OBJECTIVE:To compare the biomechanical properties of four internal fixation methods in a lower cervical spine injury model using the finite element method. METHODS:Cervical CT data of a 28-year-old healthy adult male were utilized to establish a finite element model of the normal cervical spine and a lower cervical spine three-column injury model. Four internal fixation methods were then applied to the three-column injury model, resulting in four groups:Group A, anterior cervical locked-plate(ACLP) fixation system model(anterior approach);Group B, posterior cervical pedicle screw fixation model (posterior approach);Group C, combined anterior and posterior cervical pedicle screw fixation model; Group D, Novel composite anterior cervical internal fixation model. A 75 N axial compressive load and a 1.0 N·m pure moment were applied to the upper surface of the cervical spine model to simulate flexion, extension, rotation, and lateral bending movements. The intervertebral range of motion(ROM) and stress distribution of the internal fixators under different motion conditions were compared across all models. RESULTS:Compared with the normal model, the reductions in overall intervertebral ROM for each group under flexion, extension, rotation, and lateral bending were as follows:Group A, 24.04°, 23.12°, 6.24°, and 9.06°;Group B, 24.42°, 24.34°, 6.48°, and 9.20°;Group C, 25.43°, 25.29°, 7.17°, and 9.57°;Group D, 24.75°, 25.5°, 6.71°, and 9.12°. The peak stress values of the internal fixators in each group were:Group A, 53.9 MPa, 79.9 MPa, 61.4 MPa, and 80.3 MPa;Group B, 218.3 MPa, 105.4 MPa, 206.6 MPa, and 186.8 MPa;Group C, 40.8 MPa, 97.2 MPa, 47.1 MPa, and 39.4 MPa;Group D, 93.0 MPa, 144.0 MPa, 64.8 MPa, and 106.3 MPa. CONCLUSION:The biomechanical properties of the novel composite anterior cervical internal fixation method are similar to those of the combined anterior-posterior fixation method, and superior to both the anterior cervical ACLP plate-screw fixation and posterior cervical pedicle screw fixation methods.

STUDY DESIGN:This study was to compare the biomechanical properties of 4 internal fixation methods on the lower cervical injury model by finite element method. OBJECTIVE:Using the finite element method to study the biomechanical characteristics of the novel composite anterior cervical spine fixation technique-combining anterior transpedicular screw fixation with a zero-track internal fixation. SUMMARY OF BACKGROUND INFO:Several studies have demonstrated lower cervical 3-column injury is not effective treated by anterior cervical surgery. To the best of our knowledge, few studies has examined the effectiveness of enhanced anterior cervical surgery alone. METHODS:CT data of a healthy 28-year-old male adult were selected to create finite element models of a 3-column injury model of the lower cervical spine. Four internal fixation methods were applied to the lower cervical spine injury model: anterior cervical locking plate model (group A), posterior transpedicular screw fixation model (group B), anterior+posterior transpedicular screw fixation model (group C), and the novel composite anterior cervical spine fixation model (group D). These models were subjected to 75 N axial force and 1.0 Nm to induce various movements. Comparing the range of motion (ROM), vertebral displacement, and stress distribution of the different models under various conditions. RESULTS:Compared with the normal model, in flexion, extension, rotation, and lateral bending, the overall intervertebral mobility of group D demonstrated less ROM, but a slightly larger than group C. In flexion, rotation, and lateral bending, the peak stresses for group D were less than group B. In flexion and extension, the vertebral displacements of C3-6 in group D showed less displacement, but a slightly larger than group C. CONCLUSIONS:The biomechanical characteristics of the new composite anterior cervical fixation method are favorable. LEVEL OF EVIDENCE:Level III.

OBJECTIVE:To investigate the feasibility of mimics software in analyzing a new type of complex anterior cervical fixation -- anterior transpedicular screw fixation+zero notch internal fixation.METHODS:From January 2021 to September 2022, 50 normal pedestrians who underwent cervical spine CT scanning were selected for C1-C7 segment scanning, including 27 males and 23 females, aged from 25 to 65 years old with an average of (46.0 ± 9.0) years old. The dicom format is exported and engraved into the CD, and use the mimics software to perform 3D reconstruction of each segment. A simulated screw is placed on the image according to the critical value of zero notch screw (head and tail angle 44°, internal angle 29°). The position of zero notch screw in each segment is observed to determine the feasibility of anterior transpedicular screw fixation plus zero notch internal fixation.RESULTS:For the upper zero notch screws the three-dimensional images of the cervical spine across all 50 subjects within the C3-C7 segments demonstrated safe position, with no instances of intersection with ATPS. For the lower zero notch screw, in C3-C4 and C4-C5, 4 out of 50 subjects are in the safe position in the three-dimensional images of cervical vertebrae, and 46 cases could achieve secure screw placement when the maximum caudal angle is(32.3±1.9) ° and (36.1±2.2) °, respectively. In C5-C6 and C6-C7 segments, no lower zero notch screws intersected with ATPS, and all screws are in safe positions.CONCLUSION:Lower cervical anterior pedicle screw fixation plus zero notch internal fixation can achieve successful nail placement through the selected entry point and position.

Background: The cervical anterior transpedicular screw (ATPS) fixation technology can provide adequate stability for cervical three-column injuries. However, its high risk of screw insertion and technical complexity have restricted its widespread clinical application. As an improvement over the ATPS technology, the cervical anterior transpedicular root screw (ATPRS) technology has been introduced to reduce the risk associated with screw insertion. This study aims to use finite element analysis (FEA) to investigate the biomechanical characteristics of a cervical spine model after using the novel ATPRS intervertebral fusion system, providing insights into its application and potential refinement.Methods: A finite element (FE) model of the C3-C7 lower cervical spine was established and validated. After two-level (C4-C6) anterior cervical discectomy and fusion (ACDF) surgery, FE models were constructed for the anterior cervical locked-plate (ACLP) internal fixation, the ATPS internal fixation, and the novel ATPRS intervertebral fusion system. These models were subjected to 75N axial force and 1.0 Nm to induce various movements. The range of motion (ROM) of the surgical segments (C4-C6), maximum stress on the internal fixation systems, and maximum stress on the adjacent intervertebral discs were tested and recorded.Results: All three internal fixation methods effectively reduced the ROM of the surgical segments. The ATPRS model demonstrated the smallest ROM during flexion, extension, and rotation, but a slightly larger ROM during lateral bending. Additionally, the maximum bone-screw interface stresses for the ATPRS model during flexion, extension, lateral bending, and axial rotation were 32.69, 64.24, 44.07, 35.89 MPa, which were lower than those of the ACLP and ATPS models. Similarly, the maximum stresses on the adjacent intervertebral discs in the ATPRS model during flexion, extension, lateral bending, and axial rotation consistently remained lower than those in the ACLP and ATPS models. However, the maximum stresses on the cage and the upper endplate of the ATPRS model were generally higher.Conclusion: Although the novel ATPRS intervertebral fusion system generally had greater endplate stress than ACLP and ATPS, it can better stabilize cervical three-column injuries and might reduce the occurrence of adjacent segment degeneration (ASD). Furthermore, further studies and improvements are necessary for the ATPRS intervertebral fusion system.

OBJECTIVES: To establish a predictive model to evaluate the risk of adjacent vertebral refracture (VRF) after percutaneous kyphoplasty (PKP) for osteoporotic vertebral compression fracture (OVCF) based on perioperative imaging data. METHODS: This study was a retrospective cohort study which established a predictive model of VRF after PKP for OVCF. Patients who underwent PKP for OVCF in our hospital between January 2018 and December 2020 were enrolled and divided into a refracture group and normal group. Perioperative imaging data including preoperative bone mineral density (BMD), fatty infiltration (FI%) of paravertebral muscle, sagittal parameters of the spine and pelvis, and recovery rate of vertebral height were collected. The prediction model is obtained by multifactor logistic regression analysis. RESULTS: A total of 242 patients were included, including 23 cases in the VRF group and 219 cases in the normal group. There were statistical differences in BMD, FI %, recovery rate of vertebral height, and sagittal imbalance between the 2 groups. Receiver operating characteristic curve analysis of continuous variables showed that BMD 5-2.80, FI% >= 40%, and recovery rate of vertebral height >= 10% were the cutoff values. Logistic regression analysis showed that BMD 5-2.80, FI% >= 40%, and sagittal imbalance were independent risk factors for VRF. The area under the curve according to the predicted probability was 0.85 (P< P < 0.05). After simplifying the model, the total point of the model was 7 points, with a cutoff value of 5 points. CONCLUSIONS: The prediction model obtained in this study can predict refracture after PKP for OVCF early and effectively. It has an excellent predictive effect which is suitable for clinicians.

OBJECTIVES: The aim of this systematic review was to evaluate the risk factors for cage subsidence (CS) after oblique lumbar interbody fusion (OLIF). METHODS: The cohort and case-control studies which reporting potential risk factors for CS following OLIF were searched in PubMed, Embase, and Web of Science from database inception to June 17, 2023. Two researchers independently screened the literature, extracted data, and evaluated the quality of the literature according to the Newcastle Ottawa Scale. RevMan5.3 software was used for Meta analysis. x(2) statistics and I-2 statistics were used to evaluate heterogeneity, and the analysis results were represented by forest plots. RESULTS: A total of 8 studies with 280 cases of CS from 832 patients whonderwent OLIF met the inclusion criteria. Elderly patients over 60 years old (odds ratio [OR] 2.44, 95% CI 1.38-4.31, P = 0.002), osteoporosis (OR 4.18, 95% CI 2.30-7.61, P = 0.002), end plate injury (OR 5.72, 95% CI 2.32-14.11, P = 0.0002), and overdistraction of intervertebral space (OR 1.67, 95% CI 1.3 2-2.11, P < 0.0001) were potential risk factors, while Hounsfield units value of the vertebral body (OR 0.97, 95% CI 0.95-1.00, P = 0.02) is a protective factor. The number of operative segments did not increase the risk of CS. CONCLUSIONS: Older age, osteoporosis, endplate injury, and overdistraction of the intervertebral space may increase the risk of CS after OLIF. Although the incidence rate of CS is low, implementing effective preventions is a priority for clinicians based on these risk factors.

Objective:To explore the best screw path and safe screw path angle range of anterior transpedicular screws in the lower cervical spine based on 3D CT imaging by screw axial fluoroscopy.Methods:Fifty cervical CT data integral from volunteers from June 2019 to July 2020 were selected from Ningbo No. 6 Hospital and were confirmed to have no obvious defect. Among the cases, 24 were males and 26 were females aged 22-52 (31.9±5.4) years. The original data of CT scanning were imported into Mimics software in DICOM format for 3D reconstruction. On the coronal and sagittal images of the reconstructed 3D CT images, the leading edge of the C 3-7 vertebral body was divided into four parts. The MEDcap module was used for simulated screw placement in the right pedicle, and the best screw path was obtained by screw axial fluoroscopy. The best screw insertion area, the angle between the horizontal screw and the posterior edge of the vertebral body, and the angle between the sagittal screw and the anterior edge of the vertebral body were recorded. Then, the head of the screw was moved to obtain the maximum head inclination, tail inclination, inward inclination, and outward inclination of the safety screw path. The angles formed by the best screw path with the maximum head inclination, tail inclination, inward inclination, and outward inclination safety screw path were denoted respectively. The data of males and females were compared by independent sample t-test. Results:In 50 patiens, the best screw entry area in sagittal plane was zone 2 at C 3-5 (72%[36/50], 68%[34/50], 78%[39/50], respectively), zone 3 at C 6-7 (70%[35/50], 76%[38/50], respectively), and the best screw entry area in horizontal plane was zone 3 at C 3-5 (90%[45/50], 82%[41/50], 88%[44/50], respectively), zone 2 at C 6-7 (80%[40/50], 84%[42/50], respectively). The best angles for screw insertion in the sagittal and horizontal positions were 78.3°-69.9° and 46.7°-50.1° for males and 76.1°-64.9° and 44.7°-48.7° for females, respectively. The sagittal and horizontal angles between men and women had significant differences (all P values<0.001). The maximum safe angles of head inclination, tail inclination, inward inclination, and outward inclination were 8.7°-14.2°, 8.9°-13.1°, 5.4°-8.5°, and 5.3°-8.4° for males and 7.5°-13.4°, 8.4°-12.8°, 4.8°-8.0°, and 4.7°-7.8° for females, respectively. The difference was statistically significant (all P values<0.05). Conclusion:The optimal screw path and safe screw path angle of ATPS in lower cervical are obtained by screw axial fluoroscopy combined with CT three-dimensioal software to simulate screw placement and measurement, which provides imaging anatomical data support for the safety of screw placement.

Abstract Objective This study aims to investigate the feasibility of the anterior transpedicular root screw (ATPRS) intervertebral fusion system for the cervical spine and provide a basis for the design of the ATPRS intervertebral fusion system. Methods A total of 60 healthy adult cervical spine CT images examined from our hospital were selected, including 30 males and 30 females, with an average age of 39.6 ± 4.8 years. The image data was imported into Mimics 21.0 software in DICOM format for 3D model reconstruction. Simulated screw insertion was performed on both sides of the midline of the intervertebral space. The entry point (P1) was determined when the upper and lower screw paths did not overlap. When the screw was tangent to the medial edge of the Luschka joint, the insertion point was determined as the entry point (P2). Measurements were taken and recorded for the following parameters: distance from the screw entry point to the midline of the intervertebral space (DPM), the simulated screw length, inclination angle, cranial/caudal tilted angle, the anterior–posterior (AP) and mediolateral (ML) diameters of the cervical intervertebral space, the heights of the anterior, middle, and posterior edges of the cervical intervertebral space, and the curvature diameter of the lower end plate of the cervical vertebral body. Statistical analysis was performed on the measurement results. Results The screw entry area (P1P2) showed an increasing trend from C3-C7 in both male (2.92–6.08 mm) and female (2.32–5.12 mm) groups. There were statistical differences between men and women at the same level (P < 0.05). The average screw length of men and women was greater than 20 mm, and the upper and lower screw lengths showed an increasing trend from C3 to C7. In the area where screws could be inserted, the range of screw inclination was as follows: male group upper screw (47.73–66.76°), lower screw (48.05–65.35°); female group upper screw (49.15–65.66°) and lower screw (49.42–63.29°); The range of cranial/caudal tilted angle of the screw was as follows: male group upper screw (32.06–39.56°), lower screw (29.12–36.95°); female group upper screw (30.97–38.92°) and lower screw (27.29–37.20°). The anterior–posterior diameter and mediolateral diameter of the cervical intervertebral space showed an increasing trend from C3 to C7 in both male and female groups. The middle height (MH) of the cervical intervertebral space was greater than the anterior edge height (AH) and posterior edge height (PD), with statistical differences (P < 0.05). Conclusions Through the study of CT images of the cervical spine, it was determined that the ATPRS intervertebral fusion system has a feasible area for screw insertion in the cervical intervertebral space.

Abstract Objective: Exploring the safe range of anterior transpedicular screw (ATPS) in the lower cervical spine. Methods: Fifty healthy adult cervical spine CT imaging data were selected from our institution for this study. The image data was imported into Mimics 21.0 software in DICOM format for 3D model reconstruction. Then, using the intersection of the pedicle axis and the anterior wall of the vertebral body as the screw entry point, a 3.5 mm simulated screw was inserted. The simulated screw was rotated and moved with the intersection acting as its center. On the horizontal view, the included angle (α) between the simulated screw axis and the mid-sagittal plane, the width of the pedicle, and the distance between the transverse point and the mid-sagittal plane at the anterior vertebral body wall were measured from C3 to C7; On the sagittal view, the included angle (β) between the simulated screw axis and the plane of the anterior vertebral body wall, the height of pedicle, and the distance between the sagittal intersection point and the upper endplate were measured C3 to C7. Results: No matter in the transverse or sagittal planes, C7 had the largest average safety range, while C3 was the smallest. The average safety range of screw placement on the transverse plane increased from C3 to C7, ranging from 5.25°to 9.43°, of which C7 was the largest (9.43°) and C3 was the smallest (5.25°). The average safety range of screw placement on the sagittal plane showed a trend of first increasing, then decreasing, and then increasing, ranging from 12.57° to 14.70°, of which C7 was the largest (14.70°), and C3 was the smallest (12.57°). There was no statistical difference between the left and right pedicles of the same cervical level (P>0.05). Conclusions: When the entry point was determined, there was a certain safety range for ATPS in the lower cervical spine. Those are helpful for the clinical application of ATPS technology. However, the individual anatomy of the cervical spine is relatively different, and sufficient preoperative preparations should still be made to ensure the safety and accuracy of screw placement.