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)
Which two bursa are predominately affected by septic bursitis?
Olecranon
Prepatellar
What is the pathogenesis of septic bursitis?
Usually trauma to overlying skin
Often simultaneous cellulitis
Spread from contiguous focus - skin
Mostly s aureus, some skin strep
What is the treatment for septic bursitis?
Antibiotics, oral or IV
Operative resection of bursa if failure to respond to antibiotics or it recurs
What are the most common locations for osteomyelitis?
Long bones of extremities (legs more than arms)
Bones of feet
Vertebral column
When does osteomyelitis begin to show changes on radiographs?
Two weeks after infection starts
What’s the gold standard for diagnosing osteomyelitis?
Bone biopsy and culture
How long is therapy needed for osteomyelitis?
Minimum of 6 weeks for adults
What is acute hematogenous osteomyelitis?
Most common form in prepubertal children and IVDA and patients with catheters
Metaphysis of long bones - distal end of femur and proximal end of tibia
Antibiotics for three weeks
What is the cause of vertebral osteomyelitis?
Generally hematogenous but direct implantation can occur - s aureus, brucella, tb, fungal = blasto, cocc.
Can cause abscesses in surrounding tissues
Can be complicated by collapse of vertebra or cord compression
What are the symptoms of vertebral osteomyelitis?
Slowly progressive back pain
Maybe night sweats and fever
No fever until later in course
Tenderness
How is vertebral osteomyelitis diagnosed?
Bone biopsy and culture
MRI for imaging
What is the treatment for vertebral osteomyelitis?
Minimum 4-6 weeks antibiotics, usually 6
Surgery generally unnecessary unless unstable spine or large abscess
What is the course of osteomyelitis in diabetics?
Often indolent - months before presentation, no systemic symptoms
Recurrence frequent after antibiotic therapy - progressively proximal amputations common
What vascular insufficiency is associated with osteomyelitis?
Microvascular in diabetics
Macrovascular in peripheral vascular disease
What is acute vs. chronic cellulitis in patients with vascular disease generally due to?
Acute - s aureus or beta hemolytic strep
Chronic - anaerobes or enterobacteriaceae
