Upper Limb Practice Questions

Q: A patient who has taken the first COVID vaccine comes for the second dose. An astute nurse noticed that the shoulder was flabby, flat, and was asymmetrical. There was an associated loss of contour of the shoulder joint. Injury to which of the structures might have resulted and was avoidable?

Deltoid muscle. ***Deltoid muscle*** - The **deltoid muscle** is the principal muscle that gives the shoulder its rounded contour. Damage to or atrophy of the deltoid can lead to a **flat, flabby, and asymmetrical shoulder**. - Improper vaccine administration, such as injecting too high or too deep, can directly injure the deltoid muscle, leading to inflammation (**SIRVA - Shoulder Injury Related to Vaccine Administration**) or even deltoid atrophy, which would cause the observed lack of contour. *Supraspinatus muscle* - The **supraspinatus** is primarily involved in the initial **abduction** of the arm and stabilization of the shoulder joint, but it does not significantly contribute to the visible external contour of the shoulder. - Injury to the supraspinatus mainly causes **pain and weakness** with abduction, rather than a visible change in shoulder shape. *Infraspinatus muscle* - The **infraspinatus** is a rotator cuff muscle primarily responsible for **external rotation** of the arm. - Injury to this muscle would cause weakness in external rotation and potentially posterior shoulder pain, but not the noticeable loss of shoulder contour described. *Teres minor muscle* - The **teres minor** is also a rotator cuff muscle assisting in **external rotation** and stabilization of the humeral head. - Similar to the infraspinatus, its injury would impair external rotation and cause posterior shoulder pain, but it doesn't define the overall shape of the shoulder.

Q: A patient presents with difficulty extending their wrist following trauma to the posterior forearm. Which of the following muscles would be most affected by injury to the posterior interosseous nerve?

Extensor digitorum. ***Extensor digitorum*** - The **posterior interosseous nerve (PIN)** innervates most muscles of the **posterior compartment of the forearm**, including the extensor digitorum. [1] - Loss of function in the **extensor digitorum** would directly impair **extension of the fingers** and contribute significantly to difficulty extending the wrist. [1] *Extensor carpi ulnaris* - This muscle is also innervated by the **posterior interosseous nerve (PIN)** and contributes to **wrist extension** and **ulnar deviation**. - While its innervation by the PIN is correct, injury to the PIN would affect this muscle, but the *extensor digitorum* is more broadly responsible for the stated primary symptom (difficulty extending the wrist), as its primary action is finger and thus wrist extension. *Extensor carpi radialis brevis* - While it is a **wrist extensor**, it is innervated by the **deep branch of the radial nerve** *before* it becomes the posterior interosseous nerve. - Therefore, an isolated injury to the **posterior interosseous nerve** proper would typically spare the extensor carpi radialis brevis. *Extensor pollicis longus* - This muscle is indeed innervated by the **posterior interosseous nerve (PIN)** and acts to extend the **thumb**. [1] - While it would be affected, the primary problem described is difficulty extending the *wrist*, for which the extensor digitorum plays a more significant and general role than the extensor pollicis longus.

Q: A 45-year-old woman undergoes a modified radical mastectomy for breast cancer. Following the procedure, she experiences numbness in the medial aspect of her upper arm. Which of the following nerves was most likely injured during the surgery?

Intercostobrachial nerve. ***Intercostobrachial nerve*** - The **intercostobrachial nerve** provides sensory innervation to the **medial aspect of the upper arm** and is vulnerable to injury during **axillary dissection** in a modified radical mastectomy [1]. - Injury typically results in **numbness** or **paresthesia** in this specific dermatomal distribution [1]. *Musculocutaneous nerve* - The **musculocutaneous nerve** innervates the muscles of the **anterior compartment of the arm** (e.g., biceps brachii) and provides sensation to the **lateral forearm**. - Damage would primarily affect **forearm sensation** and arm flexion, not medial upper arm sensation. *Thoracodorsal nerve* - The **thoracodorsal nerve** innervates the **latissimus dorsi muscle**, a large muscle of the back and shoulder [1]. - Injury would lead to **weakness in adduction, extension, and internal rotation** of the arm, with no sensory deficit in the upper arm [1]. *Long thoracic nerve* - The **long thoracic nerve** innervates the **serratus anterior muscle**, which stabilizes the scapula and allows for arm abduction above 90 degrees. - Injury results in **"winged scapula,"** making it difficult to raise the arm overhead, without sensory loss in the upper arm.

Q: A 16-year-old boy is brought to the emergency department after being tackled at a football game. Per his mom, he is the quarterback of his team and was head-butted in the left shoulder region by the opposing team. Shortly after, the mother noticed that his left arm was hanging by his torso and his hand was “bent backwards and facing the sky.” The patient denies head trauma, loss of consciousness, sensory changes, or gross bleeding. A physical examination demonstrates weakness in abduction, lateral rotation, flexion, and supination of the left arm and tenderness of the left shoulder region with moderate bruising. Radiograph of the left shoulder and arm is unremarkable. Which of the following is most likely damaged in this patient?

C5-C6 nerve roots. ***C5-C6 nerve roots*** - The "bent backwards and facing the sky" hand posture indicates **Waiter's tip position**, a classic sign of **Erb-Duchenne palsy**, caused by damage to the upper trunk of the brachial plexus (C5-C6 roots) [1]. - Weakness in **abduction** (deltoid, supraspinatus), **lateral rotation** (infraspinatus, teres minor), **flexion** (biceps, coracobrachialis), and **supination** (biceps, supinator) are all consistent with C5-C6 nerve root involvement. *Ulnar nerve* - Ulnar nerve damage would result in a **claw hand deformity** (hyperextension of MCP joints and flexion of DIP/PIP joints of 4th and 5th digits) and weakness in intrinsic hand muscles, not the observed upper arm weakness. - Sensory loss involves the medial hand and little finger. *C8-T1 nerve roots* - Damage to the C8-T1 nerve roots (lower trunk) typically results in **Klumpke's palsy**, characterized by a more severe **claw hand** and paralysis of intrinsic hand muscles [1]. - This presentation does not match the observed functional deficits. *Long thoracic nerve* - Injury to the long thoracic nerve causes paralysis of the **serratus anterior muscle**, leading to **scapular winging**, especially when pushing against a wall. - While possible in shoulder trauma, it does not explain the widespread weakness in abduction, rotation, flexion, and supination of the arm.

Q: Tendons in the 2nd compartment of wrist?

Extensor carpi radialis brevis and longus. ***Extensor carpi radialis brevis and longus*** - The **second dorsal compartment** of the wrist houses the tendons of the **extensor carpi radialis longus (ECRL)** and **extensor carpi radialis brevis (ECRB)** muscles [1]. - These muscles are primarily responsible for **wrist extension** and **radial deviation** of the hand [1]. *Extensor pollicis longus* - The **extensor pollicis longus (EPL)** tendon is located in the **third dorsal compartment** of the wrist [1]. - Its main function is to **extend the thumb's interphalangeal joint** and contributes to extension and adduction of the thumb. *Extensor pollicis brevis* - The **extensor pollicis brevis (EPB)** tendon is found in the **first dorsal compartment** of the wrist [1]. - It works with the abductor pollicis longus to form the **anatomical snuffbox** and primarily **extends the metacarpophalangeal joint** of the thumb [1]. *Abductor pollicis longus* - The **abductor pollicis longus (APL)** tendon is also located in the **first dorsal compartment** of the wrist [1]. - Its primary actions are to **abduct** (move away from the palm) and **extend the thumb** at the carpometacarpal joint [1].

Q: Which bone connects the sternum to the scapula?

Clavicle. ***Clavicle*** - The **clavicle**, or collarbone, is the only bone that directly connects the **axial skeleton** (via the sternum) to the **appendicular skeleton** (via the scapula). - It articulates medially with the **manubrium** of the sternum at the sternoclavicular joint and laterally with the **acromion** of the scapula at the acromioclavicular joint. *First rib* - The **first rib** articulates with the **manubrium** of the sternum but does not connect directly to the scapula. - Its primary role is to form part of the **thoracic cage**, protecting internal organs. *Manubrium* - The **manubrium** is the superior part of the **sternum** and articulates with the clavicles and the first two ribs. - It does not directly connect to the **scapula**; rather, the clavicle mediates this connection. *Second rib* - The **second rib** articulates with both the **manubrium** and the body of the sternum at the **sternal angle**. - Like the first rib, it is part of the **thoracic cage** and does not directly connect to the scapula.

Q: Which of the following structures passes through Guyon's canal?

Ulnar nerve. ### Ulnar nerve - The **ulnar nerve** passes through Guyon's canal, along with the ulnar artery, making it susceptible to compression here [1]. - Compression of the ulnar nerve in Guyon's canal can lead to motor and sensory deficits in its distribution, known as **ulnar tunnel syndrome** [1]. ### Flexor carpi radialis - The **flexor carpi radialis tendon** passes through a separate compartment in the carpal tunnel, distinct from Guyon's canal. - Its primary function is wrist flexion and radial deviation, and it is not associated with Guyon's canal. ### Radial nerve - The **radial nerve** courses along the lateral aspect of the forearm and hand and does not pass through Guyon's canal. - Its injury typically manifests as **wrist drop** and sensory loss over the dorsum of the hand. ### Median nerve - The **median nerve** passes through the carpal tunnel, which is medial to Guyon's canal in the wrist [1]. - Entrapment of the median nerve in the carpal tunnel causes **carpal tunnel syndrome**, characterized by symptoms in the thumb, index, middle, and radial half of the ring finger [1].

Q: Pointing index finger is seen in which nerve injury

Median. ***Median*** - The **pointing index finger** sign occurs in **proximal median nerve injury** when attempting to make a fist, as the median nerve supplies **flexor digitorum superficialis (FDS)** and lateral half of **flexor digitorum profundus (FDP)**. - This creates the classic **"hand of benediction"** or **"pope's blessing"** sign where index and middle fingers remain extended due to loss of flexion capability. *Axillary* - Primarily innervates the **deltoid** and **teres minor muscles**, affecting **shoulder abduction** and external rotation. - Injury does not cause any **finger positioning abnormalities** or hand deformities. *Radial* - Injury causes **"wrist drop"** with inability to extend the wrist, thumb, and fingers at **MCP joints**. - Results in all fingers remaining **flexed due to unopposed flexor action**, not a pointing finger deformity. *Ulnar* - Injury causes **"claw hand"** deformity primarily affecting the **ring and little fingers** (4th and 5th digits). - Creates **hyperextension at MCP joints** and **flexion at PIP/DIP joints**, with the index finger typically less affected.

Q: Winging of scapula is due to paralysis of

Serratus anterior. ***Serratus anterior*** - The **serratus anterior muscle** is responsible for **protraction and rotation of the scapula**, holding it close to the thoracic wall. - Paralysis of this muscle, often due to injury to the **long thoracic nerve**, causes the **medial border of the scapula** to protrude posteriorly, a condition known as **medial scapular winging**. - This is the **classic and most common cause** of scapular winging. *Rhomboid major* - The rhomboid major muscle primarily performs **retraction and downward rotation of the scapula**. - Paralysis of this muscle would lead to the scapula being displaced laterally and superiorly, not winging. *Trapezius* - The trapezius muscle has multiple actions, including **elevating, depressing, retracting, and rotating the scapula**. - Paralysis of the trapezius (e.g., due to **accessory nerve damage**) can cause **lateral scapular winging** where the inferior angle protrudes, along with shoulder drooping and difficulty shrugging. - However, **serratus anterior paralysis** is the classic answer for scapular winging in exam contexts. *Levator scapulae* - The levator scapulae muscle is primarily involved in **elevating and downwardly rotating the scapula**. - Dysfunction of this muscle would impair shoulder elevation but would not be the direct cause of scapular winging.

Q: The highlighted muscle is supplied by which nerve?

Musculocutaneous nerve. ***Musculocutaneous nerve*** - The **musculocutaneous nerve** innervates all three muscles in the **anterior compartment of the arm**: the biceps brachii, brachialis, and coracobrachialis. - The **biceps brachii** is a prominent muscle located in the anterior compartment of the arm, responsible for **flexion of the elbow** and **supination of the forearm**. *Median nerve* - The **median nerve** primarily innervates muscles in the **anterior compartment of the forearm** (except for the flexor carpi ulnaris and medial half of the flexor digitorum profundus) and some thenar muscles in the hand. - It does not supply any muscles in the anterior compartment of the arm. *Ulnar nerve* - The **ulnar nerve** innervates the **flexor carpi ulnaris** and the medial half of the **flexor digitorum profundus** in the forearm, as well as most intrinsic hand muscles. - It does not supply muscles of the anterior compartment of the arm. *Radial nerve* - The **radial nerve** innervates all muscles in the **posterior compartment of the arm** (triceps brachii) and forearm, which are primarily involved in **extension**. - It also has no role in innervating the muscles of the anterior compartment of the arm.

Question 1

A patient who has taken the first COVID vaccine comes for the second dose. An astute nurse noticed that the shoulder was flabby, flat, and was asymmetrical. There was an associated loss of contour of the shoulder joint. Injury to which of the structures might have resulted and was avoidable?

Accepted Answer

Deltoid muscle

Answer

Supraspinatus muscle

Answer

Infraspinatus muscle

Answer

Teres minor muscle

Question 2

A patient presents with difficulty extending their wrist following trauma to the posterior forearm. Which of the following muscles would be most affected by injury to the posterior interosseous nerve?

Accepted Answer

Extensor digitorum

Answer

Extensor carpi ulnaris

Answer

Extensor carpi radialis brevis

Answer

Extensor pollicis longus

Question 3

A 45-year-old woman undergoes a modified radical mastectomy for breast cancer. Following the procedure, she experiences numbness in the medial aspect of her upper arm. Which of the following nerves was most likely injured during the surgery?

Accepted Answer

Intercostobrachial nerve

Answer

Musculocutaneous nerve

Answer

Thoracodorsal nerve

Answer

Long thoracic nerve

Question 4

A 16-year-old boy is brought to the emergency department after being tackled at a football game. Per his mom, he is the quarterback of his team and was head-butted in the left shoulder region by the opposing team. Shortly after, the mother noticed that his left arm was hanging by his torso and his hand was “bent backwards and facing the sky.” The patient denies head trauma, loss of consciousness, sensory changes, or gross bleeding. A physical examination demonstrates weakness in abduction, lateral rotation, flexion, and supination of the left arm and tenderness of the left shoulder region with moderate bruising. Radiograph of the left shoulder and arm is unremarkable. Which of the following is most likely damaged in this patient?

Accepted Answer

C5-C6 nerve roots

Answer

Ulnar nerve

Answer

C8-T1 nerve roots

Answer

Long thoracic nerve

Question 5

Tendons in the 2nd compartment of wrist?

Accepted Answer

Extensor carpi radialis brevis and longus

Answer

Extensor pollicis longus

Answer

Extensor pollicis brevis

Answer

Abductor pollicis longus

Question 6

Which bone connects the sternum to the scapula?

Accepted Answer

Clavicle

Answer

First rib

Answer

Manubrium

Answer

Second rib

Question 7

Which of the following structures passes through Guyon's canal?

Accepted Answer

Ulnar nerve

Answer

Flexor carpi radialis

Answer

Radial nerve

Answer

Median nerve

Question 8

Pointing index finger is seen in which nerve injury

Accepted Answer

Median

Answer

Axillary

Answer

Radial

Answer

Ulnar

Question 9

Winging of scapula is due to paralysis of

Accepted Answer

Serratus anterior

Answer

Rhomboid major

Answer

Trapezius

Answer

Levator scapulae

Question 10

The highlighted muscle is supplied by which nerve?

Accepted Answer

Musculocutaneous nerve

Answer

Median nerve

Answer

Ulnar nerve

Answer

Radial nerve

Upper Limb — MCQs

Upper Limb — MCQs

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