Musculoskeletal and joint imaging Flashcards
Explain the difference between primary and secondary osteoarthritis.
Primary osteoarthritis occurs without a known underlying cause and is related to aging and wear-and-tear, while secondary osteoarthritis results from predisposing factors such as trauma, congenital abnormalities, or metabolic conditions.
Describe the radiographic features of aggressive versus non-aggressive bone lesions.
Aggressive lesions show permeative or moth-eaten bone destruction, interrupted periosteal reaction (e.g., Codman’s triangle), and soft tissue invasion, while non-aggressive lesions display well-defined borders, solid periosteal reaction, and lack of soft tissue extension.
What are the key MRI sequences used in musculoskeletal imaging and their purposes?
T1-weighted images provide detailed anatomical structures and fat signals; T2-weighted images highlight fluid and edema; STIR (Short Tau Inversion Recovery) suppresses fat signals to enhance fluid detection; Gradient Echo (GRE) is used for detecting hemorrhage or calcification.
Describe the pathophysiology and imaging findings of avascular necrosis (AVN).
AVN results from compromised blood supply leading to bone cell death. Early MRI findings include double-line signs on T2-weighted images, while late-stage radiographs show subchondral collapse (crescent sign) and sclerosis.
What distinguishes an osteoid osteoma from an osteoblastoma?
Osteoid osteoma is a benign bone tumor (<2 cm) with a central nidus surrounded by reactive bone, typically causing night pain relieved by NSAIDs. Osteoblastoma is larger (>2 cm), less painful, and commonly affects the spine.
List and describe the five Salter-Harris fracture types.
Type I: Fracture through the physis (growth plate); Type II: Fracture through physis and metaphysis; Type III: Fracture through physis and epiphysis; Type IV: Fracture through all three components; Type V: Crush injury to the physis.
What is the radiological “double density sign”,” and what condition does it indicate?,The double density sign indicates a bony density overlying normal bone, commonly associated with osteoid osteoma due to its central nidus surrounded by sclerotic bone.
How does MRI differentiate between acute and chronic osteomyelitis?
Acute osteomyelitis shows marrow edema on T2-weighted images with low T1 signals. Chronic osteomyelitis may present with sequestrum (dead bone), involucrum (new bone formation), and sinus tracts.
What is the difference between enchondroma and chondrosarcoma on imaging?
Enchondromas are benign, well-defined, with stippled calcifications and no cortical destruction. Chondrosarcomas show aggressive features like cortical erosion, soft tissue extension, and endosteal scalloping.
Describe the three patterns of bone destruction and their clinical significance.
Geographic: well-defined and slow-growing; moth-eaten: aggressive with irregular margins; permeative: highly aggressive with multiple small areas of bone destruction.
Which imaging modality is most sensitive for detecting early bone marrow changes?
Magnetic resonance imaging (MRI) is the most sensitive for detecting early bone marrow abnormalities such as edema and infiltration.
What are the imaging hallmarks of ankylosing spondylitis?
Bamboo spine appearance due to syndesmophyte formation, sacroiliitis with joint space narrowing, and facet joint ankylosis.
Explain the difference between lytic and sclerotic metastases on imaging.
Lytic metastases cause bone destruction and radiolucent areas (e.g., lung, thyroid cancer), while sclerotic metastases cause increased bone density and radiopaque lesions (e.g., prostate, breast cancer).
What are the imaging findings of Paget’s disease in different stages?
Lytic stage: Osteolysis and “blade of grass” sign; Mixed stage: Cortical thickening and trabecular coarsening; Sclerotic stage: Bone enlargement and ivory vertebrae.
What are the classic radiological signs of osteomyelitis on plain films?
Early: Soft tissue swelling and periosteal reaction; Late: Sequestrum (dead bone), involucrum (new bone), and cloaca (draining sinus).
How does Ewing’s sarcoma typically present on imaging?
It presents with a permeative or moth-eaten pattern of bone destruction, onion skin periosteal reaction, and soft tissue mass in the diaphysis of long bones.
Describe the MRI findings of rotator cuff tears.
Full-thickness tears show discontinuity of tendons with fluid in the gap on T2-weighted images, while partial-thickness tears show focal high signal intensity within the tendon.
What is a stress fracture
and how does it appear on imaging?,A stress fracture is a fatigue-induced fracture due to repetitive mechanical stress. It may initially be occult on plain films but appears as periosteal reaction or sclerosis later; MRI detects early marrow edema.
What are the characteristic radiological signs of gouty arthritis?
Punched-out erosions with sclerotic margins, overhanging edges, and soft tissue masses due to tophi deposition.
What distinguishes a pathologic fracture from a traumatic fracture?
A pathologic fracture occurs through weakened bone due to an underlying disease (e.g., metastasis, osteoporosis), while a traumatic fracture results from direct mechanical force on normal bone.
