Early Clinical and Radiological outcomes of the New Anatomic Knee System : Minimum 3-year Follow-up.

Abstract

Background: For total knee arthroplasty (TKA), implant design and proper coverage are important for achieving patient satisfaction. An asymmetrical anatomic implant (Persona® knee system, Zimmer Biomet, Warsaw, Indiana) enables accurate coverage and minimal bone cutting. This study aimed to analyze the clinical and radiological outcomes of TKA using an asymmetrical anatomic implant over a minimum 3-year follow-up.Methods: The medical records of 94 patients who underwent 132 TKAs using the Persona® knee system, between April 2015 and January 2016 were reviewed. Pre- and post-operative clinical outcomes (assessed using the International Knee Documentation Committee (IKDC), Western Ontario and McMaster Universities Arthritis Index (WOMAC), and Knee Injury and Osteoarthritis Outcome Score (KOOS) scores, and range of motion (ROM) were reviewed. The mechanical hip-knee-ankle (HKA) axis, component overhang and underhang and presence of a radiolucent line (RLL) were evaluated. Liner thickness were also reviewed.Results: At 3-year follow-up, the mean ROM improved from 108.4° to 130.3°. The mean IKDC subjective, WOMAC and global KOOS score significantly improved from 29.2 to 70.3, from 64.2 to 11.5, and from 66.6 to 21.7, respectively (p<0.0001). The mean mechanical HKA axis indicated the correction of the malalignment (from 9.2° varus to 0.3° varus, p<0.001). The incidence rates of >3-mm bone-to-implant size mismatch were 6.8% and 8.3% for the femoral and tibial components, respectively. RLL was found in seven cases, but they were small (>2 mm) and did not progress. In 36.3% of the knees, the additional liner thickness (11 or 13mm) was used. No case of implant loosening or early failure related to the implant design occurred. Conclusion: TKA using the Persona® knee system improved all the clinical knee scores and ROM without signs of early failure. This knee system also provides more implant size options than the conventional TKA systems and facilitates ligament balancing.