These authors studied the effect of lateralization of the center of rotation in reverse shoulder arthroplasty (RSA) for cuff tear arthropathy (CTA). Thirty-four patients had RSA either with lateralization (n = 17) or without lateralization (n = 17) by use of a 1-cm autologous bone graft ("bony increased offset") of the humeral head for CTA.
At final follow-up, all patients showed significantly increased functional results and clinical outcomes. There were no significant differences in the evaluated parameters.
If patients with degenerative changes of the teres minor were excluded, the lateralized group showed significantly increased external rotation. Bony integration of the graft could be verified on postoperative computed tomography scans in all patients.
In 4 patients, CT scan evaluation showed acromial stress fractures (2 in STD group and 2 in BIO group).
RSA with bony lateralization shows a trend toward improved external rotation in lateralized RSA, with a statistically significant improvement in external rotation in patients with an intact teres minor.
Comment: Lateralization of the center of rotation can be accomplished with either the use of graft (as in this case) or with an offset glenosphere (as in technique we use).
As nice shown in this illustration by Steve Lippitt, in medializing the center of rotation the Grammont-style reverse total shoulder (middle figure) removes the tension and function of whatever rotators may remain intact. Lateralization of the center of rotation (bottom figure) helps restore tension and function if the external rotators are intact (as shown in this study).
As stated here and here we prefer glenoid components that have different amounts of built-in lateral offset so that the tension in the residual external rotators can be adjusted.
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