Page 15 Flashcards
Only lesion in FEGNOMASHIC that is ALWAYS CENTRAL in location
Solitary/simple/unicameral bone cyst
What are the 4 aspects of bone lesion that need to be examined to assess if it is benign or malignant?
Cortical destruction, periostitis, orientation/axis, zone of transition
What is the most useful of the 4 bone lesion criteria and why?
Zone of transition - easier to characterize (narrow/wide) and always present to evaluate
What benign conditions can cause aggressive periostitis?
Infection, EG, ABC, osteoid osteoma, trauma
What should we keep in mind about periostitis when determining if a lesion is benign or malignant?
Many benign lesions can cause aggressive periostitis, but malignant lesions will never cause benign periostitis
How do bone and soft tissue tumors usually appear on MRI?
Low T1, high T2 (similar to fluid); except MFH, desmoid, calcifications - low T1/T2
What is the usefulness of Gd in assessing msk tumors?
Differentiate solid mass vs fluid collection; solid-diffuse enh, fluid-peripheral enh
How do you differentiate central and parosteal osteosarcoma?
Central-destructive, usu in ends of long bones, Parosteal-originates from periosteum, grows outside of bone
Why is it important to distinguish parosteal osteosarcoma?
Considered not as aggressive or as deadly, but once it violates the cortex, it is considered as aggressive as central osteosarc
What is the role of cross-sectional imaging in parosteal osteosarcoma?
CT/MR used to assess for invasion of adjacent cortex; if with invasion - aggressive
What are the classic differential diagnoses for a permeative lesion in a child?
Ewing sarcoma, infection, EG
What are two mimickers of parosteal osteosarcoma?
Cortical desmoid, myositis ossificans
How do you differentiate Ewing Sarcoma and primary lymphoma of bone, which look identical radiographically?
Ewing-younger age group, symptomatic, PLOB-older age group, asymptomatic
What is the only primary tumor that virtually never presents with blastic metastatic disease?
Renal cell carcinoma
What are the two tumors that are homogeneously bright on T2 (resembling fluid collections)?
Neural tumors, synovial sarcomas
What is pathognomonic of synovial osteochondromatosis?
multiple calcific loose bodies in a joint
How do you differentiate chondrosarcoma from benign enchondroma?
Soft tissue mass or edema - unlikely to be enchondroma
The only malignant tumor that can involve a large amount of bone while the patient is asymptomatic
primary lymphoma of bone
How do we differentiate synovial sarcomas from fluid collections?
High T2, in a location atypical for ganglion/bursa, +gd to prove it’s solid
How do we differentiate PVNS from synovial osteochondromatosis?
PVNS virtually never has calcifications
Traumatic anterolisthesis of C2 over C3 with fracture of the posterior elements of C2
Hangman’s fracture
e Anterior compression of a vertebral body and avulsion fracture due to severe flexion of the cervical spine and disruption of the posterior ligaments
Flexion teardrop fracture
Oblique fracture of the spinous process of the 6th cervical - 3rd thoracic vertebrae that results from avuslsion by the supraspinous ligament
Clay-shoveler’s fracture
…mallet / baseball finger?
avulsion fracture at base of distal phalanx, involves extensor digitorum tendon - if not treated will result in flexion deformity
…gamekeeper’s thumb?
avulsion on ulnar aspect of first MCP joint - ulnar collateral ligament of thumb inserts - will impair normal fxn of thumb
…lunate/perilunate dislocation?
Failure to treat may result in permanent median nerve impairment
Why is surgical fixation important for Bennett/Rolando fracture?
Fracture of 1st carpometacarpal joint where adductors insert - require orif to keep alignment
How do you differentiate a Bennett vs Rolando fracture?
Base of thumb fracture with joint involvement; bennett-not comminuted, rolando-comminuted, pseudo-bennett-comminuted but not intraarticular
Mechanism of injury for lunate/perilunate dislocation?
FOOSH
Why is it important to catch a scaphoid fracture
High risk of AVN of the proximal pole, since vascular supply starts distally, and a fracture interrupts blood supply to the proximal pole
What is the view used to evaluate the hook of the hamate?
Carpal tunnel view
How to differentiate lunate and perilunate dislocation?
perilunate-capitate and the rest are dorsally displaced, lunate-only lunate is displaced volarly
What is AVN of the lunate called?
Kienbock malacia
What wrist pathology is associated with negative ulnar variance? positive ulnar variance?
Negative-Kienbock malacia; Positive-TFCC tears
Subluxation of the radial head in children, which is usually but not invariably transient
nursemaid’s elbow or pulled elbow
How do you differentiate Colles and Smith fractures?
Colles-dorsal angulation, more common; Smith-volar angulation, less common
How do you differentiate Monteggia and Galleazi fractures?
GRIMUS - Galeazzi radial fracture, inferior disloc of ulna; Monteggia ulnar fracture, superior disloc of radius
What should we keep in mind when we see forearm fractures?
Forearm bones are a two-bone system similar to a ring bone; if there is a fracture in one bone, look for another fracture or dislocation in the other. So for forearm fractures, examine the elbow for dislocation!
Most likely fracture site if (+) posterior fat pad in adults? in children?
adults - radial head; children - supracondylar fracture
What is a helpful indicator of occult elbow fractures?
Displaced posterior fat pad - in the setting of trauma, even if fracture line is not definitely identified, still treated as fracture
Aside from fracture, what other pathologies can also displace the posterior fat pad? This is why clinical setting is important!
Infection, arthritides, any elbow effusion
How do you diagnose pseudodislocation of the shoulder?
Humeral head displaced inferolaterally; in anterior disloc, HH is displaced inferomedially
Why is it important to properly diagnose a pseudodislocation?
Cause is traumatic hemarthrosis, do not attempt to reduce the dislocation; may also suggest occult humeral head fracture
How do you differentiate sacral stress fractures from mets?
Characteristic location, appearance, history of previous RT, seeing a cortical break; if bilateral, Honda sign in radionuclide scan (H logo of honda)
Why are avulsion injuries important to diagnose?
They may appear aggressive and mimic malignant lesions, but are “do not touch” lesions, so impt to diagnose so they don’t biopsy
What are common sites of avulsion injuries in the hip?
Ischium, ASIS, AIIS, iliac crest
What are the hallmarks of DJD?
Sclerosis, joint space narrowing, osteophytosis
What joints can have erosions as a result of DJD?
TMJ, AC joint, symphysis pubis, SI joint
Why is it important to diagnose stress fractures? Give 2 reasons
May appear aggressive, with aggressive periostitis, DO NOT BIOPSY; may progress to complete fractures
How do stress fractures appear?
Sclerosis in weightbearing bone with horizontal/oblique linear pattern - considered as stress fracture until proven otherwise
What view should we look at if we consider a tibial plateau fracture?
Cross-table lateral view to check for fat-fluid level
What is a Lisfranc fracture-dislocation and how do we diagnose it?
fracture-disloc of tarsometatarsals; check alignment of 2nd MT and 2nd cuneiform
What are examples of stress fractures?
Femoral neck stress fracture - most severe; femoral diaphysis, tibia, calcaneal stress fractures
Classic triad of CPPD
pain, cartilage calcification, joint destruction
What do we measure to assess if there is a calcaneal (compression) fracture?
Bohler angle, normal is 20-40 degrees; below 20 is suggestive of compression of the calcaneus
What should we keep in mind in elderly patients with hip pain after trauma?
High index of suspicion for fracture, negative film does not exclude femoral neck fracture; MR to detect occult fracture
Migration of femoral head in RA versus OA
RA - axial; OA - superolateral
Classic triad of Charcot joint
joint destruction, dislocation, heterotopic new bone
only fat pad around the hip that gets displaced with an effusion (uncommonly seen)
obturator internus
Earliest sign of AVN
joint effusion
Signs of AVN in temporal order
patchy or mottled density / sclerosis -> subchondral lucency (often not present) -> collapse of articular surface and joint fragmentation
Triad of radiographic findings characteristic of TB arthritis?
Phemister’s triad: juxta-articular osteoporosis, peripherally located osseous erosions, and gradual narrowing of the interosseous space
The only one of the four disorders in which geodes are found, that can have a normal joint and have a geode
AVN
flexion at the proximal interphalangeal joints and hyperextension at the distal interphalangeal joints
boutonnière deformity
hyperextension at the proximal interphalangeal joints and flexion at the distal interphalangeal joints
swan-neck deformity
flexion at the metacarpophalangeal joint and hyperextension at the interphalangeal joint
hitchhiker’s, or Z-shaped, deformity of the thumb (also a form of boutonniere)
loosening of the distal attachment of the extensor tendon to the distal phalanx
mallet or drop finger
radial deviation of the wrist and ulnar deviation at the metacarpophalangeal joints
zigzag deformity
Where is the main radiographic finding in osteoporosis (cortical thinning) most reliably demonstrated?
2nd metacarpal at the mid-diaphysis (should be 1/4 to 1/3 the thickness of the metacarpal)
Why is aggressive osteoporosis considered a pseudopermeative lesion? How do you differentiate it from a true permeative lesion?
Intracortical holes may have a permeative/moth-eaten appearance; true permeative lesions have medullary involvement, while pseudopermeative only involves the cortex
What are the 3 differentials for pseudopermeative lesion?
Aggressive osteoporosis, hemangioma, radiation
What is the most common cause of osteomalacia?
Renal osteodystrophy
What is pathognomonic for osteomalacia?
Looser fractures - fracture through large osteoid seams
What are radiologic features of rickets in children?
Flared and irregular epiphyses, bending of long bones
What is pathognomonic for hyperparathyroidism and where do we usually see this?
Subperiosteal bone resorption, most commonly seen in the radial aspect of the middle phalanges of the hand
What are radiologic features of hyperparathyroidism?
Subperiosteal bone resorption, diffuse osteosclerosis, rugger-jersey spine, brown tumors
What are radiologic features of hypoparathyroidism?
Calvarial thickening, basal ganglia calci
How do you differentiate pseudohypoPTH and pseudopseudohypoPTH?
PseudohypoPTH have congenitally-resistant end-organs, while pseudopseudo have the same morphologic features but no end-organ resistance
What is the effect of thyroid function on bones?
Affects skeletal maturation; hyperthyroidism-increased skeletal maturation, thyroid acropachy; hypothyroidism-delayed skeletal maturation, cretinism
How does thyroid acropachy look like? (And honestly, why is it called that??)
Periostitis in the metacarpals and phalanges, usually ulnar aspect of 5th MC
How do epiphyses look like in hypothyroidism?
Delayed ossification of epiphyses - stippled epiphyses; delayed closure or failed closure at 3rd-4th decade
What are the characteristic features of acromegaly? (In the head? body?)
Head: calvarial thickening (frontal bossing), enlarged sinuses, enlarged sella turcica, prognathic jaw; body: hypertrophic phalangeal tufts (spade tufts), joint space hypertrophy, soft tissue hypertrophy
What do you call the appearance of vertebral bodies in osteopetrosis?
Bone-in-bone appearance, sandwich vertebrae
How do you differentiate gigantism from acromegaly?
Gigantism-before epiphyses close; acromegaly-after epiphyses close
What are the different entities that present with osteosclerosis? (There are 10 usual ddx)
Regular sex makes occasional perversions much more pleasurable and fantastic. 1 renal osteodystrophy, 2 sickle cell disease, 3 myelofibrosis, 4 osteopetrosis, 5 pyknodysostosis, 6 mets, 7 mastocystosis, 8 paget dse, 9 athletes, 10 fluorosis
What are the two types of osteopetrosis?
Osteopetrosis congenita-presents earlier, can be lethal; Osteopetrosis tarda-presents later, milder form
What are other radiologic findings associated with sickle cell disease?
Osteosclerosis, bone infarcts, fish vertebrae, hip AVN
What is the pathognomonic feature of pyknodysostosis (aka Toulouse-Lautrec syndrome)?
acro-osteolysis (resorption of distal phalanx, usually tuft) with sclerosis; distal phalanges appear as sharpened chalk
How do you differentiate sandwich vertebrae from rugger jersey spine?
Sandwich vertebrae - denser, more sharply defined; Sandwich - osteopetrosis, rugger jersey - hyperPTH
What types of carcinoma usually present with osteoblastic mets?
Prostate and breast, usually with cortical destruction or lytic component
What are the 3 phases of paget disease?
Lytic, sclerotic, mixed lytic-sclerotic
How can you differentiate Paget disease from others?
Paget usually starts at the end of a long bone (except tibia) - so if lesion is in the middle, doesn’t extend to the end of the bone, exclude Paget
Where is Paget disease usually seen?
MC in pelvis, iliopectineal line usually thickened
What is a characteristic feature of fluorosis, usually seen in the hip?
Ligamentous calcification, especially of the sacrotuberous ligament
What is the typical radiographic appearance of myositis ossificans?
Circumferential calci with lucent center
Where is the dorsal defect of the patella usually located?
Upper outer quadrant
How do you differentiate bone islands from sclerotic mets?
Bone islands - oblong, with long axis in teh axis of stress on the bone, margins show bony trabeculae, spiculated
What are the mimickers of dorsal defect of the patella?
Infection, osteochondritis dissecans
Differentiate the patyspondyly seen in Morquio syndrome vs Hurler and Hunter syndromes
Morquio - position of beak/bony projection is central anterior; Hurler and Hunter - position of beak is anteroinferior
Ddx for periostitis in a long bone w/o an underlying bony abnormality
hypertrophic pulmonary osteoarthropathy, venous stasis, thyroid acropachy, pachydermoperiostosis, trauma
Differentiate transient osteoporosis of the hip and AVN
TOH - edema is greater than with AVN and no well-demarcated margin is present
Where do overlooked tears frequently occur when ACL tears are present?
periphery of the meniscys and posterior horn of the lateral meniscus
Insertion of the ACL
medial tibial spine
Is discoid meniscus more common in the lateral or in the medial meniscus?
more common in the lateral meniscus
3 parts of the lateral collateral ligament (LCL) and their insertion
- tendon of the biceps femoris - most posterior (head of the fibula)
- fibular collateral ligament - true LCL (head of the fibula)
- iliotibial band - most anterior (Gerdy tubercle of the tibia)
3 tendons that make up the pes anserinus
sartorius, gracilis, semitendinosus
On which side does the partial cuff tear occur more commonly?
Articular side
What is the most commonly seen cuff tear on MRI?
Rim rent tear - articular-sided partial tear, occurs at the insertion of the cuff fibers onto the greater tuberosity
Two normal variants in the anterosuperior labrum that can mimic a torn or detached labrum
sublabral foramen/recess and Buford complex
Differentiate sublabral recess and SLAP tear
sublabral recess-smooth and extends medially; SLAP tear-more irregular and extends superiorly and laterally
What are borders of the quadrilateral space?
teres minor superiorly, teres major inferiorly, long head of the triceps medially, and diaphysis of the humerus laterally
What muscles does the axillary nerve innervate?
teres minor and deltoid
What do you call a small bony avulsion off the fibula?
flake fracture
Joint classification according to the extent of motion
synarthroses: fixed or rigid joints, amphiarthroses: slightly movable joints, diarthroses: freely movable joints
Diseases Earliest recognizable pathologic abnormality in RA
acute synovitis
3 early radiographic signs/characteristics of RA
ST swelling, regional/periarticular osteoporosis, joint space narrowing
Ivory vertebral body is seen in Paget’s disease, mets, and lymphoma. When do you favor Paget’s disease?
If vertebra is enlarged, diagnosis of Paget’s is usually ensured.
Ankylosis in TB arthritis vs pyogenic arhthritis
usually fibrous ankylosis in TB arthritis; usually bony ankylosis in pyogenic arthritis
How can you differentiate TB arthritis and RA which both present with marginal erosions?
In TB, there is relative preservation of joint space. In RA, early loss of articular space is more typical.
Isolated craniosynostoses
- sagittal suture (mc) increased AP diameter of the skull and decreased biparietal diameter
- bilateral coronal suture skull that is short in its AP diameter, often with a decrease in the depth of the orbits and maxillary hypoplasia
- unilateral coronal suture flatterning of the orbit on the involved side, best seen on SMV view; on frontal x-ray, harlequin-shaped orbit
- unilateral lambdoid suture plagiocephaly; flattening of one side of the back of the head
- metopic suture triangular forehead with hypotelorism
