Does a mobile-bearing, high-flexion design increase knee flexion after total knee replacement?

Area of Science:

• Orthopedic surgery
• Biomedical engineering
• Clinical biomechanics

Background:

• Total knee replacement (TKR) aims to restore function and reduce pain in patients with knee osteoarthritis.
• Improving knee flexion is a key goal in TKR design to enhance patient quality of life.
• Different TKR designs offer varying degrees of flexion and functional outcomes.

Purpose of the Study:

• To compare the clinical outcomes of two PFC Sigma total knee replacement designs.
• To evaluate the efficacy of a high-flexion rotating-platform posterior-stabilised (RP-F) design against a standard fixed-bearing posterior cruciate ligament-preserving (FB-S) design.
• To assess differences in knee flexion, weight-bearing range of motion, and pain levels at one year post-surgery.

Main Methods:

• Prospective, randomized, controlled, double-blind trial involving 77 patients with knee osteoarthritis.
• Patients were allocated to either the FB-S or RP-F TKR group.
• Outcomes including non-weight-bearing flexion, weight-bearing range of motion (level walking, ascending slope), and pain scores (Western Ontario and McMaster Universities Osteoarthritis Index) were assessed pre-operatively and at one year post-operatively.

Main Results:

• The RP-F group showed significantly greater mean post-operative non-weight-bearing flexion (113°) compared to the FB-S group (107°) (p=0.032).
• However, the FB-S group demonstrated significantly better weight-bearing range of motion during level walking (58° vs 54°, p=0.019) and ascending a slope (56° vs 52°, p=0.044).
• The RP-F group reported significantly higher post-operative pain scores (4.2 vs 2.5, p=0.043).

Conclusions:

• While the high-flexion RP-F TKR design achieved greater non-weight-bearing knee flexion, this did not translate to improved functional use in daily activities.
• Patients receiving the RP-F design experienced reduced weight-bearing range of motion and increased pain one year after surgery.
• The standard FB-S TKR design provided superior outcomes in terms of functional weight-bearing movement and pain relief at the one-year follow-up.