child with a limp

Question 1

what is acute haematogenous osteomyelitis

Answer 1

haematogenous spread of pathogens seeding into the bone
usually staph aureus

Question 2

what is septic arthritis

Answer 2

intra-articular infection of a synovial joint
may coexist with osteomyelitis

Question 3

what are the common causes of septic arthritis

Answer 3

staph aureus is the most common cause
GBS in neonates and Kingella Kingae in toddlers
Haemophilus influenzae in unimmunised
consider underlying illness and unimmunised (salmonella)

Question 4

discitis

Answer 4

inflammation/infection of an intervertebral disc, typically occuring in pre-school aged children and most often affecting the lumbar spine

Question 5

site of pain

Answer 5

most commonly hip or knee but could be any synovial joint
osteomyelitis: most commonly femur or tibia, pelvis and humerus but any long bone

Question 6

fever

Answer 6

may be absent in osteomyelitis
usually present in septic arthritis or pyogenic myositis
typically absent in discitis or transient synovitis or low grade

Question 7

onset of pain

Answer 7

osteomyelitis: subacute onset of limp, non-weight bearing or refusal to use limb
septic arthritis: acute onset of limp, non-weight bearing or refusal to use limb
pyogenic myositis: subacute onset, may involve limp
discitis: subacute onset of irritability and back pain. may involve limp or refusal to crawl or walk
transient synovitis: subacute or acute onset of limp, recent recovery from viral illness

Question 8

pain in osteomyelitis

Answer 8

poorly localised

Question 9

septic arthritis pain

Answer 9

hot, swollen, painful, immobile joint

Question 10

pyogenic myositis type pain

Answer 10

pain usually well localised
may have abdominal pain (psoas involvement)

Question 11

discitis type pain

Answer 11

refusal to bed forward, loss of lumbar lordosis, percussion tenderness over spine, hip pain, lower limb neurology, ileus

Question 12

transient synovitis type pain

Answer 12

weight bearing with limp

Question 13

systemic features

Answer 13

osteomyelitis: with or without systemic illness
septic arthritis: usually more severe systemic symptoms
pyogenic myositis: systemic symptoms usually more severe
discitis: irritable, with or without systemic illness
transient synovitis: systemically well, recent viral symptoms

Question 14

examination

Answer 14

look: resting limb position (hip flexed, abducted and externally rotated), swelling and erythema, open wounds or soft tissue infection
feel: tenderness, warmth, effusion
move: passively in all places of motion and actively

Question 15

DDx

Answer 15

transient synovitis
trauma including NAI
inflammatory conditions eg. inflammatory arthropathy, chronic recurrent multifocal osteomyelitis, acute rheumatic fever
pyogenic myositis
discitis
malignancy, including leukaemia
DDH in toddlers and children
perthes disease
SUFE

Question 16

investigations

Answer 16

not necessary if child is systemically well, afebrile and weight bearing without significant discomfort, working diagnosis and early follow up is sufficient

FBC, CRP, ESR, blood culture
x-ray
joint US

Question 17

when should blood cultures be taken

Answer 17

prior to antibiotics if possible

Question 18

FBC, ESR and CRP

Answer 18

may be normal
blood film if concern for malignancy
especially in early or chronic infection, or of infection of the small bones

Question 19

synovial fluid aspiration

Answer 19

where appropriate, in cases of suspected septic arthritis
should not delay antibiotic treatment

Question 20

x-ray

Answer 20

used to exlcude fracture and malignancy
usually normal up to 7-10 days in osteomyelitis

Question 21

ultrasound

Answer 21

to identify joint effusion in suspected septic arthritis
highly sensitive but not specific

Question 22

MRI with contrast

Answer 22

preferred test for osteomyelitis especially where symptoms are localised
may demonstrate sub periosteal abscess or marrow involvement
highly sensitive for myositis
use if still limping after 7 days

Question 23

technetium bone scan

Answer 23

may be useful where access to MRI is limited
a positive bone scan is not a specific finding
negative bone scan cannot rule out infection or other serious pathology

Question 24

treatment for septic arthritis

Answer 24

urgent aspiration +/- arthrotomy and washout
do not delay antibiotics

Question 25

antibiotic treatment

Answer 25

for uncomplicated cases of osteomyeltisi and septic arthritis commence
flucloxacillin IV every 6 hours
for children under 4 year commence
Cefazolin IV every 8 hours

Question 26

consider discharge when

Answer 26

child tolerating oral antibiotics or has planned outpatient IV therapy eg. hospital in the home
afebrile, well child
improved inflammatory markers and clinical indicators
weight bearing/using involved limb
safety netted

Question 27

red flags on history

Answer 27

> 7 days duration
severe localised pain
change to urinary or bowel habit
complete inability to walk or weight bear
nocturnal pain
systemic symptoms
consitutional symptoms

Question 28

red flags on examination

Answer 28

generalised wasting
fever
petechiae/purpura/ecchymosis

Question 29

pelvis AP or frog leg view x-ray

Answer 29

useful for identifying SUFE, DDH > 6 months, perthes disease and common pelvic avulsions

Question 30

child with a limp flowchart

Answer 30

Question 31

Kocher criteria

Answer 31

in a child with hip pain the presence of the following 4 crietria increases the liklihood of septic arthritis
- fever >38.5
- non-weight bearing
- leucocytosis >12
- ESR >40 or CRP >20

you should refer if 2 or above, 3 or above is very high probability of septic arthritis