Bone and Joint infections Flashcards
How do we get osteomyletis?
- Haematogenous = from asymptomatic bacteraemia or septicemia
- Non-haematogenous = Direct inoculation (trauma/surgery) & Local invasion (pressure ulcer, peridontal disease, sinus disease)
What is the epidemiology of Osteomyelitis?
50% under 5 yrs, 25% under 1 year. B:G is 2:1 Increase risk = - Aboriginal/maori - Sickle cell - Neonates - Immunocompromised
What is the pathophysiology of Osteomyelitis?
- Slow flow through looped capillaries and venous sinusoids near metaphysis + micro capillary trauma - Bacteria seed the metaphyseal-epiphyseal junction - Abscess develops and is protected from the immune system due to poorly developed RE system - Pressure from pus limits blood supply - Infection spreads to sub-periosteal space and lifts periosteum. Shaft ca be infected du to this - By this stage microbes can spread to the whole bone
What is septic arthritis?
Infection due to direct or continuous contamination. Contiguous contamination is more common in children as they have vessels that traverse the diaphysis and epiphysis.
What is the most common cause of Osteomyelitis?
GPCs
S.Aureus >>> Strep pyo > step pneumoniae > GBS > coagulase -ve strep
GNs
HiB (common) = kingella kingae > salmonella >> other G-ves (enterobacter, psedomonas, E.Coli)
Other
TB, fungi, parasites
Why is S.aureus so common?
Huge array of VFs We all carry it 82% of bacteraemia pts in blood and nasal isolates contained the identical strain of S.aureus
What is the most common cause of osteomyelitis in babies/infants?
Group B strep (GBS), HiB, GNs (enterobacter, pseudomonas, e.coli)
Sneaker penetration injury = Pseudomonas
TB and HiB common in developing countries.
What are the clinical features of osteomyelitis?
Pain, pseudoparalysis, fever and malaise, limping Delayed presentation could be sub-periosteal collection (erythema, tenderness, swelling) 1/3 preceded trauma
Which bones are mostly involved ?
Long bones: humerus, femur, tibia Tubular bones are mmore implicated than flat bones
How is the presentaiton of osteomyelitis different in children?
Much the same symptos and areas.
Vertebral osteomyelitis may be missed as indolent course of over 3-4 months back pain
What are the differential diagnostics of Osteomyelitis?
Septic arthritis - Commonly coexistent
Malignancy - Rule out with FBE, X-Ray and a period of Rx
Cellulitis
What are the Dx for Osteomyelitis?
Clinical signs
- Fever
- Localised tenderness
- Erythema
- Oedema
Imaging evidence: X-Ray, Bone scan and MRI
Culture: +ve blood culture (in 30-50% of cases) or bone (50-70%). Pus aspirated from bone.
Blood: WCC often normal (but FBE and films are still essential)
CRP/ESR elevated in >90%
What is the timline of inflammatory markers for Osteomyelitis?
What imaging techniques can be used to diagnose Osteomyelitis?
X-Ray
Early on, efficacy questionably
Day 3 Can only see soft tissue swelling
Day 10-21 Used to exclude fracture and cancer
Day 28 Periosteal elevation nad lytic lesions can be seen
Bone scan
More sensitive Dc modality
Show increased area of blood flow, inflammation and OB activity
Specificity 70-95%
MRI
More difficult and expensive to do
100% sensitivity
What is the treatment for Osteomyelitis?
Flucoxacillin at high doses (IV/oral), ineffective against MRSA
Dicloxacillin if adult to take care of GPs
Cephalosporin if Neonate/Unimmunised
How to treat Pseudomonas infection?
Usually 3-5d IV of Timentin or gentamicin
How do you treat chronic osteomyelitis?
Often associated with suboptinal initial Rx
CRP/ESR unhelpful for Dc/monitoring
Surgical debridement + long term ABs needed
IV-2weeks oral 3-6 months
