A Finite Element Analysis Of Mechanics About The Long Head Of Biceps Brachii Tendon

Shoulder joint is the most complex joint in kinematics of all the joints, which has the largest ROM, and the most components. In the narrow sense, the shoulder joint is composed of the scapular glenoid and the humeral head. Because of the poor bone tolerant of glenoid and humeral head, the role of soft tissue in maintaining shoulder stability and normal mechanical behavior of normal become important.Long head of biceps brachii start on the superaglenoid tubercle, which is divided into three sections: intra-articular, intrathecal and extra-articular section. During the extorsion of arm, the long head of biceps tendon (LHBT) across the superior of humeral head at almost a right angle which is a good suspension device of humeral head. When the arm abducts to 90°, the long head of biceps brachii assists deltoid and supraspinatus complete the abduction motion.All along, the role of the biceps tendon in shoulder pain has been debated. Historically, the biceps tendon has been considered to be a major source of shoulder pain, and its treatment has been considered to be a primary procedure. Over time, primary surgery on the biceps tendon has become less popular because of major interest in the rotator cuff. Currently, new interest is being focused on the long head of biceps because of the accumulation of research and clinical experience. Commonly used solutions are biceps tenotomy or biceps tenodesis. Biceps tenodesis is suggested in young, active patients that present with a degeneration of less than 50% of the biceps tendon fibers, medial subluxation of the biceps tendon, combined subscapularis tears and biceps subluxation or nonreparable SLAP lesions. The debate point of the two treatment therapy is that whether the LHBT tenotomy will affect the function of the shoulder?Bone biomechanics is considered to be the leading branch of biomechanics, the biomechanical experimental method represented by the three-dimensional finite element method is called theoretical biomechanical method which is more simplified and economical compared to experimental stress analysis. With the development of computer technology, the computer-assisted orthopedic shows more and more increasing potential and gradually become the research hotspot.Therefore, in this research we select a shoulder of 90°abduction position to study, based on the CT scan data, we set up the three-dimensional model of the shoulder, transforming the force of long head of biceps brachii into the load, and then performing finite element analysis:1. Set up a three-dimensional model of the shoulder(1). Obtain the sample dataUse CT scanner scan a shoulder joint to obtain the data at a resolution of 512pxl×512pxl, and then reconstructing the data to 0.5mm thickness, output in DICOM format. Compared with the previous method, CT scan can transform the image into data stored in a computer which can avoid loss of information, simplify the steps to reduce the accumulated error.(2). Set up the modelThe data was entered to the Mimics through the software interface, assisted with ABAQUS, we could quickly and accurately set up a shoulder model, including the humerus, scapula. After technically processed, the model would be more precise.This article assigned the material property of the model according to axial (S-I, Superior-Inferior). This was more precise compared with other domestic research, so that the model was closer to the actual situation.2. Finite element analysis using ABAQUSWe used two loading conditions to load the model, the first one was simulating the force of normal shoulder joint of 90°abduction position, the second one was simulating the force of post LHBT tenotomy.Finite element analysis results showed that after tenotomy of LHBT, stress of the distal attachment of supraspinatus on greater tuberosity did not increase, but decreased, indicating that to the rotator cuff, LHBT tenotomy did not increase its burden during shoulder abduction, which meant that LHBT tenotomy had no significant effect in rotator cuff degeneration.In this paper, we used CT scan data and Mimics to set up a accurately three-dimensional shoulder model. During the process, we resolved some problems of the model precision, and assigned more accurate material property to the model according to CT value and the appropriate empirical formula. There will be some reference value to future research.