Let’s look at the science.
In a recently published study by my senior partner (Biyani, et al., Surg Technol Int 2017) who did PCL [posterior cruciate ligament] resection in two different knees. He took away the cruciate ligament and replaced it with either an anterior lipped or a PS tibial insert. No functional differences reported at one year.
Brian Parsley and co-authors reported the same thing years ago using an ultra-congruent bearing versus posterior stabilized (J Arthroplasty 2006).
David Scott, et al. presented at AAHKS [American Association of Hip and Knee Surgeons] and subsequently published in the Journal of Arthroplasty, a prospective, randomized study of approximately 50 knees in each group, anterior lipped total knee versus PS total knee. The PCL was resected in all cases. There was no difference in functional outcomes at two years.
An elegant Mayo Clinic study of 8,000 total knees (Abdel, et al., JBJS-Am 2011). Fifteen years survivorship; 90% for cruciate retaining; 77% for posterior stabilized; and the risk of revision was lower in the cruciate retaining knees.
Finally, as we continue to evolve total knee designs, we bring technology into the picture. One of the big advances will be highly cross-linked polyethylene. It minimizes wear. But its Achilles heel is the fatigue properties. So, you cannot use a post in those designs. Long-term—you’ll see issues.
The emergence of anterior lipped cruciate retaining inserts obviates the need for a posterior stabilized total knee replacement with a cam and a post.
Surgical technique remains critical because the knee must be balanced in flexion whether you use a cruciate retaining or posterior stabilized design.
There is currently no scientific evidence to support a cam and post mechanism to replace a posterior cruciate ligament in total knee arthroplasty.
Dr. Padgett: Vestigial, according to Webster, is “an organ or part of the body that becomes functionless, such as your recta pila muscles, male nipples, tonsils.” Is the post-cam vestigial? This is the debate. I respect Michael and we are friends. But Michael on this—you are wrong.
Meneghini says, “cruciate retaining works.” Padgett says, “posterior stabilized post not only works, it predictably works.”
Mike let’s agree on this. The best knee is the natural knee. It’s the number one knee. It’s the bomb, right? No question about that. And the best gait data, is the bi-cruciate retaining gait. This goes back to Cloutier in the 80s. The problems with the bi-cruciate knees—they are technically difficult and while the gait data supports its more normalcy, clinical results demonstrate no advantage.
Modern day total knee. What’s the first step? We reset the ACL. And what happens with that? The kinematic data shows an increase in the degree of anterior translation in the ACL-deficient knee. Which, by the way, is what the cruciate retaining knee is, right?
But we want to drive contact posterior. How do we do this? Articular geometry, reliance on the PCL, or perhaps a post/cam mechanism.
