Dear Prof. Norberto Confalonieri,

What percentage of your practice is Unicompartmental Knee Arthroplasty (UKA) and is this part of your practice changing over time?

I’ve been implanting UKR since 1988 and Small Implants since 1999, with CAS since 2001. Of course, my practice has changed over time. My patients have changed over time. My technique has changed over time. In the late 80s, I implanted six Uni. Today, 35% of my knee replacements are medial and lateral UKR, 25% small implants (PFA, Bi-UKR, UKR+PFA), and 40% total or revisions, all computer assisted (as well with PSI). I have had a small and positive experience with robots (Mako and Blue Belt).

Why do you think many surgeons still are hesitant about implanting UKA?

Crucial and delicate question. First of all I notice the use of Uni is growing enormously everywhere and this is also due to the efforts of this faculty in scientific communications. In the far 1998, with Sergio, we founded the Italian Uni User Group with only 27 members. Today, many surgeons, who were against, are enthusiastic supporters and someone is here, to talk about. In a recent meeting with Mayo Clinic, of Rochester, Mark Pagnano reported about the development of Uni in his Department. In the 2000s they implanted few units of UKR, but increasing, in 2014 more than 200 and most of them with Mako robot. That said, the problems of UKR are related to its bad reputation: doesn’t last long, it’s painful, it’s challenging, there are few indications….
Well, we are here to explain how most of our patients has a very good result at long term follow up. Indications, surgical technique, pearls and tricks, are the base of success.

When do you think patellofemoral disease should be treated in unicompartmental arthritis of the knee?

Asymptomatic? Never. Symptomatic, with bone to bone (Xray Iwano classification), ever!
Now, I’d change the question: what would you do a 59 y.o. patient with isolated and symptomatic patello-femoral arthritis? The most of American surgeons would implant a TKA. We consider this an overkill treatment. We implant an isolated PFA. With a symptomatic medial or lateral tibio-femoral compartment arthritis, in a varus or valgus knee, we use Uni and PFA in association. We restore first the medial or lateral compartment, we correct the arthritis deformity and, at the same stage, we implant PFA. In some case, young patients with post traumatic arthritis, with stable knee, we use a Bi-Uni, medial and lateral, and PFA. First, the most damaged compartment (medial in varus, lateral in valgus), then the others. The same for arthritis in neurological diseases. When you spare the central ligaments, you don’t have the somatognosic effect, the feeling of loss of a part of your body (knee). Said that, two words about this reasoning. The knee is not a whole joint but it’s composed of three different compartment that work in three different way. Our aim is to solve the problem of patient without change, if it’s possible, the natural joint biomechanics. The tissue sparing surgery is our philosophy that leads to the compartmental reconstruction of the knee, saving the central pivot, real fulcrum of knee cinematic.

Do you think wear of the other compartment or of the implant is a bigger issue than wear in total knee arthroplasty (TKA)?

No, the problem is the surgical technique. We’ve already published our rules: correction of arthritis deformity, minimal bone resection, the same joint space in extension and in flexion, control of mechanical axis in flexion. New ancillary instrumentations and CAS are very helpful, above all, if you implant less than 30 UKR a year.

Why are you so passionate about UKA because when we look at register data we shouldn’t be?

I started to implant UKR long time ago, because my old Chief used them sometimes. On the afternoon, in the surgery of Department, I revised all the knee prosthesis. The outcomes of Uni were astonishing in comparison of TKR. Flexion, functional recovery, complications, stability, ecc., all the parameters were better. So, slowly, I started to use them in a favorable environment, although the scientific world was contrary. My first reports were positive. I used a very half TKA, with intramedullary tools (M.G.). In the market there were many Uni resurfacing that needed a lot of manual skill. Otto Roberson, the author of the first Swedish Register, focused perfectly the problem showing clearly how the UKR was an operation surgeon demanding and challenging.
He found the magic number: 23. Over this number of implants a year the outcomes improved dramatically. I’ve always paid attention to the surgical technique and recently I studied a software to overcame the most important hurdles of this implant. The Uni has always been penalize in the Registers. Even in the excellent work of D. Murray, publish in the Lancet 2014, the UKRs are burdened by a high rate of revisions. Yes, revisions not failures. Because to revise Uni is easier and profitable. You replace it with a primary TKA and collect the revision reimbursement. We have an average of 8% of unexplained implants painful due, in my personal opinion, to the different modulus of elasticity of two compartments. But if you wait, until 12 months, the percentage drops to near zero. Of course, with the support of therapies like Tecar, pulsing electromagnetic fields, diphosphonates, analgesics, ecc. So, too many early revisions is one of the pitfalls in the Registers. Another important point is: how have been implanted? Yes, because you can do that by free hand, by traditional cutting guides, navigation, PSI and robots. Believe me, between free hand and robot there is a huge difference in terms of accuracy. Which prosthesis are revised? Registers don’t tell us. But they say that is a fantastic operation in terms of lower mortality and complications compared to TKA, faster functional recovery, better functional scores, etc., etc, etc. In one word: natural knee.

Which type of technology could be a game changer in the development of UKA to the broader surgical public?

Navigation! Cheaper and simple. Robots will be the future, perfect software but now too expensive and cumbersome. PSI less precise than navigation, in my experience.

What do you believe our readership should learn from you about UKA?

Mininvasive surgery is not minincision. Respect noble tissue under the skin. Respect the normal cinematic of the knee. Indications, surgical technique, prudence. The knee reconstruction must be customized (a la carte). There are many implants option. There are many technological tools for your assistance. In other words, read the book “Small Implants in knee reconstruction”, edited by Springer. Have a good meeting!

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