Impact of Spacer Constraint on Outcomes in Two-Stage Exchange Revision Total Knee Arthroplasty.

Background: A two-stage revision has long been the gold standard for chronic periprosthetic joint infections, with real-component articulating spacers becoming overwhelmingly popular. Although several studies have evaluated the success of these spacers in revision total knee arthroplasty, to our knowledge, this is the first to specifically compare outcomes of spacers stratified by the level of liner constraint.

Methods: This retrospective analysis reviewed 135 patients who were indicated for two-stage revision total knee arthroplasty due to periprosthetic joint infections between 2011 and 2023 at a single specialty urban academic institution. Patients were categorized into three groups based on the polyethylene liner constraint used during the first stage: cruciate retaining (CR), posterior stabilized (PS), and varus-valgus constrained (VVC). Of these 135 patients, 60 patients (44%) were categorized in the CR group, 47 patients (35%) were in the PS group, and 28 patients (21%) were in the VVC group. These groups were compared after each stage for perioperative and postoperative outcomes such as operative time, length of stay, discharge disposition, knee range of motion (ROM), as well as incidence of rerevision and reinfection.

Results: The mean postoperative length of stay was not different among cohorts for both stages. Operative time was significantly longer in the VVC group after the second stage (P = 0.007), while there was no difference after the first stage (P = 0.085). There were no differences in ROM after both stages. The mean ROM after the first stage was 92° in the CR group, 90° in the PS group, and 85° in the VVC group (P = 0.46). After the second stage, ROM was 101° in both the CR and VVC groups and 107° in the PS group (P = 0.28). There were no differences in the risk of rerevision due to reinfection across the groups after the first or second-stage procedures. The reinfection incidence after the first stage was 14% in the VVC group, compared to 5% in the CR group and 4% in the PS group (P = 0.14). After the second stage, the reinfection risk was 21% in the VVC group, 8% in the CR group, and 13% in the PS group (P = 0.21).

Conclusions: No significant differences were observed in the risk of complications such as reinfection, rerevisions, and postoperative ROM, suggesting that the choice of liner constraint in two-stage revision can be left up to surgeon's discretion.