Bone and Joint Infections

Question 1

What is osteomyelitis?

Answer 1

infection of a bone

Question 2

What are the two means that bone can become infected?

Answer 2

hematogenous spread (spread via blood flow) and direct spread of bacteria from contaminated surrounding tissues

Question 3

What are the features of hematogenous osteomyelitis?

Answer 3

bone infection spreads to the skin; most common risk factors are IV drug use, endocarditis, and age; usually the long bones or vertebrae are affected (due to their extensive blood supply); most commonly mono-microbial (Staph aureus); S and S include localized pain, fever and chills

Question 4

What are the features of osteomyelitis caused by direct spread?

Answer 4

skin infection spreads to bone; most common causes DM (due to increased glucose production and poor blood flow) and PAD; usually affects the bones in lower extremities; most commonly poly-microbial (Staph and stool); follows a chronic course; vague symptoms of localized bone pain or no pain due to severe neuropathy

Question 5

What types of nerves are damaged in diabetic neuropathy?

Answer 5

all types: (1) sensory - loss of pain/temperature sensation leads to painless ulcers and loss of vibration/proprioception leads to gait instability and falls; (2) motor - can lead to motor weakness; (3) autonomic - decrease or increase in deep tendon reflexes

Question 6

What is the Tx for diabetic neuropathy?

Answer 6

painful neuropathy - Neurontin; non-painful - no Tx available (can only be prevented by controlling blood sugar)

Question 7

What is the most sensitive test for diabetic neuropathy?

Answer 7

10 g monofilament test - should conduct at least 2 tests to check functioning of different types of nerves (e.g., monofilament and vibration sense with tuning fork)

Question 8

What are the most common sites of diabetic ulcers?

Answer 8

tops of toes, bottoms of toes, pad of foot, heel of foot

Question 9

When should you start screening for diabetic neuropathy?

Answer 9

Type 1: 5 years after diagnosis

Type 2: at time of diagnosis (may be asymptomatic)

Question 10

How does osteomyelitis present?

Answer 10

usually chronic (weeks-months: acute onset is very rare); hallmarks are deep bone pain (“boring pain”) and localized tenderness to the touch; poor wound healing; erythema; edema; malaise; myalgia; weight loss; chills and fever (only with hematogenous spread)

Question 11

What distinguishes osteomyelitis from cellulitis?

Answer 11

cellulitis is an acute infection of the skin; presents with all 4 signs of inflammation (redness, swelling/edema, warmth, and pain); onset is rapid (onset is insidious in osteomyelitis)

Question 12

What distinguishes osteomyelitis from septic arthritis?

Answer 12

septic arthritis affects the joints; hallmark is limited ROM (both active and passive) => ROM is normal with osteomyelitis; onset is rapid (onset is insidious in osteomyelitis)

Question 13

What is the best initial test for osteomyelitis?

Answer 13

x-ray - pain is in the bone => should be the 1st test (will be positive 2 weeks after infection - will be negative if done too early)

Question 14

What is a diagnostic finding on x-ray for osteomyelitis?

Answer 14

loss of periosteum (normally appears as thick, bright white edge on bone) and periosteal elevation (long bones)

Question 15

What is the best alternative scan if x-ray is negative but there is high clinical suspicion of osteomyelitis?

Answer 15

MRI with contrast (most effective test to detect early infection) - bone scan is an alternative if MRI is not possible (nuclear test - isotopes have affinity to osteoblasts/cells that build up the bone)

Question 16

What type of culture should be performed in a PT with osteomyelitis?

Answer 16

bone culture obtained via biopsy - once Dx of osteomyelitis is established, to determine etiological agent

Question 17

When do you use contrast with an MRI?

Answer 17

when you are looking for a tumor or infection => if you are only looking for a change in structure, you conduct an MRI without contrast

Question 18

What is the Tx for osteomyelitis?

Answer 18

delay Abx until culture results are available; empiric therapy should be broad spectrum (Vancomycin IV + Ciprofloxacin IV or Piperacillin/tazobactam IV); usually also requires surgical debridement (especially if not improving)

Question 19

What is the best way to assess efficacy of Tx in osteomyelitis?

Answer 19

follow erythrocyte sedimentation rate (ESR ) weekly - should return to normal by 6-12 weeks (follow for at least 4 to 6 weeks to check for improvement)

Question 20

What is septic arthritis?

Answer 20

infection of the synovium (most commonly occurs in the knee)

Question 21

What causes septic arthritis?

Answer 21

usually direct spread of bacteria from surrounding structures (osteomyelitis or skin infection) or contamination of a surgical site (joint replacement) => hematogenous spread is rare in adults

Question 22

What are the risk factors for septic arthritis?

Answer 22

degenerative or artificial joints

Question 23

What are the most common pathogens in septic arthritis?

Answer 23

Staph aureus and disseminated N gonorrhea (in young, sexually active adults - need to check urethra/cervix/oral mucosa/etc. to check for other sites of infection)

Question 24

What is the presentation of septic arthritis?

Answer 24

always acute onset (hours-days), rapidly increasing joint pain at rest and with motion (almost always one joint), all signs of inflammation (swelling, warmth, tenderness, erythema), limited ROM (especially passive ROM => hallmark), fever

Question 25

What is the best initial test for septic arthritis?

Answer 25

joint aspiration (synovial analysis to look at the number of WBCs); nuclear acid amplification test (NAAT) if suspect disseminated gonoccocal infection

Question 26

What do the findings on WBCs suggest for Tx of septic arthritis?

Answer 26

WBCs:
1-2,000 => normal
2,000-20,000 => inflammation w/out infection (gout)
20,000-50,000 => unclear but treat if high suspicion
> 50,000 => send for Gram stain and start Tx (especially if neutrophils > 80%)

Question 27

What is the recommended Tx for septic arthritis?

Answer 27

=> vancomycin IV - switch to PO 1st generation cephalosporin (Cephalexin/Keflex) if improvement (if Staph sensitive)
=> if gonoccocal infection: ceftriaxone (Rocephin) 2 g IV or IM - switch to 3rd general cephalosporin (Cefixime/Suprax) if improvement
=> should see improvement in 3-4 weeks
=> joint drainage and “wash out”