Mapping Bacterial Biofilm on Explanted Orthopaedic Hardware: An Analysis of 14 Consecutive Cases.

BACKGROUND AND PURPOSE: Hardware implanted during primary total joint arthroplasty (TJA) carries a serious risk for periprosthetic joint infection (PJI). The formation of bacterial biofilms, which are highly tolerant of antibiotics and host immunity, is recognized as being a major barrier to treatment. It is not known if some components and their surface features are more prone to biofilm than others. This study attempted to map biofilm on different components and features of orthopedic hardware recovered during revision.

METHODS: Implant surface culture (ISC) was used on fifty-three components from fourteen hip and knee revisions. ISC achieves a thin agar coating over components, followed by incubation and observation for colony outgrowth over nine days. Recovered organisms were identified by selective culture and 16s rRNA sequencing. Outcomes were compared with clinical culturing and PJI diagnosis based on 2013 Musculoskeletal Infection Society criteria.

RESULTS: ISC paralleled clinical culturing with a sensitivity of 100% and specificity of 57.1%. When compared to MSIS criteria, sensitivity remained at 100% while specificity was 80%. Biofilm accumulation was patchy and heterogenous throughout different prostheses, though notably the non-articulating surfaces between the tibial tray and polyethylene insert showed consistent growth. On individual components, ridges and edges consistently harbored biofilm, while growth elsewhere was case-dependent.

INTERPRETATION: ISC successfully identified microbial growth with a high sensitivity while also revealing that biofilm growth was commonly localized to particular locations. Understanding where biofilm formation occurs most often on implanted hardware will help guide debridement, retention choices, and implant design.