MSK Flashcards
Diagnosis?
MR appearance?
Cause?
Elastofibroma dorsi.
The fibrous component is low on T1 and T2, with interspersed fat. Low level heterogeneous contrast enhancement.
A degenerative fibrous pseudotumor with abundant collagen, a result of mechanical irritation (> 55 years, more common in women). Seen in the infrascapular region, deep to the serratus anterior and latissimus dorsi. Often bilateral.
Diagnosis?
Rheumatoid arthritis.
Diagnosis and sign?
AVN.
The “double line sign” is frequently seen on T2 weighted images in AVN (and bone infarcts) due to an inner bright line of granulation tissue next to an outer dark line of sclerotic bone.
Diagnosis?
What must be intact for this appearance to occur?
Bucket handle meniscal tear (80% are medial meniscus). Highly specific but variable sensitivity for bucket handle tear.
The ACL must be intact for the tear to look like this- in order to prevent the fragment from migrating further laterally.
Diagnosis?
Trans-scaphoid perilunate dislocation.
This injury is associated with scapholunate and radiocapitate ligament tears.
Diagnosis?
Monteggia fracture/dislocation - proximal ulnar fracture, radial dislocation (usually anterior). Due to fall on outstretched hand.
Diagnosis?
Galeazzi fracture/dislocation. Due to fall on outstretched hand with pronated forearm. Distal radial diaphysis fracture, ulnar dislocation at DRUJ (typically dorsal).
Risk of fracture nonunion, entrapment of the extensor carpi ulnaris tendon.
Diagnosis?
MRI findings?
Chondroblastoma. Benign cartilaginous neoplasm common in the 2nd-3rd decades of life.
Circumscribed osteolytic leseion in the epiphysis with a sclerotic rim. Can have calcified chondroid matrix (30-50%). MRI: signal typical of cartilage- low to intermediate T1, intermediate to high T2. Surrounding edema common.
Diagnosis?
What is it?
Chondroblastoma.
A benign cartilaginous neoplasm, common in the 2nd-3rd decades of life. Arises in the epiphyses of long bones. Calcified chondroid matrix seen in 30-50% of chondroblastomas.
Diagnosis?
Common presentation?
Talocalcaneal coalition- talar beaking with absence of the middle facet of the subtalar joint. 2nd most common type of coalition (after calcaneo-navicular), can be osseous, fibrous, or cartilaginous.
May present with peroneal spastic flatfoot.
What is Preiser’s disease?
Scaphoid osteonecrosis in the absence of prior trauma.
(Note - post fracture, osteonecrosis occurs in the proximal pole of the scaphoid due to distal to proximal blood flow. Sclerosis on xray, low T1 and T2 on MRI)
How is a discoid meniscus diagnosed?
What is different about the diagnosis of a tear in a discoid meniscus?
Redundant meniscal tissue covering a large portion of the femoral-tibial articular surface. Suggested by the identification of meniscal tissue on 3 continuous sagittal 5 mm slices OR a meniscal body >15 mm wide or extending into the intercondylar notch on coronal images. More common laterally.
A symptomatic knee with abnormal signal within a discoid meniscus is considered a tear regardless of articular surface extension.
Diagnosis?
What is it?
Non-ossifying fibroma. (if smaller called fibrous cortical defect, aka MFD)
The most common of benign fibrous bone lesions, common in children and adolescents (peak incidence 10-15 years). They are usually not seen beyond the age of 30, as they spontaneously heal being gradually filled in by bone.
Diagnosis?
Imaging findings?
Cause?
Dorsal intercalated segmental instability (DISI).
See dorsal tilt of the lunate on lateral view (>20º relative to capitate), widening of the scapholunate interval (>5 mm) on PA view.
Occurs as a result of disruption of the dorsal intercarpal ligament. Causes include carpal bone fracture (most commonly scaphoid) and scapholunate ligament dissociation.
Diagnosis?
Differential?
Superior labral anterior-posterior (SLAP) tear. Extends laterally along the labrum, vs a sublabral sulcus which extends medially. Not associated with shoulder instability. Many types.
Differentiate from:
Superior sublabral sulcus = normal variant of the superior sublabral recess, which is normally present at the attachment of the biceps tendon to the glenoid labrum. May be continuous with a sublabral foramen if present. Extends medially.
Sublabral foramen = separation of the labrum from underlying glenoid, at anterosuperior labrum, doesn’t extend posteriorly past the insertion of the long head of the biceps tendon.
What to look for on MRI?
Look for posterior tibial tendon tear, causing midfoot collapse (plantar subluxation of the talar head relative to the navicular). Commonly coexists with spring ligament failure.
Chronic injury, common in obese women and those with inflammatory arthropathies in 5th-6th decades.
What are the main ligaments of the ankle?
Identify the tendons.
Anterior group, from medial to lateral: 1. Tibialis anterior, 2. Extensor hallicus longus, 3. Extensor digitorum longus.
Lateral group: 5. Peroneus longus, 6. Peroneus brevis.
Medial group, from anterior to posterior: 10. Tibialis posterior, 9. Flexor digitorum longus, 8. Flexor hallucis longus.
Diagnosis?
Differential?
Intramuscular myxoma - low t1 with peritumoral fat rind, high T2, would have mild internal enhancement. A solitary benign soft-tissue tumor most common in women age 40-70.
Myxoid liposarcoma (look for fatty nodules, fatty septa) and myxoid chondrosarcoma can look very similar!
7M. Diagnosis?
Legg-Calvé-Perthes disease - an idiopathic avascular necrosis (AVN) of the growing femoral epiphysis seen in children.
What is Pellegrini-Stieda disease?
Ossification of the MCL near the margin of the medial femoral condyle, a result of healed past trauma to the MCL.
Diagnosis?
Cause?
Particle disease (aka aggressive granulomatosis).
An osteolytic histiocytic response of the bone to small polyethylene particles shed from the articular lining of orthopedic hardware. Look for abnormal liner wear, evident by superiorly malpositioned femoral head component in this case. May be asymptomatic until it is enough to cause loosening.
Diagnosis?
Imaging findings?
Psoriatic arthritis. Hands and feet most commonly involved. Rheumatoid factor negative, 60% HLA-B27 positive. Skin findings precede arthritis in 90%.
Periarticular marginal erosions and proliferation of bone (leads to “fuzzy” appearance). May see: pencil in cup deformity, sausage digit, “ivory phalynx-“
sclerotic distal phalanx of great toe, late- arthritis mutilans, asymmetrical sacroiliitis.
Diagnosis?
Cause?
Melorhestosis.
Thought to be a developmental error in intramembranous bone formation with overproduction of bone matrix in skeletal regions innervated by a single spinal sensory nerve. Usually presents in late adolescence or early adulthood, chronic, progressive course.
Diagnosis?
Cause?
Rugger jersey spine in secondary hyperparathyroidism.
Due to excess accumulations of osteoid related to osteoblastic activity resulting from abnormally high levels of PTH.
Diagnosis?
Cause?
Macrodystrophia lipomatosa.
Enlargement of a single digit, most commonly the 2nd or 3rd digits, hand more common than foot. Congenital but not hereditary. A fibrolipomatous hamartoma involves the nerve innervating the affected digit, see disproportionate overgrowth of fibroadipose tissue but get bony overgrowth as well. Growth ceases at puberty.
40M with a history of penetrating trauma to the finger. Diagnosis?
Differential?
Epidermal inclusion cyst. Secondary to penetrating trauma which allows the intraosseous deposition of epidermal cells that proliferate. See keratinized debris within the lesion.
Differential diagnosis is glomus tumor (typically causes extrinsic erosion along the terminal phalanx subjacent to the nail bed, extremely tender to palpation) and enchondroma (less common in the terminal phalagnes).
What is the difference between a lunate dislocation and a perilunate dislocation?
Which is shown below?
Lunate dislocation - the lunate is displaced and rotated volarly. The rest of the carpal bones are in a normal anatomic position in relation to the radius. Often a result of forceful dorsiflexion of the wrist.
Perilunate dislocation - the radiolunate articulation is preserved and the rest of the carpus is displaced dorsally. ~60% are associated with a trans-scaphoid fracture (trans-scaphoid-perilunate dislocation).
Lunate dislocation is shown on the front of the card. This is more severe. Perilunate dislocation shown below.
What is the classification of perilunate instability?
Stage I: scapholunate dissociation (rotatory subluxation of the scaphoid) due to disruption of scapholunate ligament. Exacerbated in clenched fist views.
Stage II: perilunate dislocation- the lunate remains normally aligned with the distal radius, and the remaining carpal bones are dislocated (almost always dorsally). The capitolunate joint is disrupted, and the lunate projects through the Space of Poirier. 60% are associated with scaphoid fractures.
Stage III: midcarpal dislocation- triquetrolunate interosseous ligament disruption or triquetral fracture. Neither the capitate or the lunate is aligned with the distal radius.
Stage IV: lunate dislocation- dorsal radiolunate ligament injury. Dislocation of the lunate in a palmar direction.
Diagnosis?
Common presentation?
Chondrosarcoma. Malignant cartilaginous tumors, most common in 4th-5th decades. Often lytic, moth eaten, with cortical destruction and calcified chondroid matrix (rings/arcs), soft tissue mass. MRI- low-intermediate T1, very high T2 (in non-calcified portions), heterogeneous enhancement.
Typically presents with progressive pain.
This is isointense to muscle on T2. Differential diagnosis? How to differentiate?
Giant cell tumor of the tendon sheath (aka pigmented villonodular tumor of the tendon sheath)- blooming artifact on GRE images. Slow-growing, painless.
Fibroma of the tendon sheath- benign overgrowth of tissue containing a large quantity of collagen. Slow-growing, painless. Men > women, 20-50, ~ 1/4 recur. No blooming.
Consider synovial sarcoma- calcifications, osseous invasion, bright on T2.
Diagnosis?
Key features?
Sarcoidosis.
Lacelike trabecular pattern involving multiple phalanges of the hands/feet secondary to noncaseating granulomas. Mild soft tissue swelling common. Joint spaces preserved. Metacarpals usually not involved. Can cause vertebral body sclerosis, mimicking mets.
Diagnosis?
Cause?
Presentation?
Cyclops lesion (aka localized anterior athrofibrosis). Intermediate to low signal mass on all sequences, located anteriorly in the intracondylar notch.
Dense fibroconnective vascular tissue, most common after ACL repair.
Difficulty with extension of the knee due to mass effect.
21 year old male. Diagnosis? MRI findings?
Differential?
Hemophilic arthropathy.
On MRI, uniformly thickened synovium with low signal intensity related to hemosiderin deposits. Most common joints involved are: knee, ankle, elbow, shoulder.
VS:
PVNS: nodular/lobular synovial thickening with low signal intensity.
JRA: synovitis with invreased T2 signal intensity. Affects hands/feet and spine, hemophilic arthropathy usually does not.
Diagnosis?
Cause?
Associations?
Madelung deformity.
Abnormal configuration of the distal radius caused by underdevelopment of the ulnar margins. Dorsal and radial bowing of the radius. Often bilateral. Relative overgrowth of the ulna with ulnocarpal impaction.
Multiple causes. Can be primary or secondary, including bone dysplasias (dyscondrosteosis), Turner syndrome, osteochondromatosis, achondroplasia, trauma, and infection.
Diagnosis?
Cause?
Prepatellar bursitis.
Inflammation of the prepatellar bursa in response to minor repetitive injury. Hemorrhage may coexist.
Consider inflammatory bursitis when associated findings are present- soft tissue calcs in gout, arthropathic changes in RA. If appropriate clinical scenario, consider septic bursitis.
Diagnosis?
MRI findings?
Freiberg’s disease. AVN of the metatarsal heads, most commonly the 2nd. Develop secondary OA. Athletic adolescent girls or older women who wear high-heels.
On MRI, low T1 and high T2 signal in the affected metatarsal head.
Further workup?
Avulsion fracture of the lesser trochanter.
In a young adult, this is a rare traumatic avulsion fracture from the iliopsoas tendon.
In an adult, especially without a history of trauma, pathologic fracture is likely. Cross sectional imaging must be obtained to exclude underlying malignancy.
Diagnosis?
Other features?
Nail-patella syndrome (aka Fong disease, aka osteo-onycho-dysplasia). Autosomal dominant.
See: nail dysplasia, hypoplastic or absent patellae, dislocation of the radial heads, iliac horns (asymptomatic, located at site of gluteus medius attachment), and renal dysplasia.
Diagnosis?
Criteria for diagnosis?
Complication?
Developmental hip dysplasia.
Deficient acetabular coverage of the femoral head with a center-edge angle of <25 degrees (see below).
Predisposed to _anterosuperior labral tear_s due to increased weight-bearing role of the labrum.
Diagnosis?
Inheritance?
Diagnosis of malignant transformation?
Multiple hereditary exostoses (aka osteochondromatosis).
Autosomal dominant.
MRI- look for cartilage cap thickness > 1.5 cm in size. Malignant degeneration in 3-5%, more common in centrally located osteochondromas (pelvis, hips, shoulders).
Diagnosis?
Criteria?
No trauma… likely association?
Atlantoaxial subluxation.
Widening of the predental space to > 3 mm. Note that in children the normal measurement is up to 5 mm!
Most common cause is RA. Other causes include truama, CPPD arthropathy, and Downs syndrome.
No rotator cuff tear. Diagnosis?
Cause?
Quadrilateral space syndrome. Focal denervation edema and atrophy involving the teres minor muscle +/- portions of the deltoid.
Caused by compression of the axillary nerve and posterior circumflex humeral artery in the quadrilateral space (bound by long head of triceps, teres minor and major, and the humerus, see below). Shoulder pain and paresthesias, point tenderness in quadrilateral space.
Diagnosis?
Where else to look?
Ganglion in the suprascapular notch.
Look for edema and/or atrophy of the supraspinatus and infraspinatus muscles due to compression of the suprascapular nerve. (note the suprascapular artery travels above the transverse scapular ligament at the top of the notch)
Diagnosis?
Cause?
Blount disease (tibia vara).
A result of abnormal stress on the posteromedial proximal tibial physis, which suppresses growth. Growth at the epiphysis becomes asymmetric, leading to varus angulation. Typically unilateral or asymmetric. Predisposing factors- early walking, obesity.
40M. Diagnosis?
Imaging findings?
Pleomorhpic undifferentiated sarcoma (aka Malignant fibrous histiocytoma, formerly fibrosarcoma).
The most common soft tissue sarcoma in adults. Painless, enlarging soft-tissue mass. Poor prognosis. Predilection for the retroperitoneum and extremities.
MRI: heterogeneous, intermediate on T1, high signal on T2. Marked enhancement. Well-defined margin 2/2 pseudocapsule. Surrounding edema. Can see mineralization, internal hemorrhage, necrosis, extrinsic erosion of adjacent bones.
Diagnosis?
Types?
Popliteal artery entrapment. Often asymptomatic. Symptoms usually in patients under 30 with good muscle development, present with calf claudication esp with plantar flexion. Need surgery.
Type I: popliteal artery has aberrant medial course around medial head gastrocnemius (this case).
Type II: artery is not displaced but MHG inserts more lateral than usual so the artery passes medial and beneath the muscle.
Type III: accessory slip of MHG slings around the artery.
Type IV: artery lies deep in popliteal fossa entrapped by popliteus or fibrous band.
Type V: both popliteal artery and vein are entrapped.
Diagnosis?
Hallux rigidus. OA of the 1st MTP joint.
9 months after fracture. Diagnosis?
Cause?
Hypertrophic non-union.
Related to abnormal immobilization across a fracture site. A pseudarthrosis is seen across the fracture bed with surrounding bony hypertrophy.
Diagnosis?
Imaging findings?
Giant cell tumor.
Expansile, mixed cystic and solid mass. Eccentrically located in the epiphysis of any bone. Very vascular, so significant enhancement on CT or MRI. Intermediate signal intensity on T1 and T2 weighted MR. Can have fluid-fluid levels.
2nd most common tumor in the sacrum (after chordoma), often seen in 2nd-4th decades. Chordoma often has internal calcifications and a large pre-sacral soft tissue component.
Diagnosis?
Symptoms?
Peroneal nerve sheath ganglion (common fibular nerve ganglion).
Foot drop and paresthesias over the dorsum of the foot.
Where to look for the fracture?
What is this called?
Spiral fracture of the proximal fibula.
Maisonneuve fracture. An eversion injury. See widening of the medial clear space of ankle > 5 mm (may only be on standing views), spiral fracture of the proximal fibula. Often associated with syndesmotic dysruption or malleolar fracture, and deltoid ligament tear.
