Outline
• Age
• Incidence
• Etiology
• Pathophysiology
• Presentation
• Laboratory investigations
• Imaging
• Treatment
• Surgery
• Complications
• Summary
• Special Groups
Age / Incidence / Etiology
• 1/1000 – 1/ 20 000
• Male > Female
• Pre antibiotic era ……20-50% mortality
• Advances in treatment
– Earlier dx
– Antibiotic tx
– Surgery less delay
– Children better nourished
• Glasgow incidence decreased
• New Zealand……. Madri > Whites
• South Africa…….. Black > Whites
• Changing disease / Changing organism
• Seasonal Variation
• Nutritional status, climate, lifestyle
• H Flu
– Big cause 1970’s
– 1-4 yrs
– Now decreased due to vaccinations
– Kingella Kingae
– OM in older kids
– Septic Arthritis 1-3 yrs
– Neonates separate group
Pathophysiology
• Poorly defined
– Direct inoculation
– Hematogenous spread
– Local invasion
• Infection
– Starts in Metaphysis
• Arteriole Loop / Venous Lakes
– Spread via Volkman’s canal / Haversian system
– Endothelium Leaks
• Few phagocytes in Zone of Hypertrophy
– Highest incidence in fastest growing bone
– Tubular > Flat bones
• Gaps in endothelium metaphyseal vessel
• Bacteria pass
• Adhere to Type 1 collagen
• Increase pressure in bone/ decrease blood flow
• Bone infarction / Dead Bone (sequestrum)
• Spread via Volkman Canal
• Subperiosteal Pus
• Cortex breaks down
• May spread to joint
– Hip / Shoulder / Fibula / Proximal Humerus
• Role of Trauma
– Rabbit experiment
– IV injection of bacteria
– With # start in hematoma
• Role of growth plate
– Over 18/12
– Impermeable to spread
– Under 18/12 infection crosses growth plate
• 1st osteoblasts die
• Lymphocytes release osteoclast activating factor
• Hole in bone
Diagnosis
• Pain
– Neonate peudoparalysis
– NWB
– Failure to use limb
• Fever
• Lethargy
• Anorexia
• Swelling (neonates / older kids)
• Bloodwork
– CBC Diff
– ESR
– CRP
– Blood Culture
• WBC increased 30-40%
• Left Shift 65%
• ESR increased 91%……….24-36hrs
• CRP increased 97%…………4-6hrs
• CRP
– More rapid than ESR
– 2-4 hrs …..peak 72hrs
– 10-30x normal
– Systemic ds (trauma, tumor)
• Blood Culture
– + 30-60%
– Decreased with antibiotic
– Multiple cultures no significant increase in yield
– 48 hours to get most organisms
Diagnosis
• Pus aspiration
– 70% bone + cultures
– Septic arthritis
• Gram stain
• Lymphocyte count
• % polymorphs
– > 80 000 = Septic arthritis
– > 50 000 in some series
– 80 000 also in JRA
• Do blood and joint cultures
– One or other not always +ve in same pt
– Gram stain +ve 1/3 bone and joint aspirations
• Future looking for bacteria DNA / RNA
Lab Diagnosis
• WBC not reliable
– False sense of security
– 25% increased Mayo clinic
– 65% diff abnormal
• Acute phase reactants
– Change in plasma proteins d/t cytokines
• ESR
– Nonspecific acute phase reactant
– Depends on fibrinogen concentration
– Increased 48-72 hrs
– Increased in 90% of cases
– Not affected by antibiotic tx
• CRP
– Increased in 98% of cases
Radiology
• Plain xray
– Sensitivity 43-75%
– Specificity 75-83%
• Soft tissue swelling 48hrs
• Periosteal reaction 5-7d
• Osteolysis 10d to 2 wks
– (need 50% bone loss)
• Tc99
– 24-48hrs +ve
– Bone aspiration DOES NOT give false +ve
– Decreased uptake in early phase d/t increased pressure
– “cold” scan up to 100% PPV
• Gallium
– 48 hrs to do
– Non specific
• Indium
– I131 leucocytes
– 24hrs to prepare
• Monoclonal antibodies
– Not proven to be better
• MRI
– Sensitivity 83-100%
– Specificity 75-100%
– PPV = Tc99
• Marrow and soft tissue swelling
• Good in spine and pelvis
• T1
– Best for acute infection
– Gadolinium helps
– Changes similar to
• #
• Infarct
• Bruise
• Tumor
• Post surgical
• Sympathetic edema
• CT
– Gas
– sequestrum
Treatment
• Mostly medical
– Sx to improve local environment
– Remove infected devitalized bone
– Decompress abscess cavity
• Timing !!
– Early antibiotic before necrosis / pus then sx less likely to be needed
• Antibiotic treatment
– Parenteral / oral combinations
– Often empirical
– Serum level more important than route
• Follow WBC / ESR/ CRP
• Organism / sensitivity
• Treatment Failure
– High doses
– Poor oral absorption / compliance
– Inadequate monitoring of serum levels
– Delay in Sx
• Previously start IV
• Follow ESR to guide switch to oral
• Newer studies
• Follow CRP
– Shorter period of tx needed
– IV 5d / total 23 d tx
– Cephalosporin 150mg/kd/day
• Neonates
– No studies, little evidence
– CRP / ESR not reliable
– Oral absorption not reliable
– Therefore IV neonates
– Cloxacillin
• Longer treatment required
– Pelvis
– Vertebrae
– Diskitis
– Calcaneus
• Surgical intervention
– Controversial indications
– Hole in bone not always Sx
– If purulent aspirate Sx necessary
• Sx less frequent with newer antibiotic
– 22-83% earlier studies
– 8-43% recent studies
• Surgery Indicated
– Subperiosteal Abscess
– Soft Tissue abscess
– Bone Abscess
– Failure of clinical response to antibiotic
– Associated septic arthritis
Complications
• Infection Complications
– Recurrence
– Chronic osteo
– Pathologic fracture
– Growth plate injury
• Antibiotic Complications
– Diarrhea
– N+V
– Rash
– Thrombocytopenia
– Neutropenia
Dr. Robert Deane
Janeway
