chapter 17 - acute pyogenic bone and joint infections in children Flashcards
what is the current theory of osteomyelitis?
- the glycocalyx capsule of the staph aureus has chrondotropism or a selective tendency of adherence to the cartilage growth plate of the growing child
pathophysiology of acute osteomyelitis
- bacteria deposited during a bacteraemic episode into a metaphyseal vessel
- bacteria escape through endothelial gaps and adhere to the growth plate in the metaphyseal bone
- proliferating bacteria cause retrograde thrombosis of the nutrient artery
- abscesses form in the medulla and decompression of pus takes place via volkamnns and haversion canals to the subperiosteal space
which type of osteomyelitis exists in the neonate and infants (<1)?
presents with septic arthritis but primary pathology is osteomyelitis
name the type of vessel that exists in neonates and infants and connects the metaphysis with the epiphysis
transphyseal vessels
2 complications of osteomyelitis in the neonate and infant
- destruction of the epiphysis - eg: tom smith arthritis of the hip
- growth plate damage eg: coxa vara
in the child older than one - why does subperiosteal decompression take place?
the physis acts as a vascular barrier
in ostemyelitis in a child why would the inner half of the cortex die?
nutrient artery thrombosis
what is a sequestrum?
dead bone
what is the most common cause of septic arthritis?
haematogenous spread to synovium
what are two other causes of septic arthritis?
- intra articular metaphysis decompresses into a joint
2. transphyseal spread in neonate and infant
pathophysiology of septic arthritis
- bacteria and pus destroy cartilage = chondrolysis
- staphylokinase is a proteolytic enzyme and neutrophils release proteolytic enzymes that are chondrolytic
why should you wash out a joint with septic arthritis?
to wash out the chondrolytic and proteolytic enzymes
in septic arthritis - what is the complication of having pus in the hip joint?
- pus is chondrolytic
- avascular necrosis: pus stretches the retinacular vessels to the femoral head
how does a neonate or infant with ostemyelitis present clinically?
70% not ill, can drink well, apyrexial
what is the most common finding in an neonate or infant with osteomyelitis?
pseudoparalysis
how does the clinical presentation of osteomyelitis differ in an infant and child
child: frozen joint
infant: reasonable range of passive movement
which sites are commonly affected in a neonate or infant with osteomyelitis
proximal hip/femur 50%
proximal shoulder/humerus
distal knee/femur
what are the radiographic features found in a neonate or infant with acute osteomyelitis?
metaphyseal rarefaction
subluxation of the hip and shoulder
what are the commonest sites of osteomyelitis in a child(7 yo)?
distal femur
proximal and distal tibia
how does a child with osteomyeltiis typically present clinically?
bone pain and tenderness in metaphyseal area
ill, pyrexial
refuses to bear weight on leg
± swelling
what determines whether there is swelling present in a child with osteomyeltiis?
whether the pus has decompressed sub periosteally
how does septic arthirtis present in a child?
warm, painful swelling of the joint
palpable effusion
decreased range of movement
what do the radiographs look like in the acute phase of ostemyelitis in a child?
normal radiographs in the acute phase
in a child when does osteomyelitis become visible on radiograph?
after 2 weeks
what are the radiographic changes found in a child with osteomyelitis?
metaphyseal rarefaction
periosteal reaction
which laboratory test may be raised in a child with osteomyeltiis and what would the value be?
ESR > 50
what is the best investigation to differentiate between osteomyelitis, diffuse cellulitis and mysosits?
isotope bone scan with technetium methylene disphosphonate ( 99mm Tc - MDP)
how do patients with severe disseminated staphylococcal disease present clinically?
critically ill septicaemia metastatic staphylococcal pneumonia myocardial effusion bone or joint infection
which investigation is mandatory in patients with severe disseminated staphylococcal disease?
isotope bone scan
what is the usual causative organism of osteomyelitis in child hood?
staph aureus
what is the commonest causative organism of osteomyelitis in neonates ? and the 2nd and 3rd ?
- staphylococcus 72%
- streptococcus
- gram negative - E coli
30% of neonates with osteomyeltiis are resistant to X antibiotic? which neonates are more likely to be resistant?
cloxacillin
premature neonates - who have spent time in hosptial
what is the commonest organism in septic arthritis?
staph aureus 30%
True or false: In 50% of patients with clinical septic arthritis no organism can be identified
true
how is the diagnosis of osteomyelitis made? and which investigations are needed?
- a high index of suspicion and clinical diagnosis
- radiographs in neonates to rule out fracture or tumour
- FBC, ESR, blood culture
when do you admit a patient with osteomyeltiis?
if the diagnosis is obvious or if there is doubt
how do you manage a patient initially if you suspect osteomyelitis?
observation in the ward for 24 hours
±isotope bone scan to confirm diagnosis
first line treatment of acute bone and joint infection
antibiotics IV for 24 hours
antibiotic for all patients with osteomyeltiis and route ?
cloxacillin 200mg/kg/day IV
if a neonate has been hospitalised previously which additional drug to the antibiotics do you prescribe to treat osteomyelitis? and why?
fusidic acid 30mg/kg/day
for staph aureus
antibiotic to treat pt with septic arthritis aged 6m to 2 years and route? also what does this cover?
ampicillin 150mg/kg/day IV
haemophilus influenzae
oral treatment of osteomyelitis caused by staph aureus? and duration of treatment
flucloxacillin 100mg/kg/day for 6 weeks
oral treatment of septic arthritis and duration of treatment and which 2 drugs to use if there is no growth in the age group 6m to 2 yrs
- amoxil 75mg/kg/day for 3 weeks
2. cloxacillin + ampicillin
which surgery should always be performed in septic arthritis? and what role does it play? what does it do in the hip joint?
open arthrotomy and lavage of joint
- removes chondolytic effects of organisms and pus
- hip joint: capsular distension is decompressed and prevents avascular necrosis
if osteomyelitis presents early can it be treated without surgery?>
yes
which surgery is useful in patients with osteomyeltiis?
draining the subperiosteal pus
which 3 conditions are prevented if the pus is drained in a patient with osteomyelitis
patient improves clinically
- metastatic spread
- further periosteal stripping
- devascularisation of the cortical bone
what can be done to treat a patient with osteomyeltiis if no pus is found outside the bone?
3mm drill hole made without stripping periosteum
complication of osteomyeltiis
chronic osteomyeltiis
what is the cause of chronic osteomyelitis
presence of sequestrum
describe the two types of sequestrum found in a patient with chronic osteomyelitis
small: sinus that discharges pus intermittently
large: structural sequestrum with potential to fracture
3 complications of septic arthritis explained:
chondrolysis - destruction of articular cartilage
stiffness: decreased ROM due to peri and intra articular fibrosis
avascular necrosis
which joint is affected by avascular necrosis
hip joint
when is a patient with septic arthritis at increased risk of avascular necrosis?
if treatment is delayed by > 5 days incidence increases by > 50%
