Operative Effect Comparison of Flexible Drill Guiding vs. Traditional Drill Guiding Template for Lower Cervical Pedicle Screw Insertion: A Retrospective Analysis.

OBJECTIVE: Accurately inserting pedicle screws is the key point of posterior pedicle screw fixation for lower cervical spine (C3-C7) instability. 3D printing technology can improve the accuracy of screw placement. This study compared the safety of 3D-printed flexible drill guiding template vs. traditional rigid drill guiding template for lower cervical pedicle screw insertion. METHODS: This was a retrospective study. A total of 34 patients who underwent lower cervical pedicle screw fixation from March 2018 to May 2021 were enrolled in this study, and they were divided into the flexible drill flexible drill group and the traditional drill group. A total of 18 patients in the flexible drill flexible drill group underwent pedicle screw fixation assisted by 3D printed flexible drill guiding templates for the lower cervix, and 16 patients in the traditional drill group underwent pedicle screw fixation assisted by 3D printed regular drill guiding templates for the lower cervix. The length of the incision and intraoperative blood loss during surgery were recorded and compared for the two groups. The grade, deviation of the screw entry point, deviation of the screw medial angle and screw length were measured and compared after surgery for the two groups by independent-sample tests. RESULTS: There was a significant difference in the length of the incision and blood loss between the two groups (P < 0.05). There was a significant difference between the two groups for grade (P = 0.016). The deviation of the screw entry point was 0.65 ± 0.50 mm in the flexible drill group and 0.78 ± 0.83 mm in the traditional drill group. The deviation of the screw medial angle was 2.14 ± 1.78 in the flexible drill group and 4.23 ± 2.51 in the traditional drill group, with a significant difference between the two groups (P < 0.05). CONCLUSION: Compared with regular guiding techniques, lower cervical pedicle screw placement assisted by multistep navigation templates and flexible K-wires results in less trauma and better safety.

Dual Attention Adversarial Attacks With Limited Perturbations.

The construction of undetectable adversarial examples with few perturbances remains a difficult problem in adversarial attacks. At present, most solutions use the standard gradient optimization algorithm to build adversarial examples by applying global perturbations to benign samples and then launch attacks on the targets (e.g., face recognition systems). However, when the perturbance size is limited, the performance of these approaches suffers substantially. The content of crucial places in an image, on the other hand, will impact the final prediction; if these areas can be investigated and limited perturbances introduced, an acceptable adversarial example will be constructed. Based on the foregoing research, this article offers a dual attention adversarial network (DAAN) to produce adversarial examples with limited perturbations. DAAN initially searches for effective areas in an input image using the spatial attention network and channel attention network, and then creates space and channel weights. Following that, these weights direct an encoder and a decoder to generate effective perturbation, which is then combined with the input to produce an adversarial example. Finally, the discriminator determines if the created adversarial examples are true or false, and the attacked model is utilized to determine whether the generated samples fit the attack targets. Extensive studies on various datasets show that DAAN not only delivers the best attack performance across all comparison algorithms with few perturbations, but it can also significantly improve the defensiveness of the attacked models.

A Novel C2 Screw Corridor Parallel to the Sagittal Plane for Transpedicular Fixation - A 3D-CT Study.

STUDY DESIGN: A 3D-CT Study. OBJECTIVE: To research the feasibility and advantages of screw corridors parallel to the sagittal plane (SPC) of the C2 for transpedicular fixation. SUMMARY OF BACKGROUND DATA: A total of 125 patients were enrolled for analysis, and the 3D model of the C2 for the 125 patients were reconstructed and analyzed. METHODS: The SPC screw and the corridor of the general pedicle (GPC) screw of both sides were inserted into these C2 models. The anatomic parameters of the SPC and GPC, including the inner circle diameter, length of the corridors, medial angle and cephalad angle, were measured and compared. The anatomic location of the entry point for the SPC screw was evaluated. RESULTS: The diameter of the SPC averaged 5.5±1.8 mm; 81.2% (203/250) were larger than 4 mm. There was no significant difference between the SPC and GPC in diameter or percentage of diameter greater than 4 mm. There was a significant difference between the length of the SPC (25.3±2.4 mm) and the GPC (27.4±2.2 mm). The cephalad angle was 51.6±6.9° for the SPC and 43.3±4.4° for the GPC, and there was a significant difference between the SPC and GPC. The entry point of the SPC screw was located on the cortical crest at the lower 1/4 of the lamina and located to the lower and inner side of the GPC screw entry point. CONCLUSION: It is feasible for most patients to accommodate an SPC screw with a diameter of 3.5 mm. All SPC screws crossed the pedicle completely. The optimal entry point of the SPC screw was located on the cortical crest of the axial lamina.

Finite Element Analysis and Transiliac-Transsacral Screw Fixation for Posterior Pelvic Ring with Sacrum Dysplasia.

OBJECTIVE: Posterior pelvic ring sacroiliac screws are preferred by clinicians for their good biomechanical performance. However, there are few studies on mechanical analysis and intraoperative screw insertion of the dysplastic sacrum and sacroiliac screw. This study investigated the biomechanical performance of oblique sacroiliac screws (OSS) in S1 combined with transiliac-transsacral screws (TTSs) in S2 for pelvic fracture or sacroiliac dislocation with dysplastic sacrum and evaluated the safety of screw placement assisted by the navigation template. METHODS: Six models were established, including one OSS fixation in the S2 segment, one transverse sacroiliac screw (TSS) fixation in the S2 segment, one TTS fixation in the S2 segment, one OSS fixation in the S1 and S2 segments, one OSS fixation in the S1 segment and one TSS fixation in the S2 segment, one OSS fixation in the S1 segment and one TTS fixation in the S2 segment. Then, finite element analysis (FEA) was performed. Twelve dysplastic sacrum patients with pelvis fracture or sacroiliac dislocation underwent OSS insertion in the S1 combined with TTS insertion in the S2 under the assistance of the patient-specific locked navigation template. Grading and Matta scores were evaluated after surgery. RESULTS: In the one-screw fixation group, the vertical displacements of the sacrum surface of S2 OSS, S2 TSS and S2 TTS were 1.23, 1.42, and 1.22 mm, respectively, and the maximum stress of screw were 139.45 MPa, 144.81 MPa, 126.14 MPa, respectively. In the two-screw fixation group, the vertical displacements of the sacrum surface of the S1 OSS + S2 OSS, S1 OSS + S2 TSS and S1 OSS + S2 TTS were 0.91, 1.06, and 0.75 mm, respectively, and the maximum stress of screw were 149.26 MPa, 167.13 Pa, 136.76 MPa, respectively. Clinically, a total of 12 TTS and OSS were inserted under the assistance of navigation templates, with a surgical time of 55 ± 7.69 min, bleeding of 57.5 ± 18.15 ml and radiation times of 14.5 ± 4.95. One of the TTS and one of the OSS were grade 1, and the other screws were grade 0. The Matta scores of nine patients were excellent, and three patents were good. CONCLUSION: OSS in the S1 combined with TTS in the S2 had the best mechanical stability in six models, and it is safe for screw insertion assisted by the patient-specific locked navigation template.

Comparison of Perpendicular to the Coronal Plane versus Medial Inclination for C2 Pedicle Screw Insertion Assisted by 3D Printed Navigation Template.

OBJECTIVE: C2 pedicle screw insertion is very important in posterior upper cervical surgery. The traditional screw placement technique requires us to consider both medial inclination and cephalad angle, it is difficult to operate intraoperatively. This paper is to explore a novel method of C2 pedicle screw placement compared with traditional C2 pedicle screw. METHODS: A total of 44 patients diagnosed with atlantoaxial fracture or instability from May 2018 to November 2020 were involved in this retrospective study, and they were divided into C2-PPS group (perpendicular to the coronal plane C2 screw, 24 patients) and C2-TPS group (traditional C2 pedicle screw, 20 patients). The diameter of the maximum tangential circle, distance between geometric center and median sagittal plane and screw length of PPS and TPS were measured based on the 3D model of C2, respectively. Then the 3D printed navigation templated were designed and manufactured by 3D printing to assisted the PPS and TPS placement, respectively. The surgical time and radiation exposure times during operation were recorded; the post-operative grading criteria, deviation of screw entry point and deviation of screw angle of two groups were evaluated, respectively. RESULTS: A total of 48 screws were inserted in the C2-PPS group, and 40 screws were inserted in the C2-TPS group. There were 46 screws with grade 0 (95.8%) in the PPS group and 31 screws with grade 0 (77.5%) in the TPS group, (P = 0.03). The radiation exposure times in the C2-PPS group and C2-TPS group were 4.7 ± 1.5 and 7.8 ± 3.8, respectively, (P = 0.045). The deviations of screw entry point in the C2-PPS group and C2-TPS group were 1.2 ± 0.8 mm and 3.2 ± 1.3 mm, respectively; the deviations of screw angle in the C2-PPS group and C2-TPS group were 2.1 ± 1.6° and 4.8 ± 2.0°, respectively, (P = 0.000). The diameters of the maximum tangential circle in the C2-PPS group and C2-TPS group were 5.5 ± 1.0 mm and 5.3 ± 0.9 mm, respectively. The distances between the geometric center and median sagittal plane in the C2-PPS group and C2-TPS group were 15.4 ± 2.3 mm and 18.0 ± 3.3 mm, respectively; The screw lengths in the C2-PPS group and C2-TPS group were 25.9 ± 3.2 mm and 27.6 ± 3.7 mm, respectively, (P = 0.000). CONCLUSION: Eighty percent of C2-PPS corridor can accommodate a 3.5 mm diameter screw, and with an average screw length of 26 mm. Navigation templates assisted the C2-PPS placement is less surgical time, less radiation exposure times, more safe and more accurate than C2-TPS.

Biomechanical and osteointegration study of 3D-printed porous PEEK hydroxyapatite-coated scaffolds.

The objective of this study as to evaluate the biomechanical and osteointegration properties of 3D printed porous polyetheretherketone (PEEK) with hydroxyapatite (HA) coating by simulated body fluid (SBF) method. Cylindrical scaffolds were designed and fabricated by using PEEK material through fused deposition molding (FDM). The scaffolds were divided into solid group, porous group and porous-HA group (decorated by hydroxyapatite). The mechanical properties of each group of scaffolds were tested. Then, a total of 12 New Zealand rabbits were implemented for implantation of scaffolds at femoral condyle. Finally, the osteointegration ability of scaffolds were evaluated by Micro computed tomography (Micro-CT), histology and fluorescence staining. The HA was successfully decorated on the surface of the PEEK scaffold. The modulus of solid, porous and porous-HA group was 1289.43 ± 71.44 MPa, 196.36 ± 9.89 MPa and 183.29 ± 7.71 MPa, and the compressive strength was 107.24 ± 5.15 MPa, 33.12 ± 3.86 MPa and 29.99 ± 4.16 MPa, respectively. The micro-CT results showed that the bone volume/total volume ratio (BV/TV) in the porous-HA group was significantly greater than that in solid and porous group. Compared with porous group, the trabecular number (Tb. N) and trabecular thickness (Tb. Th) of porous-HA group was higher, and the trabecular spacing (Tb. Sp) was lower. The histology and fluorescence staining showed that more new bone tissue was formed in the porous-HA at different periods compared with the porous and solid groups. In addition, according to the results of the biomechanical test and osteointegration assessment, the biomechanical properties of 3D-printed porous PEEK scaffolds are close to human trabecular bone tissue, and the hydroxyapatite coating does not degrade its biomechanical performance. The porous structure can facilitate the integration of bone tissue, and the HA coating can markedly improve this process.

Navigation Template Design and the Anatomic Measurement for Anterograde Transpubic Screws.

OBJECTIVE: For pelvic ring fractures, screw fixation became a popular technique for its good biomechanical performance. The safe insertion of anterograde the transpubic screw is important for patients with anterior pelvic ring fractures. This paper is to research the anatomical parameters of the anterograde transpubic screw corridor and evaluate the safety of anterograde transpubic screw placement assisted by the assembled navigation template. METHODS: Fifty subjects with normal pelvic, 25 men and 25 women, age from 20 to 60 were enrolled, and their ilium were 3D reconstructed. The ilium was divided into zone I, zone II and zone III. Zone I and zone III was defined as medial and lateral to the obturator foramen, respectively. Zone II is located between zones I and III. The corridor A is formed by zone I and zone II and corridor B is formed by zone I, zone II and zone III. The diameter and length of the inner circle, the distance from the center of the inner circle to the posterior superior and to the inferior iliac spine of corridor A and corridor B were measured, respectively. Nine patients with pelvic fractures underwent anterograde transpubic screw and transverse sacroiliac screw placement assisted by the assembled navigation template and were retrospectively analyzed. Operation time, blood loss, incision length and fluoroscopy times were recorded. Grading score and Matta score were evaluated after surgery. RESULTS: In the 50 subjects, the diameter of corridor A was 11.16 ± 2.13 mm, and that of corridor B was 8.54 ± 1.52 mm. The length of corridor A was 86.39 ± 9.35 mm, and that of corridor B was 117.05 ± 5.91 mm. The surface distance from the screw entry point to the posterior superior iliac spine in corridor A was 109.31 ± 11.06 mm, and that in corridor B was 127.86 ± 8.23 mm. The surface distance from the screw entry point to the posterior inferior iliac spine in corridor A was 91.16 ± 10.34 mm, and that in corridor B was 106.92 ± 7.91 mm. A total of 18 sacroiliac transverse screws and 11 anterograde transpubic screws were inserted assisted by assembled navigation templates for nine patients. The average operation time was 108.75 ± 25.71 min, the blood loss was 141.11 ± 50.21 ml, the incision length was 14 ± 4.62 cm, and the intraoperative fluoroscopy was 17.89 ± 4.01 times. CONCLUSION: Transpubic screw corridor can be obtained by 3D reconstruction. For the majority of patients, the anterograde pubic ramus corridor accommodated a 6.5 mm diameter screw. It is safe to use anterograde transpubic screw placement assisted by an assembled navigation template.

Custom design and biomechanical clinical trials of 3D-printed polyether ether ketone femoral shaft prosthesis.

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.

Feasibility of Atlas Pedicle Screw Fixation Perpendicular to the Coronal Plane-A 3D Anatomic Analysis.

STUDY DESIGN: An anatomic analysis. OBJECTIVE: To investigate the feasibility of the ideal atlas pedicle screw trajectory perpendicular to the coronal plane via atlas digital 3D reconstruction. METHODS: One hundred adult atlases were evaluated in this study. The projection of the corridor for atlas pedicle screw fixation perpendicular to the coronal plane was quickly obtained using the perspective model of 3D reconstruction, and the area, long axis, short axis and width of the pedicle corridor were measured. The inner trajectory was near the lateral wall of the pedicle, and the center of the corridor was point A. The lateral trajectory was near the lateral wall of the transverse foramen, and the center of the trajectory was point C. The midpoint of A and C was B. The length of the inner, middle and lateral trajectorys were measured. The distances from points A, B and C to the posterior tubercle of the atlas and safety swing angle were measured. RESULTS: From the dorsal view, the pedicle corridor was fitted into an ellipse with an average long axis of 13.6 mm, an average short axis of 5.2 mm, and an average area of 56.3 mm2. From the axial view, the pedicle corridor had an average width of 9.4 mm. The average lengths of the inner trajectory, middle trajectory and lateral trajectory were 31.7 mm, 28.7 mm and 25.1 mm, respectively; The average distances from the posterior tubercle to points A, B and C were 17.1 mm, 20.8 mm and 24.5 mm, respectively. The average swing angles from points A, B and C were 16.1°, 25.5°, and 28.1°, respectively. CONCLUSION: Atlas pedicle screw fixation perpendicular to the coronal plane is feasible for almost all the volunteers. Pedicle screws close to the pedicle lateral wall of the atlas posterior arch perpendicular to the coronal plane is an advanced technique that is easy to master.

Three-dimensional anatomic analysis and navigation templates for C1 pedicle screw placement perpendicular to the coronal plane: a retrospective study.

OBJECTIVE: To explore the corridor for atlas pedicle screw placement perpendicular to the coronal plane and to develop patient-specific navigation templates for pedicle screw placement. METHODS: This study is a retrospective analysis. A total of 71 patients (41 males and 30 females) were involved in this study from June 2016 to June 2018, and they were divided into a template group (39 patients) and a conventional group (32 patients). The CT-based 3D reconstruction models were analyzed in the template group. From the perspective of the 3D atlas in a coronal view, the pedicle corridor was obtained. Taking the center of the tangential circle of the pedicle as the entry point, we simulated screw placement perpendicular to the coronal plane. Then, the individual navigation template was designed and used in surgery. In the conventional group, free-hand pedicle screw placement was performed perpendicular to the coronal plane. The diameter of the maximum tangential circle and screw length of the pedicle corridor were measured in the template group. The surgical time, radiation exposure time, screw grading criteria and so on were evaluated and compared between the two groups after surgery. RESULTS: ;The diameter of the maximum tangential circle and the distance between the entry point and posterior tubercle were significantly greater in males than in females. The operation was successfully completed in all patients, without aggravation of nerve injury, and the follow-up was 12-20 months, with an average of 15.6 months. A total of 78 screws were inserted in the template group, and 64 screws were inserted in the conventional group. The surgical times in the template group and conventional group were 76.47±24.44 min and 125.63±36.41 min, respectively. The radiation exposure times in the template group and conventional group were 3.51±1.77 and 10.15±4.95, respectively, and there was a significant difference between the two groups. In the template group, the deviation in the screw entry point and screw angle were 1.92±1.67 mm and 2.08±1.98°, respectively. The medial angle deviation between the left and right sides was 2.71±1.88° in the template group, which was significantly less than the deviation of 3.76±2.22° in the conventional group. CONCLUSION: A pedicle screw trajectory perpendicular to the coronal plane can be quickly obtained based on the perspective of 3D models. The technique of screw placement perpendicular to the coronal plane assisted by navigation templates has a shorter operative time, lessintraoperative fluoroscopy and a higher safety of screw placement than traditional surgery.

3D-Printed Screw-Rod Auxiliary System for Unstable Atlas Fractures: A Retrospective Analysis.

OBJECTIVE: To develop and validate the efficacy of a 3D-printed screw-rod auxiliary system for unstable atlas fractures. METHODS: This research is a retrospective analysis, and a total of 14 patients, including 11 males and three females, were enrolled in our hospital from January 2017 to March 2019 who underwent occipitocervical fusion assisted by the 3D-printed screw-rod auxiliary system were reviewed, and with an average age of 53.21 ± 14.81 years, an average body mass index (BMI) of 23.61 ± 1.93 kg/m2 . The operation time, blood loss and radiation times during the operation were recorded. The maximum fracture displacement values of pre- and post-operation were measured based on CT imaging. All screw grades were evaluated after surgery. The occipital-cervical 2 (O-C2 ) angle and occipitocervical inclination (OCI) angle of pre-operation, post-operation and the last following-up were measured. The dysphagia scale 3 months after surgery and at the last follow-up, the Neck Disability Index (NDI) 3 months after surgery and at the last follow-up were assessed. RESULTS: All patients were completed the surgery successfully. There was no patient with severe dysphagia or aggravation of nerve injury. The follow-up was from 12 to 14 months, and with an average of 12.5 months. The average surgery time, average blood loss and average radiation times for the 14 patients were 112.14 min, 171.43 mL and 5.07 times, respectively. There was a significant difference in maximum fracture displacement between pre- and post-operation values (P < 0.05). A total of 56 screws were inserted in 14 patients, among them, three screws were classified as grade 1, and the other screws were classified as grade 0. There was a significant difference in the O-C2 between pre-operation and 3 days after operation (P = 0.002); There was a significant difference in OCI angles between pre-operation and 3 days after operation (P < 0.05); there was no significant difference in the O-C2 or OCI angle between 3 days after the operation and the last follow-up (P = 0.079; P = 0.201). The dysphagia scales of two patients were assessed as mild at 3 months after surgery, and the others were assessed as normal at 3 months after surgery. All patients' dysphagia scores returned to normal at the last follow-up. The average NDI and average neck Visual Analogue Scale (VAS) scores at the last follow-up were 2.53 and 8.41, respectively. CONCLUSION: It can objectively restore the OCI to normal with few post-operative complications under the assistance of a screw-rod auxiliary system to perform occipitocervical fusion for unstable atlas fractures and atlantooccipital joint instability.

Anatomical conditions and patient-specific locked navigation templates for transverse sacroiliac screw placement: a retrospective study.

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 of 20 transversal sacroiliac screws were successfully implanted into 10 patients with the assistance of locked navigation templates, and a total of 24 transversal sacroiliac screws were successfully implanted into 12 patients under C-arm fluoroscopy. There was a significant difference in surgical time (88 ± 14.76 min vs 102.5 ± 17.12 min, p = 0.048), radiation times (11.5 ± 1.78 vs 54.83 ± 6.59, p < 0.05) and screw grading between two groups (nineteen screws in grade 0, one screw in grade 1 and 0 screws in grade 2 vs fourteen screws in grade 0, 8 screws in grade 1 and 2 screws in grade 2, p = 0.005). All screw entry point deviations were shorter than the short axis of the cancellous corridor, and all screws were located completely within the cancellous corridor. CONCLUSION: Approximately 76% of males and females can accommodate screws with diameters of 7.3 mm in S1, and all persons can accommodate the same screw in S2. From the standard lateral perspective of the sacrum, the optimal entry point of the transverse screw is in the first 1/3 of the cancellous corridor for S1 and the centre of the cancellous corridor for S2. The patient-specific locked navigation template assisted in TSS placement with less operative time, less intraoperative fluoroscopy and higher safety of screw placement compared with traditional surgery.

Percutaneous Pedicle Screw Placement Aided by a New Drill Guide Template Combined with Fluoroscopy: An Accuracy Study.

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 ± 1.02 mm, 1.23 ± 1.25 mm, 1.83° ± 1.49°) were significantly less than those in the conventional perspective group (5.33 ± 2.99 mm, 4.32 ± 3.25 mm, 2.87° ± 1.56°). The operation time, blood loss, and radiation times were significantly lower in the guide template group (80.49 ± 9.14 min, 50.42 ± 8.9 mL, 11.02 ± 2.44) than those in the conventional perspective group (108.1 ± 21.18 min, 71.7 ± 17.09 mL, 23.53 ± 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.

Combined 3D Printed Template to Guide Iliosacral Screw Insertion for Sacral Fracture and Dislocation: A Retrospective Analysis.

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 ± 2.90 min, with average radiation exposure times of 12.05 ± 4.00. In the conventional group, the average operative time of each screw was 46.24 ± 9.59 min, with an average radiation exposure time of 56.10 ± 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 ± 0.9 mm, with a mean angle of deviation of 2.1° ± 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.

Synthesis and dielectric properties of the eco-friendly insulating gas thiazyl trifluoride.

Sulfur hexafluoride (SF6), which is known as a superior electrically insulating and arc-quenching medium, plays a decisive role in the modern transmission and distribution network of electric energy, especially in high-voltage power networks. However, the ever-increasing usage of SF6 also leads to the continuous escalation of atmospheric SF6 levels, which is considered to be the main cause of the greenhouse effect. To decrease this environmental impact, eco-friendly alternatives to SF6 have been researched for decades. To date, no significant success has been made regarding replacement gases for transmission networks. Some potential alternatives have comparatively lower global warming potential (GWP) but involve technical trade-offs. Thiazyl trifluoride, which has some excellent chemical and electric properties, is a novel substitution candidate for SF6. In this article, an efficient synthetic route starting from sulfur monochloride and followed by ammonization and fluorination was proposed. The structures of the intermediates and the target products were determined by X-ray diffraction (XRD), infrared spectroscopy (IR), and gas chromatography-mass spectrometry (GC-MS). The effects of some determining factors on the yield and purity, including the molar ratio of the reactants, recrystallization conditions and condensation temperature, were also investigated. The results showed that the overall yield of thiazyl trifluoride was approximately 25%, while the purity could be up to 90.6% under optimal conditions.

[Effectiveness analysis of three-dimensional printing assisted surgery for unstable pelvic fracture].

OBJECTIVE: To evaluate the effectiveness of three-dimensional (3D) printing assisted internal fixation for unstable pelvic fractures. METHODS: The clinical data of 28 patients with unstable pelvic fractures admitted between March 2015 and December 2017 were retrospectively analyzed. The patients were divided into two groups according to different surgical methods. Eighteen cases in the control group were treated with traditional anterior and posterior open reduction and internal fixation with plate; 10 cases in the observation group were treated with 3D printing technology to make pelvic models and assist in shaping the subcutaneous steel plates of the anterior ring. Sacroiliac screw navigation template was designed and printed to assist posterior ring sacroiliac screw fixation. There was no significant difference between the two groups in gender composition, age, cause of injury, fracture type, and time interval from injury to surgery ( P>0.05). The operation time, intraoperative blood loss, intraoperative fluoroscopy times, incision length, waiting time for weight-bearing exercise, and fracture healing time were recorded and compared between the two groups. Majeed score was used to evaluate the function at last follow-up. At immediate after operation, the reduction was evaluated according to Matta imaging scoring criteria, and the success of sacroiliac joint screw implantation in the observation group was evaluated. The deviation of screw entry point and direction between postoperative screws and preoperative simulated screws were compared in the observation group. RESULTS: All the operation was successfully completed, and all patients were followed up 6-18 months (mean, 14.4 months). In the control group, 1 case had wound infection and 2 cases had deep vein thrombosis. No serious complication such as important blood vessels, and nerve injury and pulmonary embolism occurred in other patients in the two groups. No screw pulling out or steel plate breaking occurred. The operation time, intraoperative blood loss, fluoroscopy times, incision length, and waiting time for weight-bearing exercise of the control group were significantly more than those of the observation group ( P<0.05); there was no significant difference in fracture healing time between the two groups ( t=0.12, P=0.90). There was no significant difference in reduction quality between the two groups at immediate after operation ( Z=-1.05, P=0.30); Majeed score of the observation group was significantly better than that of the control group at last follow-up ( Z=-2.42, P=0.02). The success rate of sacroiliac joint screw implantation in the observation group reached category Ⅰ. In the observation group, the deviation angle of the direction of the screw path between the postoperative screw and the preoperative simulated screw implant was (0.09±0.22)°, and the deviation values of the entry points on the X, Y, and Z axes were (0.13±0.63), (0.14±0.58), (0.15±0.53) mm, respectively. There was no significant difference when compared with those before the operation (all values were 0) ( P>0.05). CONCLUSION: Computer design combined with 3D printing technology to make personalized pelvic model and navigation template applied to unstable pelvic fractures, is helpful to accurately place sacroiliac screw, reduce the operation time, intraoperative blood loss, and the fluoroscopy times, has good waiting time for weight-bearing exercise and function, and it is an optional surgical treatment for unstable fractures.

[Accuracy analysis and clinical application of the progressive navigation template system to assist atlas-axial pedicle screw placement].

Objective: To investigate the accuracy of progressive three-dimensional navigation template system (abbreviated as progressive template) to assist atlas-axial pedicle screw placement. Methods: The clinical data of 33 patients with atlas-axial posterior internal fixation surgery between May 2015 and May 2017 were retrospectively analyzed. According to the different methods of auxiliary screw placement, the patients were divided into trial group (19 cases, screw placement assisted by progressive template) and control group (14 cases, screw placement assisted by single navigation template system, abbreviated as initial navigation template). There was no significant difference in gender, age, cause of injury, damage segments, damage types, and preoperative Frankel classification between the two groups ( P>0.05). The operation time and intraoperative blood loss of the two groups were compared. The safety of screw placement was evaluated on postoperative CT by using the method from Kawaguchi et al, the deviation of screw insertion point were calculated, the angular deviation of the nailing on coordinate systems XOZ, XOY, YOZ were calculated according to Peng's method. Results: All patients completed the operation successfully; the operation time and intraoperative blood loss in the trial group were significantly less than those in the control group ( t=-2.360, P=0.022; t=-3.006, P=0.004). All patients were followed up 12-40 months (mean, 25.3 months). There was no significant vascular injury or nerve injury aggravation. Postoperative immediate X-ray film and CT showed the dislocation was corrected. Postoperative immediate CT showed that all 76 screws were of grade 0 in the trial group, and the safety of screw placement was 100%; 51 screws were of grade 0, 3 of gradeⅠ, and 2 of gradeⅡ in the control group, and the safety of screw placement was 91.1%; there was significant difference in safety of screw placement between the two groups ( χ2=7.050, P=0.030). The screw insertion point deviation and angular deviation of the nailing on XOY and YOZ planes in the trial group were significantly less than those in the control group ( P<0.05). There was no significant difference in angular deviation of the nailing on XOZ between the two groups ( t=1.060, P=0.290). Conclusion: Compared with the initial navigation template, the progressive navigation template assisting atlas-axial pedicle screw placement to treat atlas-axial fracture with dislocation, can reduce operation time and intraoperative blood loss, improve the safety of screw placement, and match the preoperative design more accurately.

[Surgical treatment strategy for the "shell" phenomenon after thoracolumbar fracture].

Objective: To explore the surgical treatment strategy of the vertebral "shell" after thoracolumbar fracture, and provide clinical reference for the intervention and treatment of "shell". Methods: Between June 2015 and January 2017, 53 patients with high risk of vertebral "shell" after thoracolumbar fracture surgery were enrolled in a prospective study according to the selection criteria. All patients were randomly divided into two groups according to the order of treatment, 27 cases in the treatment group were treated with short-segment fixation combined with vertebral reconstruction, 26 cases in the control group were treated with short-segment fixation. There was no significant difference in gender, age, injury cause, Denis classification, fracture segment, the degree of injured vertebra compression, bone mineral density, and American Spinal Cord Injury Association (ASIA) classification between the two groups ( P>0.05). The degree of injured vertebra compression, visual analogue scale (VAS) score, and Oswestry disability index (ODI) score at preoperation, immediate after operation, and last follow-up were calculated and compared between the two groups. The "shell" phenomenon and surgery complications were observed at the same time. Results: All patients were followed up 12-18 months with an average of 14.4 months. There were 5 cases of "shell" phenomenon in the treatment group and 4 cases of nonunion at last follow-up, 23 cases of "shell" phenomenon in the control group and 19 cases of nonunion at last follow-up; there was a significant difference between the two groups ( P<0.05). In the treatment group, 1 case had incision fat liquefaction and 4 cases had bone cement leakage; in the control group, 2 cases had screw loosening and 1 case had unilateral connecting rod rupture; there was no significant difference in the incidence of complications between the two groups ( χ2=0.504, P=0.478). The degree of injured vertebra compression, VAS score, and ODI score were significantly improved in both groups at immediate after operation and last follow-up ( P<0.05). There was no significant difference in the degree of injured vertebra compression between the two groups at immediate after operation ( P>0.05), but which was significantly higher in the control group than that in the treatment group at last follow-up ( P<0.05). Except that the ODI score of the control group was significantly higher than that of the treatment group at last follow-up ( P<0.05), there was no significant difference in VAS score and ODI score between the two groups at the other time points ( P>0.05). Conclusion: The treatment of thoracolumbar fracture with short-segment fixation combined with injured vertebral reconstruction can effectively prevent the "shell" phenomenon, which is conducive to maintaining the height of injured vertebral and improving the long-term function. The effectiveness is satisfactory.

[Imaging study of "shell" phenomenon of thoracolumbar fractures after posterior reduction].

Objective: To analyze the imaging characteristics of vertebral "shell" phenomenon of thoracolumbar fractures after posterior reduction and to explore the relationship between vertebral "shell" and fracture healing. Methods: Between January 2013 and December 2015, the clinical data of 116 patients with thoracolumbar fractures treated with posterior pedicle screw-rod system reduction and internal fixation were analyzed retrospectively. There were 72 males and 44 females, aged 22-66 years (mean, 43 years). Injury causes were traffic accident in 24 cases, falling from height in 54 cases, bruise in 38 cases. Fracture segment located at T 11 in 5 cases, T 12 in 38 cases, L 1 in 52 cases, L 2 in 21 cases. There were 51 cases of compressive fracture and 65 cases of burst fracture. The sagittal Cobb angle ranged from 8 to 27°, with an average of 15°. Degree of preoperative spinal compression ranged from 20% to 75%, with an average of 44%. Bone density measurement showed that normal bone mass in 30 cases, bone loss in 40 cases, osteoporosis in 41 cases, and severe osteoporosis in 5 cases. The number, pathological characteristics, and imaging regularity of the vertebral "shell" phenomenon were observed and analyzed by logistic regression. Results: All patients were followed up 11-18 months with an average of 13 months. A total of 72 cases of vertebral "shell" phenomenon mainly located in the vertebral anterior column and the end plate near the weak area (54/72, 75.0%). Most of them were in the irregular shape (50/72, 69.5%). The vertebral fracture line was related to the shape of the vertebral body and the displacement of the vertebral body after reduction. The outcome of the "shell" can be divided into disappeared type, reduced type, and collapse type, the volume of vertebral "shell" and its outcome were the risk factors for vertebral fracture healing. Conclusion: The incidence of vertebral "shell" and nonuion of thoracolumbar fractures after posterior reduction are high. The main influencing factors are vertebral "shell" outcome and size.

Altered functional and effective connectivity in anticorrelated intrinsic networks in children with benign childhood epilepsy with centrotemporal spikes.

There are 2 intrinsic networks in the human brain: the task positive network (TPN) and task negative network (alternately termed the default mode network, DMN) in which inverse correlations have been observed during resting state and event-related functional magnetic resonance imaging (fMRI). The antagonism between the 2 networks might indicate a dynamic interaction in the brain that is associated with development.To evaluate the alterations in the relations of the 2 networks in children with benign childhood epilepsy with centrotemporal spikes (BECTS), resting state fMRI was performed in 17 patients with BECTS and 17 healthy controls. The functional and effective connectivities of 29 nodes in the TPN and DMN were analyzed. Positive functional connectivity (FC) within the networks and negative FC between the 2 networks were observed in both groups.The patients exhibited increased FC within both networks, particularly in the frontoparietal nodes such as the left superior frontal cortex, and enhanced antagonism between the 2 networks, suggesting abnormal functional integration of the nodes of the 2 networks in the patients. Granger causality analysis revealed a significant difference in the degree of outflow to inflow in the left superior frontal cortex and the left ventral occipital lobe.The alterations observed in the combined functional and effective connectivity analyses might indicate an association of an abnormal ability to integrate information between the DMN and TPN and the epileptic neuropathology of BECTS and provide preliminary evidence supporting the occurrence of abnormal development in children with BECTS.