Question 1: Slipped Upper Femoral Epiphysis (SUFE)
Stem: A 13-year-old overweight boy presents with a 3-week history of a painful limp and referred pain to his left knee. An AP radiograph of the pelvis is obtained. A line drawn along the superior surface of the left femoral neck (Klein’s line) fails to intersect the lateral part of the femoral epiphysis.
Question: What is the most likely diagnosis?
(A) Slipped Upper Femoral Epiphysis (SUFE) (B) Perthes’ Disease (C) Developmental Dysplasia of the Hip (DDH) (D) Septic Arthritis (E) Aneurysmal Bone Cyst (ABC)
Correct Answer: (A) Slipped Upper Femoral Epiphysis (SUFE).
Explanation:
- Why (A) is correct: This is the classic clinical and radiological presentation of SUFE (also known as SCFE). The key sign is the abnormal Klein’s line, which demonstrates the medial and posterior slippage of the femoral epiphysis relative to the femoral neck. The demographic (obese, adolescent male) is also classic.
- Why (B) is wrong: Perthes’ disease is avascular necrosis of the femoral epiphysis. It affects a younger age group (4-8 years) and appears as a sclerotic, fragmented, and flattened epiphysis.
- Why (C) is wrong: DDH is a congenital condition diagnosed in infancy, characterized by a shallow acetabulum and a superolaterally displaced femoral head.
- Why (D) is wrong: Septic arthritis would present acutely with fever, and radiologically with a joint effusion (loss of fat pads), not an epiphyseal slip.
- Why (E) is wrong: An ABC is a lytic, expansile bone lesion, not a slip of the growth plate.
Key Points: Slipped Upper Femoral Epiphysis (SUFE)
- Definition: A Salter-Harris Type I fracture of the proximal femoral physis.
- Demographic: Typically obese adolescents (10-16 years).
- Classic Sign: Abnormality of Klein’s line on AP view.
- “Frog-leg” View: Best view to assess the degree of posterior slippage (often described as an “ice cream slipping off a cone”).
- Risk: A surgical emergency due to the high risk of avascular necrosis (AVN) of the femoral head.
Question 2: Perthes’ Disease
Stem: A 6-year-old boy presents with a painless limp that has been present for 2 months. An AP radiograph of his right hip demonstrates that the femoral epiphysis is sclerotic, flattened, and appears fragmented. There is also some widening of the medial joint space.
Question: What is the most likely diagnosis?
(A) Slipped Upper Femoral Epiphysis (SUFE) (B) Developmental Dysplasia of the Hip (DDH) (C) Transient Synovitis (Irritable Hip) (D) Perthes’ Disease (E) Septic Arthritis
Correct Answer: (D) Perthes’ Disease.
Explanation:
- Why (D) is correct: This is the classic presentation. Perthes’ disease is avascular necrosis (AVN) of the femoral head epiphysis in a child. The classic age group is 4-8 years. The radiological signs are progressive sclerosis (dead bone), flattening (subchondral fracture), and fragmentation, followed by a re-ossification phase.
- Why (A) is wrong: SUFE affects older, adolescent children and is a slip, not a change in bone density and shape.
- Why (B) is wrong: DDH is a congenital abnormality of acetabular formation, not an acquired AVN.
- Why (C) is wrong: Transient synovitis (irritable hip) is a diagnosis of exclusion that may show a mild effusion on ultrasound, but X-rays are normal.
- Why (E) is wrong: Septic arthritis is an acute, febrile illness and would not cause sclerosis and fragmentation.
Key Points: Perthes’ Disease
- Definition: Idiopathic avascular necrosis of the capital femoral epiphysis.
- Demographic: Typically boys aged 4-8 years.
- Radiological Stages:
- Early: Small epiphysis, medial joint space widening.
- Sclerosis: Epiphysis appears dense.
- Fragmentation: Epiphysis breaks apart.
- Re-ossification: Bone begins to reform.
- Later Sign: “Mushroom-shaped” femoral head (coxa magna).
Question 3: Femoral Neck Fracture (Garden)
Stem: An 82-year-old woman falls and presents with hip pain. An AP radiograph shows an impacted subcapital fracture of the femoral neck. The inferior trabeculae are angulated (valgus), but there is no displacement.
Question: According to the Garden classification, what type of fracture is this?
(A) Garden I (B) Garden II (C) Garden III (D) Garden IV (E) Intertrochanteric
Correct Answer: (A) Garden I.
Explanation:
- Why (A) is correct: A Garden I fracture is an incomplete or impacted fracture that is non-displaced and in a stable valgus position.
- Why (B) is wrong: A Garden II fracture is a complete fracture that is non-displaced.
- Why (C) is wrong: A Garden III fracture is a complete fracture with partial displacement (varus angulation). The trabeculae are no longer aligned.
- Why (D) is wrong: A Garden IV fracture is a complete fracture with full displacement. The femoral head is completely dissociated from the neck.
- Why (E) is wrong: This is an intracapsular fracture. An intertrochanteric fracture is extracapsular.
Key Points: Garden Classification (Femoral Neck)
- Used for subcapital fractures to predict the risk of AVN.
- Garden I: Incomplete / Impacted. (Low risk of AVN)
- Garden II: Complete, non-displaced. (Moderate risk of AVN)
- Garden III: Complete, partially displaced. (High risk of AVN)
- Garden IV: Complete, fully displaced. (Highest risk of AVN)
Question 4: Tibial Plateau Fracture (Schatzker)
Stem: A 45-year-old man is struck by a car, resulting in a severe valgus force to his knee. A CT scan confirms a split-depression fracture of the lateral tibial plateau.
Question: What is the Schatzker classification for this fracture?
(A) Schatzker I (B) Schatzker II (C) Schatzker III (D) Schatzker IV (E) Schatzker V
Correct Answer: (B) Schatzker II.
Explanation:
- Why (B) is correct: A Schatzker II fracture is a split plus depression of the lateral plateau. This is the most common type.
- Why (A) is wrong: A Schatzker I is a pure split of the lateral plateau (common in younger patients).
- Why (C) is wrong: A Schatzker III is a pure depression of the lateral plateau (common in older, osteoporotic patients).
- Why (D) is wrong: A Schatzker IV is any fracture of the medial plateau.
- Why (E) is wrong: A Schatzker V is a bicondylar fracture (both plateaus are involved).
Key Points: Schatzker Classification (Tibial Plateau)
- Describes tibial plateau fractures, which are often from valgus (car bumper) or varus forces.
- I, II, III: Involve the Lateral plateau (Split, Split-Depression, Depression).
- IV: Involves the Medial plateau (high-energy, poor prognosis).
- V: Involves Both plateaus (bicondylar).
- VI: Involves the plateau and a diaphyseal dissociation.
Question 5: Ankle Fracture (Weber)
Stem: A 30-year-old woman twists her ankle. A radiograph reveals a spiral fracture of the distal fibula beginning at the level of the ankle syndesmosis and extending proximally. There is associated widening of the medial clear space.
Question: What is the Weber classification for this fracture?
(A) Weber A (B) Weber B (C) Weber C (D) Maisonneuve (E) Pilon
Correct Answer: (B) Weber B.
Explanation:
- Why (B) is correct: A Weber B fracture is a fracture of the fibula at the level of the tibiofibular syndesmosis. It is the most common type and implies that the syndesmosis is potentially unstable. The widened medial clear space indicates associated deltoid ligament rupture, making this a “bimalleolar equivalent” and unstable.
- Why (A) is wrong: A Weber A fracture is below the syndesmosis. The syndesmosis is intact and the joint is stable.
- Why (C) is wrong: A Weber C fracture is above the syndesmosis. This type always implies a syndesmotic rupture and an unstable ankle.
- Why (D) is wrong: A Maisonneuve fracture is a Weber C injury where the fibular fracture is very high (at the proximal fibula), with a syndesmotic tear and deltoid ligament rupture.
- Why (E) is wrong: A Pilon fracture is an intra-articular fracture of the distal tibia (tibial plafond).
Key Points: Weber Ankle Fracture Classification
- Based on the level of the fibular fracture relative to the syndesmosis.
- Weber A: Below syndesmosis. Stable.
- Weber B: At level of syndesmosis. May be unstable (if deltoid ligament is torn).
- Weber C: Above syndesmosis. Always unstable.
Question 6: Lisfranc Injury
Stem: A 24-year-old American football player has his foot forcefully plantarflexed and twisted. A weight-bearing radiograph of the foot reveals diastasis (widening) of the space between the base of the 1st and 2nd metatarsals. A small “fleck sign” (avulsion fragment) is seen in this space.
Question: What is the most likely diagnosis?
(A) Jones Fracture (B) Lisfranc Injury (C) March Fracture (D) Chopart Dislocation (E) Navicular Stress Fracture
Correct Answer: (B) Lisfranc Injury.
Explanation:
- Why (B) is correct: This is the classic presentation. The Lisfranc joint is the tarsometatarsal joint. The Lisfranc ligament (which holds the 2nd metatarsal to the medial cuneiform) is the key stabiliser. Diastasis between the 1st and 2nd metatarsals indicates a rupture of this ligament and a severe, unstable injury. The “fleck sign” is an avulsion of the ligament from the 2nd metatarsal base.
- Why (A) is wrong: A Jones fracture is a transverse fracture at the base of the 5th metatarsal.
- Why (C) is wrong: A March fracture is a stress fracture of the shaft of the 2nd or 3rd metatarsal.
- Why (D) is wrong: A Chopart dislocation is a dislocation of the midtarsal joint (talonavicular and calcaneocuboid).
- Why (E) is wrong: A navicular stress fracture would be a fracture line in the navicular, not diastasis of the metatarsals.
Key Points: Lisfranc Injury
- Definition: Disruption of the tarsometatarsal (TMT) joint complex.
- Key Ligament: The Lisfranc ligament (base of 2nd MT to medial cuneiform).
- Radiographic Signs:
- Diastasis between 1st and 2nd MT bases.
- “Fleck Sign”: Avulsion fracture in the 1st-2nd MT space.
- Loss of alignment (e.g., medial border of 2nd MT not aligned with medial border of intermediate cuneiform).
- Note: Weight-bearing or stress views are often required to unmask the instability.
Question 7: Osteoid Osteoma
Stem: A 19-year-old male athlete presents with a 6-month history of a dull ache in his right femur. The pain is notably worse at night and is dramatically relieved by taking Ibuprofen. A CT scan reveals a 1 cm lucent nidus in the femoral cortex, surrounded by a large area of dense reactive cortical sclerosis.
Question: What is the most likely diagnosis?
(A) Osteoid Osteoma (B) Brodie’s Abscess (C) Stress Fracture (D) Osteosarcoma (E) Eosinophilic Granuloma (LCH)
Correct Answer: (A) Osteoid Osteoma.
Explanation:
- Why (A) is correct: The clinical triad (young patient, night pain, NSAID relief) is pathognomonic for an osteoid osteoma. The CT findings of a small, well-defined nidus (<1.5 cm) surrounded by extensive reactive sclerosis are also classic.
- Why (B) is wrong: A Brodie’s abscess (a chronic, walled-off osteomyelitis) can also present as a lytic nidus with surrounding sclerosis, but the clinical history of pain relief with NSAIDs is the key differentiator.
- Why (C) is wrong: A stress fracture would appear as a linear lucency and periosteal reaction, not a round nidus.
- Why (D) is wrong: An osteosarcoma is a large, aggressive, malignant tumour, not a small, benign nidus.
- Why (E) is wrong: LCH (Langerhans Cell Histiocytosis) is a lytic lesion, sometimes with a “beveled edge,” but does not have this clinical history or marked sclerosis.
Key Points: Osteoid Osteoma
- Definition: Benign bone tumour (produces prostaglandins, causing the pain).
- Clinical Triad: Young patient (10-30), night pain, relief with NSAIDs.
- Imaging (CT is best):
- Nidus: Small (<1.5 cm), lytic, often with a central calcified dot.
- Sclerosis: Extensive, dense, reactive sclerosis surrounding the nidus.
- Treatment: Radiofrequency Ablation (RFA).
Question 8: Non-Ossifying Fibroma (NOF)
Stem: A 14-year-old boy has a knee X-ray for a minor sports injury. An incidental finding is a 3 cm, well-defined, lytic lesion in the metaphysis of the distal femur. The lesion is eccentric, has a “bubbly” (multilocular) appearance, and is surrounded by a thin, sclerotic border.
Question: What is the most likely diagnosis?
(A) Non-Ossifying Fibroma (NOF) (B) Aneurysmal Bone Cyst (ABC) (C) Giant Cell Tumour (GCT) (D) Osteosarcoma (E) Chondromyxoid Fibroma
Correct Answer: (A) Non-Ossifying Fibroma (NOF).
Explanation:
- Why (A) is correct: This is the most common benign bone lesion in children. The classic appearance is metaphyseal, eccentric, lytic, and having a well-defined sclerotic border. They are asymptomatic and typically “heal” by filling in with bone (involuting) as the patient matures.
- Why (B) is wrong: An ABC is also lytic and in this age group, but it is typically very expansile (“aneurysmal”) and would have fluid-fluid levels on CT/MRI.
- Why (C) is wrong: A GCT is epiphyseal (abuts the joint) and occurs in skeletally mature adults (age 20-40).
- Why (D) is wrong: An osteosarcoma is a malignant, aggressive lesion with ill-defined borders, soft-tissue mass, and periosteal reaction. It would not have a thin, sclerotic border.
- Why (E) is wrong: This is a rare, lytic, eccentric tumour, but NOF is vastly more common and a perfect fit.
Key Points: Non-Ossifying Fibroma (NOF)
- AKA: Fibrous Cortical Defect (if <2 cm).
- Definition: A benign, developmental “do-not-touch” lesion.
- Location: Metaphyseal (classically distal femur).
- Imaging: Eccentric, lytic, “bubbly” appearance, with a thin sclerotic border.
Question 9: Osteosarcoma
Stem: A 16-year-old boy presents with 3 months of increasing pain and swelling around his knee. A radiograph of the distal femur shows a large, destructive lesion in the metaphysis. The lesion has ill-defined borders, a large soft-tissue component, and a “sunburst” periosteal reaction. A Codman’s triangle is also present.
Question: What is the most likely diagnosis?
(A) Osteosarcoma (B) Ewing’s Sarcoma (C) Chondrosarcoma (D) Osteomyelitis (E) Giant Cell Tumour (GCT)
Correct Answer: (A) Osteosarcoma.
Explanation:
- Why (A) is correct: This is the classic presentation. Osteosarcoma is the most common primary malignant bone tumour in adolescents. The key features are: metaphyseal location (around the knee is most common), aggressive appearance (ill-defined borders), and aggressive periosteal reaction (“sunburst” or “hair-on-end”) and a Codman’s triangle (periosteum lifted off the bone).
- Why (B) is wrong: Ewing’s sarcoma is also in this age group but is classically diaphyseal (in the shaft) and has an “onion-skin” periosteal reaction.
- Why (C) is wrong: Chondrosarcoma is a tumour of older adults (40-60) and has a “rings and arcs” chondroid matrix.
- Why (D) is wrong: Osteomyelitis can mimic a malignant tumour (e.g., Ewing’s) but this classic “sunburst” appearance with a large soft-tissue mass is typical for osteosarcoma.
- Why (E) is wrong: GCT is epiphyseal and is not this aggressive.
Key Points: Osteosarcoma
- Definition: Most common primary malignant bone tumour (excluding myeloma).
- Demographic: Bimodal (10-20 years, or >65 in Paget’s).
- Location: Metaphysis (classically distal femur, proximal tibia).
- Imaging:
- Destructive, ill-defined lesion.
- Osteoid matrix: “Cloud-like” or “fluffy” tumour bone.
- Aggressive Periosteal Reaction: “Sunburst” and Codman’s triangle.
Question 10: Ewing’s Sarcoma
Stem: A 14-year-old girl presents with 2 months of localized leg pain, fever, and a raised ESR. A radiograph of the femur shows a large, permeative, lytic lesion in the diaphysis. There is a lamellated, “onion-skin” periosteal reaction and an associated large soft-tissue mass.
Question: What is the most likely diagnosis?
(A) Osteosarcoma (B) Ewing’s Sarcoma (C) Osteomyelitis (D) Langerhans Cell Histiocytosis (LCH) (E) Metastasis
Correct Answer: (B) Ewing’s Sarcoma.
Explanation:
- Why (B) is correct: This is the classic presentation. Ewing’s is a “small round blue cell tumour” that mimics infection (fever, raised ESR). Key imaging features are the diaphyseal location, a permeative (moth-eaten) appearance, and the classic “onion-skin” (lamellated) periosteal reaction.
- Why (A) is wrong: Osteosarcoma is metaphyseal and has a “sunburst” reaction.
- Why (C) is wrong: Osteomyelitis is the great mimicker of Ewing’s (and vice-versa). However, the classic “onion-skin” periostitis is more strongly associated with Ewing’s.
- Why (D) is wrong: LCH is a lytic lesion but does not typically have this aggressive periosteal reaction or systemic symptoms.
- Why (E) is wrong: Metastasis (e.g., from neuroblastoma) is possible, but Ewing’s is the classic primary tumour with this appearance.
Key Points: Ewing’s Sarcoma
- Definition: Malignant “small round blue cell tumour” (t(11;22) translocation).
- Demographic: 10-20 years.
- Clinical: Mimics infection (pain, fever, raised ESR/LDH).
- Location: Diaphysis of long bones (femur) or flat bones (pelvis).
- Imaging: Permeative, lytic lesion; “onion-skin” periostitis; large soft-tissue mass.
Question 11: Aneurysmal Bone Cyst (ABC)
Stem: A 17-year-old girl presents with knee pain after a fall. An X-ray shows a large, lytic, and highly expansile lesion in the proximal tibial metaphysis. A follow-up MRI confirms the lesion is multicystic and demonstrates multiple fluid-fluid levels within it.
Question: What is the most likely diagnosis?
(A) Aneurysmal Bone Cyst (ABC) (B) Giant Cell Tumour (GCT) (C) Non-Ossifying Fibroma (NOF) (D) Telangiectatic Osteosarcoma (E) Simple Bone Cyst
Correct Answer: (A) Aneurysmal Bone Cyst (ABC).
Explanation:
- Why (A) is correct: The two key features are the expansile (“aneurysmal”) nature and the presence of fluid-fluid levels on CT or MRI. This appearance is caused by layering of blood products within the cystic spaces.
- Why (B) is wrong: A GCT is epiphyseal and occurs in skeletally mature patients.
- Why (C) is wrong: An NOF is eccentric and lytic but not typically expansile and does not have fluid-fluid levels.
- Why (D) is wrong: This is the great mimicker. Telangiectatic osteosarcoma is a malignant tumour that also has fluid-fluid levels. The key differentiator is that it will have a thick, nodular, enhancing soft-tissue component, whereas an ABC has thin, smooth septa.
- Why (E) is wrong: A simple bone cyst is a central, lytic, non-expansile lesion, often with a “fallen fragment” sign.
Key Points: Aneurysmal Bone Cyst (ABC)
- Definition: Benign, highly expansile, blood-filled cystic lesion.
- Demographic: < 20 years.
- Location: Metaphysis of long bones or posterior elements of the spine.
- Imaging:
- Eccentric, expansile, lytic.
- Fluid-Fluid Levels (best seen on T2 MRI or CECT).
- Thin, enhancing septations.
Question 12: ACL Tear
Stem: A 26-year-old man suffers a “pivot-shift” injury during a football match, feeling a “pop” in his knee. A sagittal T2-weighted MRI demonstrates high-signal “kissing” bone bruises in the lateral femoral condyle and the posterolateral tibial plateau. The ACL itself is not clearly visualised.
Question: These secondary findings are highly specific for a tear of which ligament?
(A) Anterior Cruciate Ligament (ACL) (B) Posterior Cruciate Ligament (PCL) (C) Medial Collateral Ligament (MCL) (D) Lateral Collateral Ligament (LCL) (E) Patellar Tendon
Correct Answer: (A) Anterior Cruciate Ligament (ACL).
Explanation:
- Why (A) is correct: This is the classic “pivot-shift” impaction pattern. When the ACL tears, the tibia subluxes anteriorly, causing the lateral femoral condyle and the posterolateral tibial plateau to impact. This “kissing contusion” pattern is a highly specific secondary sign of an acute ACL tear.
- Why (B) is wrong: A PCL tear is from a “dashboard injury” (AP blow) and would cause contusions on the anterior tibia and patella.
- Why (C) & (D) are wrong: Collateral ligament tears are from varus/valgus stress and would not cause this specific rotational contusion pattern.
- Why (E) is wrong: A patellar tendon tear would show a defect in the tendon, not this bone bruise pattern.
Key Points: ACL Tear (Secondary MRI Signs)
- Bone Bruise: “Kissing contusions” in the lateral compartment (lateral femoral condyle, posterolateral tibial plateau).
- Segond Fracture: An avulsion of the lateral tibial rim (pathognomonic).
- Anterior Tibial Translation: >7 mm anterior subluxation of the tibia.
- Buckling of the PCL: The PCL appears slack and “buckled” as the tibia has moved forward.
Question 13: Achilles Tendon Rupture
Stem: A 42-year-old “weekend warrior” plays a game of squash and suddenly feels as if he was “shot in the back of the heel”. He has a palpable gap in his Achilles tendon and a positive Thompson’s test.
Question: Where is the most common site for this rupture to occur?
(A) At the calcaneal insertion. (B) At the musculotendinous junction. (C) In the mid-substance, 2-6 cm proximal to the insertion. (D) As an avulsion fracture of the calcaneal tuberosity. (E) Within the gastrocnemius muscle belly.
Correct Answer: (C) In the mid-substance, 2-6 cm proximal to the insertion.
Explanation:
- Why (C) is correct: This specific region (2-6 cm proximal to the calcaneal insertion) is a “watershed area” of poor vascularity. This hypovascularity makes it the most common site for a mid-substance rupture, especially in the “weekend warrior” demographic.
- Why (A) is wrong: Insertional tendinopathy is common, but acute rupture at the insertion is less common than the mid-substance tear.
- Why (B) is wrong: Ruptures at the musculotendinous junction are less common.
- Why (D) is wrong: An avulsion fracture is a bone injury, not a tendon rupture, and occurs in a different patient population (e.g., osteoporotic).
- Why (E) is wrong: This would be a muscle tear, not a tendon rupture.
Key Points: Achilles Tendon Rupture
- Demographic: Middle-aged men (“weekend warriors”).
- Clinical: Sudden “pop” or “shot” sensation, palpable gap, positive Thompson’s test (squeezing the calf causes no plantarflexion).
- Location: Most common in the hypovascular “watershed” zone, 2-6 cm proximal to the calcaneal insertion.
- Imaging (US/MRI): Shows a fluid-filled gap in the tendon.
Question 14: Osteochondroma
Stem: An 18-year-old is found to have a painless, hard lump on the side of his knee. A radiograph reveals a bony outgrowth from the distal femoral metaphysis. The key finding is that the cortex and medullary cavity of the lesion are in direct continuity with the parent bone. The lesion is pointing away from the joint.
Question: What is the most likely diagnosis?
(A) Osteochondroma (B) Osteoid Osteoma (C) Non-Ossifying Fibroma (D) Parosteal Osteosarcoma (E) Myositis Ossificans
Correct Answer: (A) Osteochondroma.
Explanation:
- Why (A) is correct: This is the pathognomonic description of an osteochondroma (or exostosis). The defining feature is cortico-medullary continuity, meaning the cortex and medulla of the stalk are continuous with the native bone. They are benign and typically point away from the joint.
- Why (B) & (C) are wrong: These are intra-osseous lesions (within the bone), not outgrowths from the bone.
- Why (D) is wrong: A parosteal osteosarcoma is a surface malignancy, but it is typically a large, “stuck-on” mass without medullary continuity.
- Why (E) is wrong: Myositis ossificans is calcification within the soft tissues (often post-traumatic) and is not attached to the bone (though it can be).
Key Points: Osteochondroma
- Definition: Most common benign bone tumour; a cartilage-capped bony projection.
- Location: Metaphysis of long bones (especially around the knee).
- Pathognomonic Sign: Cortico-medullary continuity with the parent bone.
- Malignant Risk: The cartilage cap can (<1%) transform into a chondrosarcoma (suspect if the cap is >1.5 cm thick in an adult).
Question 15: Paget’s Disease
Stem: A 72-year-old man presents with an elevated alkaline phosphatase on routine bloodwork. A radiograph of his pelvis shows thickening of the iliopectineal line, coarsening of the trabecular pattern, and expansion of the right pubic ramus.
Question: What is the most likely diagnosis?
(A) Paget’s Disease (B) Sclerotic Metastases (e.g., from prostate) (C) Myelofibrosis (D) Fluorosis (E) Lymphoma
Correct Answer: (A) Paget’s Disease.
Explanation:
- Why (A) is correct: This combination of findings is classic for Paget’s disease. The key features are bone expansion, cortical thickening, and coarsening of the trabeculae. Thickening of the iliopectineal line (the pelvic brim) is a specific sign.
- Why (B) is wrong: Sclerotic prostate metastases are dense (“blastic”) but are typically not expansile and do not cause trabecular coarsening.
- Why (C) & (D) are wrong: Myelofibrosis and fluorosis both cause diffuse, uniform sclerosis, not the focal, expansile, coarse-trabeculated pattern of Paget’s.
- Why (E) is wrong: Lymphoma can cause sclerotic bone lesions but is less common and would not have this classic “Pagetoid” appearance.
Key Points: Paget’s Disease of Bone
- Pathology: A chronic disorder of accelerated, abnormal bone remodelling (disorganised osteoclast and osteoblast activity).
- Phases: 1. Lytic (e.g., “osteoporosis circumscripta” in skull), 2. Mixed, 3. Sclerotic.
- Key Imaging Signs:
- Bone Expansion.
- Cortical Thickening.
- Coarsening of Trabeculae.
- Common Sites: Pelvis, Femur, Spine, Skull.
- Complication: Malignant transformation to osteosarcoma (<1%).
