Bone and soft tissue infections Flashcards
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
- Boys>girls
- Trauma history
- 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?
- Staph aureus
- Group B Streptococci
- E. coli
In older children what are the causative organisms of acute osteomyelitis?
- Staph aureus
- Strep pyogenes
- Haemophilus influenzae
In adults what are the causatuve organisms of acute osteomyelitis?
- Staph aureus
- Coagulase -ve staph (prostheses)
- Mycobacterium tuberculosis
- Pseudomonas aeroginosa (esp secondary to penetrating foot injuries, IVDA)
Likely causative organism of acute osteomyelitis in
- Diabetic foot/pressure sores
- Sickle cell disease
- Fishermen
- HIV/AIDS patients
- Diabetic foot: mixed
- Sickle cell: salmonella spp
- Fishermen: Mycobacterium marinum
- HIV/AIDS: Candida
What long bones (metaphysis) are acute osteomyelitis likely to start?
- Distal femur
- Proximal tibia
- Proximal humerus
What joints with intra-articular metaphysis are acute osteomyelitis likely to start?
- Hip
- 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
- Dec. ROM
- Position change
- Commonest around knee
Clinical features of acute osteomyelitis in children?
- Severe pain
- Reluctant to move (neighbouring joints flexed), no weight bearing
- Tender fever (swinging pyrexia) and tachycardia
- Malaise (fatigue, nausea, vomiting)
- Toxaemia
Clinical features of acute osteomyelitis in adult?
- More common in thoracolumbar spine (primary OM)
- Backache
- 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
- Blood culture
- U and Es
Diff diagnosis of acute OM?
- Acute septic arthritis
- Acute inflammatory arthritis
- Trauma
- Transient synovitis
- 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?
-X-ray
-USS
-Aspirate
Isotope bone scan
-Labelled white cell scan
-MRI
Look on slide 21 for radiograph changes
:p
How do you use microbiology to diagnose acute OM?
- Blood cultures
- Bone biopsy
- 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?
- Drug resistance
- 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
- Abscess drainage
- Debridement of dead/infected/contaminated tissue
- Refractory to non-operative Rx
Complications of acute OM?
- Septicaemia, death
- Metastatic infection
- Pathological #
- Septic arthritis
- Altered bone growth
- Chronic osteomyelitis
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
- Dead bone
- Involucrum
- Chronic inflammation on histology
Complications of chronic OM?
- Chronically discharging sinus and flare ups
- Ongoing metastatic infection
- Pathological #
- growth disturbance and deformities
- SCC
Treatment of chronic OM?
- Local/systemic antib (gentamicin cement, orally, IV)
- Surgically remove bone infection
- Soft tissue problems
- Correct deformities
- Amputation
Route of infection in acute septic arthritis?
- Haematogenous
- Erupting bone abscess
- Penetrating wound/intra-articular injury/arthroscopy (direct invasion)
Common organisms in acute septic arthritis?
- Staph aureus
- Haemo. influenzae
- Strep pyogenes
- E. coli
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?
- Recovery or
- Partial loss of articular cartilage and subsequent OA or
- Fibrous or bony ankylosis
Picture of acute septic arthritis in infant?
Septicaemia picture
- Irritable
- Won’t move
- Ill
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
- X ray
- USS
- Aspirate
Commonest cause of acute septic arthritis?
Infected joint replacement (Staph aurerus most common)
Differential diagnosis of acute septic arthritis?
- Acute OM
- Trauma
- Irritable joint
- Haemophilia
- Rheumatic fever
- Gout
- Gauchers disease
Treatment of acute septic arthritis?
- Supportive measures
- Antibiotics 3-4w
- Surgical drainage and lavage
Classification of areas affected by TB?
- Extra-articular
- Intra-articular
- Vertebral body
Clinical features of TB in bone/joint?
- Malaise
- TB contact
- Pain (esp night), swelling, weight loss
- Low grade pyrexia
- Dec. ROM
- Ankylosis
- Deformity
TB pathology?
- Primary complex (lung or gut)
- Secondary spread
- Tuberculous granuloma
- Role of nutrition/other disease (eg HIV/AIDS)
Spinal symptoms of TB?
- Little pain
- Present with abscess or kyphosis
Diagnosing TB?
- History
- Involving single joint
- Thickening of synovium
- Muscle wasting
- Periarticular osteoporosis
Investigating TB?
-FBC, ESR Mantoux test -Sputum/urine culture -Xray -Aspirate and biopsy joint
Diff diagnosis of TB?
- Transient synovitis
- Monoarticular RA
- Haemorrhagic arthritis
- Pyogenic arthritis
- Tumour
Treatment of TB?
Chemo
- RIPE (remember from 2nd year)
- Rest
- Operative drainage if needed
