Bone and Joint Infection

Question 1

Septic Arthritis

1. 3 main causes

Answer 1

1. Bacterial (10% of pts presenting w/ acute pain)
2. Viral- acute, often multi-joint
3. Fungal- chronic, usually monoarticular

Question 2

Septic Arthritis

1. Mortality if untreated?
2. Morbidity?

Answer 2

1. 10-30%

2. up to 50% w/ permanent loss of function

Question 3

1. Who can get septic arthritis?

2. Risk Factors (8)

Answer 3

1. anyone
2. Age>80, prosthetic joint, recent joint surgery, IV drug use, endocarditis, immunosuppression/chronic disease, joint disease: RA, OA, Gout, skin infection/ulcer

Question 4

3 ways Septic Arthritis can occur

Answer 4

1. Hematogenous spread
2. Direct inoculation (via trauma or surgery)
3. Spread of infection from contiguous source (bone)

Question 5

Pathogenesis of Septic Arthritis

Answer 5

1. Synovial tissue that lines the joint space is normally leaky
2. Acute inflammatory response/ infiltrate
3. This causes synovial effusion and cartilage degradation

Question 6

Septic Arthritis: Presentation

1. Onset
2. Number of joints
3. Symptoms
4. Exam

Answer 6

1. hours-days
2. mono-articular
3. pain, swelling, warmth, loss of function, fevers (not if you’re immunosuppressed)
4. Tenderness, limited ROM/painful, effusion, redness

Question 7

Differential Diagnosis of Septic Arthritis (7)

Answer 7

1. Crystal induced disease
2. Rheumatoid Arthritis
3. Osteoarthritis
4. Systemic Lupus Erythematous (SLE)
5. Reiter’s and other reactive arthritides
6. Rheumatic Fever
7. Other Rheumatological disease

Question 8

Septic Arthritis: Bacterial Causes

1. What is it most often?
2. What could it also be?
3. When does 2 become more common?

Answer 8

1. Gram +: Staph (30-65%, esp aureus); Strep (20-25%)
2. Gram Negatives: E. Coli, H. flu, Neisseria, Pseudomonas
3. IV drug use, immunocompromised, elderly

Question 9

Septric Arthritis Diagnosis

1. What is the most important test?
2. What is seen early on X-ray?
3. Late?

Answer 9

1. Diagnostic Tap
2. Early: soft tissue swelling
3. Late: loss of joint space, erosive and destructive changes

Question 10

Synovial Fluid Analysis in Septic Arthritis

1. What increases the likelihood of septic arthritis?
2. What specifically increases the likelihood of septic arthritis?
3. If a patient has low PMNs? can you rule out septic arthritis?

Answer 10

1. higher synovial WBCs
2. PMN >90%
3. NO;

Question 11

Diagnosis of Septic Arthritis

1. How useful is the Gram Stain?
2. Culture?
3. Blood culture?

Answer 11

1. diagnostic in only 50%, but good bc rare false positives
2. 80-90% diagnostic; non-gonococcal arthritis
3. positive about 50% of the time

Question 12

Treatment of Septic Arthritis (2)

Answer 12

1. Drainage (daily aspirations, surgical drainage, more important with larger/prosthetic joints)
2. Empiric, then driven by clinical background

Question 13

3 Other common causes of infectious arthritis

Answer 13

Gonococcal arthritis
Lyme arthritis
Viral arthritis

Question 14

Gonococcal Arthritis

1. Who commonly gets it?
2. What is it a form of?

Answer 14

1. most common in sexually active individuals; usually under 30 y/o
2. disseminated gonococcal infection (DGI)

Question 15

DGI

1. how common is it?
2. which gender is more likely to get it?
3. What is it associated with?
4. Other risk factors?

Answer 15

1. 0.5-3% of gonococcal infections
2. women
3. menstruation/pregnancy
4. same as other STDs: more partners, IV drug use, lower SES

Question 16

DGI

1. what causes it?
2. Classic Triad
3. Other common symptoms

Answer 16

1. result of occult bacteremia
2. Dermatitis (numerous painless, non-pruritic macules, papules, pustular lesions)
3. Tenosynovitis (most common in hands, wrists, fingers, 2/3s of pts)
4. Migratory polyarthalgia or arthritis
5. Fevers, malaises

Question 17

DGI- Septic Joint

1. How common is it?
2. How many joints?
3. Which joints?

Answer 17

1. less common, can occur w/ or w/o DGI
2. usually monoarticular
3. knees, wrist, ankles

Question 18

Gonococcal arthritis- Diagnosis

1. What must be done?
2. Gram stain
3. Culture
4. What is the best method?

Answer 18

1. diagnostic tap
2. only 25% positive for G neg diplococci
3. only 50% positive
4. PCR, either of synovial fluid or from mucosal sites of original infection

Question 19

Osteomyelitis

1. Define
2. Is it acute or chronic?
3. Ways of getting it

Answer 19

1. inflammation of bone and marrow (infection)
2. Acute vs Chronic (considered chronic when sequelae are present)
3. Hematogenous vs Contiguous

Question 20

Osteomyelitis: Hematogenous spread

1. Who gets hematogenous spread?
2. Where?
3. What bacteria are found there?

Answer 20

1. children, growing bones
2. Vertebral bodies
3. monomicrobial

Question 21

Osteomyelitis: Contiguous Spread

1. What are some risk factors?
2. What bacteria are there?

Answer 21

1. DM, ischemic ulcers, decubitus ulcers, trauma/ surgery

2. Polymicrobial

Question 22

Osteomyelitis Presentation

1. Acute
2. Chronic
3. What 2 sites present as just pain in acute?

Answer 22

1. Gradual onset of symptoms over days-weeks; pain, erythema, swelling, tender, fevers/rigors,
2. pain, erythema, swelling, sinus tracts, large ulcers
3. hip, vertebrae

Question 23

Typical Osteomyelitis Pathogens

Answer 23

Staph
Strep
Enterococcus
Gram negative rods (pseudo, e coli, enterobacter)

Question 24

Diagnosis of Osteomyelitis

1. 3 imaging modalities?
2. Which is the best? why?
3. When is it not the best?
4. What are the 3 nuclear studies?

Answer 24

1. X-ray, MRI, CT
2. MRI- good sens and spec; good negative predictive value;
3. when hardware is present?
4. Triple phase bone scan, Gallium scan, WBC scan

Question 25

Osteomyelitis Diagnosis 1. What is a common easy test? 2. If it is positive in a DM foot ulcer, what futher testing is needed?

Answer 25

1. steel probe to bone test | 2. none

Question 26

Osteomyelitis Culture 1. How good is wound swab and deep wound cultures? 2. How good is percutaneous needle biopsy? 3. How good is a bone biopsy?

Answer 26

1. poor correlation w/ diagnosed organism 2. poor correlation w/ diagnosed organism 3. best method for specimen collection; yields positive cx 87% of the time