Clinicals

Question 1

Why does supracondylar fracture of the humerus lead to Volkmann’s ischemic contracture?

Answer 1

A supracondylar fracture of the humerus can lead to Volkmann’s ischemic contracture due to damage to the blood supply to the forearm muscles and the nerve structures, particularly the brachial artery and median nerve, which run close to the fracture site.

Mechanism:
1. Compartment Syndrome: The fracture can lead to swelling and increased pressure within the forearm muscle compartments, particularly in the flexor compartment, where the brachial artery and median nerve are located.
2. Blood Flow Obstruction: Swelling or direct injury can compromise the brachial artery, reducing blood flow to the muscles of the forearm and hand.
3. Ischemia: Lack of adequate blood supply (ischemia) leads to muscle necrosis and fibrosis, causing muscle shortening and contractures.
4. Nerve Damage: The median nerve may also be compressed, contributing to motor and sensory deficits in the hand, which further leads to the characteristic claw-like deformity of the fingers.

Question 2

Anatomical Basis of Carpal Tunnel Syndrome

Answer 2

Carpal Tunnel Syndrome (CTS) occurs due to compression of the median nerve as it passes through the carpal tunnel at the wrist. The anatomical basis of CTS involves the following factors:

1. Carpal Tunnel Structure:
   • The carpal tunnel is a narrow passage formed by the flexor retinaculum (transverse carpal ligament) on the top and the carpal bones (scaphoid, lunate, trapezium, pisiform, and hamate) on the bottom.
   • It contains the median nerve and tendons of the flexor muscles (flexor digitorum superficialis, flexor digitorum profundus, and flexor pollicis longus).
2. Median Nerve Compression:
   • The median nerve can be compressed due to increased pressure within the carpal tunnel, which may result from inflammation of tendons (e.g., tendinitis), swelling (due to pregnancy, fluid retention, or other conditions), or repetitive movements of the wrist.
   • This compression leads to symptoms like pain, numbness, tingling, and weakness in the hand, particularly affecting the thumb, index, and middle fingers.
3. Risk Factors:
   • Repetitive wrist movements, inflammatory conditions (e.g., rheumatoid arthritis), trauma, diabetes, and pregnancy can increase the risk of developing CTS by exacerbating swelling or thickening of the flexor tendons or the flexor retinaculum.

Question 3

Why does rupture of the long head of biceps cause popeye deformity?

Answer 3

The rupture of the long head of the biceps causes the Popeye deformity due to the following anatomical mechanism:

1. Anatomy of the Biceps:
   • The long head of the biceps originates from the supraglenoid tubercle of the scapula and runs through the intertubercular groove of the humerus before inserting at the radial tuberosity.
   • The short head of the biceps originates from the coracoid process and remains relatively unaffected in the case of a long head rupture.
2. Effect of Rupture:
   • When the long head of the biceps ruptures (often due to sudden forceful contraction), the muscle belly shortens and gathers in the upper arm, creating a bulge in the lower part of the arm. This bulge resembles a Popeye (cartoon character) appearance.
   • The short head of the biceps remains intact and continues to contract normally, but it causes the biceps muscle to deform by pulling the muscle into a lump or ball.
3. Muscle Function:
   • While the rupture of the long head does not significantly impair the function of the biceps (since the short head still helps in elbow flexion), it leads to visible muscle deformity in the upper arm.

Question 4

Clinical importance of anatomical snuff box in diagnosing scaphoid fractures.

Answer 4

The anatomical snuff box is clinically important in diagnosing scaphoid fractures due to its location and the structures it contains. The key points are:

1. Anatomical Location:
   • The anatomical snuff box is a triangular depression on the lateral side of the wrist, formed by the tendons of the extensor pollicis longus (EPL) and extensor pollicis brevis (EPB) on the sides, and the scaphoid bone forms the floor of the box.
2. Scaphoid Fracture Detection:
   • A scaphoid fracture commonly occurs after a fall onto an outstretched hand, and it can be difficult to detect on initial X-rays, especially in the early stages.
   • Pain and tenderness in the anatomical snuff box, particularly with palpation, are strong indicators of a potential scaphoid fracture, as the fracture disrupts the normal anatomical relationship of the scaphoid.
3. Complications of Scaphoid Fracture:
   • The scaphoid has a limited blood supply, which can lead to avascular necrosis if the fracture affects the blood flow to the bone, especially fractures in the proximal part of the scaphoid.
   • Early diagnosis is crucial to prevent long-term complications such as arthritis or chronic pain.
4. Clinical Examination:
   • Tenderness in the anatomical snuff box, often combined with pain on wrist movement, is a key sign that leads clinicians to suspect a scaphoid fracture, prompting further investigation (e.g., repeat X-rays, MRI, or CT).

Question 5

Why does subacromial bursitis cause pain during shoulder abduction?

Answer 5

Subacromial bursitis causes pain during shoulder abduction due to the following mechanisms:

1. Location of the Subacromial Bursa:
   • The subacromial bursa is located between the acromion (part of the scapula) and the rotator cuff tendons, particularly the supraspinatus tendon.
   • The bursa helps reduce friction between the acromion and the tendons of the rotator cuff, allowing smooth shoulder movement.
2. Inflammation of the Bursa:
   • In bursitis, the subacromial bursa becomes inflamed and swollen, which increases pressure in the area.
   • This inflammation causes pain, especially during shoulder movements that involve compression of the bursa, such as abduction.
3. Abduction and Compression:
   • During shoulder abduction, the humeral head moves upward, bringing it closer to the acromion.
   • If the subacromial bursa is inflamed, this motion causes impingement and increased pressure on the bursa, leading to pain.

Question 6

Explain the anatomical basis of tennis elbow, lateral epicondylitis

Answer 6

Tennis elbow (lateral epicondylitis) is an overuse injury characterized by inflammation of the extensor tendons of the forearm, primarily the extensor carpi radialis brevis (ECRB) tendon, where it attaches to the lateral epicondyle of the humerus.

Anatomical Basis:
1. Location of Injury:
• The lateral epicondyle is the bony prominence on the outer side of the elbow, where the tendons of the extensor muscles of the forearm, including the ECRB, extensor carpi radialis longus (ECRL), and extensor digitorum, insert.
2. Repetitive Stress:
• Tennis elbow occurs due to repetitive wrist extension and forearm supination, causing microtears and inflammation at the origin of these tendons on the lateral epicondyle.
• Activities such as gripping, lifting, or repetitive motions (e.g., tennis strokes, manual labor) stress the extensor muscles, leading to tendon degeneration and pain.
3. Pathophysiology:
• The constant stress leads to degenerative changes in the tendons, often termed as tendinosis, which involves microtears and increased collagen production in the tendon, rather than true inflammation.
4. Symptoms:
• Pain over the lateral epicondyle, particularly with wrist extension or gripping. The pain often radiates down the forearm.

Question 7

How does the cubital tunnel syndrome affect the ulnar nerve?

Answer 7

Cubital Tunnel Syndrome occurs when the ulnar nerve is compressed or irritated as it passes through the cubital tunnel, a narrow passageway located on the medial side of the elbow, formed by the medial epicondyle of the humerus, the ulnar collateral ligament, and the flexor carpi ulnaris tendon.

1. Anatomical Location:
   • The cubital tunnel is located behind the medial epicondyle of the humerus. The ulnar nerve passes through this tunnel and can become compressed due to factors such as prolonged elbow flexion, trauma, or anatomical variations like elbow deformities.
2. Compression Mechanisms:
   • Prolonged flexion of the elbow (e.g., sleeping with the elbow bent) can stretch or compress the ulnar nerve.
   • Repetitive stress or trauma to the elbow, or bony spurs, can lead to narrowing of the tunnel and increased pressure on the nerve.
   • Swelling or inflammation in the area can also compress the nerve.
3. Symptoms:
   • Numbness and tingling in the ring and little fingers (ulnar distribution).
   • Weakness in the hand, especially affecting grip strength and the ability to perform fine motor tasks like typing or buttoning clothes.
   • Pain along the inner aspect of the elbow and forearm, particularly when the elbow is flexed.
4. Effect on the Ulnar Nerve:
   • The ulnar nerve innervates most of the intrinsic hand muscles, including those responsible for fine motor movements and grip strength, so compression of the nerve can lead to muscle weakness and atrophy, especially in the hypothenar muscles and lumbricals of the fourth and fifth fingers.

Question 8

How does Erb’s Palsy affect upper limb movements and sensation?

Answer 8

Erb’s Palsy is a neurological condition caused by injury to the upper trunk of the brachial plexus (C5-C6 roots), which can occur during difficult childbirth or trauma. This injury primarily affects the motor and sensory functions of the upper limb, leading to characteristic signs and symptoms.

1. Motor Effects:
   • Weakness or paralysis of the muscles innervated by the affected nerve roots, including:
   • Deltoid (C5) – leading to weakness or inability to abduct the shoulder.
   • Biceps (C5-C6) – causing weakness in elbow flexion.
   • Brachioradialis (C5-C6) – affecting forearm reflexes and pronation.
   • Supraspinatus and infraspinatus (C5-C6) – impairing shoulder external rotation.
   • The classic position of the arm in Erb’s Palsy is known as the “waiter’s tip” deformity, where the arm is held in:
   • Adduction, extension, and pronation (because of loss of external rotation and abduction).
2. Sensory Effects:
   • Loss of sensation in areas innervated by the C5-C6 dermatomes, which include:
   • Lateral side of the upper arm, forearm, and part of the hand (thumb and index fingers).
   • Tingling or numbness may also be present in these areas.
3. Cause:
   • Erb’s Palsy typically occurs when there is excessive stretching or tearing of the brachial plexus during difficult delivery (e.g., shoulder dystocia) or from trauma like falls or accidents, causing damage to the C5 and C6 nerve roots.