Speaker recommends lowering glenosphere in reverse shoulder arthroplasty to avoid scapular notching

Surgeons should lower the glenosphere during reverse shoulder arthroplasty to prevent scapular notching, according to a presenter at the Current Concepts in Joint Replacement Spring Meeting.

“If you’re using a prosthesis that lowers the glenosphere, you have to get it lower. Otherwise, you’re not going to do any different than if you didn’t lower it,” Lynn A. Crosby, MD, from the Medical College of Georgia, said.

Although early reports of scapular notching appeared to show no effect clinically, Crosby cited a study by Simovitch and colleagues that showed scapular notching occurring quickly within the first 14 months before stabilizing at 18 months. Other studies followed that associated lower Constant scores, range of motion and higher pain scores with scapular notching.

Crosby noted that the Nerot-Sirveaux grading scale is used to analyze scapular notching in reverse shoulder arthroplasty (RSA). He said grade I and grade II notching is confined to the pillars and contact to the lower screw, respectively, while grade III is over the lower screw and grade IV is extending over the baseplate.

“I think you will agree if you have grade I and II notching it is probably secondary to impingement of the prosthesis, but if it gets to grade III and IV there is some other process going on, and we feel that is osteolysis from debridement on the polyethylene liner and then secondary macrophage infiltration, and to take up the debris and also bone,” Crosby said.

Rotating the glenosphere was initially thought to decrease scapular notching, but Crosby cited several studies that found no difference in notching between RSA patients with an inferior tilt and a normal tilt. For advanced glenoid scapular notching, Crosby said it takes a long time to become unstable after bone moves up to the glenoid post.

“It is a long process, and currently when I follow these patients, if they are asymptomatic, I tell them I have to keep following them closely to see if there is advancement. When I see shifting is the time I recommend we do something,” he said.

In cases of severe deficiency where revision is indicated, Crosby recommended bone grafting but said a good debridement is needed.

“If it is really medial, you can use an augmented prosthesis with a bone graft or a lateral extended glenosphere to bring it back out where you need to,” he said.

Reference:

Crosby LA. Paper #13. Presented at: Current Concepts in Joint Replacement Spring Meeting. May 19-22, 2013; Las Vegas.

Disclosure: Crosby receives royalties from Exactech.