MSK - Infection

Question 1

3 types of infection spread in OM

Answer 1

Hematogenous - most common in children
Continguous - most common in adults
Direct inoculation

Question 2

Imaging features of hematogenous OM

Answer 2

Infant - can cross growth plate - metaphysis + epiphysis

Child - just in metaphysis
Single org = Staph
Loose periosteum, leading to exuberant periostitis (lamellated, aggressive)
Ddx: Ewings, LCH, lymphoma

In adults - hematogenous OM - most common in spine

Question 3

Cause of contagious spread OM

Answer 3

Adults - often from diabetic ulcers

Polymicrobial (often need sample to direct tx)

Question 4

Which pt population does Salmonella infection occur in?

Answer 4

Sickle cell - propensity for diaphysis

DDx: infarct

Question 5

Methods of spread to spine

Answer 5

Hematogenous

• arterial
• venous through epidural Batson plexus

Question 6

Most specific AND sensitive tests for OM

Answer 6

WBC scan (Indium 111 WBC or Tc-99m-HMPAO-WBC) - positive in 24-48 hours
MRI - positive in 3-5 days

Question 7

Which pt population does Pseudomonas infection occur in?

Answer 7

IVDU

Question 8

Hematogenous seeding usually affects which joints?

Answer 8

S joints

• spine
• SI joints
• SC joints
• symphysis pubis
• shoulder (AC joint)