Unicompartmental Knee Arthroplasty, Dr. Brian T. Palumbo

Thank you everyone. Again Dr. Palumbo with the adult reconstruction team at Florida Orthopaedic Institute. All right. So again my topic is a partial knee arthroplasty. Trying to gear this towards a primary care physician. The topic near and dear to my heart. These are my relevant disclosures so the objectives of the talk are discuss knee arthritis clinically and radiographically. I define what unique apartmental knee arthroplasty is and its role in reconstruction. Let’s talk a little bit about indications and patient selection which are really the bulk of this talk. I think with partial knee arthroplasty probably the most important aspect of achieving good outcomes is really patient selection. And then talk a little bit about outcome and survivorship. So of course, as you probably know knee arthritis or osteoarthritis is that wear and tear type of arthritis of the knee joint.
It really is a rather complex biochemical and mechanical process in which you get degradation of highland cartilage throughout the knee. I will talk mostly about a various knee. So I’m just for simplicity but in the various knee typically this will begin into your immediately it progresses post yearly with time and as the weather progresses until you get involvement of the Intercondylar notch in development of notch osteophytes along with a pro inflammatory state. You get a milieu for a chemical and mechanical ACL degradation. Once you get ACL or the ACL becomes insufficient you get progression of arthritis to the control lateral compartment and in subsequent tricompartmented arthritis and we’re trying to capture those knees with that with regards with regards to patient selection before they progressed to try compartment of arthritis. So here on the left you’ll see I have a normal knee healthy joint space about typically about six millimeters of joint space and the medial and lateral compartments and on the right you have a nasty arthritic knee would try compartment of arthritis you have bone on bone where pattern immediately and subtle subluxation of the femur on the tibia with progression of lateral compartment disease.
And these are this is really that what we’re trying to capture is before they progressed to to tricompartmental arthritis with arthritis with degradation of the ACLU have isolated medial compartment disease in this case and preserved lateral compartment cases where you have severe femoral tibial bone loss with severe deformities. These are obviously not cases where you can consider a partial knee totally arthroplasty is gonna be continues to be the gold standard for knee arthritis even in the case of isolated medial or lateral tibial femoral disease. I think the challenge with total arthroplasty what we’ve learned over the last decade or so is that our patients are achieving higher degrees of performance and so are the elderly elder years and their demand is really increasing. And this was really outlined by Phil Noble but outcomes and satisfaction rates with total arthroplasty are somewhat limited at least it had been over the past few decades.
And he wrote this paper in 2006 evaluated over 250 total knees and found that about 15 percent of patients were dissatisfied and I think that has a lot to do with surgical technique and experiences as a heterogenous patient data set. But it’s important understand why total knees were somewhat limited and that’s why you’re seeing this this rise in things like robotics and custom implants and in navigation to try to accommodate for that. partial knee arthroplasty is really another option to probably maintain a more natural feel or appropriate sections of the knee and have a better outcome. Overall, it’s really defined as the isolated medial or lateral tibial femoral resurfacing or also be considered a patellofemoral resurfacing but we’re not going to discuss that today. Certain benefits are improved function over total arthroplasty decreased rehab time and recovery time versus total knees. cruciate preservation will maintain a more natural kneecap somatic pattern and proper perception for the patient.
And of course, this is a bone preserving procedure relative to a total knee. Here’s an illustration on the on the right. You’ll see that this a partial knee to medial compartment arthroplasty. The patella femoral and lateral compartments are preserved and on the left. You’ll note the totally which of all three compartments are resurfaced and also it’s very important to note that the ACL is preserved with partial knee which is really a paramount in this type of surgery. So if it’s so good then why shouldn’t everyone get it to a partial knee. Because there really are some limitations in the. And again, we’re going to get into that with regards to indications and patient selection in my practice what I found is that have kind of a dichotomy I have one set of patients that will come in they know I do partial knees.
They want a partial knee. They want their perfect outcome. Quick recovery and they don’t want to hear about the downside to it. Then I have another patient subset who just you know has read about partial knees a read what’s on the Internet some bad experiences and they just don’t. I mentioned it and they just want to slap me and those are not those are certain patients that you may not even want to consider doing it anyway. The truth is really in the middle. And involves a shared decision making with the patient on one hand you have this possibility for early failure and a secondary surgery. And this issue of persistent pain which is somewhat complex and controversial but certainly an issue. And then on the other hand you have the things that we mentioned the benefits improve function proper reception. It’s a bone preserving procedure lower preoperative risk of complications and faster recovery.
I always tell the patients the stars have to align in order for this patient to be the right procedure for you has to be the right knee the right patient and the right surgeon the certain surgeon experience is critical with this type of procedure because technically it’s harder to nail this than it is a total knee and totally has a little bit of a fudge factor to it. This does not again in the indications by far the most important factor to achieve good outcomes with this type of procedure. I discuss those now. So the Kozinn and Scott criteria initially published 1989 subsequently modified I had the opportunity to work with Dr. Scott in fellowship just to talk about a few of the indications so isolated medial or lateral compartment arthritis as you can see here with the varus and valgus knee pattern weight less than 82 kilograms or 180 pounds arc of motion greater than 90 degrees with less than 5 degree of contractor and angler deformity less than 15 degrees which just passively correctable. So a case like you see on the right was severe various deformity and probably instability noted on X. These are cases you just can’t do a partial neon and just they’re not candidates and you shouldn’t consider them patella femoral arthritis.
We’ll discuss a little bit more about this in the future slides but just know that it’s for the most part of contra indication I would say a relative contra indication but certainly knees to be addressed knees to be considered and then inflammatory arthritis or things like rheumatoid psoriatic those are concerns and those are not those are contraindications to a partial name.
When you when you evaluate a lot of these indications, I think it’s you’ll find that these indications really are pointing towards not over stressing the implants these implants are not as robust as total arthroplasty components specifically the tibia. This is the weak link of of the surgery. And when you look at a total arthroplasty tibia for instance, you’ll note there is a large area a large surface area for fixation it’s covering the entire tibia. You generally have large keel sometimes even stems you can modify the implant to have stamina to improve fixation in the large in the large patient with partial knees are much more limited it’s about one third the surface area you have generally just uses a few small pegs and maybe a small keel for fixation. So the ability for these implants to stay fixed in certain quality of bone with certain patient types like large patients it’s not as good and it’s subject to early failure and that’s why indications are so important that’s why those indications are kind of gearing you towards a specific patient subset to talk about the subsets young patient really important one.
Originally this was a contra indication that closing and Scott criteria but that really creates a conundrum because this is again as we mentioned earlier this is a procedure in which its bone preserving improved function and an appropriate session relative to a total. These patients are if they have a partial knee their ability to return to discretionary activities like jogging cycling golfing is gonna be greater. So ideally that would be the perfect candidate that the young patient. But unfortunately, this this possibility for early revision is very real and pronounced in the literature. When you look at Swedish registry data it total knee arthroplasty and partial knee arthroplasty survivorship You’ll know here with total knees this is 2009 data. But then in the beige area the total the total knee survivorship in patients under the age of 55 at 10 years is approaching 8 percent.
You know pretty good survivorship and a young patient cohort. Unfortunately when you look at. That same beige area which represents the younger patient at 10 years the chance for revision is approximately 25 percent. And it’s important to note that this this type of data set is a heterogenous group of surgeons and patients so there are surgeons with varying levels of expertise. You can have general are a general or orthopedic surgeon. They’re not all arthroplasty surgeons. They may not be high volume partial knee surgeons but the important point here is to note that for all comers generally speaking partial knees in younger patients don’t last as long. Now this was again my mentor Dr. Scott. We evaluated his data and presented in the academy in 2014 and you’ll note at twenty-five years we achieved 75 percent survivorship which is really rather good in this.
These are patients under the age of 56. So I think this this kind of points to the fact that with good technique meticulous technique an experienced surgeon you can achieve excellent outcomes in survivorship even in young patients. So it’s again a bit of a dichotomy there but a heavy patient. So again we’re talking about overloading or overwhelming that implants. Keep in mind that concept but obviously these patients are going to present early and earlier in life just cause they’re loading their joints more and then of course when you implant a component such as an arthroplasty or in this case a partial knee there’s gonna be a propensity for early implant loosening and polyethylene where you have to be concerned.
There are many reports in the literature both supporting partial knees and the obese population BMI great and 40 and refuting it. So my and my synthesis of the literature the way at least I kind of perceive things is that the obese and inactive patient probably can achieve good survivorship and then the obese and active I get can I get more concerned about. But again that’s again my kind of synthesis of the literature. You have literature both supporting and refuting this concept. I think with the mesomorphic male or the large muscular guy it these are the patients I do become rather concerned about. These are weightlifters, joggers, runners, very active individuals are putting a large load and unload demand on the implants. I for the most part don’t offer these patient partial knees for that reason. I’m concerned about early loosing and failure or at least they have they have they have to have the expectation and understanding that these implants wouldn’t possibly fail early. So ACL deficiency it’s an important point and it has to be the right knee for all intensive purposes at ACL deficient knee is in the contraindications to a partial knee. It’s important understand this concept with ACL deficiency or insufficiency. You get posterior translation of the femoral condyle onto the tibia. In the case of a native knee this is going to cause a posterior wear pattern relative to the entire medial wear pattern we discussed earlier.
So does present a little bit differently ready graphically after a partial knee arthroplasty this is going to result in posterior translation of the femoral component and that’s going to result in loading of the implant in in a in a rocking horse phenomenon the implant contentiously loosens early in these cases. It’s important understand that these are not good candidates for partial knee arthroplasty there are there is substantial evidence supporting this concept of partial knee arthroplasty and concomitant ACL reconstruction. This is Simon Weston I’m sorry Western and Simon’s published excellent satisfaction in survivorship and 52 simultaneous ACLU UK reconstructions. This is definitely an option. This is a fluoroscopic analysis published by pandat and colleagues evaluating a partial knee arthroplasty with concomitant ACL reconstruction. I think the important point here is that a return and the knee can imagine to not to simulate the native knee with a partial knee an ACL reconstruction so it’s really rather impressive that with these types of procedures you can restore the native knee kinematics fairly well patella femoral arthritis.
So if you see this in the clinic is the patient a candidate for partial knee. I would say in most cases if it’s advanced radial graphically it’s probably a conference occasion there is literature support that you could you can potentially. Ignore this. My experience and probably most surgeons would suggest that if you have either moderate or worse patella femoral arthritis that these patients are not candidates for partially blasting lasting just to briefly discuss this concept of dual compartment medial patella femoral joint arcs of plastic. There are several implants in the market in my view these are rarely indicated I published on one of these implants in 2011 and it was fraught with some really poor clinical results and even catastrophic failure in several cases and in my hands this is just not even a consideration.
So it just did touch on implant pearls and some technical pearls. Briefly I think the point regarding implants is that this is a significant factor. There’s a lot there probably a multitude of different geometries and implants in the market. They’re really only several tried and true implants with a long-term track record. Some of the work we did years ago evaluated geometries of specific base plates and found that certain base plates had higher intrinsic stress and micro motion than others. And there’s this these directly we’re associated with good and or poor clinical outcomes specifically in the registry data. So implant design is really rather important and shouldn’t be ignored and shouldn’t be shouldn’t be just using any implant on the market. Brief technical pearls I think surgically a lot of surgeons want to maintain a minimally invasive approach with these surgeries somewhat contradictory because obviously we’d like to have less soft tissue disruption. On the other hand, it’s more important to implant these components correctly. So if your misalignment these implants are going to fail rather quickly. Specifically with regards to the tibia it has to be perpendicular to the coronial axis and then in line with the native slope on the sagittal view there is positioning in these implants as I mentioned before very not well tolerated all of it will result in result in early failure and loosening things like overhang as you can see here with the tibia will also result in a persistent pain and loosening.
Last point here technically when performing these or when implanting these components if you overstuffed or make that compartment too tight it can translate those forces to the controls compartment resulting in early wear and a progression of arthritis.
So it’s something to be to be cognizant of. So in summary I think partially the RS class is a fantastic operation and there’s definitely improved recovery improved proper perception a more natural feel relative to a total knee. Mainly because you’re preserving that ACL. It’s definitely bone preserving. So for the young patient although there’s a higher risk for failure is also the benefit of preserving bone the early failure is very real. It’s dependent on age activity level surgeon’s preference the size of the patient and then patient you know of course patient’s election as we discussed. Be cautious for the young obese and active ACL tear as contraindications patella femoral arthritis for the most part contraindications. Thank you. Look forward answer any questions you have.