MSK Infections Flashcards
Define osteomyelitis.
Inflammation of the bone and medullary cavity.
Usually located in one of the long bones.
What is a contiguous infection?
located adjacent to where infections started
What is the medullary cavity?
the elongated region of the diaphysis, contains bone marrow.
What is the gold standard diagnostic test for osteomyelitis?
bone biopsy
In the treatment of osteomyelitis, do you await lab confirmation of antimicrobials, or start empirical treatment?
await anti-microbial results, antibiotics given for 6 weeks.
Which classification of infection would an open fracture be?
contiguous
What is a clinical clue of osteomyelitis due to an open fracture?
non-union and poor wound healing
What is the treatment of an infected open fracture?
early management key: aggressive debridement, fixation and soft tissue cover.
What are the likely organisms found in an open fracture osteomyelitis?
stap aureus and aerobic gram negative bacteria
What is diagnostic tool for diabetes/vascular insufficiency induced osteomyelitis?
probe to bone
what is the treatment for diabetic ulcer induced osteomyelitis?
acute & antibiotic naive -> fluclox 2g daily IV
acute & non-antibiotic naive -> vancomycin IV 15-20mg/l
Who gets haematogenous osteomyelitis?
prepubertal children
PWID
central lines/dialysis/elderly
Causative organisms in PWID haematogenous osteomyelitis?
staphlyococcus, streprococci
unusual pathogens - candida, pseudomonas, eikenella corrodes (needle lickers), mycobacterium tuberculosis.
What is the most common pathogen in a dialysis patient who acquired osteomyelitis?
staph aureus
What are some unusual sites of infection due to haematogenous spread?
osteitis pubis - urogynae procedures predispose to bacterial causes
clavicle osteo - risk factors are neck surgery and subclavian vein catheterisation
What are the pathogens found in sickle cell osteomyelitis?
salmonella and staph aureus
What is Gaucher’s disease?
a lysosomal storage disorder, may mimic a bone crisis, often affects the tibia.
sterile if bone crisis, staph aureus if infected.
SAPHO and CRMO, what are they and who gets them?
SAPHO - Synovitis, Acne, Pustulosis, Hyperostosis, Osteitis - Adults
CRMO - Chronic Recurrent Multifocal Osteomyelitis - Children
What are the most common sites involved in SAPHO/CRMO?
chest wall
pelvis
spine
lower limb
What is the typical number of active lesions seen per patient with SPAHO/CRMO?
5
Most likely classification of vertebral osteomyelitis?
haematogenous
Epidural abscess would be located where?
anterior to the spinal cord
What is the imaging used fo vertebral infection?
MRI or Ga-67 scan (FDG-PET)
clinical signs of vertebral osteomyelitis?
50% have fever
90% insidious pain and tenderness
90% raised inflammatory markers
15% neurological signs/symptoms
<50% raised WCC
32% abnormal plain film
treatment of vertebral osteomyelitis?
drainage of large para-vertebral/epidural abscesses
antimicrobials for 6 weeks
What are the clinical results you would expect to see upon treating vertebral osteo?
> 50% decrease in ESR
decrease in inflammatory markers and pain
What are the indications for repeated MRI post-treatment of vertebral osteo?
unexplained increase in inflammatory markers
increasing pain
new anatomically related signs/symptoms
What test should be offered to all adults who are diagnosed with skeletal tuberculosis?
HIV test
What is the pathophysiology of Pott’s disease?
Haematogenous spread of TB from e.g. the lungs to vertebrae.
Infection spreads from 2 adjacent vertebrae to intervertebral disc. If only one vertebra is affected, the disc will be normal, but if 2 are involved, the avascular disc cannot receive nutrients so collapses.
Caseous necrosis: disc tissue dies leading to vertebral narrowing and eventually vertebral collapse and spinal damage.
What needs to be checked in kids with skeletal TB?
check reduced receptors for IFN-gamma R1, IL-12 beta-1
what are the risk factors for prosthetic joint infection?
RA
diabetes
obesity
malnutrition
What are the potential mechanisms of prosthetic joint infection?
direct inoculation at time of surgery
manipulation of joint at time of surgery
seeding of joint at a later time
What are the timing differences of early vs. late joint infections?
early = within a month late = after one month
What are the 3 main symptoms of PVL producing Staph aureus infections?
- skin infections
- necrotising pneumonia
- invasive infections, e.g. bacteraemia, septic arthritis
What is the treatment of PVL producing staph aureus?
FLucloxacillin, clindamycin, linezolid
What are some of the diagnostic tests for prothetic joint infections?
culture - preoperative tissue (multiple) - if same organism grows from multiple samples, increases significance.
CRP - helps along with clinical history
radiology - might show joint loosening
What is the treatment for an infected prosthetic joint?
remove prosthesis and cement
antimicrobials for at least 6 weeks
re-implantation of joint after aggressive antibiotic therapy.
Which pathogen would be seen in an infected upper limb prostheses?
Propionibacterium acnes
What are the main pathogens in infected prostheses?
gram positives - staph aureus and sth epidermidis
Coagulase Negative Staphylococci is part of normal flora. In which circumstances could it cause an infection?
It has low virulence and can only cause infection if prosthetic material is present.
What is the most common member of coagulase negative staphylococci group?
staph epidermidis
What is the virulence factor of staph epidermidis?
slime
what is the initial antibiotic therapy of staph epidermidis?
vancomycin
What is the immediate treatment of septic arthritis? And which case is the exception and alternative?
FLUCLOXACILLIN (high doses)
< 5 y/o add Ceftriaxone (for H influenzas cover)
What is pyomyositis?
Bacterial infection of muscle caused by infalmmation.
Describe the pathogen in Tetanus.
Clostridium tetani
Gram +ve strictly anaerobic rods.
Spores - found in soil, gardens etc.
What is the incubation period of clostridium tetani?
4 days - several weeks.
Why does spastic paralysis occur in Tetanus?
It is a neurotoxin - binds to inhibitory neurones, preventing release of neurotransmitters. (ACh)
What is the classical shape of the terminal spore in clostridium tetani?
drumstick shaped
What is the treatment of tetanus?
surgical debridement antitoxin supportive measures antibiotics.... penicillin/metronidazole booster vaccination - toxoid
