Currently submitted to: JMIR Research Protocols
Date Submitted: May 4, 2026
Open Peer Review Period: May 5, 2026 - Jun 30, 2026
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From Clinical Grading to Mechanical Vulnerability: A Radiologist-Integrated Parametric Finite Element Study of Progressive Cuff Deficiency and Acromial Overload in Reverse Shoulder Arthroplasty
ABSTRACT
Background:
Acromial stress fractures represent a clinically important complication in reverse shoulder arthroplasty (RSA) with reported incidences up to 11%. Although modern implants improve the current situation, the precise role that load transfer plays in acromial fracture risk in RSA is not completely understood. To date, there is no preoperative method for risk stratification using individualised patient-specific factors.
Objective:
We present a prospective, imaging-based, radiologist-assisted finite element framework to estimate acromial stress risk after RSA. This protocol outlines its implementation and a first feasibility analysis.
Methods:
Ten to fifteen consecutive patients scheduled for elective primary RSA will undergo standardised high-resolution CT and 1.5T/3T MRI. Rotator cuff integrity will be graded using the Goutallier classification; the ordinal scores will be aggregated into a patient-specific Cuff Deficiency Index (CDI) using a preliminary weighting scheme (supraspinatus 0.40, infraspinatus 0.30, subscapularis 0.20, teres minor 0.10) subject to validation on the pilot cohort. This index will serve as a direct scalar multiplier for deltoid loading parameters in the finite element model. Patient-specific geometries will be created from HU-mapped cortical bone (CT) and MRI-derived deltoid anatomy. Physiological and RSA loading scenarios will be simulated in FEBio v3.x under quasi-static conditions. Acromial von Mises stresses will be extracted in anatomically defined Levy zones. Morphometric and stress-based parameters will be correlated with six-month postoperative radiographs. This study is registered on ClinicalTrials.gov (NCT07545707).
Results:
Patient recruitment and finite element simulations have not yet commenced. Data collection is scheduled to begin in the second quarter of 2026. This protocol paper reports the planned workflow and analysis strategy only.
Conclusions:
By prospectively integrating radiological grading of rotator cuff integrity into a patient-specific finite element workflow, this study aims to explore whether preoperative imaging and biomechanical modelling can identify anatomical patterns associated with increased acromial stress in RSA. Clinical Trial: ClinicalTrials.gov NCT07545707
Citation
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