TITLE:
Stresses in the Scapular Fossa Do Not Exceed the Yield Stress When Elevated up to 135 Degrees of Abduction after Reverse Shoulder Arthroplasty
AUTHORS:
Rina Sakai, Tomonori Kenmoku, Ryo Tazawa, Kazuhiro Yoshida, Tomomi Mizuhashi, Masanobu Ujihira
KEYWORDS:
Reverse Shoulder Arthroplasty, Finite Element Analysis, Yield Stress, Glenoid
JOURNAL NAME:
Journal of Biomedical Science and Engineering,
Vol.17 No.2,
February
7,
2024
ABSTRACT: Reverse shoulder arthroplasty (RSA) is an
effective treatment for rotator cuff tears. Despite its advantages,
complications occur at a high rate. Complications requiring revision include a
high rate of base plate failure, 38% of which are due to instability. The
primary stability the base plate ensures is a crucial factor and, thus, is the
subject of much debate in clinical studies and biomechanical research. This
study is aimed to provide data that will contribute to the base plate’s
pri-mary stability and glenoid longevity by clarifying the stresses at the
scapular fossa and base plate interface associated with elevation after RSA. A
3D finite element model was created from the DICOM data for the scapulohumeral
joint and SMR shoulder system. For loading conditions, 30 N was applied for
each posi-tion with abduction angles of 0, 45, 90, and 135 degrees. A
three-dimensional fi-nite element analysis was performed using the static
implicit method with LS-DYNA. The von Mises stresses in the scapular fossa were
found not to exceed the yield stress on the bone even after elevation to an
abduction angle of 135 de-grees after RSA. It is rough to uniformly compare the
yield stress and the von Mises stress, but it was inferred that the possibility
of fracture is low unless a large external force is applied. A maximum von
Mises stress showed 0 degrees of abduction, suggesting that the lowered
position is in a more severe condition than the elevated position. If better
improvement is desired, it may be necessary to devise ways to reduce the stress
on the upper screw.