (C5–C6) evaluates the integrity of the musculocutaneous nerve. 4. **Injury:** Damage to this nerve results in weak elbow flexion and weak forearm supination (though the supinator muscle remains intact via the radial nerve).

Question 433: The axillary nerve is a branch of which part of the brachial plexus?

A. Trunk
B. Medial cord
C. Lateral cord
D. Posterior cord (Correct Answer)

Explanation: The axillary nerve (C5, C6) arises directly from the posterior cord of the brachial plexus. The posterior cord is formed by the union of the posterior divisions of all three trunks (upper, middle, and lower), representing the dorsal aspect of the limb's nerve supply. **Why the Posterior Cord is correct:** The posterior cord gives off five branches, easily remembered by the mnemonic **ULTRA**: * **U**pper subscapular nerve * **L**ower subscapular nerve * **T**horacodorsal nerve [1] * **R**adial nerve (Terminal branch) * **A**xillary nerve (Terminal branch) **Why other options are incorrect:** * **Trunk:** The trunks (Upper, Middle, Lower) primarily give off branches like the suprascapular nerve and nerve to subclavius (from the upper trunk), but not the axillary nerve. * **Medial Cord:** This cord gives rise to the ulnar nerve, medial cutaneous nerves of the arm/forearm, and the medial head of the median nerve. * **Lateral Cord:** This cord gives rise to the musculocutaneous nerve, lateral pectoral nerve, and the lateral head of the median nerve. **Clinical Pearls for NEET-PG:** 1. **Site of Injury:** The axillary nerve is most commonly injured during **fractures of the surgical neck of the humerus** or **anterior dislocation of the shoulder joint**. 2. **Clinical Presentation:** Injury leads to paralysis of the **deltoid** (loss of abduction from 15–90 degrees) and **teres minor**, along with sensory loss over the "regimental badge area" (lower half of the deltoid). 3. **Quadrangular Space:** The axillary nerve passes through this space along with the posterior circumflex humeral artery.

Question 434: All of the following are true statements about the joints of the upper limb EXCEPT:

A. Acromioclavicular joint - Plane synovial joint
B. Shoulder joint - Ball and socket joint
C. Sternoclavicular joint - Hinge joint (Correct Answer)
D. Intercarpal and midcarpal joints - Plane synovial joint

Explanation: ### Explanation The **Sternoclavicular (SC) joint** is anatomically and functionally a **Saddle-type synovial joint**, not a hinge joint. It is unique because it is the only bony attachment between the upper limb and the axial skeleton. Despite being a saddle joint, it functions almost like a ball-and-socket joint due to the presence of a fibrocartilaginous articular disc that divides the joint cavity, allowing for multi-axial movement (elevation/depression, protraction/retraction, and rotation). **Analysis of Options:** * **A. Acromioclavicular joint:** This is correctly identified as a **Plane synovial joint**. It allows gliding movements between the acromion of the scapula and the lateral end of the clavicle, facilitating scapular rotation during arm abduction. * **B. Shoulder joint:** This is a classic **Ball and socket joint** (Glenohumeral joint). It provides the greatest range of motion of any joint in the body at the expense of stability. * **D. Intercarpal and midcarpal joints:** These are **Plane synovial joints**. They allow small gliding movements between individual carpal bones, which contribute to the overall flexibility of the wrist complex. **NEET-PG High-Yield Pearls:** * **Sternoclavicular Joint:** It is the only joint in the upper limb that contains a complete **intra-articular disc**, which acts as a shock absorber and prevents medial displacement of the clavicle. * **Hinge Joints in Upper Limb:** The primary examples are the **Humeroulnar (Elbow) joint** and the **Interphalangeal joints**. * **Pivot Joints:** The **Proximal and Distal Radioulnar joints** are pivot joints, essential for supination and pronation. * **Ellipsoid Joint:** The **Wrist (Radiocarpal) joint** is an ellipsoid/condyloid joint.

Question 435: A 16-year-old boy sustained a severe radial nerve injury due to a midshaft humerus fracture following a motorcycle fall. Which of the following conditions would most likely result from this injury?

A. Loss of wrist extension leading to wrist drop (Correct Answer)
B. Weakness in pronating the forearm
C. Sensory loss over the ventral aspect of the thumb
D. Inability to oppose the thumb

Explanation: **Explanation:** **1. Why Option A is Correct:** The radial nerve (C5-T1) travels in the **spiral groove** of the humerus, making it highly susceptible to injury in midshaft humerus fractures. This nerve innervates the extensors of the forearm. A lesion at this level results in paralysis of the *Extensor Carpi Radialis Longus/Brevis* and the *Extensor Digitorum*, leading to an inability to extend the wrist against gravity—a clinical condition known as **Wrist Drop**. **2. Why the Other Options are Incorrect:** * **Option B:** Forearm pronation is primarily controlled by the **Median Nerve** (*Pronator Teres* and *Pronator Quadratus*). Radial nerve injury affects supination (via the *Supinator* muscle), though the *Biceps Brachii* (Musculocutaneous nerve) can still perform supination when the elbow is flexed. * **Option C:** Sensory loss in radial nerve injury typically occurs on the **dorsal** aspect of the first web space. Sensory loss on the **ventral (palmar)** aspect of the thumb is characteristic of a **Median Nerve** injury. * **Option D:** Opposition of the thumb is the function of the *Opponens Pollicis*, which is part of the thenar eminence and is supplied by the **Recurrent branch of the Median Nerve**. **3. High-Yield Clinical Pearls for NEET-PG:** * **Saturday Night Palsy:** Compression of the radial nerve in the axilla (e.g., crutch palsy) presents with wrist drop **plus** loss of triceps function (extension of the elbow). * **Midshaft Fracture:** Triceps function is usually **spared** because the branches to the long and medial heads of the triceps arise proximal to the spiral groove. * **PIN Palsy:** Injury to the Posterior Interosseous Nerve (a branch of the radial nerve) causes

Question 436: Winging of scapula is due to:

A. Medial pectoral nerve palsy
B. Lateral pectoral nerve palsy
C. Nerve to serratus anterior palsy (Correct Answer)
D. Nerve to latissimus dorsi palsy

Explanation: Explanation: Winging of the scapula is a clinical condition where the medial border of the scapula becomes abnormally prominent, resembling a wing. This occurs due to paralysis of the Serratus Anterior muscle. 1. Why the correct answer is right: The Long Thoracic Nerve (Nerve to Serratus Anterior), which arises from the roots of the brachial plexus (C5, C6, C7), supplies the serratus anterior. This muscle is the primary protractor of the scapula and holds its medial border firmly against the posterior thoracic wall. When this nerve is damaged (often due to trauma or surgery like radical mastectomy), the muscle fails to anchor the scapula, causing the medial border to "wing" outwards, especially when the patient attempts to push against a wall. 2. Why the incorrect options are wrong: * Medial & Lateral Pectoral Nerves: These supply the Pectoralis Major and Minor [1]. Paralysis leads to weakness in adduction and medial rotation of the arm, not scapular winging. * Nerve to Latissimus Dorsi (Thoracodorsal Nerve): This supplies the Latissimus Dorsi [1]. Injury results in weakness of extension, adduction, and internal rotation of the humerus (the "climbing" muscle). Clinical Pearls for NEET-PG: * Long Thoracic Nerve of Bell: Also known as the "5-6-7 nerve" (C5, 6, 7 keep the wings to heaven). * Testing: Ask the patient to push against a wall with outstretched hands. * Overhead Abduction: The serratus anterior (along with the Trapezius) is essential for rotating the scapula upwards to allow abduction of the arm beyond 90 degrees. * Pseudo-winging: Paralysis of the Trapezius (Spinal Accessory Nerve) can cause a milder form of winging, but the scapula moves laterally and superiorly, unlike the medial winging seen in serratus anterior palsy.

Question 437: The fourth dorsal interosseous muscle is innervated by?

A. Recurrent (motor) branch of the median nerve
B. Deep branch of the ulnar nerve (Correct Answer)
C. Dorsal branch of the ulnar nerve
D. Superficial branch of the radial nerve

Explanation: **Explanation:** The **fourth dorsal interosseous muscle** is one of the intrinsic muscles of the hand. The fundamental rule for hand innervation is that **all interossei (both dorsal and palmar)** are supplied by the **deep branch of the ulnar nerve (C8, T1).** **1. Why the correct answer is right:** The ulnar nerve enters the hand through Guyon’s canal and divides into superficial and deep branches [1]. The **deep branch** is purely motor; it follows the course of the deep palmar arch and supplies all interossei, the two medial lumbricals, the hypothenar muscles, and the adductor pollicis [2]. Since the fourth dorsal interosseous is located in the fourth intermetacarpal space, it falls under this motor distribution. **2. Why the incorrect options are wrong:** * **Option A:** The recurrent branch of the median nerve supplies the "TH" muscles of the thenar eminence (Abductor pollicis brevis, Flexor pollicis brevis, and Opponens pollicis). * **Option C:** The dorsal branch of the ulnar nerve is **purely sensory**, providing cutaneous innervation to the medial half of the dorsum of the hand and the proximal parts of the medial 2.5 fingers [1]. * **Option D:** The superficial branch of the radial nerve is **purely sensory**, supplying the skin over the lateral part of the dorsum of the hand and the base of the thumb. **High-Yield Clinical Pearls for NEET-PG:** * **DAB & PAD:** **D**orsal interossei **AB**duct (4 muscles); **P**almar interossei **AD**duct (3 muscles). * **Ulnar Paradox:** Higher lesions of the ulnar nerve (at the elbow) result in less prominent clawing than lower lesions (at the wrist) because the medial half of the Flexor Digitorum Profundus is also paralyzed. * **Froment’s Sign:** Tests for adductor pollicis palsy (ulnar nerve) where the patient compensates by flexing the thumb IP joint (median nerve/FPL).

Question 438: For which of the following nerve palsies is the below test detected?

A. Median nerve
B. Ulnar nerve (Correct Answer)
C. Radial nerve
D. Anterior interosseous nerve

Explanation: ***Ulnar nerve*** - **Froment's sign** is positive when there is weakness of the **adductor pollicis muscle**, which is innervated by the deep branch of the ulnar nerve. - Compensatory flexion of the **flexor pollicis longus (FPL)** occurs to maintain grip strength, causing thumb flexion at the interphalangeal joint. *Median nerve* - The median nerve primarily innervates the **thenar muscles** (abductor pollicis brevis, flexor pollicis brevis, opponens pollicis) and does not supply the adductor pollicis. - Median nerve palsy would present with **ape hand deformity** and loss of thumb opposition, not Froment's sign. *Radial nerve* - The radial nerve innervates **extensor muscles** of the wrist and fingers, not the adductor pollicis muscle. - Radial nerve palsy causes **wrist drop** and inability to extend the wrist and fingers, unrelated to thumb adduction testing. *Anterior interosseous nerve* - This nerve is a branch of the median nerve that innervates the **flexor pollicis longus**, **flexor digitorum profundus** (index and middle fingers), and **pronator quadratus**. - Anterior interosseous nerve palsy affects the **pincer grip** but does not cause weakness of thumb adduction tested by Froment's sign.

Question 439: A patient presents with a deep stab wound in the middle of the forearm, resulting in impaired movement of the thumb. Examination suggests a lesion of the anterior interosseous nerve. Which of the following muscles is paralyzed?

A. Flexor pollicis longus and brevis
B. Flexor pollicis longus and opponens pollicis
C. Flexor digitorum profundus and pronator quadratus (Correct Answer)
D. Flexor digitorum profundus and superficialis

Explanation: ### Explanation The **Anterior Interosseous Nerve (AIN)** is a purely motor branch of the **Median Nerve**. It arises in the proximal forearm, passes between the two heads of the pronator teres, and descends on the anterior surface of the interosseous membrane. **1. Why the Correct Answer is Right:** The AIN supplies exactly **2.5 muscles** in the deep compartment of the forearm: * **Flexor Pollicis Longus (FPL):** Responsible for flexion of the thumb IP joint. * **Pronator Quadratus (PQ):** The chief initiator of forearm pronation. * **Flexor Digitorum Profundus (FDP) - Lateral Half:** Specifically the tendons going to the index and middle fingers. Therefore, a lesion of the AIN leads to paralysis of the FDP (lateral half) and the Pronator Quadratus. **2. Analysis of Incorrect Options:** * **Option A & B:** These include the **Flexor Pollicis Brevis** and **Opponens Pollicis**. These are **intrinsic muscles of the hand** (thenar eminence) supplied by the recurrent branch of the median nerve, not the AIN [1]. * **Option D:** The **Flexor Digitorum Superficialis (FDS)** is supplied by the main trunk of the Median Nerve, not its anterior interosseous branch. **3. Clinical Pearls for NEET-PG:** * **Kiloh-Nevin Syndrome:** This is an isolated AIN palsy. Patients cannot make the **"OK" sign**; instead of a circle, they form a "pinch" (flat-to-flat) because they cannot flex the IP joint of the thumb (FPL) and the DIP joint of the index finger (FDP). * **Sensory Sparing:** Since the AIN is a purely motor nerve, there is **no sensory loss** in the hand, which helps differentiate it from a proximal median nerve injury [1]. * **The "Half" Rule:** Remember that the medial half of the FDP (ring and little fingers) is supplied by the **Ulnar Nerve**.

Question 440: Which of the following muscles is spared when the radial nerve is injured in the radial groove?

A. Long head of triceps (Correct Answer)
B. Medial head of triceps
C. Lateral head of triceps
D. Anconeus

Explanation: **Explanation:** The radial nerve arises from the posterior cord of the brachial plexus ($C5-T1$). To answer this question, one must understand the sequential branching pattern of the radial nerve as it descends the arm. **1. Why the Long Head of Triceps is spared:** The radial nerve gives off branches to the **long head of the triceps** and the **medial head (superior part)** high up in the axilla, *before* the nerve enters the spiral (radial) groove. Therefore, a fracture of the humeral shaft or a compression injury within the radial groove occurs distal to the origin of these fibers, leaving the long head of the triceps functional [1]. **2. Analysis of Incorrect Options:** * **Lateral head of triceps:** The branch to the lateral head arises *within* the radial groove. It is typically paralyzed in this injury. * **Medial head of triceps:** While the medial head receives a "high" branch in the axilla, its main innervation (inferior part) occurs within the radial groove. Thus, it is significantly weakened. * **Anconeus:** The nerve to the anconeus arises from the radial nerve while it is in the radial groove and descends through the medial head of the triceps to reach the muscle. It is consistently affected in spiral groove injuries. **Clinical Pearls for NEET-PG:** * **"Saturday Night Palsy":** Injury in the radial groove leads to **Wrist Drop** (loss of extensors) but **Extension of the Elbow is preserved** (due to the spared long head). * **Axillary Injury (Crutch Palsy):** If the nerve is injured in the axilla, the long head is also lost, resulting in the inability to extend the elbow. * **Sensory Loss:** In a radial groove injury, there is sensory loss over the narrow strip of the posterior forearm and the dorsal surface of the lateral $3\frac{1}{2}$ fingers. [1]

Practice by Chapter

Pectoral Region and Axilla

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Arm and Cubital Fossa

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Forearm and Hand

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Joints of Upper Limb

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Nerves of Upper Limb

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Arterial Supply and Venous Drainage

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Lymphatic Drainage

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Muscles and Their Actions

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Applied Anatomy and Clinical Correlations

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Surface Anatomy and Landmarks

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Upper Limb — MCQs

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