Question 1: Scaphoid Fracture
Stem: A 22-year-old man presents to the emergency department with wrist pain after a fall on his outstretched hand (FOOSH). He has focal tenderness in the anatomical snuffbox. Initial scaphoid-view radiographs are reported as normal.
Question: What is the most appropriate next step in management to definitively rule out an occult fracture?
(A) Repeat radiographs in 10-14 days. (B) CT scan of the wrist. (C) MRI scan of the wrist. (D) Radionuclide bone scan. (E) Immobilise in a cast and discharge with no follow-up.
Correct Answer: (C) MRI scan of the wrist.
Explanation:
- Why (C) is correct: MRI is the gold standard for diagnosing occult scaphoid fractures. It has near 100% sensitivity and specificity and can detect a fracture (as a T1-dark/T2-bright line with marrow oedema) within 24-48 hours. It also has the added benefit of assessing for ligamentous injury (e.g., SLAP tear) and early avascular necrosis.
- Why (A) is wrong: This is a traditional approach, but it delays the diagnosis. The fracture only becomes visible after 10-14 days due to bony resorption at the fracture site, and it is still less sensitive than MRI.
- Why (B) is wrong: CT is excellent for characterising a known fracture (showing displacement, comminution) and is very good at finding occult fractures, but it is less sensitive than MRI in the hyperacute phase and involves ionising radiation.
- Why (D) is wrong: A bone scan is sensitive (will be “hot”) but is non-specific (can be hot from contusion or arthritis), involves significant radiation, and is not a first-line investigation.
- Why (E) is wrong: Discharging without follow-up for a clinically suspected scaphoid fracture is negligent due to the high risk of non-union and avascular necrosis.
Key Points: Occult Scaphoid Fracture
- Clinical Suspicion > Radiograph: Always treat for a fracture (immobilise) if there is clinical snuffbox tenderness, even if X-rays are normal.
- Blood Supply: The scaphoid has a tenuous, retrograde blood supply from the distal pole. This makes the proximal pole highly vulnerable to avascular necrosis (AVN).
- Imaging: MRI is the most sensitive and specific modality for diagnosis, prognostication (AVN), and assessing associated ligament injuries.
Question 2: Scaphoid Avascular Necrosis (AVN)
Stem: A 30-year-old man presents with chronic wrist pain 8 months after an untreated scaphoid waist fracture. A new radiograph demonstrates that the proximal pole of the scaphoid is sclerotic and has fragmented.
Question: This radiographic appearance is most characteristic of:
(A) Fracture non-union. (B) Avascular necrosis (AVN). (C) Osteoarthritis. (D) Chondrocalcinosis. (E) Preiser’s disease.
Correct Answer: (B) Avascular necrosis (AVN).
Explanation:
- Why (B) is correct: Sclerosis (increased density) of the proximal pole following a scaphoid fracture is the classic radiographic sign of avascular necrosis. The dead bone does not participate in the hyperaemic resorption of normal healing and thus appears relatively dense. Fragmentation and collapse follow.
- Why (A) is wrong: Non-union (failure to heal) is present, but the sclerosis is the specific sign of AVN, which is the underlying cause of the non-union.
- Why (C) is wrong: Osteoarthritis (joint space narrowing, osteophytes) is a consequence of AVN and non-union (known as SLAC – Scapholunate Advanced Collapse), but it is not the primary finding.
- Why (D) is wrong: Chondrocalcinosis is calcification of the cartilage (e.g., TFCC), not sclerosis of the bone.
- Why (E) is wrong: Preiser’s disease is a rare spontaneous avascular necrosis of the scaphoid, not one caused by a fracture.
Key Points: Scaphoid AVN
- Cause: Interruption of the retrograde blood supply, most common with proximal pole and displaced waist fractures.
- Radiographic Signs: Persistent fracture line (non-union), sclerosis of the proximal pole, fragmentation, and eventual collapse.
- MRI: The most sensitive tool; shows lack of enhancement of the proximal pole on post-contrast T1 images.
Question 3: Distal Radius Fracture (Colles’)
Stem: An 80-year-old woman with osteoporosis falls on her outstretched hand. An X-ray of her wrist reveals an extra-articular fracture of the distal radius with dorsal angulation and dorsal displacement of the distal fragment.
Question: What is the eponym for this fracture pattern?
(A) Colles’ fracture (B) Smith’s fracture (C) Barton’s fracture (D) Chauffeur’s fracture (E) Galeazzi fracture
Correct Answer: (A) Colles’ fracture.
Explanation:
- Why (A) is correct: A Colles’ fracture is the most common distal radius fracture, classically described as an extra-articular fracture with dorsal angulation and dorsal displacement of the distal fragment. This results in the “dinner fork” deformity.
- Why (B) is wrong: A Smith’s fracture is the opposite, with volar angulation of the distal fragment, typically from a fall on a flexed wrist (a “garden spade” deformity).
- Why (C) is wrong: A Barton’s fracture is an intra-articular fracture of the dorsal or volar rim of the distal radius.
- Why (D) is wrong: A Chauffeur’s (or Hutchinson’s) fracture is an intra-articular fracture of the radial styloid.
- Why (E) is wrong: A Galeazzi fracture is a fracture of the radial shaft with an associated dislocation of the distal radioulnar joint (DRUJ).
Key Points: Distal Radius Fractures
- Colles’: Dorsal angulation. Mechanism: FOOSH.
- Smith’s: Volar angulation. Mechanism: Fall on flexed wrist.
- Barton’s: Intra-articular rim fracture (dorsal or volar).
- Chauffeur’s: Radial styloid fracture.
Question 4: Kienböck’s Disease
Stem: A 28-year-old male carpenter presents with several months of chronic, central wrist pain and weakness. A plain radiograph demonstrates increased density (sclerosis) and early collapse of the lunate bone. The patient is also noted to have a negative ulnar variance.
Question: What is the most likely diagnosis?
(A) Scaphoid non-union (B) Ulnar impaction syndrome (C) Kienböck’s disease (D) Preiser’s disease (E) Intraosseous ganglion
Correct Answer: (C) Kienböck’s disease.
Explanation:
- Why (C) is correct: Kienböck’s disease is avascular necrosis (AVN) of the lunate. The classic radiographic finding is increased sclerosis, followed by fragmentation, collapse, and secondary osteoarthritis.
- Why (A) is wrong: This involves the scaphoid, not the lunate.
- Why (B) is wrong: Ulnar impaction syndrome is associated with positive ulnar variance (a long ulna), which impacts the lunate. This patient has negative ulnar variance (a short ulna), which is a known risk factor for Kienböck’s.
- Why (D) is wrong: Preiser’s disease is AVN of the scaphoid.
- Why (E) is wrong: An intraosseous ganglion would appear as a simple, well-defined lytic lesion, not a sclerotic, collapsed bone.
Key Points: Kienböck’s Disease
- Definition: Avascular necrosis of the lunate.
- Associations: Strongly associated with negative ulnar variance (a relatively short ulna), which is thought to increase shear stress on the lunate.
- Imaging: Sclerosis of the lunate is the earliest sign, followed by fracture, fragmentation, and collapse (Lichtman classification).
Question 5: Rotator Cuff Tear
Stem: A 65-year-old man presents with chronic right shoulder pain and weakness, particularly when abducting his arm. A coronal T2-weighted MRI of the shoulder is performed.
Question: Which of the following findings is the most specific sign of a full-thickness tear of the supraspinatus tendon?
(A) High signal within the tendon substance on a T1-weighted image. (B) A small amount of fluid in the subacromial-subdeltoid bursa. (C) A high-signal (fluid) gap extending from the articular surface to the bursal surface of the tendon. (D) Atrophy and fatty infiltration of the supraspinatus muscle belly. (E) A down-sloping acromion.
Correct Answer: (C) A high-signal (fluid) gap extending from the articular surface to the bursal surface of the tendon.
Explanation:
- Why (C) is correct: This is the definition of a full-thickness tear on T2/PD fat-sat images. A high-signal “gap” (fluid) fills the defect, connecting the articular side (glenohumeral joint) with the bursal side (subacromial-subdeltoid bursa).
- Why (A) is wrong: Signal on T1 is not used; high signal on T2 within the tendon (not a full gap) is tendinosis or a partial tear.
- Why (B) is wrong: Bursal fluid is a non-specific sign of inflammation and is seen with tendinosis, partial tears, and impingement.
- Why (D) is wrong: Fatty atrophy (Goutallier classification) is a sign of a chronic full-thickness tear, but (C) is the direct sign of the tear itself.
- Why (E) is wrong: A down-sloping acromion is a cause of impingement, which is a risk factor for a tear, not the tear itself.
Key Points: Rotator Cuff Tear (MRI)
- Partial Tear: High-signal defect on the articular or bursal surface, but not communicating through.
- Full-Thickness Tear: High-signal fluid-filled gap on T2-weighted images communicating from the articular to the bursal surface.
- Chronic Signs: Tendon retraction, muscle atrophy, and fatty infiltration.
Question 6: Anterior Shoulder Dislocation
Stem: A 20-year-old rugby player presents with severe shoulder pain after a tackle. His arm is held in abduction and external rotation. A post-reduction CT scan shows an impaction fracture of the posterolateral humeral head and an avulsion fracture of the anteroinferior glenoid rim.
Question: What are the correct eponyms for these two injuries, respectively?
(A) Hill-Sachs lesion and Bankart lesion. (B) Bankart lesion and Hill-Sachs lesion. (C) Reverse Hill-Sachs lesion and Reverse Bankart lesion. (D) SLAP lesion and Bankart lesion. (E) Hill-Sachs lesion and SLAP lesion.
Correct Answer: (A) Hill-Sachs lesion and Bankart lesion.
Explanation:
- Why (A) is correct: This is the classic “lesion pair” for anterior glenohumeral instability.
- Hill-Sachs Lesion: The impaction fracture on the posterolateral humeral head, which occurs as it impacts against the glenoid rim during dislocation.
- Bankart Lesion: The injury to the anteroinferior glenoid labrum. When this includes a bone fragment (as in this stem), it is a “Bony Bankart.”
- Why (B) is wrong: The order is incorrect based on the stem.
- Why (C) is wrong: “Reverse” lesions (Reverse Hill-Sachs, Reverse Bankart) are associated with posterior shoulder dislocations.
- Why (D) & (E) are wrong: A SLAP (Superior Labrum Anterior-Posterior) lesion is an injury to the superior labrum, not the anteroinferior rim.
Key Points: Anterior Shoulder Dislocation
- Mechanism: Forced abduction, external rotation, and extension.
- Hill-Sachs Lesion: Impaction fracture of the posterolateral humeral head.
- Bankart Lesion: Injury to the anteroinferior labrum.
- Bony Bankart: A Bankart lesion that includes a fracture of the glenoid rim.
Question 7: Posterior Shoulder Dislocation
Stem: A 45-year-old man is brought to the ED after a generalised tonic-clonic seizure. He has severe shoulder pain. The AP radiograph shows the humeral head is fixed in internal rotation, giving it a “lightbulb” appearance.
Question: What is the most likely diagnosis?
(A) Anterior shoulder dislocation. (B) Posterior shoulder dislocation. (C) Adhesive capsulitis. (D) Proximal humerus fracture. (E) Rotator cuff tear.
Correct Answer: (B) Posterior shoulder dislocation.
Explanation:
- Why (B) is correct: Posterior dislocations are rare (2-5% of all shoulder dislocations) and are famously “missed” on initial AP X-rays. The classic causes are the “3 E’s”: Epileptic seizure, Electric shock, or Extreme trauma. The “lightbulb sign” is caused by the humeral head being fixed in internal rotation, making the tuberosities disappear and the head appear round.
- Why (A) is wrong: An anterior dislocation is usually obvious, with the humeral head displaced inferiorly and medially (subcoracoid).
- Why (C) is wrong: Adhesive capsulitis (“frozen shoulder”) is a clinical diagnosis of restricted movement; X-rays are normal.
- Why (D) is wrong: A fracture may be present, but the “lightbulb” sign is specific to the dislocation.
- Why (E) is wrong: A rotator cuff tear is a soft-tissue injury, not a dislocation.
Key Points: Posterior Shoulder Dislocation
- Classic Causes: Seizure, electrocution, trauma.
- AP X-ray Signs:
- “Lightbulb Sign”: Humeral head fixed in internal rotation.
- “Trough Sign”: A vertical line of sclerosis on the medial humeral head, which is the reverse Hill-Sachs lesion (an impaction fracture of the anteromedial humeral head).
- Definitive View: An axillary view or CT will confirm the posterior displacement.
Question 8: Radial Head Fracture (Fat Pads)
Stem: An adult patient falls on an outstretched hand and presents with a painful, swollen elbow. The lateral radiograph demonstrates an elevated anterior fat pad (the “sail sign”) and a visible posterior fat pad. No distinct fracture line is seen.
Question: This combination of findings is presumptive evidence of what occult injury?
(A) Olecranon fracture. (B) Supracondylar fracture. (C) Lateral epicondylitis. (D) Radial head fracture. (E) Normal elbow.
Correct Answer: (D) Radial head fracture.
Explanation:
- Why (D) is correct: In an adult, the presence of a joint effusion (indicated by the fat pad signs) after a FOOSH is considered a radial head fracture until proven otherwise. The posterior fat pad is always abnormal, as it sits deep within the olecranon fossa and is only visible when an effusion pushes it out.
- Why (A) is wrong: An olecranon fracture is usually obvious and displaced.
- Why (B) is wrong: A supracondylar fracture is the most common occult fracture in children with an elbow effusion, but in adults, it is the radial head.
- Why (C) is wrong: This is a soft-tissue overuse injury and would not cause a joint effusion.
- Why (E) is wrong: A visible posterior fat pad is never normal.
Key Points: Elbow Fat Pads
- Anterior Fat Pad: A small sliver may be normal. When elevated by an effusion, it looks like a “sail.”
- Posterior Fat Pad: Never visible on a normal lateral X-ray. Its presence always indicates a joint effusion.
- Effusion in Adult: Most likely an occult radial head fracture.
- Effusion in Child: Most likely an occult supracondylar fracture.
Question 9: Supracondylar Fracture (Child)
Stem: A 6-year-old boy falls from a climbing frame onto his outstretched hand. A lateral elbow radiograph shows a joint effusion. The anterior humeral line is drawn and is noted to pass anterior to the capitellum.
Question: What is the most likely diagnosis?
(A) Pulled elbow (radial head subluxation). (B) Supracondylar fracture. (C) Lateral condyle fracture. (D) Normal elbow with effusion. (E) Medial epicondyle fracture.
Correct Answer: (B) Supracondylar fracture.
Explanation:
- Why (B) is correct: The anterior humeral line (AHL) is a key tool for assessing paediatric elbows. It is a line drawn down the anterior cortex of the humerus, which should transect the middle third of the capitellum. In a (typically posterior-displaced) supracondylar fracture, the distal fragment is displaced, and the AHL passes anterior to the capitellum.
- Why (A) is wrong: A pulled elbow is a clinical diagnosis and has normal radiographs.
- Why (C) is wrong: A lateral condyle fracture (the 2nd most common) would show a fracture line through the lateral condyle (a Salter-Harris IV).
- Why (D) is wrong: The abnormal AHL proves this is more than just an effusion.
- Why (E) is wrong: This is an avulsion fracture, often seen in “Little League elbow.”
Key Points: Supracondylar Fracture
- Most common paediatric elbow fracture.
- Key Sign: Abnormal anterior humeral line.
- Complication: High risk of vascular injury (brachial artery) and nerve injury (median nerve), which is a surgical emergency.
Question 10: Bennett’s Fracture
Stem: A 23-year-old man punched a wall and now has severe pain at the base of his thumb. A radiograph reveals a two-part, intra-articular fracture of the base of the first metacarpal. A small ulnar fragment remains attached to the trapezium, while the main metacarpal shaft is displaced radially and dorsally.
Question: What is the eponym for this unstable fracture-dislocation?
(A) Bennett’s fracture (B) Rolando’s fracture (C) Boxer’s fracture (D) Gamekeeper’s thumb (E) Chauffeur’s fracture
Correct Answer: (A) Bennett’s fracture.
Explanation:
- Why (A) is correct: A Bennett’s fracture is a two-part intra-articular fracture of the base of the thumb (1st metacarpal). It is unstable because the pull of the abductor pollicis longus (APL) tendon displaces the large fragment, while the small fragment is held by the volar beak ligament.
- Why (B) is wrong: A Rolando’s fracture is also an intra-articular fracture of the 1st metacarpal base, but it is comminuted (3 or more parts), typically in a “T” or “Y” shape.
- Why (C) is wrong: A Boxer’s fracture is a fracture of the 5th metacarpal neck.
- Why (D) is wrong: A Gamekeeper’s (or Skier’s) thumb is an avulsion or tear of the ulnar collateral ligament (UCL) of the thumb’s MCP joint.
- Why (E) is wrong: This is a fracture of the radial styloid.
Key Points: Thumb Base Fractures
- Bennett’s: 2-part, intra-articular, unstable.
- Rolando’s: 3+ parts (comminuted), intra-articular, unstable.
Question 11: AC Joint Injury
Stem: A 28-year-old cyclist falls directly onto the tip of his shoulder. A radiograph shows that the acromioclavicular (AC) joint is widened and the coracoclavicular (CC) distance is 18 mm (normal < 13 mm), with the clavicle visibly elevated above the acromion.
Question: This degree of injury implies tearing of which ligaments?
(A) Acromioclavicular ligament only. (B) Coracoclavicular ligament only. (C) Acromioclavicular and Coracoclavicular ligaments. (D) Coracoacromial ligament. (E) Glenohumeral ligaments.
Correct Answer: (C) Acromioclavicular and Coracoclavicular ligaments.
Explanation:
- Why (C) is correct: This describes a Rockwood Type III (or V) injury. Widening of the AC joint implies rupture of the AC ligament (Type II). Elevation of the entire clavicle, with widening of the CC distance, implies rupture of the coracoclavicular ligaments (the conoid and trapezoid) as well.
- Why (A) is wrong: Tearing the AC ligament only (Type II) would widen the AC joint, but the CC distance would be normal.
- Why (B) is wrong: This is an unstable injury, and the AC ligament would almost certainly be torn as well.
- Why (D) is wrong: The coracoacromial ligament is superior and not involved in this mechanism.
- Why (E) is wrong: These are the ligaments of the glenohumeral joint.
Key Points: AC Joint Injury (Rockwood Classification)
- Type I: Sprain of AC ligament. X-ray normal.
- Type II: Tear of AC ligament. AC joint widened, CC distance normal.
- Type III: Tear of AC and CC ligaments. Clavicle elevated <100%.
- Type V: A severe Type III, with >100% elevation of the clavicle.
Question 12: Osteoid Osteoma
Stem: A 17-year-old boy presents with 6 months of persistent, dull pain in his proximal humerus. The pain is significantly worse at night and is reliably relieved by taking aspirin. A CT scan is ordered.
Question: What is the most likely finding on the CT scan?
(A) A well-defined, lytic lesion in the epiphysis. (B) A small, well-defined lucent nidus (<1.5 cm) surrounded by extensive, dense cortical sclerosis. (C) A large, expansile, lytic lesion with multiple fluid-fluid levels. (D) A “ground-glass” matrix lesion expanding the bone. (E) A “rings and arcs” calcified matrix within the medullary cavity.
Correct Answer: (B) A small, well-defined lucent nidus (<1.5 cm) surrounded by extensive, dense cortical sclerosis.
Explanation:
- Why (B) is correct: The clinical history (young patient, night pain, relieved by NSAIDs) is pathognomonic for an osteoid osteoma. The classic CT finding is the small, lytic nidus (the tumour itself) with a massive, disproportionate amount of surrounding reactive cortical sclerosis (the body’s reaction).
- Why (A) is wrong: This describes a chondroblastoma (epiphyseal, lytic, in a teen).
- Why (C) is wrong: This describes an aneurysmal bone cyst (ABC).
- Why (D) is wrong: This describes fibrous dysplasia.
- Why (E) is wrong: This describes a chondroid matrix (enchondroma or chondrosarcoma).
Key Points: Osteoid Osteoma
- Definition: Benign bone tumour, most common in long bones (femur, tibia, humerus).
- Classic Triad: Young patient (10-30), night pain, relief with NSAIDs.
- Imaging: CT is the best modality. Shows a small, lucent nidus (often with a central dot of calcification) and extensive surrounding sclerosis.
Question 13: Enchondroma
Stem: A 45-year-old woman has a hand radiograph for an unrelated injury. An incidental finding is a 1.5 cm, well-defined, lucent lesion in the metaphysis of the proximal phalanx of the 3rd digit. It contains stippled calcifications consistent with a “rings and arcs” chondroid matrix.
Question: What is the most likely diagnosis?
(A) Enchondroma (B) Giant Cell Tumour (GCT) (C) Bone infarct (D) Metastasis (E) Osteoid Osteoma
Correct Answer: (A) Enchondroma.
Explanation:
- Why (A) is correct: Enchondroma is the most common primary bone tumour of the hand. The location (phalanges, metacarpals) and the “rings and arcs” or “stippled” calcification (a chondroid matrix) are classic.
- Why (B) is wrong: GCTs are epiphyseal and are very rare in the hand.
- Why (C) is wrong: Bone infarcts appear as serpiginous, sclerotic borders, not chondroid matrix.
- Why (D) is wrong: Metastases distal to the elbow (acrometastases) are rare, and when they occur, they are typically aggressive, lytic lesions (e.g., from lung cancer).
- Why (E) is wrong: An osteoid osteoma has a nidus and reactive sclerosis, not a chondroid matrix.
Key Points: Enchondroma
- Most common bone tumour of the hand.
- Location: Metaphyseal/diaphyseal, in the small tubular bones.
- Imaging: Lytic, expansile lesion with a chondroid matrix (“rings and arcs”).
- Syndromes: Ollier’s disease (multiple enchondromas) and Maffucci’s syndrome (enchondromas + soft-tissue hemangiomas).
Question 14: Giant Cell Tumour (GCT)
Stem: A 30-year-old woman presents with wrist pain. An X-ray reveals a large, lytic, expansile, and eccentric lesion in the epiphysis of the distal radius. The lesion abuts the articular surface, and the zone of transition is narrow.
Question: Given the patient’s age and the lesion’s location, what is the most likely diagnosis?
(A) Giant Cell Tumour (GCT) (B) Aneurysmal Bone Cyst (ABC) (C) Chondroblastoma (D) Metastasis (E) Brown Tumour
Correct Answer: (A) Giant Cell Tumour (GCT).
Explanation:
- Why (A) is correct: This is the classic description. GCTs are “quasi-malignant” tumours that occur in skeletally mature adults (age 20-40, after growth plates close). Their hallmark is an epiphyseal location that abuts the articular surface. The distal radius is one of the most common sites.
- Why (B) is wrong: An ABC is also lytic and expansile but is typically metaphyseal and occurs in a younger (skeletally immature) patient.
- Why (C) is wrong: A chondroblastoma is also epiphyseal but occurs in skeletally immature patients (before growth plate closure).
- Why (D) is wrong: Metastases are typically metaphyseal/diaphyseal and have a more aggressive appearance.
- Why (E) is wrong: A Brown Tumour (hyperparathyroidism) is possible but less common; it is lytic and expansile but not classically epiphyseal. GCT is the best fit.
Key Points: Giant Cell Tumour (GCT)
- Demographic: Skeletally mature adults (20-40 years).
- Location: Epiphyseal and abuts the joint surface.
- Appearance: Lytic, expansile, eccentric, narrow zone of transition.
- Common Sites: Distal femur, proximal tibia, distal radius.
Question 15: Suprascapular Notch Ganglion
Stem: A 35-year-old volleyball player presents with shoulder weakness and a dull, aching pain. An MRI demonstrates a well-defined, multiloculated cystic lesion within the suprascapular notch. There is marked fatty atrophy of the supraspinatus and infraspinatus muscles.
Question: This combination of findings is diagnostic of:
(A) A SLAP tear with a paralabral cyst. (B) Suprascapular nerve entrapment by a ganglion cyst. (C) Quadrilateral space syndrome. (D) A chronic, retracted rotator cuff tear. (E) Adhesive capsulitis.
Correct Answer: (B) Suprascapular nerve entrapment by a ganglion cyst.
Explanation:
- Why (B) is correct: The suprascapular nerve passes through the suprascapular notch to innervate the supraspinatus, then wraps around the spinoglenoid notch to innervate the infraspinatus. A ganglion cyst (a benign cyst) in this notch compresses the nerve, causing denervation and subsequent fatty atrophy of both muscles.
- Why (A) is wrong: A SLAP tear can cause a paralabral cyst, but it’s typically in the spinoglenoid notch, which would only compress the nerve branch to the infraspinatus. A cyst in the suprascapular notch (higher up) affects both muscles.
- Why (C) is wrong: Quadrilateral space syndrome involves compression of the axillary nerve as it passes through the quadrilateral space, causing atrophy of the teres minor.
- Why (D) is wrong: A rotator cuff tear causes muscle atrophy due to disuse, but the atrophy would not be in this specific nerve distribution, and there would be no compressing cyst.
- Why (E) is wrong: Adhesive capsulitis is soft-tissue inflammation and would show a thickened inferior capsule, not muscle atrophy or a cyst.
Key Points: Suprascapular Nerve Entrapment
- Nerve Path: Suprascapular Notch -> Innervates Supraspinatus -> Spinoglenoid Notch -> Innervates Infraspinatus.
- Suprascapular Notch Cyst: Compresses the main nerve, causing atrophy of both supraspinatus and infraspinatus.
- Spinoglenoid Notch Cyst: Compresses the distal branch, causing isolated atrophy of the infraspinatus only. (Often associated with a SLAP tear).
