High Rates of Occult Infection After Shoulder Fracture Fixation: Considerations for Conversion Shoulder Arthroplasty.

BACKGROUND: Existing hardware may contribute to increased risk of bacterial contamination and subsequent periprosthetic joint infection (PJI) in conversion shoulder arthroplasty performed for failed fracture fixation.

QUESTIONS/PURPOSES: This study examined the incidence of positive pre-operative aspiration and inflammatory marker data, along with correlation of pre-operative positive aspiration or inflammatory markers and subsequent infection following conversion shoulder arthroplasty for failed open reduction and internal fixation (ORIF) and the need for re-operation at 4.6-year follow-up.

METHODS: Twenty-eight patients who underwent conversion to shoulder arthroplasty for any reason after fracture fixation were retrospectively reviewed in a single center. A pre-operative aspiration was done in 17 patients; all patients had intra-operative tissue sampling. All procedures were single-stage removal of hardware and performance of the arthroplasty. In cases of pre-operative positive bacterial growth, a single-stage procedure was performed according to the septic ENDO-Klinik protocol.

RESULTS: In 4 of 17 pre-operative joint aspirations, bacterial growth was detected; one pre-operative negative aspiration demonstrated bacterial growth in intra-operative sampling. In three of them, the infection has been validated through intra-operatively results. Pre-operative aspiration showed a sensitivity of 75% and specificity of 92% (p < 0.005) for infection. No post-operative PJIs were observed. Six revisions were performed, most commonly for aseptic loosening (two cases) and conversion of hemiarthroplasty to a reverse design (two cases).

CONCLUSIONS: In conclusion, the risk of low-grade shoulder infection after fracture osteosynthesis may be higher than in hip and knee joints, based on limited study data. Adequate pre-operative testing is recommended to rule out occult shoulder infection in this setting.