“We are really still experimenting with surface replacement, ” says John Cuckler, “It should be limited to centers with sufficient volume.” “Contrary to what John showed you, there is actually higher survivorship [with surface replacement] than total hip in the at-risk patients, ” argues Tom Schmalzried. “We reported this in 2004…we hid it in the Journal of Bone and Joint Surgery (JBJS) so John must not have been able to find it.”
This week’s Orthopaedic Crossfire® debate is, “The Optimal Metal-Metal Arthroplasty is Not a Surface Replacement.” For the proposition was John M. Cuckler, M.D. from the Alabama Spine and Joint Center. Against the proposition was Thomas P. Schmalzried, M.D. of the Joint Replacement Institute in Los Angeles; moderating was Cecil H. Rorabeck, M.D., F.R.C.S.(C) of the University of Western Ontario.
Dr. Cuckler: “I like resurfacing. However, I’m doing them in a setting with a 56-year-old male who had a malunion of a subtrochanteric fracture with a question of infection. I didn’t think I could get any type of conventional stemmed implant into him…he is now four years out and continues to function well. The problem is that we don’t have enough long-term data.”
“The pros of resurfacing: they conserve femoral bone stock; cons are larger: issues of femoral fracture, increased acetabular bone stock removal, anatomic limits to the indication of this type of device, the biomechanics may be inferior, and the results—early on—and the learning curve consequences are significant.”
“Short term results: This data is somewhat aged now (from 1996, 1999), but the revision rate early on (12%, 71%, and some 0%) indicates that there is something going on that is improving and may become as good as the conventional total hip. If you look at newer reports [2004, 2005], the survivorship at two year follow-up is good, but not as good as conventional hip replacement.”
“If you look at Amstutz’s experience—and he has devoted his life to this concept…his survivorship at 2-6 year follow-up is 97% for the group as a whole. Good—but not as good as modern cementless conventional total hip arthroplasty.”
“The Australian Joint Registry: they found that the surface replacement arthroplasty revision rate compared with conventional total hips—short to intermediate term results are not nearly as good as with conventional total hip arthroplasty. In experienced hands, the results are approaching as good, but the learning curve is steep, as shown by Michael Mont’s experience. He had a 26% failure rate in his first 50 and 1% in his next 150.”
“Paul Beaulé and Amstutz’s selection criteria…their ‘Surface Arthroplasty Risk Index.’ (previous surgery=1; weight=2 if <82kg/180lbs; femoral cyst>1cm=2; activity level=1) This is going to knock out the majority of my young patients. If you have a score greater than 3 your risk of failure goes up 12 times.”
“Age is a relative contraindication to this device if you’re over 65. Under age 55 you can do reasonably well in the hands of an experienced surgeon…but after that it’s debatable. And women do not do as well with this device; older women do even worse than older men.”
“So the limitations to surface replacement include: leg length discrepancy>1cm, osteoporosis, heavy weight or light weight, female, acetabular dysplasia, varus and maybe valgus necks, femoral head cysts, large infarcts, you can’t restore offset well with these devices…and high activity level may be a relative contraindication.”
“We probably remove more acetabular bone stock with these devices…that may come back to haunt us. Ion release I don’t think is a factor. But there are unanswered questions: we need better intermediate and long term results; we need to know how the revision, especially on the socket side, is turning out…the acetabulum is the real question.”
“For now we should limit this to centers with sufficient volume and experience to teach us all what this device will really do. Thank you.”
Dr. Schmalzried: “These are not directly competing technologies. There are narrower indications for resurfacing, and you will see amazing outcomes and patients. Contrary to what John showed you, there is actually higher survivorship than total hip in the at-risk patients for which resurfacing is indicated.”
“We reported this in 2004…but we hid it in the JBJS so John must not have been able to find it. There’s no difference in the socket size that I use for surface replacement versus total hip in equivalent sized patients.”
“The selection criteria include the shape of the proximal femur. For example, a patient had bad mechanics in his right hip—a big slip. He is very short and quite varus, so I’m going to do a nice total on him and fix up his offset and limb length. His other hip had nice mechanics, so I’ll do a resurfacing on that side. No difference in the socket parameters or position.”
“Indications: those patients with an increased risk for failure of a total hip, that have a good proximal femur, or some femoral deformity or device that would complicate putting in a total hip. My poster child is a patient with bilateral surface replacements, and is active duty Navy Seal. In his free time he barefoot water-skis backwards.”
“Very important: Dr. Amstutz’s series really taught us who’s it best in and who should we avoid. Who’s at higher risk for failure? Females, smaller component sizes, those with large femoral defects, smaller patients, and relative varus position. Best results? Big osteoarthritic males because there’s dense bone, large fixation area. Also, the series showed that there was durable acetabular component fixation, just like we see with cementless acetabular components in total hips.”
“Patients are living longer and harder. They are unaccepting of disability, and want no restrictions. They don’t want a stem; they’re worried about the limitations of a total hip (no running/hard skiing/singles tennis). And large males can break a stem.”
“Three DEXA studies show that resurfacing maintains bone. You’ll never see proximal bone maintenance—Gruen zones 1 and 7—with a total hip. You just can’t do it with inside out…I don’t care how short the stem is. You only get it with outside-in physiologic loading.”
“These are the fill in the blanks for John. If you look at all comers—all total hips versus all resurfacings in Australia—he’s right. But that’s a patient selection issue. If you look at the at-risk demographic, males more than females, age under 65 and larger sized components…those patients actually have a better six year survivorship (that’s the length of time the Aussie registry’s been around) than the equivalent demographic with a total hip.”
“Conversion to total hip: one of our fellows looked at that, mostly for femoral side failure. The outcomes are similar to those of a primary total hip; the operative variables in terms of blood loss and operating time are similar to a total hip, and there have been no revisions in that group…no re-revisions out to 46 months.”
“Why resurfacing? The indications have been refined, and it’s not a directly competing technology with total hip. We do see higher activity, and I don’t place any restrictions on these patients…and it doesn’t in any way appear to be associated with early failure. Most importantly, there is higher survivorship in the at-risk demographic when compared to the same demographic with total hips. Thank you.”
Moderator Rorabeck: “John, one of the issues that patients who have had a resurfacing will tell you is that their hip ‘feels normal.’ The biomechanics are not normal. Why is that?”
Dr. Cuckler: “I think that happens because of what David Blaha said earlier…we hit that ‘sweet spot’ in terms of restoring the biomechanics and function of the musculature of the hip. I think you can achieve that with either of these implants. What we agree on is that it takes careful patient selection, preoperative planning…and if you’re not doing a fair number of these regularly you’re probably not going to get the kind of results that Tom gets. You may need to send it to someone else.”
Moderator Rorabeck: “Women don’t do as well…is it about head size or osteopenia, or what?”
Dr. Cuckler: “We don’t know. The ones I’ve revised have been revised for femoral neck fracture, which related to a technical error on the part of the surgeon. (We’ve met the enemy and he is us.) If you notch that femoral neck at the time of surgery you should probably go ahead and convert to a conventional total then and there.”
Dr. Schmalzried: “The Aussie registry—this year’s registry—is helpful. In big registries you have surrogates, such as gender, age, and component size. What they find is that the survivorship is better in males, in younger patients, and in larger components. If you take all those together the surrogate is cross sectional bone mass across the femoral neck. Resurfacing failures are all front loaded…they tend to occur in the first year and are mostly due to fracture. So those that don’t have much cross sectional bone mass are the ones at higher risk for short-term failure.”
Moderator Rorabeck: “So, John, should we being doing DEXA scans on resurfacing patients?”
Dr. Cuckler: “Clearly, osteopenia disposes to failure, but I think in the hands of an expert you can probably still get a good result. Patient selection is key, and you need to discipline yourself…at the end of the day I find very few that are truly appropriate.
Moderator Rorabeck: “You used the word ‘expert’ too, John. Is this an operation that somebody who’s doing five hips a year should think about taking up?”
Dr. Cuckler: “Probably not. But if you’re doing 30 or more I think you can begin…there is a different skill set than conventional hip arthroplasty.”
Moderator Rorabeck: “If I were a 50 year old again and needed a hip replacement—and I’m obviously a male (or I think I am)—I would think seriously about having a resurfacing arthroplasty. John, where is ‘the place’ for this surgery?”
Dr. Cuckler: “We will ultimately be using this procedure in cases with proximal femoral deformity, and in young active males…and it will be done in a select number of centers where people can do enough to have the skills to do it consistently well.”
Moderator Rorabeck: “Thank you both.”
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