Obtaining anatomic motion and laxity characteristics in a total knee design

Area of Science:

• Biomechanical Engineering
• Orthopedic Surgery
• Medical Device Design

Background:

• Reproducing normal knee motion is a primary objective in total knee replacement (TKR) design.
• Current TKR designs often fail to achieve the goal of replicating natural knee kinematics.
• Guided Motion (GM) TKR designs were developed to offer more anatomic motion than standard prostheses.

Purpose of the Study:

• To evaluate the kinematic performance of novel Guided Motion total knee designs.
• To compare the motion patterns of GM knees with a standard posterior-stabilized (PS) knee and anatomic knee motion.

Main Methods:

• GM knee designs were created using a computer-aided method, generating bearing surfaces based on desired motion.
• A specialized knee testing machine applied physiological forces (compression, shear, torque) during flexion.
• Neutral path of motion and laxity were measured, adapting ASTM standard Constraint Test protocols.

Main Results:

• Kinematic analysis revealed that GM knees exhibited motion patterns closer to anatomic knee motion.
• Comparison with a standard PS knee demonstrated superior kinematic replication by the GM designs.
• Results were benchmarked against previously determined anatomic motion data from knee specimens.

Conclusions:

• The study provides evidence supporting the potential of GM designs to achieve more anatomic knee motion.
• Further in vitro evaluations using knee simulators or advanced computer modeling are warranted.
• Successful in vivo reproduction of anatomic motion could lead to enhanced clinical outcomes for TKR patients.