LE6 BONES Flashcards

Question

A pelvic X-ray of a 65-year-old obese woman presenting with difficulty in ambulation shows markedly narrowed hip joints, more pronounced in the superior portion. Osteophytes are seen in the acetabular rim with sclerosis of the articulating surfaces. What is the radiologic diagnosis? A. Osteoarthritis B. Rheumatoid Arthritis C. Ankylosing Spondylitis D. Psoriatic Arthritis

Answer 1

A. Osteoarthritis Rationale: The hallmark radiologic features of osteoarthritis include joint space narrowing, osteophyte formation, and subchondral sclerosis, particularly affecting weight-bearing joints like the hip.

Answer 2

B. Rheumatoid Arthritis Rationale: Rheumatoid Arthritis commonly presents with periarticular osteopenia and soft tissue swelling, particularly in the hands, as an early radiologic finding before joint erosions or space narrowing occurs.

Answer 3

C. Ankylosing Spondylitis Rationale: The "bamboo spine" appearance is a classic finding of Ankylosing Spondylitis due to ossification of the annulus fibrosus, along with symmetrical sacroiliitis.

Answer 4

A. Epiphyses must be open Rationale: Giant Cell Tumors occur after the closure of the epiphyses. The other criteria (abutting the articular surface, well-defined non-sclerotic margin, and eccentric location) are important discriminators.

Answer 5

A. Myeloma Rationale: Multiple Myeloma does not typically show increased uptake on radionuclide bone scans because it does not provoke an osteoblastic response.

Answer 6

D. Leads to multiple calcific loose bodies in a joint Rationale: Synovial osteochondromatosis is a benign condition resulting from synovial metaplasia, leading to the formation of multiple calcified or non-calcified loose bodies in the joint.

Answer 7

D. Zone of transition Rationale: The zone of transition (the clarity of the border between normal and abnormal bone) is the most important determinant of lesion aggressiveness, with a narrow zone suggesting a benign process and a wide, ill-defined zone indicating malignancy.

Answer 8

B. Monostotic form Rationale: Monostotic Fibrous Dysplasia accounts for about 85% of cases, affecting a single bone, whereas the polyostotic form is less common.

Answer 9

D. Never has calcifications Rationale: Pigmented Villonodular Synovitis (PVNS) is a benign synovial soft tissue process that does not produce calcifications, unlike synovial osteochondromatosis.

Answer 10

B. Benign processes Rationale: A narrow zone of transition with well-defined borders is indicative of benign bone lesions, whereas aggressive lesions typically exhibit a wide transition zone.

Answer 11

D. Psoriatic Arthritis Rationale: The "pencil-in-cup" deformity, caused by marginal erosions and bone resorption, is a classic finding of Psoriatic Arthritis.

Answer 12

C. Lamellated Rationale: Aggressive periosteal reactions, such as those seen in Ewing Sarcoma, often present with a lamellated (onion-skin) appearance due to rapid periosteal irritation.

Answer 13

A. Radiographs in orthogonal views Rationale: Radiographs (X-rays) remain the first-line imaging modality for evaluating bone lesions due to their availability, cost-effectiveness, and diagnostic value.

Answer 14

C. Nasal Rationale: The nasal bone is the most commonly fractured facial bone due to its prominence and relatively thin structure.

Answer 15

D. Non-Ossifying Fibroma Rationale: A fibrous cortical defect that grows larger than 2 cm is classified as a Non-Ossifying Fibroma, which is a benign self-limiting lesion.

Answer 16

C. Fibrosarcoma Rationale: Fibrosarcoma is a lytic malignant tumor that leads to aggressive cortical destruction without osteoid or chondroid matrix production.

Answer 17

C. MRI Rationale: MRI is the gold standard for evaluating soft tissue structures, including tendons and ligaments, due to its superior contrast resolution.

Answer 18

C. Infection. Rationale: Infection (such as osteomyelitis) can present as a lucent or cystic lesion on radiographs, mimicking benign bone lesions. It is included in the F-E-G-N-O-M-A-S-H-H-I-C mnemonic, which helps in the differential diagnosis of benign lucent/cystic bone lesions.

Answer 19

D. Zone of transition Rationale: The clarity of the border between normal and abnormal bone (zone of transition) is the most reliable indicator of malignancy, with a wide, ill-defined border suggesting an aggressive lesion.

Answer 20

A. Eosinophilic granuloma Rationale: Eosinophilic granuloma can present with an aggressive, permeative appearance, often mimicking malignant bone tumors such as Ewing’s sarcoma.

Answer 21

A. Low-grade, chronic irritation Rationale: Benign periosteal reactions result from slow, chronic irritation, allowing the periosteum to lay down thick, organized bone.

Answer 22

C. Lamellated Rationale: Aggressive periosteal reactions, such as those seen in Ewing’s sarcoma, often present with a lamellated (onion-skin) appearance due to rapid periosteal irritation.

Answer 23

B. Benign processes Rationale: A narrow zone of transition with well-defined borders is indicative of benign bone lesions, whereas aggressive lesions typically exhibit a wide transition zone.

Answer 24

D. Osteosarcoma is the most common primary malignant bone tumor. Rationale: Osteosarcoma is the most common primary malignant bone tumor, particularly in adolescents and young adults.

Answer 25

B. Ewing sarcoma Rationale: Ewing sarcoma, along with osteosarcoma, is a common primary malignant bone tumor in young patients, usually affecting the diaphysis of long bones.

Answer 26

C. Myeloma Rationale: Multiple myeloma is the most common primary malignant bone tumor in older adults.

Answer 27

B. Second peak occurs in the sixth decade of life. Rationale: While osteosarcoma primarily affects young individuals, a secondary peak occurs in older adults, often associated with Paget’s disease or previous radiation.

Answer 28

A. Grows outside the bone. Rationale: Parosteal osteosarcoma arises from the periosteum and grows externally, without initial cortical destruction.

Answer 29

B. Eosinophilic granuloma is a differential diagnosis. Rationale: Ewing sarcoma, eosinophilic granuloma, and infection can appear radiologically similar, making differential diagnosis crucial.

Answer 30

B. Ewing’s sarcoma Rationale: If benign periostitis or sequestration is present, Ewing’s sarcoma is less likely because it typically presents with aggressive periosteal reactions.

Answer 31

A. Chondrosarcoma Rationale: Chondrosarcoma frequently presents with amorphous or "snowflake" calcifications due to its cartilaginous matrix.

Answer 32

B. Can have a bony sequestrum completely separated from the surrounding bone. Rationale: Fibrosarcoma is a malignant tumor that can cause extensive bone destruction and sequestration, creating a completely separated bony fragment.

Answer 33

C. Primary lymphoma of bone Rationale: Unlike most bone malignancies, primary lymphoma of the bone can be extensive without causing significant symptoms.

Answer 34

C. Renal cell carcinoma Rationale: Renal cell carcinoma produces only lytic metastatic lesions and does not cause blastic metastases.

Answer 35

A. Myeloma Rationale: Multiple Myeloma does not typically show increased uptake on radionuclide bone scans because it does not provoke an osteoblastic response.

Answer 36

D. Leads to multiple calcified loose bodies in a joint. Rationale: Synovial osteochondromatosis is a benign condition resulting from synovial metaplasia, leading to the formation of multiple calcified or non-calcified loose bodies in the joint.

Answer 37

D. Never has calcifications. Rationale: Pigmented Villonodular Synovitis (PVNS) is a benign synovial process that does not produce calcifications, unlike synovial osteochondromatosis.

Answer 38

C. Fibrosarcoma Rationale: Fibrosarcoma is a lytic malignant tumor that leads to aggressive cortical destruction without osteoid or chondroid matrix production.

Answer 39

A. Narrow zone of transition Rationale: A narrow zone of transition with well-defined borders is characteristic of benign bone lesions, whereas a wide zone indicates aggressive or malignant processes.

Answer 40

C. Expansile Rationale: Expansile lesions grow outward but maintain cortical integrity, as seen in Aneurysmal Bone Cysts and Osteoblastomas.

Answer 41

B. Monostotic form Rationale: Monostotic Fibrous Dysplasia accounts for about 85% of cases, affecting a single bone, whereas the polyostotic form is less common.

Answer 42

D. No periosteal reaction Rationale: Fibrous Dysplasia is a benign lesion that does not induce a periosteal reaction, making this a key distinguishing feature.

Answer 43

C. Phalanges Rationale: Enchondromas in the phalanges occur without soft tissue hemangiomas, distinguishing them from syndromes like Maffucci Syndrome.

Answer 44

A. Ollier Disease Rationale: Ollier Disease consists of multiple enchondromas but lacks the soft tissue hemangiomas seen in Maffucci Syndrome.

Answer 45

B. Maffucci Syndrome Rationale: Maffucci Syndrome presents with multiple enchondromas and soft tissue hemangiomas, distinguishing it from Ollier Disease, which lacks hemangiomas.

Answer 46

B. Must be less than 30 years of age Rationale: Eosinophilic Granuloma, a form of Langerhans Cell Histiocytosis, primarily affects children and young adults under 30 years old.

Answer 47

A. Epiphyses must be open Rationale: Giant Cell Tumors typically occur after physeal closure, meaning the epiphyses must be closed, not open.

Answer 48

D. Non-Ossifying Fibroma Rationale: A fibrous cortical defect that exceeds 2 cm is classified as a Non-Ossifying Fibroma, a benign lesion commonly found in children and adolescents.

Answer 49

D. Osteoblastoma Rationale: Osteoblastomas often occur in the posterior elements of the spine and are frequently associated with Aneurysmal Bone Cysts.

Answer 50

D. Both A and B (Metastases and Multiple Myeloma) Rationale: Metastatic bone disease and Multiple Myeloma are the most common bone malignancies in older adults.

Answer 51

C. Fallen Fragment Sign Rationale: The "Fallen Fragment Sign" is highly characteristic of a Solitary Bone Cyst after a pathological fracture.

Answer 52

C. Infection Rationale: Infection, particularly osteomyelitis, must always be considered in the differential diagnosis of a lucent or cystic bone lesion.

Answer 53

A. Metastasis Rationale: Metastatic bone lesions are rare in individuals under 30 unless there is a known primary malignancy.

Answer 54

A. X-ray in 2 orthogonal views Rationale: The standard initial imaging for fractures is an X-ray with at least two orthogonal views to assess alignment and displacement.

Answer 55

B. Characteristic “crescent” sign Rationale: The "Crescent Sign" on radiographs is a late-stage finding of subchondral collapse in Avascular Necrosis.

Answer 56

D. Subluxation Rationale: Subluxation refers to an incomplete or partial dislocation where the joint surfaces remain in partial contact.

Answer 57

C. Spiral fracture Rationale: Spiral fractures result from a rotational force applied to a bone, producing a helical fracture line.

Answer 58

D. Overriding Rationale: Overriding fractures occur when the fractured bone ends overlap, leading to a shortening of the limb segment.

Answer 59

B. Accessory bone Rationale: Accessory bones are normal anatomical variants that can sometimes be mistaken for avulsion fractures on radiographs.

Answer 60

C. Supracondylar fracture Rationale: The "posterior fat pad sign" is a radiographic finding that suggests an occult intra-articular fracture, most commonly a supracondylar fracture in children or a radial head fracture in adults. When the posterior fat pad is visible on a lateral elbow X-ray, it typically indicates hemarthrosis due to an underlying fracture, with supracondylar fractures being the most common in pediatric patients.

Answer 61

D. Neither A nor B Rationale: A Hill-Sachs deformity is an impaction fracture of the posterolateral humeral head due to anterior shoulder dislocation, not a fracture of the glenoid labrum or related to posterior dislocation.

Answer 62

A. Joint space narrowing, hypertrophic spurs, subchondral sclerosis Rationale: Osteoarthritis is characterized by cartilage loss (joint space narrowing), osteophyte formation, and subchondral sclerosis.

Answer 63

B. Hand Rationale: Rheumatoid arthritis most commonly affects the small joints of the hands, particularly the MCP and PIP joints.

Answer 64

A. Periarticular osteopenia, soft tissue swelling, subluxation Rationale: Rheumatoid arthritis presents with periarticular osteopenia, soft tissue swelling, and progressive joint destruction leading to subluxation.

Answer 65

C. Both A & B Rationale: Gout is characterized by tophi deposition and juxta-articular erosions with overhanging edges.

Answer 66

C. Psoriatic arthritis Rationale: The "pencil-in-cup" deformity is a radiographic feature seen in severe psoriatic arthritis due to joint erosion and bone resorption.

Answer 67

A. Legs Rationale: Osteomyelitis in children typically affects long bones, particularly the femur and tibia.

Answer 68

B. Hematogenous spread Rationale: In children, osteomyelitis most commonly spreads hematogenously from a distant infection.

Answer 69

D. Cloaca Rationale: A cloaca is an opening in the involucrum through which necrotic bone (sequestrum) can drain.

Answer 70

✅ D. Cloaca Explanation: In chronic osteomyelitis, the cloaca is the space or opening in the involucrum (new bone formation) where sequestrum (dead bone) and pus reside. This space allows the drainage of necrotic material, leading to persistent infection and sinus tract formation. Answer Choices Analysis: 🔴 A. Sequestrum → Incorrect • Sequestrum refers to the necrotic, devascularized bone fragment that remains in the infected area due to disrupted blood supply. • It is a hallmark of chronic osteomyelitis but does not describe the space where it resides. 🔴 B. Brodie’s abscess → Incorrect • Brodie’s abscess is a localized, subacute form of osteomyelitis characterized by a well-defined abscess cavity in the metaphysis of long bones, often surrounded by sclerotic bone. • It is not the space where dead bone resides in chronic osteomyelitis. 🔴 C. Involucrum → Incorrect • Involucrum is the new bone formation that surrounds the sequestrum as a reaction to infection. • It attempts to wall off the infection but does not refer to the space within it. ✅ D. Cloaca → Correct • The cloaca is the space within the involucrum where sequestrum and pus reside. • It allows pus to drain externally, forming chronic sinus tracts. • If untreated, it may lead to squamous cell carcinoma. High-Yield Chronic Osteomyelitis Features: • Sequestrum = Dead, necrotic bone fragment • Involucrum = New bone formation around infection • Cloaca = Opening in involucrum where pus & sequestrum are housed • Complications = Sinus tract formation, pathologic fractures, rarely squamous cell carcinoma 🔥 Remember: In chronic osteomyelitis, sequestrum sits inside the cloaca, which is surrounded by involucrum! 🔥 .

Answer 71

A. Hot lesion Rationale: Increased uptake on a bone scan indicates high metabolic activity, characteristic of infection, tumors, or fractures.

Answer 72

B. Staphylococcus aureus Rationale: Staphylococcus aureus is the most common pathogen responsible for osteomyelitis in both acute and chronic cases.

Answer 73

B. Brodie’s abscess Rationale: Brodie’s abscess is a form of subacute osteomyelitis that presents as a radiolucent lesion with surrounding sclerosis in long bones, often mistaken for a tumor.

Answer 74

C. Endosteal scalloping Rationale: Endosteal scalloping is caused by slow-growing lesions, such as enchondromas or myeloma, leading to progressive cortical thinning.

Answer 75

D. 40% Rationale: Approximately 40-50% of bone mineral must be lost before it becomes radiographically evident as lucency on plain films.

Answer 76

C. Involucrum Rationale: Involucrum is a reactive bone formation around a sequestrum (necrotic bone fragment) in chronic osteomyelitis.

Answer 77

A. Pott’s disease Rationale: Pott’s disease (spinal tuberculosis) involves destruction of the vertebral bodies and intervertebral disc space narrowing, leading to kyphotic deformities.

Answer 78

A. Sequestrum Rationale: Sequestrum is a dead, devascularized bone fragment that remains within an infected or inflamed area, characteristic of chronic osteomyelitis.