Bone and Soft Tissue Infections Flashcards
(54 cards)
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?
- Mostly children
- M>F
- 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?
- Boils
- Tonsillitis
- Skin abrasions
What is a source of infection of osteomyelitis in adults?
- UTI
- Arterial line
What are the most common infecting organisms of acute osteomyelitis in infants <1 year?
- Staph aureus
- Group B streptococci
- E.coli
What are the most common infecting organisms of acute osteomyelitis in older children?
- Staph aureus
- Strep pyogenes
- Haemophilus influenzae
What are the most common infecting organisms of acute osteomyelitis in adults?
- Staph aureus
- Coagulase negative staphylococci (prostheses), Propionibacterium spp (prostheses)
- Mycobacterium tuberculosis
- 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
Salmonella spp.
-Sickle cell disease
Mycobacteriumm marinum
-Fishermen and filleters
Candida
-Debilitating illness including HIV/AIDs
What site are usually affected by acute osteomyelitis?
Long bones: Metaphysis
- Distal femur
- Proximal tibia
- Proximal humerus
Joints with intra-articular metaphysis
- Hip
- Elbow (radial head)
What is the pathophysiology of acute osteomyelitis?
- Starts at metaphysis
- Vascular stasis (venous congestion+ arterial thrombosis)
- Acute inflammation: increased pressure
- Suppuration
- 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
- Decrease ROM
- Positional change
- Commonest around the knee
What is the clinical presentation of acute osteomyelitis in the child?
- Severe pain
- Reluctant to move (neighbouring joints held flexed); not weight bearing
- May be tender fever (swinging pyrexia) + tachycardia
- Malaise (fatigue, nausea, vomiting – “nae weel” - fretful
- Toxaemia
What is the clinical presentation of a acute osteomyelitis in the adult?
-Primary OM seen commonly in thoracolumbar spine
-Backache
-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)
- ESR, CRP
- 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)
-Ultrasound
-Aspiration
-Isotope Bone Scan (Tc-99, Gallium-67)
labelled white cell scan (Indium-111)
-MRI
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
- MRI
What is involved in the microbiological diagnosis of acute osteomyelitis?
- Blood cultures in haematogenous osteomyelitis and septic arthritis
- Bone biopsy
- 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)
- Surgery
What is choice of antibiotic dependent on in acute osteomyelitis?
- Spectrum of activity
- Penetration to bone
- Safety for long term administration
