Abstract: BACKGROUND: Elbow pressing method is the common manipulation of massage. The forces on the lumbar vertebra are different with different angle elbow pressing methods and improper manipulation may aggravate the disease. Currently, the relevant research needs to be further improved.  
OBJECTIVE: Using the method of finite element analysis, to observe the distribution of stress, the distribution and direction of displacement at L4-L5 vertebra and posterior structure of lumbar model with different angle elbow pressing methods, and to investigate the safest and most suitable angle of elbow pressing method so as to provide reference for clinical practice.
METHODS:  CT images of a 25-year-old healthy male volunteer were obtained. A normal lumbar finite element model was established using Mimics, Geomagic Studio, Solidworks, Hypermesh, and ABAQUS softwares. The elastic modulus and Poisson’s ratio of nucleus pulposus and annulus fibrosus were changed to establish the left and back protrusion of lumbar intervertebral disc. The pressing position was the projection of the protrusion’s body surface. The pressing force was 400 N, and the pressing was simulated once every 15° until 165° from left to right. The distribution of stress, the distribution and direction of displacement in the vertebral body and posterior structure of finite element models with normal and lumbar disc herniated lumbar spine were observed under the different angle elbow pressing methods. The implementation of the research protocol complied with the relevant ethical requirements of the First Affiliated Hospital of Hunan University of Chinese Medicine, and the subjects signed informed consent to the test process and use.  
RESULTS AND CONCLUSION: (1) Compared with the normal lumbar spine model, the range of stress concentration in the posterior structure of the lumbar disc herniation model was larger, such as articular joints, pedicles, and simulated compression parts. Many stress concentrations occurred, such as back and side of the lower part of the right lamina of L4 and the lower part of the L5 vertebral body. (2) When the angle of the elbow was 15°-45°, the stress of the lumbar disc herniation model was mainly concentrated on the right side. (3) When the pressing angle was 30°-60°, the largest displacement distribution was the L4 bilateral superior articular process. Moreover, the vertebral body and its rear structure would shift forward and right. (4) Compared with different angle elbow pressing methods, when the angle of the elbow was 30°-45°, the load on the affected vertebral body was smaller, and the safety was higher. The position of the L4-L5 lumbar facet joints can be adjusted to restore the normal biology of the spine mechanical status. This conclusion is recommended for clinical reference.

Key words: finite element method, lumbar vertebra, lumbar disc herniation, elbow pressing method, massage