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Muscluloskeletal Systems > Bone and Soft Tissue Infection > Flashcards

Bone and Soft Tissue Infection Flashcards

1
Q

What is the epidaemiology of acute haematogenous osteomyelitis?

(Who is it more common in? What is it associated with?)

A

Haematogenous spread is mostly children (different ages)

boys > girls

Associated with diabetes, rheumatoid arthritis, immune compromise, long-term steroid treatment, sickel cell

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2
Q

What should you look for in a history when you suspect acute haematogenous osteomyelitis?

A

History of trauma (minor)

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3
Q

What can be a source of infection in acute osteomyelitis?

3 general sources + Infants, children and adults

A

Haematogenous spread - children and elderly

Local spread from contaguous site of infection - trauma (open fracture), bone surgery (ORIF), joint replacement

Secondary to vascular insufficiency

In infants: infected umbilican cord

In children: boils, tonsilitis, skin abrasions

In adults: UTI, arterial line

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4
Q

What organisms cause acute osteomyelitis in infants?

under 1 year

A

Staph aureus
Group B streptococci
E. coli

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5
Q

What organisms cause acute osteomyelitis in older children?

A

Staph aureua
Strep pyogenes
Haemophilus influenzae

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6
Q

What organisms cause acute osteomyelitis in Adults?

A

Staph aureua

Coagulase negative staphylococci (prostheses)

Propionibacterium spp (prosthesus)

Streptococci pyogenes (infectious arthritis)

Mycobacterium tuberculosis

Pseudomonas aeroginosa (esp secondary to penetrating foot injuries, IVDAs)

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7
Q

Acute osteomyelitis in butchers may be caused by what organism?

A

Brucella

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8
Q

Acute osteomyelitis in fishermen, filleters may be caused by what organism?

A

Mycobacterium marinum

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9
Q

When may candida cause acute osteomyelitis?

A
  • Debilitating illness,
  • HIV AIDS,
  • long term antibiotic treatment,
  • extensive GI surgery,
  • malignancy
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10
Q

What 2 special cases may cause mixed infection acute osteomyelitis?

A

Diabetic foot (mixed infection including anaerobes)

Pressure sores

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11
Q

What organisms can cause vertebral and sternal acute osteomyelitis?

A

Vertebral

  • S. aureus
  • TB

Sternal:
-Coagulase negative staphylococci post cardiac surgery

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12
Q

What two conditions can result in acute osteomyelitis caused by salmonella spp and gonococcus?

A

Sickle cell disease -> salmonella spp

STD - gonococcus

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13
Q

Describe the pathology of osteomyelitis

A

Starts at metaphysis - role of trauma?

Vascular stasis
(venous congestion + arterial thrombus)

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)

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14
Q

Give 3 examples of long bones with their metaphysis outside the joint

A

Distal femur
Proximal tibia
Proximal humerus

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15
Q

Give two examples of joints with intra-articular metaphysis

A

Hip

Elbow (radial head)

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16
Q

What is involucrum?

A

An involucrum (plural involucra) is a layer of new bone growth outside existing bone seen in pyogenic osteomyelitis. It results from the stripping off of the periosteum by the accumulation of pus within the bone, and new bone growing from the periosteum.

It can be seen radiographically (i.e., with x-rays), although it is seen rarely in developed countries, given that osteomyelitis is rarely left untreated there.

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17
Q

What is a sequestrum?

A

A sequestrum (plural: sequestra) is a piece of dead bone that has become separated during the process of necrosis from normal or sound bone.

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18
Q

Describe the pathological process of sequestrum

A
  • Infection in the bone leads to an increase in intramedullary pressure due to inflammatory exudates
  • The periosteum becomes stripped from the osteum, leading to vascular thrombosis (granulation tissue “walls off” sequestrum)
  • Bone necrosis follows due to lack of blood supply (adjacent healthy bone is devascularised, causing further destruction)
  • Sequestra are formed
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19
Q

What are the clinical features of acute osteomyelitis in a child?

A

Severe pain

Reluctant to move (neighbouring joints held flexed); not weight bearing

May be tender and inflammed

Fever (swinging pyrexia) + tachycardia

malaise (fatigue, N+V - “Nae weel”)

Toxaemia

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20
Q

What are the clinical features of acute osteomyelitis in an infant?

A

May be minimal signs, or may be very ill

Failure to thrive

Possibly drowsy or irritable

Metaphyseal tenderness + swelling

Decreased ROM

Positional change

Commonest around knee

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21
Q

What are the clinical features of an adult with acute osteomyelitis?

Both primary and secondary

A

Primary OM seen commonly in thoracolumbar spine fever

  • Backache
  • History of UTI or urological procedure
  • Old, diabetic, immunocompromised

Secondary OM much more common

  • Often after open fracture, surgery (esp. ORIF)
  • Mixture of organisms
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22
Q

How do you diagnose acute osteomyelitis?

list the diagnostic tests -> bloods, imaging etc

A

History and clinical examination (pulse and temp)

FBC + diff WBC (neutrophil leucocytosis)

ESR, CRP

Blood cultures x3 (at peak temp -> 60% positive)

U+Es- ill, dehydrated

X-ray (normal in first 10-14 days)

USS

Aspiration

Isotope bone scan (Tc-99, Gallium-67)

Labelled white cell scan (Indium-111)

MRI

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23
Q

How can you make a microbiological diagnosis in acute osteomyelitis?

A

Blood cultures in haematogenous ostemyelitis 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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24
Q

What is the differential diagnosis of acute osteomyelitis?

A

Acute septic arthritis

Trauma (fracture, dislocation etc)

Acute inflammatory arthritis

Transient synovitis (“irritable hip”)

Rare:

  • Sickle cell crisis
  • Gaucher’s disease
  • Rheumatic fever
  • Haemophilia
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25
Q

How do you treat acute osteomyelitis?

A

Supportive treatment for pain and dehydration
-general care, analgesia

Rest and splintage

Antibiotics

  • Route (IV/oral switch - 7-10 days?)
  • Duration (4-6 wks - depends on response, ESR)
  • Choice - empirical (Fluclox + BenylPen) while waiting
26
Q

Give some reasons for antibiotic “failure”

A

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

27
Q

Give 4 indications for surgery in acute osteomyelitis

A

Aspiration of pus for diagnosis and culture

Abscess drainage (multiple drill-holes, primary closure to avoid sinus)

Debridement of dead/ infected/ contaminated tissue

Refractory to non-operative Rx >24-48hrs

28
Q

Give some complications of acute osteomyelitis

A

Septicaemia, death

Metastatic infection

Pathological fracture

Septic arthritis

Altered bone growth

Chronic osteomyelitis

29
Q

Give 3 reasons why subacute osteomyelitis may occur over acute osteomyelitis

A

Increased host resistance
Lower bacterial virulence
Antibiotic usage

30
Q

What are the clinical features of subacute osteomyelitis?

A

Long history (weeks, months)

Variable symptoms (pain, limp)

Local swelling/ warmth occasionally

Tenderness

31
Q

What is the differential diagnosis for subacute osteomyelitis?

A

Tumour - Ewing’s sarcoma, osteoid osteoma

TB

32
Q

What is Brodie’s abscess?

(What is it? Who does it occur in? What are its features?

A

A well defined cavity in cancellous bone

A Brodie abscess is a type subacute osteomyelitis

Older children

Painful limp, no systemic features

Radiographic lucency in long bone metaphysis

33
Q

What is the differential diagnosis of Brodie’s abscess?

A

Ewing’s sarcoma

34
Q

What is the treatment for Brodie’s abscess?

A

Curettage

35
Q

What are the investigations for subacute osteomyelitis?

A

X-ray

Bone scan

Biopsy (50% +ve) grow oragism

36
Q

What is the treatment for subacute osteomyelitis?

A

Prolonged course of antibiotics

Surgery - curettage

37
Q

What can cause chronic osteomyelitis?

A

May follow acute osteomyelitis (now much rarer in children)

May start de novo

  • Following operation
  • Following open fracture (possibly many years later)
  • Immunosuppressed, diabetes, elderly, drug abusers etc)

Repeated breakdown of “healed” wounds

38
Q

What is the definition of chronic osteomyelitis?

A

Chronically discharging sinus fixed to the underlying bone containing sequestrum surrounded by infected granulation tissue and involucrum

39
Q

What organisms usually cause chronic osteomyelitis?

A

Often mixed infection

usually same organism(s) each flare up

Mostly Staph. Aureus, E. Coli, Strep. Pyogenes, Proteus

40
Q

What is the pathology of chronic osteomyelitis?

What 3 features can it be boiled down to?

A

Sequestrum + involucrum + sinus

41
Q

What is the treatment for chronic osteomyelitis?

A

Long term antibiotics?

  • local (gentamicin cement/beads, collatamp)
  • Systemic (orally/ IV/ home AB)

Eradicate bone infection - surgically (multiple operations)

Treat soft tissue problems

Deformity correction?

Massive reconstruction?

Amputation?

42
Q

What are the complications of chronic osteomyelitis?

A

Chronic discharging sinus + flare ups

Ongoing (metastatic) infection (abscesses)

pathological fracture

Epithelioma

Growth disturbance + deformities

Amyloidosis

Squamous cell carcinoma (0.07%)

43
Q

What is the route of infection in acute septic arthritis?

A

Direct invasion

  • Penetrating wound (iatrogenic? - joint injection)
  • I/A injury
  • Arthroscopy

Eruption of bone abscess

Haematogenous

Metaphyseal septic focus

44
Q

What are the two outcomes of a metaphyseal septic focus?

A

Spread into either joint cavity -> septic arthritis

OR

Spread into periosteum -> osteomyelitis

45
Q

What are the common oragnisms of acute septic arthritis?

A

Staphylococcus aureus
Haemophilus influenzae
Streptococcus pyogenes
E. Coli

46
Q

What is the pathology of acute septic arthritis?

A

Acute synovitis with purulent joint effusion

Articular cartilage attacked by bacterial toxin and cellular enzyme

Complete destruction of the articular cartilage

47
Q

What are the sequelae of acute septic arthritis?

outcomes

A

Complete recovery

OR

partial loss of the articular cartilage and subsequent OA

OR

Fibrous or bony ankylosis

48
Q

What are the clinical features of acute septic arthritis in a neonate?

A

Picture of septicaemia

  • Irritability
  • Resistant to movement
  • Ill
49
Q

What are the clinical features of acute septic arthritis in a child?

A

Acute pain in a single large joint

  • Reluctant to move the joint (ANY movement- c.f. bursitis where RoM ok)
  • Increased temp and pulse
  • Increased tenderness
50
Q

What are the clinical features of acute septic arthritis in an adult?

A

Often involves superficial joint (knee, ankle, wrist)

Rare in healthy adult

51
Q

What are the investigations for acute septic arthritis?

A

FBC, WBC, ESR, CRP, blood cultures
X-ray
USS
Aspiration

52
Q

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

Wat can it result in?

A

Infected joint replacement

Rare (1-1.5%) but disaster (death, amputation, removal of arthroplasty

Changing picture of organisms, but Staph still most common

53
Q

What is the differential diagnosis of acute septic arthritis?

A 
Acute osteomyelitis
Trauma
Irritable joint
Hemophilia
Rheumatic fever
Gout
Gaucher's disease
54
Q

How do you classify tuberculosis of the bone and joint?

A

Extra-articular (epiphyseal/ bones with haemodynamic marrow)

Intra-articular (large joints)

vertebral body

55
Q

Does bone and joint TB involve single or multiple lesions?

A

Multiple lesions in 1/3 of patients

So 2/3 have single

56
Q

What are the clinical features of tuberculosis of the bone and joint?

A

Insidious onset and general ill health

Contact with TB

Pain (esp. at night), swelling, loss of weight

low grade pyrexia

Joint swelling

Decrease ROM

Ankylosis

Deformity

57
Q

Why is there poor entry of antibiotics in bone and joint TB?

A

Obliterative endarteritis

58
Q

What are the 2 stages of bone and joint TB?

A

Early short lived vascular

Chronic avascular

59
Q

How do you diagnose bone and joint TB?

A

Long history

Involvement of single joint

Marked thickening of the synovium

Marked muscle wasting

Periarticular osteoporosis

60
Q

What are the investigations for TB?

A

FBC, ESR
Mantoux test
Sputum/ Urine culture

X-ray

  • Soft tissue swelling
  • Periarticular osteopaenia
  • Articular space narrowing

Joint aspiration and biopsy

  • AAFB identified in 10-20%
  • Culture +ve in 50% of cases
61
Q

What is the differential diagnosis of bone and joint TB?

A

Transient synovitis
Monoarticular RA
Haemorrhagic arthritis
Pyogenic arthritis

Muscluloskeletal Systems (29 decks)

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