UKA IS ASSOCIATED WITH A LOWER RISK FOR PJI AND A HIGHER SUCCESS RATE OF INFECTION TREATMENT COMPARED TO TKA

Introduction & Aim Periprosthetic joint infection (PJI) is one of the most devastating complications, with an incidence rate of around 2% after total knee arthroplasty (TKA). According to different arthroplasty registries, PJI is the most common reason for a revision surgery of TKA. The major concern related to unicompartmental knee arthroplasty (UKA) compared to TKA is the inferior long-term survival reported. Some novel cohort studies report that UKA is associated with a lower risk of PJI compared to TKA, but none of the studies available compared the success rate of PJI treatment after UKA and TKA. The present study aimed to compare the risk for PJI within first 2 years after UKA and TKA. Methods We retrospectively analyzed a consecutive cohort of patients between 2010 and 2023 having cemented UKA or TKA at a high-volume orthopaedic hospital. For each procedure, the demographic data about the patient, date of primary arthroplasty, date of revision surgery, reason for revision surgery, date of death, and date of last follow-up were collected prospectively. The primary outcome was revision due to PJI within first 2 years after the surgery. The definite diagnosis of PJI was based on the EBJIS definition. The rate of PJI in the UKA and TKA was compared. Results In total, 1,492 cemented, fixed-bearing UKA and 8,007 cemented TKAs were included. UKA and TKA subgroup were similar age, sex distribution and BMI. Among UKAs, we identify 6 PJI (0.5%), while 121 PJI (1.5%) among TKAs (p<0.001). Considering UKA PJI, we observed 3 early infections, all successfully cured with debridement, exchange of polyethylene liner, irrigation, and antibiotic course (DAIR). The remaining 3 late infections were successfully cured with one-stage conversion (OSE) to TKA followed by antibiotic treatment. Considering TKA PJI, we observed 39 early PJI and 82 late PJI. Among early TKA PJI, 22 were treated with DAIR and 17 with two-stage implant exchange (TSE) with 4 cases of PJI treatment failure. Among late TKA PJI, 33 were treated with DAIR, 10 with OSE, and 39 with TSE. Among all TKAs, 88% success rate of PJI treatment was observed, 8 failures were observed in the DAIR procedure after late acute PJI, and 7 failures after the TSE protocol, while no failure of OSE. Conclusions Our study shows that UKA is associated with lower risk for PJI than TKA. Furthermore, we also observed a higher success rate of PJI treatment in UKA compared to TKA.