Good results seen with algorithmic approach for treating hip instability

Issue: April 2014

ORLANDO, Fla. — Researchers found nearly an 85% success rate using a six-part algorithm to determine treatment for patients with recurrent dislocation following total hip arthroplasty.

Based on their findings, Wayne G. Paprosky, MD, and colleagues at Rush found the highest incidence of redislocation in patients with abductor deficiencies (type III instability). Moreover, they discovered five of 11 type III hips treated with constrained liners failed.

Wayne G.
Paprosky

“We are now advocating the use of tripolar constrained liners where possible, especially in these type III abductor deficiencies,” Paprosky said during his presentation at the Current Concepts in Joint Replacement Winter Meeting, here. “When you are converting an acetabulum, which is a type IIIB, you will reduce the incidence of loosening. I can only re-emphasize that constrained liners should be used with caution, and these patients have somewhat of a poor prognosis with poor abductor function. In those cases where you do not know the etiology, you may have to counsel them and tell them there is a potential for recurrence.”

He added, “There is a good prognosis with isolated acetabular revision when you make sure that all malpositioned cups are appropriately aligned.”

For their study, Paprosky and colleagues performed a retrospective analysis of 75 consecutive hip arthroplasties that were revised due to instability. They classified the cases into the following six categories based on the etiology of the instability:

malposition of the acetabular component (type I);
malposition of the femoral component (type II);
abductor insufficiency (type III);
soft-tissue bony impingement due to a suboptimal head-neck ratio (type IV);
ate polyethylene wear (V); and
unclear etiology for cases with an intact abductor trochanteric complex and no component malpositioning or wear (type VI).

“We found that 40 of these cases were repeat revisions for instability. The two most common causes were for component malposition and abductor insufficiency,” Paprosky said.

Surgeons treated type I and II instabilities with component exchange; type III cases were treated with a constrained liner; type IV instabilities were treated by upsizing the femoral head and removing the sources of impingement; and type V cases were treated with a liner exchange.

The overall success rate for all treatments of instability was 84.4%. When treatment for type III abductor insufficiencies was removed, the success rate was 92%.

“Simply throwing in a constrained liner for abductor deficiency once the acetabular component is correctly positioned, either snap-fitting this in the proper shell or constraining it using a cemented liner, is not all it is cracked up to be,” Paprosky said. “Our proposal, if possible, is to go with the larger head. Often a good solution is to go with a 28-mm head and put a bipolar in place. This enables you to upsize if you converted a type IIIB acetabulum to a larger shell.” – by Gina Brockenbrough, MA, and Jeff Craven

Reference:

Paprosky WG. Paper #41. Presented at: Current Concepts in Joint Replacement Winter Meeting; Dec. 12-14, 2013; Orlando, Fla.

For more information:

Wayne G. Paprosky, MD, can be reached at 25 N. Winfield Rd., Suite 505, Winfield, IL 60190.
Disclosure: Paprosky owns stock in Avenir Medical, is on the speaker’s bureau for DePuy Synthes, Medtronic and Zimmer, and is a paid consultant for Stryker and Zimmer.