This week’s Orthopaedic Crossfire® debate was part of the 33rd Annual Current Concepts in Joint Replacement® (CCJR®), Winter meeting, which took place in Orlando. This week’s topic is “The Medial Stabilized Knee: The “Post-Cam” Replacement.” For is Fares S. Haddad, M.D., F.R.C.S., University College Hospital, London, United Kingdom. Opposing is Chitranjan S. Ranawat, M.D., Hospital for Special Surgery, New York, New York. Moderating is Thomas S. Thornhill, M.D., Harvard Medical School, Boston, Massachusetts.
Mr. Haddad: It’s a huge privilege to debate Chit. Chit was designing knee replacements when I was learning how to walk and has done a phenomenal job over the last few decades. But the reality is that the world has moved on.
We’ve shown knee replacement to be an effective strategy, but there are some poor satisfaction rates out there and our patients’ expectations and our own expectations are increasing. We really should be at the stage where technology allows us to recreate the stability and the kinematic profile of the native knee.
And we haven’t really moved very far. We’ve been arguing at this meeting about the same things ever since I started: alignment, fixation, patella resurfacing and so forth. We should be interested in the medial pivot discussion.
Let’s begin with the anatomy of the knee. We know that the medial side is ball and socket; and the lateral side moves around the medial side. That’s been well documented. So we know that there is a concept that sagittal stability medially may be the key to optimal function.
Knee replacement technology developed along the route it did because of a number of surgical limitations. The Freeman medial pivot route was superseded by other techniques, but maybe the time has come to revisit that. Because there is good data suggesting that if you use a medial pivot knee, survivorship can be excellent.
And the really interesting thing is now there are a number of designs out there that use this concept, so perhaps the time has come to think about it a little bit harder.
If you look at medial stabilized knee designs under fluoroscopy, they do exactly what you expect them to do. If you look at the knees, they are made to do difficult tasks that our patients struggle with like stepping up and kneeling and what you find is you get the same graphs as when you’re studying the native knee.
Perhaps we’re achieving what we set out to achieve.
What about the data? In a prospective randomized study we are trying to drill down and compare a knee not too unfamiliar to our moderator (PFC Sigma PS, n = 40 knees) with a medial pivot knee (MRK, n = 40 knees) and randomizing patients trying to see if we can see a difference.
These are patients that had a standardized surgery, standardized follow-up, all by the same team in the same way. They’re pretty similar, both clinically and radiographically pre-operatively and didn’t really have very big differences in their post-operative journey. They had the typical sort of complications that patients get after knee surgery (2 DVT, 1 hematoma, no revisions, no infections, 3 unrelated deaths, 4 lost to follow-up).
But when we look at their range of motion, we saw much bigger, statistically significant (p = 0.0035) range of motion in the medial pivot knees and this was maintained after 5 years.
