Infection of bones and joints Flashcards
(40 cards)
What are the common causative agents of joint infection?
- Usually bacterial
- Rarely fungal
Some viruses (rubella, mumps and Hep. B) are associated with a mild self-lijmiting arthritis but this is not due to direct joint involvement
What is the predominant causative organism of septic arthritis?
Staph. aureus
What are the risk factors for the development of septic arthritis?
- RA
- OA
- Joint prostheses
- IV drug abuse
- Alcoholism
- Diabetes
- Recent intra-articular corticosteroid injection
- Presence of cutaneous ulcers
What organisms may cause septic arthritis in specific patient groups?
- In sexually active patients, gonococcal arthritis may be suspected
- In older and immunocompromised people, gram-negative organisms are more common than among young people (although staph./strep. still predominate)
What causative organism might be suspected in a patient presenting with septic arthritis who has recently been discharged from hospital, or in nursing home residents or patients with in dwelling urinary catheters?
MRSA
What might cause septic arthritis in immunocompromised patients?
Tuberculous arthritis
How might a joint become infected?
By direct injury or by blood borne infection from an infected skin lesion or another site
How does septic arthritis present?
A hot, swollen, tender restricted joint which has developed acutely. There may be evidence of infection elsewhere e.g. fever.
How might septic arthritis present in a patient who has a prosthetic joint?
May be early (within 3 months of surgery) or late
Early infection presents with wound inflammation or discharge, joint effusion, loss of function and pain
Late disease presents with pain or mechanical dysfunction
What investigations might be done if a patient is suspected of having septic arthritis?
- Synovial fluid gram stain and culture
- Synovial fluid white cell count
- Blood culture
- ESR and CRP
What is the appearance and white cell count of normal synovial fluid?
Appearance: straw-coloured
WCC: <3000 WCC/mm3
What is the appearance and white cell count of inflammatory synovial fluid?
Appearance: cloudy
WCC: >3000 WCC/mm3
What is the appearance and white cell count of septic synovial fluid?
Appearance: opaque
WCC: up to 75,000 WCC/mm3
How is acute septic arthritis managed in confirmed Staph. aureus infection?
Flucloxacillin + fusidic acid
Add gentamicin in immunosuppressed patients to cover gram-negative agents
Antibiotic therapy should be IV for 2 weeks, then oral for a further 4 weeks
The joint should be aspirated to dryness as often as necessary
How should acute septic arthritis be managed in confirmed staph aureus infection in a penicillin allergic patient?
Replace IV flucloxacillin with IV clindamycin or ceftriaxone for 2 weeks
Oral clindamycin or ceftriaxone for a further 4 weeks
How should acute septic arthritis be managed in confirmed MRSA infection?
Replace IV flucloxacillin with IV vancomycin
What is the most common cause of septic arthritis in previously fit young adults?
Gonococcal arthritis
What concomitant symptoms may be seen with gonococcal arthritis?
It occurs secondary to genital, rectal or oral infection although this is often asymptomatic
Concomitant skin infection is common- maculopapular pustules are seen
How is gonococcal arthritis treated?
Penicillin, ciprofloxacin or doxycycline for 2 weeks and joint rest
How is meningococcal arthritis treated?
Penicillin
What bones/joints are most commonly affected in tuberculous arthritis?
Hip knee and spine
What are the symptoms of tuberculous arthritis?
Insidious onset of pain, swelling and dysfunction
Patient is febrile, has night sweats and loses weight
How is tuberculous arthritis treated?
As for tuberculosis infection elsewhere (i.e. rifampicin, pyrazinamide, ethambutol, isoniazid) but with treatment extended to 9 months
What is osteomyelitis?
Infection of bone marrow which may spread to the bone cortex and periosteum via the Haversian canals. It results in inflammatory destruction of the bone and, if the periosteum becomes involved, necrosis.
