Finite element study on whether posterior upper wall fracture is a risk factor for the failure of short-segment pedicle screw fixation in the treatment of L1 burst fracture.

PURPOSE: To establish the finite element model of T12 and L2 (T12-L2) pedicle screw fixation for severe L1 burst fracture, and quantitatively simulate and analyze the screw stress and vertebral displacement in different degrees of L1 posterior upper wall fracture (PUWF), and evaluate whether PUWF degree is a risk factor for fixation failure. METHODS: The data of 6 healthy volunteers were used to establish a finite element model of T12-L2 pedicle screw fixation for type A severe burst fractures. The stress and displacement of the conventional and Schanz pedicle screws for the different degrees of PUWF (including the anterior upper wall of the vertebral canal and the bipedicle) were evaluated. RESULTS: The maximum stress and L1 displacement of conventional and Schanz pedicle screws were positively correlated with the severity of the PUWF (P<0.05). During anterior flexion, the maximum stress of conventional pedicle screws for 70% type I were 538.3±59.75MPa and the maximum stress of Schanz pedicle screws for 90% type Ⅱ, 90% type Ⅲ and 70% type IV fractures were close to the fatigue threshold. The maximum stress during anterior flexion were significantly higher than those during posterior extension, bending and rotation (P<0.05). CONCLUSION: The posterior upper wall fracture of vertebral body (VB) of type A burst fracture is not an independent risk factor for the failure of short-segment pedicle screw fixation (SSPSF). Anterior flexion of type A fractures combined with severe PUWF of VB was a risk factor for the failure of SSPSF.

The feasibility of short-segment Schanz screw implanted in an oblique downward direction for the treatment of lumbar 1 burst fracture: a finite element analysis.

BACKGROUND: To evaluate the biomechanical properties of short-segment Schanz screw implanted in an oblique downward direction for the treatment of lumbar 1 burst fracture using a finite element analysis. METHODS: The Universal Spine System (USS) fixation model for adjacent upper and lower vertebrae (T12 and L2) of lumbar 1 vertebra burst fracture was established. During flexion/extension, lateral bending, and rotation, the screw stress and the displacement of bone defect area of the injured vertebrae were evaluated when the downward inserted angle between the long axis of the screws and superior endplate of the adjacent vertebrae was set to 0° (group A), 5° (group B), 10° (group C), and 15°(group D). There were 6 models in each group. RESULTS: There were no significant differences in the maximum screw stress among all the groups during flexion/extension, lateral bending, and rotation (P > 0.05). There were no significant differences in the maximum displacement of the bone defect area of the injured vertebrae among all the groups during flexion/extension, lateral bending, and rotation (P > 0.05). CONCLUSION: Short-segment Schanz screw implanted in an oblique downward direction with different angles (0°/parellel, 5°, 10°, and 15°) did not change the maximum stress of the screws, and there was a lower risk of screw breakage in all groups during flexion/extension, lateral bending, and rotation. In addition, the displacement of the injured vertebra defect area had no significant changes with the change of angles.

Effect of electroacupuncture on mice model of permenopausal depressive disorder.

OBJECTIVE: Study the effect of electroacupuncture on permenopausal depressive disorder (PDD) model through the peri-menopausal depression model mice. METHODS: KM female mice were selected. Except for the blank group (BG), the other groups of mice were removed by castration method. The mice of PDD was prepared by combining chronic unpredictable stimulation. Mice in the model group (MG) were not treated and fed normally. The western medicine group (WG) was given the corresponding drug for treatment. The electroacupuncture group (EAG) was given the electroacupuncture for treatment, and consecutive for 28 days. The levels of T, E2, FSH and LH in serum of mice were measured, and the brain tissue of 5-HT, DA and NE level were measured. Through the HE staining observed the morphological changes of mice hypothalamus. RESULTS: Compared with MG, EAG could increase the number of spontaneous activities of PDD model mice, the level of T, E2 in serum and the level of 5-HT, DA, NE in brain tissue was improved, and the level of FSH, LH in serum was reduced, and the hypothalamic lesions was improved. CONCLUSION: Electroacupuncture could improve the activity and memory of PDD mice, adjust the disorder of sex hormone, and increased the levels of monoamine transmitters (5-HT, NE, DA), and it could effectively improve the behavior and related biochemical indexes of PDD, and thus play an important therapeutic role.