The Procedure – For Surgeons

I’m Marty Redish and am a general orthopedist in practice for 36 years in Chattanooga, Tennessee. I learned the Repicci technique when it was introduced in 1999 and started doing cases in March 2000 and have done around 4000 of them since. My interest in this has allowed me to be involved as a consultant with Biomet, MAKO, Zimmer-Biomet, and now Maxx orthopedics. I was part of an international development group to produce a new fixed bearing Uni based in Europe with Biomet. I was part of a four surgeon team that helped to develop the lateral uni for MAKO. I was working with engineers to develop improved instrumentation for the Repicci unicondylar when the company decided to discontinue manufacturing the implant. I am now working as a consultant with Maxx orthopedics, a company that has aided me in finally accomplishing my goal, which is to develop instrumentation and power tools to make this technique easy and reproducible. 

I am doing this work because of my firm belief that our profession is doing patients a disservice by doing total knees in great numbers on patients who do not need them. I receive no royalties from the sales of this product. We need to be doing UKA on patients with unicondylar disease and I think that this method can be a way to break down the barriers that keep most surgeons from doing them. 

I have proven that this implant works with 10 year followup at 94.6 % retention rate as published. We have developed a new system that makes the procedure quick, easy,accurate, and reproducible. There is no need for robotics or patient specific instrumentation, no need for distraction devices, or creation of stress risers from extra pin holes.This makes it ideal as a procedure that can be done in an ambulatory surgery center with very low overhead. 

I will in the next section explain the rationale for using this system. We will examine the history of it and the reasons it is seldom used or even known about presently. We will look at how the indications for UKA are expanded by using this implant. Included will be pertinent studies and a video of the technique. 

Why are so few UKAs done? 

There are many reasons for this, and here are some: 

1) Many of us get very little training in UKA, even those of us that are fellowship trained in arthroplasty 

2) The cumulative literature states that UKA has a higher revision rate than TKA

3) UKA can be more difficult to do than TKA, with no greater reimbursement.

4) We are afraid that an unsuccessful UKA will compromise a future TKA that could have done to begin with, that nobody would have faulted us for doing in the first place.  

It is reason 4 that I feel is most responsible for the paucity of UKAs that are done. The literature has shown that revision of UKAs results in a knee that is closer to resembling results of total knee revision than it is a primary total knee. Often long stems and/or augments are needed. That, of course, is because the UKA has removed some of the bone that we needed to support a primary TKA. The literature has also shown that UKAs performed by those doing them at a low volume have worse results than those by high volume users. So the new orthopedic surgeon is faced with a decision whether or not to do a procedure that they are not very familiar with that will compromise the chance of a primary TKA. Most choose not to take that chance.  

But what if we had a UKA that could be converted to a primary TKA if needed, and the recovery for the patient was not much more involved than arthroscopy? If we knew that we weren’t compromising any future TKA in case the patient did poorly? Then the fear of doing harm is taken out of the equation for the most part. 

It is no wonder that when Biomet first introduced the Repicci implant, the procedure I did and similar to what I do now, that it was difficult to even get into a one day seminar to learn it because of the demand from joint surgeons. It seemed obvious at the time that this was the” next big thing.” This procedure was where the term “minimally invasive” was invented, by my colleague at Maxx orthopedics Bob Eberle. This implant was made to be something that did not destroy any bone stock that would be needed for a possible conversion to a primary TKA, and it was the first to be done through a muscle sparing incision. 

Resurfacing vs Resection UKA 

At this point I would like to make the distinction between “resection” and “resurfacing” UKA. A resection UKA utilizes saw cuts through the femur and tibia. The femoral component has to be at least 6 mm thick and has chamfer cuts. The tibial component is usually modular with a metal tray and poly insert. Basically like half a total knee. A “resurfacing” UKA does not use saw cuts except for possibly removing a small portion of posterior femoral condyle. The femoral component is curved to match the contour of the femoral condyle and can have one peg and a keel. The keel controls rotation and strengthens the component so that it can be as thin as 2mm. The tibial component is an all polyethylene wafer that is inlayed and cemented into the tibial surface. A resurfacing UKA preserves portions of the natural joint line and removes minimal bone. A resection UKA removes more bone and cuts away the natural surface, so that the joint line must be re-established by varying thicknesses of metal and plastic. 

Brief history of the resurfacing UKA with all poly inlay 

The Marmor UKA from the early 1970s made use of an inlayed all poly tibial component and a thin resurfacing femoral component with one peg. It proved quite successful despite the smaller and thinner size of the tibial component and the less durable material then used for the plastic compared to today’s polyethylene. Because of some engineering errors by the manufacturer and ensuing medical-legal actions because of the femoral components being inaccurately sized, users of this prosthesis abandoned its use for fear of legal entanglements. 

Then in 1999 Biomet introduced the “repicci” resurfacing UKA, which was done through a small muscle sparing incision without patellar dislocation. There are several reasons that the initial widespread enthusiasm for this technique eventually waned to the point that Zimmer Biomet stopped manufacturing it a few years ago. First, it was taught in one day seminars that did not prepare the surgeon properly.This led to procedures being improperly done, which resulted in an unacceptable percentage of failures as reflected in various registries. Secondly, attempts to improve the technique were abandoned by the manufacturer in favor of promoting the Oxford UKA. As a result, Biomet stopped promoting the Repicci just a few years after it’s introduction. This left a minority of it’s users who had individually succeeded in teaching themselves how to effectively use the prosthesis still using it, and by attrition and retirement of these surgeons, the sales went down to a point where it was no longer profitable to make the prosthesis. 

It is critically important to note that the literature did not uniformly show this approach to be unsuccessful. Instead the results were variable depending on proficiency of surgical technique. I published a paper showing a 94.6 retention rate 10-13 years followup and Repicci and Kohane also had very favorable results. 

The MAKO company was originally formed by engineers who saw the problem of the Repicci technique and tried to solve it with the use of robotics and haptic guidance. They developed a resurfacing UKA looking almost identical to the Repicci but that could be more accurately implanted using a robotic arm. Unfortunately their tibial component did not originally have a textured inferior surface, so some sudden loosening occurred at the poly-cement interface of some of their cases. This, along with the purchase by Stryker, led to the abandonment of the all-poly inlay for which the robotics were originally designed to make more accurate to implant as opposed to the freehand Repicci technique. 

This new product we have created with Maxx Orthopedics, called “Renew” is very similar in design to the Repicci. The difference is that by creating a better workflow and new instrumentation, jigs and power tools, it is now easier, more accurate, and reproducible. Everything has been designed to be user friendly. A new rasp to flatten the bottom of the tibial pocket is a game-changer. A simple templating system ensures that the femoral component is centered on the tibial inlay. The use of a highspeed aggressive burr and a bit especially designed to decorticate the femoral surface are new, easy to use tools. The surgical setup places the surgeon in a comfortable position and there are no extra holes made by alignment pins and no distraction devices are needed. 

I hope that you will take the time to look at the technique video and other materials provided, and thanks for your interest.

Cleaning out marrow contents thoroughly with an improvised tip to the pulse lavage to the tibial surface and using medium viscosity cement has allowed for deeper and more thorough cement penetration in these inlayed tibial component. The engineers at Mako were interested in the x-rays of my patients with such deep cement penetration. This paper, presented at the Orthopedic Research Society meeting, is an elegant laboratory study of how this cementing technique helps prevent subsidence and loosening.

This is a recent paper that demonstrates that superior clinical results are obtained by
placement of the femoral component in the central third of the tibial component in UKA. The new system used for the Renew partial knee has a simple mechanism that places the femoral component reliably in the central third.