The rotator cuff, also known as the rotator sleeve, consists of the supraspinatus muscle, infraspinatus muscle, teres minor muscle attached to the greater tubercle, and subscapularis muscle attached to the lesser tubercle. It forms a sleeve structure at the anatomical neck of the humerus head. The rotator cuff is an essential stable structure of the shoulder joint. Rotator cuff tear will weaken or even lose the stability of the shoulder joint. It can cause chronic shoulder pain, the third most common symptom in the systemic musculoskeletal system after back and neck pain. According to the study of Minagawa et al, in a group of people with an average age of 69.5 years who underwent health examination, the incidence of rotator cuff tears reached 22.1%. The study of rotator cuff biomechanics is of great value for understanding the occurrence, development mechanism, and surgical treatment of rotator cuff injury. Because measurement techniques and ethical issues limit traditional biomechanical experiments, the stress distribution of rotator cuff under physiological and pathological conditions is almost impossible to obtain. In recent years, with the continuous development of computer technology, software development, and image processing, the rotator cuff’ finite element model is becoming increasingly mature, becoming an indispensable tool for biomechanical research of the rotator cuff.

To establish a complete three-dimensional finite element model of the shoulder joint and rotator cuff tissue and to conduct the related mechanical analysis.

A healthy adult shoulder joint's CT and MRI scan data were successfully imported into Mimics 21.0, 3-Matic 11.0, and Geomagic Studio 2012 software to complete the model construction. Then it was imported into the Hypermesh 2019 software to conduct pre-processing operations such as material assignment, mesh division, load application, and boundary conditions. Finally, it was imported into Abaqus 6.14 software to simulate the stress characteristics of rotator cuff tissues at shoulder abduction of 5°, 10°, 15°, 20°, 25°, and 30°.

The 3D finite element model of the rotator cuff has a complete structure and highly restores the tissue morphology of the rotator cuff. The mechanical analysis results show that the supraspinatus muscle has the largest force during shoulder abduction, which proves the model's validity.

The method is feasible, and the 3D finite element model of the rotator cuff is established completely, which can be used in the biomechanical research of rotator cuff.