Skeletal Micro Flashcards
What are the three mechanisms of spread to a joint?
Hematogenously Direct inoculation (trauma, surgery, injection, bite) Contiguous spread (ulcers)
What are the three different syndromes resulting from infection of joints?
Acute bacterial - usually mono or oligo articular, rapid onset and progression, can cause permanent damage
Viral - poly articular, symmetric, no therapy required, resolves spontaneously with no permanent damage
Chronic mono or oligo arthritis - mycobacteria, fungi, or fastidious bacteria)
What are risk factors for dev of septic arthritis?
Underlying abnormal joint
Systemic conditions
Sequela of osteomyelitis in joints where capsule inserts distal to epiphyses of associated bone (hip, proximal radius)
What are the most commonly affected joints in septic arthritis?
Weight bearing joints
Especially knee
Hip also a lot in kids
How is the pain different in septic arthritis than bursitis?
SA - pain more intense with extension than flexion
Bursitis - pain more intense with flexion than extension
What is needed for diagnosis of septic arthritis?
Joint fluid WBC > 50,000-100,000
Gram stain and culture can help
What are the treatment objectives with septic arthritis?
Drainage of infected joint fluid
Antibiotic therapy - empiric then narrow - 2-4 weeks (usually 4, 2 in gonorrhoeae)
Early rehab to preserve joint function
What should you treat for if a patient is immunocompromised?
GNRs
What are the different methods of drainage of an infected joint?
Repetitive aspirations
Arthroscopic drainage
Open drainage - hip and shoulder
What are predictors of poor outcome in septic arthritis?
Underlying joint disease Delay in appropriate treatment Multiple joint involvement Elderly Involvement of hip or shoulder
What is the most common virus responsible for viral arthritis and what is its presentation?
Parvovirus B19
Slap cheek rash on face of children, fine reticular rash on trunk and legs - unusual in children
Arrest at pronormoblast stage can mimic anemia
Usually large joints in hand, can mimic RA
Usually resolves within 2 weeks
How is diagnosis of viral arthritis from parvovirus B19 done?
Serum IgM antibody to parvovirus
PCR analysis
Bone marrow biopsy
What is the main mechanism and most common cause of infection of prosthetic joints?
Direct inoculation
Coagulase negative staph as common or more than s aureus
How does the presentation of an infected prosthetic joint compare to an infected native joint?
Usually less severe and more chronic
Present sub-acutely over months
Main symptom is progressive joint pain
What do radiographs show in infected prosthetic valves?
Lucencies around prosthesis
Movement of device
Reaction of periosteum of adjacent bone
When are outcomes of a one step protocol favorable?
When relatively avirulent organisms involved
When are chronic suppressive antibiotics okay as opposed to removal of an infected prosthetic joint?
Low virulence organism
Removal of prosthetic is risky
Prosthesis functions reasonably well
What are the two syndromes caused by gonococcal septic arthritis?
Arthritis
Tenosynovitis-dermatitis (dermatitis-arthritis)
Which joints are more commonly affected in gonococcal septic arthritis?
Knees
Wrists
Ankles
How is disseminated gonococcal infection diagnosed?
Gram stain and culture yield is low
Must culture mucosal surfaces - cervix, urethra, rectum, pharynx
NAATs of mucosal surfaces adjunct for culture
What is the treatment of disseminated gonococcal infection?
No need for surgery
IV ceftriaxone for 2 weeks
What are the symptoms of chronic infectious arthritis?
Mono articular involvement, slow onset, indolent course, lack of systemic symptoms, progressive destruction of joint
Physical exam mostly normal - just pain and possible effusion
What pathogens are associated with chronic arthritis?
Syphillis Lyme disease Whipples disease Fungal pathogens - blastomyces, coccidioides, paracoccidioides, not histo Tb
How is chronic arthritis due to fungal pathogens diagnosed and treated?
Organisms seen in synovial fluid
Operative drainage usually unnecessary
Medical therapy with anti fungal drugs (itraconazole)
