Bone and Joint Infections Flashcards
What is osteomyelitis?
infection of a bone
What are the two means that bone can become infected?
hematogenous spread (spread via blood flow) and direct spread of bacteria from contaminated surrounding tissues
What are the features of hematogenous osteomyelitis?
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
What are the features of osteomyelitis caused by direct spread?
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
What types of nerves are damaged in diabetic neuropathy?
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
What is the Tx for diabetic neuropathy?
painful neuropathy - Neurontin; non-painful - no Tx available (can only be prevented by controlling blood sugar)
What is the most sensitive test for diabetic neuropathy?
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)
What are the most common sites of diabetic ulcers?
tops of toes, bottoms of toes, pad of foot, heel of foot
When should you start screening for diabetic neuropathy?
Type 1: 5 years after diagnosis
Type 2: at time of diagnosis (may be asymptomatic)
How does osteomyelitis present?
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)
What distinguishes osteomyelitis from cellulitis?
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)
What distinguishes osteomyelitis from septic arthritis?
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)
What is the best initial test for osteomyelitis?
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)
What is a diagnostic finding on x-ray for osteomyelitis?
loss of periosteum (normally appears as thick, bright white edge on bone) and periosteal elevation (long bones)
What is the best alternative scan if x-ray is negative but there is high clinical suspicion of osteomyelitis?
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)
What type of culture should be performed in a PT with osteomyelitis?
bone culture obtained via biopsy - once Dx of osteomyelitis is established, to determine etiological agent
When do you use contrast with an MRI?
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
What is the Tx for osteomyelitis?
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)
What is the best way to assess efficacy of Tx in osteomyelitis?
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)
What is septic arthritis?
infection of the synovium (most commonly occurs in the knee)
What causes septic arthritis?
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
What are the risk factors for septic arthritis?
degenerative or artificial joints
What are the most common pathogens in septic arthritis?
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)
What is the presentation of septic arthritis?
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
What is the best initial test for septic arthritis?
joint aspiration (synovial analysis to look at the number of WBCs); nuclear acid amplification test (NAAT) if suspect disseminated gonoccocal infection
What do the findings on WBCs suggest for Tx of septic arthritis?
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%)
What is the recommended Tx for septic arthritis?
=> 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”
