High-flexion rotating-platform knees: rationale, design, and patient selection.

Area of Science:

• Orthopedic Surgery
• Biomedical Engineering
• Materials Science

Background:

• High flexion in total knee arthroplasty (TKA) is defined as flexion beyond 125 degrees.
• Activities requiring high flexion, such as kneeling, involve complex rotational movements.
• Existing TKA designs may limit the range of motion (ROM) necessary for these activities.

Purpose of the Study:

• To evaluate the clinical outcomes of the P.F.C. Sigma RP-F maximum flexion knee system.
• To assess the modifications made to enhance bearing conformity and reduce polyethylene stresses.
• To determine the efficacy of the P.F.C. Sigma RP-F in achieving superior ROM.

Main Methods:

• Modification of the P.F.C. Sigma RP posterior-stabilized knee to create the P.F.C. Sigma RP-F.
• Addition of a third contact area at the post-cam mechanism to increase bearing conformity.
• Clinical evaluation of patient outcomes, including postoperative ROM, for the P.F.C. Sigma RP-F.

Main Results:

• Statistically significant increases in postoperative ROM were observed in patients receiving the P.F.C. Sigma RP-F.
• The modified design effectively reduced polyethylene stresses in the 125-155 degree flexion range.
• Fluoroscopic kinematics demonstrated superior femoral roll-back with the P.F.C. Sigma RP system.

Conclusions:

• The P.F.C. Sigma RP-F knee system demonstrates significant promise for achieving maximum flexion.
• Patient selection criteria include those with high-flexion lifestyles, younger, active individuals, and those with limited preoperative ROM.
• The system is expected to provide enhanced longevity and improved functional outcomes for TKA patients.