Computer assisted total knee arthroplasty: kinematic versus mechanical alignment

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The aim of this project is to compare two different total knee arthroplasty (TKA) approaches with regards to alignment. Traditionally TKA aimed to achieve a neutral or straight (mechanical) alignment of the knee with a perpendicular joint line. However studies have shown that rarely does this arrangement echo normal anatomy. In most individuals the mechanical axis of the limb is not neutral and the joint line is often slightly oblique. Given that up to 20-25% of patients are dissatisfied with their TKA outcomes due to pain and poor function with activities of daily living, there is much room for improvement. Kinematic alignment aims to restore the knee to its normal pre-diseased alignment, in doing so match the prosthesis more closely to the ligamentous envelope which it must function and therfore may improve post-operative kinematics and function. The gold standard for accuracy in TKA is computer assisted surgery and although mechanical versus kinematic alignment has been studied in a single randomised control trial, the surgery was performed without computer assistance. This study will compare outcomes of navigated kinematically aligned TKA versus navigated mechanically aligned TKA which uses computer assistance to ensure accurate positioning of the prosthesis. 250 patients will be chosen for the study. These patients will be selected by three surgeons involved with ORIQL as needing total knee arthroplasty and as indicated by clinical guidlines. There will be two study groups. Group A (200 patients) will be patients undergoing unilateral total knee replacement and group B will be those undergoing bilateral TKR. The participants in group A will be randomized to either mechanical or kinematic alignment. Group B (50 patients) will have one knee replaced kinematically and the other mechanically. Randomisation will apply to which knee is done first. The first replacement will be done kinematically and the second mechanically provided that any alignment difference between the two does not produced visual asymmetry. In this instance, the second knee will be done kinematically and the patient withdrawn from the trial. All patients will undergo the same protocol process for total knee arthroplasty. All other intra-operative and post-operative protocols will be the same for all patients. They will be followed up post-operatively at 2 weeks, 6 weeks, 6 months, and then yearly. Post-operative radiologic assessment will be that normally required following TKA. Outcome measures will include validated clinical pain and function scores such as the WOMAC score, EQ5D, Knee Society Score, the Oxford Knee Score, and the Forgotten Joint Score. Data collected will be analysed using statistical methods in order to find any statistically significant difference in results between the two alignment strategies

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