Total knee replacement designs have differing stability under novel robotic testing method in vitro.

Area of Science:

• Orthopedic biomechanics
• Biomedical engineering
• Surgical robotics

Background:

• Total knee arthroplasty (TKA) aims to restore knee function, but implant design can influence post-operative stability and kinematics.
• Instability following TKA is a significant concern impacting patient outcomes.

Purpose of the Study:

• To quantify the impact of three distinct TKA designs on knee kinematics and stability using a novel robotic testing method.
• To compare the biomechanical performance of different TKA implant geometries against native knees and each other.

Main Methods:

• Eight fresh-frozen cadaveric knees were tested under compressive and anterior-posterior (AP) tibial forces using a robotic actuator.
• Testing was performed on native knees and after implantation of three TKA designs (gradually reducing radius, multi-radius, single-radius).
• Knee laxity and rollback were analyzed using statistical parametric mapping.

Main Results:

• The single-radius TKA design exhibited significantly greater AP laxity compared to the intact knee and other TKA designs.
• No significant differences in AP laxity were observed between the intact knee, gradually reducing radius, and multi-radius TKA designs.
• Rollback percentages were not significantly different across the intact knee and the three TKA designs.

Conclusions:

• Significant differences in AP laxity exist between native and TKA knees, and among different TKA implant designs.
• Knee implant geometry influences stability, with variations in sensitivity to cadaveric and implantation factors.
• Robotic testing provides objective data on TKA design effects, potentially guiding surgeons to improve patient outcomes.