Tuesday, February 9, 2016

Reverse total shoulder - does glenophere size matter?

Impact of glenosphere size on clinical outcomes after reverse total shoulder arthroplasty: an analysis of 297 shoulders

These authors reviewed 297 primary reverse total shoulders in 290 patients: a 38-mm-diameter glenosphere was used in 160 shoulders and a 42-mm-diameter glenosphere in 137 shoulders after a minimum 2-year follow-up

While the authors found that  improvements in active forward elevation and active external rotation were significantly greater in shoulders with a 42-mm glenosphere (+59° vs +44° for aFE and +24° vs +18° for aER) the results for the two glenosphere diameters actually were quite similar:

The overall rate of scapular notching was 9.8% (29 of 297), with no overall significant difference
between groups. Complications included 3 postoperative periprosthetic humeral fractures, 5 scapular spine stress fractures, 3 cases of residual pain and stiffness, 1 glenoid prosthesis loosening, 1 brachial plexus palsy, 1 superficial wound infection, and 1 complication due to the surgical scar.

Comment: Again we see the problem with retrospective studies: the paper does not explain why some patients received the 38 and others the 42. In that the demographics of the two groups were similar, there must have been some other important factor(s) that influenced the choice - surgeon experience? differences in pathoanatomy? soft tissue issues? 

As the diagrams above show, the geometrical differences between the two prosthesis options are no more than a few millimeters. It is likely that the variation in the anatomy of the patient would have a greater effect on the geometry of the reconstruction than the anatomy of the prosthesis. 

The cementless, bone preserving technique we use for a reverse total shoulder is shown in this link.