Metaphyseal cones in septic revision total knee arthroplasty: A retrospective cohort study with minimum 2-year follow-up.

Purpose: Metaphyseal cones improve fixation and address bone loss in revision total knee arthroplasty (rTKA), but their use in septic revision remains controversial because of theoretical concerns about biofilm formation on porous surfaces, and evidence confined to the septic setting is scarce. We aimed to describe infection eradication, implant survival and functional outcomes and the metaphyseal microbiological environment after cone implantation in septic rTKA. Methods: This multicentre retrospective single-arm cohort study included consecutive patients undergoing septic rTKA with at least one porous tritanium metaphyseal cone at two centres between January 2016 and December 2023. Periprosthetic joint infection was diagnosed by the European Bone and Joint Infection Society (EBJIS) 2021 criteria. In one-stage revisions, an additional metaphyseal bone sample was obtained during reaming for cone implantation. The primary outcome was infection eradication at a minimum 24-month follow-up; infection-free implant survival was estimated by Kaplan-Meier. Secondary outcomes were metaphyseal culture positivity in one-stage patients and functional scores (Knee Society Score [KSS], Western Ontario and McMaster Universities Osteoarthritis Index [WOMAC], EuroQol five-dimension five-level questionnaire [EQ-5D-5L], EuroQol Visual Analogue Scale [EQ-VAS]) at last follow-up. Results: Thirty-four patients (mean age 70.3 ± 8.3 years; 55.9% female) were included: 18 (52.9%) one-stage and 16 (47.1%) two-stage revisions. Median follow-up was 44 months (interquartile range [IQR]: 35-50). Infection was eradicated in 31 patients (91.2%, 95% confidence interval [CI]: 75.1%-97.1%); all three failures occurred by 14 months. Metaphyseal cultures were positive in 12 of 18 one-stage patients (66.7%, 95% CI: 43.7-83.7). Cones were removed in three patients. Median functional scores were KSS Knee 80, KSS Functional 60, WOMAC Physical Function 17 and EQ-VAS 70. Conclusion: In this cohort, cone implantation in septic rTKA was associated with a high infection eradication rate and durable implant survival, with three cone removals. The 66.7% metaphyseal culture positivity in one-stage patients is an exploratory finding that may reflect occult infection or sample contamination and cannot be generalised beyond this subgroup. These findings support cones as a reconstructive option in septic rTKA. Level of Evidence: Level IV.