Seven Surgeons Tackle a 61-Year-Old Stockbroker’s First Total Knee – Part I

At the last Orthopaedic Summit: Evolving Technologies (OSET), a panel of orthopedic surgeons tackled the case of a 61-year-old stockbroker undergoing her first total knee replacement—knows all the investments and technology. In this panel, moderated by Scott Sporer, M.D., seven different surgeons offered their take on the real answer. Let’s hear from the first four. Can you guess who won? Is it 1) 3D Computer Navigation, or 2) Sensor Balancing, or 3) Navigation Hand-Held Alignment, or 4) a CT Guided Robotic Total Knee?

“3D Computer Navigation Imaging Is the Answer to Get Perfection”

Dr. McAllister: A 61-year-old active female stockbroker who is intelligent and well-read has been investigating what kind of technology she wants for her knee replacement. I’ll give you five reasons why she will choose computer navigation.

First, computer navigation is really the only global, 3D, real-time technology that has been proven over decades to deliver the outcomes we desire.

Unlike some other technologies, with navigation the surgeon is allowed to use familiar instruments. The surgeon can use the technology and still choose implants based on the quality and value of the implants, rather than the technology that’s being used.

How can computer navigation help us with early functional results? When accompanied by the appropriate balancing equipment, not only do we have command of all the important features of a knee replacement—but we’ve enhanced our opportunity to accurately perform minimally invasive surgical techniques, avoid a rod at the femur, and deal with some of the issues in terms of transfusions.

Navigation also impacts the venue, allowing us to become much more capable and austere with our choices of instruments. I do the majority of my joint replacements now in an ASC [ambulatory surgeryl center], where we need to be careful about the number of instruments.

When you’re talking to a patient, what they want to know is: What do you do? What is your experience? Why should I come to you?

I’m going to convey information on my patient-reported outcomes and the impact these technologies have had on my patients. I will emphasize that if this patient qualifies to have her surgery done on an outpatient basis, then that would save her a portion of the cost. I’ll show her how many narcotic pills our patients use, what her rate of recovery will be, and how quickly she’ll be able to get back to her daily activities. So, I will be discussing recovery at two weeks, three weeks, four weeks and Forgotten Joint Scores at three months instead of at two years.

I said I’d give you five reasons why this patient will choose to have navigation for her knee replacement. These are not my reasons, but instead harken back to a 2007 consensus statement from AAOS [American Academy of Orthopaedic Surgeons): navigation is the accepted gold standard for mechanical access, component positioning, ligament balancing, and it’s the perfect adjunct for minimally invasive surgical techniques which are now accepted. In the end, it means she can now more easily have her knee replacement done in the ASC. All my other colleagues are just wrong.

“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.

“Precision Alignment Technology in Your Hand, Gets It Done: A Simple Technique, I Will Convince You – Do the Total Knee My Way”

Dr. Ast: Why do I navigate? I navigate because conventional guides don’t work. The accuracy of conventional instruments hovers around 70-80%. The accuracy of some form of navigation hovers between 95-100%. And not only is navigation superior when it comes to achieving alignment, but it is superior in achieving long-term function.

I like to navigate with something that stays inside my surgical field, lets me use the implant of my choice, and seems familiar. If I am operating in my surgery center and I have to switch from a uni to a total, then there is no need to change anything at all…I only have to click a different button. That’s the beauty of the KneeAlign system: You can do any technique you want. You can align it however you choose, and you hit your goals every single time.

The technique is simple, and the navigation seamlessly integrates into the workflow. I am able to do procedures faster with this than with conventional instrumentation. The learning curve with this technology is very short; it’s also highly reproducible and highly accurate. And it goes beyond simply making sagittal cuts.

I use a gap balancing tool to guide appropriate resections and, most importantly, to set my femoral rotation because in my opinion that’s actually what we surgeons do the worst. Simply put in the device to tension your ligaments, and the gauge will tell you the correct numbers. Not only can you use the device to guide your cuts, but you can use the device afterwards to verify them. Soon we will even have medial and lateral gap height measurements.

This system has been proven in multiple published studies to be within one or two degrees of neutral mechanical access 96% of the time—dramatically better than conventional guides and equal to or better than conventional line-of-sight navigation.

This precision alignment technology offers all the benefits of traditional navigation with none of the drawbacks: both limb alignment and gap balancing are easily accomplished. There is no out-of-pocket expense to buy a million-dollar machine. You can use this on a case-by-case basis, and it is ideal for any patient—especially for those in your surgery center. I ask you, “Why haven’t you used it yet?”

“CT-Guided, Robotic Arm-Assisted Total Knee Arthroplasty”

Dr. Hepinstall: Navigation results are accurate and precise for alignment. In fact, my results will convince you to do the total knee my way. Our study found a nine-year navigation revision rate that is only 1.5% lower than conventional total knee replacement.

The goal of smart trials was to try and shift to a different target and objectively assess soft tissue balance in total knee arthroplasty. But balance wasn’t achieved in all knees despite the use of smart trials. Why? Perhaps because the original femoral rotation wasn’t ever going to allow you to get the balance right because of the femoral rotation you selected initially. We need something that allows us to intervene earlier in the process before we have done all of the bone cuts.

In fact, this was the impetus for the move to the world of the imageless robots. We have bone mounted robots that position cutting jigs and hand-held smart tools that prep the bone to accept manual jigs. These robots allow 3D intraoperative planning based on the registration of the accessible bone.

I use a CT-based robotic arm assisted total knee arthroplasty. It starts with a 3D plan based on a CT scan for shape matching, which allows us to visualize things we’ve never seen at before.

There are two forms of CT-based robotic arm total knee arthroplasty. One is a super navigation device where the knee is pinned in place and you get it precisely where you want it based on a pre-op plan (but there is no intraoperative soft tissue balancing). This is not the type of CT-based robotic arm TKR [total knee replacement] I do.

I opt for the procedure that allows us to robotically balance the knee with haptic soft tissue protection, surgeon control and no increase in adverse events. Again, you start with a 3D-measured resection plan no different than above. The workflow proceeds as follows: you expose the knee, attach the arrays, register the bone, remove accessible osteophytes, and then stress the knee dynamically to assess ligament laxity before making any bone cuts.

I adjust the resection thicknesses to reset the gap in the normal compartment. I then hinge on the normal side, adjusting alignment and rotation to approach balance, but not fully achieve it. We want to respect safe alignment parameters. Note that the affected compartment often loosens after removal of bone and osteophytes.

We then make fine-tuned controlling cuts, based on our dynamic assessment of the gaps.

Now we proceed with the soft tissue exposure and attach the arrays and probe the bone. With a CT-based plan, if you don’t pass the registration, that tells you something. The CT-based plan tells you that you didn’t probe the bone perfectly, information that adds value and accuracy.

We then dynamically assess the ligaments in flexion with the spacer and then move the knee into extension. We also can place the knee in 20 or 30 degrees of flexion to decompress the osteophytes and the posterior capsule.

The published results are quite good, with evidence showing that haptics and surgeon control protect the ligaments. There’s been no increase in adverse events and the benefits include less pain, less analgesic use, lower hemoglobin drops, fewer physical therapy sessions, and shorter length of stay. We also found faster time to straight leg raise and better knee flexion at discharge with improved WOMAC [Western Ontario and McMaster Universities Arthritis Index] scores both at six months and a year.

I examined my own results with 120 knees. Despite a technique and an implant that were new to me, we achieved balance with less articular constraint and a shorter length of stay. We also had a smaller flexion contracture on average and fewer manipulations under anesthesia to achieve similar knee flexion and similar Knee Society Scores.

While you might think a robot is unnecessary, it is actually a very good way to establish targets and hit them reliably. The robot can streamline your inventory in the future and protect the soft tissue. Go ahead and try it my way.

To hear how three other surgeons handled this same issue, stay tuned for Part II.

Please visit https://orthosummit.com/ for more information on this year’s upcoming 10th Anniversary Orthopedic Summit 2020 event on December 8-12, 2020 at the Bellagio in Las Vegas, Nevada.