Robotic-assisted "physiological alignment" TKA with a 3-degree varus inclination does not affect gait ability, regardless of pre-arthritic CPAK classification matching.

Background: Traditionally, the hip-knee-ankle (HKA) angle has been used as an indicator of lower limb mechanical alignment to predict postoperative outcomes in total knee arthroplasty (TKA). However, patients with knee osteoarthritis exhibit considerable individual variation in coronal plane alignment of the lower limb. The Coronal Plane Alignment of the Knee (CPAK) classification was introduced as a novel method to reflect these individual alignment characteristics. Nevertheless, it remains inconclusive whether aligning the lower limb to the patient's native CPAK phenotype before and after TKA leads to improved outcomes. Objective: The purpose of this study is to investigate the impact of postoperative CPAK phenotypes and the changes from pre-to postoperative states on gait in robotic-assisted (RA) bi-cruciate stabilized (BCS) TKA using an asymmetric prosthesis aimed at achieving functional alignment (FA). Participants: and Setting: This retrospective, single-surgeon, consecutive cohort study included 46 patients who underwent RA-BCS TKA. Methods: Pre- and postoperative CPAK classifications were compared, and changes in the arithmetic hip-knee-ankle angle (aHKA), joint line obliquity (JLO), and gait analysis scores were evaluated both preoperatively and one year postoperatively. Results: No significant differences were observed between the two groups in preoperative or postoperative walking ability, or in the postoperative changes in gait parameters. Conclusions: RA-BCS TKA using physiological alignment and an asymmetric prosthesis with a built-in 3° varus inclination demonstrated no significant differences in walking ability, regardless of the prearthritic CPAK classification. Level of evidence: Level Ⅲ.