This week’s Orthopaedic Crossfire® debate was part of the 18th Annual Current Concepts in Joint Replacement® (CCJR®), Spring meeting, which took place in Las Vegas. This week’s topic is “Neutral Mechanical Alignment: Stickin’ with the One That Brung Ya.” For is Peter K. Sculco, M.D., Hospital for Special Surgery, New York, New York. Opposing is Denis Nam, M.D., Rush University Medical Center, Chicago, Illinois. Moderating is Thomas S. Thornhill, M.D., Brigham and Women’s Hospital, Boston, Massachusetts.
Dr. Sculco: Just to start off saying that I’m honored to be debating Denis Nam. We were co-residents to together at HSS and he was my chief resident. I think we’ve aged pretty well over the past few years. I consider Dr. Nam to be a research friend and colleague but today he is my CCJR foe and he is a formidable opponent because he has already won awards from Seth and already debated in previous debates and honed his research skills.
I am sure many of you look at me and think that I have met my match and that I am out brained and out brawned, but I would contend that I will win due to the fact that I am supporting mechanical alignment and he will fail due to the kinematic alignment weakness of his argument.
What are the keys to a successful total knee arthroplasty?
First, you need long term implant survival. Then we need improved function and overall quality of life.
Recently, there’s been growth in alignment paradigms and today we are going to focus on neutral mechanical alignment and kinematic alignment.
When we look at neutral mechanical alignment and we look at large, long term studies from various registries, we do have good 10-15-year data showing greater than 90-95% survivorship for a number of different total knee implants.
In terms of pain and function, there was a recent meta-analysis (Shan, JBJS-Am 2016) looking at a number of studies that showed that neutral mechanically aligned total knees have a large and sustained positive effect on improving pain and function in patients and are very effective in treating knee osteoarthritis.
So, you are probably, wondering why are we even having this debate today? What’s the problem with our current methods?
Of course, we have that 10-20% patient dissatisfaction and Denis has published previously that while 90% of patients are satisfied, only 66% of them thought their knees felt ‘normal.’ While we know that patient satisfaction is a multifactorial, very complicated problem that is not always related to the knee itself, it does raise a question whether neutral mechanical alignment could be contributing to this dissatisfaction.
For a patient who is potentially unhappy with his neutrally aligned total knee we have Dr. Howell. He believes that kinematic alignment is the answer to this patient’s problems. Why is it the answer? It corrects the knee to its pre-arthritic alignment, restores the native articular surface, the native joint line obliquity, the native joint laxity, and minimizes soft tissue releases.
But what is the penalty for doing this?
