Author:
Amin AntoineKazzi
Stephen R.Hayden
MohamadKanso
Description
- Bacteria can be introduced into a joint by:
- Hematogenous spread (most common)
- Invasive procedures
- Contiguous infection (e.g., osteomyelitis, cellulitis)
- Direct inoculation such as plant thorns or nails
- Acute inflammatory process results in migration of WBCs into joint
- Synovial hyperplasia, cartilage damage, and formation of a purulent effusion
- Irreversible loss of function in up to 50%
- Mortality rate reported as high as 11%
Pediatric Considerations |
- Hip infections are most common:
- 50% occur in children <3 yr old
- Infants present with irritability, fever, and loss of appetite
- Older children present with fever, and a limp or refusal to bear weight or use joint
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Etiology
- Risk factors:
- Old age, infancy
- Rheumatoid arthritis and degenerative joint disease
- Intravenous drug user (IVDU), endocarditis
- Females (gonococcal [GC] infection)
- Immunosuppression (AIDS, diabetes, chemotherapy, steroid therapy)
- Repeated joint injections, pre-existing joint diseases, trauma, or prosthesis
- Skin infection, cutaneous ulcers
- No bacterial pathogen is identified in 10-20%
- Most common organisms:
- Staphylococcus aureus in adults, hip infections (80%), and patients with rheumatoid arthritis or diabetes
- Multidrug-resistant S. aureus (MRSA) has been noted in some studies to be the most common organism in community-onset adult SA
- Neisseria gonorrhoeae most common in young, healthy, sexually active patients (incidence has decreased over the past decades due to a decrease in the incidence of mucosal GC infections)
- Other pathogens: Group A β-hemolytic and group B, C, and G Streptococci:
- Gram-negative rods (e.g., Pseudomonas aeruginosa, Escherichia coli) in 10% of cases
- Neisseria meningitidis (12% of patients with meningococcal meningitis)
- Common in old age, infancy, immunosuppression, and IVDU (Pseudomonas)
- Anaerobes: Diabetes, prosthetic joints
- Mycobacterial and fungal causes: Atypical (e.g., in advanced HIV); more indolent course
Signs and Symptoms
- Presents abruptly as a single painful, swollen, warm, tender joint
- Common findings include:
- Fever
- A separate source of infection (e.g., skin)
- Extremely painful joint motion in all planes and restricted movement
- A joint effusion (less evident in sacroiliac, hip, and shoulder)
- Any joint can be involved:
- Typically a single joint is involved
- Most commonly knee, then hip, shoulder, and ankle
- Commonly seen in IVDUs: Sacroiliac costochondral and sternoclavicular joints:
- Vertebral involvement such as lumbar facets possible
- Human and animal bites, plant thorns, local steroid therapy, and trauma may lead to infection in atypical locations
- Polyarticular involvement in 10-20%:
- Mostly with rheumatoid arthritis; delay in diagnosis from low suspicion and more subtle presentations (fever in only 50%)
- Patients with sepsis
- GC SA features:
- Develops in 1-3% of untreated gonorrhea and in 42-85% of disseminated GC infection
- Typically monoarticular but commonly polyarticular
- Migratory polyarthralgia, tenosynovitis (present in 20% of patients with arthritis), and dermatitis:
- Involves small joints (e.g., fingers, wrist, elbow, ankle)
- Signs of urethral or vaginal GC infection may be present
- Painless maculopapular lesions on trunk, arms, legs, and around affected joint
Essential Workup
Arthrocentesis
- Perform joint aspiration in any suspected case
- Send fluid for protein and glucose, cell count, Gram stain, and culture
- Typical SA findings:
- A turbid, purulent, or serosanguineous fluid
- A leukocytosis (usually 50,000-150,000/mm3) with a polymorphonuclear predominance (>75%); lower WBC may be seen in GC SA
- Often a decreased glucose and elevated protein level
- Appearance of crystals does not rule out SA
- Use special stain or culture media when indicated (e.g., GC, anaerobes, fungus, mycobacterium)
- Intra-articular lidocaine reduces the sensitivity of subsequent cultures; immediate emptying of aspirated sample into a blood culture flask increases the yield
- In non-GC SA, Gram stain and culture are positive in 50% and 90% of cases, respectively:
- Drops to nearly 10% and 50% in GC SA, respectively
- Real-time PCR can detect bacterial pathogen DNA in many culture-negative aspirates
- Fluoroscopic, sonographic, or CT guidance can be used in technically difficult aspirations
- CT scan and MRI may aid in the diagnosis for joints such as the sacroiliac joint
- Arthrocentesis is contraindicated whenever there is an underlying joint prosthesis or an overlying skin infection:
- If cellulitis present, use an alternate approach through normal skin
Diagnostic Tests & Interpretation
Lab
- Nonspecific serum leukocytosis (more common in children), left shift, and C-reactive protein (CRP) and ESR elevation are usually present
- Procalcitonin can be a helpful aid to rule in rather than rule out SA (pooled negative likelihood ratio of 0.49)
- UA and culture can reveal a urologic source for the pathogen
- Blood cultures may be useful: Positive in 50-70% of non-GC SA
- Culture any potential focus of infection (pharynx, urine, cervix, or anus), particularly when suspecting GC
Imaging
- Plain radiographs to identify:
- Effusion
- Baseline status of the joint
- Contiguous osteomyelitis
- Concurrent rheumatologic diseases
- Fractures or foreign body
- Joint loosening (a late nonspecific sign)
- US, CT, and MRI are more sensitive:
- US may be used to guide aspiration of some joints (e.g., hip) and to detect joint effusions
- Scintigraphic techniques are sensitive and specific in diagnosis of SA. However, they are often not available through ED
- Other tests:
- Bacterial DNA amplification techniques in rapid detection and identification of organisms
Differential Diagnosis
- Viral arthritis
- Rheumatoid arthritis
- Gout or pseudogout
- HIV-associated arthritis
- Reactive arthritis
- Lyme disease
- Osteomyelitis
- Endocarditis
- Septic bursitis
- Trauma
- In children:
- Juvenile idiopathic arthritis
- Slipped capital femoral epiphysis
- Legg-Calve-Perthes disease
- Metaphyseal osteomyelitis
- Transient synovitis
Pediatric Considerations |
- Because of vaccine, Haemophilus influenzae is no longer the most common agent
- S. aureus is most common
- Group B Streptococcus, enterobacteria, and gram-negative rods in the newborn
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Prehospital
No specific considerations
Initial Stabilization/Therapy
- Patient may be septic and require resuscitation
- If patient is toxic, do not delay antibiotics for aspiration results
ED Treatment/Procedures
- Promptly aspirate joint fluid
- Obtain cultures
- Start empiric antibiotics based on Gram stain (if available) and age group or risk factors - consider staphylococcal, streptococcal, and gram-negative coverage; and MRSA in the appropriate setting. Recommended duration of treatment is 2-4 wk. Intra-articular antibiotics are contraindicated
- No risk factors for atypical organisms:
- Gram stain with gram-positive cocci; empiric vancomycin 15-20 mg/kg/dose IV q8-12h
- For methicillin-sensitive S. aureus (MSSA) nafcillin 1-2 g q6h IV (peds: 50-100 mg/kg/d divided q6h max 12 g/d)
- If penicillin allergic, clindamycin 600 mg q8h IV or second- or third-generation cephalosporin IV
- High risk of gram-negative sepsis (elderly, frail, recurrent UTI, and recent abdominal surgery):
- Second- or third-generation cephalosporin for example, ceftriaxone 2 g per day IV (peds: 50-100 mg/kg/d IV divided q12-24h max 4 g/d) or ceftazidime 2 g q8h IV (90-150 mg/kg/d divided q8h; max 6 g/d)
- Gram stain may influence antibiotic choice
- MRSA risk (known MRSA, recent inpatient, nursing home resident, leg ulcers or catheters, or other risk factors determined locally):
- Vancomycin IV + second- or third-generation cephalosporin IV
- Suspected gonococcus or meningococcus:
- Ceftriaxone IV or similar
- Dependent on local policy or resistance
- IVDUs: Discuss with infectious disease (ID) consultant
- ICU patients, known colonization of other organs (e.g., cystic fibrosis): Discuss with ID consultant
- Early orthopedic consultation to evaluate eligibility for surgical drainage
- Pain control: Narcotics and moderately flexed splinting
- Immunologic therapies are experimental
- Prosthesis: Some may try to preserve the limb unless it is loose on plain films
- Patients should be at rest with joint maintained in optimal position to prevent damage
Medication
- Ceftazidime: 1-2 g IV q8h; peds 90-150 mg/kg/d divided q8h; max 6 g/d
- Cefotaxime: 2 g IV q8h; peds: 100-200 mg/kg q8h; max 12 g/d
- Ceftriaxone:2 g IV per day; peds: 50-100 mg/kg/d IV divided q12-24h max 4 g/d
- Nafcillin: 2 g IV q4h; peds: 50-100 mg/kg/d divided q6h max 12 g/d
- Vancomycin: 15-20 mg/kg/dose IV q8-12h
Pediatric Considerations |
- Open surgical drainage is the method of choice in pediatric hip SA
- Cover H. influenzae type B if prior immunization cannot be established
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Disposition
Admission Criteria
- All patients with suspected SA should be admitted until SA is ruled out
- May undergo drainage of joint, as indicated, by serial aspirations, arthroscopy, or arthrotomy
Discharge Criteria
Cases where suspected SA has been adequately ruled out