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No notching found with eccentric glenospheres for reverse shoulder arthroplasty
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A level 1 study comparing eccentric and concentric glenospheres during reverse shoulder arthroplasty for patients with cuff tear arthropathy showed similar clinical results between the groups, but found that eccentric components prevented scapular notching.
“We did not find a better clinical outcome with the eccentric glenosphere,” Peter Poon, MBChB, FRACS, said during his presentation at the 12th EFORT Congress 2011. “The striking difference was that with the eccentric glenosphere, it does prevent notching and we did not find any complications that were specific to the use of this newer design of glenosphere. Therefore, in our practice, we continue using them.”
For their randomized, controlled, double-blind prospective study, Poon and his colleagues studied the performance of 36-mm eccentric and concentric glenospheres.
“We chose to look at this smaller glenosphere and not the larger diameter glenosphere to avoid the situation where small shoulders in little old ladies may be simply too small to implant a large diameter glenosphere,” Poon said.
From 2007, two surgeons at a single center performed reverse shoulder arthroplasty using a similar surgical technique in 34 patients who received a concentric glenosphere and 31 patients who had an eccentric glenosphere. All of the patients were older than 70 years of age, received the Systema Multiplana Randelli (SMR) reverse shoulder prosthesis (Lima-LTO, Italy) and underwent a similar postoperative rehabilitation. The groups had an average follow-up of 1 year.
The groups were assessed using a subjective shoulder rating system, range of motion, radiographs, the American Shoulder Elbow Score (ASES), Oxford shoulder score, and Visual Analog Scale for pain. A research nurse blinded to the type of glenosphere used conducted the clinical assessments, and registrars or residents assessed the radiographs.
The team found no significant differences between the groups regarding any of the measurements.
“For each of the parameters we used to evaluate the clinical outcome, we could see that the preoperative and the postoperative scores, and the degree of improvement of these parameters were very similar and virtually identical comparing the two groups,” Poon said. “This is true for pain relief, subjective shoulder rating, ASES, Oxford shoulder score, active forward elevation and active external rotation.”
However, the investigators found a significant difference in the rate of scapular notching between the groups. In the eccentric glenosphere group, the team found no scapular notching. In the concentric group, three patients had scapular notching of 3 mm, 7 mm and 8 mm at 1-year follow-up. However, Poon noted that these patients had above average clinical results.
One patient in the concentric glenosphere group underwent revision to a thicker humeral insert for recurrent dislocation and experienced no further dislocations. Acromial stress fractures occurred at 2-year follow-up in one patient in each group. – by Renee Blisard
Reference:
- Poon P, Chou J. Prospective, double-blind, randomized, controlled clinical trial of the SM reverse shoulder prosthesis comparing the eccentric to concentric 36 mm glenosphere: Clinical outcome and scapular notching. Paper #350. Presented at the 12th EFORT Congress 2011. June 1-4. Copenhagen, Denmark.
- Peter Poon, MBChB, FRACS, can be reached at the NS Orthopaedics, Northern Clinic, 212 Wairau Rd, Glenfield 0627; 09 443 0047; email: petercpoon@xtra.co.nz.
- Disclosure: Poon is a paid consultant for Lima and receives research funding from Lima and Arthrex. Lima funds his research nurse.