SHort Interval Full Two-stage Implant Exchange

Inclusion Criteria: Prospective group: * Patient over 18 years old * Patient managed for a definite osteoarticular infection in a hip or knee prosthesis according to EBJIS definitions (2021) Clinical definition : fistula communicating with the prosthesis, prosthesis exposed / Or biological ≥ 2 samples positive for the same microorganism / And/ or 3000 leukocytes or \> 80% of PNN on the synovial fluid / Or histological: visible microorganism, \> or = 5 PNN on 5 HPN * Patient with an indication for 2-stage surgery: A Impossibility of conservative treatment : infection occurring more than 4 weeks after prosthesis implantation, fistula, documented resistant germ, loosened prosthesis / B Unsuitable 1-stage change: recurrence after 1-stage management, precarious bone capital, documented resistant microorganism, infection without prior microbiological documentation, fistula, surgeon's assessment in disfavor \- Effective contraception during the research period for fertile women of childbearing age Retrospective group : * Patient managed before 31/12/2021 for a definite osteoarticular infection in a hip or knee prosthesis according to EBJIS definitions (2021) Clinical definition : fistula communicating with the prosthesis, prosthesis exposed Or biological ≥ 2 samples positive for the same microorganism And/ or 3000 leukocytes or \> 80% of PNN on the synovial fluid Or histological: visible microorganism, \> or = 5 PNN on 5 HPN * Patient managed by 2 "long" stage surgery with reimplantation time \> 6 weeks with an evolutionary follow-up of at least 15 months after the end of antibiotics Exclusion Criteria: Prospective group : * Indication for conservative treatment, 1-stage or 2 long stage surgery * Reimplantation by another surgical approach requiring complete skin closure of the initial scar * Other surgeries scheduled within 30 days of removal * Participation in another interventional treatment study and/or in an exclusion period due to participation in another protocol * Subject not affiliated with a social security plan or beneficiary of such a plan * Failure to obtain written informed consent * Patient with a legal protection measure (guardianship, curatorship) * Patient under justice safeguard * Pregnant or breastfeeding woman Retrospective group : \- Refusal to participate Study exit criteria * Bacteriological samples positive for fungi * Infection not retained after analysis of samples (no sufficient clinical or biological criteria according to EBJIS definition) * Withdrawal of consent