Bone and Soft Tissue Infection

Question 1

What is osteomyelitis?

Answer 1

Infection of the bone

Question 2

What are the different types of osteomyelitis?

Answer 2

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

Question 3

Is specific or non-specific osteomyelitis more common?

Answer 3

Non-specific

Question 4

What age group and sex does acute osteomyelitis mostly affect?

Answer 4

• Mostly children
• Boys > girls

Question 5

What are risk factors for acute osteomyelitis?

Answer 5

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

Question 6

What are sources of infection for acute osteomyelitis?

Answer 6

• 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

Question 7

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

Answer 7

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

Question 8

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

Answer 8

• 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)

Question 9

Describe the pathology of acute osteomyelitis?

Answer 9

• 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)

Question 10

Where does acute osteomyelitis typically start?

Answer 10

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

Question 11

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

Answer 11

• 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

Question 12

How is acute osteomyelitis diagnosed?

Answer 12

• 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)

Question 13

What bloods can be done for acute osteomyelitis?

Answer 13

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

Question 14

What imaging can be done for acute osteomyelitis?

Answer 14

• 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

Question 15

What microbiological diagnosis can be done for acute osteomyelitis?

Answer 15

• 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)

Question 16

Describe the differential diagnosis for acute osteomyelitis?

Answer 16

• 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)

Question 17

What are some soft tissue infections included in the differential diagnosis for acute osteomyelitis?

Answer 17

• 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)

Question 18

What is the treatment for acute osteomyelitis?

Answer 18

• 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

Question 19

What are indications for surgery for acute osteomyelitis?

Answer 19

• 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

Question 20

What are some potential complications of acute osteomyelitis?

Answer 20

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

Question 21

What can chronic osteomyelitis occur after?

Answer 21

Can follow acute osteomyelitis or occur de novo:

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

Question 22

What are some risk factors for chronic osteomyelitis?

Answer 22

• immunosuppressed, diabetics, elderly, drug abusers, etc.

Question 23

What organisms are usually responsible for chronic osteomyelitis?

Answer 23

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

Question 24

Describe the pathology of chronic osteomyelitis?

Answer 24

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

Question 25

What are potential complications of chronic osteomyelitis?

Answer 25

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

Question 26

What is the treatment for chronic osteomyelitis?

Answer 26

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

Question 27

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

Answer 27

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

Question 28

Infection A is?

Answer 28

Septic arthritis

Question 29

Infection B is?

Answer 29

Osteomyelitis

Question 30

What organisms are typically responsible for acute septic arthritis?

Answer 30

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

Question 31

Describe the pathology of acute septic arthritis?

Answer 31

* 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

Question 32

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

Answer 32

* 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)

Question 33

What investigations should be done for acute septic arthritis?

Answer 33

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

Question 34

What is the differential diagnosis for acute septic arthritis?

Answer 34

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

Question 35

What is the treatment for acute septic arthritis?

Answer 35

* General supportive measures * Antibiotics * Surgical drainage and lavage

Question 36

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

Answer 36

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

Question 37

What are clinical features of TB in bones and joints?

Answer 37

* 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

Question 38

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

Answer 38

Especially at night

Question 39

Describe the pathology of TB in bones and joints?

Answer 39

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

Question 40

How does TB often present in the spine?

Answer 40

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

Question 41

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

Answer 41

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

Question 42

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

Answer 42

* 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

Question 43

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

Answer 43

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

Question 44

What is the treatment for TB in bones and joints?

Answer 44

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

Question 45

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

Answer 45

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