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Flashcards in 4/7 Osteomyelitis Deck (58)
1

By what routes can organisms enter bone and cause osteomyelitis?

Organisms enter bone by the hematogenous route

or by inoculation from a contiguous focus of infection

or by a penetrating wound

2

what will enhance a patient's susceptibility to infection?

-Trauma

-ischemia

-foreign bodies

(expose sites to which bacteria can bind)

3

what happens to bone if untreated infection becomes chronic?

Ischemic necrosis of bone 

-> separation of large devascularized bone fragments (sequestra -- E)

4

What happens when pus breaks through the bone's cortex?

Subperiostial abscesses form, and the periosteum deposits new bone (involucrum --C) around the sequestrum

5

How can bacteria escape host defenses?

-Adhering to damaged bone

-entering and living in osteoblasts

-coating themselves with biofilm

6

65 yo woman presents with ulcer on sole of her foot, below the first MTP joint. Diabetic neuropathy. Unsure how long the ulcer has been there. What is best dx test for osteomyelitis?

-PE, vitals, pressure around the ulcer

-blood cultures, pus from ulcer

-labs: CBC, ESR, CRP

-MRI of the foot

-plain films of the foot for bony erosion or periosteal elevation.

65 yo woman presents with ulcer on sole of her good, below the first MTP joint. Diabetic neuropathy. Unsure how long the ulcer has been there. What is best dx test for osteomyelitis?

-PE, vitals, pressure around the ulcer

-blood cultures, pus from ulcer

-labs: CBC, ESR, CRP

-MRI of the foot

-plain films of the foot for bony erosion or periosteal elevation.

7

What is seen on pathology of acute osteomyelitis?

organisms

neutrophils

congested or thrombosed blood vessels

8

What is seen on pathology of chronic osteomyelitis?

Necrotic bone (no living osteocytes)

mononuclear cells

granulation

fibrous tissue

9

Contiguous focus infections and those due to vascular insufficiency: most common in what age group?

Over 50y

10

Contiguous focus infections and those due to vascular insufficiency: what are some precipitating factors?

Surgical interventions, orthopedic surgery (e.g., knee, hip replacements)

–History of diabetes mellitus or peripheral vascular disease

Trauma, including open fractures

-also bedsores (decubitus ulcers)

11

A hematogenous infection usually involves what pattern of bones?

What is usually the source of the bacteremia?

Usually involves a single bone only

Source of bacteremia is not often apparent, may be hx of blunt trauma leading to intraosseus hematoma or vascular obstruction.

12

5yo at ER w leg pain. One week ago she fell off bike, & was subsequently fine. A few days later she started crying w walking. Now: temp 39, other vitals normal. Leg is painful, swollen over thigh. Hx notable for otitis media, for which she has received many courses of abx, most recently cephalexin, one month ago.

Lab results: WBCs 17000, plain film of the leg is normal. You order BCs and start abx while waiting for add’l testing. What antibiotics do you use?

-IV vancomycin to cover S aureus and strep 

-IV ceftriaxone to cover S aureus, strep, and  H inf.

-IV ampicillin plus gentamicin to cover streptococci, pneumococcus and E Coli

-Oral ciprofloxacin to cover staph, strep, E coli, Pasteurella multocida

-Oral cephalexin to cover S aureus and streptococci

5yo at ER w leg pain. One week ago she fell off bike, & was subsequently fine. A few days later she started crying w walking. Now: temp 39, other vitals normal. Leg is painful, swollen over thigh. Hx notable for otitis media, for which she has received many courses of abx, most recently cephalexin, one month ago.

Lab results: WBCs 17000, plain film of the leg is normal. You order BCs and start abx while waiting for add’l testing. What antibiotics do you use?

-IV vancomycin to cover S aureus and strep (because she has been on a lot of abx, and may by this point be colonized by MRSA. Has had selection pressure from her prior abx)

-IV ceftriaxone to cover S aureus, strep, and  H inf. (only covers MSSA, not MRSA)

-IV ampicillin plus gentamicin to cover streptococci, pneumococcus and E Coli (E coli not a cause of osteomyelitis in a 5 yr old)

-Oral ciprofloxacin to cover staph, strep, E coli, Pasteurella multocida (cannot give cipro to a 5 yr old)

-Oral cephalexin to cover S aureus and streptococci

**generally do not use oral abx to treat osteomyelitis

13

75 yo man at ED w back pain. Has been feeling unwell for weeks, w poor appetite, occasional sweats and fatigue, but no fever. Comes in now because pain is worse over the past day, and his legs feel weak. Hx notable for diverticulitis and prostatic hypertrophy, which requires intermittent self-catheterization. Retired dairy farmer, served in Vietnam in 1967.

Most urgent concern is:

-degen joint disease and spinal stenosis, for which you prescribe anti-inflammatory agents and arrange for PT

-Recurrent diverticulitis, for which you order an abdominal CT

-UTI, including pyelonephritis, for which you order UA, urine culture, and IV pyelogram

-Spinal TB, for which you do a PPD, get plain films of the spine, order a CXR 

-vertebral osteomyelitis complicated by epidural abscess, for which you order an MRI of the spine 

75 yo man at ED w back pain. Has been feeling unwell for weeks, w poor appetite, occasional sweats and fatigue, but no fever. Comes in now because pain is worse over the past day, and his legs feel weak. Hx notable for diverticulitis and prostatic hypertrophy, which requires intermittent self-catheterization. Retired dairy farmer, served in Vietnam in 1967.

Most urgent concern is:

-degen joint disease and spinal stenosis, for which you prescribe anti-inflammatory agents and arrange for PT

-Recurrent diverticulitis, for which you order an abdominal CT

-UTI, including pyelonephritis, for which you order UA, urine culture, and IV pyelogram

-Spinal TB, for which you do a PPD, get plain films of the spine, order a CXR (possible esp since he served overseas)

-vertebral osteomyelitis complicated by epidural abscess, for which you order an MRI of the spine (key think you worry about is epidural abscess encroacning on the spinal cord and causeing paralysis – legs feel weak -> might be the start of a cord problem.)

14

Are most cases of osteomyelitis Contiguous or Hematogenous in origin?

80% are contiguous (includes cases secondary to vascular insufficiency)

other 20% is hematogenous

15

What is the origin of the infection for osteomyelitis via contiguous focus?

what are predisposing factors for this type of osteomyelitis?

Origin: punctures, bites, surgical procedures, trauma

Predisposing factors: compound/open fractures, PVD, diabetes, orthopedic surgery

16

what are the common sites of infection for osteomyelitis via contiguous focus?

what is the typical patient population?

sites: feet (esp in diabetics), hands, tibia, femur

Patients: adults, esp w diabetes

17

what is the origin of the infection for hematogenous osteomyelitis?

what are predisposing factors?

infection originates from bloodstream

predisposing factors: bacteremia, endocarditis, sickle cell diseae, prior bone damage

18

what are the typical sites of infection for someone with hematogenous osteomyelitis?

what is the typical patient population?

Patients are Children, Elderly, or IVDUs

Sites for children: tibia, femur

Elderly and IVDUs: vertebrae

19

hematogenous osteomyelitis: where does it tend to locate within bones of children?

bacteria tend to settle in well-perfused metaphysis - especially in growing bones where they are sequestered and nourished.

20

Why does hematogenous osteomyelitis often to go the vertebrae of elderly and IVDUs?

Due to damage to their spines

These patients will have prior/current back pain.

21

Hematogenous infection: usually caused by a single pathogen, or multiple pathogens?

what is the most common pathogen?

what do we want to be sure to cover for?

caused by a single pathogen 95% of the time

caused by S aureus 50% of the time

so make sure to cover for MRSA (Ceftaroline, Vanco, Daptomycin, Linezolid, TMP/SMX -check this list!)

22

Hematogenous osteomyelitis:

constitutional s/s?

local s/s?

Constitutional: fever, chills, malaise, irritability, indolence (esp in adults)

Local: restricted movement, difficulty walking or bearing wt, local pain, tenderness, edema, erythema, warmth, induration

23

Vertebral osteomyelitis: type of contiguous or hematogenous osteomyelitis?

hematogenous.

24

Vertebral osteomyelitis: what arteries carry the bacteria to this location?

what part of the spine is usually affected?

what is a great substrate for infection?

-Organisms reach vertebrae via spinal arteries

-usually involves the lumbar or thoracic spine

-damaged bone is great substrate for infection

25

Microbiology of Vertebral osteomyelitis: is it usually a single pathogen or polymicrobial?

what is most common?

always want to cover for what?

Since this is a type of hematogenous infection, the microbio is the same:

caused by a single pathogen 95% of the time

caused by S aureus 50% of the time

so make sure to cover for MRSA (Ceftaroline, Vanco, Daptomycin, Linezolid, TMP/SMX -check this list!)

26

Vertebral osteomyelitis is caused by S aureus 50% of the time: wht other bugs cause this in these cases?

-men w bladder outlet obstruction/large prostates:

-pts with diverticulitis

-IVDUs:

-Sickle cell anemia:

-men w bladder outlet obstruction/large prostates: Enterococci

-pts with diverticulitis: E Coli, other enteric bacilli

-IVDUs: S aureus, Pseudomonas, Serratia

-Sickle cell anemia: Salmonella, S aureus

Also: Viridans strep (general)

27

Risk factors for Vertebral Osteomyelitis?


-Age > 50

-Sickle cell disease

-Diabetes mellitus

-Hemodialysis
-Endocarditis

-Injecting drug use

-Nosocomial bacteremia

-Long-term vascular access

-Urinary tract infection, esp. elderly men

-Preceding minor trauma or fall

 

28

Vertebral Osteo: what are s/s?

Patients will report a history of what?


-Presents as back or neck pain (>90%) 


-Patients may give history of having had fever and/or rigors weeks before presentation with back pain 


-Percussion tenderness of spine and paraspinal muscles, with spasm (85%) 


-Fever often low-grade or absent (50%) 


-Constitutional symptoms: anorexia, malaise 

-Often insidious in onset, then subacute or chronic

29

Vertebral Osteo: how to make the diagnosis?

-Plain films show irregular erosions in end plates of adjacent vertebral bodies and narrowing of intervening disk space – virtually diagnostic of infection


-Positive blood cultures (20-50%) 






-CT scan or MRI may show epidural, paraspinal, retropharyngeal, mediastinal, retroperitoneal, or psoas abscess originating in the spine.
 

30

Contiguous Focus Osteomyelitis: what are precipitating factors?

Occurs in pts 50+ due to these precipitating factors (generally involving falling apart due to old age):


-Surgical interventions, orthopedic surgery (e.g., knee, hip replacements) 




-History of diabetes mellitus or peripheral vascular disease 






-Trauma, including open fractures 








-Lesser trauma: stepping on nails, punctures, bites 










-Decubitus ulcers
 

31

What is generally the cause of contiguous focus osteomyelitis in patients with normal vascularity?

What are s/s in these patients?


Related to penetrating injuries (trauma)
 




Related to surgery


 






By direct extension from adjacent soft tissues




 








Signs/symptoms:






 


-Erythema, swelling
 




-Pain


 






-Impaired ROM




 








-Purulent sinus-tract drainage (often key to osteomyelitis)








 

 

 

32

What is generally the cause of contiguous focus osteomyelitis in patients with vascular insufficiency?

What are s/s in these patients?

-Usually involves the small bones of the feet (87%)

-Diabetic neuropathy exposes the foot to frequent trauma and pressure sores, and the patient may be unaware of infection as it spreads to bone.

-Poor tissue perfusion impairs normal inflammatory responses and wound healing, a milieu conducive to anaerobic infection.

Signs/symptoms:
Skin ulcer, possibly cellulitis

Infection usually localized to small bones of the foot

May be minimal pain, if associated with advanced neuropathy






 

 

 

33

What pathogens are associated with Continuous Focus Osteomyelitis?

What is the predominant pathogen?

Continuous focus osteo: 

30-50% are polymicrobial

S aureus is predominant (as with Hematogenous)

34

In continuous focus osteomyelitis, in what kinds of wounds/infections would we expect to see anaerobic pathogens?

(review: what are the anaerobic pathogens)?

Anaerobic pathogens seen in bites, dental/sinus infections, deep puncture wounds & peripheral vascular disease

Cat bites: suspect Pasturella multocida (aerobic, WTF)

Human bites: suspect Eikenella corrodens

Foot wound (classically a puncture through a sneaker): Pseudomonas (aerobic but can survive)

List of Anaerobic pathogens: Anaerobic strep (oral, GI), Bacteriodes, Fusobacterium, Prevotella, Actinomyces, Clostridia spp.

35

In continuous focus osteo, in what situations would we expect coag-neg staph?

Coag neg staph associated with infections of prostheses and other ortho hardware

(Coag-neg staph include S saprophyticus and S epidermidis: S. epidermidis = associated with ortho hardware & pacemakers, forms biofilms, is a skin commensal)

36

How and when to get a sample of suspected osteomyelitis for culture?

-Before starting abx

-Get deep cultures (swabbing a sinus tract or ulcer base won't give you the info you need)

-May need needle aspiration or biopsy.

37

How do the ESR and CRP levels help us in osteomyelitis?

How long should we continue antibiotics?

ESR and CRP are elevated in most cases of active infection, even if no constitutional sx and no leukocytosis.

-Establish baseline ESR & CRP when osteo is first dx.

-Follow CRP initially to see if treatment is working

-CRP should be normal within 2 weeks. If not, you may not be treating correctly.

-Treat for 4-6 w or until CRP is normal AND ESR is < 60% of baseline value.

38

Basics about ESR: why is it elevated with infection? 

how does it change over the course of infection?

ESR causes endothelial cell adhesion, spreading and proliferation -- essential for tissue repair.

Adhesion from ESR causes incr sed rate.

ESR is slow to rise, slow to fall.

39

Basics about CRP: why is it elevated with infection? 

how does it change over the course of infection?

CRP made by liver.

Component of innate immune response.

Reactive w short half life: rises and falls quickly with onset of infection and with treatment.

40

Role of plain films in imaging osteomyelitis?

Crude test, part of initial workup.

Won't see bone infection until at least 10d after onset.

Lytic changes only seen after 4-6w. 

Unlikely to see Vertebral Osteo.

May be difficult to distinguish osteomyelitis from neuropathic arthropathy.

41

Role of radionucleotide scans in imaging osteomyelitis?

(remove WBCs, label with tracer, re-inject and see where they distribute)

Expensive, cumbersome

Three phases; in osteo, all phases show increased WBC uptake

Can help distinguish between osteomyelitis and soft tissue infection in adjacent tissues

42

What's the best choice for imaging osteomyelitis?

What will it show?

MRI is best for all types (incl vertebral)

Even if osteo is seen on plain film, helpful to get an MRI: can see extent of infection and early involvement of adjacent bone.

Sens: 96%, specificity 87%

43

General principles of treating osteomyelitis?


-Obtain cultures before starting treatment! 


-Use bactericidal agents (rather than -static)

-Not many WBCs in bone; you are relying heavily on abx

-Start with parenteral therapy w high doses of antibiotics

-Base empirical therapy on findings of Gram staining, or choose agents to cover the most likely pathogens.

-Empiric coverage for S. aureus (until culture results are complete) is advisable in most cases.

 

 

44

If the osteo is found to be caused by Strep, what is the treatment?

PCN G

45

If the osteo is caused by S aureus (MSSA), tx is?

PCN allergic pt? 

nafcillin

if PCN allergic: cefazolin, ceftriaxone, (also ceftaroline but $$$), clindamycin

46

If osteo is caused by MRSA, treatment is?

Vanco.

Alternatives: Linezolid, Daptomycin

47

Tx for gram-neg bacilli?

ampicillin, cefazolin, ceftriaxone, or a quinolone, based on susceptibility results

48

Tx for pseudomonas?


-combination therapy with aminoglycoside plus a β-lactam or a quinolone 


-Resistant organism: hence requires combination of abx 

49

Special notes for treatment of contiguous osteomyelitis in pts with vascular insufficiency?

Think diabetics with foot problems

-Requires surgical debridement

-Effectiveness of surgery is limited by blood supply to the site and the body's ability to heal the wound

-Try to revascularize the limb before debridement if the vasc disease involves large arteries

-Prognosis is poor, even for acute osteo, if bone is not removed.

50

One slide on skeletal tuberculosis:

-most common site?

-what other s/s will be seen?

-suspect TB in what situations?

-what will be seen on histopath?


-Most commonly involves thoracic spine (direct extension of pulmonary TB through lymphatics)

-Usually accompanied by abnl chest x-ray, ie chronic fibrotic changes or nodules due to ongoing or prior TB

-Suspect TB on the basis of epidemiology (where a pt is from, likelihood of exposure), CXR, PPD or interferon-release assay

-Histopath shows necrotizing granulomas, but the infection is “paucibacillary” so stains may be neg (culture may take 6 weeks)

 

 

51

RR from FA:

Osteo pathogen to assume if no other info is available?

S aureus

52

RR from FA:

Osteo pathogen if patient is sexually active?

Neisseria gonorrhoeae (though uncommon cause of osteo; more likely to cause septic arthritis)

53

RR from FA:

Osteo pathogen if pt is diabetic or IVDU?

Pseudomonas, Serratia

54

RR from FA:

Osteo pathogen if pt has sickle cell?

Salmonella

55

RR from FA:

Osteo pathogen if patient has prosthetic replacement?

S aureus, S epidermidis

56

RR from FA:

Osteo pathogen if patient has vertebral disease (Pott's disease)?

Mycobacterium tuberculosis (TB)

57

RR from FA:

Osteo pathogen if patient has dog/cat bites or srcatches?

Pasturella multocida

58

RR from FA:

Most osteo occurs in what patients?

ESR and CRP are helpful or not?

Most osteomyelitis occurs in children (not sure SBM agrees)

Elevated CRP and ESR are classic but not specific