Osteomyelitis/Septic arthritis

Question 1

What is the pathophys of osteomyelitis

Answer 1

bone infection = acute inflammation = bone necrosis = sequestrum of devitalized bone = chronic inflammation = deposit of new bone encasing shell (involcrum) = subperiosteal abscess = +/- draining sinus

Question 2

How does osteomyelitis occur

Answer 2

Bacteria gets into the bone and trigger an acute response
PMN infiltrate and form a subperiosteal abscess, causing ischemic injury
Pus gets into vascular channels and impairs blood supply, causing increased intraosseous pressure
High intraosseous pressure causes a draining sinus
Blood supply is compromised causing separation of necrotic bone (Sequestra)
Surviving bone becomes osteoporotic
A new bone sheath forms (Involcrum) in response to sequestrum (tries to seal them)

Question 3

Key findings in osteomyelitis are

Answer 3

Gradual onset Sx over days to weeks (unless you have diabetes!)
Dull, unrelenting pain w/ or w/o movement
Subjective fever and chills
tenderness, warmth, erythema, soft tissue swelling, ROM and Fxn loss
draining sinus tract

Question 4

Commonly, what are the only areas that present with pain

Answer 4

Hip
Pelvis
Vertebrae

Question 5

Nonspecific findings in osteomyelitis are

Answer 5

increased ESR and CRP

Elevated WBC if acute, but likely normal if chronic osteomyelitis

Question 6

What other diagnostics should you preform for osteomyelitis

Answer 6

Radiographs
Blood cultures
Bone biopsy (not needed if getting cultures and XR and w/ Sx)
GOLD: Gandolinium MRI (most Sn and Sp)
Alternative: bone scan (sensitive but not Sp)

Question 7

Radiographs will show

Answer 7

Early: demineralization
Late: sequestra and involcrum

Question 8

Usually what is your order if someone presents with suspected osteomyelitis

Answer 8

Get ESR, CRP, cultures, and XR- if abn…
MRI*, or bone scan, CT, bone biopsy, or all- if abn…
IV antibiotics!

Question 9

What IV abx do you start with in osteomyelitis

Answer 9

Vancomycin + Fluoroquinolone (empiric)
MSSA: Naficillin
MRSA: Vancomycin
Pseudomonas/Gram neg (DM): Ciprofloxacin
-No improvement in 48-96 hours, need Surgical Debridement

Question 10

What are types of infectious arthritis

Answer 10

Non-gonococcal acute bacterial (septic)

Gonococcal

Question 11

What causes non-gonococcal Infectious arthritis

Answer 11

Hematogenous spread (MC) 
Staph aureus (MC), MRSA, GBS, E. coli, Pseudomonas

Question 12

RF for non-gonococcal infectious arthritis are

Answer 12

Immunosuppressed 
DM
Sickle cell anemia 
Prosthetic joint 
Hc of arthritis 
Trauma 
Bacteremia

Question 13

How does non-gonococcal present

Answer 13

Acute onset mono-articular inflammation (MC knee!)
Erythema, effusion, warmth, pain
Limited function
+/- fever or leukocytosis

Question 14

How do you diagnose Non-gonococcal

Answer 14

*Synovial fluid analysis (aspirate w/ 16g needle- wide bore)
Blood cultures (50% are +)
Imaging is not very helpful

Question 15

Synovial fluid of non-gonococcal will show

Answer 15

>50K WBC
>75% PMN on differential 
low Glucose (eat the glucose) 
Positive culture 
\+/- gram stain

Question 16

Polyarticular infectious arthritis is common in

Answer 16

> 60 y/o
concurrent RA
In knee, elbow, shoulder, and hip primarily
Way poorer prognosis than monoarticular

Question 17

Polyarticular infectious arthritis is commonly caused by

Answer 17

Staph and Strep

Blood cultures and synovial cultures common in most

Question 18

What is different about polyarticular non-gonococcal

Answer 18

Affects unusual joints: Sternoclavicular, Costochondral, Pubic Symphysis
Staph aureus is still MC, but next MC is Pseudomonas (gram -)

Question 19

How do you treat non-gonococcal

Answer 19

Joint aspiration and irrigation 
IV abx (don't wait on cultures): Vanc + Ceftriaxone (3rd gen) 
MSSA= Naficillin
MRSA: Vancomycin

Question 20

How can you confirm clearance of infection after IV abx in non-gonococcal

Answer 20

Serial synovial fluid analysis

Question 21

Gonococcal infectious arthritis is associated with

Answer 21

Neisseria gonorrhea infecting otherwise healthy people
Migratory arthritis if sexually active
W>M
More common during menses and pregnancy

Question 22

How does gonococcal typically present

Answer 22

Migratory, non-symmetric polyarthralgias of wrist, knee, ankle, and elbow 
usually 1-4 days 
Tenosynovitis 
Necrotic pustules on palms and soles 
Fever and GU Sx not common 
<50% develop purulent arthritis

Question 23

What labs should you get for Gonococcal

Answer 23

Synovial fluid analysis: elevated WBC. Gram stain + in 25%, culture + in 50%
Blood cultures: + in 4-70%
*Cultures of urethra, throat, cervix, and rectum (+ even w/o Sx)
Imaging is not helpful
CBC not usually helpful bc WBC high in < 30%

Question 24

How do you treat Gonococcal

Answer 24

Azithromycin 1g PO + Ceftriaxone (3rd gen)

After improvement in 24-48 hrs, need 7-14 d course of Ceftriaxone IM daily

Question 25

What is the MC location of osteomyelitis

Answer 25

Kids: Log bones
Adults: Vertebrae

Question 26

What are the 3 ways osteomyelitis can spread

Answer 26

Hematogenously 
Spread from hardware (artificial joint) 
Venous insufficiency (diabetic ulcer)