Does spacer type influence bone lysis and clinical outcomes? A comparative analysis in two-stage revision for periprosthetic knee infection

BACKGROUND: Periprosthetic joint infection (PJI) following total knee arthroplasty remains a serious complication associated with substantial morbidity and complex surgical management. Two-stage revision arthroplasty is widely accepted as the gold standard treatment, in which an antibiotic-loaded cement spacer is used during the interim period to maintain joint space and deliver local antimicrobial therapy. While previous studies have compared static and articulating spacers, limited data are available regarding the impact of handmade versus prefabricated spacers on radiological bone loss and functional outcomes. METHODS: This retrospective observational study included 23 patients who underwent two-stage revision surgery for knee PJI between 2011 and 2024. PJI was diagnosed according to the 2018 International Consensus Meeting (ICM) criteria. Patients were divided into two groups based on spacer type: handmade static vancomycin-loaded spacers (n = 14) and prefabricated articulating gentamicin-loaded spacers (n = 9). Clinical outcomes (reinfection, complications), functional outcomes (range of motion [ROM], WOMAC score, ambulation status), and radiological parameters (bone lysis, joint space gap measurements, and AORI classification) were compared between groups. Statistical analyses were performed using nonparametric tests, with significance set at p < 0.05. RESULTS: Reinfection rates were higher in the handmade spacer group (28.6%) compared with the prefabricated group (11.1%), although the difference was not statistically significant. Radiological analysis suggested greater femoral and tibial bone lysis in the handmade spacer group, reflected by significantly higher AORI scores (femoral p = 0.005; tibial p = 0.002). Functional outcomes favored the prefabricated spacer group, with significantly improved postoperative ROM (p = 0.007) and WOMAC scores (p = 0.038). Independent ambulation was achieved more frequently in the prefabricated spacer group (77.8% vs. 21.4%, p = 0.019). Complication rates, including spacer failure and salvage procedures, were also higher in the handmade spacer group. CONCLUSION: In this retrospective cohort, the clinical pathway involving prefabricated articulating gentamicin-loaded spacers was associated with less radiological bone loss and improved functional outcomes compared with handmade static vancomycin-loaded spacers during two-stage revision for knee PJI. However, given the limited sample size and retrospective design, these findings should be interpreted cautiously and require confirmation in larger prospective studies.