MSK Radiology Flashcards
What’s the initial modality for MSK complains?
X-ray (radiography)
X-ray
Images obtained by projecting X-ray beams through a subject onto an image detector
Available on film/digital
Indications of radiography
Fractures, dislocations, bone fixation, arthritis, bone tumors, skeletal dysplasia
Contraindications of X-ray
Exclusively soft tissue injuries, early presentation of certain soft tissue conditions, primarily medullary bone diseases, caution with excessive repeat images and unnecessary radiation
Advantages of radiography
Readily available, reproducible, inexpensive, patient ease cause happens in seconds, don’t need technical training to to interpret, can do real-time radiography (fluoroscopy can help)
Limitations of radiography
Images are larger than subject and must be calibrated, superimposed structures (3D data creating a 2D image), exposure, low sensitivity for subtle fractures and soft tissue injuries
Principle views of radiography
Posterior/Anterior or Anterior/Posterior, lateral, obliques, may need to supplement views specific to site
Computed tomography (CT)
Sophisticated X-rays, uses X-rays and produce tomographic images (imaging in sections and then formatted into cross sectional cuts)
Contrast mediums- iodinate materials, barium and air
Indications of CT
Combine with contrast medium to image joints, stereotactic frame (biopsies, surgical planning, radiation therapy), angiography, staging of complex fractures, small intraarticular fragments/loose bodies, fracture healing, bone tumors
Contraindications of CT
Unnecessary imaging, significant metal in the area, allergy or inability to tolerate contrast dye (renal insufficiency), pregnancy should be avoided unless severe
Advantages of CT
Tomography, best bone Assessment modality, higher contrast resolution images (avoid overlapping structures), digital nature allows for reconstruction, interventional options, well tolerated and generally quick
Limitations of CT
Artifacts so blurring from patient movement, beam hardening from hardware, limited use for soft tissue, requires large physical site, limitation on size (300-400 lbs), higher cost than X-ray, radiation exposure, claustrophobia
Views of CT
Sagittal (divide right and left), coronal (divide Anterior and Posterior), axial (horizontal so divides superior and inferior)
MRI has similar planes
MRI
Images produced by reconstruction of data set, utilizes strong magnetic field with radio frequency pulses and collects differences in tissue signal intensity, performed with patient usually supine and by the specific body site
Advantages of MRI
Superior contrast resolution, ideal for soft tissue pathology while still good for bone, highly sensitive, contrast compounds generally safer than CT contrast medium (because gadolinium based)
Limitations of MRI
More severe artifact than CT (motion and metal), large shielded imaging suite, magnetic field, claustrophobia, expensive, one exam for one body part and average time is 45 min
Indications of MRI
Intrarticular soft tissue structures, MR arthrograhy, superior sensitivity in diagnosis of early detection of bone marrow conditions, stress fractures and malignancy, more of a problem solving tool
Contraindications of MRI
Pacemakers, mechanical pumps, electric stimulators, foreign bodies in eye, any other metal products
What’s the difference between T1 and T2 MRI?
T1 is better for anatomic Assessment because fat is bright and fluid is dark (1 Big Mac to be fat)
T2 is better for fluid Assessment so fat and fluid are both right and highlight soft tissue injuries
Ultrasound
Sound waves produce images, transducer transmit sounds and detects reflected sound waves, tomographic, echogenicity frequency of sound waves (low is cystic, high is solid mass), doppler measures motion
Advantages of ultrasound
Beneficial for soft tissue (tendons and muscles), low cost, well tolerated, no known harmful effects, highly protable, unossified epiphyses
Limitations of ultrasound
Artifacts, not available everywhere, limited by skills of provider, minimal use in evaluating bone
Indications for ultrasound
Often study of choice in infant for multiple conditions, soft tissue conditions in adults, guided assistance for joint infections, biopsies, soft tissue drainage
Contraindications of ultrasound
NONE in orthopedics
Nuclear scintigraphy
Nuclear medicine imaging, most common is bone scan (IV injection of radioisotope bound to phosphate as a tracer, imaging can then be seen between 1 min and 24 hours after)
Tracer will distribute in metabolically active bone at 2-4 hours
Can be single view of cross-sectional
Indications for bone scan
Osteomyelitis, metastases, bone tumors, occult fractures
Contraindications of bone scan
Avoid in children and pregnant women when possible
Advantages of bone scan
Very sensitive for skeletal pathology (because if its negative for something there is nothing there), mildly sensitive for soft tissue concerns
Limitations of bone scan
Non-specific, lack detail, lower sensitivity in early fractures with slow healing potential, used in combo with other imaging, radiation exposure
Types of complete fractures
Transverse, oblique, spiral, avulsion, comminuted (multiple pieces)
Types of incomplete fractures
Torus (buckle), greenstick, bowing
Why do kids get incomplete fractures?
Periosteum
What is the periosteum?
Part of the bone that is more metabolically more active and promotes callus formation and remodeling activity
Thicker and more durable, less likelihood of displacement and gives the unique fracture presentations
Where do you see compression fractures the most?
Spine
Salter-Harris classification of fractures (in skeletally immature patients)
I-separate (runs along physis/growth plate)
II- above (through metaphysis- which is proximal to growth plate)
III-lower (goes out epiphysis which is distal to growth plate)
IV- through (through 2 levels)
V-reduced (crushing and erasing of growth plate)
Concerning features of bone tumors and lesions
Indistinct margins, abnormal periosteal reaction, soft tissue mass/invasion, rapid growth, pathologic fracture
Terms of displacement
Nondisplaced and displaced Translation (often referred to as displacement)- use percents Angulation Rotation Shortening Bayonetted (overlap) Distracted/impacted
Occult fracture
Fracture of a bone that is difficult to see on an xray so it tends to be missed (scaphoid is common)
Contributing factors to fracture malunion or nonunion
Use of oral steroids, poor bone contact, loss of bone, interruption of blood supply, excessive motion, age, poor nutrition, tobacco use
