Infections of Bones, Joints and Limbs

Question 1

Describe septic arthritis.

Who can be affected?

Answer 1

• Hot swollen joint(s) - common medical emergency.
• All ages can be affected but septic arthritis is more common in elderly people and very young children.
• Delayed treatment can lead to irreversible joint damage.
• Case fatality ~11-50%.
  
  • Fatality is mostly in patients who have multiple sites of septic arthritis.
• Resistance to conventional ABx is increasing.

Question 2

What are the criteria for diagnosis of septic arthritis?

Answer 2

• Newman definition - 1 of 4 points must be met:
  
  1. Isolation of a pathogenic organism from an affected joint.
  2. Isolation of a pathogenic organism from another source (e.g. blood) in the context of a hot red joint suspicious of sepsis.
  3. Typical clinical features and turbid joint fluid in the presence of previous ABx treatment.
  4. Postmortem or pathological features suspicious of septic arthritis.

Question 3

How does septic arthritis typically present?

Answer 3

• 1-2 week hx of a red, painful, and restricted joint.
• In patients in whom bacteria were cultured from synovial fluid:
  
  • Fever was recorded in 34%
  • Sweats in 15%
  • Rigors in 6%
• Generally, large joints (typically lower limb) are affected. Any joint can be affected. Common:
  
  • Knee
  • Hip
  • Lumbosacral spine
• Up to 20% of patients have more than one joint affeted.
• If pre-existing arthritis, the joint(s) will show signs out of proportion to disease.
• Low virulence causative organisms and fungal and mycobacterial infections can delay presentation.

Question 4

What are the conditions which make a patient predisposed to septic arthritis?

Answer 4

• Rheumatoid arthritis or OA
• Joint prosthesis
• IV drug use
• Alcoholism
• DM
• Previous intra-articular corticosteroid injection
• Cutaneous ulcers

Question 5

What are the causative organisms of septic arthritis?

Answer 5

• S. aureus
• S. pyogenes
• S. epidermis
• M. tuberculosis
• Salmonella
• Brucella
• Don’t forget Neisseria gonorrhoeae in those who are sexually active
• Kingella - rare but can cause septic arthritis in children
• Pasteurella - take note of the patient’s hx; if they have been bitten by animals this can cause septic arthritis.

Question 6

What are the differentials if a patient presents with ?septic arthritis?

Answer 6

• Septic arthritis
• Crystal arthritis (gout, calcium pyrophosphate disease)
• Reactive arthritis
• Monoarticular presentation of polyarthritis
• Intra-articular injury (fracture, meniscal tear etc.)
• Haemarthrosis
• Inflammatory OA
• Note! Mimics:
  
  • Cellulitis
  • Bursitis
  • Phlebitis

Question 7

Describe the pathogenesis of septic arthritis.

Answer 7

• Infection can be introduced into a joint by:
  
  • Haematogenous spread
  • Direct inoculation e.g trauma or iatrogenically

Question 8

Which investigations should you do if querying septic arthritis?

Answer 8

• If there is a concern regarding septic arthritis, prompt joint aspiration is required. Please contact orthopaedics for any joint other than knees, or for any prosthetic joints.

1. ​Aspiration from an area of clear skin: send for joint aspirate C&S (includes microscopy and crystals - call lab to inform of the sample).
2. Peripheral blood cultures.
3. Obtain relevant cultures, If suspected gonococcus, request PCR.
4. FBC, U&E, CRP, urate (NB - may be normal in acute gout).
5. X-ray joint (?evidence of chondrocalcinosis).
6. Coagulation screen if appropriate.
7. MRI if concerns re osteomyelitis.

Question 9

Describe the pharmacological management of acute septic arthritis.

Answer 9

• If the causative organism is thought to be S. aureus:
  
  • ​IV flucloxacillin 2g qds for 2 weeks then oral therapy.
  • Total course 4-6 weeks.
  • If penicillin allergy give Clindamycin IV 600mg qds.
• Discuss with orthopaedics for washout.
• If complicated (e.g. recent surgery or GI procedure) it is likely to be a gram negative organism, therefore discuss with infectious diseases or microbiology for ABx advice.

Question 10

Describe the management of a patient who presents with acute increase in pain with or without swelling in one or more joints.

Answer 10

Question 11

Describe the management of septic arthritis in secondary care.

Answer 11

Question 12

Describe reactive arthritis.

Answer 12

• Reiter’s syndrome
• Classic triad of conjunctivitis, urethritis and arthritis.
• Occurring after an infection e.g. urogenital or GI tract.
• Epidemiologically, the disease is more common in men.
• Dermatologic manifestations:
  
  • Keratoderma blennorrhagicum
  • Circinate balanitis
  • Ulcerative vulvitis
  • Nail changes
  • Oral lesions

Question 13

State the organisms which cause septic arthritis.

Answer 13

• Chlamydia trachomatis
• Shigella flexneri
• Salmonella enteritidis / typhimurium / muenchen
• Yersinia enterocolitica
• Pseudotuberculosis
• Campylobacter jejuni / fetus
• Ureaplasma urealyticum
• Clostridium difficile
• Neisseria gonorrhoea
• Borrelia burgdorferi
• Chlamydia pneumoniae
• Escherichia coli

Question 14

How is reactive arthritis treated?

Answer 14

• Reactive arthritis may be treated with full dose NSAID with gastric protection.
• AND treatment of precipitating factors e.g. chlamydia.

Question 15

What is osteomyelitis?

Answer 15

Inflammation of the bone and bone marrow usually caused by pyogenic bacteria, and rarely by mycobacteria or fungi.

Question 16

How do bones become infected in osteomyelitis?

Answer 16

• Haematogenous spread
• Local spread (from septic arthritis or cellulitis)
• Compound fracture
• Foreign body

Question 17

Which organisms predispose a patient to osteomyelitis?

Answer 17

• Salmonella - makes patient predisposed to sickle cell disease.
• Brucella - associated with travel, foreign body and unpasturised milks.
• S. epidermis - particluarly associated with infection in prosthetics because it forms a biofilm.
• H. influenzae - predisposes children <5.
• E. coli and others - UTI.

Question 18

Which bones are most commonly affected by osteomyelitis?

Answer 18

Question 19

How does haematogenous spread to bones usually present?

Answer 19

• Usually asymptomatic
• Skin sepsis may be present (but is usually absent)
• Organisms settle in growing metaphysis

Question 20

How can a foreign body introduce an infection into bone?

Answer 20

• Trauma
• Shrapnel / GSW
• Orthopaedic implant (K nail)
• Nail through a trainer (Pseudomonas lives in trainers)

Question 21

What are the causative organisms of osteomyelitis?

Answer 21

• S aureus (>80%)
• S. pyogenes (~5%)
• Gram negative bacteria
• M. tuberculosis

Question 22

What are the symptoms and signs of osteomyelitis?

Answer 22

• Painful swollen site
• Fever
• Reduced movement (may be the only sign in the veyy young)
• Paraplegia

Question 23

What are the preliminary investigations you should carry out if querying osteomyelitis?

Answer 23

• Fever
• WBC
• ESR
• CRP

Question 24

What are the more detailed investigations you should carry out if you suspect osteomyelitis?

Answer 24

• Blood culture
• X-ray
• MRI / CT / bone scan
• Pus
• Notes
  
  • Take 3 cultures (surgeons may take up to 6) as this increases the chance of finding bacteria on culture.
  • May be negative early on in the course of infection.

Question 25

What is the pharmacological treatment for acute osteomyelitis caused by S. aureus?

Answer 25

* Flucloxacillin IV 2g qds. * 2 weeks minimum IV followed by oral therapy. * Total course 4-6 weeks. * **If penecillin allergy** Clindamycin IV 600qds. * Seek specialist advice. * Consider referral for outpatient parenteral therapy (OHPAT).

Question 26

What is the pharmacological treatment for chronic osteomyelitis caused by S. aureus and occasionally coliforms?

Answer 26

* Oral flucloxacillin 1g qds. * If MRSA or penicillin allergy - oral doxycycline or co-trimoxazole (check sensitivities). * If coliforms suspected - seek specialist advice.

Question 27

What is the pharmacological treatment for MRSA osteomyelitis?

Answer 27

* Vancomycin IV * Dosing as per local guidance. * Aim for trough level of 15-20mg/L. * SEEK SPECIALIST ADVICE

Question 28

What are the risk factors for prosthetic joint infections in: * Primary arthroplasty * Revision arthroplasty of the hip and knee?

Answer 28

* Primary arthroplasty: * Rheumatoid arthritis * DM * Poor nutritional status * Obesity * Concurrent UTI * Steroid therapy * Malignancy * Postoperative surgical site infection * NNIS \>0 * Revision arthroplasty: * Prior joint surgery * Prolonged operating room time * Preoperative infection (of teeth, or skin, or UTI)

Question 29

Which organisms are commonly responsible for infections of the hip following arthroplasty?

Answer 29

Question 30

Which organisms are commonly responsible for infections of the knee following arthroplasty?

Answer 30

Question 31

Describe the investigation and diagnosis of a patient who presents with any of the following: * Sinus tract or persistent wound drainage * Acute onset of painful prosthesis * Chronic painful prosthesis

Answer 31

Question 32

Describe the management of a prosthetic joint infection.

Answer 32

Question 33

Describe the management of prosthetic joint infection when patients are not a candidate for new prosthesis.

Answer 33