Background: The success rates of treating chronic periprosthetic joint infection (PJI) have plateaued in the last two decades utilizing exchange protocols combined with extended parenteral antimicrobials. At the same time, extended systemic antimicrobials carry well-recognized adverse effects, including organ toxicity, metabolic derangements, and disruption of host–microbiome balance, which may themselves impair host inflammatory responses and tissue healing. The defined challenge is to intensify local site eradication while minimizing systemic antimicrobial exposure and its associated host harms. This study introduces a tactical treatment shift focusing on local microbial biocidal treatment, that we aptly name “antimicrobial brachytherapy” protocol (ABP). Methods: A consecutive case series of 25 patients with chronic PJI in total knee arthroplasty (TKA) were treated with the ABP from 2019 to 2023. In brief, the protocol includes: (1) local multimodal antimicrobial therapy applied during debridement to reach and extinguish microbial reserves, (2) eliminating parenteral antimicrobials and limiting oral antimicrobials to 3 weeks, and (3) employing variable explantation times (longer when needed) via a 1.5 exchange technique allowing individualized host and limb rejuvenation. Patients were graded according to McPherson host scoring. Musculoskeletal Infection Society (MSIS) tier levels were used to rate success. All patients had a minimum two-year follow-up. Results: Eighty percent of the patients were significantly compromised, consisting of B and C hosts having 2 and 3 limb scores. Outcomes using the MSIS tier rating show 16/25 (64%) tier 1 success (infection-free without antimicrobial suppression). In these 16 patients, three were still using their 1.5 implant at a mean 4.2 years (2–5.5 years). There were two (8%) tier 3C outcomes (aseptic revision at <1 year), and six (25%) tier 3E failures (amputation, resection arthroplasty or arthrodesis) with four amputations for continued infection, and two who underwent a repeat 1.5 exchange for recurrent infection. Of the four patients amputated, three had fungal microbes identified in post-resection aspirations. Lastly, there was one (4.15%) tier 4a outcome (mortality at <1 year). Conclusions: The ABP concept is a tactical shift focusing antimicrobial therapy within the zone of infection, avoiding long course systemic antimicrobials, and allowing variable explantation time for host and limb rejuvenation. Success was comparable to published MSIS tier 1 outcomes using traditional two-stage exchange protocols with extended parenteral antimicrobials. Given the small sample size and absence of a comparator, the results should be regarded as hypothesis-generating, and require validation in larger, randomized, controlled studies.
McPherson et al. (2026) studied this question.