“Larger femoral heads have decreased the need for constrained liners, ” argues Craig Della Valle.” “And constrained liners don’t always work.” “Hold on, ” says Larry Dorr. “I’ve used constrained liners for 20 years and I haven’t had the failure rates that have been reported.”
This week’s Orthopaedic Crossfire® debate is “The Use of Constrained Liners in Revision THA: More Problems Than They Solve.” For the proposition is Craig J. Della Valle, M.D. of Rush University Medical Center. He; against the proposition is Lawrence D. Dorr, M.D. of Keck Medical Center of USC. Moderating is William J. Maloney III, M.D. from Stanford Hospital and Clinics.
Dr. Della Valle: “Dislocation is the number one reason for total hip arthroplasty (THA). It’s also probably the most common complication after THA. Large femoral heads have changed the usage of constrained liners, and this has been facilitated by highly cross-linked polyethylene (HCLP). Because HCLP has facilitated the use of larger heads there doesn’t seem to be a meaningful increase in wear when you use a larger head. Such heads have been shown in two Level I studies to decrease the risk of dislocation in both primary and revision THA.”
“Michael Ries looked at his dislocation rate after his revision THA procedures. He found that large heads—if the abductors were intact—really decreased the risk of dislocation. When the abductors were deficient even large heads didn’t prevent that complication. These liners can be engaged into a compatible shell and they can be cemented into a well fixed shell. About 10 years ago John Callaghan showed that when cementing these into a shell he had over a 90% success rate.”
“But not all constrained liners are created equal. Furthermore, many of these studies that have examined the use of constrained liners are now 10 years old. A lot of the situations in the past where we used constrained liners I think we would now use a large head—such as abductor deficiency. Maybe the results aren’t quite as good in contemporary practice.”
“I did a complex allograft revision—a structural revision—that I was proud of until the patient came in six weeks postop and was abductor deficient. I had read the article and knew that I needed to use a constrained liner, but unfortunately it pulled the cup out of the pelvis.”
“There are additional negatives of constrained liners. Almost all of them decrease range of motion [ROM], which leads to impingement and then higher stresses on the polyethylene. Oftentimes they require thin polyethylene and depending on the design, sometimes it’s not cross-linked. There’s also an increased risk of late loosening. Also, if a constrained liner fails, in the vast majority of cases another operation will be necessary. The number one rule with constrained liners is that these liners will not compensate for component malposition.”
“Is there an alternative? There is a lot of European literature showing that dual mobility articulations both decrease the risk of instability and can be used for recurrent instability. Although these bearing couples also have their own problems, including intraprosthetic dislocation, wear, and higher torques.”
“They do, however, solve some pretty difficult problems. If you do use these they can be on their own or cemented into a well fixed shell. I did have some problems, however. I took a dual mobility liner and scratched up the back as I would with a polyethylene liner; I cemented it into place and it quickly flipped out of the acetabulum. So now I use a dual mobility cup that’s meant for cementing into the acetabulum…now we don’t have any problems.”
“In a recent study we compared dual mobility articulations to constrained liners for pretty similar indications; the dual mobility articulations performed better. The risk of recurrent dislocation was lower. More importantly, the risk of repeat revision was lower in the dual mobility group. So at this point dual mobility is our go-to in lieu of a constrained liner.”
Dr. Dorr: “I’ve used constrained liners for 20 years and I haven’t had the failure rates that you’ve heard reported. I think the major cause of failure with these liners is poor surgical judgment…trying to use the constrained liner to make up for a bad situation. If you want success it’s really simple: you must ensure that you press fit the liner against the metal edge of the cup. You don’t want a liner that falls into the cup and you don’t want a liner proud [when the outer lip of the liner is not flush with the rim of the shell] of the cup. Also, you have to scratch both the polyethylene and metal liner. And you must ensure that the cup is in a good position.”
“I prefer a liner without a hood because it can increase the risk of impingement; and with impingement you have some risk for dislocation with a constrained liner. Also, the cement should never be more than 2mm.”
“I have a few technical tips. Use a power drill to scratch the implants. Use the cement more liquid than the normal doughy cement used with an acetabular component because then it’s too stiff and you can’t get the liner down against the metal shell. If you have rotational pegs on the shell you need to remove them; the liner has to be flush against the shell. And you must pressurize the liner until the cement is hard. I want a tight fit in there. John Callaghan and I showed (both in the lab and in a clinical study) that this technique is very reproducible and successful.”
“Here’s a tip about getting the head to seat fully into the polyethylene: dry the polyethylene and the femoral head. If you don’t you can’t get a lock in there. I think some failures occur because the head isn’t totally locked in. With the one I use today you can’t get the ring in unless it’s locked.”
“The dual mobility cups are like a boxer who’s flexible and makes you want to be like him. A fancy dual mobility boxer shows his moves and the old guy with the constrained liner is just standing around in the background…and it just takes one punch.”
Moderator Maloney: “Craig, one minute.”
Dr. Della Valle: “The decision making is always difficult, and because dislocation is such a common complication in hip replacement, I think surgical judgment is really important. In some of the cases Dr. Dorr mentioned I may have just used a large head. And while large heads also have their negatives, in general they seem to do a good job in terms of decreasing instability where in the past we may have used a constrained liner.”
Dr. Dorr: “It’s difficult to use a large head in a cup that’s 49mm.”
Dr. Della Valle: “Agreed.”
Dr. Dorr: “If you have a poor abductor and you can’t use a big head then you have to choose between dual mobility and a constrained liner to bail yourself out.”
Moderator Maloney: “Larry, if a socket is retroverted 10 degrees are you going to put a constrained liner in?”
Dr. Dorr: “No. You just have to have the same criteria for cup position using a constrained liner that you would have for a cup position being correct for a regular liner. You’re using a constrained liner in a limited situation and in a bad situation where there is failure of biological constraint for the hip. There’s only two ways we can get constraint in a hip. In a hip you get biological constraint by the muscles in the capsule…and if you don’t have it you must have mechanical constraint. That’s when we use some of these mechanically constrained liners. So the decision for using it is based on the absence of biological constraint or the ability to get biological constraint. You still must have component position.”
Moderator Maloney: “I’ve seen people assess lateral opening but not anteversion, and I think it’s critical to make sure you have reasonable anteversion when you put a constrained liner in…or else it’s going to pull out.”
Dr. Dorr: “That’s one of the big problems we have with regular cups too because we see a lot of these talks on how they use imaging intraoperatively, but a lot of it only gives them inclination, not anteversion.”
Moderator Maloney: “Craig, any situations today where you would use a constrained liner?”
Dr. Della Valle: “In a small female …a 48mm cup where you’re abductor deficient and to get in a dual mobility articulation is going to be difficult.”
Moderator Maloney: “Larry, one of the most common situations we see is a big revision with poor bone quality, etc., and you’d really like to put a constrained liner in, but you’re worried about the liner pulling the whole acetabular reconstruction out.”
Dr. Dorr: “That’s when you’ve got poor biological constraint and you need mechanical constraint, but you’ve got poor bone and you can’t get good component fixation. I’d put a cast on for at least two months. Sometimes we have to use fracture principles. If the bone is no good you can’t just hope that it’s going to act like a primary hip replacement.”
Moderator Maloney: “Craig, it seems like you’re transitioning to this dual mobility concept. Where are you using it?”
Dr. Della Valle: “The biggest ones are abductor deficiencies and complex revisions where you’re concerned about fixation of your acetabular revision. And while I think the dual mobility does impart more torque than a large head, it’s less than a constrained liner. In these situations where I would have cemented in a constrained liner we’ve gone to cementing in a dual mobility liner. It’s also helpful with the older systems where all you can get is a 28 or 32mm head…and for a dual mobility bearing you need a 28.”
Moderator Maloney: “Is there any primary situation where you’d use a dual mobility socket and/or a constrained liner today?”
Dr. Della Valle: “I do some dual mobility for primaries, but in general those are acute femoral neck fractures for a THR. Also, alcoholic or drug dependent patients, patients with cerebral palsy or Parkinsons’s disease.”
Moderator Maloney: “Larry, your thoughts on dual mobility?”
Dr. Dorr: “I haven’t used it, but I know that there are people having success in a revision situation…so it’s probably a good device.
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