Flashcards in Bone and Soft Tissue Infections Deck (54)
In what forms can osteomyelitis occur?
-Acute vs chronic
-Specific (e.g. TB) vs non-specific (most common)
Who is usually affected by acute osteomyelitis?
-History of trauma (minor)
-Other disease: diabetes, rheumatoid arthritis, immune compromise, long term steroid treatment, sickle cell
What the infection in acute osteomyelitis spread?
-Haematogenous spread – children and elderly
-Local spread from contiguous site of infection: trauma (open fracture), bone surgery (ORIF), joint replacement
-Secondary to vascular insufficiency
What is a source of infection of osteomyelitis in infants?
Infected umbilical cord
What is a source of infection of osteomyelitis in children?
What is a source of infection of osteomyelitis in adults?
What are the most common infecting organisms of acute osteomyelitis in infants <1 year?
-Group B streptococci
What are the most common infecting organisms of acute osteomyelitis in older children?
What are the most common infecting organisms of acute osteomyelitis in adults?
-Coagulase negative staphylococci (prostheses), Propionibacterium spp (prostheses)
-Pseudomonas aeroginosa (esp. secondary to penetrating foot injuries, IVDAs)
Give examples of specific acute osteomyelitis causing organisms and their associated at risk populations.
Mixed infection including anaerobes
-Diabetic foot and pressure sores
-Sickle cell disease
-Fishermen and filleters
-Debilitating illness including HIV/AIDs
What site are usually affected by acute osteomyelitis?
Long bones: Metaphysis
Joints with intra-articular metaphysis
-Elbow (radial head)
What is the pathophysiology of acute osteomyelitis?
-Starts at metaphysis
-Vascular stasis (venous congestion+ arterial thrombosis)
-Acute inflammation: increased pressure
-Release of pressure (medulla, sub-periosteal, into joint)
-Necrosis of bone (sequestrum)
-New bone formation (involucrum)
-Resolution, or not (chronic osteomyelitis)
What is the clinical presentation of acute osteomyelitis in the infant?
-May be minimal signs, or may be very ill
-Failure to thrive
-Possibly. drowsy or irritable
-Metaphyseal tenderness + swelling
-Commonest around the knee
What is the clinical presentation of acute osteomyelitis in the child?
-Reluctant to move (neighbouring joints held flexed); not weight bearing
-May be tender fever (swinging pyrexia) + tachycardia
-Malaise (fatigue, nausea, vomiting – “nae weel” - fretful
What is the clinical presentation of a acute osteomyelitis in the adult?
-Primary OM seen commonly in thoracolumbar spine
-History of UTI or urological procedure
elderly, diabetic, immunocompromised
-Secondary OM much more common
-Often after open fracture, surgery (especially ORIF)
-Mixture of organisms
How is acute osteomyelitis diagnosed?
-History and clinical examination (pulse + temp.)
-FBC + diff WBC (neutrophil leucocytosis)
-Blood cultures x3 (at peak of temperature 60% +ve)
-U&Es – ill, dehydrated
What is the differential diagnosis for acute osteomyelitis?
-Acute septic arthritis
-Acute inflammatory -Arthritis
-Trauma (fracture, dislocation, etc.)
-Transient synovitis (“irritable hip”)
-Rare (sickle cell crisis, Gauchers disease, rheumatic fever, haemophilia)
-Soft tissue infection
What soft tissue infections are included in the differential diagnosis of acute osteomyelitis?
-Cellulitis - (deep) infection of subcutaneous tissues (Gp A Strep)
-Erysipelas - superficial infection with red, raised plaque (Gp A Strep)
-Necrotising fasciitis - aggressive fascial infection (Gp A Strep, Clostridia)
-Gas gangrene - grossly contaminated trauma (Clostridium perfringens)
-Toxic shock syndrome - secondary wound colonisation (Staph aureus)
How is acute osteomyelitis diagnosed?
-X-ray (normal in the first 10-14 days)
-Isotope Bone Scan (Tc-99, Gallium-67)
labelled white cell scan (Indium-111)
What is seen on radiographs of acute osteomyelitis?
-Early radiographs minimal changes
-10-20 days early periosteal changes
-Medullary changes: lytic areas
-Late osteonecrosis: sequestrum
-Late periosteal new bone: involucrum
What scan are used in acute osteomyelitis?
-Technetium-99m labelled diphosphonate
-Gallium 67 citrate delayed imaging
-Indium-111 labelled WBC scan
What is involved in the microbiological diagnosis of acute osteomyelitis?
-Blood cultures in haematogenous osteomyelitis and septic arthritis
-Tissue or swabs from up to 5 sites around implant at debridement in prosthetic infections
-sinus tract and superficial swab results may be misleading (skin contaminants)
How is acute osteomyelitis treated?
-Supportive treatment for pain and dehydration including general care and analgesia
-Rest and splintage
-Antibiotics (route dependent on patient, duration 4-6 weeks depending on response, choice empirical (Fluclox, and Benzylpen) while waiting)
What is choice of antibiotic dependent on in acute osteomyelitis?
-Spectrum of activity
-Penetration to bone
-Safety for long term administration
Why might antibiotics fail in acute osteomyelitis?
-Drug resistance – e.g. lactamases
-Bacterial persistence - ‘dormant’ bacteria in dead bone
-Poor host defences - IDDM, alcoholism…
-Poor drug absorption
-Drug inactivation by host flora
-Poor tissue penetration
What are the indications for surgery in acute osteomyelitis?
-Aspiration of pus for diagnosis & culture
-Abscess drainage (multiple drill-holes, primary closure to avoid sinus)
-Debridement of dead/infected /contaminated tissue
-Refractory to non-operative Rx >24..48 hrs
What are the possible complications of acute osteomyelitis?
-Altered bone growth
How might chronic osteomyelitis originate?
-May follow acute osteomyelitis (rare in children)
-May start de novo following surgery, open fracture or in immunosuppressed, diabetic, IVDU and elderly patients
How is chronic osteomyelitis characterised?
Repeated breakdown of healed wounds