Upper Limb — MCQs

A 32-year-old man presents with multiple fractures of his right upper limb following a severe car crash. He underwent surgery with fixation of bony fragments using metallic plates. Five months postoperatively, he presents with the ability to abduct his arm and extend his forearm. Sensation in the forearm and hand is intact. However, his hand grasp is very weak, and he cannot extend his wrist against gravity. Which of the following nerves was most likely injured during the surgical procedure?

Upper Limb Indian Medical PG Practice Questions and MCQs

Question 191: What is the preaxial border of the limb?

A. Ulnar border of forearm
B. Fibular border of leg
C. Radial border of forearm (Correct Answer)
D. None of the above

Explanation: ### Explanation The concept of **preaxial and postaxial borders** is rooted in embryology. During the 5th week of development, limb buds appear as outpocketings from the ventrolateral body wall. Each limb bud has a cranial (cephalic) border and a caudal (caudal) border. **1. Why the Radial Border is Correct:** The **preaxial border** corresponds to the cranial or thumb-side of the developing limb. In the upper limb, the radius is the lateral bone in the anatomical position. Therefore, the **radial border** of the forearm (lateral side) is the preaxial border. Conversely, the **postaxial border** corresponds to the caudal or little-finger side, represented by the **ulnar border** (medial side). **2. Why Other Options are Incorrect:** * **Ulnar border of forearm:** This is the **postaxial border** of the upper limb. * **Fibular border of leg:** In the lower limb, the **preaxial border** is the **tibial (medial) side** (big toe side), while the **fibular (lateral) side** is the **postaxial border**. This difference occurs because the lower limb rotates medially by 90 degrees during development, whereas the upper limb rotates laterally. **3. High-Yield Facts for NEET-PG:** * **Rotation Rule:** Upper limbs rotate **laterally** (extensors on the posterior aspect); Lower limbs rotate **medially** (extensors on the anterior aspect). * **Dermatomes:** Preaxial borders are generally supplied by higher spinal segments (e.g., C5-C6 for the radial side), while postaxial borders are supplied by lower segments (e.g., C8-T1 for the ulnar side). * **Preaxial Bone:** Radius (Upper Limb), Tibia (Lower Limb). * **Postaxial Bone:** Ulna (Upper Limb), Fibula (Lower Limb).

Question 192: Which cervical nerve root supplies the thumb dermatome?

A. C5 and T1
B. C6 (Correct Answer)
C. C7
D. C8

Explanation: The cutaneous innervation of the upper limb follows a specific segmental pattern (dermatomes) derived from the brachial plexus. The **C6 nerve root** is responsible for the sensory supply to the lateral aspect of the forearm and, most characteristically, the **thumb** [1]. **Why C6 is correct:** In the standard dermatomal map, C6 supplies the radial side of the forearm and the entire thumb [1]. A classic memory aid for NEET-PG is to form a "6" with your thumb and index finger; this reminds you that C6 covers these digits. **Analysis of Incorrect Options:** * **A. C5 and T1:** C5 supplies the skin over the deltoid and the lateral aspect of the upper arm (pre-axial). T1 supplies the medial aspect of the forearm and distal arm (post-axial). * **C. C7:** This nerve root typically supplies the middle finger (the "center" of the hand). * **D. C8:** This nerve root supplies the medial aspect of the hand, specifically the ring and little fingers. **High-Yield Clinical Pearls for NEET-PG:** * **Reflex Association:** C6 is also the primary root for the **Brachioradialis and Biceps reflexes**. * **Motor Supply:** C6 contributes to wrist extension. A C6 radiculopathy would present with sensory loss in the thumb and weakness in wrist extension. * **The "Hand Rule":** * Thumb = C6 * Middle finger = C7 * Little finger = C8 * **Axilla:** T2 (via the intercostobrachial nerve). * **Nipple line:** T4.

Question 193: A 50-year-old woman presented with numbness and weakness of the right hand. On examination, there was atrophy of the thenar eminence and hypoaesthesia in the distribution. Compression of which of the following nerves could explain the presentation?

A. Ulnar Nerve
B. Radial Nerve
C. Axillary Nerve
D. Median Nerve (Correct Answer)

Explanation: ### **Explanation** The clinical presentation of **thenar eminence atrophy** and **hypoaesthesia** (numbness) in the hand is a classic sign of **Median Nerve** compression, most commonly occurring at the wrist within the carpal tunnel (Carpal Tunnel Syndrome). **1. Why Median Nerve is Correct:** The median nerve provides motor innervation to the **LOAF** muscles (Lateral two Lumbricals, Opponens pollicis, Abductor pollicis brevis, and Flexor pollicis brevis). The latter three make up the thenar eminence. Chronic compression leads to denervation and subsequent atrophy of these muscles [1]. Sensitivities are affected in the lateral 3½ fingers and the corresponding palmar surface [1]. **2. Why Other Options are Incorrect:** * **Ulnar Nerve:** Innervates the hypothenar eminence and most intrinsic hand muscles. Injury leads to "Claw Hand" and atrophy of the interossei, not the thenar eminence [1]. * **Radial Nerve:** Primarily supplies the extensors of the forearm and wrist. Injury typically results in "Wrist Drop" and sensory loss on the dorsal aspect of the first web space. * **Axillary Nerve:** Innervates the deltoid and teres minor muscles. Injury results in loss of shoulder abduction and sensory loss over the "regimental badge" area of the lateral arm. **3. NEET-PG High-Yield Pearls:** * **Ape Thumb Deformity:** Caused by median nerve palsy, where the thumb is adducted and extended due to the loss of opponens pollicis and abductor pollicis brevis. * **Pointing Index (Benedict’s Sign):** Seen when attempting to make a fist in high median nerve palsy. * **Tinel’s Sign & Phalen’s Test:** Key clinical provocative tests used to diagnose Carpal Tunnel Syndrome. * **Palmar Cutaneous Branch:** This branch of the median nerve arises *proximal* to the carpal tunnel; therefore, sensation over the central palm is often spared in Carpal Tunnel Syndrome [1].

Question 194: Which arteries form the arterial anastomosis around the shoulder?

A. 2nd part of subclavian artery with 2nd part of axillary artery
B. 1st part of subclavian artery with 3rd part of axillary artery (Correct Answer)
C. 3rd part of subclavian artery with 1st part of axillary artery
D. 3rd part of subclavian artery with 3rd part of axillary artery

Explanation: The arterial anastomosis around the scapula is a vital collateral circulation that ensures blood flow to the upper limb if the axillary artery is obstructed. ### **Why Option B is Correct** The anastomosis occurs between branches of the **1st part of the subclavian artery** and the **3rd part of the axillary artery**. Specifically, it involves: 1. **From the Subclavian Artery (1st Part):** The **Thyrocervical trunk** gives off the **Suprascapular artery** and the **Deep branch of the Transverse cervical artery** (also known as the Dorsal scapular artery). 2. **From the Axillary Artery (3rd Part):** The **Subscapular artery** gives off the **Circumflex scapular artery**. These vessels meet on the dorsal and costal surfaces of the scapula, allowing blood to bypass the axillary artery if it is ligated or blocked between the 1st and 3rd parts. ### **Why Other Options are Incorrect** * **Options A, C, and D:** These are incorrect because they misidentify the segments involved. The anastomosis is functionally designed to bridge the gap between the root of the neck (Subclavian) and the distal portion of the axillary artery. The 2nd part of the subclavian and the 1st/2nd parts of the axillary do not provide the primary vessels for this specific scapular network. ### **NEET-PG High-Yield Pearls** * **Direction of Flow:** If the axillary artery is ligated between the 1st and 3rd parts, blood flow in the **circumflex scapular artery reverses** to reach the distal axillary artery. * **Acromial Anastomosis:** A separate network exists over the acromion process involving the acromial branches of the Thoracoacromial, Suprascapular, and Posterior Circumflex Humeral arteries. * **Clinical Significance:** This collateral circulation is so efficient that the axillary artery can often be ligated between the 1st and 2nd parts without causing gangrene of the arm.

Question 195: A man is unable to hold typing paper between his index and middle fingers. Which of the following nerves was likely injured?

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

Explanation: ### Explanation The correct answer is **C. Ulnar nerve**. **1. Why the Ulnar Nerve is Correct:** The action described—holding a piece of paper between the fingers—is called **adduction of the fingers**. This movement is performed by the **Palmar Interossei** muscles. All interossei (both palmar and dorsal) are innervated by the **deep branch of the ulnar nerve** (C8, T1) [1]. * **Palmar Interossei (3 muscles):** Adduct the fingers (PAD). * **Dorsal Interossei (4 muscles):** Abduct the fingers (DAB). Inability to adduct the fingers results in a positive "Card Test," where the patient cannot grip a piece of paper between their extended fingers against resistance [2]. **2. Why the Other Options are Incorrect:** * **Radial Nerve:** Primarily supplies the extensors of the elbow, wrist, and fingers [1]. Injury leads to "Wrist Drop," not loss of finger adduction. * **Median Nerve:** Supplies the thenar muscles (LOAF: Lumbricals 1 & 2, Opponens pollicis, Abductor pollicis brevis, Flexor pollicis brevis) [1]. Injury affects thumb opposition and precision grip (Ape thumb deformity). * **Musculocutaneous Nerve:** Supplies the anterior compartment of the arm (Biceps, Coracobrachialis, Brachialis). Injury results in weak elbow flexion and loss of sensation on the lateral forearm. **3. High-Yield Clinical Pearls for NEET-PG:** * **Froment’s Sign:** Another test for ulnar nerve palsy. The patient compensates for a weak **Adductor Pollicis** (ulnar nerve) by using the **Flexor Pollicis Longus** (median nerve), causing the thumb's IP joint to flex when gripping paper [2]. * **Ulnar Paradox:** The higher the lesion (at the elbow), the less prominent the clawing of the fingers, because the long flexors (FDP) are also paralyzed. * **Wartenberg’s Sign:** Inability to adduct the little finger due to ulnar nerve palsy [2].

Question 196: Which of the following clinical signs is observed in median nerve injury?

A. Pointing Index (Correct Answer)
B. Wristdrop
C. Wartenberg's Sign
D. Regimental badge sign

Explanation: **Explanation:** The **Median Nerve** is the "nerve of precision" and the "laborer’s nerve." Injury to this nerve, particularly at or above the elbow (High Median Nerve Palsy), results in the **Pointing Index** (also known as the **Ochsner’s Clasping Test**). 1. **Why Pointing Index is Correct:** When a patient is asked to clasp their hands together, the index finger remains extended. This occurs because the median nerve [1] supplies the **Flexor Digitorum Profundus (FDP)** to the index and middle fingers and the **Flexor Digitorum Superficialis (FDS)**. Paralysis of these muscles prevents flexion of the PIP and DIP joints of the index finger, leaving it "pointing." 2. **Analysis of Incorrect Options:** * **Wristdrop:** Caused by **Radial Nerve** injury (typically at the mid-shaft of the humerus). It results from paralysis of the wrist extensors. * **Wartenberg’s Sign:** Observed in **Ulnar Nerve** palsy. It is the inability to adduct the little finger due to weakness of the 3rd palmar interosseous muscle. * **Regimental Badge Sign:** A patch of sensory loss over the lateral aspect of the shoulder (deltoid area) caused by **Axillary Nerve** injury. **High-Yield Clinical Pearls for NEET-PG:** * **Ape Thumb Deformity:** Seen in median nerve injury due to paralysis of the Thenar muscles (Opponens pollicis), leading to loss of thumb opposition. * **Benediction Deformity:** Seen when the patient attempts to make a fist; the index and middle fingers stay extended (similar mechanism to Pointing Index). * **Carpal Tunnel Syndrome:** The most common site of compression for the median nerve at the wrist [1].

Question 197: The axillary artery is divided into three parts by which muscle?

A. Pectoralis major
B. Pectoralis minor (Correct Answer)
C. Teres major
D. Teres minor

Explanation: The **axillary artery** is the direct continuation of the subclavian artery, beginning at the outer border of the first rib and ending at the lower border of the teres major muscle. ### Why Pectoralis Minor is Correct The **pectoralis minor muscle** crosses the axillary artery anteriorly, serving as the key anatomical landmark that divides it into three functional parts: 1. **First Part:** Proximal to the muscle (between the 1st rib and upper border of pectoralis minor). It has **one** branch. 2. **Second Part:** Posterior (deep) to the muscle. It has **two** branches. [1] 3. **Third Part:** Distal to the muscle (between the lower border of pectoralis minor and lower border of teres major). It has **three** branches. ### Why Other Options are Incorrect * **Pectoralis Major:** While it forms the anterior wall of the axilla, it does not anatomically segment the artery into three distinct parts. [1] * **Teres Major:** This muscle marks the **termination** of the axillary artery, where it becomes the brachial artery. * **Teres Minor:** This muscle forms part of the posterior wall of the axilla and is a boundary for the quadrangular and triangular spaces, but it does not divide the artery. ### High-Yield Clinical Pearls for NEET-PG * **Mnemonic for Branches:** "Save The Lions And Pity She-devils" (Superior thoracic, Thoraco-acromial, Lateral thoracic, Subscapular, Anterior circumflex humeral, Posterior circumflex humeral). * **The "Rule of Numbers":** The part number corresponds to the number of branches (1st part = 1 branch; 2nd part = 2; 3rd part = 3). * **Largest Branch:** The **subscapular artery** (from the 3rd part) is the largest branch of the axillary artery. * **Surgical Landmark:** The cords of the brachial plexus are named (Lateral, Medial, Posterior) based on their relationship to the **second part** of the axillary artery. [1]

Question 198: The cephalic vein drains into which of the following veins?

A. Brachial vein
B. Subclavian vein
C. Axillary vein (Correct Answer)
D. Inferior vena cava

Explanation: **Explanation:** The **cephalic vein** is a major superficial vein of the upper limb [1]. It originates from the radial side of the dorsal venous arch of the hand, ascends along the lateral aspect of the forearm and arm, and travels within the **deltopectoral groove** (between the deltoid and pectoralis major muscles) [1]. It ultimately pierces the **clavipectoral fascia** to drain into the **axillary vein**, just before the axillary vein becomes the subclavian vein at the outer border of the first rib [1]. **Analysis of Options:** * **Axillary vein (Correct):** This is the anatomical termination point of the cephalic vein [1]. * **Brachial vein (Incorrect):** The **basilic vein** (the medial superficial vein) joins the venae comitantes of the brachial artery to form the axillary vein; the cephalic vein remains lateral and more superficial until its termination. * **Subclavian vein (Incorrect):** While the cephalic vein drains very close to the transition point, the axillary vein becomes the subclavian vein only after crossing the **lateral border of the 1st rib**. The cephalic vein joins the axillary vein proximal to this landmark. * **Inferior vena cava (Incorrect):** The IVC drains the lower half of the body. Venous return from the upper limb enters the Superior Vena Cava (SVC) via the brachiocephalic veins. **High-Yield Clinical Pearls for NEET-PG:** * **Deltopectoral Triangle:** The cephalic vein is a key landmark in this triangle (bounded by the deltoid, pectoralis major, and clavicle) and is often used for **permanent pacemaker lead insertion**. * **Median Cubital Vein:** This vein connects the cephalic and basilic veins in the cubital fossa and is the preferred site for venipuncture [1]. * **Mnemonic:** The **B**asilic vein goes **B**eep (Deep) earlier to join the brachial, while the **C**ephalic vein stays **C**lose to the surface until the shoulder.

Question 199: The carpal tunnel contains all of the following important structures, EXCEPT:

A. Median Nerve
B. Flexor pollicis longus
C. Flexor carpi radialis (Correct Answer)
D. Flexor digitorum superficialis

Explanation: ### Explanation The **Carpal Tunnel** is a fibro-osseous gateway located on the palmar aspect of the wrist, formed by the deep arch of the carpal bones and the overlying **Flexor Retinaculum** (Transverse Carpal Ligament) [1]. #### Why Flexor Carpi Radialis (FCR) is the Correct Answer: The **Flexor carpi radialis** tendon does **not** pass through the carpal tunnel. Instead, it travels through a separate, dedicated compartment within the lateral attachment of the flexor retinaculum (the groove of the trapezium) [2]. It is considered extrinsic to the tunnel itself. #### Analysis of Other Options: The carpal tunnel contains exactly **10 structures**: * **Median Nerve (Option A):** The most superficial and clinically significant structure [1]. Compression leads to Carpal Tunnel Syndrome. * **Flexor Pollicis Longus (Option B):** A single tendon located on the radial side of the tunnel [3]. * **Flexor Digitorum Superficialis (Option D):** Four tendons (arranged in two layers: middle and ring finger tendons are superficial to index and little finger tendons). * **Flexor Digitorum Profundus:** Four tendons located in the deepest layer [3]. #### High-Yield Clinical Pearls for NEET-PG: * **Contents Mnemonic:** "4+4+1+1" (4 FDS, 4 FDP, 1 FPL, 1 Median Nerve). * **Ulnar Nerve & Artery:** These pass superficial to the flexor retinaculum through **Guyon’s Canal**; they are never contents of the carpal tunnel [1]. * **Palmar Cutaneous Branch of Median Nerve:** Arises proximal to the tunnel and passes superficial to the retinaculum [3]. This explains why sensation over the **thenar eminence is spared** in Carpal Tunnel Syndrome. * **Most Common Cause of Compression:** Inflammation of the synovial sheaths (tenosynovitis) surrounding the flexor tendons.

Question 200: A 32-year-old man presents with multiple fractures of his right upper limb following a severe car crash. He underwent surgery with fixation of bony fragments using metallic plates. Five months postoperatively, he presents with the ability to abduct his arm and extend his forearm. Sensation in the forearm and hand is intact. However, his hand grasp is very weak, and he cannot extend his wrist against gravity. Which of the following nerves was most likely injured during the surgical procedure?

A. Posterior cord of the brachial plexus
B. Radial nerve at the distal third of the humerus (Correct Answer)
C. Radial and ulnar nerves
D. Radial, ulnar, and median nerves

Explanation: ### Explanation **1. Why Option B is Correct:** The clinical presentation points toward a **high radial nerve palsy** occurring distal to the origin of the branches for the triceps. * **Intact Forearm Extension:** The branches to the **Triceps brachii** arise in the axilla and the proximal part of the radial groove. Since the patient can extend his forearm, the nerve is intact at the proximal humerus. * **Intact Abduction:** This confirms the **Axillary nerve** (Deltoid) is functional. * **Wrist Drop & Weak Grasp:** The radial nerve supplies the extensors of the wrist and fingers [1]. Inability to extend the wrist against gravity (wrist drop) is a classic sign. A weak hand grasp occurs because the wrist extensors cannot stabilize the wrist in extension, which is biomechanically necessary for the long flexors to exert maximum force. * **Surgical Context:** The distal third of the humerus is a high-risk zone for radial nerve injury during plate fixation (Holstein-Lewis fracture site), where the nerve pierces the lateral intermuscular septum [1]. **2. Why Other Options are Incorrect:** * **Option A (Posterior Cord):** Injury here would cause paralysis of the Deltoid (loss of abduction) and the Triceps (loss of forearm extension), both of which are functioning in this patient. * **Option C & D:** There is no evidence of **Ulnar nerve** (claw hand, loss of adduction/abduction of fingers) or **Median nerve** (ape thumb deformity, loss of pronation) involvement. Sensation in the hand and forearm is also intact, ruling out extensive plexus or multi-nerve injuries. **3. Clinical Pearls for NEET-PG:** * **Sensory Sparing:** In distal humeral injuries, the **Posterior Cutaneous Nerve of the Forearm** often branches off higher up, explaining why sensation may remain intact despite motor loss. * **The "Saturday Night Palsy" vs. "Crutch Palsy":** Both involve the radial nerve, but the level of injury determines if the Triceps is spared. * **Rule of Thumb:** If the patient can extend the elbow, the radial nerve lesion is in the **spiral groove or distal to it** [1]. If they cannot extend the elbow, the lesion is in the **axilla**.

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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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