MSK Infections Flashcards
Which groups of patients are most prone to getting osteomyelitis?
Immunocompromised Chronic disease DM Elderly Young children
What is the pathophysiology of osteomyelitis?
Bacteria may infect directly due to trauma or surgery, or may spread haematological from another site
As bacteria multiply, local osteolysis occurs and pus develops –> impairs blood flow making it very difficult to treat
Dead fragment of bone can form (sequestrum) –> antibiotics alone will not cure infection at this stage
What is a Brodie’s abscess?
An abscess with a thin rim of sclerotic bone, can occur i children with subacute osteomyelitis
What is Pott’s disease?
Chronic osteomyelitis in the spine caused by TB –> spread from lungs
How is Pott’s disease diagnosed?
MRI spine
Which organisms may cause osteomyelitis?
Staph aureus Group A strep Group B strep (neonates) Enterobacter H. influenza in children P. aeruginosa (IVDU) Salmonella
Which group of patients get Salmonella osteomyelitis?
Sickle cell disease
What are the clinical features of acute osteomyelitis?
Severe pain (may be absent in diabetic foot)
- constant and worse at night
Low grade pyrexia
Tender, swelling, erythema
Which bloods should be done in acute osteomyelitis?
Routine + cultures
Which mode of imaging is definitive for osteomyelitis?
MRI
What is the role of xray in osteomyelitis?
Often done but has poor accuracy –> often appears normal until about 7-10 days
What is the gold standard investigation for osteomyelitis?
Culture from bone biopsy at debridement
What is the management for acute osteomyelitis?
Long term (>4 weeks) IV antibiotics If abscess --> drain If patient deteriorates or signs of progressive bone destruction --> debridement
What are the complications of acute osteomyelitis?
Overwhelming sepsis
Children may develop growth disturbance due to premature physeal closure
Recurrence of infection
May develop chronic osteomyelitis
What are the features of chronic osteomyelitis?
Localised ongoing bone pain + malaise/lethargy
May be a draining sinus tract
How may investigation findings differ in chronic osteomyelitis?
Blood tests may be normal
Culture may be negative
(cultures from sinus tract often contaminants)
What is the management for chronic osteomyelitis?
(antibiotics alone will not work)
–> surgical debridement + long term IV antibiotics
- complex staged reconstruction with internal/external fixation
- prolonged rehab
Amputation possible if patient not suitable for long rehab
How might a surgical implant/prosthesis become infected?
From patient or theatre staff’s skin (during surgery)
Post-op before wound healed
Late via the blood
What are the clinical features of an infected prosthesis?
Chronic infection Pain Poor function Recurrent sepsis Sinus formation Implant loosening
What are the consequences of infection of fracture stabilising materials?
Osteomyelitis
Non-union of fracture
Which organisms are most likely to cause an early prosthesis infection?
Staph aureus
Gram -ve bacilli e.g. coliforms
Which organisms are most likely to cause a late prosthesis infection (low grade, may take up to a year to be diagnosed)?
Staph epidermidis
Enterococcus
How is an infected surgical prosthesis managed?
Washout + revision surgery usually required
- may need to be left without a joint while antibiotics treat the infection
Then new prosthesis
What are the main causative organisms for septic arthritis?
Staph aureus (most common)
Streptococci
Gonorrhoea (sexually active)
Salmonella (sickle cell disease)
How might the joint be affected long term following septic arthritis?
Irreversible damage to cartilage
Severe, early OA
What are some risk factors for septic arthritis?
Age > 80 Pre-existing joint disease DM Immunosuppression CKD Joint prosthesis IVDU
What are the clinical features of septic arthritis?
Single, red, swollen, warm joint
Severely painful on active + passive movement
Pyrexia in 60%
Unable to weight bare
Symptoms often more subtle in a prosthetic joint
How should a suspected septic arthritis be investigated?
Bloods including FBC, CRP, ESR, urate + blood cultures
JOINT ASPIRATION is essential, ideally before antibiotics
Which tests need to be done on the joint aspirate which suspicious of septic arthritis?
gram stain, leukocyte count, polarising microscopy + culture
How is septic arthritis managed?
Manage sepsis
Antibiotics for at least 4-6 weeks (IV for 2)
Surgical irrigation + debridement (washout)
- can be done open or arthroscopic
- may need to be done several times
If prosthetic joint –> washout + revision surgery
