MiR-223 enhances lipophagy by suppressing CTSB in microglia following lysolecithin-induced demyelination in mice.

BACKGROUND: Lipid droplet (LD)-laden microglia is a key pathological hallmark of multiple sclerosis. The recent discovery of this novel microglial subtype, lipid-droplet-accumulating microglia (LDAM), is notable for increased inflammatory factor secretion and diminished phagocytic capability. Lipophagy, the autophagy-mediated selective degradation of LDs, plays a critical role in this context. This study investigated the involvement of microRNAs (miRNAs) in lipophagy during demyelinating diseases, assessed their capacity to modulate LDAM subtypes, and elucidated the potential underlying mechanisms involved. METHODS: C57BL/6 mice were used for in vivo experiments. Two weeks post demyelination induction at cervical level 4 (C4), histological assessments and confocal imaging were performed to examine LD accumulation in microglia within the lesion site. Autophagic changes were observed using transmission electron microscopy. miRNA and mRNA multi-omics analyses identified differentially expressed miRNAs and mRNAs under demyelinating conditions and the related autophagy target genes. The role of miR-223 in lipophagy under these conditions was specifically explored. In vitro studies, including miR-223 upregulation in BV2 cells via lentiviral infection, validated the bioinformatics findings. Immunofluorescence staining was used to measure LD accumulation, autophagy levels, target gene expression, and inflammatory mediator levels to elucidate the mechanisms of action of miR-223 in LDAM. RESULTS: Oil Red O staining and confocal imaging revealed substantial LD accumulation in the demyelinated spinal cord. Transmission electron microscopy revealed increased numbers of autophagic vacuoles at the injury site. Multi-omics analysis revealed miR-223 as a crucial regulatory gene in lipophagy during demyelination. It was identified that cathepsin B (CTSB) targets miR-223 in autophagy to integrate miRNA, mRNA, and autophagy gene databases. In vitro, miR-223 upregulation suppressed CTSB expression in BV2 cells, augmented autophagy, alleviated LD accumulation, and decreased the expression of the inflammatory mediator IL-1ß. CONCLUSION: These findings indicate that miR-223 plays a pivotal role in lipophagy under demyelinating conditions. By inhibiting CTSB, miR-223 promotes selective LD degradation, thereby reducing the lipid burden and inflammatory phenotype in LDAM. This study broadens the understanding of the molecular mechanisms of lipophagy and proposes lipophagy induction as a potential therapeutic approach to mitigate inflammatory responses in demyelinating diseases.

Proteomics and bioinformatics reveal insights into neuroinflammation in the acute to subacute phases in rat models of spinal cord contusion injury.

Neuroinflammation is recognized as a hallmark of spinal cord injury (SCI). Although neuroinflammation is an important pathogenic factor that leads to secondary injuries after SCI, neuroprotective anti-inflammatory treatments remain ineffective in the management of SCI. Moreover, the molecular signatures involved in the pathophysiological changes that occur during the course of SCI remain ambiguous. The current study investigated the proteins and pathways involved in C5 spinal cord hemi-contusion injury using a rat model by means of 4-D label-free proteomic analysis. Furthermore, two Gene Expression Omnibus (GEO) transcriptomic datasets, Western blot assays, and immunofluorescent staining were used to validate the expression levels and localization of dysregulated proteins. The present study observed that the rat models of SCI were associated with the enrichment of proteins related to the complement and coagulation cascades, cholesterol metabolism, and lysosome pathway throughout the acute and subacute phases of injury. Intriguingly, the current study also observed that 75 genes were significantly altered in both the GEO datasets, including ANXA1, C1QC, CTSZ, GM2A, GPNMB, and PYCARD. Further temporal clustering analysis revealed that the continuously upregulated protein cluster was associated with immune response, lipid regulation, lysosome pathway, and myeloid cells. Additionally, five proteins were further validated by means of Western blot assays and the immunofluorescent staining showed that these proteins coexisted with the F4/80+ reactive microglia and infiltrating macrophages. In conclusion, the proteomic data pertaining to the current study indicate the notable proteins and pathways that may be novel therapeutic targets for the treatment of SCI.

A Retrospective Study of the Effect of Spinopelvic Parameters on Fatty Infiltration in Paraspinal Muscles in Patients With Lumbar Spondylolisthesis.

OBJECTIVE: The effect on fat infiltration (FI) of paraspinal muscles in degenerative lumbar spinal diseases has been demonstrated except for spinopelvic parameters. The present study is to identify the effect of spinopelvic parameters on FI of paraspinal muscle (PSM) and psoas major muscle (PMM) in patients with degenerative lumbar spondylolisthesis. METHODS: A single-center, retrospective cross-sectional study of 160 patients with degenerative lumbar spondylolisthesis (DLS) and lumbar stenosis (LSS) who had lateral full-spine x-ray and lumbar spine magnetic resonance imaging was conducted. PSM and PMM FIs were defined as the ratio of fat to its muscle cross-sectional area. The FIs were compared among patients with different pelvic tilt (PT) and pelvic incidence (PI), respectively. RESULTS: The PSM FI correlated significantly with pelvic parameters in DLS patients, but not in LSS patients. The PSM FI in pelvic retroversion (PT > 25°) was 0.54 ± 0.13, which was significantly higher in DLS patients than in normal pelvis (0.41 ± 0.14) and pelvic anteversion (PT < 5°) (0.34 ± 0.12). The PSM FI of DLS patients with large PI ( > 60°) was 0.50 ± 0.13, which was higher than those with small ( < 45°) and normal PI (0.37 ± 0.11 and 0.36 ± 0.13). However, the PSM FI of LSS patients didn't change significantly with PT or PI. Moreover, the PMM FI was about 0.10-0.15, which was significantly lower than the PSM FI, and changed with PT and PI in a similar way of PSM FI with much less in magnitude. CONCLUSION: FI of the PSMs increased with greater pelvic retroversion or larger pelvic incidence in DLS patients, but not in LSS patients.

Ipsilateral Fixation and Reconstruction of the Cervical Spine after Resection of a Dumbbell Tumor Via a Unilateral Posterior Approach: A Case Report and Biomechanical Study.

OBJECTIVE: There is lack of an internal fixation following resection of a dumbbell tumor by hemi-laminectomy and facetectomy that achieves adequate stability with less trauma. Unilateral fixation and reconstruction (unilateral pedicle screw and contralateral lamina screw fixation combined with lateral mass reconstruction, UPS + CLS + LM) may be an ideal technique to address this problem. A biomechanical comparison and a case report were designed to evaluate its spinal stability and clinical effect. METHODS: Seven fresh-frozen human subcervical specimens were used for the biomechanical testing. The conditions tested were: (1) intact; (2) injured (single-level hemi-laminectomy and facetectomy); (3) unilateral pedicle screw (UPS) fixation; (4) UPS fixation combined with lateral mass (LM) reconstruction (UPS + LM); (5) UPS fixation and contralateral lamina screw fixation (UPS + CLS); (6) UPS + CLS + LM; (7) UPS fixation and contralateral transarticular screw fixation (UPS + CTAS); (8) bilateral pedicle screw (BPS) fixation. Range of motion (ROM) and neutral zone (NZ) were obtained at C5-C7 segment under eight conditions. In addition, we report the case of a patient with a C7-T1 dumbbell tumor that was treated by UPS + CLS + LM technique. RESULTS: Except left/right lateral bending and right axial rotation (all, p < 0.05), ROM of UPS + CLS + LM condition in other directions was similar to that of BPS condition (all, p > 0.05). There was no significant difference between UPS + CLS + LM and the UPS + CTAS condition in other directions of ROM (all, p > 0.05), except in left/right axial rotation (both, p < 0.05). Compared to UPS + CLS condition, left/right lateral bending ROM of UPS + CLS + LM condition were significantly reduced (both, p < 0.05). UPS + CLS + LM condition significantly reduced ROM in all directions compared to UPS and UPS + LM condition (all, p < 0.05). Similarly, except lateral bending (p < 0.05), there was no difference in NZ in other directions between UPS + CLS + LM and BPS condition (both, p > 0.05). There was no significant difference between UPS + CLS + LM and UPS + CTAS condition in NZ in all directions (all, p > 0.05). Axial rotation NZ of UPS + CLS + LM condition was significantly reduced compared to UPS + CLS condition (p < 0.05). Compared to UPS and UPS + LM condition, NZ of UPS + CLS + LM condition was significantly reduced in all directions (all, p < 0.05). The patient's imaging examination at 3 months postoperatively indicated that the internal fixation did not move and the graft bone was seen with fusion. CONCLUSION: After resection of a dumbbell tumor in the cervical spine, UPS + CLS + LM technique is a reliable internal fixation method to provide sufficient immediate stability and promote postoperative bone fusion.

Disc degeneration contributes to the denser bone in the subendplate but not in the vertebral body in patients with lumbar spinal stenosis or disc herniation.

BACKGROUND CONTEXT: It is commonly believed that decreased bone quality would lead to endplate degeneration and arthritic changes in the facet joints, and thus accelerated disc degeneration (DD). However, some more detailed studies of vertebral bone structure have found that bone mineral density (BMD) in the vertebral body is increased rather than decreased in moderate or greater disc degeneration. The relationship between BMD and DD still needs further study. MRI-based vertebral bone quality scores have been shown to be effective in reflecting BMD, rendering a new way to evaluate the changes of vertebral body bone with DD using MRI alone. PURPOSE: To evaluate MRI-based vertebral bone quality and Pfirrmann grades in patients with lumbar spinal stenosis or disc herniation, and to identify if DD is associated with denser bone around the endplate. STUDY DESIGN/SETTING: A single-center, retrospective cohort study. PATIENT SAMPLE: A total of 130 patients with lumbar disc herniation and lumbar spinal stenosis from January 2019 to November 2020 who had a complete dual-energy X-ray absorptiometry scan and noncontrast lumbosacral spine MRI data. OUTCOME MEASURES: The vertebral bone quality score (VBQ) and sub-endplate bone quality score (EBQ) was calculated as a ratio of the signal intensity of the vertebral bodies and sub-endplate regions to the signal intensity of the cerebrospinal fluid at L3 on the mid-sagittal T1-weighted MRI images, respectively. The Pfirrmann grades of the lumbar discs were assessed as well. METHODS: The age, gender, body mass index, and T-score of the lumbar spine of the patients were collected. The degeneration grades of the lumbar discs were evaluated according to the Pfirrmann classification. VBQ and EBQ were measured through T1-weighted lumbar MRI. The VBQ and EBQ scores were compared between cranial and caudal sides. The correlation between MRI-based bone quality and DD was calculated. A linear regression model was used to examine the association between DD and adjacent EBQ and VBQ. RESULTS: This study included 569 lumbar segments from 130 inpatients. Cranial and caudal EBQ decreased with the increase of the Pfirrmann grade. The discs with Pfirrmann grade 5 had significantly lower caudal EBQ than the discs with Pfirrmann grades 2, 3, and 4. In the osteoporosis patients, the Pfirrmann grades negatively correlated both with the cranial EBQ and caudal EBQ. Pfirrmann grade greater than 4 was an independent contributor to the cranial EBQ, whereas greater than 3 was an independent contributor to the caudal EBQ. CONCLUSIONS: Disc degeneration grades correlated with the EBQ but not with the VBQ. In patients with lumbar spinal stenosis or disc herniation, DD contributes to the denser bone in the sub-endplate, but not in the whole vertebral body.

Medial Buttress Plate and Allograft Bone-Assisted Cannulated Screw Fixation for Unstable Femoral Neck Fracture with Posteromedial Comminution: A Retrospective Controlled Study.

OBJECTIVE: To investigate the outcomes of open reduction and internal fixation combined with medial buttress plate (MBP) and allograft bone-assisted cannulated screw (CS) fixation for patients with unstable femoral neck fracture with comminuted posteromedial cortex. METHODS: In a retrospective study of patients operated on for unstable femoral neck fractures with comminuted posteromedial cortex from March 2016 to August 2020, the clinical and radiographic outcomes of 48 patients treated with CS + MBP were compared with the outcomes of 54 patients treated with CS only. All patients in the CS + MBP group were fixed by three CS and MBP (one-third tubular plates or reconstructive plates) with bone allografts. The surgery-related outcomes and complications were evaluated, including operative time, blood loss, union time, femoral head necrosis, femoral neck shortening, and other complications after the operation. The Harris score was evaluated at 12 months after the operation. RESULTS: All patients were followed up for 12-40 months. The average age of patients in the CS-only group (54 cases, 22 females) and CS + MBP group (48 cases, 20 females) was 48.46 ± 7.26 and 48.73 ± 6.38 years, respectively. More intraoperative blood loss was observed in the CS + MBP group than that of patients in CS-only group (153.45 ± 64.27 vs 21.86 ± 18.19 ml, t = 4.058, P = 0.015). The average operative time for patients in the CS + MBP group (75.35 ± 27.67 min) was almost double than that of patients in the CS-only group (36.87 ± 15.39 min) (t = 2.455, P < 0.001). The Garden alignment index of patients treated by CS + MBP from type I to type IV was 79%, 19%, 2%, and 0%, respectively. On the contrary, they were 31%, 43%, 24% and 2% for those in the CS-only group, respectively. The average healing times for the CS-only and CS + MBP groups were 4.34 ± 1.46 and 3.65 ± 1.85 months (t = 1.650, P = 0.102), respectively. Femoral neck shortening was better in the CS + MBP group (1.40 ± 1.73 mm, 9/19) than that in the CS-only group (4.33 ± 3.32 mm, 24/44). Significantly higher hip function was found in the CS + MBP group (85.60 ± 4.36 vs 82.47 ± 6.33, t = 1.899, P = 0.06). There was no statistical difference between femoral head necrosis (4% vs 11%, χ2  = 1.695, P = 0.193) and nonunion (6% vs 9%, χ2  = 0.318, P = 0.719). CONCLUSION: For unstable femoral neck fractures with comminuted posteromedial cortex, additional MBP combined with bone allografts showed better reduction quality and neck length control than CS fixation only, with longer operative time and more blood loss.

Cervical Alignment of Patients with Basilar Invagination: A Radiological Study.

OBJECTIVE: To investigate the cervical alignment and the relative range of motion (ROM) in patients with basilar invagination (BI). METHODS: A total of 40 BI cases (38.1 years old ± 17.9 years old, 19 male and 21 female) and 80 asymptomatic individuals (33.8 years old ± 10.8 years old, 40 male and 40 female) were included. The Skull-C2 /Skull-BV, Skull-C7 , C2 -C7 /BV-C7 wall angles, C0 -C2 /C0 -BV, C0 -C7 , C1 -C7 , and C2 -C7 /BV-C7 angles were measured in dynamic X-ray images (including neutral, extension, and flexion positions). Correlation between the upper and lower cervical curvatures were analyzed. The total, extension, and flexion ROMs of these angles were calculated, respectively. RESULTS: The BI patients had a smaller C0 -C2 /C0 -BV angle (18.2° ± 16.4° vs 30.9° ± 9.3°), but larger C2 -C7 /BV-C7 (32.2° ± 16.1° vs 19.4° ± 10.6°) and C2 -C7 /BV-C7 wall angles (37.8° ± 17.2° vs 23.6° ± 10.2°) than the control group in neutral position. The upper and lower curvatures correlated negatively in neutral (r = -0.371), extension (r = -0.429), and flexion (r = -0.648) positions among BI patients, as well as in extension position (r = -0.317) among control group. The BI patients presented smaller total ROMs in Skull-C2 /Skull-BV (12.3° ± 16.6° vs 19.7° ± 10.9°), C0 -C2 /C0 -BV (8.1° ± 11.1° vs 17.6° ± 10.5°), and C0 -C7 angles (57.8° ± 14.2° vs 78.3° ± 17.9°), but a larger total ROM in C2 -C7 /BV-C7 wall angle (52.8° ± 13.9° vs 27.0° ± 16.1°) than the control group. The BI patients also presented smaller extension ROMs in Skull-C2 /Skull-BV (6.9° ± 9.4° vs 12.5° ± 9.3°), Skull-C7 (24.5° ± 10.9° vs 30.7° ± 12.5°), and C0 -C2 /C0 -BV angles (4.4° ± 7.8° vs 9.9° ± 8.6°) than the control group. Moreover, the BI patients showed smaller absolute values of flexion ROMs in Skull-C2 /Skull-BV (-5.2° ± 9.4° vs -7.3° ± 8.0°), C0 -C2 /C0 -BV (-3.2° ± 8.8° vs -7.7° ± 8.7°), and C0 -C7 angles (-33.2° ± 13.0° vs -52.8° ± 19.2°), but a larger absolute value of flexion ROM in C2 -C7 /BV-C7 wall angle (-33.9° ± 14.8° vs -8.2° ± 15.1°). CONCLUSION: The cervical spine was stiffer in BI patients than the asymptomatic individuals, especially in the upper cervical curvature. The negative correlation between upper and lower cervical curvatures was more obvious in BI patients.

Bioinformatics analysis identified apolipoprotein E as a hub gene regulating neuroinflammation in macrophages and microglia following spinal cord injury.

Macrophages and microglia play important roles in chronic neuroinflammation following spinal cord injury (SCI). Although macrophages and microglia have similar functions, their phagocytic and homeostatic abilities differ. It is difficult to distinguish between these two populations in vivo, but single-cell analysis can improve our understanding of their identity and heterogeneity. We conducted bioinformatics analysis of the single-cell RNA sequencing dataset GSE159638, identifying apolipoprotein E (APOE) as a hub gene in both macrophages and microglia in the subacute and chronic phases of SCI. We then validated these transcriptomic changes in a mouse model of cervical spinal cord hemi-contusion and observed myelin uptake, lipid droplets, and lysosome accumulation in macrophages and microglia following SCI. Finally, we observed that knocking out APOE aggravated neurological dysfunction, increased neuroinflammation, and exacerbated the loss of white matter. Targeting APOE and the related cholesterol efflux represents a promising strategy for reducing neuroinflammation and promoting recovery following SCI.

Utility of somatosensory and motor-evoked potentials in reflecting gross and fine motor functions after unilateral cervical spinal cord contusion injury.

Fine motor skills are thought to rely on the integrity of ascending sensory pathways in the spinal dorsal column as well as descending motor pathways that have a neocortical origin. However, the neurophysiological processes underlying communication between the somatosensory and motor pathways that regulate fine motor skills during spontaneous recovery after spinal cord contusion injury remain unclear. Here, we established a rat model of cervical hemicontusive injury using C5 laminectomy followed by contusional displacement of 1.2 mm (mild injury) or 2.0 mm (severe injury) to the C5 spinal cord. Electrophysiological recordings were performed on the brachial muscles up to 12 weeks after injury to investigate the mechanisms by which spinal cord pathways participate in motor function. After spinal cord contusion injury, the amplitudes of somatosensory and motor-evoked potentials were reduced, and the latencies were increased. The forelimb open field locomotion test, grooming test, rearing test and Montoya staircase test revealed improvement in functions. With increasing time after injury, the amplitudes of somatosensory and motor-evoked potentials in rats with mild spinal cord injury increased gradually, and the latencies gradually shortened. In comparison, the recovery times of somatosensory and motor-evoked potential amplitudes and latencies were longer, and the recovery of motor function was delayed in rats with severe spinal cord injury. Correlation analysis revealed that somatosensory-evoked potential and motor-evoked potential parameters were correlated with gross and fine motor function in rats with mild spinal cord contusion injury. In contrast, only somatosensory-evoked potential amplitude was correlated with fine motor skills in rats with severe spinal cord injury. Our results show that changes in both somatosensory and motor-evoked potentials can reflect the changes in gross and fine motor functions after mild spinal cord contusion injury, and that the change in somatosensory-evoked potential amplitude can also reflect the change in fine motor function after severe spinal cord contusion injury. This study was approved by the Animal Ethics Committee of Nanfang Hospital, Southern Medical University, China (approval No. NFYY-2017-67) on June 11, 2017.

Genome-Wide Expression Difference of MicroRNAs in Basal Cell Carcinoma.

Distinct expression of the miRNAs has rarely been explored in basal cell carcinoma (BCC) of skin, and the regulatory role of miRNAs in BCC development remains quite opaque. Here, we collected control tissues from adjacent noncancerous skin (n = 15; control group) and tissues at tumor centers from patients with cheek BCC (n = 15; BCC group) using punch biopsies. After six small RNA sequencing- (sRNA-seq-) based miRNA expression profiles were generated for both BCC and controls, including three biological replicates, we conducted comparative analysis on the sRNA-seq dataset, discovering 181 differentially expressed miRNAs (DEMs) out of the 1,873 miRNAs in BCCs. In order to validate the sRNA-seq data, expression of 15 randomly selected DEMs was measured using the TaqMan probe-based quantitative real-time PCR. Functional analysis of predicted target genes of DEMs in BCCs shows that these miRNAs are primarily involved in various types of cancers, immune response, epithelial growth, and morphogenesis, as well as energy production and metabolism, indicating that BCC development is caused, at least in part, by changes in miRNA regulation for biological and disease processes. In particular, the "basal cell carcinoma pathways" were found to be enriched by predicted DEM targets, and regulatory relationships between DEMs and their targeted genes in this pathway were further uncovered. These results revealed the association between BCCs and abundant miRNA molecules that regulate target genes, functional modules, and signaling pathways in carcinogenesis.

A preliminary study of a novel robotic system for pedicle screw fixation: A randomised controlled trial.

BACKGROUND AND OBJECTIVE: Existing orthopaedic robotic systems are almost restricted to provide guidance for trajectory direction. In the present study, a novel spinal robotic system with automatic drilling power was introduced. The aim of this study is to evaluate the feasibility and safety in pedicle screw â€‹insertion of posterior lumbar interbody fusion assisted by this novel robotic system. METHODS AND MATERIALS: A randomised controlled trial was conducted for 17 participants who were required posterior lumbar interbody fusion process. Seven (3 M/4 F) were randomly assigned to the robot-assisted group (RA group), and the other ten (4 M/6 F) were assigned to the conventional technique group (FH group). A novel robotic system was used in the RA group. All measurements were based on postoperative computed tomography (CT) data. Accuracy of screw insertion was determined using the Gertzbein and Robbins Scale. Precision was measured by the entry point deviation distance and the trajectory rotation. Other variables included operation time, radiation time, length of stay, and screw-related complications. RESULT: A total of 82 pedicle screws were placed in the 17 participants. In the RA group, 90.6% of screws placed were Grade A, and 9.4% were Grade B. In the FH group, 78.0% of screws were Grade A, 20.0% were Grade B, and 2.0% were Grade C. No statistical difference was found in the operation time, radiation time per case, and length of stay between both groups. The radiation time per screw is significantly lower in the RA group. No screw-related complications or revision occurred in the present study. CONCLUSION: The outcome of screw accuracy of this robotic system was comparable with that of experienced surgeons, and no screw-related complication was found in the RA group during hospitalisation. In addition, radiation time per screw in the robotic group was significantly lower than that in the conventional group, which shows the potential to reduce radiation exposure of pedicle screw fixation assisted by this robotic system. TRANSLATIONAL POTENTIAL: Our study shows that pedicle screw fixation assisted by "Orthbot" system is accurate and safe. It is concluded that this novel robotic system offers a new option for internal implantation in spine surgery.

Biomechanical evaluation of a dynamic pedicle screw fixation device.

BACKGROUND: Recent innovations in dynamic devices have promised a reduction in stress shielding, protection of adjacent segment degeneration, and decreased implant failure. However, there have been few studies comparing the biomechanical properties of a rigid device in comparison to a dynamic posterior fixation device. The purpose of this study was to compare the immediate stability of a new dynamic pedicle screw fixation device with an equivalent rigid device. METHODS: Six thoracolumbar cadaver spines (T10-L4) were fixed in a biomechanical testing frame. Pure moments of 10Nm were loaded in six directions: flexion, extension, right and left lateral bending, and right and left axial rotation. For each spine, four different stages were tested: intact, destabilization of the middle segment, fixation with the dynamic device, and fixation with the rigid device. Ranges of motion were measured using stereophotogrammetry. The specimens with each device were then subjected to flexion-compression loading for five cycles on a MTS 858 Universal Testing Machine. The average stiffness of the last three cycles was recorded. FINDINGS: Both dynamic and rigid devices were found to provide stability for the injured segment in flexion-extension and lateral bending. In axial rotation, the devices could restore the stability to levels similar to those in an intact spine. Results also indicated a slight increase in range of motion in flexion-extension and significant reduction in stiffness of flexion-compression with the dynamic device (P < 0.01), in comparison to the rigid device. INTERPRETATION: The dynamic device offers a system that may alter favorably the movement and load transmission of a spinal motion segment without sacrificing construct stability.

Cortical bone trajectory screws for the middle-upper thorax: An anatomico-radiological study.

To quantify the reference data concerning the morphometrics of the middle-upper thorax to guide the placement of cortical bone trajectory (CBT) screws.Eighty patients were studied on computed tomography (CT) scans. The reference anatomical parameters were measured. Next, 20 cadaveric specimens were implanted with CBT screws based on CT measurements. These specimens were then judged directly from the cadaveric vertebrae and X-ray.The maximum length of the trajectory, the maximum diameter, and the cephaled angle exhibited a slight increase trend while the transverse and sagittal angles of the pedicle tended to decrease from T3 to T8. We recommend that the width of CBT screw for middle-upper thoracic spine is 5.0 mm, the length is 25 to 35 mm. The cadaveric anatomical study revealed that 5/240 screws penetrated in the medial or lateral areas, 5/240 screws penetrated in the superior or inferior pedicle wall, and 2/240 screws did not fit into the superior endplate of the pedicle.The CBT screws are safe for the middle-upper thorax. This study provides a theoretical basis for clinical surgery.

Comparison of Cervical Spine Anatomy in Calves, Pigs and Humans.

BACKGROUND CONTEXT: Animals are commonly used to model the human spine for in vitro and in vivo experiments. Many studies have investigated similarities and differences between animals and humans in the lumbar and thoracic vertebrae. However, a quantitative anatomic comparison of calf, pig, and human cervical spines has not been reported. PURPOSE: To compare fundamental structural similarities and differences in vertebral bodies from the cervical spines of commonly used experimental animal models and humans. STUDY DESIGN: Anatomical morphometric analysis was performed on cervical vertebra specimens harvested from humans and two common large animals (i.e., calves and pigs). METHODS: Multiple morphometric parameters were directly measured from cervical spine specimens of twelve pigs, twelve calves and twelve human adult cadavers. The following anatomical parameters were measured: vertebral body width (VBW), vertebral body depth (VBD), vertebral body height (VBH), spinal canal width (SCW), spinal canal depth (SCD), pedicle width (PW), pedicle depth (PD), pedicle inclination (PI), dens width (DW), dens depth (DD), total vertebral width (TVW), and total vertebral depth (TVD). RESULTS: The atlantoaxial (C1-2) joint in pigs is similar to that in humans and could serve as a human substitute. The pig cervical spine is highly similar to the human cervical spine, except for two large transverse processes in the anterior regions ofC4-C6. The width and depth of the calf odontoid process were larger than those in humans. VBW and VBD of calf cervical vertebrae were larger than those in humans, but the spinal canal was smaller. Calf C7 was relatively similar to human C7, thus, it may be a good substitute. CONCLUSION: Pig cervical vertebrae were more suitable human substitutions than calf cervical vertebrae, especially with respect to C1, C2, and C7. The biomechanical properties of nerve vascular anatomy and various segment functions in pig and calf cervical vertebrae must be considered when selecting an animal model for research on the spine.

[Establishment of a rabbit model of scoliosis induced by asymmetric load using springs].

OBJECTIVE: To establish rabbit model of scoliosis induced with stable asymmetric lumbar loads. METHODS: Scoliosis was induced in 10 two-month-old New Zealand rabbits using 316L stainless steel springs placed between the unilateral transverse processes of L2 and L5. Serial radiographs were documented before and at 1, 4, 8, 9 and 12 weeks after the operation. At weeks, the rabbits were randomly divided into SR group (n=5) with the spring removed and SK group (n=5) without spring removal. RESULTS: All the rabbits survived the experiment with Cobb angle all greater than 10 degree at the end of the experiment. Significant changes were found in the Cobb angles and kyphotic angles at 1, 4 and 8 weeks after the operation (P<0.05). At 8 weeks, the Cobb angle, the kyphotic angle and the length of the spring were similar between SR and SK groups (P>0.05), and in the 4 weeks following spring removal in SR group, the Cobb angle and the kyphosis decreased significantly compared with those in SK group (P<0.05). Micro-CT showed that the BV/TV of the concave side was greater than that of the convex side. The length of the spring did not show obvious changes during the experiment (P>0.05). CONCLUSIONS: Asymmetric lumbar loading is a convenient, time-saving, and highly reproducible approach for establishing rabbit models of scoliosis.

Computed tomographic morphometric analysis of pediatric clival screw placement at the craniovertebral junction.

STUDY DESIGN: A computed tomography-based morphometric measurement of the pediatric craniovertebral junction for clival screw placement. OBJECTIVE: To identify morphometric differences of the pediatric clivus at different ages and establish guidelines for pediatric clival screw fixation. SUMMARY OF BACKGROUND DATA: Anterior fixation of the pediatric craniovertebral junction, a viable alternative to posterior occipital-cervical fixation, requires clival screw placement. The morphology of the pediatric clivus may be associated with greater difficulty in adequate purchase because of the spheno-occipital synchondrosis (clival fissure). METHODS: Morphometric analysis was conducted on computed tomographic scans of the craniocervical junction in 87 pediatric patients who were assigned into groups based on their ages (2-5 yr, 6-9 yr, 10-13 yr, and 14-16 yr). Measurements were made of the sagittal and axial planes to determine the clival length, widest and narrowest clival diameter, clival fissure distance, clival-cervical angle, and putative screw lengths. RESULTS: The mean clival length, widest diameter, narrowest diameter, fissure distance, and putative screw lengths were 29.4 mm, 28. 9 mm, 17.3 mm, 21.9 mm, and 9.6 mm, respectively. These measurements were significantly different among the groups and highly correlated to age (P < 0.01). There was no significant difference in clival-cervical angle among the groups, with a mean angle of 129.2°± 6.4°. A clival screw (ø3.5 mm) was accommodated for all children older than 10 years, 89% of children aged 6 to 9 years, and 80% of children aged 2 to 5 years. CONCLUSION: A clival screw fixation is feasible in the pediatric craniovertebral junction, particularly in children aged 10 years or older. The dimensions of the clivus were highly dependent on age. We suggest that all pediatric patients should undergo high-resolution, thin-slice computed tomography preoperatively to assess suitability for clival screw fixation. LEVEL OF EVIDENCE: 3.

Experimental cadaveric study of lateral impact of the pelvis in children.

OBJECTIVE: To study the mechanic response of children's pelvis to lateral impact. METHODS: Twelve 2-to 12 year-old children's cadavers were donated by their relatives for this impact test, dividing into younger group (2 to 4 years old, n=6) and elder group (5 to 12 years old, n=6). CT scan and X-ray examination were performed before the impact test, and after the test, X-ray examination and autopsy were conducted. All the pelvises were impacted at a speed of 7.5+/-0.5 m/s but for one at 9.1m/s. RESULTS: All tests showed similar behavior of the pelvis with similar timing and peak viscous criterion (V*C) values. Statistical significance was noted in the maximum V*C and degree of stiffness of the pelvis between the 2 groups (P<0.05). No injuries occurred in the 2 groups after the impact. CONCLUSION: The pelvic test yields very repeatable pelvic response among each group tested.

Role of the biomechanical property of the endplate in anterior cervical fusion.

OBJECTIVE: To study the distribution of the biomechanical properties in the cervical vertebrae with or without the endplate, so as to evaluate the importance of the endplate in cervical anterior fusion. METHODS: Indentation tests were performed at 20 standardized testing points chosen on each surface of the endplate with the impact adjusted perpendicular to the endplate surface using a hemispherical indenter 2 mm in diameter. The failure load and rigidity at each test site were determined from the load-displacement curves. Independent sample t test and factorial analyses were used to analyze the results. RESULTS: On either superior or inferior endplate surface, both the failure load and rigidity differed significantly between the endplate-intact and endplate-removed groups (P < 0.001). The posterior region of the superior endplate and the lateral regions of the inferior endplate were stronger and more rigid than any other region across the endplate surface in the endplate-intact group, while for enplate-removed group, the posterior region of the superior endplate and the posterolateral regions of the inferior endplate were the stronger and more rigid. CONCLUSION: The endplate plays an important role in deciding the success of anterior cervical fusion, and due attention should be paid to the endplate in the intervertebral implant device designing and the surgical approach modification.

[Stability analysis of an enhanced load sharing dynamic pedicle screw fixation device and its equivalent rigid device].

OBJECTIVES: To compare the stability of an enhanced load sharing dynamic pedicle screw fixation device with its equivalent rigid device and to evaluate biomechanical roles of the dynamic fixation. METHODS: A model of L(1) body fracture was produced on seven specimens of fresh adult cadaver spine from T(10) to L(4). Both dynamic and rigid devices were applied in the specimens to strength the injured level. Ranges of three dimensional movements and stiffness under flexion-compression were measured in intact, injured and stabilized specimens. RESULTS: Both dynamic and rigid devices were found to provide significant stability for injured segment in flexion-extension and lateral bending. In axial rotation, the devices could restore the stability to levels similar to those in an intact spine. Results indicated 40% increase in range of motion in flexion-extension and 24.1 Nmm reduction in stiffness of flexion-compression for dynamic device, compared with the rigid device. CONCLUSION: The dynamic device offers a design that may enhance load sharing without sacrificing the stability and will decrease stress-shielding and stress concentration.

[The effect of disc degeneration on the structural property distributions in the cervical vertebral endplates].

OBJECTIVE: To study the effect of disc degeneration on the structural property distributions in the cervical vertebral endplates. METHODS: A 2 mm-diameter hemispherical indenter was used to perform indentation tests at 0.03 mm/s to the depth of 2 mm at 20 normalized locations in 50 bony endplates of intact human cervical vertebrae (C2 approximately C7). The resulting load-displacement curves were used to extract the failure load and stiffness of each test site. Grade of disc degeneration was determined using Nachemson's grading scale. One-way ANOVA, factorial analyses, SNK tests and correlate analyses were used to analyze the result data. RESULTS: Both the failure load and stiffness decreased with disc degeneration in the cervical endplates (P <0.001, both), and correlated significantly with the disc degeneration (rs=-0.429 and rs=-0.244, respectively). Only the distribution of superior cervical endplate changed with disc degeneration, but that of inferior cervical endplate changed little. CONCLUSIONS: The structural property distributions in the cervical vertebral endplates change significantly in the degenerated discs. It suggests that disc degeneration is an important factor to evaluate the intervertebral implant subsidence in anterior cervical fusion.