MSK Imaging Flashcards
Describe the radiation dose the patient receives from an X-ray for every 1000 photons
For every 1000 photons reaching the patient, 100-200 photons are scattered. Just 20 reach the image detector. The rest are absorbed by the patient.
[radiation dose ~800-900?]
______ uses continuous x-ray imaging to create a real-time look into internal structures and is useful for dynamic procedures such as injections, biopsies, angiograms, and GI evaluations
Fluoroscopy
Imaging modality made up of superimposed 2D imaging with plain radiographs; able to measure and display varying x-ray attenuations of the tissues in a section of the body by passing through the section from different angles and reconstructing the image
CT
Strengths vs. weaknesses of CT
Strengths: fast, good resolution of bony lesions, less expensive than MRI
Weaknesses: ionizing radiation, expensive, poor soft tissue contrast
Between T1 and T2 weighted MRIs, which one results in water showing up relatively bright and fat relatively dark?
T2 weighted
[T1 weighted show fat relatively bright and water relatively dark]
Between T1 and T2 weighted MRIs, which one is better for detecting pathology?
T2, because it fluid (edema) shows up bright white
[as a general rule, T1 are better for detecting anatomy, T2 are better for detecting pathology]
Strenghts vs. weaknesses of MRI
Strengths: no ionizing radiation, entire cross-sections without interference, superior soft tissue contrast
Weaknesses: subject to motion artifact, inferior to CT in detecting acute hemorrhage, inferior to CT in detection of bony injury, requires prolonged acquisition time for many images
Imaging modality used to help elucidate tears in labrum or cartilage; contrast medium is injected into joint under fluoroscopy
MRI or CT arthrogram (contrast used depends on whether it is CT or MRI)
How does a normal tendon appear on ultrasound?
Hyperechogenicity and fibrillary
Examples of MSK pathology that may be viewed using ultrasound include tendon and muscle pathologies. Ultrasound can show full thickness tears in tendons. It can also show muscle disruption +/- hematoma. How would a hematoma show up on ultrasound?
Anechoic or hypoechoic area
What is a DEXA scan and how is it generated?
Dual Energy X-ray Absorption
Radiograph tube generates photon beams of 2 different energy levels, thus the term “dual-energy”. The difference in attenuation of the 2 photon beams as they pass through body tissue of variable composition distinguishes bone from soft tissue and allows quantification of bone mineral density (BMD)
What is the difference between the uses of a T-score and a Z-score that are generated from a DEXA scan?
T-score = used for diagnosis of osteoporosis
Z-score = used to compare the patient’s bone mineral density to a population of peers
T/F: When ordering an x-ray following a minor musculoskeletal trauma in which fracture is suspected, one view is sufficient
False — one view is no view!
ALWAYS ORDER MULTIPLE VIEWS
Is a greenstick fracture considered complete or incomplete?
Incomplete — some cortex is still intact
[to be considered complete, all parts of the cortex are disrupted]
OLDACID is a mnemonic used to describe what is observed in X-ray. What does it stand for?
Open vs. Closed Location Degree of fracture Articular extension/involvement Comminution/pattern Intrinsic bone quality Displacement/angulation/rotation
_______ = fracture through the epiphyseal plate
Salter-Harris
5 classifications of Salter-Harris fractures using SALTER mnemonic
Type I: Straight across
Type II: Above
Type III: Lower (beLow)
Type IV: Two or through
Type V: ERasure fo growth plate or cRush
Condition where bone tissue forms inside muscle or other soft tissue after an injury; tends to develop in young adults and athletes who are more likely to experience traumatic injuries
Myositis ossificans
4 benign bone tumors
Giant cell tumor
Osteochondroma
Osteoblastoma
Osteoid osteoma
3 malignant bone tumors
Chondrosarcoma
Osteosarcoma
Ewing sarcoma
Benign, but locally aggressive and destructive bone tumor composed of multinucleate osteoclast-type cells; usually solitary and seen in 20s-40s at the epiphyseal end of long bones, typically around the knee and have “soap bubble” appearance on X-ray
Giant cell tumor
Giant cell tumors most commonly affect the ______ part of long bones, usually around the _____ joint.
They often cause ______-like symptoms but pts may present with pathologic fractures. They have _________-appearance on X-ray
Epiphyseal; knee
Arthritis; soap-bubble
Most common benign bone tumor; most commonly solitary and seen in men and diagnosed in late adolescence through early adulthood; commonly pedunculated and between 1-20 cm, arising from metaphysis of long tubular bones, particularly around the knee
Osteochondroma
Clinical presentation of osteochondroma
Frequently diagnosed incidentaly, but may present as a slow-growing mass which can be painful if it impinges a nerve or if the stalk is fractured
Osteochondromas most commonly arise from the ______ of long bones, particularly around the ____ joint
Metaphysis; knee
What is the difference between osteoid osteoma and osteoblastoma in terms of size, site of origin, presentation, and ASA responsiveness?
Osteoid osteomas are <2cm, originate in appendicular skeleton, and present with severe nocturnal pain that is relieved by ASA and other NSAIDs
Osteoblastomas are >2cm, originate in posterior spine, and present with chronic pain that is unresponsive to ASA
Malignant cartilage-producing tumor most commonly seen in men who are in their 40s or older; most commonly in axial skeleton (pelvis, ribs, shoulder), and presents as painful, progressively enlarging mass
Chondrosarcoma
Malignant osteoid matrix-producing bone tumor that is the most common primary malignant tumor of bone; bimodal age distribution in <20 and again in older adults. Most commonly arise from metaphysis of long bones of extremities (often the knee). Presents as painful, progressively enlarging mass
Osteosarcoma
Osteosarcomas most commonly arise from the _____ of long bones of the extremities.
They are associated with mutations in ____ and ____.
They have a _______ pattern and ______ _______ on plain film
Metaphysis
RB; TP53
“Sunburst”; “Codman Triangle”
Malignant, primitive neuroectodermal tumor commonly arising from diaphysis of long bones (femur) and flat bones of the pelvis in white males <20 y/o; presents as painful enlarging mass with affected site often being warm, swollen, and tender
Ewing sarcoma
Ewing sarcoma commonly arises from the _____ of long bones like the femur, and the flat bones of the pelvis.
It is associated with a ______ translocation, CD-99 positivity, and a _______ appearance on plain film
Diaphysis
(11;22); “Onion skin”
3 pathways for organisms to reach bone
- Hematogenous spread
- Extension from a contiguous site
- Direct implantation (trauma or surgery)
Most common cause of pyogenic osteomyelitis
Staph aureus
Etiology of osteomyelitis to consider in an IV drug user
Staph aureus
3 etiologies of osteomyelitis to consider in UTI-associated osteomyelitis
E.coli
Pseudomonas
Klebsiella
2 etiologies to consider with osteomyelitis in neonates
H.influenzae
Group B strep
Etiology of osteomyelitis to consider in pt with sickle cell disease
Salmonella
Etiology of osteomyelitis to consider in sexually active young adults
N.gonorrhea
Describe progression of hematogenous osteomyelitis to sequestra (separation of dead bone)
Inflammatory exudate within marrow —> increased intramedullary pressure —> extension of exudate into cortex —> rupture of periosteum —> interruption of periosteal blood supply —> necrosis —> sequestra
What is the imaging modality of choice for <2 weeks of symptoms + suggestive clinical history of osteomyelitis?
X-ray, followed by MRI if it looks like osteomyelitis
[if symptoms have been going on >2 weeks, do MRI right away]
What bone disease is characterized by function-limiting pain, effect on walking distances, pain at night or rest, activity induced swelling, stiffness, mechanical issues like instability, locking, and catching?
Osteoarthritis
Radiographic evidence of osteoarthritis
Joint space narrowing Osteophytes Eburnation of bone Subchondral sclerosis Subchondral cysts
What bone disease is characterized by morning stiffness >1h, swelling in >3 joints, nodules, bony erosions and decalcification, symmetric arthritis, and often affects MCP, PIP, and wrist?
Rheumatoid arthritis
Rheumatoid arthritis appearance on radiographs vs. MRI
Radiographs show periarticular erosions
MRI shows soft tissue inflammation and pannus
Clinical manifestations of rheumatoid arthritis are similar to arthralgia secondary to _______ infection, except in the latter: symptoms usually last no more than 1-2 weeks, and patients may present with fever and other systemic findings
Parvovirus
T scores associated with osteopenia vs. osteoporosis
Osteopenia = L2-4 lumbar density of 1.0-2.5 standard deviations below the peak bone mass of a 25 year old individual (T score of -1 to -2.5)
Osteoporosis = L2-4 lumbar density >2.5 standard deviations below the peak bone mass of a 25 year old individual (T score < -2.5)
What bone disease may present with arthritis in the hands, dactylitis, onychodystrophy, onycholysis, chronic uveitis, entheses such as achilles tendonitis, posterior tibial tendonitis, and plantar fascitis in the setting of rash on extensor surfaces?
Psoriatic arthritis
Radiographic hallmark of psoriatic arthritis
Pencil-in-cup deformity
Bone disease caused by imbalance of osteoblastic and osteoclastic activity, causing an increase in disordered and structurally unsound bone mass; presents with elevated alkaline phosphatase with normal calcium and phosphorus, and mosaic pattern of lamellar bone on histology
Paget disease
In terms of imaging when paget disease is suspected, _______ can be diagnostic, while ________ is useful for staging
X-ray; Radionuclide bone scan
What are 2 long term complications of paget disease?
High-output heart failure secondary to AV shunts
Increased risk of osteosarcoma
Untreated, symptomatic hyperparathyroidism can lead to what 3 bone pathologies?
Osteoporosis
Brown tumors
Osteitis fibrosa cystica
What bone disease presents with bone pain and plain film findings including subperiosteal bone resorption on radial aspect of middle phalanges, tapering of distal clavicles, “salt and pepper” appearance of the skull, bone cysts, and brown tumors of the long bones?
Osteitis fibrosa cystica
Group of diseases characterized by a reduction of bone resorption and diffuse, symmetric skeletal sclerosis secondary to impaired osteoclasts; most commonly due to carbonic anhydrase II mutation. Pts may be asymptomatic or present with fracture, pancytopenia, or extramedullary hematopoiesis
Osteopetrosis
