The Effect of the Design of Polyethylene Inserts in Total Knee Arthroplasty on Patient Reported Outcomes.

Introduction: Several types of polyethylene liners have been developed to address the specific needs of patients' anatomy within total knee arthroplasty (TKA). In modern TKA, the posterior-stabilized (PS) and the cruciate-retaining (CR) designs are the most common, with the medial congruent (MC) design becoming more popular. The MC total knee arthroplasty has a posterior dwell point allowing for more flexion. The purpose of this study was to determine differences in patient-reported outcomes (PROMs) or postoperative outcomes between these three TKAs.

Methods: Patients who underwent a primary, elective, unilateral TKA between June 2021 and July 2023 were identified. Demographics and perioperative and postoperative outcomes were extracted from the medical record. PROMs from 624 patients were obtained through a digital engagement platform. A P value ≤0.05 was considered statistically significant.

Results: Patients were subdivided into three groups; 111 PS-TKA, 278 CR-TKA, and 235 MC-TKAs. Most implants were Zimmer (71.5%) and were cemented (92.9%). Patients in the CR group were predominantly male (P = 0.003) and had a lower body mass index (P < 0.001). No differences were seen in Knee Injury and Osteoarthritis Outcome Score for Joint Replacement scores at any time point (preoperative: P = 0.073; 12 weeks: P = 0.144; 6 months: P = 0.666; 1 year: P = 0.622). A similar percentage of patients met the minimal clinically important difference (P = 0.480), and Forgotten Joint Scores were equivalent (P = 0.930). Patient physical therapy parameters (Timed Up and Go test [P = 0.779] and ambulation distance [P = 0.103]), inpatient pain levels (at rest: P = 0.101, with activity: P = 0.052), or morphine milligram equivalents dosed (P = 0.608) were comparable. No differences were seen in 30-day complications.

Conclusion: This study fails to demonstrate a difference in PROMs, functional parameters, or complications between the PS-TKAs, CR-TKAs, and MC-TKAs. All three constructs perform similarly in the immediate postoperative period. Because equivalent outcomes occur with each polyethylene, implant choice should be left to physician preference.