1. Always a Diagnostic Puzzle
Osteomyelitis
Always a Diagnostic Puzzle
schreibman.info

2. Osteomyelitis: Put the Pieces Together
HISTORY
Clinical
Surgical
RADIOGRAPHS
Recent CT
Chronic
MRI
Active

3. Osteomyelitis: Put the Pieces Together
HISTORY
Clinical
Surgical
RADIOGRAPHS
Recent
MRI
Marrow
+Gd
Abscess

4. Osteomyelitis: Topics
Definitions
Active
Chronic
Mechanisms
Hematogenous
Direct spread
Imaging
Radiographs CT
MRI
Bone Model
Cortex
Marrow

5. Osteomyelitis: Definitions
comes from Greek:
osteon = bone
myelos = marrow
itis = inflammation
“Inflammation of bone marrow”
Infection of bone marrow
“Osteomyelitis”
High Sensitivity
Low Specificity
Marrow inflammation from infection looks like inflammation from any other cause
MRI
Marrow

6. Osteomyelitis: Definitions
Active Osteomyelitis vs
Chronic Osteomyelitis

7. Osteomyelitis: Definitions
Active Osteomyelitis
“Aggressive”
Resembles Tumor
Cortex Destruction
Periosteal Reaction

8. Active Osteomyelitis “Aggressive” Cortex Destruction
16yoM distal fibula pain 3w after inversion injury
“Aggressive”
Cortex Destruction
Periosteal Reaction
HISTORY
Clinical Followup

9. Osteomyelitis: Definitions
Chronic Osteomyelitis
“Non-Aggressive”
Resembles Callus
3 Characteristics:
Involucrum: “wrap”
Thick periosteum around infected bone
Sequestrum: “set apart”
Piece of dead, infected, bone
Cloaca: “sewer”
Opening in cortex through which pus can escape
RADIOGRAPHS
Active ≠ Chronic

10. Active vs Chronic Osteomyelitis
RADIOGRAPHS
Active ≠ Chronic
Active
Osteomyelitis
Chronic
Osteomyelitis

11. Active Osteomyelitis “Aggressive” Cortex Destruction
16yoM distal fibula pain 3w after inversion injury
“Aggressive”
Cortex Destruction
Periosteal Reaction
Active
Osteomyelitis

12. Chronic Osteomyelitis
19yoM fibula pain 2.5years later…
RADIOGRAPHS
Active ≠ Chronic
Chronic
Osteomyelitis
2.5 years

13. Chronic Osteomyelitis
19yoM fibula pain 2.5years later… CT
Tibia
Involucrum
Chronic
Osteomyelitis
Fibula
Sequestrum
Cloaca

14. Chronic Osteomyelitis
42yoM Diabetic
Involucrum Developing
6 weeks later
10 more weeks

15. Chronic Osteomyelitis
27yoM s/p removal
Rt Femoral Rod
27yoM s/p removal
Rt Femoral Rod
Involucrum
CT Scout

16. Chronic Osteomyelitis
27yoM s/p removal
Rt Femoral Rod
27yoM s/p removal
Rt Femoral Rod
Involucrum
Sequestrum
Axial Slice
CT Scout
Coronal Reformat

17. Chronic Osteomyelitis
27yoM s/p removal
Rt Femoral Rod
27yoM s/p removal
Rt Femoral Rod
Involucrum
Sequestrum
Cloaca
Axial Slice
CT Scout
Oblique Coronal

18. Osteomyelitis: Mechanisms
Direct Spread  adjacent tissues
Most common cause
Decubitus ulcer
Septic arthritis
PUS

19. Decubitus Ulcer  Ischium
52yoM
quadriplegic T1 
Ischium
Ischium  T1

20. Osteomyelitis: Mechanisms
Direct Spread  adjacent tissues
Most common cause
Decubitus ulcer
Septic arthritis
Puncture into bone
Stepped on nail
External fixator
Ring sequestrum

21. Chronic Osteomyelitis
Ring Sequestrum
Chronic Osteomyelitis
Involucrum
Sequestrum
Cloaca
Poor Union
RADIOGRAPHS

22. Osteomyelitis: Mechanisms
Direct Spread  adjacent tissues
Most common cause
Decubitus ulcer
Septic arthritis
Puncture into bone
Stepped on nail
External fixator
Ring sequestrum
Hematogenous
Site related to patient age

23. Hematogenous Osteomyelitis
Site related to patient age
Epiphysis
Physis
Metaphysis
Arteriole
Venule
Infection
occurs
at end of
Infection
occurs at
metaphysis of
Septic
Emboli
Diaphysis
Blood
Supply
Immature
Bone
Mature
Bone

24. Hematogenous Osteomyelitis
1yoM strep
pneumonia

25. Hematogenous Osteomyelitis
1yoM strep
pneumonia
3 months later

26. Osteomyelitis: Imaging
Many Imaging Options:
Radiographs CT MR US
Nuc Med
What to order when?

27. Osteomyelitis: What to Order When
Radiographs
………… ALWAYS!
May show evidence of active infection
Bone destruction, periosteal reaction
May show evidence of chronic infection
Involucrum
Screen for metal
Orthopedic hardware, foreign bodies
Unexpected findings
Fractures,
Delineate current anatomy
Surgical resections,
RADIOGRAPHS NEED TO BE RECENT vs
gas in soft tissues
neuropathic deformity

28. Need for Recent Radiographs
Example
66yoM h/o Diabetes
Presents in Sept swollen foot
MR is requested to “r/o Osteo”
Are there radiographs?
Yes
…3 months ago
Repeat radiographs obtained now, prior to MR, reveal…
Normal Lisfranc joint
Neuropathic destruction of the Lisfranc joint
June
September

29. Osteomyelitis: What to Order When
Radiographs ………… ALWAYS!
CT……………………. Chronic Cases
CT best for calcified structures
Involucrum
Sequestrum
Cloaca
CT of the extremities is insensitive for:
Bone marrow pathology
Soft tissue pathology

30. Osteomyelitis: What to Order When
Radiographs ………… ALWAYS!
CT……………………. Chronic Cases
MRI..…………………. Active Cases
Shows extent of soft tissue edema
Excellent for demonstrating abscesses
and other drainable fluid collections
Sensitive for bone marrow pathology
Can be overly sensitive
at expense of specificity
Infected bone marrow resembles marrow edema due to other causes

31. Osteomyelitis: MR Imaging
Bone Model
Marrow
Cortex T1 T2
X-rays

32. Osteomyelitis: MR Imaging
Bone Model
Marrow
Marrow
Marrow
Cortex
Cortex
Cortex
Surrounding
Tissues (fat)
Surrounding
Tissues (fat) T1 T2
X-rays

33. Osteomyelitis: MR Imaging
Bone Model
Marrow
Marrow
Marrow
Cortex
Cortex
Cortex
Surrounding
Tissues (fat)
Surrounding
Tissues (fat) T1
T2fs
X-rays

34. Osteomyelitis: MR Imaging 
Path=Fluid
T1=Dark
T2=Bright
T1fs+Gd
Enhancement
Inflamed
 Uniform
Abscess
 Wall
Cyst
 Not
(STIR) T1
T2fs

35. Osteomyelitis: MR Imaging  
Enhancement
Inflamed
 Uniform
Abscess
 Wall
Cyst
 Not
(STIR)
T1fs T1
T2fs
+Gd

36. Osteomyelitis: MR Imaging
Detection of the non-enhancing pus pocket (abscess) is crucial
Presence of soft tissue abscess proves the edema in underlying bone marrow is osteomyelitis.
Site for aspiration for culture.
If IV Gd doesn’t get into abscess,
IV antibiotics won’t get in either,
abscess may require drainage.

37. Osteomyelitis: MR Imaging
63yoM Diabetic
with heel ulcer
Intact cortex T1
Enhancing cellulitis
No non-enhancing abscess pocket
Minimal
Marrow
Edema
Figure 115: Developing calcaneal osteomyelitis in a 63 year-old diabetic patient.
a) Lateral radiograph of the calcaneus shows intact cortex along the plantar surface (white arrowheads).
Incidentally seen is mural calcification of the posterior tibial artery. Such arterial calcifications are common in diabetic patients.
b) Mid-sagittal T1 image shows no bone destruction.
c) Corresponding sagittal Inversion Recovery image shows little if any bone marrow edema.
d) Corresponding sagittal post IV contrast T1 fat-suppressed image reveals diffuse enhancement of the plantar soft tissues, indicative of cellulitis, but no non-enhancing abscess pockets.
Arterial Ca++
T1fs
IVGd IR

38. Osteomyelitis: MR Imaging
63yoM Diabetic
2 weeks later…
2 weeks earlier
Cortical destruction
Intact cortex
More marrow edema
More tissue edema
Non-enhancing abscess pocket
When the patient’s symptoms did not respond to antibiotics, repeat imaging was obtained 2 weeks later.
e) Lateral radiograph now demonstrates loss of cortex along the plantar surface of the calcaneus (black arrowheads).
f) Mid-sagittal T1 image reveals infiltration of the fatty heel pad (gray arrows).
g) Corresponding sagittal Inversion Recovery image reveals fluid bright signal (white arrows) within the soft tissues adjacent to the calcaneus, as well as bone marrow edema within calcaneus (white arrowheads).
h) Corresponding sagittal post IV contrast T1 fat-suppressed image reveals a non-enhancing abscess pocket (black arrows) as well as enhancing bone marrow (white arrowheads).
T1fs
IVGd IR

39. Osteomyelitis: MR Imaging
63yoM Diabetic
2 weeks later…   
2 weeks earlier
Cortical destruction
Intact cortex
Marrow edema
Abscess Pocket
Coronal T1 (i), Inversion Recovery (j) and post IV contrast T1 fat-suppressed (k) images through the abscess pocket confirm the findings seen in the sagittal plane: an abscess pocket (white and black arrows) adjacent to the osteomyelitis (white arrowheads) along the planter surface of the calcaneus.
T1fs
IVGd T1 IR

40. Decubitus Ulcer  Ischium
52yoM
quadriplegic
Abscess! 
T1fs
+Gd  T1
Abscess?  
T2fs

41. Osteomyelitis: MR Imaging
1yoF Swollen
left lower leg R L
Periosteal Reaction
Figure 116: Brodie’s abscess in a young child.
a) AP radiograph of the asymptomatic right leg.
b) AP radiograph of the swollen left leg reveals a lucency in the distal fibula metaphysis (white arrow in the magnified dashed box). This lucency has a well-defined and sclerotic margin, indicating chronicity. There are also thick, chronic, periosteal reactions (white arrowheads) extending up the diaphysis.
Metaphyseal
lucency

42. Osteomyelitis: MR Imaging
1yoF Swollen
left lower leg
Brodie Abscess
Periosteal Reaction
c) Coronal T1 image through the distal fibula confirms the radiographic findings of a thick chronic periosteal reaction (white arrowheads), as well as the well-circumscribed dark line (open arrowheads) around the lesion corresponding to the sclerotic margin.
d) The corresponding coronal T2 fat-suppressed image shows the well-circumscribed lesion (white arrow) is a bright as fluid and thus probably cystic.
e) The corresponding coronal T1 fat-suppressed post IV contrast image not only confirms the lesion (black arrow) is mostly non-enhancing and thus mostly cystic… but also demonstrates peripheral enhancement, in some places thick (black arrowhead), characteristic of an abscess, in this case an intra-osseous or “Brodie’s” abscess.
(There is inadequate fat-suppression of the heel pad (gray arrowheads) on both of the fat-suppressed sequences.)
Non-enhancing abscess
Intra-osseous
Metaphyseal
T1fs
IVGd T1
T2fs

43. Osteomyelitis: What to Order When
Radiographs ………… ALWAYS!
CT……………………. Chronic Cases
MRI..…………………. Active Cases
US……….…………… Fluid/Abscess
US guided aspiration for culture
Cannot assess bone involvement
Nuc Med.……………. Problem Cases
Where MR specificity is decreased
Neuropathic feet
Infected hardware

44. Infection around metal: MRI
T2fs
T1fs
IVGd
We can see soft tissues around bone
Enhancing granulation tissue (phlegmon?)
We can’t see the marrow within bone
Cannot evaluate for “osteomyelitis”
T,K 21yoM

45. Infection around metal: Nuc Med
Requires 2 Radiopharmaceuticals
Tc-Bone Scan (Active bone metabolism)
In-WBC Scan
(Areas of WBC accumulation)
1)BS: Sen/Spec
2)WBC:Spec/Sen

46. Infection around metal: Nuc Med
Femur
Plate
Tc-Bone Scan
In-WBC Scan
Removed
Tibia Plate
Femur
Femur
Tibia
Tibia
Placed
Antibiotic
PMM-Beads
Tibia
Plate
S,B 31yoM

47. Charcot (Neuropathic) Foot
T1fs
+IV Gd
T2fs
Abscess
Tc99m MDP
In111 WBC
Infection
P,K 65yoF

48. Osteomyelitis: Put the Pieces Together
HISTORY
Clinical
Surgical
RADIOGRAPHS
Recent
MRI
Marrow
+Gd
Abscess

49. Osteomyelitis: Put the Pieces Together
HISTORY
Clinical
Surgical
RADIOGRAPHS
Recent CT
Chronic
MRI
Active