Moderator Trousdale: Craig, any role for cementing in the modular shiny cobalt chrome implant?
Dr. Della Valle: Yeah, if I want dual mobility and I have to cement something in, I use a cup. I’ll use a brand name because it’s what it is, it’s made for cement, it’s now owned by Smith & Nephew, it’s the Polar Cup. It’s a European product that’s made for cementation and you usually have to have about a 12 to13mm difference so if you have a 60mm shell you can usually get in a 49mm or 47mm Polar Monobloc dual mobility shell and you can cement that in there.
Moderator Trousdale: Yeah, we’ve had some success cementing the cobalt chrome dual mobility that’s made for primary, so it’s got a very rough HA surface on it and that interface is outrageously strong. Trying to take those out could be a chore so that could be a problem.
Dr. Sculco: Yeah, I think just to follow with the constrained sockets I think we’ve had failures trying to cement that liner into an existing shell and the reason is, it’s a fairly bulky liner and you tend, if you don’t have good cement margins and you try to just use a modicum of cement, they loosen and they fail. We’ve had failures with that so as you point out, Craig, I think you need a larger shell when you use that liner so you get good cement coverage, otherwise they potentially will fail.
Moderator Trousdale: So, maybe give the audience and me some clues here. How do you decide, Craig and Tom, between a dual mobility and a constrained liner? What are your criteria to say, “I’m going to do a dual mobility in this patient group or a constrained liner in this patient group?”
Dr. Della Valle: I would say the only scenario where I would favor constraint is that specific scenario where it’s a corrosion type issue because I’m worried about that extra modular junction just in terms of monitoring that patient post-operatively.
Moderator Trousdale: So, you’ll give dual mobility a shot and if it fails, you’ll go to next step of constraint.
Dr. Della Valle: Usually. There are several manufacturers that make shells that will take either a large head or a constrained or a modular dual mobility and I feel it just gives me the most options. Again, our experience, if you look at all comers, our risk of instability when we last looked was about 8% so that’s big.
Moderator Trousdale: Real deal, Tom.
Dr. Sculco: As I said earlier, if we are a straightforward revision, I think dual mobility works well. I think for the more complex revisions, poor soft tissue, older patients, you’re worried about instability, I still have more confidence you’re they’re going to be stable with a constrained socket.
Moderator Trousdale: Fair enough. Thank you, gentlemen, for a lively debate.
Please visit www.CCJR.com to register for the 2019 CCJR Spring Meeting, May 8-11 in Cleveland, Ohio.
