Evaluation of the Functional Impact at 12 Months Post-op of Posterior Cruciate Ligament Conservation During Robotic-assisted Surgery (MAKO) for Total Knee Replacement. A Randomized, Single-blind, Multicenter, Controlled Superiority Study.

Knee arthroplasty is a growing surgical discipline and 102,655 prostheses were fitted in France in 2019. The principle of total knee arthroplasty (TKA) is to replace a thickness of bone and cartilage whilst maintaining homogeneous tension of the capsulo-ligamentary envelope. Different designs have been developed over the years to achieve a good compromise between stability and mobility, ligament balancing being one of the major challenges of this procedure. The results of this surgery are good, but remain inferior to those of the total hip prosthesis. Around 1/5 patients operated on are dissatisfied.

The posterior cruciate ligament (PCL) plays a role in the stability of the prosthetic knee, preventing anteroposterior translation and allowing femoral roll-back. It also plays a role in flexion space. However, whether or not the PCL is retained during total prosthetic knee insertion has not been shown to make any difference to clinical or functional outcomes.

The proprioceptive role of mechanoreceptors in the anterior cruciate ligament (ACL) has already been demonstrated in several studies. We can therefore imagine a similar effect when the PCL is conserved in TKA. Three prospective randomized studies have attempted to demonstrate this. However, those three studies did not find any significant differences in clinical or functional results. It should be noted, however, that all those studies were carried out without the use of robotics or any other means of assessing PCL preservation.

Robotics have made it possible to obtain better results, as well as greater accuracy and reproducibility of the surgical procedure and better intraoperative laxity control based on the concept of functional alignment.

Mechanical alignment was the first to be used during insertion of the prosthetic knee. It facilitates alignment according to the tibial and femoral mechanical axis, and better implant survival thanks to improved stress distribution. However, the patient's anatomy is not respected, leading to a certain amount of patient dissatisfaction. The concept of kinematic (or anatomic) alignment was designed to achieve greater respect for patient anatomy and ligament balancing. More recently, with the advent of navigation and robotics, the authors have described functional alignment, which optimizes TKA alignment according to residual ligament tension.

Since robotic assistance provides better control of the procedure and, in particular, better preservation of PCL integrity in this surgical variant, we believe it is time to conduct a high-level evidence study comparing these two surgical techniques: preservation versus removal of the posterior cruciate ligament in knee arthroplasty. We hypothesize that preserving the PCL will lead to better functional results, a better quality of life and an earlier return to activity.