Flashcards in Bone and soft tissue infections Deck (46):
What is osteomyelitis?
Bone infection. Can be acute or chronic. Either specific (eg TB) or non-specific (most common)
In acute osteomyelitis when is it more common?
-Mostly in children
-Other disease (DM, rheum arthritis, immunocompromised, steroid treatment, sickle cell)
What are the different sources of infection? What typically causes infection in infants, children and adults?
-Haematogenous spread - children and elderly
-Local spread from contiguous infection site: trauma (open #), bone surgery (ORIF), joint replacement
-Secondary to vascular insufficiency
In infants: infected umbilical cord
In children: boils, tonsilitis, skin abrasions
In adults: UTI, arterial line
In infants <1y what are the causative organisms of acute osteomyelitis?
-Group B Streptococci
In older children what are the causative organisms of acute osteomyelitis?
In adults what are the causatuve organisms of acute osteomyelitis?
-Coagulase -ve staph (prostheses)
-Pseudomonas aeroginosa (esp secondary to penetrating foot injuries, IVDA)
Likely causative organism of acute osteomyelitis in
-Diabetic foot/pressure sores
-Sickle cell disease
-Diabetic foot: mixed
-Sickle cell: salmonella spp
-Fishermen: Mycobacterium marinum
What long bones (metaphysis) are acute osteomyelitis likely to start?
What joints with intra-articular metaphysis are acute osteomyelitis likely to start?
-Elbow (radial head)
What is the pathology of acute osteomyelitis?
-Starts at metaphysis
-Vascular stasis (venous congestion+arterial thrombosis)
-Acute inflammation, suppuration, release of pressure
-Necrosis of bone (sequestrum)
-New bone formation (involcrum)
-Resolution (or not - chronic osteomyelitis)
Clinical features of acute osteomyelitis in infants?
-May be minimal/very ill
-Fail to thrive
-Drowsy or irritable
-Metaphyseal tenderness and swelling
-Commonest around knee
Clinical features of acute osteomyelitis in children?
-Reluctant to move (neighbouring joints flexed), no weight bearing
-Tender fever (swinging pyrexia) and tachycardia
-Malaise (fatigue, nausea, vomiting)
Clinical features of acute osteomyelitis in adult?
-More common in thoracolumbar spine (primary OM)
-UTI/urological procedure history
-Elderly, DM, immunocompromised
-Secondary OM more common (open #, surgery etc)
Diagnosing acute osteomyelitis?
-History and exam (pulse+temp)
-FBC and WBC
-ESR and CRP
-U and Es
Diff diagnosis of acute OM?
-Acute septic arthritis
-Acute inflammatory arthritis
-Rare (sickle cell, Gauchers, rheumatic fever, haemophilia)
What soft tissue infections are differential diagnoses of acute OM?
-Cellulitis (Gp A strep)
-Erysipelas (Gp A strep)
-Necrotising fasciitis (gp A strep, clostridia)
-Gas gangrene (clostridium perfringens)
-TSS (staph aureus)
Investigations for acute OM?
Isotope bone scan
-Labelled white cell scan
Look on slide 21 for radiograph changes
How do you use microbiology to diagnose acute OM?
-Tissue or swabs at debridement if any
-Sinus tract, superficial swabs (may be misleading)
Treatment for acute OM?
-Supportive (analgesia, rest, splintage)
-Antibiotics (IV/oral, 4-6wks, Fluclox/benzylpen while waiting)
Why do antibiotics fail in acute OM?
-Bacterial resistance (dormancy)
-Poor host defences
-Poor drug absorption
-Drug inactivation by host flora
-Poor tissue penetration
Indications for surgery on acute OM?
-Aspiration of pus
-Debridement of dead/infected/contaminated tissue
-Refractory to non-operative Rx
Complications of acute OM?
-Altered bone growth
When may chronic OM occur?
-May follow acute OM
-De novo (following op/open #, immunosuppressed, DM, elderly, IVDA etc)
-Repeated breakdown of healed wounds
Organism in chronic OM?
-Usually same organisms each flare up
-Usually staph aureus, e. coli, strep pyogenes, Proteus
Pathology in chronic OM?
-Cavities, poss. sinuses
-Chronic inflammation on histology
Complications of chronic OM?
-Chronically discharging sinus and flare ups
-Ongoing metastatic infection
-growth disturbance and deformities
Treatment of chronic OM?
-Local/systemic antib (gentamicin cement, orally, IV)
-Surgically remove bone infection
-Soft tissue problems
Route of infection in acute septic arthritis?
-Erupting bone abscess
-Penetrating wound/intra-articular injury/arthroscopy (direct invasion)
Common organisms in acute septic arthritis?
Pathology in acute septic arthritis?
-Acute synovitis with purulent joint effusion
-Articular cartilage attacked by bacterial toxin and cellular enzyme
-Destruction of articular cartilage
Sequelae of acute septic arthritis?
-Partial loss of articular cartilage and subsequent OA or
-Fibrous or bony ankylosis
Picture of acute septic arthritis in infant?
Picture of acute septic arthritis in child/adult?
-Reluctant to move joint
-Inc temp, tenderness and pulse
Investigations of acute septic arthritis?
-FBC, WBC, ESR, CRP, blood culture
Commonest cause of acute septic arthritis?
Infected joint replacement (Staph aurerus most common)
Differential diagnosis of acute septic arthritis?
Treatment of acute septic arthritis?
-Surgical drainage and lavage
Classification of areas affected by TB?
Clinical features of TB in bone/joint?
-Pain (esp night), swelling, weight loss
-Low grade pyrexia
-Primary complex (lung or gut)
-Role of nutrition/other disease (eg HIV/AIDS)
Spinal symptoms of TB?
-Present with abscess or kyphosis
-Involving single joint
-Thickening of synovium
-Aspirate and biopsy joint
Diff diagnosis of TB?