Insert conformity variation affects kinematics and wear performance of total knee replacements

Background: The insert conformity is a critical factor for successful total knee replacement which must be considered in design of the implant. However, the effects of conformity on knee kinematics and wear under physiological environment are often neglected in previous studies. The present study involved evaluating the biomechanics and wear performance with regard to different insert conformity in total knee replacement.

Methods: Different tibial inserts with different sagittal and coronal conformity levels were created and analyzed using a previously developed wear prediction framework, coupling a patient-specific musculoskeletal multibody dynamics simulation, finite element and wear analysis. The contact mechanics, kinematics, and wear performance were compared during 10 million cycles of wear simulation.

Findings: The findings revealed that the knee kinematics was affected by sagittal conformity design variables, which further influenced the wear of insert bearing surface. Additionally, kinematics and wear of artificial knee joint were much more sensitive to sagittal than coronal conformity of tibial insert. The lower sagittal conformity designs had lower wear rates, worn area and contact area. In turn, the wear of insert bearing surface also changed insert conformity, and further impacted on knee kinematics.

Interpretation: The present study indicated that the sagittal conformity design of insert surface played a crucial role to improve contact mechanics and kinematics performance and minimize wear of total knee replacement. The optimization of insert conformity should be considered carefully in implant design and surgical procedures.