Infections of Bones and Joints Flashcards
(28 cards)
What is septic arthritis?
• 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 approx 11%-50%.
• Resistance to conventional antibiotics is increasing.
What is the Newman definition to diagnose septic arthritis?
One of:
(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 antibiotic treatment
(4)post-mortem or pathological features suspicious of septic arthritis.
What is the typical presentation in a case of septic arthritis?
• 1–2 week history 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 leg) are affected. Common areas - Knee Hip, Lumbosacral spine (any joint is possible)
• Up to 20% of patients have more than one joint affected.
• 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.
What are some predisposing conditions for septic arthritis?
- Rheumatoid arthritis orosteoarthritis
- Joint prosthesis
- Intravenousdrugabuse
- Alcoholism
- Diabetes
- Previous intra-articular corticosteroid injection
- Cutaneous ulcers
What are some causative organisms for septic arthritis?
- S.aureus
- S.pyogenes
- S.epidermidis
- M.tuberculosis
- Salmonella
- Brucella (from unpasteurised dairy products),
- Don’t forget Neisseria gonorrhoeae in sexually active
- Kingella can cause infections in children
- Pasturella can cause infections in animal bites
What would a differential diagnosis be for the symptoms of septic arthritis?
Septic arthritis
Crystal arthritis (Gout, Calcium Pyrophosphate Disease
Reactive Arthritis
Monoarticular presentation of polyarthritis
Intra-articular injury (fracture, meniscal tear etc)
Haemarthrosis
Inflammatory OA
NB mimics eg cellulitis, bursitis, phlebitis
Describe the pathogenesis of bone + joint infection of septic arthritis
Or
How can infection be introduced into a joint?
– haematogenous spread
– direct inoculation e.g. trauma or iatrogenically.
How should one investigate a potential septic arthritis?
Prompt joint aspiration is required - contact ortho for any joint other than knees, or for prosthetics
- Aspiration from an area of clear skin: send for joint aspirate C&S (includes microscopy and crystals - call lab to inform them of sample)
- Peripheral blood cultures
- Obtain relevant cultures. If suspected gonococcus, request PCR
- FBC, U&Es, CRP, urate (NB - may be normal in acute gout)
- X-ray joint (?evidence of chonedrocalcinosis)
- Coagulation screen if appropriate
- MRI if concerns regarding osteomyelitis
How should acute septic arthritis be managed?
- Discuss with orthopaedics for washout
- If complicated e.g. recent surgery or GI procedure likely Gram negative organism therefore discuss with infectious disease or microbiology for antibiotic advice
IV flucloxacillin 2g qds for 2 weeks then oral therapy
Total course 4-6 weeks
If penicillin allergy Clindamycin IV 600mg qds
What is reactive arthritis?
- Reiter’s syndrome, also known as reactive arthritis -classic triad conjunctivitis, urethritis, and arthritis
- Occurring after an infection e.g. urogenital or GI tract.
- Epidemiologically, the disease is more common in men
- HLA-B27 is associated with reactive arthritis
• Dermatologic manifestations – keratoderma blennorrhagicum – circinate balanitis – ulcerative vulvitis – nailchanges – oral lesions
What organisms induce reactive arthritis?
Many, including:
– Chlamydia trachomatis – Shigella flexneri – Salmonella enteritidis/typhimurium/muenchen – Yersinia enterocolitica – Yersinia pseudotuberculosis (Pseudotuberculosis) – Campylobacter jejuni/fetus – Ureaplasma urealyticum – Clostridium difficile – Neisseria gonorrhoeaa – Borrelia burgdorferi – Chlamydia pneumoniae – Escherichia coli
How Amy reactive arthritis be treated>
Reactive arthritis may be treated with full dose NSAID with gastric protection and treatment of precipitating factors e.g. Chlamydia
What is osteomyelitis?
• Osteomyelitis - inflammation of the bone and bone marrow usually caused by pyogenic bacteria, and rarely by mycobacteria or fungi
How do bones become infected with osteomyelitis?
• Haematogenous spread • Local spread (from septic arthritis) • Compound fracture (open) • Foreign body
What predispositions to osteomyelitis may an individual have?
• Sickle cell disease • Travel/milk • Prosthesis • Children under 5 (rare in countries with Hib vaccination programme) • UTI Each predisposition has an associated organism cause
What areas are most commonly affected by osteomyelitis?
The humerus and the bones of the leg: femur, tibia, fibula, calcaneum
Describe the haematogenous spread of osteomyelitis to the bones
• Usually asymptomatic
• Skin sepsis may be present (but is usually
absent)
• Organisms settle in growing metaphysis near growth plate
What foreign bodies may cause osteomyelitis?
- Trauma
- Shrapnel/Gun shot wound
- Orthopaedic implant (K nail)
- Nail through trainer (Pseudomonas)
What are the most common organisms responsible for osteomyelitis?
- S. aureus (>80%)
- S. pyogenes (~5%)
- Gram negative bacteria • M. tuberculosis
What are the symptoms/signs of osteomyelitis?
- Painful swollen site
- Fever
- Reduced movement (may be only sign in very young)
- Paraplegia
What preliminary investigations should one perform with suspected osteomyelitis?
- Fever
- WBC
- ESR
- CRP
What should you look out for in imaging for suspected osteomyelitis?
- Radiology signs of osteomyelitis on plain film and CT include:
- periosteal elevation •Focal osteopenia •Cortical thinning •Scalloping
- xray- these signs can be delayed in early infection
- There may be marrow edema on MRI
- MRI and bone scans are more sensitive in early or ambiguous cases
- MRI is preferred for vertebral osteomyelitis as it can exclude paravertebral abscess and cord impringement.
How should one investigate osteomyelitis?
Investigations • Bloodculture • X-ray • MRI/CT/Bonescan • Pus
Notes:
• Take 3 cultures (surgeons may take up to 6)
• May be negative early on in the course of infection
• Operative sample
What therapeutic regimens may you use for osteomyelitis?
If acute: Flucloxacillin IV 2g qds
2 weeks minimumIV followed by oral therapy
Total course is 4-6 weeks
If penicillin allergy Clindamycin IV 600mg qds
Seek specialist advice
If chronic: Oral Flucloxacillin 1g qds
If MRSA or penicillin allergy oral doxycycline or co-trimoxazole (check sensitivities)
If coliforms suspected seek specialist advice
If MRSA: Vancomycin IV
Dosing as per local guidance
Aim for trough level of 15-20mg/L
Seek specialist advice
• Alternatives empirical
- Ciprofloxacin (for Salmonella infection)
- Isoniazid, Rifampicin, Pyrazinamide, Ethambutol (tuberculosis)
• Drainage/Removal of involucrum
