Comparative study of intraoperative knee flexion with three different TKR designs

Area of Science:

• Orthopedic Surgery
• Biomedical Engineering
• Prosthetics Design

Background:

• Achieving substantial postoperative flexion in total knee arthroplasty (TKA) is crucial for patients desiring to squat or kneel.
• Prosthesis design is a key factor influencing postoperative knee flexion.
• In vivo analysis of intraoperative flexion across different TKA prosthesis designs is valuable.

Purpose of the Study:

• To compare the intraoperative flexion of three different knee prosthesis designs during TKA.
• To evaluate whether posterior-stabilized (PS) designs offer superior flexion compared to ultracongruent (UC) designs.
• To assess if high-flexion PS models provide enhanced intraoperative flexion over standard PS models.

Main Methods:

• A controlled, single-operator study involving 72 osteoarthritic knees undergoing TKA.
• Comparison of three prosthesis models: SAL (UC), LPS (standard PS), and LPS Flex (high-flexion PS).
• Intraoperative flexion was measured using computer-assisted navigation before soft-tissue closure.

Main Results:

• The LPS-Flex achieved a mean intraoperative flexion of 134 degrees, compared to 124 degrees for the SAL (p=0.0004).
• The standard LPS model showed 130 degrees of flexion versus 124 degrees for the SAL (p=0.14).
• The SAL UC design reduced intraoperative flexion by 8 degrees compared to PS models (p<10(-4)).

Conclusions:

• Posterior-stabilized (PS) knee prostheses, including standard and high-flexion models, provide superior intraoperative flexion compared to the SAL ultracongruent design.
• No significant difference in intraoperative flexion was found between the high-flexion LPS-Flex and the standard LPS prosthesis.
• The SAL ultracongruent design appears to limit intraoperative flexion in TKA.