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Block 2 - MSK > Lecture 19 - Infection Of Bones And Joints > Flashcards

Lecture 19 - Infection Of Bones And Joints Flashcards

1
Q

Osteomyelitis

A

Infection of the bone

  • usually caused by pyogenic bacteria or mycobacteria
  • subclassified on the basis of duration, causative organism, anatomic location of infection and route
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2
Q

Typed of osteomyelitis

A
  • associated with open fractures
  • hematogenous long bone osteomyelitis
  • vertebral osteomyelitis
  • osteomyelitis associated with diabetes and peripheral vascualr disease
  • caused by unusual organism or in uncommon sites
  • post traumatic: 50%
  • vascular insufficiency : 30%
  • hematogenous seeding: 20%
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3
Q

Risk factors for osteomyelitis

A
  • anything that affects immune surveillance, metabolism and local vascularity
  • systemic: maluntrition, renal or hepatic failure, diabetes, hypoxia, immune disease, extremes of age,
  • Local: chronic lymphodema, major vessel compromise, small vessel disease, vasculitis, venous stasis, malignancy, scarring, fibrosis, neuropathy
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4
Q

Microbiology of osteomyelitis

A
  • common: staph aureus or coagulase negative staph
  • occasinally encoutneres: streptococci, enteroccoci, gram - bacteria, anaerobes
  • rarely encounteres: MB TB, non-TB MB, brucella, salmonella, dimorphic fungi, fungi
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5
Q

Osteomyelitis mechanism

A
  • bone resistant to bacterial colonization
  • disruption of bone integrity can introduce ingection
  • neutrophil migration -> oedema and inflammation
  • diagnostic delays can lead to progressive destruction of therapy not initiated promptly
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6
Q

OM symptoms

A
  • fever, chills, fatigue, localized pain, swelling, redness
  • prior trauma, surgery, antibiotic use
  • decreased ROM, deformity
  • focal tenderness
  • problems with weight bearing and normal function
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7
Q

OM investigation

A
  • ESR and CRP elevated
  • Elevated WCC in acute OM, not chronic
  • blood cultures to guide therapy
  • bone biopsy
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8
Q

OM Imaging: XRAy

A
  • XRAY: helpful first step especially in chronic OM

- periosteal elevation, bone irregularity, osteolysis, new bone formation

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9
Q

OM: nuclear imaging: technetium 99m bone scan

A
  • high sensitivity >85% but lesser specificity (54-87%)

- focal uptake which correlates with clinical signs suggestive of osteomyelitis

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10
Q

OM: CT SCANS

A
  • Reveal articular surface and bone changes earlier than X ray
  • changes more easily appreciated
  • more specific than bone scan
  • assess soft tissue involvement better
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11
Q

OM: MRI

A
  • detect bone marrow abnormalities
  • highest sensitivity/specificity in detection of osteomyelitis
  • able to detect earlier changes
  • typically decrease signal on T1-weighted images and increase signal on T2-weighted and STIR images
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12
Q

Hematogenous OM

A
  • most commonly S aureus or b-hem strep
  • enterobacteriaceae more common in elderly or immuno compromised
  • risk factors: intravascular source, immune compromised, old age, UTI…
  • in infants and children usually involves metaphysis
  • in adults, vertebra is most common location
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13
Q

Vertebral OM

A
  • elderly, IVDU
  • insidious or abrupt onset of severe focal, localised back pain - radiates and is unrelieved by analesics
  • neurologic deficits secondary to vertebral body collapse or epidural abcess
  • prolonged antibiotics and surgical excision
  • microbiology diagnosis crucial
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14
Q

Vertebral OM microbiology

A
  • staph aureus in >50%
  • enteric gram - bacteria, especially those that cause UTI (eg: E coli)
  • pseudomonas aeruginosa and candida
  • Groups B and G streptococci
  • consider TB, especially if symptoms last for more than 1 months
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15
Q

Vertebral OM suite

A
  • may follow spinal surgery or epidural catherer
  • involves intervertebral disc first
  • epidural abcess andparaplegia can occur
  • rapid diagnosis with MRI
  • blood cultures, CT guided biopsy and surgical specimens for culture before antibiotics
  • IV antibiotics for 4-6 weeks
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16
Q

Osteomyelitis associated with open frctures

A
  • fracture contaminated at time of accident
  • usually lower limb
  • organism: environmental/skin/commensal flora
  • hospital acquired
  • leads to infected non-union, often with surgically implanted devices
17
Q

Management of OM associated with open fractures

A
  • antibiotic prophylaxis at initial reduction and fixation prevents up to 50% infetion
  • initial management: aggressive debridement and irrigation, fixation of fracture and softt issue coverage, rotation flap graft
  • plastic surgery if blood supply is poor
  • prolonged antibiotics
  • amputation of limb in severe cases
18
Q

Vascular insuficiency: diabeted

A
  • poor peripheral vascular supply
  • poor healing capacity
  • minor trauma leads to ulcers that spread to bone
  • baseline peripheral neuropathy
  • typically polymicrobial: Staph, Strep, Enterococcus, Gram negative and anaerobic organisms
19
Q

Diabetic foot osteomyelitis management

A
  • early aggressive and frequent debridement
  • management of pressure areas and shoe care
  • deep cultures
  • IV antibiotics for 2-4 weeks
  • oral therapy can continue for up to 6 months
  • healing will not occur unless a good vascular supply is established
20
Q

Chronic osteomyelitis

A
  • persistent infection
  • mostly refractory to antimicrobial therapy
  • bone sclerosis and deformity
  • fibrosis, vascular thrombosis, bone necrosis -> inhibits antibiotic penetration
  • commonly at ends of long bone
  • often no constitutional symptoms or leucocytosis but CRP elevated
21
Q

Chronic osteomyelitis treatment

A
  • broad spectrum IV antibiotics aftr blood and or bone culture obtained
  • once organism identified, coverage is narrowed
  • 4-6 weeks antibiotics
  • surgical excision to remove necrotic tissue, restore blood flow, manage dead space
  • due to the avascularity of bone with chronic OM, radical resection or amputation is often necessary
22
Q

Tuberculous osteomyelitis

A
  • MB TB

-

23
Q

Septic arthritic sources

A
  • Bacterial
  • Viral: often multiple joints, generally does not lead to long term morbidity
  • TB and non-candida fungi: usually as chronic slowly progressive monoarticular arthritis
24
Q

Presenting symptoms of septic arthrits

A
  • pain, LOF over 1-2 weeks
  • decrease range of motion, swelling, redness, warmth
  • focal pain often only symptom of axial infection
  • fever variable
  • focal joint tenderness, inflammation, effusion
  • active and passive ROM limited
25
Q

Septic arthritis - microbiology

A
  • streptococci, S aureaus
  • GNR: P. Aeruginosa
  • unusual causes: Kingella, Brudcella, animal bites, flora, sexual exposure, tick bites
  • chronic bacteria
  • viral arthritic
26
Q

Septic arthritis: Staph aureus

A
  • multifocal
  • costo chondral
  • sternoclavicular

THINK ENDOCARDITIS

27
Q

N. Gonorrhea septic arthritis

A
  • disseminated in 0.5-3% of mucosal gonorrhea
  • two syndromes:
    1) arthritis
    2) Tenosynovitis, dermatitis and migratory polyarthralgia
28
Q

Septic arthritis - diagnosis

A
  • WCC count
  • Gram stain - poor sensitivity
  • culture aspirate
  • culture blood
  • Specific PCR
29
Q

Septic arthritis: treatment

A
  • washout aids treatment and anrtibiotic diffusion into joint
  • 4-6 weeks therapy
  • deally 2 weeks IV but depends on organism and antibiotics with good oral bioavailibility
  • children: little IV needed
30
Q

Prosthetic joint infection

A
  • PJI require arthroplasty, long hospitalisation and antibiotic courses
  • formation of biofilm
31
Q

Classification of prosthetic related infections

A
  • Early post op: 4 weeks - 24 months / CoNS, P.acnes, anaerobes, S. Aureus
  • Hematogenous >2 years/ b.streptococci, S aureus, GNB
32
Q

PJI - clinical presentation

A
  • Early soft tissue infection PJI and hematoma are difficult to differentiate
  • pain in 90% of cases
  • fever swelling and sinus drainage in less than 50%
  • S aureus and GpA Strep most common
33
Q

Treatment 4 choices

A

1) debridement with retention
2) Removal of implant - 1 stage exchange
3) Removal of implant - 2 stage exchange
4) removal of implant - no reimplantation

Block 2 - MSK (38 decks)

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