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Thursday, July 7, 2022



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An Interview with Dr. Robert Steensen Orthopedic Surgeon on Kinematic Alignment

Why he prefers kinematic alignment

How did you discover kinematic alignment?

I’m an orthopedic surgeon in Columbus, Ohio with over 30 years of practice experience. Like many, I was taught mechanical alignment. That’s what we’ve done for years, and we’ve had good results. But I had an interest in improving my results.

In following the orthopedic literature, I noticed that kinematic alignment began popping up more and more. At first, it went against what traditionally has been taught. It’s a different philosophy, and it takes a little time to wrap your head around it – but the more I considered it, the more sensible it seemed. I thought this could be a better option.

Can you expand further on what kinematic alignment entails?

Kinematic alignment is a technique to place a knee implant where the native knee was prior to the development of arthritis. By its nature, it is individualized to each patient. By restoring the joint surface, the ligaments are under their natural tension and the leg is re-aligned to the normal alignment for that patient. Traditionally in orthopedics, knee replacement has used a “one size fits all” approach – mechanical alignment – that is standard for every single patient. It is a good procedure, but we can get better results and help the patient recover fully and faster if we place the knee exactly where the original knee was.

Compare mechanical alignment to kinematic alignment.

Mechanical alignment has the goal of making each leg straight from hip to knee to ankle and placing the joint line perpendicular to that line. That is not the natural alignment or joint line for almost any patient. Kinematic alignment tries to match the natural joint line and therefore restore the alignment to the normal for that patient. The alignment and joint line will be personalized for each patient.

With kinematic alignment, I see patients getting back to full function, faster. It feels more natural to the patient because it restores the joint line and works with their ligaments. Because I don’t have to release ligaments, they have less surgery, and patients recover faster. Surgeons who use mechanical alignment often have to release ligaments because the new joint surface does not match the ligaments, and it won’t feel as natural to the patient. If you look at the patient satisfaction levels of mechanical alignment, about 80 percent of people are satisfied with their knee, leaving a good portion of patients that are not completely satisfied. I believe it’s important to match the patient’s native kinematics better – after all, these are knee replacements, not knee approximations.

Why do you prefer kinematic alignment?

In kinematic alignment, you’re trying to duplicate the kinematics of the individual knee. In my view, it is focused on restoring the femoral joint surface to its pre-arthritic position. This restores the flexion-extension axis of the joint. It feels more natural to the patient, because it puts the joint line where it was and it works with the patient’s ligaments. While the traditional mechanical alignment was a good procedure for many years, with the increase in knowledge and innovations in technology, techniques of the past are not good enough for the patient today.

When I was using mechanical alignment, I achieved good results, but they were good results like everyone else gets good results. My patients were in the bell-shaped curve. My goal was to move the bell curve in a positive direction. With mechanical alignment, I felt some knees were very good and some were just good, but not a home run. I compare it with hitting a baseball. If you can hit the sweet spot, you really feel that was a successful surgery. Kinematic alignment allows you to hit the sweet spot much more predictably. It’s a balanced knee with the joint line in its normal position and the ligaments under normal tension. I believe it’s a better technique and a better knee implant, and patients feel more at ease knowing that their knee implant is being personalized to their specific needs.

What are the limitations of kinematic alignment?

Since mechanical alignment has one angle as a goal, ligament releases are often needed to balance the knee. In kinematic alignment, the resections are fine-tuned to match the patient’s anatomy. Ligament releases are not necessary except for in extreme cases. If you don’t have intact ligaments, neither kinematic alignment or mechanical alignment is appropriate, and surgeons need a more constrained implant.

How can the method be improved?

The world is moving towards technology, but technologies have yet to prove any value to the patient. I believe this is because technologies have been focused on a mechanical alignment goal. Kinematic alignment studies, on the other hand, show patients are getting better results when compared to mechanical alignment because of the technique. With that said, MicroPort Orthopedics is putting an emphasis on how they can integrate technology into their products and techniques for a positive impact on patient outcomes, specifically when it comes to the kinematic alignment technique.

Why do you choose to combine kinematic alignment with the Medial-Pivot knee system?

I believe pairing kinematic alignment with the MicroPort Orthopedic Medial-Pivot knee design offers additional improvement. If you align the joint line with the native knee using kinematic alignment, and you align to the native rotational axis with the Medial-Pivot design, that knee is going to feel as natural as a knee can feel for a total knee replacement. It matches both the flexion-extension axis and the rotational axis of the patient’s pre-arthritic knee.

The MicroPort Orthopedics Medial-Pivot knee system also provides great stability. It is very congruent medially, and unconstrained laterally, allowing the rotation that you normally have in a knee. The medial pivot design is actually, in both my opinion and KT 1000 testing, the most stable of the primary total knees. With the stability of the ball-in-socket design, you don’t need to resect a box or have a big post, and do not need an insert that is constrained both medially and laterally – the ball-in-socket design creates the stability.

How does your interpretation compare to other techniques in the market?

As time has progressed, we’ve made minor changes. This hasn’t been a system quickly thrown together. This is a system that’s had time to mature. These are our best efforts, and our best results. Surgeons who utilize these techniques can, in my opinion, improve their results for their patients.

I believe that kinematic alignment and the Medial-Pivot knee system share the same philosophy and work well together. I began working with MicroPort Orthopedics a few years ago because, at the time, there was not a set of manual instruments for performing kinematic alignment. I now perform my best knees because I’m combining the kinematic alignment technique, which aligns the flexion-extension axis of the knee, and the Medial-Pivot knee system, which aligns the rotational axis of the knee, recreating the normal kinematics of the knee. I have patients coming in, who in my judgment, are doing better, faster, because it’s more natural to put the knee implant where the original joint line was before they had arthritis.

Medical Device News Magazine
Medical Device News Magazine is a division of PTM Healthcare Marketing, Inc. Pauline T. Mayer is the managing editor.