Objective: To analyse the anatomical conditions of transverse sacroiliac screw (TSS) about the S1 and S2 segments in order to develop and validate a locked navigational template for TSS placement. Methods: A total of 22 patients with sacral fractures were involved in this study from May 2018 to February 2019. Patients were divided into two groups according to the surgery procedure: locked template group and conventional group. The CT data of 90 normal sacra were analysed. The long axis, short axis and lengths of TSS, cancellous corridors were measured through 3D modelling. A patient-specific locked navigation template based on simulated screws was designed and 3D printed and then used to assist in TSS placement. The operative time and radiation times were recorded. The Matta criteria and grading score were evaluated. The entry point deviation of the actual screw placement relative to the simulated screw placement was measured, and whether the whole screw was in the cancellous corridor was ob`served. Results: S1 screws with a diameter of 7.3 mm could be inserted into 69 pelvises, and S2 screws could be inserted in all pelvises. The S1 cancellous corridor had a long axis of 25.44 ± 3.32 mm in males and 22.91 ± 2.46 mm in females, a short axis of 14.21 ± 2.19 mm in males and 12.15 ± 3.22 mm in females, a corridor length of 153.07 ± 11.99 mm in males and 151.11 ± 8.73 mm in females, and a proportional position of the optimal entry point in the long axis of the cancellous corridor of 35.96 ± 10.31% in males and 33.28 ± 7.2% in females. There were significant differences in the corridor long axis and corridor short axis between sexes (p < 0.05), and there were no significant differences in corridor length and proportional position of the optimal entry point in the long axis of the cancellous corridor between sexes (p > 0.05). The S2 cancellous corridor had a long axis of 17.58 ± 2.36 mm in males and 16 ± 2.64 mm in females, a short axis of 14.21 ± 2.19 mm in males and 13.14 ± 2.2 mm in females, a corridor length of 129.95 ± 0.89 mm in males and 136.5 ± 7.96 mm in females, and a proportional position of the optimal entry point in the long axis of the cancellous corridor of 46.77 ± 9.02% in males and 42.25 ± 11.95% in females. There were significant differences in the long axis, short axis and corridor length (p < 0.05). There was no significant difference in the proportional position of the optimal entry point in the long axis of the cancellous corridor (p > 0.05). A total
Objective: To evaluate the accuracy and safety of a combined 3D printed guide template (combined template) to assist iliosacral (IS) screw placement for sacral fracture and dislocation.Methods: A total of 37 patients, 24 men and 13 women, age from 22 to 68 years old, diagnosed with a sacral fracture and dislocation were involved in this study for retrospective analysis from January 2016 to February 2018. There were 19 patients in the template group (42 screws) and 18 patients in the conventional group (31 screws). In the combined template group, IS screw placement was assisted by a combined 3D printed template; in the conventional group, the IS screws were placed freehand under fluoroscopy. The accuracy of the IS screw placement was evaluated by comparing the screw angle and the location of the screw entry point between the actual and the simulated screw in the combined template group. The safety of the IS screw placement was evaluated by comparing the quality of the reduction, the grading of the screws, the operation time, and radiation exposure times between groups.Results: A total of 73 pedicle screws were placed in 37 patients: 42 screws (30 S1, 12 S2) in the combined template group and 31 screws (23 S1, 8 S2) in the conventional group. In the conventional group, 1 patient developed symptoms of L5 nerve stimulation. In the combined template group, the average operative time of each screw was 25.01 AE 2.90 min, with average radiation exposure times of 12.05 AE 4.00. In the conventional group, the average operative time of each screw was 46.24 AE 9.59 min, with an average radiation exposure time of 56.10 AE 6.75. There were significant differences in operation and radiation exposure times between groups. The rate of screw perforation was lower in the combined template group (2 of 42 screws, 0 at grade III and 2 at grade II) than in the conventional group (5 of 38 screws, 2 at grade III and 3 at grade III). In the combined template group, the mean distance between the entry points of the actual and simulated screws was 1.4 AE 0.9 mm, with a mean angle of deviation of 2.1 AE 1.6 . All patients were followed up once every 3 months and were followed for 3 to 12 months.Conclusion: Using the combined template to assist with the insertion of IS screws delivered good accuracy, less fluoroscopy and shorter operation time, and avoided neurovascular injury as a result of screw malposition.
Objective: To evaluate the accuracy of percutaneous pedicle screw (PPS) placement aided by a new drill guide template.Methods: The patients were divided into guide template group and conventional perspective group. In the conventional perspective group, the screws were placed by hand under fluoroscopy. In the guide template group, the screw placement was aided by a new drill guide template, and the drill guide template is designed according to the patient's ideal pedicle screw, but not based on skin morphology. The accuracy was evaluated by comparing the following parameters between the two groups: pedicle breach level, inclination angle deviation between the left and right screws, sagittal angle deviation between the left and right screws, and position deviation of the left and right screw entry points. The consistency of the postoperative screw angle and the corresponding guide template inclination angle was compared in the guide template group. The operative time, blood loss, and radiation times were compared between the groups.Results: A total of 146 patients (876 screws) were enrolled in our study including 79 (474 screws) in the guide template group and 67 (402 screws) in the conventional perspective group. The pedicle breach level in the guide template group (22/474) was significantly lower than that in the conventional perspective group (47/402) (P < 0.05). The position and direction deviations of the left and right screws in the guide template group (2.06 AE 1.02 mm, 1.23 AE 1.25 mm, 1.83 AE 1.49 ) were significantly less than those in the conventional perspective group (5.33 AE 2.99 mm, 4.32 AE 3.25 mm, 2.87 AE 1.56 ). The operation time, blood loss, and radiation times were significantly lower in the guide template group (80.49 AE 9.14 min, 50.42 AE 8.9 mL, 11.02 AE 2.44) than those in the conventional perspective group (108.1 AE 21.18 min, 71.7 AE 17.09 mL, 23.53 AE 4.54). There were no significant differences between the postoperative screw angle and the corresponding guide template angle in the guide template group.Conclusion: PPS placement aided by a new drill guide template yielded higher screw accuracy and less operative time, blood loss, and radiation exposure than traditional screw placement.
During the surgical resection and reconstruction of a pathological femoral fracture, the removal of the femoral tumor leaves a large bone defect. Thus, it is necessary to reconstruct the defect and perform internal fixation. Polyether ether ketone (PEEK) has been widely used in spinal fusion and cranioplasty given its excellent biomechanical properties, biocompatibility, and stability. The typical design method of femoral prosthesis is based on the contralateral mirror image model (M-model), and we propose a novel method for designing femoral prosthesis, which is based on the cross section and centerline of the mirrored femur (C-model). In this study, the femoral shaft prostheses based on two models were manufactured using fused deposition modeling technology, and we use mechanical test and finite element analysis (FEA) to reveal the differences in mechanical properties of the two models. The mechanical results showed that the maximum loading force and yield strength were increased by 3% and 6% in the C-model prosthesis compared with the M-model prosthesis, respectively. In FEA, the results indicate that the C-model prosthesis could reduce the stress concentration by 5.4%-10.9% compared to the M-model prosthesis.Finally, the 3D-printed PEEK femoral shaft prosthesis based on C-model was implanted, no early complications occurred. Postoperative radiological examination indicated that the prosthesis and the femoral osteotomy end were closely matched and fixed well.
Deep learning models are widely used in daily life, which bring great convenience to our lives, but they are vulnerable to attacks. How to build an attack system with strong generalization ability to test the robustness of deep learning systems is a hot issue in current research, among which the research on black-box attacks is extremely challenging. Most current research on black-box attacks assumes that the input dataset is known. However, in fact, it is difficult for us to obtain detailed information for those datasets. In order to solve the above challenges, we propose a multi-sample generation model for black-box model attacks, called MsGM. MsGM is mainly composed of three parts: multi-sample generation, substitute model training, and adversarial sample generation and attack. Firstly, we design a multi-task generation model to learn the distribution of the original dataset. The model first converts an arbitrary signal of a certain distribution into the shared features of the original dataset through deconvolution operations, and then according to different input conditions, multiple identical sub-networks generate the corresponding targeted samples. Secondly, the generated sample features achieve different outputs through querying the black-box model and training the substitute model, which are used to construct different loss functions to optimize and update the generator and substitute model. Finally, some common white-box attack methods are used to attack the substitute model to generate corresponding adversarial samples, which are utilized to attack the black-box model. We conducted a large number of experiments on the MNIST and CIFAR-10 datasets. The experimental results show that under the same settings and attack algorithms, MsGM achieves better performance than the based models.
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