Upper Limb

Upper Limb Indian Medical PG Question 1: What is true about the blood supply of the scaphoid bone?

• A. Mainly through the ulnar artery
• B. Major supply from the ventral surface
• C. Major supply from the dorsal surface (Correct Answer)
• D. Proximal supply in antegrade fashion

Upper Limb Explanation: The scaphoid is the most commonly fractured carpal bone [1], and its unique vascular anatomy is a high-yield topic for NEET-PG. [2] ### **Explanation of the Correct Answer** The scaphoid receives approximately **70–80% of its blood supply from the dorsal carpal branch of the radial artery**. These vessels enter the bone through the **dorsal ridge** (non-articular surface) and supply the proximal two-thirds of the bone via **retrograde flow**. This makes the dorsal surface the primary site of vascular entry. ### **Analysis of Incorrect Options** * **Option A:** The blood supply is derived almost exclusively from the **radial artery**, not the ulnar artery. * **Option B:** While some minor vessels enter the distal tubercle on the volar (ventral) side, the **major** supply is dorsal. * **Option C (Correct):** As stated, the dorsal carpal branch of the radial artery is the dominant source. * **Option D:** The blood supply to the proximal pole is **retrograde** (distal-to-proximal). There is no direct antegrade supply to the proximal pole, which is why it is highly susceptible to ischemia. [2] ### **Clinical Pearls for NEET-PG** * **Retrograde Blood Flow:** Because the vessels enter distally and travel proximally, a fracture at the **waist of the scaphoid** often severs the blood supply to the proximal fragment. [1] * **Avascular Necrosis (AVN):** The proximal pole is the most common site for AVN (Preiser’s disease is idiopathic AVN, but post-traumatic AVN is more common). [2] * **Anatomical Snuffbox:** Tenderness here is pathognomonic for a scaphoid fracture. * **Non-union:** Due to the precarious retrograde supply, scaphoid fractures have a high risk of non-union and delayed healing. [2]

Upper Limb Indian Medical PG Question 2: In ulnar nerve injury in the arm, all of the following are seen except?

• A. Hypothenar atrophy
• B. Adduction of thumb (Correct Answer)
• C. Loss of sensation of the medial one-third of the hand
• D. Claw hand

Upper Limb Explanation: **Explanation:** The ulnar nerve (C8-T1) is the "musician’s nerve," responsible for fine motor movements of the hand. To solve this question, one must understand the muscular innervation of the thumb. **Why "Adduction of thumb" is the correct answer:** The **Adductor Pollicis** muscle is innervated by the deep branch of the ulnar nerve [1]. In an ulnar nerve injury, this muscle is paralyzed, leading to a **loss of thumb adduction** [1]. Patients compensate for this loss by flexing the thumb at the interphalangeal joint (using the Flexor Pollicis Longus, innervated by the median nerve) when asked to grip a piece of paper—a clinical sign known as **Froment’s Sign**. Therefore, adduction is lost, not preserved. **Analysis of Incorrect Options:** * **Hypothenar atrophy:** The ulnar nerve supplies the hypothenar muscles (Abductor, Flexor, and Opponens digiti minimi). Denervation leads to visible wasting of the medial palm. * **Loss of sensation (medial 1/3):** The ulnar nerve provides sensory innervation to the medial one and a half fingers and the corresponding medial third of the palm and dorsum of the hand. * **Claw hand:** This occurs due to paralysis of the medial two lumbricals and all interossei [1]. This leads to hyperextension at the MCP joints and flexion at the IP joints of the 4th and 5th digits. **High-Yield Clinical Pearls for NEET-PG:** * **Ulnar Paradox:** A high lesion (at the elbow) results in a *less* prominent clawing than a low lesion (at the wrist) because the Flexor Digitorum Profundus (medial half) is also paralyzed in high lesions, reducing the flexion at the IP joints. * **Innervation Rule:** The ulnar nerve supplies all intrinsic muscles of the hand **except** the "LOAF" muscles (Lateral two lumbricals, Opponens pollicis, Abductor pollicis brevis, Flexor pollicis brevis), which are supplied by the Median nerve [1].

Upper Limb Indian Medical PG Question 3: What is true about the pectoralis major muscle?

• A. It is an abductor and internal rotator of the shoulder.
• B. Its blood supply is by the perforating branch of the internal thoracic artery.
• C. Its blood supply is by the thoracoacromial artery. (Correct Answer)
• D. Its nerve supply is by the intercostal artery.

Upper Limb Explanation: ### Explanation **1. Why Option C is Correct:** The **pectoralis major** is a large, fan-shaped muscle of the anterior chest wall. Its primary arterial supply is the **thoracoacromial artery** (specifically its pectoral branch), which is a branch of the second part of the axillary artery. Additional supply comes from the lateral thoracic artery. **2. Why the Other Options are Incorrect:** * **Option A:** The pectoralis major is an **adductor** and **medial (internal) rotator** of the humerus, not an abductor. Its clavicular head also helps in the flexion of the humerus. * **Option B:** While the internal thoracic artery provides some minor supply via its perforating branches, the **dominant** and primary blood supply is the thoracoacromial artery. In surgical contexts (like the PMMC flap), the thoracoacromial artery is the definitive pedicle. * **Option D:** The nerve supply of the pectoralis major is derived from the **medial and lateral pectoral nerves** (C5–T1), which arise from the brachial plexus [1]. The intercostal nerves supply the skin and intercostal muscles, not the pectoralis major [1]. **3. High-Yield Clinical Pearls for NEET-PG:** * **Dual Nerve Supply:** It is one of the few muscles supplied by both the medial and lateral pectoral nerves (named based on their origin from the cords of the brachial plexus) [1]. * **Poland Syndrome:** A congenital condition characterized by the unilateral absence of the pectoralis major, often associated with syndactyly. * **Surgical Flap:** The Pectoralis Major Myocutaneous (PMMC) flap is a "workhorse" flap in reconstructive head and neck surgery, based on the **pectoral branch of the thoracoacromial artery**. * **Insertion:** It inserts into the **lateral lip of the bicipital groove** of the humerus. (Mnemonic: "A Lady between two Majors" — Latissimus dorsi in the floor, Pectoralis major on the lateral lip, and Teres major on the medial lip).

Upper Limb Indian Medical PG Question 4: Loss of extension of the little finger and hypothenar atrophy are seen in an injury of which nerve?

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

Upper Limb Explanation: **Explanation:** The **ulnar nerve** is the primary motor nerve of the hand. The clinical presentation described—loss of extension of the little finger and hypothenar atrophy—is characteristic of a distal ulnar nerve lesion (e.g., at the wrist/Guyon’s canal) [1]. 1. **Why Ulnar Nerve is correct:** * **Hypothenar Atrophy:** The ulnar nerve supplies the three hypothenar muscles (Abductor digiti minimi, Flexor digiti minimi brevis, and Opponens digiti minimi) [1]. Injury leads to visible wasting of the medial palm. * **Loss of Extension:** While the Radial nerve extends the MCP joints, the **lumbricals and interossei** (supplied by the ulnar nerve) are responsible for extending the Interphalangeal (IP) joints [1]. Loss of the 3rd and 4th lumbricals leads to the "ulnar claw hand," where the patient cannot fully extend the IP joints of the little finger. 2. **Why other options are incorrect:** * **Posterior Interosseous Nerve (PIN):** While the PIN supplies the Extensor Digitorum and Extensor Digiti Minimi (responsible for MCP extension), it does **not** supply the hypothenar muscles. PIN injury causes "finger drop" but no sensory loss or hypothenar wasting [1]. * **Radial Trunk:** High radial nerve injury causes "wrist drop" and loss of extension at the MCP joints, but the hypothenar eminence remains intact [1]. * **Median Nerve:** This nerve supplies the thenar muscles (LOAF). Injury leads to "Ape thumb" deformity and thenar atrophy, not hypothenar [1]. **NEET-PG High-Yield Pearls:** * **Ulnar Paradox:** A lesion at the wrist causes more prominent clawing than a lesion at the elbow because the FDP (medial half) remains intact, increasing the flexion deformity at the IP joints. * **Froment’s Sign:** Tests for adductor pollicis (ulnar nerve) palsy; the patient compensates by flexing the FPL (median nerve). * **Wartenberg’s Sign:** Abduction of the little finger due to unopposed action of EDM (radial nerve) when palmar interossei (ulnar nerve) are paralyzed.

Upper Limb Indian Medical PG Question 5: In Erb's palsy, what is the typical position of the affected limb?

• A. Extended, laterally rotated, pronated
• B. Extended, laterally rotated, supinated
• C. Extended, medially rotated, pronated (Correct Answer)
• D. Extended, medially rotated, supinated

Upper Limb Explanation: ### Explanation **Erb’s Palsy** (Waiter’s Tip or Policeman’s Tip deformity) results from an injury to the **upper trunk of the brachial plexus (C5-C6)**, most commonly due to birth trauma or a fall on the shoulder [1]. #### Why Option C is Correct: The deformity is caused by the loss of function in specific muscle groups, leading the limb to take a position dictated by the unopposed action of the surviving muscles: 1. **Extended Elbow:** Loss of the **Biceps brachii** and **Brachialis** (flexors). 2. **Medially Rotated Arm:** Loss of the **Supraspinatus** and **Infraspinatus** (lateral rotators), leaving the subscapularis and pectoralis major unopposed. 3. **Pronated Forearm:** Loss of the **Biceps brachii** (the powerful supinator) and **Supinator** muscle. 4. **Adducted Shoulder:** Loss of the **Deltoid** and **Supraspinatus** (abductors). #### Why Other Options are Incorrect: * **Options A & B (Laterally rotated):** Incorrect because the lateral rotators (Infraspinatus/Teres minor) are paralyzed; the arm is pulled medially by the intact subscapularis. * **Options B & D (Supinated):** Incorrect because the primary supinator (Biceps) is paralyzed; the forearm remains fixed in pronation. #### High-Yield Clinical Pearls for NEET-PG: * **Site of Injury:** **Erb’s Point** (junction of 6 nerves: C5, C6 roots; Suprascapular n.; N. to Subclavius; Anterior and Posterior divisions of the upper trunk). * **Nerves Involved:** Suprascapular nerve, Axillary nerve, and Musculocutaneous nerve [1]. * **Sensory Loss:** A small area of anesthesia over the **lower part of the deltoid** (regimental badge area). * **Reflexes:** The **Biceps and Supinator reflexes** are characteristically lost. * **Contrast:** Compare with **Klumpke’s Paralysis (C8-T1)**, which presents with a "Claw Hand" and potential Horner’s Syndrome.

Upper Limb Flashcard 1 of 5

Question: A lesion to the #_____ cord would result in wrist drop, paralysis of the deltoid, and impairment of internal rotation of the humerus

Answer: 3 - posterior

Upper Limb Flashcard 2 of 5

Question: The space marked is the upper triangular space and the _____ artery is a content of it.

Answer: circumflex scapular

Upper Limb Flashcard 3 of 5

Question: The structure marked as "X" in the given image is formed by the 1st lumbrical, _____ dorsal interossei and _____ palmar interossei

Answer: 1st

Upper Limb Flashcard 4 of 5

Question: A lesion to #_____ would result in "Saturday night palsy" (wrist drop).

Answer: 6 (radial nerve injury)

Upper Limb Flashcard 5 of 5

Question: The marked structure is the _____ nerve.

Answer: musculocutaneous