Postoperative flexion analysis of 3 rotating-platform knee designs

Area of Science:

• Orthopedic Surgery
• Biomedical Engineering
• Reconstructive Surgery

Background:

• Rotating-platform knee implants are designed to enhance postoperative knee flexion.
• Modifications have been made to improve implant performance, evolving from cruciate-sacrificing to cruciate-substituting designs.

Purpose of the Study:

• To evaluate if modifications in rotating-platform knee implants led to improved postoperative knee flexion.
• To compare the clinical outcomes of the Low Contact Stress (LCS) implant with its successors, the PFC Sigma RP (ΣRP) and PFC Sigma RPF (ΣRPF).

Main Methods:

• Comparative analysis of postoperative flexion at 2 years against preoperative flexion across three implant designs: LCS, ΣRP, and ΣRPF.
• Statistical analysis was performed on patient demographics and flexion changes, with subgroup analysis based on preoperative flexion levels.

Main Results:

• Both cruciate-substituting implants (ΣRP and ΣRPF) demonstrated statistically significant improvements in postoperative flexion compared to the cruciate-sacrificing LCS implant (P<.001).
• No statistically significant difference in postoperative flexion was found between the ΣRP and ΣRPF implants (P=.045).
• In patients with preoperative flexion <125°, ΣRP and ΣRPF achieved significantly better postoperative flexion than LCS (P<.001), but not significantly different from each other (P=.621).

Conclusions:

• Cruciate-substituting rotating-platform knee implants offer superior postoperative flexion compared to cruciate-sacrificing designs.
• The modifications leading to the ΣRP and ΣRPF implants represent a successful advancement in improving knee flexion after total knee arthroplasty.