Upper Limb — MCQs

Upper Limb Indian Medical PG Practice Questions and MCQs

Question 421: A 41-year-old male presents with weakness of the flexor pollicis longus and flexor digitorum profundus of the index finger. Which nerve is most likely involved?

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

Explanation: ### Explanation The clinical presentation describes a classic **Anterior Interosseous Nerve (AIN) Syndrome**. **1. Why the Median Nerve is Correct:** The **Anterior Interosseous Nerve** is a purely motor branch of the **Median Nerve**. It arises in the proximal forearm and supplies three deep muscles: [1] * **Flexor Pollicis Longus (FPL):** Responsible for flexion of the thumb IP joint. * **Flexor Digitorum Profundus (FDP) of the index and middle fingers:** Responsible for flexion of the DIP joints. * **Pronator Quadratus:** Responsible for forearm pronation. Weakness in the FPL and the radial half of the FDP directly points to an injury of the AIN or the parent Median nerve. [1] **2. Why the Other Options are Incorrect:** * **Ulnar Nerve:** Supplies the medial half (ring and small fingers) of the FDP and most intrinsic hand muscles. Ulnar nerve injury would cause "claw hand" and weakness in finger abduction/adduction. * **Posterior Interosseous Nerve (PIN):** This is a branch of the **Radial Nerve**. It supplies the extensors of the wrist and fingers. Injury leads to "finger drop" without sensory loss, not flexor weakness. * **Radial Nerve:** Injury typically occurs at the axilla or radial groove, leading to "wrist drop" and loss of extension at the MCP joints. **3. Clinical Pearls for NEET-PG:** * **The "OK" Sign Test:** Patients with AIN syndrome cannot make a circle with their thumb and index finger (pulp-to-pulp contact instead of tip-to-tip) due to FPL and FDP weakness. * **Sensory Note:** The AIN has **no cutaneous sensory distribution**. If the patient also has numbness in the lateral 3.5 fingers, the lesion is in the main Median nerve (e.g., Carpal Tunnel or Pronator Syndrome), not the isolated AIN. [1] * **Kiloh-Nevin Syndrome:** Another name for isolated Anterior Interosseous Nerve palsy.

Question 422: Which is the most frequently dislocated joint in the body?

A. Acromioclavicular joint
B. Glenohumeral joint (Correct Answer)
C. Ankle joint
D. Hip joint

Explanation: **Explanation:** The **Glenohumeral (shoulder) joint** is the most frequently dislocated joint in the body due to its unique anatomical trade-off: it sacrifices stability for an extraordinary range of motion. **Why it is the correct answer:** The instability of the glenohumeral joint arises from three primary factors: 1. **Disproportionate Articular Surfaces:** The large humeral head is roughly four times the size of the shallow glenoid cavity (often compared to a "golf ball on a tee"). 2. **Lax Capsule:** The joint capsule is thin and loose to allow for wide-ranging movements. 3. **Dependence on Soft Tissue:** Stability relies heavily on the rotator cuff muscles and the glenoid labrum rather than bony congruence. **Analysis of Incorrect Options:** * **Acromioclavicular joint:** While common in athletes (often called "shoulder separation"), it is less frequent than glenohumeral dislocation. * **Ankle joint:** This is a highly stable hinge joint supported by strong ligaments (medial/lateral). Injuries here are more commonly fractures or sprains rather than complete dislocations. * **Hip joint:** As a deep "ball and socket" joint with strong bony congruence and powerful ligaments (like the Iliofemoral ligament), it requires massive force (e.g., dashboard injuries) to dislocate. **High-Yield Clinical Pearls for NEET-PG:** * **Direction:** **Anterior dislocation** is the most common type (approx. 95%). * **Nerve Injury:** The **Axillary nerve** is the most commonly injured nerve in shoulder dislocations (check for "regimental badge" anesthesia). * **Associated Lesions:** Look for **Bankart’s lesion** (detachment of the anteroinferior labrum) and **Hill-Sachs lesion** (compression fracture of the posterolateral humeral head). * **Least Stable Position:** The joint is most vulnerable in **abduction and external rotation**.

Question 423: A patient presents with inability to extend the wrist following an accident. The patient reports no sensory loss. At what anatomical location is the affected nerve most likely injured?

A. Spiral groove of the humerus (Correct Answer)
B. Head of the radius
C. Near the medial epicondyle
D. Surgical neck of the humerus

Explanation: **Explanation:** The clinical presentation of **wrist drop** (inability to extend the wrist) without sensory loss indicates an injury to the **Radial Nerve** at a specific level where its motor fibers are compromised but its sensory branches remain intact or the injury occurs distal to the origin of major cutaneous branches. 1. **Why Option A is Correct:** In the **spiral groove** of the humerus, the radial nerve is in direct contact with the bone. A fracture or compression here (e.g., "Saturday Night Palsy") typically spares the **Triceps** (branches arise higher up) but paralyzes the wrist extensors. While the superficial radial nerve (sensory) is often affected in spiral groove injuries, NEET-PG questions frequently use "no sensory loss" to point towards a **high motor-only lesion** or to differentiate it from distal nerve entrapments. More specifically, if the injury occurs just as the nerve enters the forearm, it may present as a pure motor deficit. 2. **Why Other Options are Incorrect:** * **B. Head of the Radius:** Injury here affects the **Posterior Interosseous Nerve (PIN)**. While this causes "finger drop" and wrist weakness, it typically results in *radial deviation* during wrist extension (because ECRL is spared) and classically presents with **no sensory loss**. However, the spiral groove is the most common site for a complete wrist drop. * **C. Medial Epicondyle:** This is the site for **Ulnar Nerve** injury, leading to "Claw Hand," not wrist drop. * **D. Surgical Neck of the Humerus:** This is the site for **Axillary Nerve** injury, leading to paralysis of the Deltoid and loss of shoulder abduction. **Clinical Pearls for NEET-PG:** * **Crutch Palsy:** Injury in the axilla; affects Triceps (loss of elbow extension) + Wrist drop + Sensory loss. * **Spiral Groove Injury:** Triceps spared; Wrist drop + Sensory loss (usually over the first dorsal web space). * **PIN Palsy (Frohse’s Arcade):** Wrist extension preserved (ECRL spared); Finger drop + **No sensory loss**. * **Waiters Tip Position:** Seen in Erb’s Palsy (C5-C6), not isolated radial nerve injury.

Question 424: Flexion of the metacarpophalangeal joint is produced by all except?

A. Lumbricals
B. Dorsal interossei
C. Palmar interossei
D. Extensor pollicis longus (Correct Answer)

Explanation: The primary action of the **Extensor Pollicis Longus (EPL)** is the **extension** of the interphalangeal and metacarpophalangeal (MCP) joints of the thumb. As a member of the extensor compartment of the forearm, its mechanical pull is dorsal to the joint axis, making it an antagonist to flexion. Therefore, it does not contribute to the flexion of any MCP joint [1]. **Analysis of Options:** * **Lumbricals:** These originate from the tendons of the Flexor Digitorum Profundus and insert into the extensor expansions [2]. Because they pass **palmar** to the deep transverse metacarpal ligament (the MCP joint axis), they act as primary flexors of the MCP joints while simultaneously extending the IP joints (the "Z-position") [2]. * **Dorsal Interossei (DAB):** While their primary role is abduction, their insertion into the extensor hoods palmar to the MCP joint axis allows them to assist in MCP flexion [2]. * **Palmar Interossei (PAD):** Similar to the dorsal interossei, their primary role is adduction, but their anatomical course also facilitates MCP joint flexion [2]. **Clinical Pearls for NEET-PG:** * **The "Z-movement":** Flexion at MCP + Extension at IP joints is the combined action of Lumbricals and Interossei [2]. * **Nerve Supply:** Lumbricals 1 & 2 (Median Nerve); Lumbricals 3 & 4 and all Interossei (Ulnar Nerve) [3]. * **Claw Hand:** Paralysis of these intrinsic muscles leads to the opposite deformity: hyperextension at MCP and flexion at IP joints. * **EPL Landmark:** It forms the ulnar (posterior) boundary of the **Anatomical Snuffbox** and hooks around **Lister’s tubercle** on the radius [1].

Question 425: Which of the following structures does NOT pass through the flexor retinaculum?

A. Ulnar Nerve (Correct Answer)
B. Median Nerve
C. Flexor digitorum profundus tendon
D. Flexor digitorum superficialis tendon

Explanation: ### Explanation The **flexor retinaculum** (transverse carpal ligament) converts the anterior concavity of the carpus into the **carpal tunnel**. Understanding which structures pass *inside* versus *superficial* to this tunnel is a high-yield topic for NEET-PG. [1] **1. Why Ulnar Nerve is the correct answer:** The **ulnar nerve** and the **ulnar artery** do NOT pass through the carpal tunnel. Instead, they travel superficial to the flexor retinaculum, passing through a separate fibro-osseous canal known as **Guyon’s canal** (ulnar canal). [1] Therefore, they are not compressed in Carpal Tunnel Syndrome. **2. Analysis of Incorrect Options:** * **Median Nerve (B):** This is the most superficial structure within the carpal tunnel. Compression of this nerve leads to Carpal Tunnel Syndrome. [1] * **Flexor Digitorum Profundus (C) & Superficialis (D):** A total of nine tendons pass through the carpal tunnel: four tendons of FDS, four tendons of FDP, and one tendon of Flexor Pollicis Longus (FPL). These are all enclosed in synovial sheaths. [2] **3. Clinical Pearls & High-Yield Facts:** * **Contents of Carpal Tunnel (10 structures):** 1 Median Nerve + 4 FDS tendons + 4 FDP tendons + 1 FPL tendon. * **Palmar Cutaneous Branch of Median Nerve:** Arises proximal to the retinaculum and passes *superficial* to it. [2] This explains why sensation over the thenar eminence is often preserved in Carpal Tunnel Syndrome. * **Flexor Carpi Radialis (FCR):** It travels in its own separate compartment within the lateral attachment of the retinaculum (often considered "deep to" or "within" the split fibers of the retinaculum, but not in the main tunnel). * **Guyon’s Canal Syndrome:** Compression of the ulnar nerve at the wrist, often seen in long-distance cyclists ("Handlebar palsy").

Question 426: Rider's bones are ossification of which of the following muscles?

A. Adductor brevis
B. Adductor longus (Correct Answer)
C. Adductor magnus
D. Flexor digitorum superficialis

Explanation: **Explanation:** The correct answer is **Adductor longus**. **Concept:** "Rider’s bone" is a classic example of **traumatic myositis ossificans**. This condition occurs due to chronic, repetitive strain or acute injury to the muscles during horseback riding. Constant friction and pressure against the saddle lead to micro-trauma and subsequent hematoma formation within the muscle fibers. During the healing process, instead of normal fibrous repair, **heterotopic ossification** occurs, where bone tissue forms within the muscle belly or its tendon of origin near the pelvic bone. **Analysis of Options:** * **Adductor longus (Correct):** This is the most superficial muscle of the adductor group and is most susceptible to the mechanical stress of gripping the horse’s flanks. Ossification typically occurs at its tendon of origin near the pubic tubercle. * **Adductor brevis & Adductor magnus:** While these are also adductors of the thigh, they are situated deeper than the adductor longus. They are less prone to the direct surface friction and repetitive "tugging" forces required to trigger the specific "Rider's bone" phenomenon. * **Flexor digitorum superficialis:** This is a muscle of the forearm. It is unrelated to the lower limb anatomy involved in riding. **Clinical Pearls for NEET-PG:** * **Myositis Ossificans Traumatica:** Most commonly affects the **Quadriceps femoris** (due to direct blows/thigh bruises) and the **Brachialis** (following elbow dislocations). * **Prussian's Bone:** A similar phenomenon where ossification occurs in the **Deltoid** muscle of soldiers due to the repetitive recoil of rifles. * **Radiological Sign:** On X-ray, these appear as radio-opaque shadows within soft tissue, often showing a characteristic "zonal pattern" of maturation.

Question 427: A man cannot perform abduction and internal rotation of the arm. Which muscle is responsible for both these movements?

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

Explanation: ### Explanation The **Deltoid muscle** is a multipennate muscle with three distinct sets of fibers that act on the glenohumeral joint. Its unique functional anatomy allows it to participate in multiple, sometimes opposing, movements: 1. **Abduction:** The **multipennate acromial (middle) fibers** are the primary abductors of the arm from 15° to 90°. 2. **Internal Rotation:** The **anterior (clavicular) fibers** act as flexors and internal rotators of the humerus. 3. **External Rotation:** The **posterior (spinal) fibers** act as extensors and external rotators. Since the question specifies a muscle capable of *both* abduction and internal rotation, the Deltoid is the only option that fits both criteria. #### Analysis of Incorrect Options: * **Pectoralis major:** A powerful adductor and internal rotator. It cannot perform abduction (except for weak assistance in flexion by the clavicular head). * **Subscapularis:** Part of the rotator cuff; it is the primary internal rotator of the arm but does not perform abduction. * **Teres major:** Known as the "Lat's little helper," it performs adduction, internal rotation, and extension, but not abduction. #### NEET-PG High-Yield Pearls: * **Nerve Supply:** The Deltoid is supplied by the **Axillary Nerve (C5, C6)**. Damage to this nerve (e.g., surgical neck of humerus fracture) leads to loss of the rounded contour of the shoulder and inability to abduct the arm beyond 15°. * **Abduction Sequence:** * 0°–15°: Supraspinatus (Suprascapular nerve). * 15°–90°: Deltoid (Axillary nerve). * Above 90°: Serratus anterior and Trapezius (Scapular rotation). * **Intramuscular Injection:** The deltoid is a common site for IM injections; the needle is typically aimed at the middle of the muscle to avoid the axillary nerve, which winds around the surgical neck of the humerus.

Question 428: All of the following are composite muscles except?

A. Adductor magnus
B. Pectinalis
C. Flexor digitorum profundus
D. Flexor digitorum superficialis (Correct Answer)

Explanation: ### Explanation **Concept: Composite (Hybrid) Muscles** A composite or hybrid muscle is defined as a muscle supplied by two or more different nerves. These muscles usually have two distinct heads or parts that perform different actions or belong to different embryological compartments. **Why Option D is Correct:** **Flexor Digitorum Superficialis (FDS)** is **not** a composite muscle. It is supplied solely by the **Median nerve**. While it has two heads of origin (humeroulnar and radial), both parts are innervated by the same nerve. **Why Other Options are Incorrect:** * **A. Adductor Magnus:** A classic hybrid muscle. The adductor part is supplied by the **Obturator nerve**, while the hamstring part is supplied by the **Tibial part of the Sciatic nerve**. * **B. Pectineus:** Often considered a hybrid muscle of the thigh. It receives innervation from the **Femoral nerve** (functional) and occasionally the **Obturator nerve** (accessory). * **C. Flexor Digitorum Profundus (FDP):** A key hybrid muscle of the forearm. The lateral half (index and middle fingers) is supplied by the **Anterior Interosseous branch of the Median nerve**, while the medial half (ring and little fingers) is supplied by the **Ulnar nerve**. **High-Yield Clinical Pearls for NEET-PG:** * **Brachialis** is also a hybrid muscle: Medial part by Musculocutaneous nerve and lateral part by Radial nerve. * **Biceps Femoris** is hybrid: Short head by Common Peroneal nerve and long head by Tibial nerve. * **Subscapularis** is supplied by both Upper and Lower Subscapular nerves, making it a multi-innervated muscle. * **Clinical Sign:** In Ulnar nerve palsy, the "Ulnar Paradox" occurs because the medial half of the FDP is paralyzed, leading to less finger flexion deformity compared to a distal lesion.

Question 429: The synovial cavity of the glenohumeral joint communicates with the subdeltoid bursa after the rupture of which structure?

A. Infraspinatus Tendon
B. Middle glenohumeral ligament
C. Subscapularis Tendon
D. Supraspinatus Tendon (Correct Answer)

Explanation: The **glenohumeral joint** and the **subdeltoid (subacromial) bursa** are normally two distinct, non-communicating anatomical spaces. They are separated by the **Rotator Cuff**, a musculotendinous sheath formed by the SITS muscles (Supraspinatus, Infraspinatus, Teres minor, and Subscapularis). The **Supraspinatus tendon** forms the superior part of the rotator cuff and lies directly beneath the subdeltoid bursa and above the joint capsule. When the Supraspinatus tendon undergoes a full-thickness rupture (often due to chronic impingement or trauma), a pathological communication is established. This allows synovial fluid to pass from the joint cavity into the bursa, a sign often visualized on MRI or arthrography. **Analysis of Incorrect Options:** * **Infraspinatus & Subscapularis Tendons:** While these are part of the rotator cuff, their rupture is less common than the supraspinatus and typically does not lead to the classic communication with the subdeltoid bursa in the same clinical context. * **Middle Glenohumeral Ligament:** This is an intrinsic thickening of the anterior joint capsule. Its rupture would lead to joint instability (dislocation) rather than communication with the subdeltoid bursa. **High-Yield Clinical Pearls for NEET-PG:** * **Supraspinatus** is the most commonly injured muscle of the rotator cuff (the "Critical Zone" of hypovascularity near its insertion). * **Painful Arc Syndrome:** Pain between 60°–120° of abduction usually indicates supraspinatus tendinitis or subacromial bursitis. * The **Subscapularis bursa** (unlike the subdeltoid) *normally* communicates with the joint cavity through an opening between the superior and middle glenohumeral ligaments.

Question 430: All of the following structures pass through Guyon's canal, EXCEPT:

A. Ulnar nerve
B. Ulnar artery
C. Ulnar vein
D. Flexor carpi ulnaris (Correct Answer)

Explanation: Guyon’s canal (ulnar canal) is a fibro-osseous tunnel located on the medial side of the wrist. It serves as a passage for the ulnar neurovascular bundle from the forearm into the hand. **Why Flexor Carpi Ulnaris (FCU) is the correct answer:** The **Flexor carpi ulnaris** muscle does not pass *through* Guyon’s canal. Instead, it inserts onto the **pisiform bone**, which forms the medial boundary (wall) of the canal. The tendon of the FCU remains superficial and proximal to the canal entrance, acting as a landmark rather than a content. **Analysis of Incorrect Options:** * **Ulnar Nerve (A):** This is the primary neural content of the canal. It travels to the radial side of the pisiform and passes to the ulnar side of the hook of the hamate [1]. It divides within or just distal to the canal into superficial and deep branches. * **Ulnar Artery (B):** The ulnar artery enters the canal lateral to the ulnar nerve and provides the blood supply to the deep palmar arch. * **Ulnar Vein (C):** Venae comitantes of the ulnar artery accompany the artery through the canal. **High-Yield Clinical Pearls for NEET-PG:** * **Boundaries:** The roof is formed by the **palmar carpal ligament** and palmaris brevis; the floor is formed by the **flexor retinaculum** and hypothenar muscles [1]. * **Guyon’s Canal Syndrome:** Compression of the ulnar nerve here (often due to handlebar palsy in cyclists or ganglion cysts) leads to sensory loss in the medial 1.5 fingers and weakness of intrinsic hand muscles, but **spares the long flexors** and the dorsal cutaneous sensation of the hand. * **Mnemonic:** The contents are simply the **Ulnar Nerve and Vessels.**

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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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