IS THE ANTERIOR MINIMALLY INVASIVE HIP APPROACH (AMIS) ASSOCIATED WITH A HIGHER RATE OF POLYMICROBIAL INFECTIONS COMPARED TO THE OTHER SURGICAL APPROACHES?

Aim The direct anterior minimally invasive approach (AMIS) for total hip arthroplasty (THA) is gaining increasing popularity due to its lower invasiveness compared to other traditional surgical approaches. The aim of the study is to compare the pathogens causing periprosthetic joint infections (PJI) in THAs implanted via AMIS with those causing infections in THA implanted via other approaches. Method All consecutive patients, treated for early or delayed onset periprosthetic hip infection in our hospital from 2011 to the present were selected. Both PJI after THA and hemiarthroplasties (HA) were included. Only pathogens isolated from synovial fluid and intraoperative tissue cultures were included in the analysis. Late infections or those with hematogenous etiology, as well as pathogens isolated via wound swab, were excluded. Differences in pathogens found and surgical times between the AMIS group and the non-AMIS group were analyzed using Fisher's exact test and Student's t-test, respectively. Results Twenty-one patients were included, 10 men and 11 women, with an average age of 78 years, 7 with PJI after HA and 14 after THA. All HAs were implanted via the direct lateral approach, while the THAs were implanted as follows: 9 via AMIS, 2 via posterolateral approach, and 3 via direct lateral approach. The most frequently isolated pathogens were: 7 S. aureus , 7 coagulase-negative staphylococci, and 3 P. aeruginosa . In 4 cases, all from the AMIS group, polymicrobial infections were found (p=0.02). Gram-negative bacteria were more frequent in the non-AMIS group. No significant differences were found in surgical times between THAs implanted via AMIS and those implanted via other approaches, but the duration of HA surgeries was, as expected, shorter than that of THA surgeries. Conclusions Recent literature has shown that infections in THAs implanted via AMIS present a characteristic flora. Our study confirms these findings, highlighting a higher number of polymicrobial infections in the AMIS group. These results should be confirmed in larger cohorts and exclusively of THA cases to avoid confounding factors related to the longer surgical duration of THAs compared to HAs (p=0.01).