MSK Flashcards
**Dorsal intercalated segmental instability **
Happens with SL ligament injury
WIDENING (>80) of the Scapholunate angle
The Lunate tilts DORSALLY and the scaphoid tilts volar
Volar intercalated segmental instability
Rare, happens with lunotriquetral lug injury.
Lunate and Scaphoid tilt Volar
ACUTE scapholunate angle <30
Bennets
Fracture base of the first metacarpal
Pull of the abductor pollicus longus (APL tendon causes dorsolateral dislocation
Nb a comminuted # base of 1st metacarpal = ROLANDO
Gamekeepers
Avulsion fracture of the base of the proximal first phalanx
Ulnar collateral ligament disruption
STENER lesion = when adductor tendon gets caught in the torn edges of the UCL = Surgery
Segond fracture
Lateral tibial plateau
Associated with ACL tear (75%) and internal rotation
MR SL = Medial Reverse Lateral Segond
Reverse Segond fracture
Medial tibial plateau
Associated with PCL tear with external rotation. Associated with medial meniscus injury.
MR SL = Medial Reverse Lateral Segond
Arcuate sign
Avulsion of the proximal fibula
Associated with PCL tear
Tillaux fracture
Salter-Harris 3 = through the anterolateral distal tibial epiphysis
Triplane fracture
Salter-harris 4 =Vertical component through the epiphysis , horizontal component through the physis , oblique through metaphysis
What is bohlers line?
line drawn between the anterior and posterior borders of the calcaneus
< 20 ? fracture
ENCHONDROMA
Commonest location Hands/feet
Long bones: proximal humerus > distal and proximal femur > proximal tibia
Intramedullary and metaphysis
multiple enchondroma
Maffuci - haemangioma
Olliers - multiple enchondroma only
DDx
-Brown tumor (hyperparathyroidism),
-sarcoid - lace like bone lesion phalanges
-intraosseous ganglion
-metastatic disease.
MRI
T1: low to intermediate signal
Fluid-sensitive sequences: lobulated high signal typical of cartilage lesions
Enhancement: peripheral and septal, accentuating lobules
Chondrosarcoma
May be cecondary to
- Osteochondromas
- enchondromas
Chondrosarcomas occur in the pelvis, femur, humerus.
Skull base, TMJ
DDX
-Most well differentiated, low grade = ‘low grade chondroid lesion’ , cant differentate from enchondroma
-Bone infarct
MRI
Lobular growth
High 2 signal/STIR, low T1
ring and arcs/chondroid matrix islands on CT
Soft tissue extension
**endosteal scalloping. **
if no mineralized matrix/rings and arcs = aggressive/high grade
How to tell chondrosarcoma from enchondroma ?
* Pathological fracture occurring with minimal trauma
* Multilayered or spiculate periosteal reaction
* Permeative or moth-eaten osteolysis
* Cortical destruction
* A soft tissue mass
Endosteal scalloping more than 2/3 cortex
Osteochondroma
points away from the joint
Pedunculated lesion arising from surface of bone with continuity of normal cortex and marrow
Metaphysis/metaphyseal equivalents (rarely diaphysis)
Multiple =
Diaphyseal aclasia/Multiple Hereditary Exostoses - Metaphysis region of tubular bones of extremities
Cap > 1.5cm ??? chondrosarcomatous transformation
ng. avian spur points towards the joint
osteosarcoma
Femur (40%) and proximal tibia commonest sites (15%)
**Aggressive periosteal reaction **
- Sunburst
- Codman triangle
- Lamellated (onion skin)
**High grade = Met to the lung
**
Reverse zoning phenomenon - dense mature matrix in the centre, less peripherally
DDx
ewings Sarcoma
telangiectatic oestosarcoma
Distal Femur
Haemorrhagic and necrotic components
Fluid-fluid levels
Thus, heterogenous on T1 and T2
*Purely lytic but with aggressive features, less likely osteoid matrix
Solid components enhance
DDx
ABC
—Expansile lytic lesion arising in metaphysis
—No tumour nodularity and enhancement
- Thin peripheral and septal enhancement
GCT
—Mildly expansile metaphyseal lesion with extension to joint line
—Can be very aggressive and have soft tissue extension
Parosteal OS
Big +++
**Posterior distal femur (metaphysis) **
Osteoid ++
Marrow extensions (50%)
Early adult and middle age
*string sign Lucnet cleft between bone and mass. This is not present in Periosteal sarcoma
Low grade
Periosteal OS
Diaphyseal
Likes **medial distal femur **
Large enhancing soft tissue component
Less osteoid comapared to parosteal
Usually, no marrow extension
Nb Intermediate grade ie worse prognosis than parosteal but better than conventional
chondromyxoid fibroma
look for internal septations/pseudotrebulations
Eccentric
Sclerotic margins
DDx GCT
- very similar, similar location (eccentric, originates in metaphysis, extends to subarticular region)
-rarely has sclerotic margin
DDx ABC
-Fluid/fluid levels MRI and thin walled
DDx Non-ossifying fibroma
-Cortex based rather than eccentric intramedullary
Adamantinoma
Low-grade, malignant lesion most frequently arising in tibial** cortex**
Mutlifocal
slcerotic and lytic compoents
*Cortically based lesion in anterior tibia
synovial sarcoma
Triple sign
Heterogeneous signal (combination of low, intermediate, and high) T2 signal from:
Solid mass
haemorrhage + necrosis
calcification (1/3).
Bowl of grapes sign = multiloculated appearance of mass with internal septa
Heterogenous enhancement of the solid components.
little to no perilesional oedema
Classic history -
paediatric patient with a multi-cystic appearing mass with well-defined margins around the knee joint
NOT in joint ie DOESNT arise from the synovium. Close to joint
well differentiated liposarcoma
*>75% fat content
*thickened septa
*small soft tissue nodularity
commonly located in the retroperitoneum
if develops a clear cut separate nodular/soft tissue dominant focus > 1 cm = de-differentiated
if < 20
= Myxoid liposarcoma often shows a classic myxoid background (T2/STIR-bright) with some nodular soft tissue
and adipose tissue components. Don’t confuse for cyst!!!
Osteoid osteoma
Cortically based
peripheral sclerosis and central with nidus
**nidus > 2cm = osteoblastoma **
= Posterior elements
Nb** Osteoblastoma can have have soft tissue expansion/involvement**
Double density bone scan
DDx
-stress fracture
- intracortical abscess
Melorheostosis
Irregular continous cortical hyperostosis or linear intraosseous sclerosis
‘Dripping candle wax’
Occurs in sclerotomal distribution - thickening underlying skin
Can cross joints
Fibrous dysplasia
long, expansile lesion with mixed density ranging from lytic to *ground glass .
‘long lesion in a long bone’.
Typically medullary, with expansion,
Monostotic is most common FD
‘Shepereds crook deformity’ if proximal femur
Polyostotic fibrous dysplasia
2 conditions assocated with polyostotic FD
1. McCune- Albright - Cafe-au-lait, precocious puberty
2.Mazarbrauds
+ look for intramuscular Myxomas in adults
Monostotic is most common FD
ABC
- Eccentric in location
- More pronounced Fluid-fluid levels
- More expansile
- Can be 2o = giant cell tumor, chondroblastoma, and osteoblastoma
SBC
- Centered in medulla
- Classic HUMERUS and long bones
- Fallen fragment sign
- Present with pathological fracture
Nb in small bones, phalanx, metacarapls - appear identical
chondroblastoma
Epiphyseal regions long bone
(or epiphyseal equivalent - Patella, calcaneus, trochanters, tuberosities, tarsal and carpal bones)
Males < 20
*Lytic lesion
-eccentric **
- arising epiphysis or apophysis.
skeletally immature patient - +/- internal Ca2/chondroid matrix+
-*Extensive perilesional edema and enhancement in marrow MRI
**
Not a child or adolescent adult clear cell chrondrosarcoma
NOF
children/adolescences
Distal tibia and femur in a
metadiaphyseal,
*Cortical
well defined,** sclerotic margins** , can also **have internal septations **
If <2-3 cm in size this may be termed a fibrous cortical
defect.
NOF may also heal and become completely sclerotic
DDX
ABC - MRI ‘fluid - fluid’ levels.
GCT
Doesnt typical extent to the epiphysis (like GCT)
GCT non -sclerotic margin
Growth plates closed
chondromyxoid fibroma
- both sclerotic margins and internal septations
-eccentric intramedullary
Mnemonic is MELT.
Metastasis/Myeloma
Eosinophilic granuloma
Lymphoma
Trauma/Tuberculosis.
GCT
-Physis closed.
-Non-sclerotic margins
-originated in epiphysis and extends to metaphysis.
-Abuts articular surface
-Eccentric
-‘Soap bubble’
If in spine = sacrum
Fluid-fluid level on MRI
Can be locally aggresive, rarely metastases
DDx
+Chondroblastoma
- Skeletal immature usually
- originates in epiphysis rather than metaphysis
- chondroid matrx
- Sclerotic margin common + periosteal reaction
-Extensive regional edema
+Chondrosarcoma
+ABC
Rickets = Child: growth plates (physes) wide, frayed, and cupped
Osteomalacia = Adult: Looser zones (late finding), smudgy and ill defined trabeculae
Osteochondrosis?
Kohlers = Navicular
Frieberg = 2nd Metatarsal
Severs = Calcanael apophysis
Blount = proximal medial tibial epiphysis = ‘Bow leg’
Perthes = Femoral head (4-8)
Scheuermann disease = Vertebral apophyses. multiple wedged vertebrae and thoracic kyphosis
Preiser = scaphoid
Kienbock = Lunate (20-40, associated with negative ulnar variance)
Panners = Capitellum (5-10, throwers)
Bilateral and symmetrical
- AS
- IBD
Bilateral and asymmetrical
- Gout
- Reiters
- Psoriatic
osteitis condensans - female, bilateral, symmetric, triangle-shaped sclerosis of ilium at sacroiliac joint
Unilateral
- infection
- rarely SAPHO
causes of posterior vertebral scalloping?
SATAN
Syringomyelia/Dural ectasia
Acromegaly
Tumours - (ependymoma, lipoma , dermoid, neurofibroma)
Achondroplasia
NF - 1
also
Connective tissue disease - marfans, ehler danlos
Mucopolysacchardoses - hurlers, murquio - VERTEBAL BEAKING
Downs
Atlanta-axial subluxation
Flaring of iliac wings ‘mickey mouse’/elepahant ears’pelvis
DDH
Eleven ribs
NF-1
Commonest skeletal/Spinal abnormality
–Scoliosis (from plexiform neurofibromas)
–Posterior vertebral scalloping
–Dural ectasia
– Lateral thoracic mengiocele
– Foraminal narrowing, Hypoplastic pedicles and posterior elements (remodelling from mengiocele)
– Intramedullary or extramedullary intradural NF’s
Haemophilia arthopathy
Dense hemarthrosis
Epiphyseal overgrowth
Erosions & joint space narrowing, significant OA in young adolescent
**Hypertrophied synovium due to haemosiderin (GRE blooming ++) and low on all signals
Widened intercondylar notch**
Rare pseduotumour =
Large expansile or lytic bubbly lesion with mass effect on adjacent tissues/scalloping on bone
nail-patella syndrome
Bilateral iliac ‘horns’
absent/hypoplastic patella’s
Broad horizontal acetabulum
Pagets
Osseous expansion
Thickening of cortex
Coarse trabecular pattern
Skull - osteoporosis circumpripta (lytic phase)
Skull - sclerotic phase - Enlargement of skull: widening of diploic space, involvement of inner and outer tables
‘tom o shanter’ sign
Brown = well defined cortical lesion with no periosteal reaction
Also in lytic phase - blade of grass or flame shaped lucent bone lesion
osteopetrosis
Diffusely dense bones (marble bone)
Pigmented villonodular synovitis (PVNS)
Joint effusion
Low signal T1/T2
**haemorrhagic proliferation of the synovium in a frond-like villonodular fashion **gives rise to the classic low signal ‘feathery’ sea-anenome-like finding
Blooming artefact MRI because of haemosiderin
scalloping of the pre-patellar fat pad and erosions of adjacent bone
DDx
Haemophilia - as blood products in joint too
widening of the intercondylar notch due to pannus formation
Joint degeneration
Lipoma Arborescens
kids
chronic inflammation of the synovium leading to extensive fatty infiltration of the synovium
high on T1 and T2 but suppress on fat-saturated sequences.
**Post-contrast the synovium itself will enhance. **
Treatment is by synovectomy.
SAPHO
Synovitis: anterior chest wall, unilateral sacroiliitis
Acne: hydradenitis suppurativa, acne conglobata
Pustulosis: palmoplantar pustulosis (50%)
Hyperostosis: enthesopathy, sclerosis
Osteitis: inflammatory changes, pain
Sternoclavicular hyperostosis
Nuclear medicine bone scan, bilateral uptake in the sternoclavicular joints and manubrium is called a** ‘bull’s head’ sign**
Unilateral sacroiliitis may also occur
Features of DISH?
DISH
flowing ossification of at least 4 vertebral bodies with normal disk spaces and sacroiliac joints
Adherent to anterior and right-lateral vertebral bodies in thoracic spine- left lateral vertebrae can be spared ? aortic pulsation
ossification of patellar ligament
spur formation in the appendicular skeleton (olecranon, calcaneum, patellar ligament) frequently present
enthesopathy of the iliac crest, ischial tuberosities, and greater trochanters
whiskering of iliac crest
DDX
ankylosing spondylitis (AS)
Osteoporosis is prominent differentiating feature following ankylosis
AS syndesmophytes: thin, vertical, form in anulus
Severe late AS may extend to ossify ALL
gauchers
Erlenmeyer flask - Metaphyseal flaring
H shaped vertebrae
Osteonecrosis/AVN- femoral and humeral heads
-serpiginous sclerotic areas or a bone-within-bone appearance
Hepatosplenomegaly is common and co-existent with thrombocytopaenia and anaemia secondary to bone marrow failure
diffuse marrow replacement with low signal T1
100 times more common in Ashkenazi Jews
DDX sickle cell
Similar H-shaped vertebrae
ON similar; more patchy sclerosis
No Erlenmeyer flask deformity
Spleen infarcts are differentiating factor - small calcified spleen
Rheumatoid arthritis
Synovitis/soft tissue swelling
Periarticular oestopenia
**Marginal erosions **
Uniform joint space narrowing
Deformity late stage
**No bone proliferation **
Proximal distribution in hands
-MCP, and PIPJ- typically first
- Carpals, Radiocarpal,
Hip
-concentric loss of joint space, osteoarthritis (OA) = superior loss of joint space
-acetabular protrusion
Shoudler girdle
-erosion of the distal clavicle
-marginal erosions of the humeral head: the superolateral aspect
-“high-riding shoulder” = subacromial-subdeltoid bursitis
- high incidence of rotator cuff tear
Spine
-erosion of the dens
- atlantoaxial subluxation
- atlantoaxial impaction (cranial settling): cephalad migration of C2
- erosion and fusion of uncovertebral (apophyseal joints) and facet joints
DDx
Amyloid arthropathy can be similar distribution and pattern of erosions.
However amyloid classically preserves joint space, unusual for periarticular osteopenia and LARGE and excessive subchondral cyst formation
Psoriatic arthritis
**Distal - Favours DIPJ and IPJ>MCP **
**Mixed - Erosive changes and bone proliferation **
Sausage digit (dactylitis)
Pencil in cup
No osteoporosis - NORMAL bone density
Outside hands-
- Ivory phalanx
-Altanoaxial subluxation
-Spondyloarthropathy -
Bulky paravertebral ossification, asymmetric with skips
Sacroiliitis: bilateral but asymmetric
DDx
Reiters
- Same appearance of bilateral but asymmetric sacroiliitis
- Same bulky paravertebral ossification
Thin vertical syndesmophytes with concomitant bilateral sacroiliitis
‘Bamboo spine’
Joints widen first before narrows
Enthesopathy - calcified tendon insertion sites
‘Dagger sign’ - spinous process fusion
Early features are far more subtle and require a higher index of suspicion, which include,
MRI-
-Enthesopathy - high signal on MRI at tendon insertion sites
-Romanus lesions/’Shiny corners’ - triangular shaped oedema at the corners of vertebral bodies
-Andersson lesions - bony oedema in the vertebral bodies adjacent to the disks.
-Oedema in the sacroiliac joints.
Sequences = T1 fat sat and STIR, coronal SIJs and sagittal spine
T1 fat sat - useful for visualisation of bony erosions and new bone formation
T1 fat sat post contrast - useful for detecting bone marrow abnormalities (but so is STIR, so contrast is not an absolute requirement for imaging ankylosing spondylitis).
STIR - useful for detecting bone marrow abnormalities in the SIJs and spine
T2 fat sat - useful for detecting oedema
Extra-articular
-Upper lobe predominant ILD, fibrobullous disease
-aortic root dilatation, aortic regurgitation, pericarditis
DDx
- IBD associated arthritis -
- Axial - Identical appearance of sacroiliitis and spondylitis to AS
- IBD enthesopathy often calcaenus
CPPD
Overlaps with OA but atypical Joints
-Patellofemoral and not medial/lateral compartment
Wrist: radiocarpal joint
Hand: MCP joints, particularly 2nd and 3rd
Chondrocalcinosis (not invariably present)
Hook osteophytes of metacarpal heads
Subchondral cysts common, may be large
Scapholunate advanced collapse wrist SLAC*- Degenerate SL ligament
Disorders assoicated with CPPD - 4 Hs
- hypothyroidism
- haemochromatosis
- hyperparathyroidism
- hypomagneseia
DDx
Haemochromatosis
-Younger males, similar distribution to CPPD
- Both ‘hooked’ oestophytes - of the radial aspect of the 2nd and 3rd MCP
Gout
Typically men >40
Spares joint space (until late)
Juxta-articular erosions (punched out) with Overhanging edges
erosions with sclerotic margins
Soft tissue tophi
1st MTP joint = most frequent site
Hyperparathyroidism
**‘Subperiosteal bone resorption’ radial 2nd and 3rd fingers **
**Terminal tuft erosions/resportion = Acro osteolysis
**
Brown tumour:
-expansile, nonaggressive lytic lesion, Non sclerotic margins
-no cortex destruction, periosteal reaction, soft tissue mass or matrix
Superior and inferior rib notching
Rugger jersey spine/osteosclerosis is associated with secondary hyperparathyroidism
chondrocalcinosis
salt and pepper skull
-due to generalized bone resorption with more focal areas of lucency ± patchy sclerosis
1° hyperparathyroidism (HPTH): parathyroid adenoma (75-85%)
Tc-99m sestamibi scan and US for diagnosis
2° HPTH: chronic kidney disease most common
Nb Renal osetodystrophy is 2° HPTH and oestomalacia
JIA?
Before 16
Premature closure of the physis
large effusions++
erosions
Cartilage destruction & joint space narrowing (JSN)
End-stage ankylosis
Carpus most frequent site of fusion
Widened intercondylar notch
DDx
Haemophilia
TB
Psoriatic arthropathy
DDx for Ivory vertebrae
see picture
DDx Atlanto-axial subluxation?
see picture
Osteoporotic vs metastatic vertebral body fracture
see picture
TB vs Staph discitis?
see picture
Dashboard injury?
see picture
Hyperextension injury to the knee?
see picture
anterior aspect of the tibial plateau and femoral condyles
Pivot shift injury?
see pic
Clip injury
see picture
Patellar dislocation injury pattern?
see pic
DDx for Erlenmeyer flask deformity?
see picture
Sclerosing Dysplasia
Osteopoikilosis
Metaphyseal or epiphyseal foci of dense lamellar bone that resemble bone islands
**Pyknodysostosis **
Severe sclerosis involving entire skeleton but medullary space is preserved
- short stature
- small mandibular size and beaking of the nose
-Wormian bones
-acro-osteolysis with sclerosis (-acro-osteolysis with sclerosis)
osteopathia striata
Striated intramedullary densities, often metaphyseal
‘stalks of celery’
Myositis ossifcans calcifcation pattern?
It begins as amorphous calcification and then develops a sharper cortical margin after approximately 2 months.
Periosteal reaction may or may not be present but crucially there is no erosion of the underlying cortex, a fact which discriminates it from malignant fibrous histiocytoma.
string sign
Unlike a parosteal osteosarcoma, this plane will extend along the whole length of the mass completely separating it from the bone.
Parosteal osteosarcoma may have scalloping
problem with the development of the ulnar side of the distal end of the radius. The distal radioulnar joint subluxes and the ulna displaces dorsally. proximal carpus is V-shaped
Madelung deformity
growth failure of the distal radius, by comparison the ulna appears lengthened (Positive ulnar variance).
appearance is of a V-shape to the radioulnarcarpal joint with angles of <120 considered characteristic.
Mnemonic = DIGIT
D = Dysplastic - Ollier disease, osteochondromatosis, achondroplasia, mucopolysaccharidoses, diaphyseal aclasis
I = Idiopathic
G = Genetic - Autosomal dominant.
50% of patients have bilateral deformities.
Most common association is Turner syndrome
I = Infection
T = Post-Traumatic
Features of multiple myeloma
1) Plasmacytoma - solitary lytic lesion - spine, pelvis , skull
2) Myelomatosis - Diffuse skeletal involvement - oestolytic lesions with discrete margins
3) Diffuse skeleteal oestopenia - no lytic , predominantly in the spine (this type can have multiple compression fractures)
4) Scelorsng myeloma - with sclerotic bony lesions , associated with POEMS syndrome
Myeloma has poor uptake on bone isotope scans
Features of hypertrophic osteoarthopathy
Periosteal reaction, usually along shafts of tubular bones in extremities
Generally symmetrical
Location
Tibia, fibula, radius, ulna are most frequent
Less common in phalanges
3-phase bone scan
Typically linear symmetric ↑ uptake along margins of long bones: parallel track sign, tram line sign, or double stripe sign
types of osteogensis imperfecta?
Almost alwas type 1 or 4
Type 1 most common
- Blue sclera
- normal stature
- Hearing impairment
Type 4
-small stature
-usually normal hearing
Calcaneonavicular vs talocalcaneal coalitions
see picture
