ABSTRACT
BACKGROUND:Ligaments are important structures in maintaining the stability of the lumbar spine,and these structures are prone to degradation due to the generated mechanical stress.However,there are few studies on ligament injuries. OBJECTIVE:To determine the range of motion and stress of each ligament in the state of motion based on a three-dimensional finite element model,and to systematically explore the influence of ligament injury on the stability of the lumbar spine and its biomechanical significance. METHODS:The L4-L5 lumbar finite element model was established.All free forces on the lower surface of L5 were constrained,and a torque of 5 N·m was applied to simulate the motion states of the lumbar spine.Progressive ligament damage was simulated by changing Young's modulus of the ligament. RESULTS AND CONCLUSION:(1)The extension range of motion of most ligament injuries increased significantly.In contrast,there was no significant change in the lateral bending range of motion.(2)The range of motion of capsular ligament injury increased significantly in flexion,extension and lateral bending.The extension range of motion increased significantly after the anterior longitudinal ligament injury.Intertransverse ligament injury resulted in a significant increase in the lateral bending range of motion.(3)After a single ligament injury,the most significant change in range of motion was observed during extension.After a single ligament injury,the stress of the remaining ligaments increased,especially the capsular ligament.The stress changes of the interspinous ligament and ligamentum flavum were the least obvious.Ligament stress changes least in lateral bending and most in torsion.(4)Ligament damage did not result in major changes in disc pressure,indicating that ligament injury leads to an increased range of motion of the lumbar spine and affects the stability of the lumbar spine.(5)Capsular ligament was stable in flexion,extension and lateral bending.The anterior longitudinal ligament showed a stable extension;the intertransverse ligament stabilizes the lateral curve.(6)Extension exercise is sensitive to a ligament injury,and the pathological changes of the ligament can be examined by extension exercise.(7)Stress compensation was given to the remaining ligaments to maintain the stability of the lumbar spine after a single ligament injury.(8)Interspinous ligament and ligamentum flavum injuries have the least impact on the peripheral ligaments,while capsular ligament injuries have the greatest impact on the peripheral ligaments.(9)The ligament injury has the least effect on the residual ligament stress during lateral bending exercise,while it has the greatest effect on the ligament stress during the twisting exercise.Patients with ligament injury should avoid twisting exercises.Ligament injuries do not affect disc pressure.
ABSTRACT
Objective Comprehensively considering the effectiveness and safety of massage, a method for evaluating the pros and cons of oscillation excitation and pulse excitation for lumbar oblique-pulling manipulation was proposed, and lumbar oblique-pulling manipulation under oscillation excitation was optimized. Methods A multi-rigid body biomechanical model of thoracolumbar spine was established. The manipulation force was used as the input force of the model. Using MATLAB/Simulink, variation of the displacement and acceleration of each lumbar segment with time was simulated. For the optimization of lumbar massage manipulation, the core elements of massage force, namely, frequency (f) and operand (n) were changed, and then the maximum relative displacement and maximum acceleration of each lumbar segment were compared. A new index z was proposed to comprehensively evaluate effectiveness and safety of the manipulation. Results The maximum relative displacement of each lumbar segment was almost equal when lumbar oblique-pulling manipulation under two kinds of excitation was applied. For lumbar oblique-pulling manipulation, the maximum acceleration of each lumbar segment under oscillation excitation was significantly smaller than that under pulse excitation. When the frequency of massage was 1-2.5 Hz, the overall effect of massage was better, and the overall effect had no relation with the operands, and the force of massage lasted for one operand; when the frequency of message was 3.33 Hz and the operands were more than 5, the massage had the best effect, meanwhile the strength of each lumbar segment was relatively large; when the frequency of massage exceeded 5 Hz, and the overall performance of massage was not good. Conclusions Lumbar oblique-pulling manipulation under oscillation excitation is safer than that under pulse excitation. The research findings provide doctors with a reasonable range of operating parameters for lumbar oblique-pulling manipulation under pulse excitation.
ABSTRACT
Breast cancer is the most common spontaneous malignancy in women, causing a serious threat to women's health. Experimental animal models have been important research tools in bringing insights into the related mechanisms of breast cancer, as well as in delivering improved therapies for the disease. To reveal the pathogenesis of various breast cancers and facilitate the development of new drugs,ideal animal models of breast cancer should share some common tumor molecular characteristics and biological behavior with that of human breast cancer. In this review,five types of experimental animal breast cancer models were included, which may provide a basis for research on diagnosis and treatment of human breast cancer.