Bone, Joint, and Muscle Infection - Cross

Question 1

Septic arthritis definition?

Answer 1

Typically refers to bacterial infection in a joint.

Question 2

Septic Arthritis main route of infection? Others?

Answer 2

Usually hematogenously acquired

Other routes: Direct inoculation of bacteria into joint through surgery, trauma; contiguous spread from adjacent infected soft tissue or bone

Question 3

Most common bug in “Step on a Nail” septic arthritis

Answer 3

Pseudomonas Aeruginosa

Question 4

Most common bug in “Bit by my dog/cat” septic arthritis

Answer 4

Pasteurella Multocida

Question 5

Most common bug in sickle cell septic arthritis

Answer 5

Salmonella

Question 6

Pseudomonas Aeruginosa seen in these patients with septic arthritis?

Answer 6

IVDU (IV Drug Use), iatrogenic septic joint post surgical procedure/injection

Question 7

Most common bug causing septic arthritis?

Answer 7

Staph aureus

Question 8

Most important risk factor in septic arthritis?

Answer 8

preexisting abnormal joint architecture (i.e. RA, osteoarthritis, gout)

Question 9

Risk factors for septic arthritis?

Answer 9

Abnormal joint architecture (most important), RA, osteoarthritis, gout, advanced age, diabetes, IVDU, immunosuppression, endocarditis

Question 10

2nd most frequent cause of septic arthritis?

Answer 10

Strep; GAS, GCS, GGS

Question 11

Neonate has septic arthritis. What bug? This bug causes septic arthritis in what other patients?

Answer 11

Group B strep, also in diabetics, those with malignances

Question 12

Sacroiliac joint arthritis. Bug? Source?

Answer 12

Brucella from unpasteurized milk. Super rare. Dr. Cross hasn’t seen it.

Question 13

Sternoclavicular septic arthritis or clavicular osteomyelitis. Most likely in what patients?

Answer 13

IV drug users

Question 14

RA patients most likely to get septic arthritis from what bug?

Answer 14

Staph aureus

Question 15

Most common joint affected in septic arthritis?

Answer 15

The knee ( around 50%), mono-articular in 80-90% of cases

Question 16

Most common joint affected in septic arthritis in children?

Answer 16

The hip

Question 17

What bug causes gas gangrene?

Answer 17

Clostridium perfringens

Question 18

Typical clinical presentation of a patient with septic arthritis

Answer 18

Intense pain and loss of function of that joint over 1-2 weeks; swelling, erythema, and increased joint warmth

Question 19

What is characteristic of children with a septic hip?

Answer 19

they hold the hip in a flexed and externally rotated position, resist all ROM

Question 20

Dx of septic arthritis requires what?

Answer 20

arthrocentesis of affected joint

Question 21

Arthrocentesis facts

> how many cells usually required to make dx?

What type of cells are most abundant?

> how many cells pretty much is a dead giveaway for septic arthritis

Blood culture usually +?

Answer 21

> 50,000 usually septic

mostly neutrophils

> 100,000 = “you can pretty much bet this is a septic joint”

Blood cultures not often +

Question 22

Most important thing to look for when aspirating a joint that is suspected to be septic?

Answer 22

The presence of crystals, if crystals are present then it’s gout, not septic arthritis

Question 23

Nonspecific lab findings seen in septic arthritis

Answer 23

Leukocytosis, elevated ESR and/or CRP

Question 24

Early X-ray findings in septic arthritis

Answer 24

periarticular soft tissue swelling, nml osseous structures

Question 25

Late X-ray findings in septic arthritis

Answer 25

Joint space loss, bony erosion/destruction

Question 26

Ultrasound of septic joint is useful for what?

Answer 26

assess for presence of effusion and to guide needle aspiration if needed

Question 27

Who are you going to immediately call if pt has septic arthritis?

Answer 27

Future drew aka ortho to come for drainage +/- irrigation and debridement

Question 28

What bug causes a migrating arthritis

Answer 28

Gonococcus

Question 29

Presentation of gonococcal arthrits

Answer 29

Triad of dermatitis (this is key), tenosynovitis, and migratory polyarthralgia

Question 30

Epidemiology of Gonococcal arthritis. List a few

Answer 30

**4x more common in women**; \<40 years old, lower socioeconomic status, **multiple sex partners, illicit drug use**

Question 31

Pathogenesis of Gonococcal arthritis

Answer 31

Results due to occult bacteremia; infection could have been contracted days to months prior to dissemination

Question 32

Risk factors for gonococcal arthritis?

Answer 32

Women during menstruation, pregnancy, or postpartum; complement deficiencies (C5-C8)

Question 33

General outcome of blood cultures

Answer 33

around 25% are positive; don't be fooled by negative blood cultures

Question 34

Joints that gonococcal arthritis normally affects

Answer 34

Knees, wrists, ankles

Question 35

What is this? What disease is this associated with? Early or late in progression of disease?

Answer 35

Erythema migrans aka Bullseye rash = Early Infection Stage 1 Lyme disease

Question 36

Common bug that causes lyme disease?

Answer 36

*Borrelia burgdorferi*

Question 37

Lyme disease common where (geography)?

Answer 37

Common in northern states; NOT common in TN or Missouri. - Hey lets go picket in front of the Infectious disease convention. Theyll start listening to us then.

Question 38

Stages of Lyme disease?

Answer 38

Stage 1 (early infection): erythema migrans; classic "bullet" rash Stage 2 (early infection): Secondary skin lesions similar to initial lesions, but smaller; malar rash and conjunctivitis **Stage 3 (Persistent infection)**: intermittent attacks of joint swelling, **especially large joints like the knee**; even in untreated patients persistent arthritis normally resolves completely over several years

Question 39

Test used to diagnose Lyme disease

Answer 39

Lyme western blot test

Question 40

Alpha toxin associated with what bug? Main effect?

Answer 40

clostridium perfringens, causes hemolysis leading to anemia

Question 41

Gas gangrene in a patient causes what?

Answer 41

myonecrosis, necrotizing fasciitis

Question 42

Leukocyte threshold for diagnosis of prosthetic joint infection

Answer 42

Threshold is much lower for leukocytosis in the synovial fluid when compared to a nml joint; prosthetic joints don't have the amount of vascular access for inflammatory cells

Question 43

Treatment for prosthetic joint infection

Answer 43

REMOVE THE PROSTHESIS; prolonged abx therapy

Question 44

Conjunctivitis, palsies, and meningitis are associated with what disease?

Answer 44

Early Infection Stage II of Lyme Disease Features: include secondary skin lesions similar to initial lesions, but smaller; malar rash and conjunctivitis - heart and nervous system including palsies and meningitis

Question 45

Pt has abscess on spine, whats your likely dx?

Answer 45

Pott's disease (MTB osteomyelitis of spine)

Question 46

Likely source and route leading to Pott's Disease

Answer 46

TB of lung spread hematogenously to spine

Question 47

What bug causes double zone of hemolysis on blood agar?

Answer 47

clostridium perfringens

Question 48

Osteomyelitis due to candida infection seen in what patients? Other bugs common to this subset of patients?

Answer 48

IV drug users. Staph aureus, pseudomonas, candida, and serratia

Question 49

Causes of viral arthritis?

Answer 49

Rubella, Parvo B19, HCV, HBV

Question 50

Characteristic course of viral arthritis?

Answer 50

short duration, most resolve spontaneously; small joints of the hands most commonly affected

Question 51

How is the inflammation caused in viral arthritis

Answer 51

Immune complex formation; deposition in the joints causes inflammation

Question 52

Most common causes of osteomyelitis

Answer 52

Common (\>50% of cases) = Staph aureus, coag - staph (S. epidermidis, etc) Less common (\>25% of cases) = streptococci, enterococci, gram - (pseudo in someone stepped on a nail), anaerobes, MTB

Question 53

Pathogenesis of staph aureus causing osteomyelitis?

Answer 53

Expresses high affinity adhesions to components of bone matrix that express fibronectin, laminin, collagen, etc - it was bolded in her notes.

Question 54

Presentation of osteomyelitis

Answer 54

Nonspecific pain around the involved site with absence of systemic signs/symptoms

Question 55

In osteomyelitis, what usually alerts you to the source?

Answer 55

Location, location, location

Question 56

Osteomyelitis as a result of hematogenous seeding in adults is usually what type?

Answer 56

vertebral osteomyelitis

Question 57

Hematogenous long bone osteomyelitis: mono or polymicrobial?

Answer 57

monobacterial

Question 58

Contiguous infection osteomyelitis: mono or polymicrobial?

Answer 58

polymicrobial

Question 59

Foot osteomyelitis in diabetics is usually due to what route of infection?

Answer 59

result of contiguous spread

Question 60

Foot osteomyelitis after nail puncture usually due to what route of infection?

Answer 60

Result of direct inoculation

Question 61

Long bones of the lower extremity are the most common location of infection in what subset of patients with osteomyelitis?

Answer 61

Acute hematogenous osteomyelitis in children, obviously a result of hematogenous seeding

Question 62

Patient comes in with neck/back pain symptoms. What is an important question to ask?

Answer 62

Have you had recent injections in your back/neck. Rare but could be vertebral osteomyelitis due to iatrogenic cause (like injecting a long ass needle in someones neck)

Question 63

Complement deficiency risk factor for what? What complements specifically?

Answer 63

gonococcal arthritis, C5-C8