Dr. Lewallen: Let me begin and maybe confuse my opponent a little bit by agreeing with him. I think the future of our profession, over the decades ahead, will be individualized hip and knee reconstruction. We will evolve towards a prescription based on their individual anatomic variability.
But we’re not there, not even close. And it could be dangerous to get in front of the parade.
I don’t have any conflicts directly related to this except being old and resistant to change.
The historical gold standard was chosen because surgeons could do it in a reproducible fashion. The outcome results supported the procedure and you’ve seen the data…variations around a target of this sort do not impact outcome. Importantly, having some varus on your tibia didn’t seem to make it any better either.
In my practice, there’s a lot of other things that can go wrong with primary knees and that are wrong with the ones I revise. How do we avoid those things? If we look at causes of failure, actually malalignment isn’t that big of a player, though admittedly early on perhaps it had a bigger role.
But what are the common errors?
- Under resection of the distal femur.
- Deviation from the alignment target. Not everybody hits the target and all of us have a bad day in the OR when we miss the target.
- Femoral malrotation and epicondylar axis problems.
- Tibial malrotation.
- Flexion extension gap imbalance.
It’s unclear how changing the target and kinematic knee alignment is going to solve any of those issues.
This operation demands attention to detail and small changes from what you’re doing in the surgery can combine to make big differences and the errors are iterative.
Failure to achieve rotation and balance at one place may affect the component on the other side. We’re told to resect exactly the same amount of bone from the back of the condyles on someone who, remember, had their knee wear out at age 50. That’s a normal knee? I don’t think so. So, we’re going to take bone off of the hypoplastic lateral condyle and mal-rotate that femoral component?
A few years ago, the most common cause of problems with total knees from the podium at the Academy was patellofemoral problems. That’s largely been solved by attention to detail and implants, but also surgical technique to avoid malrotation. I don’t think we want to go back.
Malrotation of the tibia, which is facilitated by problems with the femoral side, is a very, very frequent cause of problems. How does kinematic alignment solve that problem?
At the beginning of our careers many of us observed that a lot of folks are walking around a little varus in the tibia, and a little more valgus on the femur and the joint is a little bit oblique. What would go wrong with sort of having that as a target?
I can tell you what went wrong. Surgeons weren’t able to hit the target of the 3 degrees very reliably. They couldn’t see it very well. We had a lot of variability. So, 3 degrees of varus is okay, but 5 or 6 degrees is not. And if you shoot for 3, you’re going to end up over there some of the time.
One of the things I will compliment the kinematic folks on…here’s the first time in my career that I’m giving this talk and there are four RCTs [randomized clinical trials] on the topic that have come out in the last couple of years. The problem? They’re all different. Some say it’s good. Some say it’s okay, but you have more outliers and poor outcome.
Kinematic alignment is an interesting concept. We will watch this with interest. But it increases the technical difficulty and complexity for the average surgeon. Meantime, follow the steps and put it in straight.
