“My message is that the short tapered titanium porous plasma sprayed femoral component is efficacious, with less than 1% stem revisions if we look at revisions related to the stem, ” says Adolph Lombardi. Leo Whiteside counters, “Despite the literature we must be careful here. I know a lot of good guys who have tried and failed with fractures, migration, and loosening. Let’s avoid the learning curve.”
This week’s Orthopaedic Crossfire® debate is “The Short Stem: Emergent Solution for Primary Hip Problems.” For the proposition is Adolph V. Lombardi, Jr., M.D., F.A.C.S. from Mt. Carmel New Albany Surgical Hospital in Ohio; against the proposition is Leo A. Whiteside, M.D. of the Missouri Bone and Joint Center in St. Louis. Moderating is Thomas S. Thornhill, M.D. from Harvard Medical School in Boston.
Dr. Lombardi: “Not all short stems are created equal: there are short and bulky, short tapered, the ‘Mayo Influence’ stems, and the neck sparing stems. There are multiple reports showing short term follow-up (2.7 years and 8 years on an ultra-short stem) but no stem revisions. For the DePuy Proxima Stem it was the same in different studies (1.7, 2.2, and 4.5 years). The Mayo Stem didn’t do as well—even in the hands of the designer (9% stem revisions). So we’re seeing small series in the literature, but what’s emerging is more and more stems that are FDA approved.”
“A 2013 review article by Banerjee included 22 articles; the researchers found that ‘midterm survivorship of short stems has thus far been comparable to traditional stems’. Follow-up was four years. In a 2012 article by Rometsch there were 14 articles reviewed involving 7, 000 devices; they had a revision rate of 0.38 per 100 component years.”
“What’s the length of a standard stem? If the goal of the tapered stem is to preferentially load the proximal femur, then why do I need a long stem? Short stems comply with that proximal loading theory of tapered stems. In McLaughlin’s 2010 series he used a device known as ‘reduced distal’ so that he wouldn’t get the stem impinging distally.”
“Why do you need a stem? Maybe to prevent varus…but in our series varus stems did as well in this porous plasma-sprayed device as did the straight stems that were neutral. Also, if you use a varus stem you can accommodate some femoral deformities, as well as a proximal-distal mismatch. Also, they violate less bone and revisions are easier. Short stems facilitate a shorter incision surgery as well as procedures like the anterior supine intermuscular.”
“Our experience in over 2, 450 cases has been excellent. Also, when I looked at my series of long stems compared to my short stems I found that I was having a few more problems interoperatively with my longer stems than with my short stems. From January 2006 to April 2013 we did 2, 457 of these surgeries. We had to revise 35; our biggest nemesis was infection (15 of the 35). The second biggest issue was periprosthetic fractures. In some patients we noticed a distal hypertrophy, so we modified the stem to reduce the distal part. We looked at 100 of these short stems that were the standard and then 100 that were reduced distal, and we classified the amount of distal canal fill. We found that by reducing the distal portion we had now decreased the amount of what I call ‘grade three’ canal fill (distally) down to 12%.”
“So my message is that the short tapered titanium porous plasma sprayed femoral component is efficacious, with less than 1% stem revisions if we look at revisions related to the stem (i.e., not including infections).”
Dr. Whiteside: “Remember that the femoral forces are high: 250Kg of axial load offset and 2.5 KgM of torsional load. Bone ingrowth occurs only if you keep the micromotion less than 20 microns at that interface. It’s achieved primarily by proximal fixation (wedge or collar). Fixation depends on a tight distal diaphysis, and the length of the stem. It also depends on torsional load bearing, the femoral neck, and diaphyseal cortical interlock.”
“Total surface area is very important. I have settled on a tapered rough porous proximally coated implant that is rectangular and long enough to engage the diaphsys and support the implant. Whether you have a wedge or collar, tight or loose fit distally makes the difference at low and high loads. Tightness or looseness distally controls axial motion. Torsional micromotion is another matter. One of my fellows found that torsional micromotion is very poorly controlled by the standard round stems that you see all time. Part of that is because of the resection of the neck. Michael Freeman showed us that if you resect the neck you lengthen the lever arm that the load is applied to and you shorten the lever arm that resists it. A quick lab test will show that torsional load to failure is much higher if you keep the entire neck and much lower if you resect the neck.”
“If you cut the stem in two you get three times more micromotion at the interface. I lean more toward a rectangular stem that has various sizes that allow me to get that tight distal fixation. Even in Dorr type C bone if you concentrate on getting tight distal fixation, torsional micromotion is minimized well below the 20 microns of interface motion.”
“Preserve the neck and don’t worry about incision length. Preserve the bone, not the skin. Even in soft bone you can still preserve the neck and end up with excellent fixation. Continue to compact and fit proximally first, maintaining the neck—especially that medial and posterior cortex. Then size distally. The final implant is made to fit that broached cavity…rectangular for scratch fit distally…proximally porous coated and made to fit in a femoral neck. Then you get a short lever arm that applies the load and a long lever arm that resists the load…and a tight fit in the canal. You do end up with a little proximal stress relief, but you don’t end up with a varus femur even if you try to varus it.”
“The literature looks good for short stems. However, with a few phone calls I found out that we have a problem. I know a lot of good guys who have tried and failed with fractures, migration, and loosening. That suggests that we need to be careful; let’s avoid the learning curve here…and avoid ‘minimally invasive’ anything. Use an extensile approach, and use an implant that is fixed proximally and distally for both axial and torsional loads that you can do right every time.”
Moderator Thornhill: “Adolph, now that people are pushing anterior hips and other minimally invasive approaches. Do you think it’s right to shorten the implant because of your approach?”
Dr. Lombardi: “Leo is right…don’t do a minimally invasive procedure because of the implant. If you’re driven to make a shorter incision I suggest you get comfortable with whatever device you’re going to use in that shorter incision with your standard approach and then go to your different approach. I’ve done many of these shorter stems through a direct lateral approach, and now I’m doing an anterior supine intermuscular on about 25% of my patients. But I can still use the longer stem…the incision would have to be longer.
Dr. Whiteside: “If you have a longer stem and you decide you’re not getting enough fixation then you can put in a longer stem. I’d suggest some corners on that stem of yours. Round is kind of dangerous in the femur because it can slide around. I like to see edges that get cortical purchase distally.”
Dr. Lombardi: “I use a porous plasma spray stem that’s been on the market for almost 25 years. It’s got a roughened surface, it’s rectangular, and the amount of porous coating in the short stem is identical to the amount of porous coating in the long version of it.”
Dr. Whiteside: “The amount of porous coating is important.”
Dr. Lombardi: “I would challenge you on that grit blasting distally. That is a pain in the rear. Why do we need that? And if you ever have to remove one of those stems you’d better know that it’s grit blasted distally because you’re going to have to do a very long osteotomy.”
Dr. Whiteside: “You need that because it improves fixation and if you get osteolysis proximally then it’s nice to have a well fixed implant that you can salvage.”
Dr. Lombardi: “If you didn’t have that grit blasting distally you wouldn’t have to worry about that osteolysis because you’d have bone up there. But because you put that grit blasting distally it got fixed distally and the proximal bone has melted away.”
Dr. Whiteside: “Fixation distally does not cause proximal osteolysis; other issues do. If you have a fixed stem it’s likely to stay fixed if it’s fixed proximally and distally. Flexibility of that stem gives you bone preservation proximally.”
Moderator Thornhill: “Adolph, occasionally with an uncemented implant—and certainly with a cemented implant or a modular implant—you can change version. What do you do in those cases with your short stem?”
Dr. Lombardi: “If I have an issue with version, the flexibility of using a tapered stem that’s rectangular…you can maybe change 5/10 degrees. If you must do more than that then you have to go to a different design. I use the one Leo showed that has both proximal and distal fixation so that I can dial in the rotation I want.”
Moderator Thornhill: “Leo, what about impingement?”
Dr. Whiteside: “That’s important. You have to be careful and trim the edges of that proximal femur—especially anteriorly so that it doesn’t impinge in flexion. If you’re concerned about it you can put your finger on the front, flex the hip, and if it requires more trimming you can do that. But if you just flatten off that osteophyte it clears fine, especially with a 32mm head.”
Moderator Thornhill: “A question from the audience here. Adolph, did distal hypertrophy mean thigh pain in these patients?”
Dr. Lombardi: “No. It was more of a radiographic finding that was bothersome to some of us who were using this device. And so we do what was done in the standard line, and that is to come up with a reduced distal. We need a few more years under our belts with the reduced distal to tell you that we’re not going to have that distal hypertrophy. What I found by reducing distal is that we increased the size. I would broach with my standard stem broach and then broach with my reduced distal broach, and found that I was able to push up one or two sizes.”
Dr. Whiteside: “That distal hypertrophy is part of a shorter stem. The stresses are huge when you have a short stem; a longer stem mitigates those stresses to the point where you don’t see nearly as much distal hypertrophy.”
Dr. Lombardi: “I saw it with our longer porous plasma sprayed stems.”
Dr. Whiteside: “Of course…if they’re ingrown and big distally.”
Moderator Whiteside: “Thank you, gentlemen.”
Please visit www.CCJR.com to register for the 2014 CCJR Spring Meeting, May 18 – 21 in Las Vegas, Nevada.
