A Computational Investigation Into Acromial Fractures After Reverse Total Shoulder Arthroplasty
These authors point out that acromial fractures are a debilitating complication following reverse total shoulder arthroplasty (RTSA). The purpose of their work was to (1) improve the current state of finite element (FE) bone stress estimates after RTSA and to investigate the effects of (2) plane of elevation, (3) hand loads, and (4) baseplate screw position on scapular spine stress.
Their FE method used was validated against an in-vitro strain gauge based experiment and found to be accurate in the prediction of stress increases and decreases after RTSA.
The coronal plane of elevation was found to increase scapular spine stress compared to more central planes of elevation. Hand load increased stress levels above the fatigue threshold of healthy cortical bone.
A divergent screw angle decreased bone stress and if the screw penetrated the scapular spine then leaving the screw in place decreased bone stress compared to withdrawal.
Comment: Reverse total shoulder arthroplasty dramatically changes the loads applied to the scapula and can lead to fatigue fractures of the scapular spine. Should a drill penetrate the spine of the scapula, this model suggests it is better to place a screw in the hole, rather than leaving it empty.
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