“Cemented stems are versatile, surgeon-friendly, and mechanically sound.” says Arun Mullaji. Kelly Vince prefers uncemented saying, “There are times when cement is best, but for the vast majority of cases I find that uncemented, long diaphsyeal engaging stems are preferable.”
This week’s Orthopaedic Crossfire® debate is “Cemented Stems: A Requisite in Revision TKA [total knee arthroplasty].” For the proposition is Arun Mullaji, F.R.C.S.(Ed), M.S. from The Arthritis Clinic in Mumbai, India; against the proposition is Kelly G. Vince, M.D., F.R.C.S.(C) from Whangarei Hospital in New Zealand. Moderating is Leo A. Whiteside, M.D. of the Missouri Bone and Joint Center in St. Louis.
Dr. Mullaji: “Why should you use a stem in revisions at all? To enhance fixation of implants when there is Type 1 or Type 2 bone loss. If it’s more than that you’ll use sleeves or cones or other devices. Also, when you’re using a more constrained device you need better fixation.”
“I think there are five key benefits to cemented stems. They are versatile, particularly in altered patho-anatomy. Mechanically, they provide sound and immediate fixation with less stress shielding, stem tip pain, and a lower fracture risk. They help technically in facilitating balancing a much larger flexion gap, and they allow antibiotics to be mixed in the cement for revisions related to infection. Clinical results show that there is less loosening and radiolucency. Lastly, they’re surgeon-friendly (easier to insert or revise and cheaper).”
“We need cemented stems in Asia where we often see distorted anatomy in the form of saggital and coronal bowing of the femur, a larger valgus correction angle, and tibial bowing. We’ve reported these in our previous publications (Journal of Arthroplasty 2009 and 2013), both noting femoral bowing and valgus correction angle in our patients that can vary from 2-12 degrees. Cementless stems—or any other stems—can only provide 5/6/7 degrees of valgus. Lastly, metaphyseal or even diaphyseal bowing is common, and in our recent publication we’ve shown the influence of tibial plateau inclination.”
“So in these conditions if you use a long press-fit cementless stem you can have malalignment, penetration of the cortex, or periprosthetic fractures…and end up with a much larger flexion gap. When you put in a long cementless stem you are anteriorizing the femoral component, and you end up with a huge flexion gap.”
“Most of these cases require a revision on the femoral side. You have a trumpet shaped canal, and on the tibia you have ice-cream cone defects. This means that if you’re going to use a cementless stem you’re going to put in a thick, long one and fix it distally. That way you increase the length of the canal that you’re violating and you will have stress shielding. This was shown in the 2008 study by Completo et al. published in The Knee. They showed that the amount of load being transferred distally by the cementless stem is minimal—just 6% as compared to 24% with cemented stems.”
“Likewise on the femoral side, a short cemented stem can provide as good a fixation as a long cementless one. A 2012 study by Conlisk et al. in Bone and Joint Research showed that the relative motion is least for cemented stems on the femur. You have more stem tip pain with cementless stems—11-20%. There is also a much higher incidence of radiolucency (10-74% with cementless stems; 32-61% with cemented).”
“Most of our revision cases will have a larger flexion gap than extension gap. If you’re using a cemented stem you can flex it, posteriorize it, and close that gap. If you use a cementless stem—which is usually long—it will follow the bow and move the femoral component anteriorly. With a cemented one you can fudge and adjust it.”
“In infections it’s useful to be able to mix antibiotics with cement. And the clinical evidence shows a much higher loosening rate with cementless stems—7% versus 29% (Fehring et al., CORR, 2003). There is a much higher mechanical failure rate, with more re-revisions with cementless stems. Lastly, these are surgeon-friendly because they are easy to insert, easy to remove, a reduced risk of fracture, and they are cheaper.”
“There are caveats. Use mobile-bearing inserts to reduce fixation stresses on the bone-cement interface. Use the optimum cementing technique, and ensure accurate implant position.”
Dr. Vince: “We need to remember where the diaphysis is, as well as the metaphysis. Also note that the diameters of the funnel shaped bone differ significantly in these locations. In revisions I would opt for a diaphyseal engaging press fit stem; a metaphyseal length press fit is not recommended. What is necessary is some increase in fixation when constraint is used. I do agree that some kind of stem fixation is required in revision TKA.”
“By 1987 I was using the Insall Burstein modular revision system; by 1995 I had acknowledged that the short stems weren’t working that well. With failures you can either use more cement or you can use a different technique, which is what I chose to do.”
“The available research is full of bad information. The paper by Fehring et al. entitled ‘Stem Fixation in Revision TKA: A Comparative Analysis’ should be called ‘Metaphyseal Stem Fixation in Revision TKA: A Comparative Analysis.’ They’ve excluded the diaphyseal length stems. And they had higher failure rates with their uncemented stems, but they weren’t long enough.”
“The Mayo Clinic study by Shannon et al. (JOA, 2003) again shows metaphyseal length stems with a 10% failure rate…I’d stop doing it if I had a 10% failure rate. Their lengths were too short; the fill of the canal was too narrow.”
“The technique would be 145mm stem on the tibia, 200mm on the femur. When you do revisions involving big deformity you really need to fully cement a shorter stem to get the alignment that you want. Metaphyseal fully cemented stems are a reasonable choice if you’re very concerned about loosening. I’d favor the diaphyseal length stems to guide position and enhance fixation. My colleagues and I have studied the technique. The tibia is an asymmetric bone, and the stem is best placed in an asymmetric medial position.”
“I also found that I could manipulate femoral position by eccentric reaming. If you use a straight stem on the femur it may not be in the correct position, but we can increase valgus by reaming eccentrically to the lateral side. If you use a straight stem with this technique it will overhang on the lateral side. But if you ream eccentrically to the lateral side you can increase valgus with a long stem; then you can centralize the component by using an offset stem.”
Moderator Whiteside: “Arun?”
Dr. Mullaji: “If you have access to offset stems I think you can modify your reaming technique and you can use long, cementless stems. The problem is that in our part of the world you often don’t have offset stems available…they also add an expense. What about the larger flexion gap? You’d need to use offset stems to do the same thing. So when you’re dealing largely with the older population, low demand, osteoporotic patients you don’t want to put in these long, thick stems which are likely to fracture the bone…then have a problem with mismatch of your flexion and extension gaps.”
Moderator Whiteside: “Kelly, your rebuttal?”
Dr. Vince: “Leo, I don’t want anyone using fully cemented stems for the wrong reason. The majority of revisions done with fully cemented smaller stems are actually put in the wrong position. The component is floating around the cement mantle, and the surgeon is poorly informed as to where it should be. The diaphsyeal engaging stem actually guides you. But if you have to remove a fully cemented stem you may believe Arun that it’s easier to take out…but come and talk to me after you’ve tried it.”
Moderator Whiteside: “I couldn’t agree more. Arun, when you get an infection in these cemented, pressure-injected stems how do you get that thing out of there?”
Dr. Mullaji: “If it’s an early infection then I’ll use your technique and put in these antibody infusions. It can be challenging to remove, but it’s not difficult in an infection situation. If it’s uninfected, yes.”
Moderator Whiteside: “‘Infected’ was my question.”
Dr. Mullaji: “By the time most of these patients come to us they are already loose.”
Dr. Vince: “We have a strong bias in our literature against publishing bad results, and I’d suggest that there is no publication of the treatment of infected fully cemented long stems because the results are bad.”
Moderator Whiteside: “Kelly, you use cementless long stems often. Do your patients have end of stem pain?”
Dr. Vince: “If you say you have a patient with an uncemented stem that is diaphyseal engaging with this technique with end of stem pain, you’re going to have to prove that the component is not loose before I believe that there’s end of stem pain. There is no good study on end of stem pain.”
Moderator Whiteside: “And you have no anecdotes where you removed a stem or cut a stem in two because of end of stem pain?”
Dr. Vince: “No.”
Moderator Whiteside: “I must say that I do. Thank you both.”
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