Infection Flashcards
transient synovitis septic arthritis acute/subacute/chronic osteomyelits puncture wound infections
What is transient synovitis of the hip?
- Hip pain due to inflammation of the synovium of the hip
- most common cause of hip pain in paeds population
- most common in aged 4-8 years
- male : female 2:1
Describe the risk factors of transient synovitis of the hip?
- Cause of transient synovitis of the hip is unknown
- however related to
- trauma
- bacterial or viral infection ( poststreptococcal toxic synovitis)
- higher interferon concentration
- allergic reaction
What is the pathoanatomy of transient synovitis of the hip?
- Non specific inflammation and hypertrophy of the synovial lining/membrane
What is the prognosis of transient synovitis of the hip?
- Natural hx of disease
- usually benign
- marked improvements usually in 24-48hrs
- complete resolution of symptoms will usually occur in <1 week
What are the key questions to ask in hx?
- Site of pain
- groin vs hip ( referred)
- Timing ( intermittent vs constant)
- Lack of mechanical symptoms ( locking/catchng giving way)
- Assoc limp
- constitutional symptoms
- recent infection/trauma
What are the signs /symptoms of transient synovitis of the hip?
Symptoms
- Mild/ absent fever
- Acute/ insidiuos onset of groin/thigh pain
- pain is worse on awaking
- refusal to wb on affected extremity
- usually improves during the day ( can walk w a limp later in day)
- muscle spasms
Signs
- hip in Flexion, Abduction, and External rotation ( position of least amount of intracapsular pressure)
- child usually doesn’t have toxic appearance
- mild to moderate restriction of hip abduction= most senstive rom restriction
What is seen on xray in transient synovitis of the hip?
- AP , Lateral and frog lateral
- usually normal appearance
- may show medial joint space widening
What do uss in transient synovitis of the hip show?
- Accurate for detecting intracapsular fluid/effusion
- may show synovial membrane thickening
- difficult to distinguish transient synovitis from septic arthritis
Is MRI useful in transient synovitis of the hip?
- Yes it can distinguish transient synovitis of the hip from septic arthritis
- BUT a GA is required
- so not first line investigation
What are the labs values seen in transient synovitis of the hip?
- WBC maybe slightly elevated
- CRP >20mg/l is the dtrongest independent risk factor for Septic arthritis
- ESR is usually < 20mm/h
What are Kocher’s criteria?
- Criteria for septic arthritis
- 3 out of 4 =93% chance of SA
- Fever >38.5oC
- WBC >12,000mm3
- NWB on affected limb
- ESR >40mm/h
What are the most important factors to rule out Septic arthritis?
- Pt WB on limb
- CRP <20mg/L
What is the tx of transient synovitis of the hip?
Non operative
- for pt afebrile last 24hrs, mild symptoms
- improve ambulation
- Kocher’s criteria <2
- tx with IV/PO NSAIDS and Observe 24hrs
-
early wb with physio
- if improve w nsaids likely to be TS
- symtpoms resolve in <1 week
Surgery
-
Joint aspiration USS /II, then initation of IV antibiotics
- high suspicion of SA
- worsening hip pain
- Kocher’s score> 2
-
Irrigation and debridement of hip
- documented infection
- kocher criteria 4/4
- outcomes= tx is time sensitive
- prolonged infection will affect cartilage survival
What are the complications of transient synovitis of the hip?
- Legg- Calve - Perthes (1-3%)
- Coxa Magna
- Hip dysplasia
What is hip septic arthritis?
- A surgical emergency that requires prompt recognition & tx
- Peaks first few years of life
- 50% cases occur in children < 2years
- hip joint involved in 35% of all cases of SA
What are the risk factors of hip septic arthritis?
- Prematurity
- Cesarian section
What is the pathophysiology of hip septic arthritis?
- Direct inoculation from trauma or surgery
- Haematogenous seeding
-
Extension from adjacent bone
- can develop from contiguous spread of osteomyelitis
- often from metaphysis
- common in neonates who have transphyseal vessela that allow spread into the joint
What joints in children have intra-articular metaphyses
what is the relevance of this?
- Hip
- shoulder
- elbow
- ankle
- NOT THE KNEE
- septic arthritis may occur secondary to direct intra-articualar spread from metaphyseal osteomyleitis
What is the mechanism of destruction in hip septic arthritis?
- Release of proteolytic enzymes ( matrix metalloproteinases) from inflammatory and synovial cells, cartilage, & bacteria which may cause articular surface damage within 8 hours
- increase joint pressure may cause femoral head osteonecrosis if not relieved promptly
What are the signs and symptoms of hip Septic arthritis??
Symptoms
- Presents more acutely than osteomyelitis
- often assoc with fever
- toxic shock appearance
- children refused to walk / move hip
Signs
- Localised swelling
- effusion, warmth, tenderness
- hip rests in ABDUCTION, FLEXION & EXT ROTATION
- hip capsular vol is maximised in this position
- ROM
- severe pain with passive motion
- unwillingness to move joint ( pseudoparalysis)
- examine adjacent joints- to rule out other invovlement
What is seen on imaging in a pt with hip Septic arthritis?
Xrays
- Ap, lateral , frog lateral
- normal
- widening of joint space, subluxation/dislocation/ lateral displacement of femoral head
USS
- Maybe helpful to identify effusion
- can guide aspiration
What criteria are the best predictors of SA?
- Fever >38.5oC
- CRP >2.0 mg/dl
- then ESR/ refusal to WB, & serum WBC
- from Caird ‘s level 1 evidence paper JBJS am 2006
What are the complications of hip Septic arthritis?
-
Femoral head destruction
- complete destruction of femoral head,neck easily visible on xray- see pic
- salvage operations including varus/valgus proximal femoral osteotomies
- Deformity
- physeal damage -> late angular deformity & LLD
- Joint destruction
- Hip dislocation
- Growth disturbance
- Gait abnormalities
- osteonecrosis
What is epidemiology of osteomyelitis in children?
- incidence 1 in 5000 children
- 50% cases in pts < 5years
- 2.5 x more common in boys
- more common in 1st decade of life due to rich metaphyseal blood supply and immature immune system
- not uncommon in healthy children
- typically Metaphyseal via Haematogenous seeding
What is an involucrum?
- A layer of new bone growth outside exisiting bone seen in osteomeylitis
Define a sequestrum?
- Necrotic bone which has become walled off from its blood supply & can present as a nidus for chronic osteomyelitis
What is seen on radiographs with osteomyelitis?
- Early films maybe normal or show loss of soft tissue planes & soft tissue oedema
- new periosteal bone formation (5-7 days)
- osteolysis (10-14 days)
- Late fims 1-2 wks - metaphyseal rarefraction (reduction in metaphyseal bone density) or possible abscess
What other imaging is helpful in osteomyelitis?
MRI
- T1 signal Decreased
- T1 with gadolinium signal Increased- see pic
- T2 signal increased
- 88%-100% sensitivity
Bone scan
- non diagnostic xray
- localised pathology of infant/toddler with non focal exam
- tech- 99m can localised the focus of infection & show multifocal infection
- 92% sensitivity
- cold bone scan- assoc w more aggressive infections
Bone aspiration
- for definitive DX
- 50%-85% affected pts have positive cultures
What lab results will you see in osteomyelitis?
-
WBC
- elevated in 25% pts
- correlated poorly w tx response
-
CRP
- elevated in 98% pts
- elevated within 6 hours
- most sensitive to monitor therapeutic repsonse
- Declines rapidly with successful early tx
-
ESR
- elevated in 90% pts
- rises rapidly and peaks 3-5 days but declines too slowly to guide tx
-
Blood Culture
- only positive in only 30-50% of time
- Plasma Procalcitonin
- new serological test rises rapidly with bacterial infections
- elevated 58% pts with paediatrtic om
What is the most common organism in this injury?
- Pseudomonas aeruginosa
- gram negative rod
- most common organismm from a nail puncture thru a sneaker
- different organisms more common in diabetic and immunocompromised pts
