What is the treatment for septic arthritis of the shoulder?

Treatment of Septic Arthritis of the Shoulder

Septic arthritis of the shoulder requires immediate surgical debridement combined with intravenous vancomycin, followed by 3-4 weeks of antibiotic therapy tailored to culture results. 1, 2

Initial Assessment and Diagnosis

Determine if this is a surgical emergency based on clinical presentation:

• Surgical emergencies (severe systemic toxicity, meeting SIRS criteria, rapidly progressive symptoms) require immediate surgical debridement with intraoperative cultures 1, 3
• Non-emergencies should proceed with joint aspiration first 1

Obtain joint aspiration for definitive diagnosis:

• Synovial fluid white blood cell count ≥50,000 cells/mm³ is suggestive of septic arthritis, though 57% of shoulder aspirates may show counts below this threshold 1, 4
• Culture is positive in approximately 80% of non-gonococcal cases 1, 2
• Send fluid for Gram stain, culture, cell count, and crystal analysis 3

Obtain blood cultures before initiating antibiotics 3

Consider MRI before surgery in select cases:

• MRI helps classify infection severity: Type I (confined to glenohumeral joint), Type II (extra-articular extension), or Type III (concomitant osteomyelitis) 4
• Concomitant osteomyelitis occurs in up to 30% of cases and requires longer treatment 1, 2, 3
• MRI is particularly useful when clinical suspicion remains high despite negative joint aspiration 1

Surgical Management

All shoulder septic arthritis cases require surgical intervention:

• Open debridement is the standard approach for shoulder infections, as arthroscopic management alone is typically insufficient 5
• Arthrotomy, irrigation, and debridement are the standard surgical interventions 1, 2
• Patients require an average of 2.2 surgical debridements to eradicate infection 4
• Obtain intraoperative cultures during debridement 1, 3

For prosthetic joint infections:

• Device removal is recommended 2
• If removal is not possible, chronic suppression with appropriate antibiotics is necessary 2

Antibiotic Therapy

Empiric therapy (start immediately after obtaining cultures):

• IV vancomycin 15 mg/kg every 6 hours (or 30-60 mg/kg/day in 2-4 divided doses) is first-line for adults 1, 2, 3
• This covers MRSA, which is increasingly common in septic arthritis 1, 3

Culture-directed therapy (adjust based on results):

• For MRSA: Continue vancomycin; consider adding rifampin 600 mg daily or 300-450 mg twice daily for enhanced bone and biofilm penetration 1, 2
• For MSSA: Switch to nafcillin, oxacillin, or cefazolin 1
• For Streptococcal infections: Use penicillin G or ceftriaxone 1
• For polymicrobial infections: Dual antibiotic coverage is mandatory (e.g., linezolid for MRSA plus ciprofloxacin for Pseudomonas) 1

Special pathogen considerations for shoulder:

• Propionibacterium species are seen only in shoulder infections, not other joints 5
• Shoulder infections more commonly result from hematogenous spread compared to knee infections 5

Duration of therapy:

• 3-4 weeks for uncomplicated septic arthritis 1, 2, 3
• Longer courses required if concomitant osteomyelitis is present 1, 2, 3
• For prosthetic joint infections: 12 weeks shows better outcomes than 6 weeks 1, 2

Transition to oral antibiotics:

• Can switch after 2-4 days if clinically improving, afebrile, and tolerating oral intake 1
• Oral antibiotics are not inferior to IV therapy for most cases 1
• Options for MRSA include linezolid 600 mg PO every 12 hours or TMP-SMX plus rifampin 1

Monitoring and Follow-up

Monitor treatment response with:

• Serial CRP and ESR to assess inflammatory markers 3
• Clinical improvement in pain, range of motion, and systemic symptoms 3
• Resolution of SIRS criteria before considering discharge 3

Expected outcomes:

• Remission rates of 90% for shoulder septic arthritis 5
• Mortality rate of 10% in shoulder infections (higher than knee) 5
• Only 50% of patients return to their previous level of activity 5
• Significant reduction in shoulder function should be expected compared to other joints 5
• Mean Constant Score of 66.6 at follow-up 5

Critical Pitfalls to Avoid

Do not rely solely on synovial fluid cell counts:

• 57% of shoulder aspirates show counts below the standard 50,000 cells/mm³ cutoff 4
• Negative joint aspirate culture does not rule out infection 1, 2

Do not use arthroscopy alone:

• Unlike knee infections, shoulder septic arthritis always requires open debridement 5
• Multiple debridements are often necessary 4

Do not miss concomitant osteomyelitis:

• Occurs in up to 30% of cases and requires longer antibiotic courses 1, 2, 3
• Consider MRI if clinical suspicion is high 1, 3

Do not delay treatment in high-risk patients:

• Patients with rheumatoid arthritis on immunotherapy require special attention and are at higher risk for complications 6
• Age and time between symptom onset and diagnosis are significant risk factors for more severe infection 4
• Body mass index is the only risk factor for recurrence 4

Monitor for drug interactions and adverse effects:

• Particularly important in elderly patients on multiple medications 1
• Adjust vancomycin dosing based on trough levels 1