Bone and Soft Tissue Infections Flashcards Preview

Systems: MSK AB > Bone and Soft Tissue Infections > Flashcards

Flashcards in Bone and Soft Tissue Infections Deck (54)
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1

In what forms can osteomyelitis occur?

-Acute vs chronic
-Specific (e.g. TB) vs non-specific (most common)

2

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

3

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

4

What is a source of infection of osteomyelitis in infants?

Infected umbilical cord

5

What is a source of infection of osteomyelitis in children?

-Boils
-Tonsillitis
-Skin abrasions

6

What is a source of infection of osteomyelitis in adults?

-UTI
-Arterial line

7

What are the most common infecting organisms of acute osteomyelitis in infants <1 year?

-Staph aureus
-Group B streptococci
-E.coli

8

What are the most common infecting organisms of acute osteomyelitis in older children?

-Staph aureus
-Strep pyogenes
-Haemophilus influenzae

9

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)

10

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

11

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)

12

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)

13

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

14

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

15

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

16

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

17

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

18

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)

19

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

20

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

21

What scan are used in acute osteomyelitis?

-Technetium-99m labelled diphosphonate
-Gallium 67 citrate delayed imaging
-Indium-111 labelled WBC scan
-MRI

22

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)

23

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

24

What is choice of antibiotic dependent on in acute osteomyelitis?

-Spectrum of activity
-Penetration to bone
-Safety for long term administration

25

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

26

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

27

What are the possible complications of acute osteomyelitis?

-Septicemia, death
-Metastatic infection
-Pathological fracture
-Septic arthritis
-Altered bone growth
-Chronic osteomyelitis

28

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

29

How is chronic osteomyelitis characterised?

Repeated breakdown of healed wounds

30

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