All-Polyethylene Tibias in TKA: PS vs CS Implants

Osteoarthritis, Knee

cost, total knee replacement, arthroplasty, posterior stabilized, cruciate retaining, all-polyethylene

This is a randomized control trial where patients will be randomized to receive one of two types of total knee arthroplasty (TKA) all-polyethylene (AP) tibial components: cruciate retaining (CR) or posterior stabilized (PS). We will use radiostereometric analysis to assess the stability of the implants at 6 weeks, 3 months, 6 months, 1 year and 2 year post-operatively. The main objective of this project will be to determine which AP tibial component offers the greatest stability. Additionally, we will seek to determine whether patient BMI significantly impacts the stability of AP tibial components.

With healthcare expenditures rising as our population ages, there have been significant efforts targeted towards streamlining costs associated with various medical treatments. One area of substantial spending in the orthopaedic surgery field is total joint replacements. The effort to reduce costs has sparked a renewed interest in the use of allpolyethylene (AP) tibial components in total knee arthroplasty (TKA). In recent years, there has been ample research demonstrating that AP tibial components have performed as good as, or better, than metal-backed (MB) tibial components. Some studies have estimated that cost savings could be as high as 50% with routine use of AP tibial components. While sufficient literature exists demonstrating the equivalence or superiority of AP versus MB designs, there is a paucity of work done comparing different types of AP tibial components. Tibial components in TKA can be of the posterior stabilizing (PS) or cruciate retaining (CR) variety. To date, we are unaware of any study that directly compares AP tibial PS components to AP tibial CR components. Radiostereometric analysis (RSA) has evolved as an exceptionally precise and reliable method for assessing the migration of components in total joint arthroplasty. Using RSA data, it is possible to accurately predict, within the first 24 months post-operatively, the survival of a total joint arthroplasty. Furthermore, the use of RSA outcomes in arthroplasty research allows for adequately powered studies with significantly smaller sample sizes than previously required. The main objective of this project will be to determine which AP tibial component offers the greatest stability. Additionally, we will seek to determine whether patient body mass index (BMI) significantly impacts the stability of AP tibial components. We will prospectively enroll patients who will be undergoing a total knee arthroplasty by one of the study investigators. Potentially eligible patients will have the project explained to them during their preadmission clinic visit prior to surgery and if interested a member of the research team will perform the informed consent process. Should a patient elect to participate in the study they will sign the informed consent form and complete demographics and baseline health related quality of life questionnaires including Oxford Knee, EQ-5D, and the VR-12, in addition to the Western Ontario McMaster Universities Osteoarthritis Index (WOMAC) which is already completed as per standard of care. The baseline demographic characteristics that will be collected include age, BMI, gender, and relevant medical comorbidities. Patients will be randomized to have either a PS or CR all-poly tibial component used during surgery. Randomization will be stratified by BMI to ensure equal distribution in both groups. During surgery the surgeon will insert 6-9 tantalum beads in the proximal tibial, 6 beads in the polyeythylene tray, and another bead into the tip of the polyethylene stem. These beads will be used to measure migration of the implants on RSA imaging (radiostereometric analysis). The RSA x-rays will be taken at baseline (2 weeks) and at the 6-week, 3 months, 6 months and 1 year and 2 year follow-up appointments. These images will be taken at Robarts Research Institute in the RSA analysis suite. At the 3month, 6 month, 1 year and 2 year visits we will also collect health related quality of life questionnaires including the WOMAC, Oxford Knee, EQ-5D and the VR-12. Patients and data collector will be blinded to treatment arm. The person who will analyze the RSA images will be able to see which treatment arm participants belong to (based on viewing xrays) however the hypothesis of the study will not be revealed to them prior to analysis. Intra-operative cost information will also be collected using institutional cost data in order to compare differences in OR costs between the two implant designs and across BMI categories.

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