Bone and Soft Tissue Infection Flashcards by Fouzia Jamal

What is osteomyelitis?

Infection of the bone

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What are the different types of osteomyelitis?

Acute or chronic
Specific or non-specific (most common)

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Is specific or non-specific osteomyelitis more common?

Non-specific

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What age group and sex does acute osteomyelitis mostly affect?

Mostly children
Boys > girls

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What are risk factors for acute osteomyelitis?

History of trauma (minor)
Other disease
- diabetes, rheum arthritis, immune compromise, long-term steroid treatment, sickle cell

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What are sources of infection for acute osteomyelitis?

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

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What is a common source of infection for acute osteomyelitis in: infants, children, adults?

In infants
- Infected umbilical cord
In children
- Boils, tonsillitis, skin abrasions
In adults
- UTI, arterial line

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What are the most common infecting organisms for acute osteomyelitis for: infants (<1 year), older children and adults?

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)

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Describe the pathology of acute osteomyelitis?

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)

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Where does acute osteomyelitis typically start?

Starts at metaphysis
- Typically distal femur, proximal tibia, proximal humerus or for joints with intra-articular metaphysis the hip or elbow

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Describe some of the clinical features of acute osteomyelitis in: infants, children, adults?

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

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How is acute osteomyelitis diagnosed?

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)

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What bloods can be done for acute osteomyelitis?

FBC + diff WBC (neutrophil leucocytosis)
ESR, CRP
blood cultures x3 (at peak of temperature – 60% +ve)
U&Es – ill, dehydrated

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What imaging can be done for acute osteomyelitis?

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

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What microbiological diagnosis can be done for 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)

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Describe the differential diagnosis for acute osteomyelitis?

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)

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What are some soft tissue infections included in the differential diagnosis for 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)

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What is the treatment for acute osteomyelitis?

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

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What are indications for surgery for 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 some potential complications of acute osteomyelitis?

septicemia, death
metastatic infection
pathological fracture
septic arthritis
altered bone growth
chronic osteomyelitis

What can chronic osteomyelitis occur after?

Can follow acute osteomyelitis or occur de novo:

Following operation
Risk factors
- immunosuppressed, diabetics, elderly, drug abusers, etc.

What are some risk factors for chronic osteomyelitis?

immunosuppressed, diabetics, elderly, drug abusers, etc.

What organisms are usually responsible for chronic osteomyelitis?

Often mixed
Usually same organism each flare up
Mostly Staph. Aureus, E. Coli, Strep. pyogenes, Proteus

Describe the pathology of chronic osteomyelitis?

cavities, poss. sinus(es)
dead bone (retained sequestra)
involucrum
histological picture is one of chronic inflammation

What are potential complications of chronic osteomyelitis?

* chronically discharging sinus + flare-ups * ongoing (metastatic) infection (abscesses) * pathological fracture * growth disturbance + deformities * squamous cell carcinoma (0.07%)

What is the treatment for chronic osteomyelitis?

* Long term antibiotics * Local * Systemic * Eradicate bone infection surgically * Treat soft tissue problems * Deformity correction * Massive reconstruction * Amputation

What are the different route of infection for acute septic arthritis?

* haematogenous * eruption of bone abscess * direct invasion * penetrating wound (iatrogenic? – joint injection) * intra-articular injury * arthroscopy

Infection A is?

Septic arthritis

Infection B is?

Osteomyelitis

What organisms are typically responsible for acute septic arthritis?

* *Staphylococus aureus* * *Haemophilus influenzae* * *Streptococcus pyogenes* * *E. coli*

Describe the pathology of acute septic arthritis?

* Acute synovitis with purulent joint effusion * Articular cartilage attacked by bacterial toxin and cellular enzyme * Complete destruction of articular cartilage * Finally complete recovery or partial loss of articular cartilage or fibrous or bony ankyloses

What are the clinical features of acute septic arthritis in: neonate, child/adult, adult?

* Neonate * irritability * resistant to movement * ill * Child/adult * 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 * Adult * often involves superficial joint (knee, ankle, wrist) * rare in healthy adult * May be delayed diagnosis * Infected joint replacement (most common cause)

What investigations should be done for acute septic arthritis?

* FBC, WBC, ESR, CRP, blood cultures * X ray * ultrasound * aspiration

What is the differential diagnosis for acute septic arthritis?

* acute osteomyelitis * trauma * irritable joint * haemophilia * rheumatic fever * gout * Gaucher’s disease

What is the treatment for acute septic arthritis?

* General supportive measures * Antibiotics * Surgical drainage and lavage

What are the different classifications of TB in bones and joints?

* extra-articular (epiphyseal / bones with haemodynamic marrow) * intra-articular (large joints) * vertebral body

What are clinical features of TB in bones and joints?

* 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

When does the pain due to TB in bone and joints occur usually?

Especially at night

Describe the pathology of TB in bones and joints?

* primary complex (in the lung or the gut) * secondary spread * tuberculous granuloma

How does TB often present in the spine?

Can occur in the spine where it causes little pain but presents with abscess or kyphosis

What does the diagnosis of TB in bones and joints involve?

* long history * involvement of single joint * marked thickening of the synovium * marked muscle wasting * periarticular osteoporosis

What investigations should be done for TB in bones and joints?

* FBC , ESR * Mantoux test * Sputum/ urine culture * Xray soft tissue swelling * periarticular osteopaenia * articular space narrowing * Joint aspiration and biopsy * AAFB identified in 10-20% * culture +ve in 50% of cases

What is the differential diagnosis for TB in bones and joints?

* transient synovitis * monoarticular RA * haemorrhagic arthritis * pyogenic arthritis * Tumour

What is the treatment for TB in bones and joints?

* Chemotherapy * Initial: rifampicin, isoniazid and ethambutol (8 weeks) * Then: rifampicin and isoniazid (6- 12months) * Rest and splintage * Operative drainage if necessary

What is the medical treatment for TB in bones and joints?

* Initial: rifampicin, isoniazid and ethambutol (8 weeks) * Then: rifampicin and isoniazid (6- 12months)

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Bone and Soft Tissue Infection Flashcards

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