“Cemented stems in revision TKA trump press fit stems, ” says Thorsten Gehrke. “With fully cemented stems, ” says Kelly Vince, “if you assume that you don’t have to worry about position you’ll be disappointed in a high percentage of fully cemented stems.”
This week’s Orthopaedic Crossfire® debate is “Cemented Stems: A Requisite in Revision TKA.” For the proposition is Thorsten Gehrke, M.D. from ENDO-Klinik in Hamburg, Germany; against the proposition is Kelly G. Vince, M.D., F.R.C.S.(C) from Whangarei Hospital in New Zealand. Moderating is John J. Callaghan, M.D. from the University of Iowa.
Dr. Gehrke: “The rationale behind stems in revision total knee arthroplasty (TKA) is that it needs additional component fixation because the stem is able to bypass the deficient bone and transfer load to the diaphysis. A 70mm stem can reduce the tibial plateau load to 38%. But the general question is, ‘Shall you do it in a press fit way or fully cemented?’”
“I have 10 reasons why it’s good to have fully cemented stems.
- Number 10: Fully press fit is not possible due to the femoral anatomy. The distal femur is bowed and you can’t get a good press fit in the femur. Even on the tibial side, cemented stems show significantly less micromotion.
- Number 9: Cementless press fit stems are predictors for the knee axis. This is a problem in deformities like varus deviations.”
- Number 8: Removal of well-fixed cementless stems can be a problem in some models.
- Number 7: End of stem pain. Robert Barrack et al. (Clinical Orthopaedics and Related Research, 1999)reported that up to 20% of patients had end of stem pain with press fit stems. This never happens with fully cemented stems.
- Number 6: Changes in bone mineral density (BMD). Jensen et al. (Journal of Orthopaedic Traumatology, 2010) showed that with press fit stems you have a significant increase of BMD; but after one year there are no relevant increases. In the proximal tibia they found temporary decreases of BMD of 4%.”
- Number 5: Cemented stems provide better load transfer to the diaphysis than press fit stems (Completo et al., The Knee, 2008). Their finite analysis on the femoral side showed that a cemented stem reduces load up to 58%, whereas the press fit stems reduced it only to 18%. On the tibial side, the load transfer with cemented stems are much better (24%) than with press fit (6%).
- Number 4: If you use cementless revision stems then you need a lot of trays and you have almost no place to operate. With a fully cemented stem you only need one tray.
- Number 3: There is a higher interoperative fracture rate with press fit stems. Cipriano et al. (Journal of Arthroplasty, 2013) reported 4.9% tibial and 1% femoral fracture rates with press fit stems. This is nearly unknown in cemented stems.
- Number 2: With antibiotic loaded bone cement we have much better protection against periprosthetic joint infection. This was proven by Mader et al. (Antimicrobial Agents and Chemotherapy, 1997) because there is the phenomenon of the elution of antibiotics from the bone cement.
- Number 1: Do we have better survival of press fit stems or fully cemented stems? Fehring et al. (Clinical Orthopaedics and Related Research, 2003) compared 107 cemented stems to 95 press fit stems. He found significantly higher loosening rate in the cementless stems than in the fully cemented stems. But if you go through the literature we see that Dr. Fehring is alone. Based on the current literature there is no final statement that can be drawn regarding the optimal fixation technique in revision TKA.
But I go with the guys from Mayo Clinic who say that ‘the cemented stemmed revision TKA is superior to that of revision TKA with press fit stems.’”
Dr. Vince: “‘Requisite’ means ‘necessary’ and I think we’d all agree that this is not the case here. Stems, however, need some definition. When we talk about cemented stems in revision I think we’re actually referring to fully cemented stems.”
“When it comes to the diaphysis and the metaphysis, the big difference there is the diameter, the former having a less tapered diameter. This is critical when we’re thinking of not cementing the stems (and I don’t mean ingrowth stems). Our choices for knee revision surgery are fully cemented (short-stubby or metaphysis) or uncemented (diaphyseal). In a patient with a severe bow to the femur I would use a short-stubby; if I had used a press fit stem there it would have gotten in the way of the alignment I wanted. In a patient who had serious problems with loosening I used a metaphyseal…I fully cemented it. But 85% of the time I do press fit diaphyseal engaging stem extensions.”
“They’re not fully cemented and are thus easy to remove if necessary. They also guide alignment. As for a metaphyseal press fit stem, the results are poor. So at least some kind of stem is requisite in revision. I began doing revisions with the Insall Burstein I and thought we could conquer the world. By 1995 however, I had published a paper on the limits of press fit medullary fixation. There were many cases of loosening, and these were all metaphyseal engaging stems.”
“Tom Fehring’s work—Stem Fixation in Revision TKA—should include the word ‘Metaphyseal’ because they excluded the diaphyseal length stems. They found more loosening amongst the uncemented group on the tibia, and more loosening amongst the uncemented group on the femur. And Mayo Clinic should have used the word ‘metaphyseal’ in their study—Revision TKA with Cemented Components and Uncemented Intramedullary Stems. Their loosening rate was 10%.”
“More recent data on metaphyseal cementing with stems without cement by Chris Peters (Journal of Arthroplasty, 2005) is reliable. The technique includes taking care of the anatomy, so I use offset stems to match the tibial anatomy when I can. When I can’t I fully cement a smaller stem. An important technical aspect of this surgery is that the entry point be correct. Look at the prosthesis you’re using, and with, for example, one that is designed anatomically, it requires an anterior entry point. If you’re using the offset stems to shift the component front to back that means you have the wrong entry point.”
“Uncemented stems are more technique dependent. When faced with varus bows I would recommend that depending on your goal, you either ream eccentrically to the lateral side for more valgus. If we put a straight stem in that configuration that would lead to a component overhanging on the lateral side. So we’d use the offset to centralize the component. We would ream medially if we want to reduce the valgus and when we’re caring for someone with valgus instability.”
“We do use cement. For example, there is a little cement on the cut bone surface; the stem goes down into the canal without cement and then cement is injected around it in the metaphyseal area. But there is not cement at the tip of the stem. I would like to see a cement mantle that is at least equal to what I do in a primary.”
“We are trying to avoid these very long, fully cemented stems so we use trabecular metal. Trabecular metal provides excellent initial fixation, and you can even fully cement shorter stems if you’re certain of the alignment.”
“So I recommend stem extensions for revisions, long stems for press fit, shorter stems for full cementing, trabecular metal cones for problem cases, and try the press fit trials to guide your alignment and position. Choose the augments to maintain the position, and then fully cement a shorter or smaller diameter stem.”
Moderator Callaghan: “Thorsten, any comments?”
Dr. Gehrke: “The offset stems are variable in some cases, but if you use one you should never fully cement them because they’re a nightmare to remove. Your revision is more likely to succeed if, when you cement an offset stem, you just cement the metaphysis.”
Dr. Vince: “There would be no reason to use an offset stem if your technique was full cementation.”
Moderator Callaghan: “Thorsten, would you review why you don’t need offset stems with cement?”
Dr. Gehrke: “In the majority of my revision TKA cases I don’t need offset stems. The alignment doesn’t depend on the offset of the stem, it depends on the soft tissue, bone cuts, and entry point, etc.”
Moderator Callaghan: “That’s the thing with the cemented stem…you can put it where you want it.”
Dr. Vince: “You can place it where you want it, but if you assume that you have some type of stem where you don’t have to worry about position you’ll be disappointed in a high percentage of fully cemented stems.”
Moderator Callaghan: “Kelly, if you look at first round of cement versus cementless stems I’d say cement won.”
Dr. Vince: “There are still cases that are better treated with fully cemented stems. The majority of revisions that are being done with uncemented stems are done inadequately and are consistent with an ineffective technique from a decade ago. These are shorter stems, they don’t fit, and they don’t go in with the right trajectory with the canal. The presence of a stem doesn’t mean that we don’t need tremendous fixation distally. So if I can take a trial component on and off distally…if I don’t have a pinch fit on the residual bone, I’m not happy. I need a pinch fit with my augments on a femur; I need a pinch fit that requires a mallet to drive that component home.”
Moderator Callaghan: “Thorsten, it’s almost impossible for you to fracture a canal with cement, right?”
Dr. Gehrke: “That’s not a technical issue. It’s almost impossible.”
Moderator Callaghan: “So we’ve gone to tightening up stems. In addition, we’re adding these metaphyseal sleeves. How do you know if you’re too loose, too tight, or just right?”
Dr. Vince: “If you’ve cracked diaphyses and metaphyses it’s likely with no consequence because you’ve bypassed it. Also, when reaming the femur we want surgeons to keep their hands up, not drop the reamer, because you must be parallel to the shaft of the femur. If you drop it down you can’t make it fit. And we don’t want the trials to be removable by hand. The issue we really need to address is end of stem pain. You first have to prove it’s not loose. In the paper that was quoted they compared cemented versus uncemented on the tibia; cemented tibial stems have the highest incidence of end of stem pain. They made no comparison of cemented and uncemented on the femur.”
Moderator Callaghan: “Thorsten, can you give us your techniques for removing cemented stems?”
Dr. Gehrke: “It’s always a question of training. To remove cement from the tibia or femur is much easier from the knee side than from the hip side. You need a range of different instruments and then it’s not normally an issue. But if the bone is deficient/thin then you could fracture the bone during the cement removal.”
Moderator Callaghan: “Thank you.”
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