Does mobile-bearing knee arthroplasty motion change with activity?

Area of Science:

• Orthopedic surgery
• Biomechanical engineering
• Medical device design

Background:

• Total knee arthroplasty (TKA) aims to restore knee function.
• Implant design, particularly mobile-bearing types, influences joint mechanics.
• Understanding in vivo kinematics is crucial for optimizing TKA outcomes.

Purpose of the Study:

• To compare the in vivo kinematics of rotating-platform and meniscal-bearing total knee arthroplasty designs.
• To evaluate the influence of different activities of daily living on knee kinematics in mobile-bearing TKA.

Main Methods:

• In vivo knee kinematics were analyzed using fluoroscopic imaging and 3D model registration.
• Ten patients with bilateral TKAs (one rotating-platform, one meniscal-bearing) were studied.
• Kinematics were assessed during non-weightbearing flexion-extension, squatting, and stair climbing.

Main Results:

• Meniscal-bearing knees exhibited greater anteroposterior translations compared to rotating-platform knees.
• Increased quadriceps demand led to more posterior femoral rollback in meniscal-bearing designs.
• Rotating-platform knee condylar translations remained relatively consistent across activities.

Conclusions:

• Activity dynamics significantly affect knee kinematics after total knee arthroplasty.
• Unconstrained meniscal-bearing prostheses are more sensitive to activity-induced kinematic changes than rotating-platform designs.
• Implant design plays a critical role in the stability and motion of total knee replacements during daily activities.