This computer-simulation study models reverse shoulder arthroplasty to rank how five surgical and implant factors affect impingement-free abduction. It tests glenosphere position, tilt, size, center-of-rotation offset, and humeral neck-shaft angle across 243 combinations. The goal is a hierarchy surgeons can use to reduce inferior scapular notching.
Scapular notching plagues reverse shoulder arthroplasty, with reported rates from 56% to 96%, and it correlates with worse outcomes and even implant failure. This paper gives you a mental hierarchy for fighting it. To maximize abduction, prioritize a lateralized center of rotation and an inferior glenosphere position. Those two factors dwarf implant size.
To prevent the adduction deficit that causes notching, choose a varus (130°) neck-shaft angle and place the glenosphere low. A valgus 170° neck never cleared the scapula in this model.
The practical rule: if your system has a glenosphere centered at the glenoid, drop it inferiorly to regain motion and avoid notching. If you cannot place it low, lean on a more varus neck angle or a more lateral offset to achieve the same goal. Remember this is passive, single-plane simulation. It sets an upper bound on motion. Soft-tissue balance and muscle power still govern the active result.
This computer-simulation study models reverse shoulder arthroplasty to rank how five surgical and implant factors affect impingement-free abduction. It tests glenosphere position, tilt, size, center-of-rotation offset, and humeral neck-shaft angle across 243 combinations. The goal is a hierarchy surgeons can use to reduce inferior scapular notching.
Scapular notching plagues reverse shoulder arthroplasty, with reported rates from 56% to 96%, and it correlates with worse outcomes and even implant failure. This paper gives you a mental hierarchy for fighting it. To maximize abduction, prioritize a lateralized center of rotation and an inferior glenosphere position. Those two factors dwarf implant size.
To prevent the adduction deficit that causes notching, choose a varus (130°) neck-shaft angle and place the glenosphere low. A valgus 170° neck never cleared the scapula in this model.
The practical rule: if your system has a glenosphere centered at the glenoid, drop it inferiorly to regain motion and avoid notching. If you cannot place it low, lean on a more varus neck angle or a more lateral offset to achieve the same goal. Remember this is passive, single-plane simulation. It sets an upper bound on motion. Soft-tissue balance and muscle power still govern the active result.