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86 Cards in this Set

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Giant Cell Tumor
Imaging Findings

* Lytic epiphyseal lesion extending to subchondral bone without surrounding sclerosis
* Occurs typically in skeletally mature patients

Top Differential Diagnoses

* Aneurysmal Bone Cyst (ABC)
* Intraosseous Ganglion
* Chondroblastoma
* Osteosarcoma
* Giant Cell Reparative Granuloma

Pathology

* 5% of all primary bone tumors
* 6th most common primary bone tumor

Clinical Issues

* Pain and swelling at affected area, relieved by decreased activity
* Pathologic fracture in 30%
* Locally aggressive: 12-50% recurrence rate
* Can undergo sarcomatous transformation, spontaneously or in response to radiation therapy
* Curettage with cryotherapy, phenol, liquid nitrogen to reduce recurrence rate
* Surgical resection with filling of resection cavity with bone graft or methylmethacrylate
* Radiation only for cases of unresectable tumor (risk of sarcomatous degeneration)
* Resection of pulmonary implants
Chondroblastoma
Imaging Findings

* Best diagnostic clue: Well-defined lytic lesion centered in epiphyses of skeletally immature patients
* Radiographs diagnostic
* MRI might suggest aggressive/malignant lesion due to extensive surrounding edema

Top Differential Diagnoses

* Clear-Cell Chondrosarcoma
* Giant Cell Tumor
* Langerhans Cell Histiocytosis (LCH)
* Intraosseous Ganglion
* Aneurysmal Bone Cyst (ABC)
* Avascular Necrosis of the Femoral Head
* Osteomyelitis (Abscess)
* Pseudotumor of the Greater Humeral Tuberosity

Pathology

* Less than 1% of all primary bone tumors
* 9% of benign bone tumors

Clinical Issues

* Mild joint pain, tenderness, swelling
* Benign tumor
* May become locally aggressive
* Curettage and packing with bone graft, polymethylmethacrylate

Diagnostic Checklist

* Location (epiphyses/apophyses), age (immature skeleton)
Chondroblastoma
Imaging Findings

* Best diagnostic clue: Well-defined lytic lesion centered in epiphyses of skeletally immature patients
* Radiographs diagnostic
* MRI might suggest aggressive/malignant lesion due to extensive surrounding edema

Top Differential Diagnoses

* Clear-Cell Chondrosarcoma
* Giant Cell Tumor
* Langerhans Cell Histiocytosis (LCH)
* Intraosseous Ganglion
* Aneurysmal Bone Cyst (ABC)
* Avascular Necrosis of the Femoral Head
* Osteomyelitis (Abscess)
* Pseudotumor of the Greater Humeral Tuberosity

Pathology

* Less than 1% of all primary bone tumors
* 9% of benign bone tumors

Clinical Issues

* Mild joint pain, tenderness, swelling
* Benign tumor
* May become locally aggressive
* Curettage and packing with bone graft, polymethylmethacrylate

Diagnostic Checklist

* Location (epiphyses/apophyses), age (immature skeleton)
Langerhans Cell Histiocytosis
Terminology

* Synonyms: Langerhans cell histiocytosis (LCH), Langerhans cell granulomatosis, eosinophilic granuloma (EG), histiocytosis X
* Abnormal histiocyte proliferation producing granulomatous skeletal lesions

Imaging Findings

* Best diagnostic clue: Child presenting with vertebra plana sparing disc space
* Calvarium > mandible > long bones > ribs > pelvis > vertebrae
* Thoracic (54%) > lumbar (35%) > cervical (11%)
* Children > adults
* Morphology: Destructive lytic lesion +/- pathologic fracture, soft tissue mass, spinal canal extension

Top Differential Diagnoses

* Ewing sarcoma
* Metastases
* Neuroblastoma
* Hemopoietic malignancies
* Osteomyelitis
* Giant cell tumor

Pathology

* Expanding erosive histiocyte accumulation within medullary cavity

Diagnostic Checklist

* Vertebra plana much more common in children than adults
* Unexplained vertebral compression fractures in children or adolescents merit evaluation to exclude LCH or leukemia
common



Septic Joint
Click to close this panel

less common



Psoriatic Arthritis (PSA), Early

Ankylosing Spondylitis (AS), Early

Chronic Reactive Arthritis (CRA), Early

Osteoarthritis (OA) (Mimic)
Click to close this panel

rare



Rheumatoid Arthritis (RA)

Gout
Hint: True unilateral sacroiliitis must be considered septic joint until proven otherwise
o Radiographic signs may be subtle
o Clinical signs may be misleading (buttock, groin, hip pain)

Hint: Consider diagnosis of septic SI joint in at-risk patients
o HIV-AIDS
o Diabetic patients
Sacroiliitis, Bilateral Asymmetric

common



Psoriatic Arthritis (PSA)

Osteoarthritis (OA) (Mimic)
Click to close this panel

less common



Chronic Reactive Arthritis (CRA)

Ankylosing Spondylitis (AS)

Inflammatory Bowel Disease (IBD)

Renal Osteodystrophy (Renal OD) (Mimic)
Click to close this panel

rare



Juvenile Idiopathic Arthritis (JIA)

Gout

Rheumatoid Arthritis (RA)
Bilateral asymmetric sacroiliac (SI) disease most frequently is seen in PSA & CRA

Other spondyloarthropathies that are generally bilaterally asymmetric may be asymmetric at some point in the process
o Hint: AS is much more prevalent than either psoriatic or chronic reactive spondyloarthritis, so should be strongly considered with this appearance
Sacroiliitis, Bilateral Symmetric

common



Ankylosing Spondylitis (AS)

Osteoarthritis (Mimic) (OA)

DISH (Mimic)

Osteitis Condensans Ilii (Mimic)
Click to close this panel

less common



Inflammatory Bowel Disease Arthritis (IBD)

Psoriatic Arthritis, Late (PSA)

Renal Osteodystrophy (Mimic) (Renal OD)
Click to close this panel

rare



Chronic Reactive Arthritis, Late (CRA)

Rheumatoid Arthritis (RA)
Sacroiliac (SI) joint inflammatory disease is most frequently seen in spondyloarthropathies

Two spondyloarthropathies are particularly noted for bilateral and symmetric involvement
o Hint: Bilateral symmetric sacroiliitis most frequently is due to ankylosing spondylitis, inflammatory bowel disease spondylitis
o Hint: Remember that spondyloarthropathies that are usually bilaterally asymmetric (PSA, CRA) may develop bilaterally symmetric disease at some point

Purely productive diseases of the SI joints may mimic the sclerosis of sacroiliitis
o OA, DISH, osteitis condensans ilii
o Sclerosis is predominantly on iliac side
o No associated erosive change
o Hint: Watch for location of sclerosis of SI joints to differentiate these mimics from true spondyloarthropathies & from one another
Rickets - pathophysiology, DDx
Terminology

* Nutritional rickets: Simple vitamin D deficiency due to lack of vitamin D in diet or inadequate exposure to sunlight is most common cause; calcium deficiency a cause in Turkey and in both tropical and subtropical Africa (rare elsewhere)

Imaging Findings

* Best diagnostic clue: Widened long-bone physes with cupped, splayed, and frayed metaphyses
* Healing: Increased density in zone of provisional calcification seen after treatment in 2-3 weeks with nutritional rickets and 2-3 months with renal rickets

Top Differential Diagnoses

* Leukemia
* Congenital syphilis
* Gymnast wrist

Pathology

* Normal bone development depends upon ready availability of calcium, phosphorus, and vitamin D
* Rickets: Calcification of cartilage and osteoid does not occur → widening of the zone of provisional calcification, which is perceived as physeal widening on radiographs
* Rickets: Metaphyseal widening and cupping caused by stress at sites of ligament attachments, splaying of cartilage cells peripherally, and microfracturing of primary spongiosa by protrusion of physeal cartilage

Clinical Issues

* Most cases of rickets respond to vitamin D therapy and, if necessary, calcium supplementation
Flask metaphysis - DDx
TOPDOG

thalassemia
oseopetrosis
pyle's disease (metaphyseal dysplasia)
diaphyseal aclasia
ollier's disease
gaucher's disease
Jefferson C1 Fracture
Terminology

* Atlas burst fracture
* Compression fracture of C1 arch

Imaging Findings

* Best diagnostic clue: Lateral displacement of both articular masses of C1 from those of C2 on open mouth radiograph
* Subluxation if unstable
* Axial CT defines components of fracture to best advantage
* May demonstrate various patterns of arch disruption
* Avulsion fragment off inner pillar at insertion of transverse ligament indicates instability
* Any lateral spread of C1 pillars on open mouth X-ray view requires CT
* Evaluate entire cervical spine as well as upper thoracic spine
* Associated fractures occur in 24-48% of cases

Top Differential Diagnoses

* Congenital Variants, Clefts, Malformations of Atlas
* Rotational Malalignment of Atlas, Axis Pillars
* Pseudospread of Atlas in Children

Diagnostic Checklist

* Routine CT of cervical spine in trauma victims with severe neck pain
* Evaluate lower levels for additional fractures
* 1-2 mm offset of C1 lateral masses vs. C2 on open mouth view in infants may be normal variant
Odontoid C2 Fracture
Terminology

* Traumatic bony disruption of odontoid process

Imaging Findings

* Lateral radiograph: Anterior or posterior displacement of C1 arch vs. C2, and prevertebral soft tissue swelling
* Classic imaging appearance
* Open mouth frontal radiograph depicts transverse or oblique defect through dens
* May be difficult to depict in elderly with osteoporosis
* Axial (source) images may miss or underestimate fracture if its plane parallels slice orientation

Top Differential Diagnoses

* Congenital Nonunion of Odontoid Tip (Os Odontoideum)
* Congenital Variation: 3rd Occipital Condyle
* Rheumatoid Arthritis: C1/C2 Subluxation
* Pathologic C2 Fracture

Pathology

* Three ossification centers form C2
* Os odontoideum represents unfused ossification center atop dens C2
* Type III fracture follows embryologic line of union between dens and body of C2
* Sudden forward or backward movement of the head, neck rigidly erect & articulations locked
* Osteoporosis in elderly predisposes to Type II fracture and nonunion
* Type I: Avulsion of tip
* Type II: Transverse fracture at base of dens
* Type III: Fracture extending into body of C2
Hangman's C2 Fracture
Terminology

* Traumatic spondylolisthesis of axis (TSA)

Imaging Findings

* Anterior displacement of C2 VB, C1, & skull vs. C3 on lateral X-ray
* Classic imaging appearance: Defects through pedicles & C2 VB anterior to C3 VB; laminae aligned
* Axial slice shows disrupted ring of C2
* Variation of fracture sites, including extension into body, not uncommon
* Dens typically spared
* Extension into vertebral artery foramen raises possibility of vertebral artery (VBA) damage
* Additional fracture levels seen in 33% of cases, C1 most commonly
* Canal at C2 enlarged
* Evaluate entire cervical spine (even upper thoracic): Associated fractures occur in 33% of cases
* Any anterior subluxation of C2 vs. C3 on lateral X-ray warrants CT
* MR if neurologic symptoms are present

Top Differential Diagnoses

* Pseudosubluxation
* Rotatory Subluxation of C2-C3
* Primary Spondylolysis

Diagnostic Checklist

* C2-C3 VB anterior subluxation with laminal line normally aligned requires CT even without fracture shown on X-ray
Burst Fracture, Cervical
Terminology

* Comminuted fracture (Fx) of vb extending through both endplates due to axial compression

Imaging Findings

* Best diagnostic clue: Wedged lower cervical vb with end plate defect, focal gibbus on lateral radiograph

Top Differential Diagnoses

* Benign compression fracture
* Flexion fracture

Clinical Issues

* Severe neck pain after trauma with axial load
* Radiculopathy or myelopathy may be present
Burst Fracture, Lumbar
Terminology

* Vertebral fracture due to axial load, involving all 3 columns

Imaging Findings

* Most common upper lumbar
* Morphology: May involve superior endplate, inferior endplate or both
* Compression of the vertebral body on anteroposterior, lateral radiography
* Posterior displacement of posterior vertebral body cortex on lateral radiography
* Widening interpediculate distance on anteroposterior radiography
* Multidetector abdomen CT scan obviates need for dedicated spine CT

Top Differential Diagnoses

* Compression fracture
* Chance fracture
* Pathologic fracture due to tumor
* Fracture-dislocation

Pathology

* Degree of neurologic injury with lumbar burst highly dependent on position of conus
* Lower lumbar burst fractures may have minimal or no neurologic signs

Diagnostic Checklist

* High association with lower extremity & pelvis fractures
Chondrocalcinosis
Click to close this panel

common



Pyrophosphate Arthropathy

Osteoarthritis

Chronic Repetitive Trauma

Idiopathic

Gout

Hyperparathyroidism/Renal OD

Progressive Systemic Sclerosis
Click to close this panel

rare:



Paraneoplastic Syndrome

Hemochromatosis

Amyloid Deposition

Acromegaly

Wilson Disease

Hemophilia

Hypothyroidism

Hypophosphatasia

Diabetes

Ochronosis (Alkaptonuria)

Oxalosis
AP radiograph shows end stage AVN of the femoral heads (white arrow), due to steroid use. The patient had a renal transplant; note the reniform soft tissue mass in the iliac fossa (white open), along with the surgical clips.
Ddx causes:

Steroids
Hip Dislocation
Femoral Neck Fractures
Post-Traumatic, Wrist
Alcohol Abuse
Sickle Cell Anemia

Radiation Osteonecrosis

Systemic Lupus Erythematosus
Standing anteroposterior radiograph shows epiphyseal fragmentation and further volume loss 12 months later in the same child. Right acetabulum and femoral metadiaphysis are osteopenic.
Imaging Findings

* Best diagnostic clue: Fragmentation and flattening of sclerotic capital epiphysis
* Size: Variable size from peripheral irregularity of epiphyseal ossification center to complete replacement of normal marrow fat
* Late: Coxa plana, coxa magna
* Hypointense epiphyseal marrow center on T1 and T2WI

Top Differential Diagnoses

* Toxic synovitis
* Septic hip
* Juvenile chronic arthritis
* Juvenile osteonecrosis

Pathology

* Insufficiency of capital epiphyseal blood supply with physis acting as a barrier
* Ischemia may be arterial or venous
* 15-20% with bilateral involvement

Clinical Issues

* Most common signs/symptoms: Limp due to groin, thigh or referred knee pain
* 3-12 years
* Median: 7 years
* Gender: M:F = 4-5:1

Diagnostic Checklist

* Use coronal T1WI to detect subtle peripheral or linear areas of epiphyseal marrow hypointensity
Psoriatic Arthritis
Major points

* Almost always accompanies skin disease, especially nail changes
* Mostly involves DIP joints of hands > feet
* Classical deformity is called “cup-in-pencil or cup-and-pencil deformity”

Radiograph of both hands demonstrates cup-and-pencil deformities of
both thumbs and erosion of DIP joint of left middle finger

* Erosion of one end of bone with expansion of the base of the contiguous metacarpal

* There is often resorption of terminal phalanges
* There is usually no osteoporosis

* Most are HLA-B27 positive, RA factor negative
* Characteristic findings
o Tends to involve smaller joints of hand and foot more than larger joints
o Asymmetrical joint involvement
o Affects both the juxta-articular and articular margins of joint


Seronegative Spondyloarthropathies

Ankylosing spondylitis

Psoriatic arthritis

Reiter’s syndrome
Inflammatory bowel disease



* As with ankylosing spondylitis and Reiter’s syndrome, bone proliferation is a major feature. Manifests itself with:
o Bony excrescences
o Periosteal new bone formation (common)
o Entire phalanx may become “cloaked” in new bone
+ “Ivory phalanx”
# Most frequent in terminal phalanges of toes, especially first
o Ankylosis is common
+ Especially in PIP and DIP joints of hands and feet
# Feature common to seronegative spondyloarthropathies
o Whiskering at sites of tendinous insertion (enthesopathy) occurs
* Soft tissue swelling of an entire digit (sausage digit)
* Destruction of IP joint of great toes with exuberant callous formation is characteristic
* Resorption of tufts of terminal phalanges is characteristic
* Spine
o Asymmetric paravertebral ossification
+ Usually thicker and larger than syndesmophytes of ankylosing spondylitis or inflammatory bowel disease
o Occasionally, there are incomplete non-marginal syndesmophytes similar to AS
* Bilateral sacroiliitis is most common
o May produce erosions and sclerosis
o May produce widening of the SI joints
o SI joint involvement occurs in about 10-25% of patients with moderate to severe psoriasis


Patterns of Psoriatic Arthritic Changes

Arthritis involving multiple joints with DIP joint involvement

Arthritis resembling Rheumatoid Arthritis

Sacroiliitis and spondylitis

Arthritis mutilans
Erosive (inflammatory) osteoarthritis
Erosive Osteoarthritis (EOA)

* Erosive or mixed erosive/productive change IP joints
* Involvement of 1st carpometacarpal (CMC) & scapho-trapezium-trapezoid
o Usually productive as in typical OA, but may be erosive
* No other findings to suggest PSA
Erosive (inflammatory) osteoarthritis
Erosive Osteoarthritis (EOA)

* Erosive or mixed erosive/productive change IP joints
* Involvement of 1st carpometacarpal (CMC) & scapho-trapezium-trapezoid
o Usually productive as in typical OA, but may be erosive
* No other findings to suggest PSA
Rheumatoid Arthritis
Rheumatoid Arthritis (RA)

* The most classic solely erosive arthropathy
o Exceptions: Ulnar "capping" in active RA; OA may develop in inactive RA
* Location is symmetric & constant
o MCP, distal radioulnar joint, radiocarpal joint; eventually intercarpal joints and IP
o MTPs, particularly 5th
o Uniform involvement hip, knee, shoulder, elbow
Soft Tissue Calcifications
ddx

* Vascular
o venous insufficiency
* Infection
o Parasitic infestation
+ cysticercosis
+ dracunculiasis
+ armillifer armillatus
+ etc.
* Neoplasm
o primary bone-forming tumor
+ osteoma
+ osteosarcoma
o tumor necrosis
* Drugs
o Vitamin D
* Autoimmune
o dermatomyositis
o scleroderma
* Trauma
o heterotopic ossification
o injection granulomas
Soft tissue ossification DDx
Traumatic myositis ossificans
burns
neurogenic

Neoplastic
synovial sarcoma parosteal sarcoma
liposarcoma

Idiopathic fibrodysplasia progressiva
Stress Fracture
Terminology

* Normal bone subject to repetitive stresses, incapable of producing a fracture on its own, leading to mechanical failure over time

Imaging Findings

* Subperiosteal new bone at any stage except earliest may be only radiographic sign
* Sclerotic bands: Cancellous bone trabecular microcallus
* Pars interarticularis fracture → spondylolysis → spondylolisthesis
* IR, FSE, FS: Areas of marrow hyperintensity against dark background of suppressed fat
* Radiography → bone scan → MR
* CT for high-risk locations such as femoral neck, or when MR negative

Pathology

* Stress fractures: Microdamage rate exceeds repair rate
* Track & field: 64% of stress fractures in females, 50% in males
* Microfracture → osteoclasts form resorption cavities adjacent to osteons → cavities coalescence → stress fracture
* Microfractures, stress fractures → periosteal stimulation → subperiosteal new bone formation
* Trabecular microfractures → microcallus → sclerotic cancellous bone

Clinical Issues

* Prognosis poorer in anterior tibial and tarsal navicular fractures
Stress fx - plain film vs nucs
Radiographic Findings

* Initially subtle, poor cortical definition, intracortical lucent striations
o Due to osteoclastic activity
o Hairline fracture progresses to complete fracture
* Subperiosteal new bone at any stage except earliest may be only radiographic sign



Nuclear MediImaging Recommendations

* Best imaging tool: Bone scan or MR when radiographs normal
* Protocol advice
o Radiography → bone scan → MR
o CT for high-risk locations such as femoral neck, or when MR negative
cine Findings

* Bone scan: Sensitivity ~ 100%
o Intense cortical uptake
o Abnormal in 6-72 hours
o Multiple areas may be seen
* Pars interarticularis stress fracture
o Increased uptake at fracture: Scan becomes normal when lesion progresses to chronic phase of spondylolysis
Stress fx DDx
DDx:
Bone Tumor

* Cortical destruction
* Soft tissue mass outside bone

Osteoid Osteoma

* Sclerosis with lucent nidus
* Night pain relieved by aspirin

Brodie Abscess

* Sclerosis with lucent nidus

Shinsplints (Medial Tibial Stress Syndrome)

* MR with fat-suppression
o High signal along medial posterior surface of tibia (traction periostitis)
o High signal in longitudinally oriented region of bone marrow within medial part of tibial diaphysis (microdamage and repair)
Slipped Capital Femoral Epiphysis
Terminology

* Salter-Harris type-1 femoral capital physis fracture due to repetitive stress of weight-bearing

Imaging Findings

* Bilateral eventually in 18-100%
* Opposite-side SCFE occurs usually within 24 months of the first occurrence
* Morphology: Capital femoral epiphysis slips posteriorly and medially relative to metaphysis
* Capital epiphysis drops toward or below Klein's line (a line drawn along top of the femoral neck and continued towards acetabulum; line ordinarily crosses a small portion of capital femoral ossification center)
* MR: Physeal widening is a constant feature, hyperintensity is inconstant; MR is more sensitive than radiography; physeal widening can be seen on MR before apparent on radiographs

Pathology

* Epidemiology: Incidence: 0.7 to 3.4:100,000

Clinical Issues

* Pain primarily in hip, groin, or proximal thigh in 85%; distal thigh or knee pain in 15%
* Age: Girls: Range 8-15 years, average 11-12 years; boys: range 10-17 years, average 13-14 years
* Premature osteoarthritis: Develops during adulthood in 1/4-1/3 patients (SCFE may be the most common cause of degenerative joint disease in middle life)
The lesion in the 1st metatarsal might be more difficult to diagnose if it were seen as an isolated case. However, it shows a mostly sclerotic lesion occupying the entire bone, causing enlargement (arrow, #2). This description fits Paget disease, a common diagnosis in an uncommon location.


The radiograph of the spine (#1) presents as classic a "picture frame" appearance of a vertebral body as possible (arrow). The mixed lytic and dense lesion of this body is seen, along with the overall enlargement of the body. There is no reasonable diagnosis but Paget disease.
Imaging Findings

* Enlarged bone with thickened and coarse trabeculae
* Starts at one end of bone and progresses along shaft
* Osteoporosis circumscripta: Well-defined lytic lesions (destructive active stage)
* Cotton-wool appearance: Mixed lytic and blastic pattern of thickened calvarium (late stage)

Top Differential Diagnoses

* Osteoblastic Metastases
* Lymphoma
* Fibrous Dysplasia
* Multiple Myeloma
* Hemangioma
* Myelofibrosis

Pathology

* Affects 3% of individuals > 40 years
* Affects 10% of individuals > 80 years

Clinical Issues

* Insidious onset, asymptomatic for many years
* Bowed and enlarged femur and tibia
* Compression fractures (soft bone despite increased density)
* Peripheral nerve compression, neurological disorders from compression of brainstem
* Elevated serum alkaline phosphatase and urine hydroxyproline
* Sarcomatous transformation (< 1%)
* Bisphosphates: Alendronate, etidronate
* Calcitonin

Lateral radiography shows osteolytic lesion involving the anterior calvarium, consistent with osteoporosis circumscripta (lytic phase).
Isolated rotatory subluxation of scaphoid
Carpal dislocations described by extent of ligamentous injury (Mayfield)

* Stage I
o Isolated rotatory subluxation of scaphoid
+ Mechanism: acute dorsiflexion of wrist
+ May be associated with rheumatoid arthritis
+ Characterized by increased distance between scaphoid and lunate > than 2 mm (Terry Thomas sign)
+ Scaphoid ring sign – ring-shaped shadow of cortex of distal pole of scaphoid seen on end
+ Associated more than 50% of the time with distal radial fractures
* Stage II
o Dislocation or subluxation of capitate
+ Exceedingly rare
* Stage III
o Perilunate dislocation
+ Triquetrial and scaphoid malrotation
+ Result of a fall on an outstretched, hyperextended hand
+ Relatively rare
+ Occurs when the lunate maintains normal position with respect to the distal radius while all other carpal bones are dislocated posteriorly
+ Very commonly associated with a scaphoid waist fracture
# Sometimes ulnar styloid as well
+ Lunate appears triangular in shape on frontal view
+ Lunate rotates forward slightly on lateral view
+ In lateral view, all other carpal bones are dislocated posterior with respect to lunate
* Stage IV
o Lunate Dislocation
+ Most severe of carpal instabilities
+ Most commonly associated with a trans-scaphoid fracture
+ Involves all the intercarpal joints and disruption of most of the major carpal ligaments
+ Produces volar dislocation and forward rotation of lunate
# Concave distal surface of lunate comes to face anteriorly
+ Capitate drops into space vacated by lunate
+ Capitate and all other carpal bones lie posterior to lunate on lateral radiograph
+ Triangular appearance of lunate on frontal projection
Perilunate dislocation
Mayfield # Stage III

* Perilunate dislocation
o Triquetrial and scaphoid malrotation
o Result of a fall on an outstretched, hyperextended hand
o Relatively rare
o Occurs when the lunate maintains normal position with respect to the distal radius while all other carpal bones are dislocated posteriorly
o Very commonly associated with a scaphoid waist fracture
+ Sometimes ulnar styloid as well
o Lunate appears triangular in shape on frontal view
o Lunate rotates forward slightly on lateral view
o In lateral view, all other carpal bones are dislocated posterior with respect to lunate
Lateral radiograph shows a typical lunate dislocation, with dorsal dislocation of the capitate (white arrow) relative to the lunate, as well as the lunate dislocated from the radius. As the lunate dislocates volarly, it rotates 90 degrees (white curved).
Terminology

* Types: Perilunate, midcarpal, & lunate dislocations
* Dislocation requires complete dissociation of the articular surfaces
* Fractures are often associated; the terminology is very specific when this occurs

Imaging Findings

* Posteroanterior view: Disruption of carpal arcs 1 & 2
* Lateral view: Dislocation of carpal bones

Pathology

* Injury patterns follow either greater arc or lesser arc patterns; the patterns may be combined in a fracture-dislocation
* Carpal dislocations much less frequent than carpal fractures
* Perilunate dislocations are most frequent & have the least severe ligamentous damage
* Lunate dislocations are least frequent & have the most severe ligamentous damage

Diagnostic Checklist

* Carpal dislocations often go unrecognized in the ER; a high degree of suspicion may prevent this
* Posteroanterior view: Evaluate the carpal arcs for disruption
* Watch for associated fractures: Radial styloid, scaphoid, and on to others around the greater arc
* Lateral view: Pick out the relevant bones and make certain there is appropriate articulation
* Radius must articulate with proximal lunate
* Lunate distal articular surface must articulate with capitate
Carpal Dislocations: locations
# Location

* Perilunate dislocation: Dislocation is at midcarpal row
* Midcarpal dislocation: Dislocation at midcarpal row, subluxation at radius-lunate articulation
* Lunate dislocation: Dislocation at both radius-lunate articulation & midcarpal row
Ddx for diffuse dense bones
Neoplasm
Mets, Myelofibrosis
Mastocytosis, Lymphoma
Congenital
Craniotubular dysplasia
Osteopetrosis
Pyknodysostosis
Sickle cell
Metabolic
Paget's
Renal osteodystrophy
Fluorosis
Hypervitaminosis A&D
Epiphyseal bone lesion DDx
Chondroblastoma
Osteomyelitis

after fusion:
GCT
enchondroma ABC
Charcot, Neuropathic
Imaging Findings

* "5 D's"
* Normal bone density for patient
* Joint distention
* Bony debris
* Cartilage destruction
* Joint disorganization (or dislocation or deformity)
* Location is strongly suggestive of etiology
* Shoulder: Syringomyelia
* Wrist: Diabetes, syringomyelia
* Spine: Spinal cord injury, tabes, diabetes
* Hip: Alcohol, tabes
* Knee: Tabes, congenital indifference or insensitivity to pain, steroid injection
* Ankle/foot: Diabetes

Pathology

* Likely an initial alteration in sympathetic nerve control of osseous blood flow →
* Hyperemia & active bone resorption
* Secondary neurotraumatic mechanism resulting in a destructive cycle
* Blunted pain sensation & proprioception →
* Relaxation of skeletal supporting structures →
* Chronic instability →
* Recurrent injury by normal biomechanical stresses but abnormal joint loading →
* Osseous fragmentation & joint disorganization

Diagnostic Checklist

* Even though debris & other findings may be distant from joint, establish that the primary process is articular; this makes the diagnosis
Pigmented Villonodular Synovitis (PVNS)
Terminology

* Monoarticular proliferation of hemorrhagic synovium
* Occurs in joint, bursa, tendon sheath
* PVNS: Diffuse, articular form
* Giant cell tumor of the tendon sheath: Localized, extra-articular form

Imaging Findings

* Radiograph: Large effusion ± associated erosions & subchondral cysts
* MR: Effusion with synovial proliferation, low signal on all sequences & blooms on gradient echo
* PVNS (intraarticular): 80% occur in knee
* Knee > ankle > hip > shoulder > elbow
* Hand & wrist (65-89%): Volar aspect of digits
* May be focal nodular mass
* May be diffuse, with villonodular proliferation of entire synovium & in all potential joint recesses
* Best imaging tool: MR demonstrates extent; characteristic but not pathognomonic (diagnostic in 95%)
* Protocol advice: Gradient echo imaging shows blooming phenomenon of hemosiderin-laden nodules

Diagnostic Checklist

* If suspicious of PVNS, use gradient echo sequence to elicit blooming
* Blooming on gradient echo is not pathognomonic for PVNS; hemophilia is other major consideration
* Search carefully for all regions of involvement, including all recesses, to achieve complete resection
Salter Harris classification, Tx, Px

Imaging Findings

* Detection of subtle or occult fractures may change Salter-Harris staging and orthopedic management
* Protocol advice: Opposite-side comparison radiographs may help determine whether Salter-Harris type I fracture is present

Top Differential Diagnoses

* Distal radial physis stress injury: Occurs in 17% of gymnasts' wrists

Pathology

* 18% of childhood fractures involve physeal injury
* Causes of distal tibial physeal fractures: Nonspecific fall (25%), skateboard accident (16%), motor vehicle accident (12%), football (12%), soccer (8%)

Clinical Issues

* Percentage of physeal fractures in both boys and girls: 18%
* Overall complication rate: ~14%
* Complications: Premature early or complete epiphyseal closure, limb shortening or angulation, persistently trapped periosteum, joint incongruity
* Most substantial complications occur at knee and ankle
* Prolonged immobilization (3-18 months) may be needed in children with myelodysplasia

Diagnostic Checklist

* Follow knee and ankle fractures for at least a year or until skeletal maturity for early detection of premature closure of epiphyses
Staging, Grading, or Classification Criteria

* Type I: Involves only physis
* Type II: Involves physis and metaphysis
* Type III: Involves physis and epiphysis
* Type IV: Involves physis, metaphysis, and epiphysis
* Type V: Crush fracture involving all or part of physis (rare)
o Usually first recognized when cone epiphyses or partial epiphyseal arrest becomes apparent later
* Type VI-IX, as described by Ogden 1981 (rare)
o Perichondral ring injury (type VI), intra-epiphyseal fracture not involving physis (type VII), metaphysis fracture not involving physis directly but → ischemic growth disturbance (type VIII), periosteal injury → disturbed diaphyseal growth (type IX)


Treatment

* Casting for low Salter-Harris categories
* Open reduction and internal fixation often required with higher categories
* Prolonged immobilization (3-18 months) may be needed in children with myelodysplasia
periosteal reaction (generic) this case is syphilis.

Anteroposterior radiograph shows ulnar metaphyseal lucent band (arrow), radial metaphysis destructive lesion (curved arrow), and periosteal reaction (open arrows).
Periosteal reaction in children: scurvy (dense metaphyseal lines), Caffey’s (tibia, ulna, mandible), trauma, hypervitaminosis, leukemia, lymphoma, neuroblastoma, infection, physiologic, prostaglandins - SCALP
Hyperparathyroidism types
hyperparathyroidism findings
brown tumor

accumulation of osteoclasts

seen with hpth
hpth subperiosteal resorption
- radial side of phalanges
HPTH

Axial bone CT shows thick skull with mild sclerosis and a granular appearance of the diploe, as well as loss of distinction of inner & outer table, in a patient with chronic renal failure and secondary hyperparathyroidism.
Juvenile Idiopathic Arthritis (JRA)

Coronal 3D GE image shows diffuse hyperintense erosions throughout the wrist (arrows).
Terminology

* Juvenile rheumatoid arthritis (JRA), juvenile idiopathic arthritis, juvenile chronic arthritis, Still disease
* Begins < 16 year old
* ≥ 6 weeks of disease
* Arthritis (1 or more joints)
* Oligoarthritis (Pauciarticular): ≤ 4 joints involved
* Polyarthritis: ≥ 5 joints involved
* Systemic: Arthritis with characteristic fever
* Exclusion of other forms of juvenile arthritis

Imaging Findings

* Most common cause of chronic arthritis in children

Top Differential Diagnoses

* Pigmented villonodular synovitis (PVNS)
* Synovial chondromatosis or osteochondromatosis (SOC)
* Hemophilic arthropathy
* Infectious or septic arthritis
* Transient synovitis
* Leukemia

Pathology

* Unknown
* Epidemiology: 10-15 cases/100,000

Clinical Issues

* Fatigue
* Age: Peak: 1-3 years (largest peak) & 8-10 years (smaller peak)
* Gender: M < F overall, systemic M = F
Talar beaking: dorsal beaking of the talar head may indicate underlying tarsal coalition, most commonly talo-calcaneal. However, it can also indicate Rheumatoid arthritis, DISH and acromegaly.
Imaging Findings

* Best diagnostic clue: Approximation or incorporation of talus + calcaneus through middle facet vs. calcaneus to navicular through anterior facet
* Synostosis = complete coalition
* Synchondrosis = cartilaginous
* Syndesmosis = fibrous

Top Differential Diagnoses

* Subtalar Fractures
* Osteoarthritis
* Osteochondral Lesion of the Talus (OLT)

Pathology

* Congenital = failure of differentiation + segmentation of primitive mesenchyme
* Acquired = arthritis, infection, trauma + neoplasm
* 90% coalition = talocalcaneal + calcaneonavicular

Clinical Issues

* Most common signs/symptoms: Limitation of subtalar joint motion; pain
* Talocalcaneal coalition = rearfoot pain with localization to sustentaculum medially + sinus tarsi laterally
* Limitation of subtalar + mid tarsal joint motion including peroneal muscle spasm
* Tarsal coalition = most common cause of peroneal spastic flatfoot

Diagnostic Checklist

* Talocalcaneal coalitions require coronal images
Unicameral bone cyst

Axial NECT shows a lytic expansile lesion in the central iliac bone. Cortical thinning without periosteal reaction is noted.
Imaging Findings

* Best diagnostic clue: Well-defined central lytic lesion
* Fallen fragment sign secondary to pathologic fracture (pathognomonic)

Top Differential Diagnoses

* Aneurysmal Bone Cyst (ABC)
* Fibrous Dysplasia
* Fibroxanthoma
* Bone Abscess
* Enchondroma
* Langerhans Cell Histiocytosis
* Brown Tumors

Pathology

* Epidemiology: 3% of primary bone lesions

Clinical Issues

* Most lesions asymptomatic
* Pain, swelling, stiffness at closest joint
* 66% of cysts present with pathologic fractures
* Spontaneous regression in majority of cases
* Recurrence rate after injection, curettage: 20-45%
* Dual needle aspiration and percutaneous injection of corticosteroids (80-200 mg methylprednisolone)
* Open curettage with bone graft in weight bearing bones

Diagnostic Checklist

* Starts at one end of bone, migrates towards diaphysis with bone growth
Anteroposterior radiography show expansile purely lytic lesion at the base of the proximal phalanx of the 4th digit. The radiolucent appearance is typical for enchondromas of the hands.
Enchondroma

Imaging Findings

* Best diagnostic clue: Well-defined lytic lesion with chondroid matrix (rings and arcs calcifications)
* Best imaging tool: Radiographs usually diagnostic
* Protocol advice: CT best imaging modality to detect chondroid matrix

Top Differential Diagnoses

* Bone Infarct
* Chondrosarcoma
* Epidermoid Inclusion Cyst
* Juxtacortical Chondroma

Pathology

* Second most common benign bone tumor
* 2-10% of all bone tumors

Clinical Issues

* Usually asymptomatic
* Painless swelling
* Pain, unexplained by injury or fracture, should raise suspicion of malignancy
* Heal after curettage and bone grafting
* Recurrence of incompletely curetted lesions in short bones of hands
* Recurrence of long bone lesions suggests malignancy
* Asymptomatic lesions require no treatment
* Painful or worrisome lesions require curettage and careful microscopic evaluation

Diagnostic Checklist

* In absence of a fracture, painful enchondroma is considered malignant until proven otherwise
# Ollier disease

* Multiple enchondromas
o Typically asymmetric involvement of half of body
o Bilateral involvement may occur
Ollier disease also known as enchondromatosis, is a non-hereditary, sporadic, skeletal disorder characterised by multiple enchondromas that are principally located in the metaphyseal regions.

Some authors make a distinction between Ollier disease and enchondromatosis on the basis of distribution. In the original description of Ollier disease, the enchondromas where predominantly confined to one side and limited to the limbs. As such, some authors prefer to use the term Ollier disease in cases where this distribution is present, and use enchondromatosis or multiple enchondromatosis for cases where the distribution is more symmetric 5.
Epidemiology

Ollier disease is seen in both sexes without gender predilection, and usually becomes apparent by early childhood 3-4. The condition is non-hereditary and is thought to occur as a result of random and spontaneous mutations.
Clinical presentation

Clinical presentation is usually with deformity and pain (present only during periods of rapid growth) 3-4. If pain occurs when the child is older, this should raise the concern of malignant transformation or pathological fracture. If involvement of the lower limbs is significant, leg length discrepancy may occur.

Once the individual stops growing then in general so do the enchondromas. If growth occurs then, this too is a sign of potential malignant transformation 4.
Associations

There is an increased risk of chondrosarcoma occurring later in life. The risk has been reported to be up to 25 - 30% at 40 years 1-2.

The presence of enchondromatosis and soft-tissue haemangiomas in the hands and feet is termed Maffucci syndrome, and also carries an increased risk of cancer.

Occasionally patients will also be afflicted with multiple osteochondromas. This rare combination is known as metachondromatosis.
Distribution

They can occur anywhere but most frequently involve the short tubular bones of the hands and feet. Most patients have bilateral involvement but often significant asymmetry 4.
Radiographic features

Plain films show multiple enchondromas. Larger lesions can show cartilage calcification in a typical rings and arcs pattern.

For further discussion of appearances, please refer to the article on enchondromas.
Treatment and prognosis

The extent of disease is highly variable and thus so is the degree of impairment. If only a few bones are involved then little if any handicap is present, although the affected bones do have a higher rate of fracture.

If extensive involvement then growth impairment, deformity and functional impairment may be present, and these may require corrective surgery.
Differential diagnoses

* Maffucci syndrome : presence of soft tissue haemangiomas, heralded on plain films by phleboliths.
* metachondromatosis : osteochondromas also present
* sarcoidosis : lace like phalanges
Calcium pyro phosphate dihydtrate (CPPD) deposition disease also known as pseudogout

Partially calcified pseudomass behind the dens, extensive narrowing and erosive changes of the end-plates at the C2-C3 level, large erosion anteriorly in the C3 body. Intervertebral disc calcifications at the C6-C7 and C7-Th1 levels, calcifications in the posterior and anterior longitudinal ligaments and annulus fibrosus, calcifications at the interspinous ligament C7, spondylophyte formation anteriorly.
Three main manifestations of CPPD deposition are recognised:

1. chondrocalcinosis
2. crystal induced synovitis (pseudogout syndrome)
3. pyrophosphate arthropathy

Pathology

The crystals are positively birefringent on microscopy.
Associations

* primary hyperparathyroidism
* haemochromatosis
* hypomagnesaemia 2
* gout

Radiographic features

Chondrocalcinosis can occur in many locations. Notable sites include

* triangular fibrocartilage complex of wrist (TFCC)
* peri odontoid tissue around the dens : crowned dens syndrome 5
* intervertebral discs

Features of degenerative joint disease in joints that are not normally affected by it (i.e. non-weightbearing joints):

* shoulder joint
* elbow joint
* radiocarpal joint
* patellofemoral joint
Osteoid Osteoma
Imaging Findings

* Best diagnostic clue: Well-defined lytic to sclerotic lesion with surrounding sclerosis

Top Differential Diagnoses

* Osteomyelitis (Brodie's Abscess)
* Enostosis (Bone Island)
* Stress Fracture
* Osteoblastoma
* Osteoma

Pathology

* Nidus has limited growth potential
* 4% of primary bone tumors
* 12% of benign bone tumors

Clinical Issues

* Most common signs/symptoms: Local pain worse at night, decreased by salicylates in less than 30 minutes (75%)
* Local swelling and point tenderness
* Spinal involvement: Painful scoliosis with concavity of curvature toward side of lesion
* No malignant potential
* No growth progression
* Can regress spontaneously
* Surgical en-block resection of nidus curative if nidus completely removed
* Percutaneous removal (CT guided)
* Percutaneous radio-frequency ablation (CT guided)
* Medical management: Nonsteroidal antiinflammatory drugs
Myositis Ossificans - don't touch lesion
Imaging Findings

* Mature bone formation within soft tissues, seen in later stages of the disease
* Earlier stages are confusing: The bone is amorphous & appears similar to tumor bone formation
* Common in areas prone to trauma
* Shoulder & elbows in burn patients
* Formed about the pelvis & hips in spinal cord or brain injured patients
* Distinctive & related to time following trauma
* 0-2 weeks: Soft tissue mass with indistinct surrounding soft tissue planes
* 3-4 weeks: Amorphous osteoid forms within the mass; adjacent periosteal reaction may be seen
* 6-8 weeks: Sharper cortex begins to form about the lacy central osseous mass
* 5-6 months: Mature bone formation

Top Differential Diagnoses

* Tumoral Calcinosis
* Parosteal Osteosarcoma
* High Grade Surface or Soft Tissue Osteosarcoma

Diagnostic Checklist

* History of trauma & the timing relative to imaging is crucial to diagnosis, though trauma may be denied
* Must avoid biopsy during the early stages to avoid misdiagnosis of tumor
* Do not overinterpret early amorphous osteoid formation as tumor bone
* Watch for peripheral organization, either as organized bone on radiograph or CT, or as "halo" on MR
Cortical desmoid

Distal femoral metaphyseal irregularity


Irregular lucency of the posterior medial aspect of the distal femoral metaphysis. May be secondary to chronic avulsion injury of the adductor magnus.
Terminology

* DFMI: Irregularity of femoral cortex underneath attachment of medial head of gastrocnemius muscle or most distal insertion of adductor magnus

Imaging Findings

* Best diagnostic clue: Isolated radiographic finding without soft tissue mass or symptoms
* Posterior medial femoral metaphysis just lateral to adductor tubercle
* Occurs at attachment of medial head of gastrocnemius or distal insertion of adductor magnus muscles
* Bilateral: 25-100%
* May migrate with age away from epiphysis
* Long axis parallel to long axis of femur
* May be periosteal reaction
* May contain bone spicules
* Healing: DFMI disappears or may be residual cortical thickening and sclerosis
* Sensitivity: MR > radiographs
* Lesions enhance on T1 C+ sequences
* Hypointense rim at base of lesion in all sequences
* Best view: Oblique lateral radiograph of distal femur with 20-30° internal rotation of hip

Pathology

* Composed of cartilage, fibrous vascular tissue, fibrin
* Cellular components: Chronic inflammatory cells, giant cells, osteoclasts

Clinical Issues

* Often disappears after epiphyseal closure
Geode or subchondral cyst:
Axial bone CT shows marked right TMJ deformity with subchondral cysts (white curved) in deformed condyle. The fossa is also enlarged in this patient with advanced degenerative disease.
Subchondral Cyst (Geode)

* Key facts
o Intrusion of synovium through cartilage-denuded articular bone surface
o Rheumatoid (RA) or osteoarthritis (OA)
* Imaging
o Sharply marginated subcortical condylar lucency with thin sclerotic margins
o Found beneath pressure segment of joint adjacent to area of maximal joint narrowing
o RA: Begins at chondro-osseous junction
o Other OA findings: Joint space narrowing, articular sclerosis, osteophytes
Dorsal Defect of Patella (Mimic) don't touch lesion


* Lytic, round lesion in upper outer quadrant of patella
* Located on articular surface
* Overlying cartilage is intact



Anteroposterior radiograph shows a round lytic "lesion" occupying the upper outer quadrant of the patella (white arrow).
pseudocyst of the humerus
a don't touch lesion
os odontoideum
* An os odontoideum is a round or oval ossicle that lies above and separate from the body of C-2. A normal odontoid process is absent.
* Atlantoaxial instability may be present.
* Must be distingushed from an odontoid fracture
Fibroxanthoma (Non-Ossifying Fibroma
Imaging Findings

* Best diagnostic clue: Well-defined expansile eccentric lytic lesion with scalloped sclerotic margins in metaphyses of long bones
* FCD: < 2 cm, within the cortex
* NOF: > 2 cm, encroach medullary cavity
* Best imaging tool: Radiographs diagnostic

Top Differential Diagnoses

* Cortical Desmoid
* Aneurysmal Bone Cyst (ABC)
* Unicameral Bone Cyst (UBC)
* Fibrous Dysplasia
* Chondromyxoid Fibroma (CMF)

Pathology

* Most common fibrous lesion of bone
* Occurs in 20-30% of normal population during 1st and 2nd decades of life
* Jaffe-Campanacci syndrome
* Neurofibromatosis type 1

Clinical Issues

* Most common signs/symptoms: Usually asymptomatic
* May cause pain, pathologic fracture
* Benign lesion, no malignant transformation
* Spontaneous regression
* Usually does not require treatment
* Curettage with bone grafting of larger lesions at risk for fracture

Diagnostic Checklist

* Don't touch lesion
Typical case of bone island in a thoracic vertebra.
Terminology

* Synonyms: Enostosis, sclerotic island, calcified island, compact island
* Asymptomatic focal areas of bony sclerosis

Imaging Findings

* Best diagnostic clue: Small focal areas of sclerosis, with brush-like margins
* Any bone may be involved
* Most common in pelvis, femur, ribs
* Size: 1 mm to several cm
* Usually normal

Pathology

* General path comments: Normal compact bone
* Etiology: Developmental
* Epidemiology: Spine involvement in up to 14% of subjects
Anteroposterior radiograph shows patchy sclerosis of metatarsals & phalanges, consistent with bone infarcts in a child with hand-foot syndrome. Often impossible to distinguish osteomyelitis from bone infarction.
Bone Infarct

Key facts

* Typical presentation: central lesion in metaphysis or diaphysis with a well defined serpentiginous border.
* Bone infarcts resemble cartilaginous tumors.


The term bone infarct or osteonecrosis is used for lesions in the diaphysis or metaphysis. If the osteonecrosis is located in the epiphysis, the term avascular osteonecrosis is used.
* Acroosteolysis is characterized by bone resorption in the fingers and toes.
* Radiographs show terminal phalangeal resorption in the fingers and toes.
PINCH FO

* Psoriasis
* Pyknodysostosis
* Injury (thermal burn, frost bite)
* Neuropathy
o Diabetes
o Leprosy
* Collagen vascular disease
o Scleroderma
o Raynaud's disease
* Hyperparathyroidism
* Familial (Hadju-Cheney syndrome)
* Other
o Polyvinyl chloride exposure
o Progeria
Pycnodysostosis
Pycnodysostosis causes the bones to be abnormally dense (osteopetrosis); the last bones of the fingers (the distal phalanges) to be unusually short; and delays the normal closure of the connections (sutures) of the skull bones in infancy, so that the "soft spot" (fontanel) on top of the head remains widely open.
Hajdu-Cheney syndrome, also called acroosteolysis with osteoporosis and changes in skull and mandible, arthrodentoosteodysplasia and Cheney syndrome,[1] is an extremely rare autosomal dominant congenital disorder[2][3] of the connective tissue characterized by severe and excessive bone resorption leading to osteoporosis and a wide range of other possible symptoms. Approximately 50 cases have been reported worldwide.
72
Osteogenesis Imperfecta
Terminology

* Connective tissue disorder due to abnormalities in type I collagen (COL1A1, COL1A2) associated with osseous fragility and fractures

Imaging Findings

* Best diagnostic clue: Presence of fractures distinguishes OI from other skeletal dysplasias
* Callus formation gives bones a "crumpled" appearance
* Decreased mineralization
* Multiple rib fractures ("beading")
* Skull deformation from transducer pressure ("soft" bones)

Top Differential Diagnoses

* Hypophosphatasia
* Achondrogenesis
* Campomelic dysplasia
* Thanatophoric dysplasia (TD)

Pathology

* Most autosomal dominant
* Type I: Fractures rare at birth
* Type II: Most severe form, multiple fractures, lethal
* Type III: Multiple fractures at birth, progressive severe deformity of limbs, spine, skull
* Type IV: Delayed presentation, clinical and radiographic spectrum between type I and type III

Diagnostic Checklist

* Severe limb shortening with limb and rib fractures, most likely lethal OI
Anteroposterior radiograph of the lower extremities shows poorly ossified bones with thin cortices (white open) in a newborn with type IV OI. Note the healed fracture (white curved) and severe bowing (white arrow) .
Hemophilia
Terminology

* X-linked recessive bleeding disorder resulting from clotting factor deficiencies
* Pseudotumor of hemophilia: Non-neoplastic mass lesion that occurs with repeated focal intraosseous, subperiosteal, or soft tissue bleeding

Imaging Findings

* Dense hemarthrosis, arthropathy, growth deformity (balloon-like joints)
* MR: "Blooming" nodules from hemosiderin deposits
* Arthropathy: Knee > elbow > ankle > hip > shoulder
* May be polyarticular, but usually not symmetric
* Pseudotumor: Soft tissue > bone > subperiosteal
* Intraosseous pseudotumor: Femur > pelvis > tibia > small bones of hand > calcaneus
* Soft tissue pseudotumor: Thigh > gluteal region > iliopsoas muscle

Top Differential Diagnoses

* Arthropathy: Juvenile Idiopathic Arthritis (JIA)
o JIA occurs in skeletally immature patient, so hyperemia results in overgrowth & early fusion
* Arthropathy: Tuberculosis Arthritis (TB)
o If TB arthritis occurs in skeletally immature patient, can get same growth disturbance

Diagnostic Checklist

* Early MR of arthropathy should be obtained; allows early assessment which leads to aggressive prophylaxis & delays joint complications
Discitis

Coronal T2WI MR in same patient as on left shows edema and widening of paraspinal soft tissues (open arrows), narrowing of the disc (arrow), and high signal of adjacent vertebral bodies.
Terminology

* Infectious spondylitis
* Inflammatory process of the intervertebral disc space often with unknown etiology

Imaging Findings

* Lumbar spine most commonly effected
* Most common sites are L3-4 and L2-3
* Lower thoracic spine can also be involved
* Radiographic changes often lag behind development of symptoms
* Radiographic findings in lumbar discitis
* Irregularity or poor definition of adjacent vertebral endplates
* Sclerosis of adjacent vertebral bodies
* Narrowing of the intervertebral disc space
* Radiographic findings in thoracic discitis
* Paravertebral soft tissue widening
* May be present prior to disc space narrowing

Pathology

* Blood cultures or cultures from tissue sampling of disc area yield positive results in only 1/3 of cases
* When identified, Staphylococcus aureus is most common etiologic agent

Clinical Issues

* Diagnosis is often delayed because of nonspecific presentation
* Most common in children 6 months to 4 years
* Lumbar location most common in this age group
* Second peak during 10-14 years of age
* Thoracic location most common in this age group
Monteggia: Fracture ulnar shaft & dislocation radiocapitellar joint
Galeazzi: Fracture radial shaft & dislocation DRUJ
Hypertrophic Osteoarthropathy
Imaging Findings

* Best diagnostic clue: Tc-99m (diphosphonate) bone scan shows symmetric ↑ activity of diaphyseal, metaphyseal surfaces of long bones
* Distal femur, tibia/fibula and radius/ulna most common
* Skeletal scintigraphy for evaluation and surveillance
* Linear increased tracer accumulation = periosteal reaction

Top Differential Diagnoses

* Skeletal Metastases
* Thyroid Acropachy
* Paget Disease
* Venous Insufficiency
* Hypervitaminosis A
* Infantile Cortical Hyperostosis
* Camurati-Engelmann Disease
* Stress Fracture

Pathology

* Primary HOA: Autosomal dominant
* Secondary HOA: No significant genetic correlation
* Epidemiology: Secondary HOA accounts for ≥ 95% of HOA
* Pulmonary disease associated with secondary HOA: Classically bronchogenic carcinoma or pulmonary metastases

Diagnostic Checklist

* Tc-99m MDP bone scan to evaluate therapy response
* Consider secondary HOA in patients undergoing bone scintigraphy for malignancy staging workup
Causes of Hypertrophic Osteoarthropathy - intrathoracic and extrathoracic
* Classically, neoplastic or infectious thoracic disease associated with secondary HOA (although cardiac, abdominal processes not uncommon)
* Pulmonary disease associated with secondary HOA: Classically bronchogenic carcinoma or pulmonary metastases
o ≥ 80% of cases associated with bronchogenic carcinoma
o Pleural mesothelioma: Secondary HOA in ≤ 50%
o Other: Chronic obstructive pulmonary disease, pleural fibroma, chronic infection, cystic fibrosis, Hodgkin lymphoma, interstitial fibrosis
* Cardiac disease, particularly with right-to-left shunt
o Includes patent ductus arteriosis (PDA) with pulmonary hypertension
* Less common with chronic extrathoracic diseases
o Chronic inflammatory processes: Ulcerative colitis, endograft infection, Whipple disease
o Bowel disease: Crohn disease, lymphoma, bacillary and amebic dysentery
o Liver disease: Cirrhosis (alcoholic, biliary, other), hepatopulmonary syndrome
o Neoplasm: Esophageal, pancreatic, gastric, nasopharyngeal cancer
Looser Zones
Looser's zones are seen in persons with osteomalacia, chronic renal disease, fibrous dysplasia, hyperthyroidism, Pagets disease, renal osteodystrophy and X linked hypophosphataemia.
looser zones
associated with osteomalacia

Terminology

* Osteomalacia: Incomplete mineralization of normal osteoid following closure of growth plates
* Osteomalacia: Typically involves trabecular & cortical bone
* Rickets: Incomplete mineralization of normal osteoid in immature skeleton
* Rickets: Manifestation of osteomalacia in children
* Rickets: Primarily involves growth plates, metaphyseal zones of provisional calcification
* Renal osteodystrophy: Combined features of osteomalacia, secondary hyperparathyroidism and osteoporosis

Imaging Findings

* Plain film, CT: Smudgy, coarsened, demineralized bone; Looser zones, insufficiency fractures
* Bone scan: Accentuation of anterior ends of all ribs in an adult; uptake in fractures, Looser zones
* Bone scan findings of osteomalacia may coexist with bone scan findings of secondary hyperparathyroidism in spectrum of renal osteodystrophy
* Aluminum osteomalacia: ↓ uptake by bones; diffuse ↑ uptake by soft tissues, liver
* FDG PET: May show similar pattern to that on bone scan; may identify tumor in oncogenic osteomalacia

Pathology

* Normal osteoid
* Reduced calcification (especially in new bone)

Diagnostic Checklist

* Osteomalacia may coexist with findings of secondary hyperparathyroidism in renal osteodystrophy
Terminology

* Osteomalacia: Incomplete mineralization of normal osteoid following closure of growth plates
* Osteomalacia: Typically involves trabecular & cortical bone
* Rickets: Incomplete mineralization of normal osteoid in immature skeleton
* Rickets: Manifestation of osteomalacia in children
* Rickets: Primarily involves growth plates, metaphyseal zones of provisional calcification
* Renal osteodystrophy: Combined features of osteomalacia, secondary hyperparathyroidism and osteoporosis

Imaging Findings

* Plain film, CT: Smudgy, coarsened, demineralized bone; Looser zones, insufficiency fractures
* Bone scan: Accentuation of anterior ends of all ribs in an adult; uptake in fractures, Looser zones
* Bone scan findings of osteomalacia may coexist with bone scan findings of secondary hyperparathyroidism in spectrum of renal osteodystrophy
* Aluminum osteomalacia: ↓ uptake by bones; diffuse ↑ uptake by soft tissues, liver
* FDG PET: May show similar pattern to that on bone scan; may identify tumor in oncogenic osteomalacia

Pathology

* Normal osteoid
* Reduced calcification (especially in new bone)

Diagnostic Checklist

* Osteomalacia may coexist with findings of secondary hyperparathyroidism in renal osteodystrophy

Sicle cell anemia: msk complications:
Terminology

* Autosomal recessive inherited hemoglobinopathy (homozygous, HbSS); radiographic MSK findings reflect one or both of the following processes
* Chronic hemolytic anemia
* Consequences of microvascular occlusion created by sickled cells when exposed to low oxygen tension

Imaging Findings

* Generalized patchy bone density, reflecting chronic diffuse bone infarcts
* Avascular necrosis, especially of femoral head, humeral head, or vertebral bodies
* Chest: Cardiomegaly, pulmonary infarct
* Abdomen: Gallstones, absence of spleen (splenic infarct, with eventual autosplenectomy)

Pathology

* Structural defect in hemoglobin HbS: Glutamic acid in position 6 substituted with valine
* Order of events leading to infarct: Lowered oxygen tension →
* Altered shape & plasticity of red blood cells →
* Increased blood viscosity, stasis →
* Occlusion of microvasculature by sickled cells → infarct/AVN

Diagnostic Checklist

* Acute infarction & osteomyelitis can be indistinguishable on imaging; pattern of rim-enhancement on MR can be useful
* Red marrow replacement of fatty marrow can be patchy and confusing
Medial Epicondyle Avulsion
Terminology

* Medial epicondyle (ME) avulsion, medial epicondylitis (apophysitis), little leaguer's elbow, pitcher's elbow, golfer's elbow, medial tennis elbow
* Acute injury
* Medial epicondylar avulsion
* Chronic stress injury: Golfer's elbow, pitcher's elbow, little leaguer's elbow, medial tennis elbow
* Degeneration of the common flexor tendon secondary to overload caused by chronic valgus stress

Imaging Findings

* Should see medial epicondyle on AP radiograph if trochlea is identified
* Helps to exclude an entrapped medial epicondyle, can simulate the trochlear ossification center
* AP & lateral radiographs to exclude an acute avulsion
* T1, FS PD FSE (best), FS T2 FSE &/or STIR for ligament/tendon evaluation

Pathology

* Medial epicondyle avulsion; incidence of up to 50% in elbow dislocations
* Ulnar nerve injury in dislocation (25-50%)
* Trapped medial epicondyle in the elbow joint following dislocation (up to 20%)

Diagnostic Checklist

* Should see medial epicondyle when trochlear ossification center is identified
* Displaced medial epicondyle can simulate the trochlear ossification center
Medial Epicondyle Avulsion
Terminology

* Medial epicondyle (ME) avulsion, medial epicondylitis (apophysitis), little leaguer's elbow, pitcher's elbow, golfer's elbow, medial tennis elbow
* Acute injury
* Medial epicondylar avulsion
* Chronic stress injury: Golfer's elbow, pitcher's elbow, little leaguer's elbow, medial tennis elbow
* Degeneration of the common flexor tendon secondary to overload caused by chronic valgus stress

Imaging Findings

* Should see medial epicondyle on AP radiograph if trochlea is identified
* Helps to exclude an entrapped medial epicondyle, can simulate the trochlear ossification center
* AP & lateral radiographs to exclude an acute avulsion
* T1, FS PD FSE (best), FS T2 FSE &/or STIR for ligament/tendon evaluation

Pathology

* Medial epicondyle avulsion; incidence of up to 50% in elbow dislocations
* Ulnar nerve injury in dislocation (25-50%)
* Trapped medial epicondyle in the elbow joint following dislocation (up to 20%)

Diagnostic Checklist

* Should see medial epicondyle when trochlear ossification center is identified
* Displaced medial epicondyle can simulate the trochlear ossification center
Flattened Vertebral Body, Solitary
DDX

common



Pathologic Vertebral Fracture

• Osteoporosis

• Metastases, Lytic Osseous

• Metastases, Blastic Osseous

• Plasmacytoma

• Multiple Myeloma

• Steroids

• Langerhans Cell Histiocytosis

• Giant Cell Tumor

• Ewing Sarcoma

• Leukemia

• Lymphoma

• Osteomyelitis, Pyogenic

• Hemangioma

Burst Fracture

Chance Fracture

Failure of Vertebral Formation
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less common



Kümmell Disease
Flattened Vertebral Body, Multiple
ddx

common



Traumatic Fractures

Pathologic Vertebral Fracture

• Osteoporosis

• Metastases, Lytic Osseous

• Multiple Myeloma

• Metastases, Blastic Osseous

• Leukemia

• Lymphoma

Sickle Cell

Scheuermann Kyphosis
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less common



Osteogenesis Imperfecta

Achondroplasia

Cushing Disease

Spondyloepiphyseal Dysplasia

Caudal Regression Syndrome
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rare



Radiation Therapy to Spine in Childhood
Scheuermann Kyphosis
Scheuermann kyphosis

* 5° wedging of at least 4 contiguous vertebrae
* Schmorl nodes & undulating vertebral endplates
* Usually involves thoracic spine
Gout
Terminology

* Hyperuricemia, resulting in sodium urate crystal deposition in soft tissues & joints

Imaging Findings

* Best diagnostic clue: Dense tophi, juxtaarticular erosions with overhanging edges
* 1st metatarsal phalangeal (MTP) most frequent site
* Lower extremity > upper extremity
* Gouty tophus has constant T1 MR appearance: Intermediate homogeneous signal intensity
* Gouty tophus appears variably on T2 & other fluid sensitive sequences: Mixed low and high signal
* Gouty tophus enhances with contrast

Clinical Issues

* Gender: M:F = 20:1
* Ethnicity: Pacific Islanders (Maori, Polynesians) > Caucasians > African Americans

Diagnostic Checklist

* Radiograph usually diagnostic; obviates need for MR
* MR of a mass should not be interpreted without corresponding radiograph
* Septic arthritis & crystal-induced arthropathy can occur simultaneously; aspirated fluid should be evaluated for both
* A good adage to remember: Gout can look like anything & present anywhere in the musculoskeletal system!
* Location of disease may be atypical
* Soft tissue tophus may mimic an infectious or neoplastic process
* Gout is common; maintain a high index of suspicion!