A Dual-Pivot Pattern Simulating Native Knee Kinematics Optimizes Functional Outcomes After Total Knee Arthroplasty

Abstract

Background

Kinematics after total knee arthroplasty (TKA) have been studied for decades; however, few studies have correlated kinematic patterns to patient reported outcomes. The purpose of this study was to determine if a pattern of lateral pivot motion in early flexion and medial pivot motion in high flexion, simulating native knee kinematics, produces superior clinical outcomes. A second study objective was to determine if a specific kinematic pattern throughout the various ranges of flexion produces superior function and patient satisfaction.

Methods

120 consecutive TKAs were performed using sensor embedded tibial trials to record intraoperative knee kinematics through the full range of motion. Established criteria were used to identify lateral (L) or medial (M) pivot kinematic patterns based on the center of rotation within three flexion zones -- 0 to 45° (early flexion), 45 to 90° (mid flexion) and 90° to terminal flexion (late flexion). Knee Society Scores, pain scores, and patient satisfaction were analysed in relationship to kinematic patterns.

Results

Knee Society function scores were significantly higher in TKAs with early lateral pivot/late medial pivot intraoperative kinematics compared to all other kinematic patterns (p = 0.018) at minimum one-year follow-up. There was a greater decrease in the proportion of patients with early lateral/late medial pivot kinematics who reported that their knee never feels normal (p = 0.011). Higher mean function scores at minimum one-year follow-up (p < 0.001) and improvement from preoperative baseline (p = 0.008) were observed in patients with the most ideal “LLM” kinematic pattern (lateral pivot 0 to 45o and 45 to 90o; medial pivot beyond 90o) compared to those with the least ideal “MLL” kinematic pattern. All patients with the optimal “LLM” kinematic pattern compared to none of those with the “MLL” kinematic pattern reported that they were very satisfied with their TKA (p = 0.003).

Conclusion

Patients who exhibited an early flexion lateral pivot kinematic pattern accompanied by medial pivot motion in later flexion, as measured intraoperatively, reported higher functional outcome scores along with higher overall patient satisfaction. Replicating the dual-pivot kinematic pattern observed in native knees may improve function and satisfaction after TKA. Further study is warranted to explore a correlation with in-vivo kinematic patterns.