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.

Effect of different lumbar-iliac fixation and sacral slope for Tile C1.3 pelvic fractures: a biomechanical study.

BACKGROUND: Lumbar-iliac fixation (LIF) is a common treatment for Tile C1.3 pelvic fractures, but different techniques, including L4-L5/L5 unilateral LIF (L4-L5/L5 ULIF), bilateral LIF (BLIF), and L4-L5/L5 triangular osteosynthesis (L4-L5/L5 TOS), still lack biomechanical evaluation. The sacral slope (SS) is key to the vertical shear of the sacrum but has not been investigated for its biomechanical role in lumbar-iliac fixation. The aim of this study is to evaluate the biomechanical effects of different LIF and SS on Tile C1.3 pelvic fracture under two-legged standing load in human cadavers. METHODS: Eight male fresh-frozen human lumbar-pelvic specimens were used in this study. Compressive force of 500 N was applied to the L4 vertebrae in the two-legged standing position of the pelvis. The Tile C1.3 pelvic fracture was prepared, and the posterior pelvic ring was fixed with L5 ULIF, L4-L5 ULIF, L5 TOS, L4-L5 TOS, and L4-L5 BLIF, respectively. Displacement and rotation of the anterior S1 foramen at 30° and 40° sacral slope (SS) were analyzed. RESULTS: The displacement of L4-L5/L5 TOS in the left-right and vertical direction, total displacement, and rotation in lateral bending decreased significantly, which is more pronounced at 40° SS. The difference in stability between L4-L5 and L5 ULIF was not significant. BLIF significantly limited left-right displacement. The ULIF vertical displacement at 40° SS was significantly higher than that at 30° SS. CONCLUSIONS: This study developed an in vitro two-legged standing pelvic model and demonstrated that TOS enhanced pelvic stability in the coronal plane and cephalad-caudal direction, and BLIF enhanced stability in the left-right direction. L4-L5 ULIF did not further improve the immediate stability, whereas TOS is required to increase the vertical stability at greater SS.

TRIM21 inhibits the osteogenic differentiation of mesenchymal stem cells by facilitating K48 ubiquitination-mediated degradation of Akt.

Tripartite motif containing 21 (TRIM21) is a member of the TRIM protein family with E3 ubiquitin ligase activity. Recent studies have demonstrated that TRIM21 widely contributes to physiological and pathological processes by ubiquitylating critical proteins in many kinds of cells. Additionally, multiple studies have shown that TRIM21 plays an important role in multiple cell differentiation processes. However, whether TRIM21 modulates the osteogenic differentiation process of mesenchymal stem cells (MSCs) remains unclear. In this study, we demonstrated that the expression of TRIM21 was decreased during the osteogenic process of MSCs and that TRIM21 negatively regulated the osteogenic capacity of MSCs both in vitro and in vivo. Moreover, we further demonstrated that TRIM21 modulated the osteogenic process of MSCs by acting as an E3 ubiquitin ligase to mediate the K48-linked ubiquitination of Akt and cause degradation. In summary, these results emphasize the critical role of TRIM21 in bone formation and TRIM21 may be a promising target to improve the clinical use of MSCs in tissue engineering.

Effects of manipulations of oblique pulling on the biomechanics of the sacroiliac joint: a cadaveric study.

BACKGROUND: There are many reports on the treatment of sacroiliac joint dysfunction by manipulation of oblique pulling (MOP). However, the specific mechanism of MOP on the sacroiliac joint remains unclear. This study aimed to investigate the effect of MOP on the biomechanics of the sacroiliac joint and the effect of the anterior sacroiliac ligament on the stability of the sacroiliac joint. METHODS: First, MOP-F1 (F: force) and MOP-F2 were applied to nine cadaveric pelvises. Then, segmental resection of the anterior sacroiliac ligament was performed. The range of motion of the sacroiliac joint was observed in all procedures. RESULTS: Under MOP-F1 and F2, the average total angles were 0.84° ± 0.59° and 1.52° ± 0.83°, and the displacements were 0.61 ± 0.21 mm and 0.98 ± 0.39 mm, respectively. Compared with MOP-F1, MOP-F2 caused greater rotation angles and displacements of the sacroiliac joint (p = 0.00 and p = 0.01, respectively). In addition, the rotation angles and displacements of the sacroiliac joint significantly increased after complete resection of the anterior sacroiliac ligament (p = 0.01 and p = 0.02, respectively). The increase was mainly due to the transection of the upper part of the anterior sacroiliac ligament. CONCLUSIONS: MOP-F2 caused greater rotation angles and displacements of the sacroiliac joint and was a more effective manipulation. The anterior sacroiliac ligament played an important role in maintaining the stability of the sacroiliac joint; the upper part of the anterior sacroiliac ligament contributed more to the stability of the joint than the lower part.

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.

MRI-based vertebral bone quality score effectively reflects bone quality in patients with osteoporotic vertebral compressive fractures.

OBJECTIVE: The present study is aimed to validate the ability of the vertebral bone quality (VBQ) score to evaluate bone quality in patients with osteoporotic vertebral compression fractures (OVCF) and to compare it with the ability of T-score by DXA. In addition, the sensitivity of VBQ score with cerebrospinal fluid (CSF) of L2 and L3 segments as baseline is evaluated. METHODS: 196 inpatients were collected and assigned into OVCF and Non-OVCF groups, respectively. For each patient, the VBQ score was calculated by the signal intensity of the L1-L4 vertebral bodies and CSF at L3 or L2 level from T1-weighted MRIs, while T-score from DXA was also obtained. The VBQ and T-score was compared between OVCF and non-OVCF groups, and among age groups. The OVCF ORs by VBQ score and T-score were calculated using logistic regression. RESULTS: OVCF group was significantly different to the non-OVCF group in the T-score (- 2.9 vs. - 0.7) and VBQ score (4.0 vs. 3.5). VBQ score and T-score in patient aged 60-79 years old could indicate the bone quality, but only T-score in patients aged 50-59 years old. OVCF are associated with both higher VBQ score and lower T-score. The VBQ scores calculated by L2 CSF and L3 CSF were similar. CONCLUSIONS: The VBQ score is an effective indicator of bone quality in OVCF patients and comparable to T-score, particularly in people over 60 years old. The VBQ score is not sensitive to CSF of different segments as a baseline.

Ketone Metabolite ß-Hydroxybutyrate Ameliorates Inflammation After Spinal Cord Injury by Inhibiting the NLRP3 Inflammasome.

Ketogenic diet (KD) has been shown to be beneficial in a range of neurological disorders, with ketone metabolite ß-hydroxybutyrate (ßOHB) reported to block the nucleotide oligomerization domain-like receptor family, pyrin domain containing 3 (NLRP3) inflammasome in bone marrow-derived macrophages. In this study, we show that pretreatment with KD or in situ ßOHB suppressed macrophages/microglia activation and the overproduction of inflammatory cytokines, while KD downregulated the expression of NLRP3 inflammasome. Moreover, KD promoted macrophages/microglia transformation from the M1 phenotype to the M2a phenotype following spinal cord injury (SCI) in the in vivo study. Rats in the KD group demonstrated improved behavioral and electrophysiological recovery after SCI when compared to those rats in the standard diet group. The in vitro study performed on BV2 cells indicated that ßOHB inhibited an LPS+ATP-induced inflammatory response and decreased NLRP3 protein levels. Our data demonstrated that pretreatment with KD attenuated neuroinflammation following SCI, probably by inhibiting NLRP3 inflammasome and shifting the activation state of macrophages/microglia from the M1 to the M2a phenotype. Therefore, the ketone metabolite ßOHB might provide a potential future therapeutic strategy for SCI.

Efficacy of Single Level Versus Double Levels Surgery of Percutaneous Disc Nucleoplasty (PDN) Approach in Treating Lumbar Disc Herniation.

BACKGROUND Although percutaneous disc nucleoplasty (PDN) has been widely applied in treating lumbar disc herniation (LDH) in recent years, the efficacy of surgical levels for PDN on LDH has been reported in limited studies. This study aimed to explore and compare the efficacy of surgical levels (single level vs double level) of PDN in treating LDH. MATERIAL AND METHODS All patients diagnosed with LDH from January 2012 to December 2014 in our hospital who underwent PDN were included in this study. Patients were divided into a single-level group and double-level group based on the number of discs/surgical treatment levels. The improvement of visual analog scale (VAS) score, patient satisfaction, and reoperation occurrence were compared between the 2 groups. RESULTS Of 105 total patients, 75 patients were treated with single-level treatment and 30 patients with double-level treatment. VAS for leg pain and patient satisfaction scores in the double-level group were worse than those in the single-level group at 6 months after surgery (P<0.05). Among all 105 patients, the incidence of reoperation was 11.4%. Also, there was a marked difference in reoperation occurrence at 6 months after surgery between the single-level (6.7%) and double-level (23.3%) groups; however, the difference was not statistically significant (P=0.05). CONCLUSIONS PDN is a safe and minimal-invasive approach, which could effectively treat LDH. The number of surgical levels might be an important factor influencing the efficacy of PND. Caution should be exercised to strictly follow the clinical indications for nucleoplasty.

Posterior unilateral exposure and stability reconstruction with pedicle and lamina screw fixation for the cervical dumbbell tumorectomy: a case report and biomechanical study.

PURPOSE: Cervical dumbbell tumor is usually removed via a posterior approach and may require the spinal fixation sometimes. However, the present surgical methods involved either more trauma or a higher risk of instability of the cervical spine. A new technique of unilateral exposure and stability reconstruction with pedicle and lamina screws fixation for posterior cervical dumbbell tumorectomy was described and compared with conventional techniques. METHODS: Posterior unilateral exposure, hemi-laminectomy and facetectomy were performed in one patient with the cervical dumbbell tumor between C3 and C4. The stability was reconstructed by the unilateral pedicle and lamina screws fixation (UPLS), and a strip of shaped allograft bone was also implanted between the superior and inferior lateral mass. Biomechanical stability test of this new technique was investigated using seven fresh-frozen human cervical spine specimens (C4-C7) and compared with unilateral pedicle screw (UPS) and bilateral pedicle screw fixation (BPS) techniques. A continuous pure moment of ± 2.0 Nm was applied to the specimen in flexion, extension, lateral bending and axial rotation. RESULTS: The cervical dumbbell tumor was removed completely, and bone fusion with continuous bone trabecula was maintained in the patient on the final follow-up examination at 18 months postoperatively. Biomechanical stability tests revealed that the range of motion of the UPLS fixation plus graft bone implant was the same as the BPS fixation in flexion (1.8°vs. 1.5°, p = 0.58) and extension (2.3°vs. 2.2°, p = 0.73), but significantly bigger in lateral bending (3.9° vs. 1.0°, p < 0.001) and axial rotation (6.8° vs. 3.8°, p = 0.002), which were significantly smaller than the UPS fixation in all directions (all p < 0.001). CONCLUSIONS: For the treatment of cervical dumbbell tumor, posterior unilateral exposure and stability reconstruction with pedicle and lamina screws fixation following hemi-laminectomy and facetectomy appear to be a more stable and lesser trauma technique. LEVEL OF EVIDENCE: Diagnostic: individual cross-sectional studies with consistently applied reference standard and blinding.

Straighter low lumbar curvature in isthmic spondylolisthesis at L4.

BACKGROUND: This study was conducted to compare differences in imaging features and clinical symptoms between patients with single-level isthmic spondylolisthesis (IS) at L4 and at L5 and to investigate the correlation between imaging and clinical parameters. METHODS: This cross-sectional study evaluated patients with single-level IS who were enrolled between June 2011 and June 2018. A total of 139 patients, 44 in the L4 IS group and 95 in the L5 IS group, met the study criteria and were included. Imaging and clinical parameters obtained from the two groups were compared and analyzed. RESULTS: Patients in the L4 IS group had smaller lower lumbar lordosis (LLL) (27.1 ± 8.2 vs. 30.9 ± 9.3, P = 0.021) and were of older age (58.5 ± 8.7 vs. 52.8 ± 10.1, P < 0.01) than those in the L5 IS group. As per the Roussouly classification system, most patients with L4 IS were classified as Type 2 (43.2%), whereas most patients with L5 IS fell under Type 3 (44.2%). In the L5 IS group, pelvic incidence (PI), pelvic tilt (PT), sacral slope (SS), lumbar lordosis (LL), and L5 incidence (L5I) were positively associated with slippage rate (SR), but the lumbosacral angle (LSA) was negatively associated with SR (P < 0.01). In the L4 IS group, only L5I showed a positive association with SR (P < 0.01). More significant associations were found among sagittal lumbo-pelvic parameters in the L5 IS group, but none were found between SR and Oswestry Disability Index (ODI) in either group. CONCLUSIONS: When compared with patients with L5 IS, patients with L4 IS were of older age and had straighter low lumbar curvature when they were obviously symptomatic. PI was an important parameter for patients with L5 IS while for those with L4 IS, L5I deserved more attention for its significantly positive correlation with the degree of slippage.

Metformin Alleviates the Bone Loss Induced by Ketogenic Diet: An In Vivo Study in Mice.

Metformin (Met), an anti-diabetes drug, has also shown therapeutic effects for ovariectomy-induced (OVX) osteoporosis. However, similar effects against bone loss induced by a ketogenic diet (KD) have not been tested. This study was aimed to evaluate the microarchitectures and biomechanics of KD-induced osteoporosis with and without administration of Met, and compare the effect of Met on bone loss induced by KD with OVX. Forty female C57BL/6J mice were randomly divided into Sham, OVX, OVX + Met (100 mg/kg/day), KD (3:1 ratio of fat to carbohydrate and protein), and KD + Met (100 mg/kg/day) groups. After 12 weeks, the bone mass and biomechanics were measured in distal cancellous bone and in mid-shaft cortical bone of the femur. The activities of serum alkaline phosphatase (ALP) and tartrate-resistant acid phosphatase (TRAP), together with immunohistochemistry staining of osteocalcin (OCN) and TRAP, were evaluated. Both OVX and KD induced significant bone loss and compromised biomechanical properties in the cancellous bone, but no effect was found in cortical bone. The administration of Met increased the cancellous bone volume fraction (BV/TV) from 3.78 to 5.23% following the OVX and from 4.04 to 6.33% following the KD, it also enhanced the compressive stiffness from 47 to 160 N/mm following the OVX and from 35 to 340 N/mm with the KD. Met effectively increased serum ALP in the KD group while decreased serum TRAP in the OVX group, but up-regulated expression of OCN and down-regulated expression of TRAP in both OVX and KD groups. The present study demonstrated that Met effectively attenuated the cancellous bone loss induced by KD and maintained the biomechanical properties of long bones, providing evidence for Met as a treatment of by KD-induced osteoporosis in teenage skeleton.

Ketogenic diet compromises vertebral microstructure and biomechanical characteristics in mice.

Ketogenic diet (KD) compromised the microstructure of cancellous bone and the mechanical property in the appendicular bone of mice, while the effects of KD on the axial bone have not been reported. This study aimed to compare the changes in the microstructure and mechanical properties of the forth lumbar (L4) vertebra in KD and ovariectomized (OVX) mice. Forty eight-week-old female C57BL/6J mice were assigned into four groups: SD (standard diet) + Sham, SD + OVX, KD + Sham, and KD + OVX groups. L4 vertebra was scanned by micro-CT to examine the microstructure of cancellous bone, after which simulative compression tests were performed using finite element (FE) analysis. Vertebral compressive test and histological staining of the L4 and L5 vertebrae were performed to observe the biomechanical and histomorphologic changes. The KD + Sham and SD + OVX exhibited a remarkable declination in the parameters of cancellous bone compared with the SD + Sham group, while KD + OVX demonstrated the most serious bone loss in the four groups. The stiffness was significantly higher in the SD + Sham group than the other three groups, but no difference was found between the remaining groups. The trabecular parameters were significantly correlated with the stiffness. Meanwhile, the OVX + Sham and KD + OVX groups showed a significant decrease in the failure load of compressive test, while there was no difference between the KD + Sham and SD + Sham groups. These findings suggest that KD may compromise the vertebral microstructure and compressive stiffness to a similar level as OVX did, indicating adverse effects of KD on the axial bone of the mice.

Clival screw and plate fixation by the transoral approach for the craniovertebral junction: a CT-based feasibility study.

PURPOSE: A clivus screw and plate was invented and proved to strengthen the stability of the craniovertebral junction (CVJ). However, it is unclear whether the clivus screw and plate could be placed onto the CVJ by transoral approach. Therefore, the present study aims to evaluate the feasibility of clivus screw and plate placement by transoral approach and investigate its relative anatomic parameters. METHODS: A total of 80 normal adults (40 males/40 females) with an average age of 60.4 ± 11.6 years old were enrolled in this study. All parameters were measured in a supposed maximums mouth-opening status on computed tomography images, where the vertex of lower incisor was defined as Point A. The vertical intersection from Point A to extracranial clivus was defined as Point B, and its distance to the bottom of clivus was measured as B length. Point B was considered as ideal screw entry point. All the cases were divided into three types based on the location of Point B: above the top portion (Type 1), between the top and bottom portion (Type 2), and below the bottom portion (Type 3) of extracranial clivus. The B Length was defined as a minus value if the case belonged to Type 3. The anterior skull base angle, the angles between tangent of extracranial clivus and the lines from Point A to different parts of clivus, and distances between Point A and clivus and C1-3 vertebra were also measured. RESULTS: One in eighty cases (1.2%) belonged to Type 1 with a B Length of 32.12 mm. Most cases (61.3%) were Type 2 with a B Length of 8.7 mm, while Type 3's was - 9.7 mm occupying for 37.5%. Significant statistic differences were found in anterior skull base angle between these three types (128.9°, 122.7° and 118.5° for Type 1, 2 and 3, respectively). The distances from Point A to the top and bottom portion of the clivus and the pharyngeal tubercle were 97.5, 96.0 and 96.8 mm, respectively. The angles between the tangent of the clivus and the lines from Point A to the above three structures were 75.7°, 92.3° and 84.0°, respectively. The distances from Point A to the middle point of anterior margin of C1 anterior tubercle, C2 vertebra and C3 vertebra were 79.1, 73.4 and 61.5 mm, respectively. CONCLUSION: The clivus screw and plate placement could be accomplished with optimal screw angle by transoral approach in most of patients. Mandibular splitting would be needed in patients with greater anterior skull angle. These slides can be retrieved under Electronic Supplementary Material.

Ketogenic diet delays spinal fusion and decreases bone mass in posterolateral lumbar spinal fusion: an in vivo rat model.

BACKGROUND: Ketogenic diet (KD), a low-carbohydrate-and-high-fat diet, causes a metabolic state of ketogenesis and has been used to treat drug-resistance epilepsy. Our recent studies showed KD neuroprotective after spinal cord injury and causing bone loss. Effects of KD on spinal fusion were still unknown. This study was aimed to evaluate effects of KD on spinal fusion in rats. METHODS: Thirty-two Sprague-Dawley rats were randomly divided into KD and standard diet (SD) groups. The KD group was fed with food of 1:4 carbohydrates to fat. All rats were subjected to L4/5 posterolateral lumbar spinal fusion. The blood ketone, and serum calcium, phosphorus, and insulin-like growth factor-1 (IGF-1) were measured, as well as the fusion rates, bone mass (BV), and bone mineral contents (BMC) of fusion sites were estimated at 4 and 8 weeks. RESULTS: There was no significant difference in serum calcium or phosphorus levels between groups at 4 or 8 weeks. However, there was a significant increase of blood ketone (1.02 mmol/L vs 0.38 mmol/L at 4 weeks; 0.83 mmol/L vs 0.32 mmol/L, at 8 weeks) and decrease of serum IGF-1 (339.4 ng/mL vs 630.6 ng/mL at 4 weeks; 418.8 ng/mL vs 628.6 ng/mL, at 8 weeks) in the KD group compared with the SD group. The spinal fusion occurred less in the KD group (1/16 vs 6/16 at 4 weeks; 7/16 vs 10/16, at 8 weeks), particularly at 4 weeks after surgery. The BV and BMC were lower in the KD group than that in the SD group at 4 weeks, but not different between groups at 8 weeks. CONCLUSIONS: This study demonstrated that KD delayed spinal fusion and decreased bone mass in posterolateral lumbar spinal fusion in rats.

Ketogenic Diet Compromises Both Cancellous and Cortical Bone Mass in Mice.

To clarify osteoporotic effects of ketogenic diet (KD) on cancellous and cortical bone compared with ovariectomy (OVX) in mice. Forty female C57BL/6J 8-week-old mice were randomly divided into SD+Sham, SD+OVX, KD+Sham, and KD+OVX groups, and fed for 12 weeks. The distal femur of trabecular bone and the middle femur of cortical bone were evaluated with Micro-CT scanning. The maximum bending force and stiffness of the tibia were calculated using a three-point bending test. Osteoblast and osteoclast expression of femur were identified using tartrate-resistant acid phosphatase (TRAP), collagen type I (CoLI), and osteocalcin (OCN) staining. A 2-factor analysis of variance was used to evaluate effects of KD and OVX on radiological, biomechanical, and histological parameters. KD resulted in not only remarkable cancellous bone decline comparable to OVX, but also unique cortical bone reduction. The maximum bending force and stiffness decreased in the KD+Sham and KD+OVX groups but did not change in the SD+OVX group. The KD+OVX led to significantly higher expression in TRAP and noticeably lower expression in CoLI when compared with other groups. Both KD+Sham and SD+OVX prominently increased expression in TRAP, but decreased expression in CoLI. There was no significant difference in OCN among the four groups. The present results suggest that KD compromises both the cancellous and cortical bone architecture of long bones while OVX only in cancellous bone architecture. A combination of KD and OVX may lead to more bone loss.

Biomechanical comparison of transfacet screws to lateral mass screw-rod constructs in the lower cervical spine.

PURPOSE: Transfacet screws have been used as an alternative posterior fixation in the cervical spine. There is lack of spinal stability of the transfacet screws either as stand-along constructs or combined with anterior plate. This study was designed to evaluate spinal stability of transfacet screws following posterior ligamentous injury and combined with anterior plate, respectively, and compare transfacet screws to lateral mass screw-rod constructs. METHODS: Flexibility tests were conducted on eight cadaveric specimens in an intact and injury, and instrumented with the transfacet screw fixation and lateral mass screw-rod construct at C5-C7 levels either after section of the posterior ligamentous complex or combined with an anterior plate and a mesh cage for C6 corpectomy reconstruction. A pure moment of ±2.0 Nm was applied to the specimen in flexion-extension, lateral bending, and axial rotation. Ranges of motion (ROM) were calculated for the C5-C7 segment. RESULTS: ROM with the transfacet screws was 22 % of intact in flexion-extension, 9 % in lateral bending and 11 % in axial rotation, while ROM with the lateral mass screw-rod construct was 9 % in flexion-extension, 8 % in lateral bending and 22 % in axial rotation. The only significant difference between two constructs was seen in flexion-extension (5.8 ± 4.2° vs. 2.4 ± 1.2°, P = 0.002). When combined with an anterior plate and mesh cage, the transfacet screw fixation reduced ROM to 3.0° in flexion-extension, 1.2° in lateral bending, and 1.1° in axial rotation, which was similar to the lateral mass screw-rod construct. CONCLUSIONS: This study identified the transfacet screw fixation, as stand-alone posterior fixation, was equivalent to the lateral mass screw-rod constructs in axial rotation and lateral bending except in flexion-extension. When combined with an anterior plate, the transfacet screw fixation was similar to the lateral mass screw-rod construct in motion constraint. The results suggested the transfacet screw fixation a biomechanically effective way as supplementation of anterior fixation.

Feasibility and trajectory study of anterior transarticular crossing screw placement for atlantoaxial joint instability: a cadaveric study and description of a novel technique.

PURPOSE: In unique clinical situations where C1-C2 anterior transarticular screw (ATS) fixation is not available or has failed, an anterior transarticular crossing screw (ATCS) with transcorporal pathway of the screws inside the contralateral promontory of C2 may enhance the stabilization and achieve atlantoaxial arthrodesis. The present study was to describe a novel technique of ATCS fixation for atlantoaxial joint instability and its applied anatomy, and compared it with ATS fixation method. METHODS: Direct measurements using digital calipers and a goniometer were conducted on 30 pairs of dried human C1 and C2 vertebrae. The ATS and ATCS with screws (Φ 4.0 mm) were performed on 11 fresh cervical spine specimens. The screw lengths in the C1 and C2, and screw entry angles of the ATS and ATCS were measured, respectively. Cadaver specimens were dissected to observe the incidence of violation to the important structures surrounding the ATS and ATCS fixation technique. RESULTS: There was enough osseous space for ATCS placement. The lateral and incline angle of the ATCS was 36.2° and 28.7°, respectively. Screw purchase in C2 of the ATCS (25.6 mm) was greater than that of the ATS (11.4 mm). The ATCS C1 purchase (14.8 mm) was similar to the ATS C1 purchase (14.9 mm). No violation to the vertebral artery groove, the spinal canal or the atlanto-occipital joint was observed after the ATCS placement. CONCLUSION: Anterior transarticular crossing screw is a feasible and viable option for atlantoaxial fixation in selected cases. This technique achieved remarkable longer screw purchase and could enhance the atlantoaxial stability.

A clivus plate fixation for reconstruction of ventral defect of the craniovertebral junction: a novel fixation device for craniovertebral instability.

PURPOSE: A fabricated mesh cage and/or posterior occipitocervical instrumentation alone has been used for reconstruction of ventral defect of the upper cervical spine. However, using a trimmed mesh cage it was hard to achieve optimal clival screw purchase and it migrated or broke. A specific instrumentation at the craniovertebral junction (CVJ) should incorporate the morphology of the CVJ and biomechanical validation. The purpose of the present study was to develop an innovative clivus plate integrated with the clinical anatomy of CVJ and to evaluate the stability of the clivus plate fixation (CPF), stand-alone or combined with a posterior occipitocervical fixation (POCF). METHODS: Dimensions relevant to the clivus plate were measured on 40 adult dry bones and CT images of 30 patients. The CPF was composed of the clivus plate and a titanium mesh cage. The clivus plate was anchored to the clivus, atlas and C3 body and connected to the mesh cage. Six fresh cadaveric head-neck specimens (Oc-C4) were used in this study (46 ± 15 years old, 2 F/4 M). A continuous pure moment of ±1.5 Nm was applied to the specimen in flexion, extension, lateral bending and axial rotation. The status of intact, CPF alone, and CPF plus POCF was tested on each specimen. The CPF was implanted to the specimen following resection of the C1 anterior arch, C2 vertebral body, C2-C3 disc and atlantoaxial ligaments. The POCF was applied with screws anchoring at the occiput, C1, C3 and C4. The range of motion (ROM) and neutral zone (NZ) from the occiput to C3 were calculated. RESULTS: The clivus plate was developed based on measurements of 40 adult dry bones and CT images of 30 patients. The plates were successfully applied to all specimens. No obvious loosening or mismatch was observed. The mean clival length and widest and narrowest diameter of the clivus were 26, 33 and 19 mm, respectively. The clivus screw length was 8 mm for the caudal holes and 10 mm for the cephalad hole. The CPF reduced ROMs to 3.9° in flexion, 2.8° in extension, 4.2° in lateral bending and 6.8° in axial rotation. The combined CPF and POCF constrained motion within 0.6° in all directions and more than the CPF (P < 0.05). NZs after the CPF were 1.0° in flexion-extension, 2.1° in lateral bending and 2.2° in axial rotation, respectively. NZs after the CPF plus POCF were within 0.2° in all directions and less than the CPF (P < 0.05). CONCLUSION: This study demonstrated screw purchase in the adult clivus and developed an innovative clivus plate fixation for reconstructing an extensive ventral defect in the upper cervical spine. The clivus plate fixation combined a posterior instrumentation ensuring reliable upper cervical stability.

The effects of osteoporosis and disc degeneration on vertebral cartilage endplate lesions in rats.

PURPOSE: Evidence has shown that osteoporosis or intervertebral disc degeneration (IDD) led to cartilage endplate lesions (CEL), but their combined effects on the lesion remain unknown. This study developed an innovative rat model combined ovariectomy (OVX) and cervical muscle section (CMS), and aimed to evaluate the combined effects of osteoporosis and IDD on cartilage endplate lesions of cervical spine. METHODS: Fifty-two Sprague-Dawley female rats were assigned randomly into four groups as follows: the sham group (n = 10) underwent sham surgery; the OVX group (n = 14) was subjected to bilateral ovariectomy; the CMS group (n = 14) had posterior paraspinal muscles cut from C2 to C7; the CMS-OVX group (n = 14) underwent the OVX and CMS surgeries consecutively. Samples of C6-C7 segments were harvested at 12, 18 and 24 weeks post-surgery. Micro-CT analysis was performed to evaluate the CEL, intervertebral disc height (IDH) and structural indices. Histological analysis with Safranine O/fast green stain and histological score were used to observe the characteristics of the degenerative discs. RESULTS: Ovariectomy surgery resulted in significant changes of most structural indices of the C6 body, such as decrease of percent bone volume and number of bone trabecula at 12 weeks, and greater changes at 18 and 24 weeks. The CEL following CMS surgery was seen on the ventral, while the CEL in the OVX and sham groups on the peripheral. The CEL was greatest in the CMS-OVX group and significantly greater than that in the CMS and OVX groups at 12 and 18 weeks (P < 0.05). The CMS surgery resulted in significant IDH decrease at 12, 18 and 24 weeks (P < 0.05), while the OVX surgery resulted in mild IDH decrease when compared with the sham group. The IDH in the CMS-OVX group was significantly lower than that in the CMS group at 24 weeks (P < 0.05). Histological evaluation suggested cartilage endplate abrasion at 12 weeks, and in situ calcification at 18 and 24 weeks in the CMS and CMS-OVX groups. Disc degenerative scores were higher following CMS or OVX surgery, and correlated with the CEL and IDH (P < 0.01), respectively. CONCLUSIONS: The present study suggested that a combination of OVX and CMS led to more lesion of cartilage endplate than any one thereof, as well as more decrease of IDH. The lesion and IDH decrease were associated with the disc degeneration levels. The cartilage endplate was worn out at the early stage and calcified in situ later. The results indicate that osteoporosis may deteriorate the disc degeneration at specific time.