Early and Predictable Restoration of Motion Using a "Kinematic Retaining" Total Knee Replacement: A Prospective...

Area of Science:

• Orthopedic surgery
• Biomechanical engineering
• Medical device analysis

Background:

• Total knee replacement (TKR) aims to restore normal knee function.
• New TKR designs focus on improving patient outcomes and joint movement.
• Understanding implant kinematics is crucial for evaluating TKR performance.

Purpose of the Study:

• To quantify the in vivo kinematic characteristics of the Physica KR total knee replacement system.
• To assess knee joint movement during functional activities like step-up, kneeling, and lunging.
• To compare the kinematics of the Physica KR implant to established cruciate-retaining designs.

Main Methods:

• In vivo fluoroscopic analysis of 21 patients 1 year post-Physica KR implantation.
• Assessment of kinematic parameters including rollback, flexion, rotation, translation, and condylar lift-off.
• Evaluation during three defined activities: step-up, kneel, and lunge.

Main Results:

• Mean maximum passive flexion of 115.8 degrees was achieved.
• Congruent joint kinematics were observed throughout the range of motion across all activities.
• Initial femoral rollback and tibial internal rotation were noted during early flexion, with minimal condylar lift-off in most activities.

Conclusions:

• The Physica KR knee implant exhibits congruent kinematics and functional performance.
• In vivo data show initial femoral rollback, consistent with cruciate-retaining implant behavior.
• The Physica KR system demonstrates kinematics comparable to established TKR designs.