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The Knee Care Press


Implant-guided motion may help patients “forget” their TKR

At one year, patients receiving a Medial Congruent (MC) bearing reported significantly higher Forgotten Joints Scores (FJS) than those receiving a Cruciate Retaining (CR) bearing (71.6 Vs 58.7; p = 0.02) 1.

More patients in the MC group were “very satisfied” (92.6% Vs 81.5%; p = 0.04) and fewer were “not at all satisfied” (1.2% Vs 9.2%; p = 0.04) compared with the CR group1. Although the MC group reported better pain scores than the posterior stabilised (PS) group at every time point (p < 0.05), and showed a trend towards higher FJS at one year (71.6 Vs 68.71; p = 0.7381), the difference did not reach statistical significance1. The satisfaction ratings for MC and PS knees were also similar1.

This was a study of 327 consecutive TKRs implanted between January 2017 and March 20181. The TKR system used has an anatomic tibial component that accepts 5 different levels of constraint. The same CR femur accepts CR, Ultra-Congruent (UC) or MC bearings, while the PS femur accepts PS and constrained PS (CPS) bearings1. This evaluation was limited to CR (n = 70), MC (n = 96) and PS (n = 161) bearings1. UC bearings were excluded because of their limited use within the institute, and CPS bearings were excluded because their use may reflect some ligament instability. 1 All data were obtained prospectively and then retrospectively reviewed. 1 All surgeons followed a similar measured resection surgical technique, and all patients followed a similar pre- peri- and post-op care pathway1.

The authors noted that “a common goal of joint replacement surgery is for patients to be unaware of their artificial joint with daily activities. This concept of the ‘forgotten joint’ may be a way to measure the ‘success’ of joint replacement surgery1.” The validity and reliability of the FJS have been well documented1. It has demonstrated lower ceiling effects than other PROMs, which make it a good tool to measure small differences in performance between groups of high-functioning patients1.

In total hip replacement (THR), which is generally considered to provide higher levels of patient satisfaction than TKR, 1 year FJS of 73.96 were considered to be a successful outcome1. In the current study, the FJS for the MC bearing was 71.621. This is quite close to that of a successful THR, and falls between the mean (66.8) and median (75.0) scores for normative FJS-12 data for the knee, suggesting similar joint awareness to that of a healthy knee joint1.

The authors concluded that: “This type of knee design may help surgeons achieve higher levels of patient satisfaction and close the gap on the elusive 20% dissatisfaction that has previously been reported1.”

  1. Frye, B. M., et al. A Medial Congruent Polyethylene Offers Satisfactory Early Outcomes and Patient Satisfaction in Total Knee Arthroplasty. Arthroplasty Today. 2020; 7: 243-249. DOI:

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