This multicenter retrospective study asked which patient factors and implant-positioning parameters drive acromial and scapular spine stress fractures after reverse shoulder arthroplasty. It pooled 6,320 RSA patients from 24 surgeons at 15 U.S. institutions, using the Delphi method to define variables. Radiographic measures of final implant position (LSA, DSA, LHO) were compared in propensity-matched fracture and control groups.
When you plan a reverse shoulder arthroplasty, the patient in front of you matters more than the implant you pick. Osteoporosis, inflammatory arthritis, older age, female sex, and rotator cuff deficiency each roughly double the odds of an acromial or scapular spine stress fracture. Identify, optimize, and counsel these patients before surgery, then watch them closely afterward.
The implant lesson is a deltoid moment arm model. Humeral lateralization lengthens the moment arm and lowers abduction force, so it protects the acromion. Glenoid lateralization shifts the center of rotation laterally, shortens the moment arm, and raises deltoid force and strain.
Remember this is a retrospective association, and glenoid lateralization still buys real benefits (better external rotation, less notching), so it is a balance, not an absolute.
This multicenter retrospective study asked which patient factors and implant-positioning parameters drive acromial and scapular spine stress fractures after reverse shoulder arthroplasty. It pooled 6,320 RSA patients from 24 surgeons at 15 U.S. institutions, using the Delphi method to define variables. Radiographic measures of final implant position (LSA, DSA, LHO) were compared in propensity-matched fracture and control groups.
When you plan a reverse shoulder arthroplasty, the patient in front of you matters more than the implant you pick. Osteoporosis, inflammatory arthritis, older age, female sex, and rotator cuff deficiency each roughly double the odds of an acromial or scapular spine stress fracture. Identify, optimize, and counsel these patients before surgery, then watch them closely afterward.
The implant lesson is a deltoid moment arm model. Humeral lateralization lengthens the moment arm and lowers abduction force, so it protects the acromion. Glenoid lateralization shifts the center of rotation laterally, shortens the moment arm, and raises deltoid force and strain.
Remember this is a retrospective association, and glenoid lateralization still buys real benefits (better external rotation, less notching), so it is a balance, not an absolute.