Retained articulating spacers (1.5 stage) in chronic knee periprosthetic joint infections: an analysis of associate factors and outcomes in a single center cohort of patients.

Abstract

Background: Two-stage revision remains the gold standard for chronic periprosthetic joint infection (PJI), but it can significantly impact patients' quality of life and functional recovery. The 1.5-stage revision, involving indefinite spacer retention, has emerged as a potential alternative in selected high-risk patients. Our questions were: (1) What are the early functional outcomes, including their infection-free survival? (2) Which pre- and perioperative factors are associated with spacer retention? and (3) What is the mechanical survivorship of retained spacers?

Materials and methods: This was a retrospective observational study including 108 consecutive patients with chronic PJI between 2016 and 2020 who were followed prospectively for clinical outcomes. Functional status and quality of life were assessed using the EuroQol-5-Dimension-5-Level (EQ-5D-5L), Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC), and Knee Society Score (KSS) before spacer placement and prior to scheduled reimplantation. Infection-free status was defined as the absence of clinical, radiographic, and laboratory signs of infection recurrence over a 24-month follow-up. Univariate and multivariate logistic regression were used to identify factors associated with spacer retention.

Results: All patients initially underwent articulating spacer implantation as part of a planned two-stage protocol. Subsequently, after shared decision-making, the spacer was retained indefinitely ("retained articulating spacer," commonly referred to as "1.5-stage") in 43 patients (39.8%), while 65 patients proceeded to reimplantation (two-stage revision). The KSS, WOMAC, and quality of life (QoL) scores, before scheduling the revision, were better than preoperative ones (p < 0.001). An age over 75 years (odds ratio [OR] 4.216, p = 0.001), a lower postoperative WOMAC score (OR 0.972, p = 0.013), and a history of re-revision (OR 1.102, p = 0.027) were independently associated with 1.5-stage candidacy. Infection-free status was achieved in 91.7% of the overall cohort, with 87.6% success in the two-stage group and 97.7% in the 1.5-stage group. Kaplan-Meier survival analysis showed spacer survivorship of 100% at 24 months, 88.8% at 30 months, and 73.3% at 36 months.

Conclusions: Older age, better early functional outcomes, and a history of multiple surgeries at the same site were associated with spacer retention. These associations may inform patient counseling and surgical decision-making. Level of evidence IV, retrospective cohort study.