02-21 Infectious Arthritis Flashcards
What features of presentation distinguish infectious arthritis from other arthritides?
—acute onset of hot/red/swollen/LoF monoarticular inflammation that hurts even while pt is still
—effusion obvious
—likely will have open sore/cut/etc. nearby that seeded the infx
—prox LN enlarged
—may present with fever and 25% present w/ rigors
epidemiology w/ regard to age, infectious agent?
—bimodal distr: childhood and old age
—♂ predom
—in global south: TB common cause
—in global north: gram negative: infected protheses, IVDU, sexually trans
Pathophys of infx arthritis difference between:
—neonates and older patients
—young patients and other patients
—geriatric patients and younger patients
NEONATES
—b/c neonates’ epiphyseal plates have not yet sealed, there is communication between bone and joint capsule
—thus infectious arthritis → osteomyelitis in these little guys → poor prognosis =(
LES JEUNES
—trauma
—sex
—IV drugs
GERIATRICS
—many risk factors predispose elders to infx arthritis: pre-existing chronic arthritis, protheses systemic dz, and imm def
In what ways is synovial tissue susceptible to infection?
—highly vascularized (can get hematogenous spread)
—has glycoproteins which Staph can bind
What are the most common bugs that cause infx arthritis?
—Which are most common in each age group?
#1 is def Staph #2 is Group A Strep —both of which are skin commensals #3 neisseria g.
BY AGE
Neonates
—<1 month old are infected with Staph, group B strep, and Gm(-) bacilli. Until the introduction of conjugate Pre-vaccine, Hib predominated.
—Staph a. is most freq cause of septic arthritis in both children and adults.
—Group A strep have been runners up, but in the past decade group C, group B, group G streptococci have become important causes of septic arthritis.
DDx for a chronic monoarticular arthritis w/ granuloma on histo?
M tb, atypical mycobacterium, brucellosis and fungi including Sporothrix schenckii, Blastomyces dermatitidis, Coccidioides immitis, Candida species, Pseudallescheria boydii.
—Synovial biopsy with histologic stains and culture for fungi and mycobacterium is important in this situation. Brucellosis is diagnosed by serology.
—Lyme disease and parvovirus B19 are other causes of chronic monoarticular or pauciarticular arthritis, also diagnosed by serology.
Which joints most commonly involved?
knee is most commonly effected
—followed by other weight bearing joints, hip and ankle
**Bedridden patients who push themselves around on their elbows often sublux the sternoclavicular joint, with a high incidence of septic arthritis at the collar bone.
How many joints are usually affected when a pt presents w/ infex arth?
A monoarticular presentation (90%) is the rule, and should raise suspicion when one joint flares superimposed on an underlying polyarticular arthritis, i.e. rheumatoid arthritis. Polyarticular septic arthritis is sometimes seen with strep or staph infection, but involves only two or three joints (pauciarticular). Fever and arthritis are less impressive in gonococcal arthritis, which is distinguished by a migrating polyarticular presentation.
How specifically would gonorrheal arthritis present?
MNEMONIC: STD
[S]ynovitis of the knee
[T]enosynovitis of the hand
[D]ermatitis
Two clinical presentations!
GROUP 1
—distinguished by tenosynovitis and dermatitis
—Skin lesions: countable #s in multiple stages; usu maculopapular, but qqf necrotic, pustular, or vesicular.
—migratory polyarthralgia»_space; true polyarthritis, and inflam extends up tendon sheaths.
—Synovial fluid cell counts are lower than nongonococcal bacterial arthritis and synovial fluid culture is often (-)
—Blood culture may be (+), but only 20% of patients have GU sx of gonorrhea.
—DNA amplification tests may be used to detect N. gonorrhoeae in urethral, cervical, rectal, and pharyngeal swabs.
GROUP 2
—may present following a migratory polyarthritis, tenosynovitis, dermatitis, but now the arthritis has settled in one or two joints.
—synovial fluid = more purulent (culture on chocolate agar)
—culture more likely to be positive
—Blood cultures now negative.
—Cultures of cervix, urethra, and rectum are (+) in 90%.
—Blood cultures usu negative.
—DNA amplification tests may be used to detect N. gonorrhoeae in synovial fluid.
Whether these groups represent sequential stages of disease, or distinct presentations in different hosts is still debated. However, we are often faced with one or the other presentation and negative cultures. In this situation, response to ceftriaxone 1 gm a IV a day in 48 hours may be considered diagnostic.
INFECTED PROSTHETIC JOINT
—What % become infected?
—How does it get in there?
—Common organisms?
—1-5% become infected
—~1/2 infx introduced at surgery; may become apparent in mos-yrs
—Coag-neg staph common (indolent course)
—Hematog seeding at bone-cement interface w/ Staph a. or GAS presents acutely + sepsis or tox shock
—Infx in elderly patients w/ underlying dz: Gm(-) bacilli (20%) and anaerobes (7%).
How specifically would prosthetic joint infection present/how would you dx it?
DIFFICULT TO DX
—95% have joint pain
—<50% have fever, swelling, or sinus drainage.
—DDx vs aseptic inflammation, such as reaction to cement or metal, and mechanical problem.
—Mechan. probs painful w/ motion but comfortable at rest
—Constant pain = infection
—Plain film abnormal in 50%: lucencies greater than 2 mm along the bone-cement interface, migration of the prosthesis, periosteal reaction.
—Tc bone scan should be (-) by 8 months post-op, and a (-) scan = strong evidence against septic joint. However, positive bone scans or indium leukocyte scans are nonspecific and may be positive due to aseptic or mechanical problems.
—Thus, dx relies on aggressive attempts to isolate an organism by aspiration of joint fluid or arthrotomy tissue.
Septic Arthritis in Children
—Dx of septic arthritis is often delayed in kiddos
—Although outcome favorable in older kids w/ early dx and tx, younger may damage or dislocate epiphysis
—Tense joint effusion or abscess formation may compromise blood supply causing avascular necrosis (fem head)
¡¡Typical s/sx completely absent in neonates.
—Subtle irritability, low-grade fever, lack of spontaneous movement, refusal to bear weight, and asymmetry of extremity posturing are all important signs
What is toxic synovitis?
—Toxic synovitis of the hip; unilateral acute presentation; spontaneous resolution over one week in 70%.
—ETIOLOGY UNKNOWN
U/S: is there effusion? If so, should be tapped.
—Fever, WBC count, and sed rate all ~elevated, but there is enough overlap with septic arthritis to obscure their diagnostic value.
—Routine radiographs are helpful in excluding other diagnosis which include: slipped capital femoral epiphysis, fracture, avascular necrosis, juvenile rheumatoid arthritis, Ewing sarcoma, osteogenic sarcoma, and leukemia.
IVDU-induced septic arthritis
“Good prognosis w/ bad bugs”
—Unusual locations: sacroiliitis, sternoclavicular joint, and symphysis pubi
—Pseudomonas, Serratia and Candida species ~unique to IVDU
—However, most due to Staph w/ or w/o IVDU.
—Hips and shoulders are other common sites in heroin addicts and disseminated gonococcal disease and syphilis should be considered.
—Good response to abx tx alone (90%); few pts require surg drainage
Septic Sacroilitis
—Tricky one for PCPs
—75% of pts have acute fever and continuous low back pain exacerbated by motion and weight bearing, but sx are diffuse and bilateral.
—PE inadequate in disting. sacroiliitis from muscle pain, disk dz, femoral n. entrapment, bursitis, or intra-abd process
—Plain radiographs not helpful in early dx.
—Shear forces applied SI joint may help raise suspicion, if there is focal pain
—clinical suspicion? → directly to CT Scan or MRI.
—MRI uniquely suited, b/c it alone has the potential to define fluid in the SI joint, adjacent bone marrow inflammation, and soft tissue abscess which may extend into psoas, iliac, pyriformis muscles and abdominal cavity.
—These collections need pigtail catheter drainage or surgical debridement.
