David Stulberg vs. Robert Bourne Over Stubby Stems

“Short stems work, ” says David Stulberg, “and they are associated with very good bone remodeling.” Robert Bourne counters, “But we don’t even have studies where they have varied the stem length to see if the outcomes are similar. This issue is more complicated than Dr. Stulberg has presented.”

This week’s Orthopaedic Crossfire® debate is “Stubby Stems: When Less is More.” For the proposition was S. David Stulberg, M.D. from Northwestern University Hospital in Chicago. Against the proposition was Robert B. Bourne, M.D., F.R.C.S.(C) of the University of Western Ontario; moderating was Cecil H. Rorabeck, M.D., F.R.C.S.(C) of the University of Western Ontario. 

Dr. Stulberg: “We should begin by recognizing that cementless femoral stems have a variety of shapes and sizes and design rationale and they have worked terrifically well in all patients. But there are issues. One is the desire to optimally load the proximal femur; another is to deal with proximal deformity and proximal-distal mismatch. Extreme cases can be handled with a short stem, but the more common problem we face is young, active, large males with large metaphyses and narrow diaphyses. These can get us into trouble…but can easily be solved with short stems—if they worked.”

“The real issue is…exposure. Anterior approaches need something other than long stems to facilitate their use. So the hypothesis is that substantial reduction in stem length would not alter the stable fixation and reliable bony ingrowth of an implant designed to fit and fill the proximal femur. My initial experience was in relatively younger patients with good bone. I’ve had 2-4-5 year follow up. I used a custom implant to define the problem. In other words, I used one that I knew would fit proximally. We had a lot of experience with bone remodeling. Our DEXA scans showed that bone remodeling proximally was good, and that fixation was impeccable.”

“These results have been presented in Orthopedics in the last couple of months…no news…they work well and haven’t failed. In terms of fixation they function like normal hips. The next step was to take an off-the-shelf device that was very similar in concept, ask the manufacturers to get rid of the length of the stem and see what happened. I used them in all comers, and the results are the same as they were with customs. My conclusion was that short stems work, that the stems have identical clinical outcomes, and are associated with very good bone remodeling.”

“From Europe are coming a variety of stems…you could classify these a lot of ways. You could call them, ‘shortened standard’—the Biomet microplastic is an example of that. They just cut off the stems…those will work if the fixation that was the basis for their use as a long stem works as a short stem. But the high neck stems are the ones that we’re going to have to think about. These can come in two varieties: involving more than 50% of the high neck or less. That doesn’t necessarily mean that the cut is high…what it really means is that the lateral cortex is kept intact. That is a little different than what we’re used to.”

“In addition, you can have fixation of different types: multiple point contact or circumferential contact. This can be done through a high neck approach where you preserve the lateral cortex.”

“These stems must have reproducible technique and a short learning curve, secure initial fixation, durable fixation, optimum offset, and good bone remodeling. In the future we’ll see extensive proximal contact, neck sparing, extend to or engage the metaphysis, probably modular necks, all head sizes, instruments for all approaches…and they should be revisable.”

Dr. Bourne: “I have the greatest respect for Dr. Stulberg, but think the importance of femoral stem length in THR [total hip replacement] is perhaps not as simple as he has made it out to be. There are no studies I know of that have varied the stem length to see if the outcomes are similar. And there are a lot of variables to consider…there are many ‘stubby stems.’ These are important: stem length and design, femoral neck preservation, patient factors, bone quality, and activity level. To be fair, we’ll go over these issues: is the stem necessary for ingrowth, bone stock variation (varies greatly), are they MIS friendly? Do they cause less stress shielding? Do they cause less thigh pain?”

“Regarding whether a stem is necessary for proximal ingrowth, that’s tough. We need some good studies like radiostereometric analysis (RSA). When you go to a short stem you sometimes have problems with alignment. In one study by Nivbrandt he looked at one particular short stem—which didn’t look that dissimilar from what David was describing—and concluded that he had good fixation. When I look at subsidence and varus/valgus migration, I agree…it looks pretty good. But when I look at outer plane rotation I get concerned. At two years there’s a progression and perhaps retroversion of the stems.”

“MIS friendly? Perhaps. But I think the bloom is coming off MIS surgery in general. As for whether there is less stress shielding, as soon as you put a stem down the medullary canal, you load it very differently and you get a reversal of the stress patterns. We published on this years ago.”

“Less thigh pain? Again, we need good studies. Dr. Steve MacDonald presented our data on two types of conventional total hips, and we need to do the same for short stems. Dr. Pipino reported a 14% prevalence and that’s a bit concerning and is higher than we’d have with conventional stems. But it may be only for that stem.”

“Equivalent outcomes? We need a comparison group—level one versus level four clinical data. Even if you did cohort studies…we need not depend on case studies. When you look at over ten year outcomes the data is skimpy. In Professor Pipino’s study of 56 total hip replacements, 12 were lost to follow up and 44 were available at 13-17 years. His results were reasonable, but the short stem led him to put some stems in valgus, some in varus; thigh pain was 14% (he claims it resolved…we don’t know). Only 82% had satisfactory Harris Hip Scores.”

“Dr. Morrey’s study: perhaps a little better study, published in the Journal of Bone and Joint Surgery. Much better follow up, but only 6.2 year mean follow up. He had significant revisions: 3.7%…not terrible, but it hasn’t revolutionized care at the Mayo Clinic group. So even though short stems are worth looking at I think we should proceed with caution. Published series of short femoral stems have revealed increased complications. There’s a downside in perhaps inferior fixation, more revisions…and we’re not even dealing with the neck preserving implants. Thank you.”

Moderator Rorabeck: “Thanks, Bob. That was excellent. David, could you define what you mean by short stem?”

Dr. Stulberg: “One in which the stem reaches the metaphyseal/diaphyseal junction, which in practical terms means that it’s somewhere between 95 and 105mm long.”

Moderator Rorabeck: “Bob?”

Dr. Bourne: “I don’t see much advantage going to just a shorter stem. I would be looking at more of the stems like the mid-head resection or something like that where you preserve the metaphysis and diaphysis. But if you had to do a revision joint replacement later, they’re primaries.”

Moderator Rorabeck: “David, the genesis of this has come from your love of the anterior approach, and trying to find a stem that you can get in nicely that way. And this seems to solve that problem, I would guess.”

Dr. Stulberg: “If you go anteriorally you need a stem that accommodates that, and there are other ways to go, but certainly the stem in an anterior approach can be aggravating. If we can shorten it and not lose reliable fixation then I think it’s useful.”

Moderator Rorabeck: “It seems like a good thing on an anterior approach. What would you say to a surgeon who only did posterior approaches?”

Dr. Bourne: “It’s hard to generalize…to say that just because you see that one particular stem that Dr. Nivbrandt studied and what appears to be rotational instability. Whether you could apply that to Dr. Stulberg’s stem or other stems…but those studies need to be done because we’ve come a long way in total hips, with 97/98/99% survivorship at 10-15 years of our conventional stems. So before we venture off into something else we have to be cautious.”

Dr. Stulberg: “I want to emphasize that if you’re going to get into high neck designs you can’t see below the head resection level, and you’re setting yourself up for rotational instability. If that was the problem with the Pipino stem, it may be an issue with these point contact high neck devices. So my point was that if you can get circumferential contact that is the safest way to go if you’re going to a short stem. But I absolutely agree with you, Bob.”

Moderator Rorabeck: “David, it seems that to get maximum rotational stability it’s probably advantageous to preserve a bit more neck than usual—but that may open up more problems.”

Dr. Stulberg: “That was my point in showing you how I use these high necks. If I were recommending a short stem and high neck device I would use one that actually violated that lateral cortex. The concept of a high neck resection is fine, but the real issue is getting circumferential contact proximally.”

Moderator Rorabeck: “Bob, the other thing is that it’s hard to go anywhere in the world where you’re not seeing new types of short stems. Where do you think it’s going to go?”

Dr. Bourne: “If we design a stem in North America or Europe and we try to put it in people in Asia they’re way too long. There’s little data—cemented or cementless—on what the length of the stem needs to be. I think we’ve accepted this—maybe too long—and I think studies such as David’s stimulate us to look at this issue.”

Moderator Rorabeck: “Interesting. Thank you both.”

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