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.