Personalized Robotic-Assisted Total Knee Arthroplasty with Anatomo-Functional Implant Positioning for Varus Knees: A Minimum Follow-Up of 5 Years

Background/Objectives: Some personalized alignment (PA) concepts have been described with symmetrical gaps in extension and flexion. However, laxity in native knees was significantly greater laterally than medially with respect to both extension and flexion. We hypothesized that a personalized alignment can restore the native knee alignment, keep a satisfying patellar tracking, and obtain physiological ligament balancing, that is, a symmetric gap in extension and an asymmetric gap in flexion. We aimed to assess: (1) the postoperative alignment of TKA and postoperative patellar tracking (primary outcome); (2) the ligament balancing at the end of the surgery; and (3) clinical outcomes and complication rates. Methods: In this single-center, retrospective case series, we evaluated 45 patients in a consecutive series who underwent robotic-assisted primary TKA using PA between January and September 2020 with a minimum follow-up of 5 years. Complication was defined as grade ≥3 according to the Clavien-Dindo classification. Data assessed were: TKA alignment and implant positioning on postoperative radiographs, patellar tracking on the merchant view, and ligament balancing in extension and flexion upon completion of surgery. Results: Mean follow-up was 62.1 ± 2.5 months. The postoperative mean HKA angle was 177.4° ± 2.2. The medial distal femoral angle was restored (91.1° ± 1.5 postoperatively versus 91.3° ± 2). A total of four TKAs had a patellar tilt superior to 5° (8.9%). No significant difference was found in the medial gap laxity—both in extension and in flexion—and the lateral gap laxity in extension. The lateral gap laxity in flexion was significantly higher than extension or medial gap laxity (+2.9 mm). One patient was readmitted for delayed wound healing. Average improvements in Knee Society knee and function scores were 55.86 and 51.84 points, respectively. Conclusions: This personalized alignment technique using anatomo-functional implant positioning allowed restoration of native knee alignment with a “safe zone” (3° varus/valgus) for the tibial implant, maintained satisfying patellar tracking, and restituted the asymmetrical gap laxity in flexion with a higher laxity in the lateral compartment. Being the longest system-specific study to date, the results are encouraging at 5 years with no major complications. However, longer follow-up will be required to confirm the use of this technique.