David Murray says, “With revisions for pseudotumors we have poor scores with high complication rates because of soft tissue damage.” Edwin Su counters, “There may be no ‘easy out, ’ but I would rather convert a failed resurfacing because I think it’s an easier operation.”
This week’s Orthopaedic Crossfire® debate is “Surface Replacement Conversion: No Easy Out.” For the proposition is David W. Murray, M.D., F.R.C.S. of Nuffield Orthopaedic Centre in Oxford, UK; against the proposition is Edwin P. Su, M.D. from Hospital for Special Surgery in New York. Moderating is Daniel J. Berry, M.D. from Mayo Clinic in Minnesota.
Mr. Murray: “Resurfacing has many proposed advantages: very low wear, it allows high activity, a low dislocation rate, and it’s ideal for young, active men. That’s our experience in men under 50 with primary osteoarthritis…a 10 year survival of 99%. In women we’ve had poor results.”
“But the further proposed advantage of resurfacing is that revisions are simple, and that the outcomes of revisions are similar to primary total hip replacement. Early on that was our experience; the revisions were for fracture and were simple to treat and we had good results. But later on when we had pseudotumors we found the surgery was often difficult and the results were poor.”
“We had a situation where a solid lesion caused problems after revision. The patient presented with a late femoral nerve palsy. Our plastic surgeons took the lesion off the femoral nerve, but the nerve never recovered, and subsequently there was a femoral artery stenosis.”
“In 2009 we reviewed the outcomes of our revision resurfacings; there were 53 patients involved. About a third were revisions for pseudotumors, a third for fractures, and a third for infection/loosening. These were all matched with primary total hip replacements. The revisions for fracture or other causes had similar outcome scores to primary total hips…they did well. Whereas the outcomes for revisions for pseudotumors did poorly; the average outcome scores were only slightly better than the scores before hip replacement.”
“Fifty percent of our pseudotumors had complications, include subsequent dislocations, loosening, and nerve or vessel injury. Since then we’ve had more acetabular loosening; perhaps the metallic debris interferes with bone ingrowth. A third of the cases revised for pseudotumors had re-revisions, and at these we noted there was sometimes recurrence.”
“We were concerned about the late recurrences, and more recently (2012) we’ve looked at them in a retrospective case control study. We compared patients that have been revised for pseudotumor then have had re-revision for recurrence to those that did not have a recurrence. There were 37 cases revised for pseudotumor. We tend to be aggressive in our surgery, with a radical soft tissue debridement. There were nine recurrences; mean time to this second revision was 14 months. The findings at surgery: seven had substantial osteolysis or necrosis, two had complete abductor loss, one pelvic dissociation, one sciatic nerve involvement, and one femoral artery stenosis.”
“If we compare those pseudotumors that did recur with those that didn’t there were some interesting insights. Those that did recur had earlier initial revisions. The recurrence was not because we delayed the revision, but because the lesions were more aggressive. Lesions that recurred tended to be predominantly solid, suggesting that these are the more aggressive lesions.”
“So a recurrence rate of pseudotumors can be up to about 25%. We don’t know why they recur; it may be retained metal debris or hypersensitivity. It’s hard to prevent, as these recurrences happen despite extensive dissection.”
“Data from the Australian registry compares the revision rate of resurfacings converted to total hips with revision rate of primary total hips. The revision rate of resurfacings revised to hips is more than twice that in primary hips. About half of these are for simple revisions such as fracture.”
“On average, with revisions for pseudotumors we have poor scores with high complication rates because of soft tissue damage…and even with early revision of aggressive lesions you can have a poor outcome. There’s no easy out if you’ve got an aggressive pseudotumor.”
Dr. Su: “I fully agree that the goal of hip resurfacing will only be realized if it doesn’t burn bridges with respect to revision surgery or if it provides an easier solution at the time of revision—with equivalent results.”
“Harlan Amstutz’s group had one of the first papers looking at conversion of failed hip resurfacing; it showed excellent clinical outcomes, similar to that of a primary total hip replacement…with the caveat that most of these were done for femoral failures only. However, there has been an increasing incidence of reports, negative attention to the metal-metal bearing, with reports of pseudotumors, metal allergy, and tumor necrosis. The original report consisted of 20 hips, all women, with an estimate that 1% of patients would have a pseudotumor within five years. Later papers identified the female gender, dysplasia, and small component size as risk factors.”
“Technically, I think the operation is easy. You cut the femoral head off then you have excellent exposure to the acetabulum; you can use one of the new large ball adaptor explant type devices. Or you can use a trial liner, slipping it into the socket to use that as a fulcrum. In my experience it’s not that difficult to get these cups out.”
“I’ve performed 55 revisions of hip resurfacings to date with about an equal split between men and women. They’ve been done for a variety of reasons, including femoral neck fracture, metallosis, osteonecrosis of the femoral head, etc. Overall I’ve been happy with these revisions; the postoperative Harris Hip Score has been excellent at two years (a mean of 94). I have had two re-revisions for infection.”
“The types of revisions I’ve done were cup-only in 4 cases, femoral-only in 14 cases, and a full revision in 37 cases. The reasons were mostly mechanical (42%), some metallosis (24%), impingement (16%), and metal impingement (16%). Males have more mechanical reasons for failure; in my series the females have had more metallosis and unexplained pain with metal sensitivity.”
“Looking at revision type I didn’t see any difference in the clinical outcomes; however, by diagnosis, it was similar to what Professor Murray presented…that the reason for revision does play a role. The results in the unexplained pain and metal sensitivity group were substantially lower than those done for mechanical reasons. I did not see any cases of abductor destruction. Not surprisingly, we had poorer results with a less clear reason for failure; metal sensitivity did have the poorest results, usually in females. But the metal reactivity and the mechanical reasons for revisions still can have excellent results.”
“So it may be true that there’s no ‘easy out, ’ but I would rather convert a failed resurfacing because I think it’s an easier operation. Many people have vilified Professor Murray for bringing this to our attention, but he taught us that we need to be vigilant and monitor patients with metal-metal hip resurfacing. We have a low threshold to revise if there is component malposition, rising metal ion levels, or soft tissue abnormalities. The key point that may explain the difference in our outcomes is that we’ve been told to revise early with these metal-related problems.”
Moderator Berry: “So both of you say that if you do a conversion of a resurfacing arthroplasty that’s failed due to an advanced metal reaction with substantial local soft tissue reaction, that’s not a chip shot revision…it’s a tougher revision. Ed, it sounded like David generally agreed with your proposition that if you’re revising a resurfacing for mechanical problems then it’s not as tough of a revision. So when you’re doing a revision of resurfacing arthroplasty is there a role for retaining the cup?”
Dr. Su: “I think there is a role for femoral only revisions. To keep the cup you’re going to need something that mates with that cup, generally an anatomic size, large metal ball. So you would be revising it to a metal-metal hip replacement. There have been designs that have performed extremely well, and it’s a simple revision with a quick recovery. And these can work well in the long term.”
Moderator Berry: “Ed, even now when everyone’s concerned about large diameter total hip replacement with a metal-metal bearing you would still revise somebody to that and not take out a well fixed cup?”
Dr. Su: “Yes, but the caveat is that the cup must be well positioned and must be a good design.”
Moderator Berry: “What about doing a dual mobility head instead so you can put polyethylene instead of metal?”
Dr. Su: “That’s a great point. I think that’s a reasonable salvage option.”
Mr. Murray: “I’d strongly recommend not putting in a metal head on a hip replacement stem. At the beginning we did a lot of those for fractures and we thought it was great. But we had some nasty pseudotumors. If you want to preserve the socket then use the dual mobility; we’ve done that with good results. We’ve had problems with integration of sockets at revision. It’s relatively easy to cut them out, but we’ve had a few that loosened. That worries me because of the metal debris.”
Moderator Berry: “Do you think it’s because high cobalt chromium levels have caused some degree of necrosis of the bone that you can’t detect and implants don’t grow in?”
Mr. Murray: “I don’t know. I suspect it’s the environment with the ions. You can cut them out and you get a really nice surface…we were amazed that they loosened. The only thing that worries me about this dual mobility is that you get sharp edges on the resurfacing socket.”
Moderator Berry: “How much debridement is enough for the pseudotumor?”
Mr. Murray: “The recent study I shared with you showed that we don’t seem to have so many problems with the cystic ones, so we’re not so aggressive.”
Moderator Berry: “What do you do with the cystic ones?”
Mr. Murray: “We peel off the lining of the pseudotumor cyst and try to leave as much of the abductors as possible. Often you find it going up into the pelvis and we tend to pull it down.”
Moderator Berry: “Ed, comments?”
Dr. Su: “Yes, do a thorough debridement…and the solid ones seem to be more problematic. If there’s osteolysis within the bone I try to scrape all of that out and bone graft with it.”
Moderator Berry: “Abductor continuity is one of the keys to how these patients do, right? David, tricks on how to keep the abductors in shape?”
Mr. Murray: “Just be as careful as you can.”
Moderator Berry: “Thank you both.
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