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E - MSK > Bone and Tissue Infections > Flashcards

Bone and Tissue Infections Flashcards

1
Q

Common background for acute osteomyelitis

A

Children - boys
History of trauma
Other long term disease

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2
Q

Source of infection for acute OM

A

Haematogenous spread
Local spread from contiguous site of infection (open fracture, bone surgery, joint replacement)
Secondary to vascular insufficiency
Infants = infected umbilical cord
Children = boils, tonsillitis, skin abrasions
Adults = UTI, arterial line

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3
Q

Common organisms of acute OM

A 
Infants - E. coli 
Older - staph aureus
Prostheses - coagulase -ve strep
Infectious arthritis - strep pyogenes 
Secondary to penetrating foot injury - pseudomonas aeruginosa 
Sickle cell disease - salmonella
Butchers - Brucella 
Candida - HIV, long term Abx, malignancy
Vertebral OM - s. aureus, TB 
STD - gonococcus
  • Group B strep
  • Strep pyogenes
  • Haemophilus influenzae
  • Proteus / Klebsiella
  • Mycobacteria tuberculosis
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4
Q

Pathology of acute OM - order of events

A
  1. Starts at metaphysis (role of trauma)
  2. Vascular stasis - venous congestion + arterial thrombosis
  3. Acute inflammation causes increased pressure
  4. Pus forms
  5. Release of pressure
  6. Necrosis of bone
  7. New bone formation
  8. Resolution or not - chronic OM
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5
Q

Clinical features of acute OM in infants

A 
Failure to thrive 
Drowsy 
Irritable 
Metaphyseal tenderness + swelling 
Positional change 
Decreased ROM esp knee
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6
Q

Clinical features of acute OM in children

A 
Severe pain 
Reluctant pain 
Fever + tachycardia 
Malaise 
Toxaemia
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7
Q

Clinical features of acute OM in adults

A

Primary OM common in thoracolumbar spine

  • Back ache
  • UTI Hx
  • Elderly, diabetic

Secondary OM more common

  • open fracture, surgery
  • mixture of organisms
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8
Q

Diagnosis of acute OM

A 
H&E
FBC + WCC (neutrophil leucocytosis)
ESR, CRP rise
Blood cultures x3 (+ve in60%)
U&Es - dehydrated 
X-Ray (normal in first 10-14 days)
MRI - preferred 
Isotope bone scan sometimes required i.e. in presence of prostheses)

USS
Aspiration
Labelled white cell scan

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9
Q

Differential diagnosis of acute OM

A 
Acute septic arthritis 
Acute inflammatory arthritis 
Trauma 
Transient synovitis 
Soft Tissue Infection
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10
Q

What does x-ray of acute OM show

A

Good disc = tumour (bad)
Bad disc = infection (good)

Nothing for 10-14 days
Then haziness + loss of density
Then subperiosteal reaction
Later see sequestrum (late osteonecrosis) and Involucrum (late periosteal new bone)

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11
Q

Microbiological diagnosis

A

Blood cultures
Bone biopsy
Tissue swabs from up to 5 sites around implant in prosthetic infections

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12
Q

Treatment of acute OM

A

Supportive for pain and dehydration
Rest and splint age

Abx (High dose IV 6 weeks)

  • empirical flucloxacillin and Benzylpenicillin while waiting for organism and sensitivities)
  • switch to oral 7-10 days
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13
Q

Indications for surgery in acute OM

A

Aspiration of pus for diagnosis and culture
Drain abscess and remove sequestra
Debridement of dead or infected or contaminated tissue
Refractory to non-surgical treatment >24-48hrs

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14
Q

Complications of acute OM

A 
Septicaemia 
Metastatic infection 
Pathological fracture
Septic Arthritis 
Altered bone growth 
Chronic OM
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15
Q

Common presentation of chronic OM

A

Follow acute OM
Following operation
Following open fracture
Long-term conditions

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16
Q

Common organism in chronic OM

A

Often mixed

- s aureus, E. coli, strep pyogenes, proteus

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17
Q

Treatment of chronic OM

A

Radical excision of sequestra
Skeletal stabilisation
Dead-space management - reconstruction
Abx - local gentamicin cement, beads or systemic oral / IV

18
Q

Complications of chronic OM

A

Amyloid
Squamous cell carcinoma development in sinus track
Pathological fracture
Ongoing infection

19
Q

Risk factors for OM

A 
Diabetes
Vascular disease
Impaired immunity 
Sickle cell disease
Surgical prostheses
Open fractures
20
Q

Patterns of infection of OM

A

In adults, cancellous bone is typically affected.
In children, vascular bone is commonly affected (i.e. long bone metaphases - esp. distal femur, upper tibia)

This leads to cortex erosion with holes (cloacae). The pus lifts up the periosteum causing death of the original bone (sequestrum). Continued bone formation by the elevated periosteum forms an involucrum. Pus may discharge into joint spaces or via sinuses to the skin.

21
Q

Route of infection in acute septic arthritis

A

Direct invasion - penetrating wound, injury
Eruption of bone abscess
Haematogenous
Metaphysial Septic Focus

22
Q

Organisms in acute septic arthritis

A

Staph aureus
Haem influenzae
Strep pyogenes
E. coli

23
Q

Pathology of ASA

A

acute synovitis and purulent joint effusion causing destruction of the articular cartilage

24
Q

Sequelae of ASA

A

Complete recovery
OR partial loss of the articular cartilage and OA
OR fibrous or bony ankylosis

25
Q

Presentation of ASA in neonate

A

irritability
resistant to movement
ill

26
Q

Presentation of ASA in child

A

Acute pain in single large joint
Reluctant to move
Increased temp and pulse and tenderness

27
Q

Presentation of ASA in Adult

A

Common in superficial joints (knee, ankle, wrist)

Rare in healthy adult

28
Q

Investigations of ASA

A 
FBC, WBC, ESR, CRP 
Blood cultures
X-ray 
USS
Aspiration
29
Q

Most common cause of ASA in adult

A

Infected joint replacement

30
Q

Ddx of ASA

A 
Acute OM 
Trauma
Irrritable joint 
Haemophilia 
Rheumatic fever 
Gout 
Gaucher's disease
31
Q

Treatment of ASA

A

Abx 4 weeks

Surgical drainage and lavage

32
Q

Classification of bone TB

A 
Extra-articular - epiphyseal / bones with haemodynamic marrow
Intra-articular - large joints 
Vertebral body (Pott's disease)
33
Q

How does TB spread to bones

A

Haematogenous or via nearby nodes

34
Q

Clinical features of bone TB

A 
Pain esp at night
Swelling
Cold abscess formation 
\+/- joint formation 
Joint pain on movement
Decreased ROM 
Muscle wasting 
Weight loss
Malaise, fever, lethargy 
Insidious onset
35
Q

Pathology of bone TB

A

Primary complex (in lung or gut). Then secondary spread causing a tuberculous granuloma

36
Q

How does spinal TB present

A

Little pain
Abscess
Kyphosis

37
Q

Diagnosis of bone TB

A 
Long history 
Involvement of single joint
Marked thickening of synovium 
Marked muscle wasting 
Periarticular osteoporosis
38
Q

Investigations for bone TB

A 
FBC
ESR - elevated
Matoux test = +ve
Sputum / Urine culture 
X-ray 
MRI 
Joint aspiration and biopsy
39
Q

Findings on x-ray in bone TB

A

Periarticular osteopenia
Articular space narrowing
Soft tissue swelling (MRI)

40
Q

findings on joint aspiration and biopsy in bone TB

A

AAFB in 20%

Culture +ve in 50%

41
Q

Ddx for bone TB

A 
Transient synovitis 
Monoarticular RA 
Haemorrhagic / Pyogenic arthritis 
Malignancy 
Gout
42
Q

Treatment for bone TB

A

Chemotherapy

  • Rifampicin, Isoniazid, Ethambutol for 8 weeks
  • Rifampicin, Isoniazid for 6-12 months

Rest and splintage
Operative drainage rarely needed

E - MSK (29 decks)

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