Week 3 Bone and Joint Infections

Question 1

Describe infectious (septic) arthritis and the pathophysiology.

Answer 1

• infection involving joint space, usually is monoarticular
• organisms commonly enter via bloodstream (also direct, spread from contiguous site)
• organisms enter joint space, adhere to articular cartilage, neutrophils enter joint space and synovial membrane, damage to cartilage due to pressure, bacterial toxins, leukocyte proteases and inflammatory cytokines
• leads to cartilage destruction, joint space narrowing, further erosive damage to cartilage, possible extension to bone and soft tissue

Question 2

What are common organisms causing infectious arthritis?

Answer 2

1. Staph aureas most common, then streptococcus (S. pyogenes)
2. less common: E coli, N. gonorrhea, H. influenzae uncommon now due to HiB vaccine
   also less common: TB, borrelia burgdorferi, Treponema, Brucella
3. children: S. aureus, S pyogenes, Kingella kingae
4. Infants: Group B strep, Gram neg bacilli, Staph aureus
5. cat bite: pasteurella
6. virus: parvo

Question 3

What are the clinical symptoms of septic arthritis?

Answer 3

1. Hx-predisposing factors
2. fever and chills
3. PAINFUL, SWOLLEN, RED joint with limited motion
4. Joint effusion

Question 4

How do you diagnose septic arthritis?

Answer 4

1. clinical symptoms
2. Imaging studies
   - x ray: possible early findings are soft tissue swelling, later findings: joint narrowing
   - MRI good for determining bone involvement and soft tissue abscesses
3. Lab exams: blood
   - elevated C reactive protein
   - elevated wbc, positive blood cultures, elevated ESR
4. Lab exams: synovial fluid analysis
   - thick and cloudy, usually over 50,000/mm3 of abc, with more PMNs
   - gram stain not always positive, culture is more sensitive

Question 5

How do you treat septic arthritis?

Answer 5

1. Debridement
2. Antimicrobial
   - systemic: 3rd gen cephalosporin+vancomycin
   - Duration: 2-4 weeks but no good data to prove
   - DON’T need local antibiotics directly into joints

Question 6

What are some complications of septic arthritis?

Answer 6

• cartilage destruction
• pain and loss of function
• degenerative arthritis
• avascular necrosis of femoral head
• subluxation and dislocation
• recurrent infections

Question 7

Define osteomyelitis and how it is classified.

Answer 7

1. Infection of the bone
2. heterogenous in pathophysiology, presentation, and management
3. Classification based on anatomical location
   -Type I : medullary
   -Type II: superficial
   -Type III: localized
   -Type IV: diffuse
   Also classified based on host-normal, compromised, or no surgical tx indicated

Question 8

What are common organisms causing osteomyelitis?

Answer 8

• depends on etiology butt S. aureus is most common

- almost any bacterium has been found

Question 9

Describe pediatric osteomyelitis.

Answer 9

• hematogenous is most common
• pathophysiology: bacterial seeding through nutrient or metaphyseal vessels and localizes in venous sinusoids of metaphysis
• prefers metaphyses

Question 10

What are the treatment and principles of infected ununited fractures?

Answer 10

1. Infection control
   -most important: remove all necrotic bone and soft tissue
   -culture to determine. Antibiotic therapy via systemic treatment and/or local antibiotics
2. Fracture stabilization
3. Soft tissue coverage
   -importance: vascularity improves fracture healing, host defenses, and antibiotic transport. Can transfer muscle flaps
4. Bone grafting
   NOTE on antimicrobial tx: osteomyelitis is never cured, only controlled. Risk of recurrence.

Question 11

Describe vertebral osteomyelitis.

Answer 11

1. Most common sites of hematogenous osteomyelitis in adults
   - bacteremia, particularly from GU of men>50
   - injection drug use
2. Symptoms may be non specific
3. Diagnosis
   - radiographs of erosions of end plates of adjacent vertebral bodies
   - biopsy is confirmatory and help ID organism
4. Microbio
   - S. aureus is mot common
   - less so: enteric bacterial e.g. E coli, Pott’s disease from TB
5. Therapy
   - antimicrobial therapy 4-6 weeks

Question 12

What is Brodie’s Abscess?

Answer 12

• chronic localized bone abscess
• most commonly in distal tibia with single lesion, most patients are <25 years old
• may have acute or chronic presentation

Question 13

What is the association between osteomyelitis and sickle cell disease?

Answer 13

• SS increases risk for osteoarticular disease

- common organisms: S. aureus and Salmonella

Question 14

Infections of the sacroiliac joint.

Answer 14

• most commonly caused by S. aureus
• risk factors: catheters, IV drug abuse, endocarditis
• severe sacral and pelvic pain