This week’s Orthopaedic Crossfire® debate was part of the 34th Annual Current Concepts in Joint Replacement® (CCJR®), Winter meeting, which took place in Orlando. This week’s topic is “Della Valle v. Sculco: Dual Mobility Cups: The Emergent Solution for Recurrent Dislocation.” For isCraig J. Della Valle, M.D., Rush University Medical Center, Chicago, Illinois.Opposing isThomas P. Sculco, M.D., Hospital for Special Surgery, New York, New York. Moderating is Robert T. Trousdale, M.D., Mayo Clinic, Rochester, Minnesota.
Dr. Della Valle: I think dislocation remains, no matter what surgical approach that you choose, one of the most common complications we see after total hip replacement and one of those most common we see after revisions. It’s morbid for patients, it’s expensive, and it’s something we certainly would like to treat better and ideally prevent.
The number one rule when it comes down to managing the patient with instability, like many things in revisions, is to understand the root cause. You really need to understand why the patient is dislocating to appropriately treat them.
The main benefit of dual mobility is to reduce the risk of dislocation. First released in France in the 1970s, it was introduced in the U.S. market in 2009.
There certainly have been design changes since 2009. Improved fixation is probably the biggest one. One design uses a monobloc metal cup with fins. It’s got a titanium sintered surface and today, most utilize crosslinked polyethylene. Some of the contemporary designs still use a stainless steel bearing, but many of them use a cobalt chrome alloy.
A major concern with dual mobility is intra-prosthetic dislocation, that’s basically the polyethylene disassociating from the small head. It’s generally secondary to wear at the introitus with that retentive rim, and I think most of the contemporary series have reported a reduced risk with better designs.
There are still concerns over greater wear because there are two articulations and again, with cobalt chromium counter bearings as well as crosslinked polyethylene, I think this is going to be less of a problem, but nonetheless something to certainly keep an eye on.
So, there are several studies out there that basically show that if you use a dual mobility bearing in revision total hip replacement, there is a low risk of dislocation. Rob Trousdale has shown that from his series at the Mayo Clinic and we’ve also shown it in one of our series at Rush. It also has a low risk of failure when used to treat instability specifically.
Indications for dual mobility. In the first dual mobility case I did, the manufacturer came to me, said that this design helped reduce the risk of dislocation. I had a case of modular, oncology, infected, proximal femoral replacement that we were revising. I figured, “Hey well if it works for instability, let’s try it in this case.” This case is now about 7 or 8 years old and it hasn’t dislocated. I use dual mobility in patients who are abductor deficient—again revisions for instability, but also for inadequate intraoperative instability or if you are unable to get a head size larger than 36mm at the time of revision surgery.
So, we’ve done 36 dual mobility bearings in high-risk patients and followed them for a minimum of two years. We had one dislocation that was closed reduced and it’s very important to understand, if one of these does dislocate, you need to reduce it under strict paralysis in the operating room with fluoroscopy because we’ve now seen several cases where someone did not do it in the operating room, did not do a paralysis and they caused an intra-prosthetic dislocation with a forceful attempt at a closed reduction.
The other thing I want to point out here, in addition to the two deep infections, we had two cases early on where we tried to take a modular dual mobility liner, scratch up the back like you would a polyethylene liner and then cement it into a shell. We did three of them and within 6 weeks two of those failed so, that is something that you really do want to avoid.
