This week’s Orthopaedic Crossfire® debate was part of the 35th Annual Current Concepts in Joint Replacement® (CCJR®), Winter meeting, which took place in Orlando. This week’s topic is “Dual Mobility: First “Choice” for the High Risk Primary & Recurrent Dislocator.” For is Kevin L. Garvin, M.D., University of Nebraska Medical Center, Omaha, Nebraska. Opposing is Douglas E. Padgett, M.D., Hospital for Special Surgery, New York, New York. Moderating is Thomas S. Thornhill, M.D., Harvard Medical School, Boston, Massachusetts.
Dr. Garvin: I think we will all agree that hip instability is among the most common reasons for revision surgery and it’s still unacceptably high. We’ve known this for 35-36 years. Excellent study out of the Mayo Clinic by Ron Woo and Bernie Morrey (JBJS, 1982), looked at 10,000 hips. Over 300 dislocations; about 3% dislocation risk. One-third of those were re-operated. They were able to follow about 90 of those patients; 28 failed further surgery, or about 31%. Leading them to conclude, “Instability after total hip arthroplasty is a complex, multifactorial phenomenon.”
We have very little control over these very high-risk factors—prior hip surgery, alcoholism, cognitive impairment, neuromuscular disorders (Parkinson’s), female gender, avascular necrosis, obesity, hip dysplasia and infection as well as surgical factors: approach, component position, leg length, offset and abductors.
What are the effective choices for us at this time for those patients at high risk or recurrent hip dislocators? First, it’s large heads, constrained devices—and then I’m going to make the argument for non-constrained dual mobility.
In the primary setting, we have pretty good data that larger heads do decrease the risk of dislocation from about 4% to 2% (Goel, et al., JOA, 2014).
A prospective, randomized controlled trial from Howie, et al. (JBJS, 2012), looked at 28mm versus 36mm heads and showed a decrease in dislocation from 5% to just over 1%. I ask the question: Is 1% acceptable to us?
And in the revision situation, Garbuz, et al. with a multi-institutional study from seven different centers, looked at the difference in dislocation from large heads to 32mm or standard heads. And sure enough, the risk of dislocation was lessened considerably, down to 1.1% with the larger heads. (CORR, 2012).
But in that study, they excluded those who had revision for recurrent dislocation. They also excluded revision of the acetabulum, requiring a cage. Revision of the acetabulum with a cemented polyethylene liner and, finally, when they have the intraoperative dilemma of instability, they choose a constrained liner (Garbuz, et al., CORR, 2012).
But if you look cumulatively at several studies, up to 10 years, the risk of recurrent dislocation or revision of the components because of the stresses can be as high as 20-30% (Guyen, et al., JBJS, 2008).
