Static study and numerical simulation of the influence of cement distribution in the upper and lower adjacent vertebrae on sandwich vertebrae in osteoporotic patients: Finite element analysis.

Objective: We analyzed the influence of the location of the upper and lower cement on the sandwich vertebrae (SV) by computer finite element analysis. Materials and Methods: A finite element model of the spinal segment of T11-L1 was constructed and 6 mL of cement was built into T11 and L1 simultaneously. According to the various distributions of bone cement at T11 and L1, the following four groups were formed: (i) Group B-B: bilateral bone cement reinforcement in both T11 and L1 vertebral bodies; (ii) Group L-B: left unilateral reinforcement in T11 and bilateral reinforcement in L1; (iii) Group L-R: unilateral cement reinforcement in both T11 and L1 (cross); (iv) Group L-L: unilateral cement reinforcement in both T11 and L1 (ipsilateral side). The maximum von Mises stress (VMS) and maximum displacement of the SV and intervertebral discs were compared and analyzed. Results: The maximum VMS of T12 was in the order of size: group B-B < L-B < L-R < L-L. Group B-B showed the lowest maximum VMS values for T12: 19.13, 18.86, 25.17, 25.01, 19.24, and 20.08 MPa in six directions of load flexion, extension, left and right lateral bending, and left and right rotation, respectively, while group L-L was the largest VMS in each group, with the maximum VMS in six directions of 21.55, 21.54, 30.17, 28.33, 19.88, and 25.27 MPa, respectively. Conclusion: Compared with the uneven distribution of bone cement in the upper and lower adjacent vertebrae (ULAV), the uniform distribution of bone cement in the ULAV reduced and uniformed the stress load on the SV and intervertebral disc. Theoretically, it can lead to the lowest incidence of sandwich vertebral fracture and the slowest rate of intervertebral disc degeneration.

Biomechanical study of a biplanar double support screw (BDSF) technique based on Pauwels angle in femoral neck fractures: finite element analysis.

Objective: The objective of the present study is to conduct a comparative analysis of the biomechanical advantages and disadvantages associated with a biplanar double support screw (BDSF) internal fixation device. Methods: Two distinct femoral neck fracture models, one with a 30° angle and the other with a 70° angle, were created using a verified and effective finite element model. Accordingly, a total of eight groups of finite element models were utilized, each implanted with different configurations of fixation devices, including distal screw 150° BDSF, distal screw 165° BDSF, 3 CLS arranged in an inverted triangle configuration, and 4 CLS arranged in a "α" configuration. Subsequently, the displacement and distribution of Von Mises stress (VMS) in the femur and internal fixation device were assessed in each fracture group under an axial load of 2100 N. Results: At Pauwels 30° Angle, the femur with a 150°-BDSF orientation exhibited a maximum displacement of 3.17 mm, while the femur with a 165°-BDSF orientation displayed a maximum displacement of 3.13 mm. When compared with the femoral neck fracture model characterized by a Pauwels Angle of 70°, the shear force observed in the 70° model was significantly higher than that in the 30° model. Conversely, the stability of the 30° model was significantly superior to that of the 70° model. Furthermore, in the 70° model, the BDSF group exhibited a maximum femur displacement that was lower than both the 3CCS (3.46 mm) and 4CCS (3.43 mm) thresholds. Conclusion: The biomechanical properties of the BDSF internal fixation device are superior to the other two hollow screw internal fixation devices. Correspondingly, superior biomechanical outcomes can be achieved through the implementation of distal screw insertion at an angle of 165°. Thus, the BDSF internal fixation technique can be considered as a viable closed reduction internal fixation technique for managing femoral neck fractures at varying Pauwels angles.

Comparison Between Intraoperative Target Area Cement-Enhanced Percutaneous Vertebroplasty and Conventional Percutaneous Vertebroplasty for Osteoporotic Thoracolumbar Non-Total Vertebral Fractures.

AIM: To compare the efficacy and feasibility of target area cement-enhanced percutaneous vertebroplasty (PVP) and conventional PVP in osteoporotic thoracolumbar non-total vertebral fractures. MATERIAL AND METHODS: Retrospective analysis of one hundred and two patients treated in our hospital from March 2020 to May 2021 and divided into groups A (targeted) and B (conventional PVP). The Visual Analogue Scale (VAS), Oswestry Disability Index (ODI), anterior vertebral height ratio, intraoperative bleeding, operative time, bone cement volume, complications, and refracture of the injured vertebra were evaluated in both groups. RESULTS: The 2 days and 1-year post-operative VAS and ODI scores improved significantly in both groups (p < 0.05). The 2 days post-operative VAS and ODI scores were better in group A (p < 0.05), and there was no significant difference in the scores between the groups at the last follow-up (p > 0.05). The anterior vertebral height ratios were significantly higher in both groups 2 days postoperatively (p < 0.05); however, there was no significant difference in the 2 days and 1-year post-operative ratios in group A (p > 0.05). The anterior vertebral height ratio reduced in group B after 1 year compared to the 2 days post-operative value (p < 0.05). There was no statistical difference in intraoperative bleeding and the operative time between the groups (p > 0.05), and the bone cement volume was lesser in group A (p < 0.05). Six patients in group A and four patients in group B demonstrated cement leakage, the difference was not statistically significant (p > 0.05). Three patients in group A and 11 patients in group B demonstrated refracture, the difference was statistically significant (p < 0.05). CONCLUSION: Target area cement-enhanced PVP can effectively relieve short-term pain and functional disability and reduce the long-term possibility of secondary collapse. Therefore, it is a technically feasible and efficacious method for the treatment of osteoporotic thoracolumbar non-total vertebral fractures.

Biomechanical study of different bone cement distribution on osteoporotic vertebral compression Fracture-A finite element analysis.

Purpose: This study aimed to compare the biomechanical effects of different bone cement distribution methods on osteoporotic vertebral compression fractures (OVCF). Patients and methods: Raw CT data from a healthy male volunteer was used to create a finite element model of the T12-L2 vertebra using finite element software. A compression fracture was simulated in the L1 vertebra, and two forms of bone cement dispersion (integration group, IG, and separation group, SG) were also simulated. Six types of loading (flexion, extension, left/right bending, and left/right rotation) were applied to the models, and the stress distribution in the vertebra and intervertebral discs was observed. Additionally, the maximum displacement of the L1 vertebra was evaluated. Results: Bone cement injection significantly reduced stress following L1 vertebral fractures. In the L1 vertebral body, the maximum stress of SG was lower than that of IG during flexion, left/right bending, and left/right rotation. In the T12 vertebral body, compared with IG, the maximum stress of SG decreased during flexion and right rotation. In the L2 vertebral body, the maximum stress of SG was the lowest under all loading conditions. In the T12-L1 intervertebral disc, compared with IG, the maximum stress of SG decreased during flexion, extension, and left/right bending and was basically the same during left/right rotation. However, in the L1-L2 intervertebral discs, the maximum stress of SG increased during left/right rotation compared with that of IG. Furthermore, the maximum displacement of SG was smaller than that of IG in the L1 vertebral bodies under all loading conditions. Conclusions: SG can reduce the maximum stress in the vertebra and intervertebral discs, offering better biomechanical performance and improved stability than IG.