This study links dynamic osseous impingement to radiographic scapular notching after Grammont-design reverse total shoulder arthroplasty. It combines patient-specific 3D CT, video motion analysis, and custom kinematic simulation in 29 patients. The goal was to identify which glenosphere positions predict and prevent notching.
When you plan a Grammont-style reverse shoulder, think of notching as a mechanical impingement problem you can design out of the case. The glenosphere should sit maximally inferior, with as much posterior and lateral positioning as the osseous anatomy allows. All three translational directions independently lower notching risk.
This paper reframes the mechanism: the dominant impingement event is external rotation with the arm at the side, hitting the posteroinferior neck. That is why version and inclination tweaks do not fix the problem, only translation does. Remember that posteroinferior notching is often invisible on plain films. Five of these cases were CT-only, so a normal radiograph does not rule notching out.
The practical takeaway: small changes matter. Roughly 3 to 6 mm of repositioning would have avoided most impingement, which is the argument for preoperative 3D templating in these implants.
This study links dynamic osseous impingement to radiographic scapular notching after Grammont-design reverse total shoulder arthroplasty. It combines patient-specific 3D CT, video motion analysis, and custom kinematic simulation in 29 patients. The goal was to identify which glenosphere positions predict and prevent notching.
When you plan a Grammont-style reverse shoulder, think of notching as a mechanical impingement problem you can design out of the case. The glenosphere should sit maximally inferior, with as much posterior and lateral positioning as the osseous anatomy allows. All three translational directions independently lower notching risk.
This paper reframes the mechanism: the dominant impingement event is external rotation with the arm at the side, hitting the posteroinferior neck. That is why version and inclination tweaks do not fix the problem, only translation does. Remember that posteroinferior notching is often invisible on plain films. Five of these cases were CT-only, so a normal radiograph does not rule notching out.
The practical takeaway: small changes matter. Roughly 3 to 6 mm of repositioning would have avoided most impingement, which is the argument for preoperative 3D templating in these implants.