Infection is one of the most serious complications after total shoulder arthroplasty (TSA) and a common reason for revision surgery of a TSA. Unlike mechanical failures, periprosthetic joint infections (PJIs) can threaten implant survival and severely impact shoulder function. Understanding the pathogens, diagnostic approach, and treatment strategies is essential for optimal outcomes.

Common Pathogens

Cutibacterium acnes (formerly Propionibacterium acnes)

  • The most frequent cause of shoulder PJIs.
  • Typically presents as a low-grade, indolent infection with pain and stiffness rather than obvious systemic symptoms.
  • Difficult to detect due to slow growth in culture.

Other Organisms

  • Staphylococcus aureus (including MRSA) and coagulase-negative staphylococci cause more acute infections.
  • Gram-negative bacteria are rare but more aggressive when present.

Diagnostic Work-Up

Clinical Signs

  • Pain, stiffness, persistent drainage, or unexplained implant loosening.
  • Fever and redness are less common in shoulder PJIs compared to hip and knee infections.

Laboratory Tests

  • ESR and CRP: May be normal in C. acnes infections.
  • Joint Aspiration: Fluid sent for cell count, differential, and extended culture (14+ days for C. acnes).
  • Intraoperative Cultures: Multiple deep tissue samples taken during revision improve diagnostic accuracy.

Imaging

  • X-rays may show implant loosening.
  • Advanced imaging (CT, MRI with metal artifact reduction) may help but cannot reliably confirm infection.

Treatment Strategies

1. Debridement and Implant Retention (DAIR)

  • Indicated for acute infections (within weeks of index surgery).
  • Involves aggressive irrigation, debridement, and exchange of modular components.
  • Often paired with targeted intravenous antibiotics.

2. One-Stage Revision

  • Removal of implants, debridement, and reimplantation in a single surgery.
  • Considered in select cases with known organisms, good bone stock, and low-virulence infections.

3. Two-Stage Revision

  • Gold standard for chronic or complex infections.
  • Stage 1: Implant removal, extensive debridement, placement of antibiotic spacer.
  • Stage 2: Reimplantation once infection is eradicated (typically after 6–12 weeks of antibiotics).

4. Antibiotic Suppression

  • Used in patients who are poor surgical candidates.
  • Involves chronic suppressive oral antibiotics but does not eradicate infection.

Summary Table

StrategyIndicationProsCons
DAIRAcute, early infectionsPreserves implants, shorter recoveryHigh recurrence if delayed
One-Stage RevisionKnown low-virulence organismSingle surgery, faster rehabHigher reinfection risk in complex cases
Two-Stage RevisionChronic, unclear or resistant casesHighest eradication ratesTwo surgeries, longer recovery
Antibiotic SuppressionMedically frail patientsNon-invasive optionInfection persists, risk of flare

Frequently Asked Questions

1. Why is C. acnes so difficult to diagnose?
It grows slowly and often requires cultures to be held for at least two weeks. Standard tests may appear normal.

2. How successful is two-stage revision?
Success rates for infection eradication are typically 80–90%, making it the most reliable approach for chronic infections.

3. Can antibiotics alone cure the infection?
Rarely—antibiotics can suppress symptoms but usually cannot clear an established periprosthetic infection without surgery.

4. What happens if infection recurs after revision?
Options include repeat revision, long-term suppression, or salvage procedures such as resection arthroplasty.

5. Are infections more common in shoulder replacements than hips or knees?
The overall infection rate is lower, but the prevalence of C. acnes makes diagnosis more challenging.