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
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%
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
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
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
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
7
Q
OM investigation
A
- ESR and CRP elevated
- Elevated WCC in acute OM, not chronic
- blood cultures to guide therapy
- bone biopsy
8
Q
OM Imaging: XRAy
A
- XRAY: helpful first step especially in chronic OM
- periosteal elevation, bone irregularity, osteolysis, new bone formation
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
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
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
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
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
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
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
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
