Functional and quality-of-life outcomes after metal-on-polyethylene articulating spacer implantation for periprosthetic knee infection: a retrospective evaluation of a prospectively collected cohort

This study aims to evaluate functional and quality-of-life (QoL) outcomes in patients with periprosthetic joint infection (PJI) undergoing implantation of a metal-on-polyethylene articulating knee spacer as part of a planned two-stage revision, and to explore preoperative predictors of meaningful postoperative improvement. This was a retrospective observational study including 108 consecutive patients with chronic PJI treated with a metal-on-polyethylene articulating spacer between 2016 and 2020 and followed prospectively for clinical outcomes. QoL and joint-specific function were assessed preoperatively and before planned reimplantation using EQ-5D-5 L, Western Ontario and McMaster University (WOMAC), and Knee Society Score (KSS). Minimum clinically important difference (MCID) thresholds were derived using a distribution-based method. Receiver operating characteristic (ROC) analysis identified baseline predictors of achieving MCID. All outcome measures improved significantly after spacer implantation (p < 0.001), exceeding MCID thresholds for pain and function. The largest EQ-5D-5 L domain gain was for pain/discomfort. Predictive thresholds for achieving MCID were an EQ-5D-5 L index ≤ 0.44 and WOMAC index ≥ 42.5. Female sex was associated with better preoperative and postoperative WOMAC and KSS scores. Metal-on-polyethylene articulating spacers are associated with short-term improvements in pain, mobility, and QoL during the interval between stages of revision for PJI. Patients with poor baseline status may experience the greatest benefit, thereby supporting consideration of avoiding definitive reimplantation (1.5 stage). While these interim results may inform patient selection for leaving the spacer indefinitely, long-term follow-up is required to determine durability.