Does an Anterior-Lipped Tibial Insert Adequately Substitute for a Post-Cam Articulation in Total Knee Arthroplasty

Newer tibial inserts with enhanced conformity (cruciate stabilizing anterior lip; CS) to obviate the need for a posteriorly stabilized (PS) post-cam articulation in posterior cruciate ligament-deficient knees have been recently introduced in modern total knee arthroplasty (TKA). The purpose of this study was to evaluate whether clinical and functional outcomes differ in TKA cohorts without a posterior cruciate ligament (PCL) utilizing either CS anterior-lipped or PS post-cam articulation.

Prospectively collected outcomes were compared in matched cohorts of modern TKAs implanted with either CS anterior-lipped tibial inserts or PS post-cam articulations. The PCL was resected in all knees. Modern Knee Society Scores (objective, function, and satisfaction scores), walking and stair pain, EuroQol five dimensions (EQ-5D) health-related quality of life, and UCLA activity level were assessed at minimum one-year follow-up.

Forty-three anterior-lipped and 39 PS TKAs were matched on sex, age, BMI, and ASA classification at the time of surgery and months of follow-up. CS knees had significantly higher preoperative function scores than PS knees (p = 0.033), but both groups had equivalent function scores at minimum follow-up of one-year (p = 0.687). Eight-one percent of patients in each group reported being satisfied or very satisfied with their TKA (X2 = 0.072, p = 0.964).

This study supports the hypothesis that an anterior-lipped insert is an adequate functional substitute for a post-cam articulation in patients undergoing TKA with PCL excision. These findings suggest that a PS post-cam articulation may not be necessary given the introduction, availability, and clinical performance of anterior-lipped and more conforming tibial bearings. Further study and longer term follow-up is warranted.