Bone and Soft Tissue Infection Flashcards
1
Q
What is osteomyelitis?
A
Infection of the bone
2
Q
What are the different types of osteomyelitis?
A
- Acute or chronic
- Specific or non-specific (most common)
3
Q
Is specific or non-specific osteomyelitis more common?
A
Non-specific
4
Q
What age group and sex does acute osteomyelitis mostly affect?
A
- Mostly children
- Boys > girls
5
Q
What are risk factors for acute osteomyelitis?
A
- History of trauma (minor)
- Other disease
- diabetes, rheum arthritis, immune compromise, long-term steroid treatment, sickle cell
6
Q
What are sources of infection for acute osteomyelitis?
A
- Haematogenous spread
- Children and elderly
- Local spread from contiguous site of infection
- Such as trauma (open fracture), bone surgery or joint replacement
- Secondary to vascular insufficiency
7
Q
What is a common source of infection for acute osteomyelitis in: infants, children, adults?
A
- In infants
- Infected umbilical cord
- In children
- Boils, tonsillitis, skin abrasions
- In adults
- UTI, arterial line
8
Q
What are the most common infecting organisms for acute osteomyelitis for: infants (<1 year), older children and adults?
A
- Infants (<1 year)
- Staph aureus, Group B streptococci, E. coli
- Older children
- Staph aureus, Strep pyogenes, Haemophilus influenzae
- Adults
- Staph aureus
- coagulase negative staphylococci (prostheses), Propionibacterium spp (prostheses)
9
Q
Describe the pathology of acute osteomyelitis?
A
- Starts at metaphysis
- Typically distal femur, proximal tibia, proximal humerus or for joints with intra-articular metaphysis the hip or elbow
- Vascular stasis
- Venous congestion and arterial thrombosis
- Acute inflammation causing increased pressure
- Release of pressure
- Necrosis of bone (sequestrum)
- New bone formation (involucrum)
- Resolution or not (maybe become chronic osteomyelitis)
10
Q
Where does acute osteomyelitis typically start?
A
- Starts at metaphysis
- Typically distal femur, proximal tibia, proximal humerus or for joints with intra-articular metaphysis the hip or elbow
11
Q
Describe some of the clinical features of acute osteomyelitis in: infants, children, adults?
A
- Infants
- may be minimal signs, or may be very ill
- failure to thrive
- poss. drowsy or irritable
- metaphyseal tenderness + swelling
- decrease ROM
- positional change
- commonest around the knee
- 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
- 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 (esp. ORIF)
- mixture of organisms
12
Q
How is acute osteomyelitis diagnosed?
A
- history and clinical examination (pulse + temp.)
- Bloods
- FBC + diff WBC (neutrophil leucocytosis)
- ESR, CRP
- blood cultures x3 (at peak of temperature – 60% +ve)
- U&Es – ill, dehydrated
- Imaging
- 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
- Microbiological diagnosis
- 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)
13
Q
What bloods can be done for acute osteomyelitis?
A
- FBC + diff WBC (neutrophil leucocytosis)
- ESR, CRP
- blood cultures x3 (at peak of temperature – 60% +ve)
- U&Es – ill, dehydrated
14
Q
What imaging can be done for acute osteomyelitis?
A
- 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
15
Q
What microbiological diagnosis can be done for acute osteomyelitis?
A
- 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)
16
Q
Describe the differential diagnosis for acute osteomyelitis?
A
- acute septic arthritis
- acute inflammatory arthritis
- trauma (fracture, dislocation, etc.)
- transient synovitis (“**irritable hip”)
- rare
- sickle cell crisis
- Gaucher’s disease
- rheumatic fever
- haemophilia
- Soft tissue infection
- 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)
17
Q
What are some soft tissue infections included in the differential diagnosis for acute osteomyelitis?
A
- 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)
18
Q
What is the treatment for acute osteomyelitis?
A
- Supportive for pain and dehydration
- General care such as analgesia
- Rest and splintage
- Antibiotics
- Empirical (fluclox and benzylpen)
- Choose based on spectrum, penetration of bone and safety for long term administration
- Failure can occur due to
- drug resistance – e.g. b lactamases
- bacterial persistence - ‘dormant’ bacteria in dead bone
- poor host defences - IDDM, alcoholism…
- poor drug absorption
- drug inactivation by host flora
- poor tissue penetration
- Surgery
- Indications
- 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
- Timing, drainage, lavage
- Infected joint replacements
- Indications
