Introduction

Active robotics for total knee Arthroplasty (TKA) uses a CAD-CAM approach to plan the correct size and placement of implants and to surgically achieve planned limb alignment. The TSolution One Total Knee Application (THINK Surgical Inc., Fremont, CA) is an open-implant platform, CT-based active robotic surgical system. A multi-center, prospective, non-randomized clinical trial was performed to evaluate the safety and effectiveness of robotic-assisted TKA using the TSolution One Total Knee Application. This report details the findings from the IDE.

We introduce a new technique called the “Posterior Cruciate Referencing Technique” (PCRT), a specific combination of surgical technique, devices and instrumentation. Careful anatomic preservation of the posterior cruciate ligament (PCL) based upon a specific reference point off the tibia allows for use of sloped tibial components to achieve consistent functional behavior of the PCL. We discuss the preclinical design and development leading to availability of this device, and subsequent early clinical experience with this approach.

Posterior cruciate ligament (PCL) retention in total knee arthroplasty (CR-TKA) has been a feature of certain styles of TKA since the inception of predictable TKA in the early 1970s. It has been adapted and promoted as advantageous for a number of real and theoretical benefits. In reality, however, PCL retention has proven inconsistent when applied across a broad range of surgical environments. A number of adaptations in surgical technique, device modification and instrumentation have been developed to try to improve the predictability of the surgical intervention and subsequent postoperative performance. It is our belief that currently recommended surgical techniques can lead to inconsistencies in surgical judgment and consequently performance of CR devices because they inadvertently compromise the anatomy and hence functional performance of the PCL. A study by Shannon et al showed that, during CR-TKA, the PCL was either partially or completely removed as a result of the tibial cut in two out of three cases [1]. Unlike the long held and validated approach of ligament releases for fixed New Technique for Functional Posterior Cruciate Retention in TKA varus and valgus deformity that, along with alignment, allow successful long 45 term outcomes, ligament release of the PCL to balance the knee in flexion, whether by bone cuts or physical release, may compromise its overall function and explain kinematic differences in expected versus observed performance. Our hypothesis is that devices, surgical techniques and instruments designed around anatomical and functional preservation of the PCL would promote a reproducible surgical approach and consistent clinical performance of a CR-TKA. This manuscript provides the rationale for development of a new technique called the “Posterior Cruciate Referencing Technique” (PCRT), a combination of technique, instruments and devices specifically designed to preserve the PCL anatomy and take advantage of the functional performance of the PCL. We discuss the anatomical, radiographic, kinematic and mechanical testing approach that suggests that this is a safe and effective approach for primary CR-TKA.

Conclusion: This manuscript presents a body of work that elucidates specific issues of implant design and technical implantation that may have led to inadvertent compromise of function of the PCL during CR-TKA. We believe that such compromises may explain the inconsistent kinematic behavior of these devices in the hands of surgeons who use them, and may result in clinical outcomes that were unintended. We have provided the rationale for a new technique of implantation the Posterior-Cruciate Referencing Technique (PCRT) -which mates specific referencing approaches of the PCL and tibial resection, with implants, to address PCL functional New Technique for Functional Posterior Cruciate Retention in TKA behavior. We have provided laboratory, pre-clinical and early clinical evaluations that suggest that this will prove a safe and effective approach to CR-TKA.