Patient-specific implants with custom cutting blocks better approximate natural knee kinematics than standard TKA without custom cutting blocks

•Patient dissatisfaction after TKA is linked to improper alignment and placement of implants.•Restoration of normal kinematics of knee is not achieved using off-the-shelf implants and traditional instruments.•A patient-specific implant along with customized instruments recreates kinematics, which is closer to the natural knee.

BackgroundNearly 14% to 39% TKA patients report dissatisfaction causing incomplete return of function. We proposed that the kinematics of knees implanted with patient-specific prostheses using patient-specific cutting guides would be closer to normal.MethodsEighteen matched cadaver lower limbs were randomly assigned to two groups: group A was implanted with patient-specific implants using patient-specific cutting guides; group B, the contralateral knee, was implanted with a standard design using intramedullary alignment cutting guides. Knee kinematics were measured on a dynamic closed-kinetic-chain Oxford knee rig, simulating a deep knee bend and in a passive rig testing varus–valgus laxity.ResultsThe difference from normal kinematics was lower for group A compared to group B for active femoral rollback, active tibiofemoral adduction, and for passive varus–valgus laxity.ConclusionsOur results support the hypothesis that knees with patient-specific implants generate kinematics more closely resembling normal knee kinematics than standard knee designs.Clinical RelevanceRestoring normal kinematics may improve function and patient satisfaction after total knee arthroplasty.