This week’s Orthopaedic Crossfire® debate was part of the 32nd Annual Current Concepts in Joint Replacement® (CCJR), Winter meeting, which took place in Orlando this past December. This week’s topic is “The Use of Stems in Complex Primary TKA: Necessary & Sufficient.” For the proposition is Kelly G. Vince, M.D., F.R.C.S.(C), Whangarei Hospital, Whangarei, New Zealand. Opposing is Thomas P. Sculco, M.D., Hospital for Special Surgery, New York, New York. Moderating is Aaron A. Hofmann, M.D., Hofmann Arthritis Institute, Salt Lake City, Utah.
Dr. Vince: I think Tom and I are very close on this. I think Tom would agree that we don’t want anyone leaving the room thinking quite simply ‘Constrained implants don’t need stems across the board.’ That’s not what this discussion is about.
It is about primary total knee arthroplasty in the situations where there is good bone, good quality and good quantity and that are specifically complex because of deformity or instability. Personally, no matter what the type of complexity I’m approaching, if I use a constrained implant, I will always use a stem.
I find it to be an easy conversion to a constrained device by deepening the keel hole, deepening the intercondylar notch, and then fully cementing a short stem extension. These can easily be adapted and they do not compete with what the instruments have given me for the cuts. In cases of larger deformities, the ligament environment is challenging and so I would use fully cemented stubby stem extensions as well, often harvesting bone from the distal femur for use as graft material.
But I do want evidence that constraint with a standard femoral component is safe.
In 2006, a cohort of patients reported no loosening or wear, using a constrained device with no stems. In 2007, 2 to 6 year follow-up, very reasonable. The failures were very modest, I would have to agree, in Tom’s series. Two of them, one loose femoral component and one supracondylar fracture, however, I would argue would have been preventable with stem extensions. In 2012, revision rate was 4.2%, which is not bad at all in these difficult cases. But the most common cause was femoral component loosening. And I might argue that stems could have prevented those.
Tom, I think, will be able to update us on what I think is the most recent report on constrained devices without stems, but we’ll leave that up to Tom.
There is a very good paper recently in The Knee which deals with another issue—the use of patellar buttons and they made a very straightforward economic argument.
The cost of the total knee arthroplasty was $13, 788 over time, when you include the cost of additional revisions or secondary surgeries for the button. When you did not resurface the patella, the secondary resurfacings drove the actual cost of the operation up to $14, 000. Now they weren’t arguing necessarily that you should use the button or not, but they were arguing that if the revision rates remained below a certain threshold—3.54%—for patellofemoral resurfacing and above 0.77% for non-resurfaced patellae, that a difference in pricing was appreciated.
So, stem extensions do bear a cost and this economic analysis should be considered.
In conclusion, I would say stems in complex total knee arthroplasty are necessary in the way that lifeboats are necessary, even though they’re not used. In the way that child seats are necessary when we are making decisions for people who can’t make those decisions for themselves.
I would disagree, however, with the statement that stems in complex total knee arthroplasty are sufficient by themselves. I think they should be short. I think they should be fully cemented. I think the alignment definitely has to be controlled. So stems by themselves are not going to solve problems. I recommend that we use additional fixation with constraint in the complex primary total knee arthroplasty. And I would strongly recommend that we exercise caution if we put in constrained devices without additional fixation.
Dr. Sculco: I’m going to talk about the use of a constrained condylar knee without stems and give you some of our results and some of the problems we’ve had as well.
The indications for a constrained condylar knee, as Kelly has pointed out, is a complex primary knee or revision knee, where there is also bone deficiency potentially and ligamentous damage. I would say, right off the bat, that stems are needed for most revisions and I would not want anybody to leave this room and feel that I do not believe in that. And the stem fixation can either be partially cemented or fully cemented as Kelly has pointed out.
What about the potential of a CCK in the primary knee. Well, when you get a knee with severe deformity, bone loss, and/or ligamentous problems, augmentation will be needed. Stems work very well in this setting. There are results, if we look in the literature, with stem fixation for the complex primary knee as well as the revision knee.
But there are disadvantages to the use of stems. About 20 years ago, I said to myself, “Well, maybe we don’t need to use stems in everybody. They’re expensive. They do add $300-$400 to the procedure. They violate intramedullary bone, they make the revision more complex if you have to come back again. And with all the finagling in the stems, sometimes they will add additional operating time.”
In a patient from about 20 years ago, who had deformity was post traumatic, and the medial collateral ligament was not great, I did an IB knee without using a stem with good clinical outcome. And about that time, Bob Booth reported on a series of the same thing—the IB knee without stems, and he compared them to a stem cohort and they were about the same, and those without the stems, in fact, did very well.
The caveat or indications for not using a stem are that you must have good femoral bone. This is not a knee that you would use in a severe revision without good bone. You need good fixation of that device into the femoral bone and you cannot use it if you’re going to use femoral augmentation because you should use the stem particularly in that case.
Well who is it ideal for? In my opinion, primary knees which have severe angular deformity and instability, and that’s particularly the valgus knee. And the revision knee without significant bone loss, particularly a uni-compartmental or a PCL retaining knee.
When we look at our mid-term results—and Kelly mentioned them, 146 knees—most were female. Most were older and primarily I was using the IB without a stem in the older female patient with a severe valgus knee, where there was medial insufficiency, the ligament was there but it wasn’t fully competent.
So we followed them up and actually accreted the scores at four years—it was a relatively mid-term follow-up out to six years—and the results were pretty good. The Knee Score went from 36 to 89, we had some revisions— about 3%. One loosening at that point in time.
So we felt pretty good about it and we then continued with a second review of 31 patients now, follow-up for a minimum of 10 years. Our follow-up with these patients continues because we’re noting some increased problems as we go forward, which I’ll talk about briefly.
The Knee Scores did decline a little bit as patients got older, 92 to 80. The function score was down a little bit too, 74 to 68. Again, the patients were getting older, but the range of motion was preserved in this population.
We had some problems, as I said, and we’ve had some radiolucencies which are worrisome, but did not lead to failure. The biggest source of problems has been femoral failures and we’re probably about 4-5% now at 10 years as we continue to follow these patients.
Now this is a very severe group, so that’s probably not a very unacceptable follow-up at this point in time with this device.
There are relative contraindications for use of the stemless femoral component – the very heavy, obese patient, patients with severe osteoporosis, very active patients and younger populations should not use it.
In summary, the CCK without stems has shown satisfactory results. Not as good as primary knees at 10 years, but these are more severe knees. You’ve got to have good femoral bone. And the ideal patient is a patient who has good bone, with severe deformity particularly valgus knees.
Moderator Hofmann: Let’s just talk about the tibial side. Do you have the same feeling there on the tibial side, that don’t use a stem, don’t use a long stem? Or are you really just talking about the femoral side?
Dr. Sculco: We’re just talking about the femoral side. Tibial side I would use my standard stem. If you notice when I use this, I tended to use a 25, small little buttons at the end.
Dr. Vince: I would apply the same thinking for the tibia. I would put a stem extension of some description if I have used constraint. If I’m increasing the load on the fixation, I’m going to increase the fixation.
Moderator Hofmann: How about the recent information that we heard at the interim meeting of the Knee Society where heavy patients should have stem extensions? So the patient that has a BMI [body mass index] over 30, put a little stubby on there, or what’s your feeling on that whole concept of stubby stems on stem extensions on heavy patients on the tibial side?
Dr. Sculco: I think obese patients, and it was documented as we continue to follow these patients, did less well. I think if I have a super obese patient and I’m just doing a primary knee, I’ll oftentimes now use stem extensions as part of that procedure.
Dr. Vince: I think, Aaron, you’re talking about the stubbies for chubbies movement.
Moderator Hofmann: Are you saying that I fit that movement?
Dr. Vince: I think the reason our patients with elevated BMIs suffer failures is due more to wound healing problems, infections or kinematic failures. Because the surgery is more difficult for us to do, the exposure is more difficult. So they end up stiff, they end up unstable, they end up mal-rotated. They don’t really end up loose, because they’re not that active. It’s the 150-pound person who might be pounding the pavement, running, climbing mountains. People with a more sedentary lifestyle don’t suffer loosening. I think that’s a misconception that we have about the heavier patient.
Moderator Hofmann: In terms of the kind of stem, where is all that going?
Dr. Sculco: I think it’s a good question Aaron and if you’re going to use a non-cemented stem, that should be fluted, so you get a good…
Moderator Hofmann: And long.
Dr. Sculco: And long. I use 80mm on the tibia usually and 120mm on the femur. If you’re going to use a cemented stem, it should be smooth because it’s very, very difficult to get a cemented fluted stem out. So if you’re going to use a cemented stem, it’s fine, but make sure it’s a smooth stem. Otherwise you’re going to need an osteotomy to get it out.
Dr. Vince: The two strategies that are available, Aaron, are fully cemented shorter stems, just like a total hip. Or if you’re going to use an uncemented stem, it has to be engaging. If you use a long stem in a primary, your primary instrumentation’s not going to agree with the stem position. So that’s why in a primary I would use a small stem and in revision I would use the long stem.
Moderator Hofmann: Thank you to both of our panelists very much.
Please visit www.CCJR.com to register for the 2016 CCJR Winter Meeting, – December 14 – 17 in Orlando.
