Achieving More Natural Motion, Stability, and Function With a Dual-Pivot ACL-substituting Total Knee Arthroplasty Design

Abstract

Reports demonstrate up to 20% of total knee arthroplasty (TKA) patients are not satisfied and claim their knee does not feel normal. Failure to replicate native anterior cruciate ligament (ACL)-intact knee tibiofemoral kinematics and stability may contribute to this dissatisfaction. Originally described as medial-pivot pattern throughout flexion, recent studies have elucidated the more modern understanding of a complex motion pattern in ACL-intact knees, where walking and early flexion activities near extension exhibit a lateral-pivot pattern and medial-pivot pattern is observed in deeper flexion. A contemporary TKA design (EMPOWR 3-D; DJO Global, Vista, CA) has the potential to promote natural motion and stability by incorporating a conforming spherical lateral compartment to recreate the dual-pivot kinematics. In vivo fluoroscopic studies have confirmed this optimal kinematic pattern of medial-pivot motion during squatting and kneeling activities, with a lateral-pivot motion during walking. Further, near normal knee strength and minimized hamstrings co-contraction provide evidence for optimal intrinsic tibiofemoral stability. Emerging clinical results have been encouraging and support the modern dual-pivot kinematic understanding and in vivo function studies. Recent studies have revealed intraoperative dual-pivot femoral contact patterns optimize patient outcomes. Clinical results comparing the dual-pivot TKA and a traditional TKA design demonstrate patients with the dual-pivot TKA experience a higher level of function and a greater likelihood of a normal feeling knee. Merging the modern understanding of kinematics in ACL-intact knees with a contemporary dual-pivot TKA design may improve outcomes through optimal knee motion and stability, which may narrow the elusive 20% of TKA patients currently not satisfied.