A Prospective Randomised, Controlled Clinical Trial to Compare the Functional Outcomes of Patients Undergoing Total Knee Replacement Using the Zimmer-Biomet Persona Total Knee System With Cruciate-Retaining or Medial Congruent Bearings

There has been an increased demand in knee joint arthroplasties, in part due to rising life expectancies and a growing aging population, as well as increased wear and tear in the knees owing to lifestyle factors. As the demand continues to increase annually, improving long term patients' satisfaction and implant survivorship has become of utmost importance, as patients seek not only to alleviate their condition, but also return to their usual, daily activities and sports. Implant design and geometry plays an important role in this, with many modern designs seeking to replicate the native knee's kinematics and alignment through subtle changes in femoral components, tibial components, and polyethylene bearing inserts. The Zimmer-Biomet Persona® Total Knee system tries to replicate the 'feeling' of a native knee through an implant whose design not only stabilises the knee through medial conformity and anterior constraint, but also allows for freer and more natural deep flexion through freer movement of the lateral condyle. The Cruciate-Retaining Femoral Components (CR Femur) of this system, used in conjunction with the kinematic alignment surgical technique, has been shown to produce better functional outcomes and improved patient satisfaction; however, there is a lack of such studies in an Asian population to corroborate these findings.

More recently, Zimmer-Biomet introduced the Medial Congruent Bearing (MC Bearing) design to be used with the CR Femur; the design facilitates greater stability through increased anterior lip height compared to the original Cruciate Retaining Bearing (CR Bearing), thus allowing for greater anterior constraint and subluxation resistance that aids in activities requiring deeper flexion or full extension. Furthermore, the MC Bearing has been suggested for use in patients presenting with more complicated surgical histories (e.g prior high tibial osteotomies or patellectomies), whereas the original CR Bearing is strictly suggested for use only in patients undergoing knee surgery for the first time, where the posterior cruciate ligament may still be intact. This suggests that the MC Bearing may confer better cost-effectiveness, as it may be used in a wider population; combined with its subtle design changes relative to the original bearing design that further enhances the patient's mobility, the MC Bearing may be overall a better insert to recommend to surgeons and patients alike, in the hopes that it would provide the patient a greater degree of mobility, and better satisfaction.

120 patients who are seeking primary TKA surgery in Singapore General Hospital will be recruited to join this study. They will be randomized into two treatment groups in a 1:1 ratio: one group will receive the medial congruent (MC Bearing) polyethylene insert during their surgery, whereas the other group will receive the standard, cruciate-retaining (CR Bearing) design. Randomisation will be carried out by a designated study team member who will not be involved with data collection or data analysis. This team member will also keep the treatment codes in sealed envelopes until the end of the study, where the results can be unblinded, or in extraordinary situations where unblinding of patient is required.

Recruitment is anticipated to take place over twelve months following ethics board approval, beginning in Q1 2021 and completing in Q1 2022. The study is anticipated to complete in two years, with analysis expected to be completed by Q3 2024 following the last participant's last visit at 24 months post-surgery.

All patients in this study will receive routine clinical care pre- and post-operatively from their surgeon for two years; follow-up visits post-surgery will be planned for 1 month, 3 months, 6 months, 12 months and 24 months after surgery. Routine clinical care for patients undergoing TKA surgery include pre-operative and post-operative functional and strength tests at the Orthopaedic Diagnostic Centre, radiological assessments carried out by the Department of Diagnostic Radiology, and consultation visits with the surgeon. Pre-operatively, the patient will also attend a consultation with an anaesthesiologist to confirm their physical fitness for surgery.