Bone and soft tissue infection Flashcards
what is osteomyelitis
this is infection of the bone
what is the difference between acute and chronic osteomyelitis
acute - develops from a recent injury or infection
chronic - the condition regularly returns
what group of people is most affected by acute OM
children (boys)
name some predispositions to acute OM
- diabetes
- immunocompromised
- long term steroid use
- rheumatoid arthritis
what is the most common cause of acute OM
haematogenous spread of infection to the bones
in new borns, what is the most common cause of acute OM
infection of the umbilical cord
if acute OM occurs in adults, what are the likely sources of infection
UTI or arterial lines
what are the causative agents of acute OM
- staph aureus
- E. coli (babies)
- strep pyogenes
- mycobacterium tuberculosis
- salmonella (those with sickle cell)
- usually a mixed infection in those with diabetes (may need to alter the empirical formula)
where in the bone does acute OM begin
at the metaphysics of the bone
what is meant by sequestration
necrosis of the bone as a result of OM
what is meant by involucrum
this is the formation of a new layer of bone outside existing bone seen in OM
what are the clinical features of acute OM
- failure to thrive
- metaphysical tenderness and swelling
- decreased range of movement or reluctancy to move
- not weight bearing
- fever and tachycardia
- toxaemia (blood poisoning)
- history of source of infection (e.g. UTI)
what is secondary acute OM
this is more common in adults and arises as a result of an open fracture or surgery (especially ORIF - open reduction and internal fixation procedures)
name some investigations you should carry out in acute OM
- FBC + WCC
- ESR and CRP
- x-ray (usually normal in the first 2 weeks but afterwards you may see metaphysical destruction)
- U+Es
- white cell scan
- isotope bone scan
- MRI
what is the differential diagnosis of acute OM
- acute septic arthritis
- trauma
- acute inflammatory arthritis
- sickle cell crisis
- transient synovitis
- soft tissue infection (cellulitis, necrosing fascitis, toxic shock syndrome, gas gangrene
what is the cause of gas gangrene
clostridium perfingens
when are x-rays useful in the diagnosis of acute OM
after 2 weeks
name some things that can be done to determine the microbiological cause of acute OM
- blood cultures
- bone biopsy
- tissue swabs
what is the treatment of acute OM
1) supportive - pain relief and rehydration therapy
2) antibiotics (IV for the first 7-10 days) - should be take for 4-6 weeks (depending on ESR)
3) rest and splitage
what is the empirical antibiotic formula for the treatment of acute OM
Fluclox and benzoyl penicillin
what are the complications of acute OM
- chronic osteomyelitis
- septic arthritis
- septicaemia
- altered bone growth
- pathological fracture
what is subacute OM
this is a milder version of acute OM - there is absence of systemic symptoms, more vague symptoms which causes a delay in the diagnosis
in someone with subacute OM, what may you find on clinical examination
local tenderness - there may be warmth, redness or swelling over the affected area (there is unlikely to be any systemic symptoms such as nausea, vomiting or fatigue)
why would some people get subacute OM rather than acute OM
the development of subacute OM rather than acute OM is thought to be the result of a greater host defence, a weaker infective agent or recent antibiotic use
what must be ruled out in subacute OM and how is this done
you must rule out malignancy and this is done with the use of imaging and bone biopsy
name some complications of subacute osteomyelitis
chronic osteomyelitis and growth disturbances
what is the differential diagnosis of subacute osteomyelitis
wings sarcoma, TB and osteoid osteoma
what is meant by Brodie’s abscess
this is a form of subacute osteomyelitis and it typically presents in children in the metaphysical region of the proximal or distal tibia
what is the most common microbiological cause of Brodie’s abscess
staph aureus
what investigations would be useful in Brodie’s abscess
X-ray, bone scan, bone biopsy
what is the treatment of Brodie’s abscess
prolonged antibiotics and curettage surgery if the epiphyseal is involved, if there is no improvement despite treatment or for recurring cases
what is the cause of chronic osteomyelitis
chronic OM can arise from acute OM or can arise from surgery or an open#
name some predisposing factors of chronic OM
- diabetes
- immunosuppression
- drug abuse
name the likely causative organisms in chronic OM
- staph aureus
- E. coli
- strep pyogenes
what is the treatment of chronic OM
- eradication of infected bone via surgery
- long term antibiotic treatment (local and systemic antibiotics)
- treatment of soft tissue problems/complications
- amputation
complications of chronic OM
- ongoing infection
- pathological fracture
- growth disturbance
- deformity
- squamous cell carcinoma
what is acute septic arthritis
this is the acute inflammation of a joint caused by bacterial infection
what is the cause of acute septic arthritis
can be caused by direct invasion (e.g. penetrating injuries or open#), haematogenous spread or an infection from another site or the eruption of a bone abscess
what organisms cause acute septic arthritis
staph aureaus, E. coli, strep pyogenes and H. influenzae
describe the pathology of acute septic arthritis
the articular cartilage in the joint is destroyed by the bacterial toxins and the enzymes
what are the signs and symptoms of acute septic arthritis
- resistant to move - not necessarily weight bearing because any movement will be painful
- ill and irritable
- tender joint
- fever and tachycardia
investigations that should be carried out in suspected acute septic arthritis
- FBC and WBC
- ESR and CRP
- blood cultures
- USS
- aspiration and culture
- X-ray
what is the most common cause of septic arthritis in adults
infected joint replacements
what is the differential diagnosis of acute septic arthritis
- acute osteomyelitis
- trauma
- rheumatic fever
- gout
- irritable joint
what is the treatment of acute septic arthritis
- general supportive treatments
- antibiotics for 3-4 weeks
- surgical drainage
what are the clinical features of a TB joint infection
- pain (especially at night)
- contact with others with TB
- low grade fever
- decreased range of movement
- sweating
- weight loss
- joint swelling
- ankylosis (fusion of bones over a joint causing stiffness)
usually only one joint will be affected and there will be marked muscle wasting
what investigations should you do if you suspected a TB joint infection
- FBC + ESR
- Mantoux test
- urine culture
- joint aspiration and biopsy
what is the treatment of TB joint infections
- rest and splint age
- chemotherapy - rifampicin, ethambutol and isoniazid for 8 weeks followed by rifampicin and isoniazid for 6-12 months
