“Sensor-Assisted Technology Improves Patient Outcomes & Satisfaction: I Am the Answer”
Dr. Roche: I’m going discuss about how I three-dimensionally integrate the rotation of the implant, the alignment of the implant, and functionally position it to achieve optimal balance.
We integrate sensors into the trials so that they are easy to use. These trials have load sensors, alignment information and rotation, and give you quantified data on the tension in the ligament.
Intraoperative real time data can give us information on coronal imbalance, sagittal imbalance, and malalignment. Flexion gap instability—a three-dimensional problem—seems to be the most significant issue.
For total knee procedures, several things are critical. We must understand the importance of the soft tissue, as well as the dynamic stress/strain curve of the ligaments. We also must develop a better grasp of which ligaments and which bone structures affect what position of the knee.
These trials allow for the assessment of the knee depending on how much force you apply to achieve a gap balance—whether you are using a cruciate retaining or a cruciate substituting knee. The trials allow you to differentiate the distance of the opening in flexion, especially in the posterolateral corner (which can affect a lot of rotational issues).
We typically see asymmetric issues in the OR, meaning that if you have a flexion contracture, it is usually not both femoral condyles—it’s usually either the medial or lateral wheel that is jammed. The sensor provides this information so that I can try to create a perfect total knee.
The trials with sensors can achieve an effective soft tissue balancing through bone adjustments, rather than an all or nothing effect. We can now go to bone to balance and change our alignment in three-dimensions based on the soft tissue tension. This stockbroker will be very excited with this technology.
Yes, there are robots and navigation. But these simple sensors allow for very accurate bone cuts—within one to two millimeters. And, more importantly, they have tremendous effects on soft tissue balancing. If I show you a case using navigation and a robot, coronally, in flexion, I am balanced. Although testing my gaps in flexion reveals they are fine, the sensor tells me that my PCL [posterior cruciate ligament] is excessively tight. The robot allows me to rotate the femur because the PCL is affecting the posteromedial corner. So, then I take another millimeter of bone. Now I put the sensor back in and I see the rollback laterally in the medial pivot has created a fine, stable knee. All I needed to do was a small, fine adjustment of the bone.
With regard to alignment, whether you want kinematic or constitutional affects your femoral rotation. This means that you must match your tibial rotation to your femur—otherwise you will have significant soft tissue tension. This is another area where the sensor equipment is useful as it aids with the adjustment process. Adjusting the bone and achieving continuous quantified data results in a good stable knee through a full range of motion. This is what patients want—maximum motion with good stability.
Sensors are also cost-effective and save approximately $725 for the patient. The savings are achieved by minimizing postoperative intervention in terms of physical therapy because those patients are balanced and have fewer issues.
Concerning revision, we looked at 100 patients and put the sensor in before any significant changes and we found many issues. In fact, our data showed that 88% of planned total revisions changed to a partial revision. Pretty amazing.
I think all this robot-assisted knee replacement is a bunch of crap. You just need an experienced surgeon who does high volume and he can figure out things when he’s in there.