Question 1: Slipped Upper Femoral Epiphysis (SUFE)
Stem: A 13-year-old overweight boy presents with chronic left hip pain and a limp. On an AP radiograph of the pelvis, a line is drawn along the superior aspect of the femoral neck. This line fails to intersect the lateral portion of the capital femoral epiphysis.
Question: What is the eponym for this line used in the diagnosis of SUFE?
(A) Perkins’ line (B) Hilgenreiner’s line (C) Klein’s line (D) Shenton’s line (E) Skinner’s line
Correct Answer: (C) Klein’s line
Explanation:
- Why (C) is correct: Klein’s line is drawn along the superior edge of the femoral neck. Normally, it should intersect at least a small portion of the lateral femoral epiphysis. If it fails to do so, it indicates a Slipped Upper Femoral Epiphysis (SUFE).
- Why (A) is wrong: Perkins’ line is a vertical line through the lateral acetabular roof used to diagnose Developmental Dysplasia of the Hip (DDH).
- Why (B) is wrong: Hilgenreiner’s line is a horizontal line through the triradiate cartilages, also used in DDH.
- Why (D) is wrong: Shenton’s line is a curved line along the inferior pubic ramus and medial femoral neck; disruption suggests hip dislocation or fracture.
- Why (E) is wrong: Skinner’s line is used in adults to assess the relationship of the greater trochanter to the fovea capitis.
Key Points: SUFE
- Patient: Typically obese, adolescent males.
- Best View: Frog-leg lateral view is more sensitive than AP for early slips.
- Complication: High risk of Avascular Necrosis (AVN).
Question 2: Non-Accidental Injury (NAI) – Specificity
Stem: A 6-month-old infant is brought to the emergency department with irritability. A skeletal survey is performed as part of a safeguarding investigation.
Question: Which of the following fracture types has the highest specificity for Non-Accidental Injury?
(A) Simple linear skull fracture (B) Mid-shaft clavicle fracture (C) Classic Metaphyseal Lesion (CML) (D) Greenstick fracture of the radius (E) Spiral fracture of the femur in a walking child
Correct Answer: (C) Classic Metaphyseal Lesion (CML)
Explanation:
- Why (C) is correct: The Classic Metaphyseal Lesion (CML), also known as a “corner fracture” or “bucket-handle fracture,” is highly specific for NAI. It is caused by forceful pulling or twisting of a limb, leading to an avulsion of a disc of bone from the metaphysis.
- Why (A) is wrong: Linear skull fractures are common in accidental falls, though multiple or complex fractures raise suspicion.
- Why (B) is wrong: Clavicle fractures are common birth injuries or accidental injuries in toddlers.
- Why (D) is wrong: Greenstick fractures are very common accidental childhood injuries due to the flexibility of young bone.
- Why (E) is wrong: While a femur fracture in a non-ambulatory infant is highly suspicious, a spiral fracture in a child who can walk is often accidental (e.g., “toddler’s fracture”).
Key Points: High-Suspicion NAI Fractures
- High Specificity: CMLs, posterior rib fractures, scapular fractures, sternal fractures.
- Moderate Specificity: Multiple fractures of different ages, vertebral body fractures.
Question 3: Legg-Calvé-Perthes Disease
Stem: A 6-year-old boy presents with a painless limp. Radiographs show a small, sclerotic right femoral head with early subchondral lucency and widening of the medial joint space.
Question: The “crescent sign” seen in this patient represents:
(A) A joint effusion (B) A subchondral insufficiency fracture (C) Metaphyseal cyst formation (D) Synovial thickening (E) Labral tear
Correct Answer: (B) A subchondral insufficiency fracture
Explanation:
- Why (B) is correct: In Perthes disease (idiopathic AVN of the femoral head), the “crescent sign” is a linear lucency representing a subchondral fracture. It indicates Stage 2/3 disease and impending collapse of the femoral head.
- Why (A) is wrong: Effusion causes joint space widening but not a subchondral lucent line.
- Why (C) is wrong: Metaphyseal cysts occur later in Perthes but are not the “crescent sign.”
- Why (D) & (E) are wrong: These are soft-tissue findings better seen on MRI, not the radiographic crescent sign.
Key Points: Perthes Disease
- Age: Classically 4–8 years old.
- Radiographic Stages: Sclerosis/small epiphysis -> Fragmentation/Crescent sign -> Re-ossification -> Remodeling.
- End result: Coxa magna (large, flattened femoral head).
Question 4: Osteogenesis Imperfecta (OI)
Stem: A newborn presents with multiple fractures of the long bones and ribs. The ribs have a “beaded” appearance due to exuberant callus formation. The skull shows multiple small, irregular ossicles within the cranial sutures.
Question: These small skull bones are known as:
(A) Enchondromas (B) Osteomas (C) Wormian bones (D) Schmorl’s nodes (E) Bone islands
Correct Answer: (C) Wormian bones
Explanation:
- Why (C) is correct: Wormian bones (intrasutural bones) are small accessory bone ossicles found within cranial sutures. While they can be normal, the presence of >10 is associated with OI, cleidocranial dysplasia, and hypothyroidism.
- Why (A) is wrong: Enchondromas are benign cartilaginous tumors within the medullary cavity.
- Why (B) is wrong: Osteomas are benign outgrowths of compact bone, usually in the sinuses.
- Why (D) is wrong: Schmorl’s nodes are disc herniations into vertebral endplates.
- Why (E) is wrong: Bone islands (enostoses) are small areas of compact bone within cancellous bone.
Key Points: Osteogenesis Imperfecta
- Pathology: Defect in Type 1 collagen.
- Key Signs: Blue sclera, multiple fractures, Wormian bones, and “popcorn calcifications” at the metaphyses.
Question 5: Salter-Harris Classification
Stem: An 11-year-old girl falls and sustains an injury to her ankle. A radiograph shows a fracture line extending through the epiphysis and the growth plate (physis), but the metaphysis is intact.
Question: According to the Salter-Harris classification, what type of fracture is this?
(A) Type I (B) Type II (C) Type III (D) Type IV (E) Type V
Correct Answer: (C) Type III
Explanation:
- Why (C) is correct:Type III is a fracture through the Epiphysis and Physis (Mnemonic: S-A-L-T-E-R).
- S (I): Straight across (Physis only).
- A (II): Above (Physis + Metaphysis). Most common.
- L (III): Lower (Physis + Epiphysis).
- T (IV): Through (Metaphysis + Physis + Epiphysis).
- ER (V): ERasure/Crush (Compression of Physis).
- Why (A), (B), (D), (E) are wrong: These represent the other components of the mnemonic as described above.
Key Points: Salter-Harris
- Type II is the most common.
- Type III and IV are intra-articular and carry a higher risk of growth arrest.
Question 6: Osgood-Schlatter Disease
Stem: A 14-year-old athletic boy presents with chronic pain and swelling over the anterior aspect of his knee, just below the patella. Radiographs show fragmentation of the tibial tuberosity and soft-tissue swelling.
Question: What is the underlying mechanism of this condition?
(A) Acute avulsion fracture (B) Traction apophysitis (C) Primary bone malignancy (D) Septic arthritis (E) Avascular necrosis
Correct Answer: (B) Traction apophysitis
Explanation:
- Why (B) is correct: Osgood-Schlatter is a traction apophysitis of the tibial tuberosity caused by repetitive strain from the patellar tendon during growth spurts.
- Why (A) is wrong: While it involves the apophysis, it is a chronic stress injury rather than a single acute traumatic avulsion event.
- Why (C) is wrong: The location and appearance are classic for benign stress; malignancy (like Osteosarcoma) usually involves the metaphysis and has a sunburst reaction.
- Why (D) is wrong: Septic arthritis involves the joint space, not the tuberosity.
- Why (E) is wrong: AVN in this region (Sinding-Larsen-Johansson) affects the inferior pole of the patella, not the tibial tuberosity.
Key Points: Osgood-Schlatter
- Demographic: Active adolescents (10–15 years).
- Imaging: Soft tissue swelling over the tibial tubercle; fragmentation/calcification of the tubercle.
Question 7: Toddler’s Fracture
Stem: A 2-year-old child refuses to weight-bear on the right leg after a minor stumble. Initial AP and lateral radiographs of the tibia appear normal.
Question: Which additional radiographic view is most likely to reveal a faint, non-displaced Toddler’s fracture?
(A) Sky-line view (B) Internal oblique view (C) Internal rotation view (D) Stress view (E) Weight-bearing view
Correct Answer: (B) Internal oblique view
Explanation:
- Why (B) is correct: A Toddler’s fracture is a non-displaced spiral fracture of the distal tibia. It is often invisible on standard AP/Lateral views. An oblique view is frequently necessary to see the fracture line.
- Why (A) is wrong: Skyline view is for the patella.
- Why (D) & (E) are wrong: These are contraindicated or impractical in a pained 2-year-old and generally not used for this diagnosis.
Key Points: Toddler’s Fracture
- Age: 9 months to 3 years.
- Clinical: Refusal to walk/limp after minimal trauma.
- Imaging: Often occult initially; follow-up at 10–14 days will show periosteal reaction.
Question 8: Blount’s Disease
Stem: A 3-year-old child presents with progressive bowing of the legs (genu varum). Radiographs show medial sloping and fragmentation of the proximal tibial metaphysis.
Question: This condition is most commonly associated with which of the following?
(A) Vitamin D deficiency (B) Early walking and obesity (C) Type 1 Diabetes (D) Trisomy 21 (E) Steroid use
Correct Answer: (B) Early walking and obesity
Explanation:
- Why (B) is correct: Blount’s disease (Tibia Vara) is caused by disordered endochondral ossification of the medial part of the proximal tibial physis. Excessive weight (obesity) and early weight-bearing (early walking) are the primary risk factors.
- Why (A) is wrong: This causes Rickets, which shows generalized metaphyseal fraying and cupping, not isolated proximal tibial medial sloping.
- Why (C), (D), (E) are wrong: These are not established primary risk factors for Blount’s.
Key Points: Blount’s Disease
- Infantile form: 1–3 years (often bilateral).
- Adolescent form: >10 years (often unilateral).
- Measurement: Metaphyseal-diaphyseal angle >11 degrees is suspicious.
Question 9: Rickets
Stem: A 2-year-old child with a restricted diet presents with bowed legs. Radiographs of the wrists show widening of the growth plates, with fraying and cupping of the distal radial and ulnar metaphyses.
Question: These features are hallmark findings of:
(A) Scurvy (B) Rickets (C) Hypophosphatasia (D) Achondroplasia (E) Lead poisoning
Correct Answer: (B) Rickets
Explanation:
- Why (B) is correct: Rickets (Vitamin D deficiency) results in failure of osteoid mineralization. This causes the metaphyses to become soft and “splayed” out by the weight of the epiphysis, leading to cupping and fraying.
- Why (A) is wrong: Scurvy shows a dense “white line of Frankel” and a lucent “Trummerfeld zone,” not cupping.
- Why (D) is wrong: Achondroplasia shows short, thick bones and “squared” iliac wings.
- Why (E) is wrong: Lead poisoning causes dense metaphyseal bands (“lead lines”).
Key Points: Rickets
- Best place to look: Rapidly growing metaphyses (Wrists and Knees).
- Signs: Fraying, cupping, splaying, and generalized osteopenia.
Question 10: Non-Accidental Injury (Rib Fractures)
Stem: As part of a skeletal survey for NAI, a baby has a chest radiograph. Multiple small, rounded opacities are seen adjacent to the posterior aspects of several ribs near the costovertebral joints.
Question: What do these rounded opacities represent?
(A) Normal anatomical variation (B) Healing rib fractures with callus formation (C) Metastatic neuroblastoma (D) Accessory ossification centers (E) Primary lung nodules
Correct Answer: (B) Healing rib fractures with callus formation
Explanation:
- Why (B) is correct: Posterior rib fractures are highly specific for NAI. They are caused by forceful squeezing of the chest. Callus formation (healing bone) appears as rounded or spindle-shaped opacities along the rib.
- Why (A) is wrong: Ribs should be smooth; there is no normal variation that mimics posterior callus.
- Why (C) is wrong: Neuroblastoma usually causes bone destruction (lytic lesions), not focal callus-like opacities.
- Why (D) is wrong: Accessory centers do not occur in the mid-posterior rib.
Key Points: NAI Rib Fractures
- Location: Posterior ribs (near the spine) are the “red flag” location.
- Mechanism: Squeezing the infant’s chest (anteroposterior compression).
Question 11: Ewing Sarcoma
Stem: A 12-year-old boy presents with thigh pain and a fever. Radiograph shows a permeative lytic lesion in the diaphysis of the femur with a “hair-on-end” or “onion-skin” periosteal reaction.
Question: Which of the following is the most likely diagnosis?
(A) Osteosarcoma (B) Ewing Sarcoma (C) Osteoid Osteoma (D) Simple Bone Cyst (E) Non-Ossifying Fibroma
Correct Answer: (B) Ewing Sarcoma
Explanation:
- Why (B) is correct: Ewing Sarcoma classically involves the diaphysis (shaft) of long bones in children. The aggressive periosteal reaction (“onion-skin” – lamellated) is characteristic.
- Why (A) is wrong: Osteosarcoma is more common in the metaphysis and usually has a “sunburst” or “Codman’s triangle” reaction.
- Why (C) is wrong: Osteoid osteoma is small (<1.5 cm) with a lucent nidus and dense surrounding sclerosis.
- Why (D) & (E) are wrong: These are “do-not-touch” benign lesions that are well-circumscribed and lack aggressive periosteal reactions.
Key Points: Ewing Sarcoma
- Location: Diaphysis.
- Clinical: Can mimic osteomyelitis (pain, fever, raised ESR).
- Translocation: t(11;22).
Question 12: Osteoid Osteoma
Stem: An 8-year-old presents with leg pain that is worse at night and completely relieved by aspirin. Radiographs show a small 1 cm lucent lesion in the cortex of the tibial shaft, surrounded by a large area of dense reactive sclerosis.
Question: What is the most likely diagnosis?
(A) Osteosarcoma (B) Osteoid Osteoma (C) Brodie’s abscess (D) Osteoblastoma (E) Stress fracture
Correct Answer: (B) Osteoid Osteoma
Explanation:
- Why (B) is correct: This is a classic clinical “buzzword” scenario. The night pain relieved by NSAIDs is pathognomonic for Osteoid Osteoma. The 1 cm lucent nidus with surrounding sclerosis is the classic imaging appearance.
- Why (C) is wrong: Brodie’s abscess (subacute osteomyelitis) is usually in the metaphysis and is a larger lucent tract.
- Why (D) is wrong: Osteoblastoma is histologically similar but >1.5–2 cm in size and usually involves the posterior elements of the spine.
Key Points: Osteoid Osteoma
- Classic Triad: Night pain, relief with aspirin, lucent nidus < 1.5 cm.
- CT: Best modality to identify the nidus.
Question 13: Developmental Dysplasia of the Hip (DDH)
Stem: A 4-week-old female is referred for an ultrasound due to a positive Barlow maneuver. The radiologist measures the angle between the vertical line of the iliac bone and the bony acetabular roof.
Question: What is the name of this angle, and what is its normal value in a mature infant?
(A) Alpha angle; >60 degrees (B) Beta angle; >60 degrees (C) Alpha angle; <60 degrees (D) Beta angle; <55 degrees (E) Acetabular angle; <20 degrees
Correct Answer: (A) Alpha angle; >60 degrees
Explanation:
- Why (A) is correct: In the Graf classification for DDH ultrasound, the Alpha angle measures the bony acetabular roof. A value >60 degrees is considered normal (Type 1 hip).
- Why (B) is wrong: The Beta angle measures the cartilaginous roof (labrum) and should be <55 degrees.
- Why (E) is wrong: The acetabular angle is a measurement used on X-rays, not ultrasound, in older infants.
Key Points: DDH Ultrasound
- Screening: Ultrasound is the gold standard until ~4–6 months (when the femoral head ossifies).
- Alpha angle: Lower angle = shallower socket = higher risk of dysplasia.
Question 14: Kohler’s Disease
Stem: A 5-year-old boy presents with mid-foot pain. Radiographs show the tarsal navicular bone is flattened, sclerotic, and fragmented. The other tarsal bones appear normal.
Question: What is the diagnosis?
(A) Freiberg’s infraction (B) Sever’s disease (C) Kohler’s disease (D) Panner’s disease (E) Kienbock’s disease
Correct Answer: (C) Kohler’s disease
Explanation:
- Why (C) is correct: Kohler’s disease is self-limiting osteochondrosis (AVN) of the tarsal navicular. It occurs in children (3–7 years).
- Why (A) is wrong: Freiberg’s is AVN of the 2nd metatarsal head (adolescent girls).
- Why (B) is wrong: Sever’s is traction apophysitis of the calcaneus.
- Why (D) is wrong: Panner’s is AVN of the capitellum of the humerus.
- Why (E) is wrong: Kienbock’s is AVN of the lunate (adults).
Key Points: Kohler’s Disease
- Clinical: Pain over the medial midfoot.
- Prognosis: Excellent; bone usually reconstitutes fully without long-term issues.
Question 15: Scurvy
Stem: A 3-year-old child with severe developmental delay and a restricted diet presents with bleeding gums and refusal to walk. Radiographs show generalized osteopenia, a dense metaphyseal line, and a lucent band just proximal to it. Small bony spurs are seen at the metaphyseal edges.
Question: The “lucent band” proximal to the dense metaphyseal line is known as:
(A) White line of Frankel (B) Wimberger’s ring (C) Pelkan spurs (D) Trummerfeld zone (E) Looser’s zones
Correct Answer: (D) Trummerfeld zone
Explanation:
- Why (D) is correct: In Scurvy (Vitamin C deficiency), the Trummerfeld zone is a lucent band of “scurvy-scorbutic” bone under the dense metaphyseal line.
- Why (A) is wrong: The “White line of Frankel” is the dense line itself (zone of provisional calcification).
- Why (B) is wrong: “Wimberger’s ring” is a dense sclerotic rim around the epiphysis.
- Why (C) is wrong: “Pelkan spurs” are the metaphyseal edge spurs.
- Why (E) is wrong: Looser’s zones (pseudofractures) are seen in Osteomalacia/Rickets.
Key Points: Scurvy
- Cause: Vitamin C deficiency (impairs collagen synthesis).
- Imaging: Dense lines, lucent bands, and subperiosteal hemorrhage (causing massive periosteal reaction during healing)
