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Musculoskeletal System > Bone and Soft Tissue Infection > Flashcards

Bone and Soft Tissue Infection Flashcards

1
Q

How can osteomyelitis be classified?

A

Acute or chronic

Specific or non-specific

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2
Q

What populations are most commonly affected by acute osteomyelitis?

A

Younger populations
Boys more commonly affected than girls
History of trauma
History of diabetes, rheumatic fever, an immunocompromised state, long term steroids or sickle cell pathologies may be relevant

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3
Q

Where are the possible sources of infection in cases of acute osteomyelitis?

A

Haematogenous spread- most common in children and elderly

Spread from contiguous site of infection such as trauma or bone surgery- most common in adults

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4
Q

What are some specific sources of infection of acute osteomyelitis?

A

Infected umbilical cord in infants
Boils, tonsillitis and skin abrasions in older children
UTIs and arterial lines in adults

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5
Q

What are the most common causative organisms of osteomyelitis?

A

In infants <1- staph aureus, group B streptococci and E. coli
Older children- staph aureus, strep pyogenes and haemophilus influenzae
Adults- Staph aureus and mycobacterium tuberculosis
Joint replacement- Low virulence organisms usually present on skin

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6
Q

What are the rarer causative organisms of osteomyelitis?

A
  • Mixed infection including anaerobes, most common in diabetic foot and pressure sores
  • Salmonella species, most common in sickle cell disease
  • Mycobacterium marinum, most common in fishermen and fishmongers
  • Candida, only occurs in immunocompromised
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7
Q

Describe the pathology of osteomyelitis

A
  1. Starts at metaphysis
  2. Progresses to vascular stasis, which causes venous congestion and arterial thrombosis
  3. Acute inflammation, causing increased pressure
  4. Suppuration
  5. Release of pressure, which can be in the medulla, sub-periosteal or into the joint
  6. Necrosis of the bone/sequestrum
  7. New bone formation/involucrum
  8. Resolution or progression to chronic myelitis
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8
Q

What are the clinical features of osteomyelitis in infants

A
  • Failure to thrive
  • Drowsiness
  • Irritability
  • Metaphyseal tenderness and swelling
  • Decreased range of movement
  • Positional change
  • Most common around knee
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9
Q

What are the clinical features of osteomyelitis in a child?

A
  • Severe pain
  • Reluctant to move
  • Not bearing weight on affected limb
  • May be tender
  • May have fever and tachycardia
  • Malaise
  • Toxaemia
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10
Q

What are the clinical features of osteomyelitis in an adult?

A
  • Primary OM commonly seen in thoracolumbar spine
  • Backache
  • History of UTI or urological procedure
  • Elderly, diabetic or immunocompromised
  • Secondary OM much more common, typically after surgery or an open fracture and infection involves a mixture of organisms
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11
Q

How is osteomyelitis diagnosed?

A 
Largely done on history and examination
Confirmatory tests are required, which can include:
-Full blood count
-White cell count
-ESR
-C-reactive protein
-Blood cultures
-Us + Es if ill or dehydrated
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12
Q

What else would be on a differential diagnosis with acute osteomyelitis?

A
  • Acute septic arthritis
  • Acute inflammatory arthritis
  • Trauma
  • Transient
  • Soft tissue infection
  • Rarer conditions such as sickle cell crisis, Gaucher’s disease, rheumatic fever and haemophilia
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13
Q

What investigations can be helpful in diagnosing osteomyelitis?

A
  • X-ray (appears normal in first 10-14 days of infection)
  • Ultrasound
  • Aspiration
  • Isotope bone scan
  • Labelled white cell scan
  • MRI
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14
Q

How can microbiological diagnosis of osteomyelitis be done?

A
  • Blood cultures in haematogenous osteomyelitis and septic arthritis
  • Bone biopsy
  • Tissue or swabs from up to 5/6 sites around implant at debridement of prosthetic infections
  • Sinus tract and superficial swab results can be misleading due to skin contaminants
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15
Q

What does the treatment of osteomyelitis involve?

A
  • Supportive treatment for pain and dehydration
  • Rest and splintage
  • Antibiotics- start on IV antibiotics to give initial high dose then switch to oral route after 7/10 days
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16
Q

How is the antibiotic to be used in osteomyelitis chosen?

A

Based on:

  • Spectrum of activity
  • Penetration to bone
  • Safety for long term administration
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17
Q

What are the possible causes of antibiotic failure?

A
  • Drug resistance
  • Bacterial persistence (bacteria lays dormant and reactivates)
  • Poor host defences
  • Poor drug absorption
  • Drug inactivation by host flora
  • Poor tissue penetration
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18
Q

What are the indications for surgery in acute osteomyelitis?

A
  • Aspiration of pus for diagnosis and culture
  • Abscess drainage
  • Debridement of dead/infected tissue
  • Passed non-operative window (24-48hrs since development of symptoms)
19
Q

What are the possible complications of acute osteomyelitis?

A
  • Septicaemia
  • Death
  • Metastatic infection
  • Pathological fracture
  • Septic arthritis
  • Altered bone growth
  • Chronic osteomyelitis
20
Q

What populations is chronic osteomyelitis common in?

A

Can follow acute osteomyelitis but is less common in children
Can follow an operation or in immunosuppressed, the elderly, diabetics and drug abusers

21
Q

What are the causative organisms of chronic osteomyelitis?

A

Mixture of organisms- staph aureus, E.coli, strep pyogenes and proteus

22
Q

Describe the pathology of chronic osteomyelitis

A

Cavities form and progress to dead bone and then involucrum

Histology shows chronic inflammation

23
Q

What are the complications of chronic osteomyelitis?

A
  • Chronically discharging sinus + flare ups
  • Ongoing/metastatic infection
  • Pathological fracture
  • Growth disturbance + deformities
  • Squamous cell carcinoma (rare)
24
Q

What is the treatment of chronic osteomyelitis?

A
  • Long term antibiotics
  • Eradication of bone infection surgically
  • Treat soft tissue problems
  • Deformity correction
  • Massive reconstruction
  • Amputation
25
Q

What are the possible routes of infection in chronic osteomyelitis?

A
  • Haematogenous spread
  • Eruption of bone access
  • Direct invasion (penetrating wound, intra-articular injury, arthroscopy)
26
Q

What are the causative organisms of acute septic arthritis?

A

Staph aureus
Haemophilus infleunzae
Strep pyogenes
E.coli

27
Q

Describe the pathology of acute septic arthritis

A

The disease progresses from acute synovitis with purulent joint effusion to articular cartilage being attacked by bacterial toxin and cellular enzyme, which progresses to a complete destruction of the articular cartilage.

28
Q

What are the possible outcomes of acute septic arthritis?

A
  • Complete recovery
  • Partial loss of the articular cartilage and subsequent osteoarthritis
  • Fibrous or bony ankylosis
29
Q

What are the characteristics of acute septic arthritis in neonates?

A 
General septicaemia
Irritability
Resistant to move
General illness
Usually multiple sites
30
Q

What are the characteristics of acute septic arthritis in children and adults?

A

Acute, severe pain in a single, large joint
Patient resistant to move affected joint at all
Increased temperature
Increased pulse
Tenderness

31
Q

What investigations can be helpful in diagnosing acute septic arthritis?

A 
Full blood count
White cell count
Erythrocyte sedimentation rate
C-reactive protein
Blood cultures
X-ray
Ultrasound 
Aspiration
32
Q

What is the most common cause of acute septic arthritis in adults and what are the possible outcomes of this?

A

Infected joint replacement

Can result in death, amputation or removal of the arthroplasty

33
Q

What is the most common causative organism of acute septic arthritis in adults?

A

Staph aureus

34
Q

What is on the differential diagnosis for acute septic arthritis?

A
  • Acute osteomyelitis
  • Trauma
  • Irritable joint
  • Haemophilia
  • Rheumatic fever
  • Gout
  • Gaucher’s disease
35
Q

How is acute septic arthritis treated?

A

General supportive measures
3-4 weeks of antibiotics
Surgical drainage and lavage
If early infection, antibiotics can be curative but if pus is present then surgery is necessary

36
Q

What are the different kinds of tuberculosis infection affecting joints?

A

Extra-articular (epiphyseal/ bones with haemodynamic marrow)
Intra-articular (large joints)
Vertebral bodies

37
Q

In what population is tuberculosis affecting the vertebral bodies most common?

A

The elderly (multiple sites in ~1/3 of patients)

38
Q

What are the clinical features of a tuberculosis infection affecting bones and joints?

A
  • Insidious onset and general ill health
  • Contact with tuberculosis
  • Pain (most common at night)
  • Swelling
  • Weight loss
  • Low grade pyrexia
  • Joint swelling
  • Decreased range of movement
  • Ankylosis
  • Deformity
39
Q

Describe the pathology of tuberculosis infection

A

Primary infection present in lungs or gut
Secondary spread can cause spread to bones and joints, where tuberculous granulomas can occur
Malnutrition and other diseases such as HIV can help progress disease

40
Q

Based on what characteristics can diagnosis of tuberculosis be suspected?

A
  • Long history
  • Involvement of a single joint
  • Marked thickening of the synovium
  • Marked muscle wasting
  • Periarticular osteoporosis
41
Q

What investigations can be helpful in tuberculosis?

A
  • Full blood count
  • Erythrocyte sedimentation rate
  • Mantoux test
  • Sputum/urine culture
  • X-ray
  • Joint aspiration and biopsy
42
Q

What else would be on the differential diagnosis when tuberculosis symptoms are present?

A
  • Transient synovitis
  • Monoarticular arthritis
  • Haemorrhagic arthritis
  • Pyogenic arthritis
  • Tumour
43
Q

How is tuberculosis treated?

A

Treatment of tuberculosis involves either chemotherapy or drug therapy as follows:
Rifampicin, isoniazid, pyranizamide and ethambutol for 2 months
Followed by pyranizamide and ethambutol for 4 months
Rest and splintage can also be helpful, but operative drainage is very rarely necessary.

Musculoskeletal System (28 decks)

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