Chronic infections of knee megaprostheses: are “Off-Label” DAIR-Plus or partial two-stage exchange viable options?

Introduction: Two-stage revision for chronic periprosthetic joint infections (PJI) of knee megaprostheses is complex and often results in significant bone loss. DAIR-Plus and other partial exchange procedures, involving debridement with partial prosthesis removal but retaining stems, are typically used for acute PJI but may benefit select chronic cases. This study aimed to: (i) assess DAIR-Plus and partial two-stage exchange outcomes in chronic megaprosthesis infections; and (ii) identify prognostic factors to guide their use versus full component removal. Materials and methods: Twenty-three patients underwent DAIR-Plus or partial two-stage exchange (PTSE) procedures for chronic knee megaprosthetic PJI between 2000 and 2022. Nineteen patients, were included. Targeted antibiotics were administered based on Infectious Disease Specialist recommendations. Infection eradication was evaluated using clinical and serologic parameters. Results: Nineteen patients (mean age 53.4 years) underwent 13 DAIR-Plus and 7 PTSE. PJI-free survival was 57.9% at 1 year, 47.4% at 2 and 5 years, and 42% beyond 5 years. Among failures, 6 had persistent infection and 5 relapsed (mean time to relapse: 13.75 months). Four additional patients achieved infection control after further two-stage revisions; 7 remained uncontrolled, leading to 6 amputations and 1 chronic suppressive treatment. Outcomes did not differ significantly by age, gender, host status, oncological history, radiotherapy, or surgical approach. Staphylococcus spp. caused 63% of infections and were associated with significantly lower PJI-free survival at final follow-up (25% vs. 62% for other organisms, p= 0.048). Conclusions DAIR-Plus provided lasting infection control in selected chronic PJI cases, with nearly half remaining infection-free long term with notable advantages such as bone stock preservation and faster recovery. Partial two-stage exchange does not appear to offer additional advantages over DAIR-Plus. Outcomes: were not influenced by clinical factors, but Staphylococcus spp. infections showed significantly lower success.