Pediatric Musculoskeletal Infections - PedRad.org

Pediatric Musculoskeletal Infections

Tal Laor, M.D.

Cincinnati Children’s Hospital Medical Center

University of Cincinnati College of Medicine

SPR Pediatric MSK Imaging Austin, TX- Jan 2016

http://theodysseyonline.com/

Osteomyelitis Initial Focus

• Usually hematogenous source – All age groups: S. aureus

•Panton-Valentine leukocidin (PVL genes)

– <4 mo: also enterobacter, grp A & B strep

– >4 mo - 4 years: Kingella kingae, H. flu

– Sickle cell: also Salmonella

Metaphysis

• Increased vascularity

– Gd and 99mTc-MDP uptake

Subtracted image (+Gd)

• Sluggish flow

• Decreased phagocytosis

* *

Metaphysis

• Hematopoietic marrow

– Hypointense T1

– Relatively hyperintense T2 and inversion recovery

– Normal marrow has more fat than muscle or infected marrow

T1

FSE T2

*

*

“Metaphyseal Equivalents”

X

X

X

X

X

X

X

X

Medullary extension

Subperiosteal and soft tissue extension

Epiphyseal and articular extension

Local Spread

Local Spread

Direct articular

extension

Local Spread

•Hip

•Shoulder

•Elbow

•Ankle

Extension into Subperiosteal Space

• Periosteum

– Loose attachments

– Tightly tethered at physis

– Hypointense on all sequences: easy to see

• Extensive cortical fenestration

FSE T2

• Periosteum

– Loose attachments

– Tightly tethered at physis

– Hypointense on all sequences: easy to see

• Extensive cortical fenestration

Extension into Subperiosteal Space

FSE T2

medullary space

periosteum

cortex

2-year old 15-year old

T1 + Gd T1 + Gd

FSE T2

T1 + Gd

FSE T2

T1

FSEIR

Persistent Fat Signal

• In bone, subperiosteal space

• Increased intramedullary pressure leads to septic necrosis, lipocyte death, release of free fatty globules

• Acellular marrow spaces

T1

Davies AM, Eur Radiol (2005). 15:2194

FSE T2

T1

Extension into the Soft Tissues

• In > 50% of osteomyelitis

• Particularly common in the pelvis

T1 + Gd

Pelvic Osteomyelitis

• Metaphyseal equivalents in >90%

• Soft tissue abnormalities in 80%

• Variable presentation depends on spread

T1 + Gd

FSE T2

B

B

FSE T2

FSE T2

T1 + Gd

T1 + Gd

• Patterns of epiphyseal-metaphyseal vascularity:

– Infant: communication

– Child/adolescent: physis is a relative barrier

– Adult: continuity

Extension into the Physis and Epiphysis

Infant

Infant Child

Infant Child Adolescent

FSE T2

Extension into the Physis and Epiphysis

• Frequent in neonates

• Abnormal signal intensity and lack of enhancement of cartilage

• “Chondro-osteomyelitis” or “chondritis”

FSE T2

Growth Cartilage Vascularity

Jaramillo D, et al. AJR 1996; 166:879-887

Arteriole, venule, capillary

plexus, and loose

connective tissue


Gd++


Gd++

Gd++


Gd++


Gd++

Gd++


Gd++

10-month old girl with foot pain

FSE T2 T1 + Gd

after treatment

T1 + Gd

T1 + Gd

Extension into a Joint

• Epiphyseal osteomyelitis

FSE T2

Extension into a Joint

• Intracapsular location of metaphysis

Complications of Osteomyelitis: Intraosseous/Chondral Abscess

• 10 - 25%

• Contrast-enhanced

–Enhancing rim

–Hypointense center

T1 + Gd

FSE T2 T1 + Gd

• Infection accounts for 10-15% of growth arrest

• Mechanisms:

– Direct destruction (metaphyseal focus)

– Ischemia (e.g. meningococcemia)

Complications of Osteomyelitis: Growth Arrest

Premature infant with Staph sepsis

2 years later

FSE T2 FSE PD

FSE T2

T1 + Gd

2 weeks later

FSE T2 T1 + Gd

1 year later

FSE T2

Considerations

3yo old boy whose dog ran into his foot now with pain and swelling

6 weeks later, cast off, unable to bear weight

FSE T2 T1 + Gd

three weeks after the fall

FSE T2 T1 + Gd

Ewing Sarcoma

FSE T2

T1 + Gd

FSE T2

T1 + Gd

Ewing Sarcoma

FSE T2

3 yo girl with swollen knee

FSE T2

Juvenile Idiopathic Arthritis

T1 + Gd

Right

FSEIR

Left

FSEIR

Pediatric Musculoskeletal Infections - PedRad.org

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