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Musculoskeletal > Bone and Soft Tissue Infection > Flashcards

Bone and Soft Tissue Infection Flashcards

1
Q

Some concise notes from Davidsons

A

Source of infection: Haematogenous infection, post trauma, post operative

Most likely causative organisms: Staphylococcus, pseudomonas and mycobacterium tuberculosis

Risk factors: Often affects children and adolescents. Diabetes mellitus, compromised immunity (HIV and AIDS). Sickle cell disease (commonly associated with salmonella infection)

Progression of disease: Osteonecrosis leads to fragment of necrotic bone called a sequestrum (often found on any part of a bone but there is preferential targeting of the juxta-epiphyseal regions of long bones adjacent to joints). The cortex is perforated by pus, which stimulates the formation of new bone growth in the periosteum (involucrum), often leading to the development of sinuses that discharge throught the skin.

Presentation: Bone pain, tenderness, malaise, night sweats, pyrexia, adjacent joint may be painful to move. Potential for secondary septic arthritis.

Investigations: MRI best to investigate early changes. X-Ray (shows osteopenia, osteolysis and osteonecrosis). Cultures: open or image guided biopsy or blood cultures.

Osteolysis is the destruction of bone tissue.

Treatment: Parenteral antibiotics for 2 weeks followed by oral antibiotics for 4 weeks. Resection of infected bone and reconstruction is often recquired.

Complications: Secondary amyloidosis, skin malignancy at the at the margin of a discharging sinus. (marjolin’s ulcer).

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2
Q

What are the types of osteomyelitis?

A

Acute

Chronic

Specific (TB)

Non-specific (most common)

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3
Q

Who does osteomyelitis commonly affect?

A

Mostly children (diffrerent ages)

Boys is more common than girls

Someone with a history of trauma

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4
Q

What diseases might predispose someone to osteomyelitis?

A

Diabetes, rheum arthritis, immune compromise, long-term steroid treatment, sickle cell

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5
Q

What are the different sources of infection for osteomyelitis?

A
  • haematogenous spread – children and elderly
  • local spread from contiguous site of infection – trauma (open fracture), bone surgery (ORIF), joint replacement
  • secondary to vascular insufficiency
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6
Q

What are the common sources of infection in infants?

A

Infected umbilical cord

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7
Q

What are the common sources of infections in children?

A

Boils, tonsilitis, skin abrasions

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8
Q

What are the common sources of infection in adults?

A

UTI

Arterial line

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9
Q

What is the most likely infective organism for infants (less than 1 year)

A

Staph aurues

Strep group B

E.coli

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10
Q

What are the likely infective organisms for osteomyelitis in older children?

A

Older children: staph aureus, strep pyogenes, haemophilus influenzae

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11
Q

What is the likely infective organism for osteomyelitis in adults?

A

Staph Aureus

−coagulase negative staphylococci (prostheses), Propionibacterium spp (prostheses)

− Mycobacterium tuberculosis

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

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12
Q

What are the likely organisms to be infecting diabetic foot and pressure sores?

A

Mixed infection including anaerobes

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13
Q

What is the likely infective organism for sickle cell disease?

A

Salmonella spp

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14
Q

What type of bacteria are fishermen and filleters exposed to?

A

Mycobacterium marinum

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15
Q

What type of organism is liekly to cause osteomyelitis in HIV and AIDS patients?

A

Candida

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16
Q

What is the pathology of osteomyelitis?

A

starts at metaphysis – role of trauma?

vascular stasis

(venous congestion + arterial thrombosis)

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)

Notes from Davidsons: Any part of a bone may be involved but there is preferential targeting of the juxta-epiphyseal regions of long bones adjacent to joints

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17
Q

What are the clinical features on an infant?

A

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

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18
Q

What are clinical features in a child of osteomyelitis?

A

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

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19
Q

What are the clinical features of osteomyelitis in an adult?

A
  • Primary OM seen commonly in thoracolumbar spine
  • backache

history of UTI or urological procedure

elderly, diabetic, immunocompromised

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20
Q

Which is more common, primary or secondary OM?

A
  • Secondary OM much more common
  • often after open fracture, surgery (esp. ORIF)
  • mixture of organisms
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21
Q

Investigations for acute osteomyelitis?

A

history and clinical examination (pulse + temp.)

FBC + diff WBC (neutrophil leucocytosis)

ESR, CRP

blood cultures x3 (at peak of temperature – 60% +ve) (blood cultures for haematogenous osteomyelitis and septic arthritis)

U&Es – ill, dehydrated

22
Q

What is the differential diagnosis for acute OM?

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)

23
Q

How is the diagnosis of acute OM achieved?

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

Bone biopsy

24
Q

What are the features of acute OM on radiographs?

A

Early - minimal changes

10-20 days - early periosteal changes

Medullary changes - lytic areas

Late osteonecrosis (sequestrum)

Late periosteal new bone (involucrum)

25
Q

What is the treatment for acute Osteomyelitis?

A

supportive treatment for pain and dehydration – general care, analgesia

rest & splintage

antibiotics

  • route (IV/oral switch – 7-10 days?)
  • duration (4-6 wks – depends on response, ESR)
  • choice - empirical (Fluclox + BenzylPen) while waiting ( I think this is because staph aureus is a likely causative organism)

Surgery

26
Q

When might antibiotics fail?

A
  • 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

So the antibiotics won’t work for the following reasons:

The bacteria - resistant, or persistant (dormant bacteria in dead bone)

The host - Defences are poor, gut flora inactivates drug

The antibiotic - poor absorption, poor tissue penetration

27
Q

What are the indications for surgery in acute OM?

A
  • 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

So this is done to remove pus, which will be sent off for diagnosis and culture and to drain an abscess. Surgery is used to debride dead/infected/contaminated tissue. OR if non operative therapy isn’t working.

28
Q

What are the complications of acute OM?

A

•septicemia, death

metastatic infection

pathological fracture

septic arthritis

altered bone growth

chronic osteomyelitis

29
Q

Chronic Osteomyelitis

A

may follow acute osteomyelitis (now much rarer in children)

may start de novo

following operation

following open # (poss. many years earlier)

immunosuppressed, diabetics, elderly, drug abusers, etc.

repeated breakdown of “healed” wounds

30
Q

What arethe likely causative organisms for osteomyelitis?

A

often mixed infection

usually same organism(s) each flare-up

mostly Staph. Aureus, E. Coli, Strep. pyogenes, Proteus

31
Q

Pathology

A

cavities, poss. sinus(es)

dead bone (retained sequestra)

involucrum

histological picture is one of chronic inflammation

32
Q

What are the complications of chronic OM?

A
  • chronically discharging sinus + flare-ups
  • ongoing (metastatic) infection (abscesses)
  • pathological fracture
  • growth disturbance + deformities
  • squamous cell carcinoma (0.07%)
33
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? (how many operations/ years later?)
34
Q

What is the route of infection for septic arthritis?

A

haematogenous

eruption of bone abscess

direct invasion

penetrating wound (iatrogenic? – joint injection)

intra-articular injury

arthroscopy

35
Q

What are the common causative organisms for acute septic arthritis?

A

Staphylococus aureus

Haemophilus influenzae

Streptococcus pyogenes

E. coli

36
Q

What is the pathology assocaited with acture septic arthritis (pathway of disease)?

A

Synovitis (inflammation of the synovial membrane) with purulent joint effusion (increased intra-articular fluid)

Articular cartilage is attacked by bacterial toxin and cellular enzyme

Complete destruction of the articular cartilage

37
Q

What is the sequalae for acute septic arthritis?

A

complete recovery

or

partial loss of the articular cartilage and subsequent OA

or

fibrous or bony ankylosis

38
Q

What are the features of septic arthritis in the neonate?

A

Picture of septicaemia:

irritability

resistant to movement

ill

39
Q

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

A

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

40
Q

What are the features of acute septic arthrits in an adult?

A

often involves superficial joint (knee, ankle, wrist)

rare in healthy adult

May be delayed diagnosis

41
Q

What are the investigations for septic arthritis?

A

FBC, WBC, ESR, CRP, blood cultures

X ray

ultrasound

aspiration

42
Q

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

A

Infected joint replacement

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

changing picture of organisms, but Staph still most common

43
Q

What is the differential diagnosis for acute septic arthritis?

A

acute osteomyelitis

trauma

irritable joint

haemophilia

rheumatic fever

gout

Gaucher’s disease

44
Q

What is the treatment for acute septic arthritis?

A

general supportive measures

antibiotics (3-4 weeks)

surgical drainage & lavage - emergency (“never let the sun set on pus” ); open or arthroscopic lavage;

infected joint replacements - one stage revision, two stage revision, antibiotics only?

45
Q

Some concise notes from Davidson’s on septic arthritis:

A

Most rapid and destructive joint disease.

Source of infection: Haematogenous spread from either skin or upper respiratory tract, infection from either skin or upper respiratory tract, infection from direct puncture wounds or secondary to joint aspiration.

Risk factors: increasing age, pre-exisintg joint disease (RA), joint replacement, diabetes mellitus, immunosuppression, IVDA. RA predisposes infection via route of skin due to maceration of skin between toes.

Clinical features: Mono-arthritis and fever. If previous joint disease then multiple joints may be affected. The joint is usually swollen, hot and red, with pain at rest and on movement. Knee and hip are commonly targetted.

Causative organisms: Adults - staph aureus (especially if there is RA and diabetes. Sexually active adults - disseminated gonococcal infections have the potential to cause mono/oligoarthritis, painful pustular skin lesions may also be present.

46
Q

What are the classfications of tuberculosis?

A
  • Classification:
  • extra-articular(epiphyseal / bones with haemodynamic marrow)
  • intra-articular(large joints)
  • vertebral body
  • multiple lesions in 1/3 of patient
47
Q

What are the clincal features of bone TB?

A

Slow onset

Pain especially at night, swelling, loss of weight

Low grade pyrexia

Decreased ROM

Spinal TB - little pain, present with abscess of kyphosis

48
Q

What are the diagnostic features of TB?

A

long history

involvement of single joint

marked thickening of the synovium

marked muscle wasting

periarticular osteoporosis

49
Q

What are the investigations for Tuberculosis?

A

FBC , ESR

Mantouxtest

Sputum/ urine culture

Xray soft tissue swelling

periarticular osteopaenia

articular space narrowing

Joint aspiration and biopsy

AAFB identified in 10-20%

culture +vein 50% of cases

50
Q

What are the differential diagnosis for TB?

A

•transient synovitis

monoarticularRA

haemorrhagicarthritis

pyogenic arthritis

Tumour

51
Q

What is the treatment for tuberculosis?

A

Musculoskeletal (28 decks)

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