Bone and Soft Tissue Infections Flashcards
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
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?
- Septicemia, death
- Metastatic infection
- Pathological fracture
- Septic arthritis
- Altered bone growth
- Chronic osteomyelitis
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
What organisms are involved in chronic osteomyelitis?
- Often mixed infection
- Usually same organism(s) each flare-up
- Mostly Staph. Aureus, E. Coli, Strep. pyogenes, Proteus
What is the pathophysiology of chronic osteomyelitis/
- Cavities, poss. sinus(es)
- Dead bone (retained sequestra)
- Involucrum
- Histological picture is one of chronic inflammation
What are the possible complications of chronic osteomyelitis?
- Chronically discharging sinus + flare-ups
- Ongoing (metastatic) infection (abscesses)
- Pathological fracture
- Growth disturbance + deformities
- Squamous cell carcinoma (0.07%)
What are the treatment options for chronic osteomyelitis?
Long-term antibiotics?(either local (gentamicin cement/beads, collatamp) or systemic (orally/ IV/ home AB))
- Eradicate bone infection- surgically (multiple operations)
- Treat soft tissue problems
- Deformity correction?
- Massive reconstruction?
- Amputation?
What are the possible routes of infection in acute septic arthritis?
- Haematogenous
- eruption of bone abscess
- Direct invasion (penetrating wound, intra-articular injury, arthroscopy)
What are organisms are commonly implicated in acute septic arthritis?
- Staphylococcus aureus
- Haemophilus influenzae
- Streptococcus pyogenes
- E. coli
What is the pathophysiology behind acute septic arthritis?
- Acute synovitis with purulent joint effusion
- Articular cartilage attacked by bacterial toxin and cellular enzyme
- Complete destruction of the articular cartilage
What is the sequelae of acute septic arthritis?
Complete recovery OR Partial loss of the articular cartilage and subsequent OA OR Fibrous or bony anklyosis
How do neonates with acute septic arthritis often present?
Picture of septicaemia
- Irritability
- Resistant to movement
- Ill
How do children and adults often present with acute septic arthritis?
Acute pain in single large joint
- Reluctant to move the joint (any movement – c.f. bursitis where RoM OK)
- Increase temp. and pulse
- Increase tenderness
What is important to note about adults with septic arthritis?
- Often involves superficial joint (knee, ankle, wrist)
- Rare in healthy adult
- May be delayed diagnosis
How is acute septic arthritis investigated?
- FBC, WBC, ESR, CRP, blood cultures
- X ray
- Ultrasound
- Aspiration
What is the most common cause of septic arthritis in adults?
Infected joint replacements
What is the most common organism implicated in infected joint replacements?
Staph aureus
What are the outcomes of an infected joint replacement?
- Death
- Amputation
- Removal of arthroplasty
What is the differential diagnosis for acute septic arthritis?
- Acute osteomyelitis
- Trauma
- Irritable joint
- Haemophilia
- Rheumatic fever
- Gout
- Gaucher’s disease
How is acute septic arthritis treated?
- General supportive measures
- Antibiotics (3-4 weeks)
- Surgical drainage & lavage -
How is bone tuberculosis classified?
- Extra-articular (epiphyseal / bones with haemodynamic marrow)
- intra-articular (large joints)
- Vertebral body
Multiple lesions in 1/3 of patients
What are the clinical features of bone tuberculosis?
- Insidious onset & general ill health
- Contact with TB
- Pain (esp. at night), swelling, loss of weight
- Low grade pyrexia
- Joint swelling
- Decrease ROM
- Ankylosis
- Deformity
What is the pathophysiology behind bone tuberculosis?
- Primary complex (in lung or the gut)
- Secondary spread
- Tuberculous granuloma
- Note the role of nutrition and other disease (HIV/AIDs)
How does spinal tuberculosis present?
- Little pain
- Present with abscess or kyphosis
How is bone tuberculosis diagnosed?
- Long history
- Involvement of single joint
- Marked thickening of the synovium
- Marked muscle wasting
- Periarticular osteoporosis
How is bone tuberculosis investigated?
- FBC, ESR
- Mantoux test
- Sputum/urine culture
- X-Ray (soft tissue swelling, periarticular osteopenia, articular space narrowing)
- Joint aspiration and biopsy (AAFB identified in 10-20%, culture + in 50% of cases)
What is the differential diagnosis for bone tuberculosis?
- Transient synovitis
- Monoarticular RA
- Haemorrhagic arthritis
- Pyogenic arthritis
- Tumour
How is bone tuberculosis treated?
Chemotherapy
- Rifampicin, ethambutol and isoniazid 8 weeks
- Rifampicin and isoniazid further 6-12 months
- Rest and splintage
- Operative drainage rarely necessary
