Isolated Tibial Polyethylene Insert Exchange After Total Knee Arthroplasty for Treatment of Instability and/or Polyethylene Wear.

Introduction: Isolated tibial polyethylene insert exchange (ITPIE) as a treatment for instability and polyethylene wear after total knee arthroplasty (TKA) remains controversial with studies reporting varied results. The purpose of this study is to evaluate the survival and outcomes of ITPIE performed for treatment of instability with or without polyethylene wear after TKA.
Materials and Methods: A query of a private practice arthroplasty registry revealed 364 patients (390 knees) treated with ITPIE for instability and/or polyethylene wear after TKA between 1997 and 2019. Mean age was 66.8 years, mean body mass index (BMI) was 33.8 kg/m2, and 59% of patients were female. ITPIE for infection, tibiofemoral aseptic loosening, arthrofibrosis, poor wound healing, and extensor mechanism failure were excluded. All patients had well-fixed and well-aligned components prior to surgery.
Results: Mean follow up was 5.9 years. Knee Society Clinical (KSC) scores improved preoperatively from 55 to 76 postoperatively (p <0.001). Thirty knees (7.7%) required re-revision: 15 (3.8%) for ongoing instability, seven aseptic loosening, three infection, two patellofemoral maltracking, one patellar fracture, one metal allergy, and one revised elsewhere for cause unknown. Kaplan-Meier analysis revealed survival of 93.1% (95% CI: ±1.5%) at five years, 84.7% (95% CI: ±3.5%) at 10 years, and 80.5% (95% CI: ±4.4%) at 21 years.
Conclusions: ITPIE is a reliable treatment for instability and/or polyethylene wear after TKA in the presence of well-fixed and well-aligned components with good survival and clinical improvement. The less invasive nature and reduced risk for bone loss make it an attractive option versus full revision.