Biomechanical evaluation of reinsertion and revision screws in the subaxial cervical vertebrae.

BACKGROUND: This study aimed to evaluate the biomechanical effects of reinserted or revised subaxial cervical vertebral screws. METHODS: The first part aimed to gauge the maximum insertional torque (MIT) of 30 subaxial cervical vertebrae outfitted with 4.0-mm titanium screws. A reinsertion group was created wherein a screw was wholly removed and replaced along the same trajectory to test its maximum pullout strength (MPOS). A control group was also implemented. The second part involved implanting 4.0-mm titanium screws into 20 subaxial cervical vertebrae, testing them to failure, and then reinserting 4.5-mm revision screws along the same path to determine and compare the MIT and MPOS between the test and revision groups. RESULTS: Part I findings: No significant difference was observed in the initial insertion's maximum insertion torque (MIT) and maximum pull-out strength (MPOS) between the control and reinsertion groups. However, the MIT of the reinsertion group was substantially decreased compared to the first insertion. Moderate to high correlations were observed between the MIT and MPOS in both groups, as well as between the MIT of the first and second screw in the reinsertion group. Part II, the MIT and MPOS of the screw in the test group showed a strong correlation, while a modest correlation was observed for the revision screw used in failed cervical vertebrae screw. Additionally, the MPOS of the screw in the test group was significantly higher than that of the revision screw group. CONCLUSION: This study suggests that reinsertion of subaxial cervical vertebrae screws along the same trajectory is a viable option that does not significantly affect fixation stability. However, the use of 4.5-mm revision screws is inadequate for failed fixation cases with 4.0-mm cervical vertebral screws.

A Novel Method to Improve the Accuracy and Stability of the 3D Guide Template Technique Applied in Upper Cervical Spine Surgery.

AIM: To evaluate the safety and accuracy of C1 and C2 pedicle screw placement using a three-dimensional (3D)-printed double template and compare them with those of the conventional method in a clinical study. MATERIAL AND METHODS: DICOM format data from 60 cases with C1-C2 instability were obtained after computed tomography (CT) was performed. A total of 32 cases underwent surgery via the free-hand technique, whereas 28 cases underwent surgery via a 3D-printed "pointing-drilling" guide template. The ideal trajectory of the C1 and C2 pedicle screws was designed using a baseplate as a separate complementary template for the corresponding posterior C1-C2 anatomical surface, after which the "pointingdrilling" guide template was materialized using a 3D printing machine. The 3D-printed "pointing-drilling" guide template, which was sterilized with low-temperature plasma, was used to locate the starting point and determine the drill trajectory during surgery. The positions of the screws in the axial and sagittal planes of the CT scan were observed and categorized into four grades, after which the operative time, fluoroscopy time, and intraoperative bleeding in the two groups were compared. RESULTS: No significant difference (p > 0.05) in each screw classification grade was observed between the free-hand and "pointingdrilling" template groups; however, a significant difference was observed (p=0.048) between these two groups. A significant difference (p < 0.05) in fluoroscopy times was observed between the free-hand and "pointing-drilling" template groups. Conversely, no significant differences were observed in bleeding (p=0.491) and operative time (p=0.309) between the free-hand and "pointingdrilling" template groups. CONCLUSION: The 3D-printed "pointing-drilling" guide template technique promoted more secure C1 and C2 pedicle screw placement compared with the free-hand technique in clinics.

Caffeic acid modulates activation of neutrophils and attenuates sepsis-induced organ injury by inhibiting 5-LOX/LTB4 pathway.

BACKGROUND: Sepsis is a critical systemic inflammatory syndrome which usually leads to multiple organ dysfunction. Caffeic acid (CA), a phenolic compound derived from various plants, has been proved to be essential in neuroprotection, but its role in septic organ damage is unclear. This research aimed to investigate whether CA protects against organ injury in a mouse model of cecal ligation and puncture (CLP). METHODS: CA (30 mg/kg) or vehicle was administered by intraperitoneal injection immediately after CLP. The samples of blood, lungs, and livers were collected 24 h later. Organ injury was assessed by histopathological examination (HE staining), neutrophil infiltration (myeloperoxidase fluorescence), oxidative stress levels (MDA, SOD, HO-1), and inflammatory cytokines (TNF-α, IL-1ß, and IL-6) release in lung and liver tissues. Neutrophil extracellular trap (NET) formation was analyzed by immunofluorescence. In vitro experiments were performed to investigate the potential mechanisms of CA using small interfering RNA (siRNA) techniques in neutrophils, and the effect of CA on neutrophil apoptosis was analyzed by flow cytometry. RESULTS: Results showed that CA treatment improved the 7-day survival rate and attenuated the histopathological injury in the lung and liver of CLP mice. CA significantly reduced neutrophil infiltration in the lungs and livers of CLP mice. TNF-α, IL-1ß, IL-6 and LTB4 were reduced in serum, lung, and liver of CA-treated CLP mice, and phosphorylation of MAPK (p38, ERK, JNK) and p65 NF-κB was inhibited in lungs and livers. CA treatment further increased HO-1 levels and enhanced superoxide dismutase (SOD) activity, but reduced malondialdehyde (MDA) levels and NET formation. Similarly, in vitro experiments showed that CA treatment and 5-LOX siRNA interference inhibited inflammatory activation and NET release in neutrophils, suppressed MAPK and NF-κB phosphorylation in LPS-treated neutrophils, and decreased LTB4 and cfDNA levels. Flow cytometric analysis revealed that CA treatment reversed LPS-mediated delayed apoptosis in human neutrophils, and Western blot also indicated that CA treatment inhibited Bcl-2 expression but increased Bax expression. CA treatment did not induce further changes in neutrophil apoptosis, inflammatory activation, and NET release when 5-LOX was knocked down by siRNA interference. CONCLUSIONS: CA has a protective effect on lung and liver injury in a murine model of sepsis, which may be related to inhibition of the 5-LOX/LTB4 pathway.

Transcriptome profiling of the initial segment and proximal caput of mouse epididymis.

Background: The proximal region of the mouse epididymis plays a pivotal role in sperm transport, sperm maturation, and male fertility. Several studies have focused on segment-dependent gene expression of the mouse epididymis through high-throughput sequencing without the precision of the microdissection. Methods and results: Herein, we isolated the initial segment (IS) and proximal caput (P-caput) by physical microdissection using an Lcn9-cre; Rosa26tdTomato mouse model. We defined the transcriptome changes of caput epididymis by RNA sequencing (RNA-seq), which identified 1,961 genes that were abundantly expressed in the IS and 1,739 genes that were prominently expressed in the P-caput. In addition, we found that many differentially expressed genes (DEGs) were predominantly or uniquely expressed in the epididymis and region-specific genes were highly associated with transport, secretion, sperm motility, fertilization, and male fertility. Conclusion: Thus, this study provides an RNA-seq resource to identify region-specific genes in the caput epididymis. The epididymal-selective/specific genes are potential targets for male contraception and may provide new insights into understanding segment-specific epididymal microenvironment-mediated sperm transport, maturation, and male fertility.

ß-Nicotinamide mononucleotide activates NAD+/SIRT1 pathway and attenuates inflammatory and oxidative responses in the hippocampus regions of septic mice.

Sepsis-associated encephalopathy (SAE) is one of the common serious complications in sepsis, and the pathogenesis of SAE remains unclear. Sirtuin 1 (SIRT1) has been reported to be downregulated in the hippocampus and SIRT1 agonists can attenuated the cognitive dysfunction in septic mice. Nicotinamide adenine dinucleotide (NAD+) is a key substrate to maintain the deacetylation activity of SIRT1. As an intermediate of NAD+, ß-Nicotinamide Mononucleotide (NMN) has been reported to be promising in treating neurodegenerative diseases and cerebral ischemic injury. Thus we sought to investigate the potential role of NMN in SAE treatment. The SAE model was established by cecal ligation and puncture (CLP) in vivo, and neuroinflammation model was established with LPS-treated BV-2 cells in vitro. Memory impairment was assessed by Morris water maze and fear conditioning tests. As a result, the levels of NAD+, SIRT1 and PGC-1α were significantly reduced in the hippocampus of septic mice, while the acetylation of total lysine, phosphorylation of P38 and P65 were enhanced. All these changes induced by sepsis were inverted by NMN. Treating with NMN resulted in improved behavior performance in the fear conditioning tests and Morris water maze. Apoptosis, inflammatory and oxidative responses in the hippocampus of septic mice were attenuated significantly after NMN administration. These protective effect of NMN against memory dysfunction, inflammatory and oxidative injuries were reversed by the SIRT1 inhibitor, EX-527. Similarly, LPS-induced activation of BV-2 cells were attenuated by NMN, EX-527 or SIRT1 knockdown could reverse such effect of NMN in vitro. In conclusion, NMN is protective against sepsis-induced memory dysfunction, and the inflammatory and oxidative injuries in the hippocampus region of septic mice. The NAD+/SIRT1 pathway might be involved in one of the mechanisms of the protective effect.

Clinical characteristic and surgical treatment of traumatic lumbar spondylolisthesis: A series of 28 patients.

OBJECTIVE: To explore the clinical characteristics and the short-term efficacy of posterior operation for traumatic lumbar spondylolisthesis. METHODS: All 28 patients (between January 2013 and June 2018) were treated with lumbar pedicle screw fixation combined with posterior intervertebral fusion. The clinical data and imaging materials of these patients were retrospectively analyzed. RESULTS: The mean follow-up period was 24.3 months (12-36 months). The average VAS score and JOA score were significantly improved after surgery, and the difference was statistically significant (P<0.05).The last follow-up X-ray showed that 16 cases were degree 0 and 12 cases were degree I according to Meyerding grading, which were statistically improved compared with preoperative. Postoperative CT indicated lumbar internal fixation well, and the lumbar fusion rate was 100%. The Frankel grading of neurological function was significantly improved compared with preoperative. CONCLUSION: Acute traumatic lumbar spondylolisthesis is caused by severe trauma and mostly occurred at L4/L5 and L5/S1 level. Early posterior reduction, decompression and intervertebral fusion can achieve satisfactory clinical and radiological outcome.

Epididymal initial segment-specific Cre recombinase activity in Lcn8-Cre knock-in mice.

BACKGROUND: Sperm acquire the ability to fertilize ova through a complex process of epididymal maturation. To identify the functions of genes expressed in the proximal epididymis, mouse models specific to this region are needed. METHODS AND RESULTS: A Lcn8-Cre knock-in mouse line was generated using CRISPR/Cas9 technology. A 37 bp coding sequence of Lcn8 from the ATG start codon was replaced by an NLS-Cre-polyA cassette, resulting in Cre expression and the absence of Lcn8. Epididymal initial segment-specific Cre expression was identified using RT-PCR and western blotting, and the spatial-temporal Cre activity was further confirmed by using the Rosa26tdTomato reporter mice. Immunofluorescence staining showed that active Cre recombinase was present in the principal cells. Histological analyses of sperm and epididymides, and the four-month mating tests, were used to confirm that Cre expression did not affect normal development and male fecundity. CONCLUSIONS: The novel Lcn8-Cre mice can be used to establish epididymal initial segment-specific conditional knock-out mouse models.

A novel mouse line with epididymal initial segment-specific expression of Cre recombinase driven by the endogenous Lcn9 promoter.

Spermatozoa released from testes undergo a maturation process and acquire the capacity to fertilize ova through epididymal transit. The epididymis is divided into four regions, each with unique morphology, gene profile, luminal microenvironment and distinct function. To study the functions of relevant genes in the epididymal initial segment (IS), a novel IS-specific mouse model, Lcn9-Cre knock-in (KI) mouse line was generated via CRISPR/Cas9 technology. The TAG stop codon was replaced by a 2A-NLS-Cre cassette, resulting in the co-expression of Lcn9 and Cre recombinase. IS-specific Cre expression was first observed from postnatal day 17. Using the Rosa26tdTomato reporter mice, the Cre-mediated DNA recombination was detected exclusively in principal cells. The epididymal IS-specific Cre activity in vivo was further confirmed using Lcn9-Cre mice crossed with a mouse strain carrying Tsc1 floxed alleles (Tsc1flox/+). Cre expression did not affect either normal development or male fecundity. Different from any epididymis-specific Cre mice reported previously, the novel Lcn9-Cre mouse line can be used to introduce entire IS-specific conditional gene editing for gene functional study.

Carboxymethyl chitosan-decorated proliposomes as carriers for improved stability and sustained release of flaxseed oil.

A flaxseed oil carboxymethyl chitosan-decorated proliposome system was fabricated in this research. The physicochemical characteristics, stability, and in vitro release behaviors of flaxseed oil were studied and compared with that of flaxseed oil-loaded liposomes. The results of dynamic light scattering, transmission electron microscopy, and oxidation stability indicated that the storage stability of proliposomes was better. After 28 days of storage, the peroxide value of flaxseed oil-loaded liposomes (20.1 meq/kg) was significantly (P < 0.05) higher than that of flaxseed oil-loaded proliposomes (9.0 meq/kg); the thiobarbituric acid reactive substances in the former (0.53 mmol/kg) was also higher than that in the latter (0.27 mmol/kg). The in vitro release behavior of flaxseed oil indicated the proliposomes were more stable in the simulated gastrointestinal fluids. Therefore, the flaxseed oil-loaded proliposome system could be a promising vehicle for delivery flaxseed oil in food industry. PRACTICAL APPLICATION: A flaxseed oil-loaded proliposome delivery system was fabricated in this research. Their physical and oxidation stability of flaxseed oil were improved, and the in vitro cumulative release of flaxseed oil was delayed compared with flaxseed oil liposomes. This system may provide an effective strategy for the flaxseed oil encapsulation in the food industry.

A Comparison Study of Three Posterior Fixation Strategies in Transforaminal Lumbar Interbody Fusion Lumbar for the Treatment of Degenerative Diseases.

BACKGROUND: There are various posterior fixations utilized with transforaminal lumbar interbody fusion (TLIF). Previous studies have focused on the comparison of two fixation techniques. MATERIALS AND METHODS: Sixty five patients with single-level lumbar disease were included in this retrospective study. Group A was treated by TLIF with bilateral pedicle screw (BPS), Group B treated by TLIF with unilateral pedicle screw (UPS), and Group C treated by TLIF with UPS plus contralateral translaminar facet screw (UPSFS). The operative time, blood loss, Oswestry disability index (ODI), Japanese Orthopaedic Association Scores (JOA), and visual analog scores (VAS) were recorded. Radiographic examination was used to assess fusion rates and incidence of screw failure. RESULTS: The blood loss and operative times were 188.69 ± 37.69 ml and 132.96.5 ± 8.69 min in BPS group, 117.27 ± 27.11 ml and 99.32 ± 12.94 min in UPS group, and 121.50 ± 22.54 ml and 112.55 ± 9.42 min in UPSFS group; UPS and UPSFS were better than BPS (P < 0.05). The mean followup time was 38.2 months. Fusion rates were - BPS group: 95.6%, UPS group: 90%, UPSFS: 95% (P > 0.05). Screw and/or rod failures were found in three groups (BPS group: 1, UPS group: 2 and UPSFS: 1, P > 0.05). The average postoperative VAS, ODI, and JOA scores of BPS, UPS, and UPSFS were improved significantly in each group compared to preoperative scores (P < 0.05); there were no significant differences between any two groups at each followup time point (P > 0.05). CONCLUSION: UPSFS with TLIF is a viable treatment option that provides satisfactory clinical results; the clinical outcome and the complication rate were comparable to BPS. In addition, the invasive of UPSFS cases was comparable to UPS and better than BPS cases. For UPS, it could be used in suitable patients.

Template-assisted 192Ir-based stereotactic ablative brachytherapy as a neoadjuvant treatment for operable peripheral non-small cell lung cancer: a phase I clinical trial.

PURPOSE: To evaluate safety, feasibility, and efficacy of template-assisted 192Ir-based stereotactic ablative brachytherapy (SABT), combined with surgery for peripheral non-small cell lung cancer (NSCLC). MATERIAL AND METHODS: Patients with pathologically confirmed operable peripheral NSCLC, who underwent template-assisted SABT (30 Gy delivered in one fraction) and were scheduled for tumor resection 4-6 weeks after SABT were included in this study. The perioperative adverse reactions of SABT were recorded to evaluate safety and feasibility of SABT for neoadjuvant therapy. Dosimetric data from both simulated and actual plans were collected and compared. Imaging with 18F-fluorodeoxyglucose-positron emission tomography/computed tomography (18F-FDG-PET/CT) and dynamic contrast-enhanced computed tomography were scheduled before SABT and surgery to evaluate the efficacy of the neoadjuvant therapy with SABT. RESULTS: Patients did not experience any serious adverse events. None of the patients had a delay in receiving surgery. After 4-6 weeks, the indicators for the efficacy of neoadjuvant therapy significantly decreased in all patients: gross tumor volume (p < 0.001), maximum standardized uptake value (p < 0.001), tumor blood volume (p < 0.001), and tumor blood flow (p = 0.008). Dosimetric parameters in the delivered SABT plan slightly changed from the preoperative simulation, but the difference was not statistically significant (p > 0.05). CONCLUSIONS: The efficacy of template-assisted SABT for neoadjuvant therapy was significant in operable peripheral NSCLC. Moreover, no serious adverse reactions were observed; when the coplanar template guidance technique was applied, dosimetric parameters were in good agreement between the actual SABT plan and the preoperative simulated plan.

[Clinical and radiological results of thoracic and lumbar fracture and dislocation treated with posterior transforaminal decompression and interbody fusion].

OBJECTIVE: To evaluate the clinical and radiological results of patients with thoracic and lumbar fracture and dislocation treated by posterior transforaminal decompression and interbody fusion. METHODS: From June 2010 to June 2017, posterior transforaminal decompression, interbody fusion combined with pedicle screw fixation were performed in 21 patients with thoracic and lumbar fracture and dislocation. Their clinical and radiological data were collected and retrospectively analyzed, including 15 males and 6 females, aged from 25 to 58 years with an average of 45 years old. According to the criterion of American Spinal Injury(ASIA), preoperative neurological function was graded A in 3 cases, B in 7 cases, C in 6 cases, D in 4 cases and E in 1 case. Operative time and intraoperative blood loss and correlative complications were recorded. And VAS score, ODI and Cobb angle were evaluated before and after surgery. The improvement of neurological function was also analyzed at the final follow-up. Intervertebral bony fusion was observed during the follow-up by CT three-dimensional reconstruction. RESULTS: The operative time was 150 to 240 min with an average of (192±47) min. The intraoperative blood loss was 380 to 750 ml with an average of(603±120) ml. Dura sac tearing and cerebral fluid leakage occurred in 3 cases and were repaired during operation; superficial wound infection occurred in 1 case, and got healing after dressing change. The postoperative follow-up duration was 24 to 45 months with an average of(37.0±9.5) months. VAS score was improved from preoperative 8.9±0.4 to immediately postoperative 4.2±1.3(P<0.05). At the final follow-up, VAS score decreased further to 3.6±0.8. ODI was decreased from preoperative (95.30±3.52)% to (32.51±6.30)% at the final follow-up (P<0.05). Cobb angle was corrected from preoperative (21.2±8.8)° to immediately postoperative(2.3±3.1)° (P<0.05). At the final follow-up, Cobb angle was (3.2±2.5)°, showing no significant difference with immediately postoperative value. The neurological function was grade A in 3 cases, B in 3 cases, C in 5 cases, D in 6 cases and E in 4 cases at the final follow-up. All the patients got solid intervertebral bone fusion in 8 to 13 months after operation, with an average fusion time of (10.3±2.5) months. CONCLUSIONS: For the patients with thoracic and lumbar fracture and dislocation mainly involving intervertebral disc and endplate plane, posterior transforaminal decompression and interbody fusion not only is less invasive, but also can effectively reconstruct spinal three column and obtain good biomechanical stability. And, it is beneficial for the good recovery of neurological function.

[Effects of HDAC Inhibitor Scriptaid on IM9 Cell Line and Its Mechanism].

OBJECTIVE: To study the effect of HDAC inhibitor Scriptaid on multiple myeloma IM9 cells and preliminarily clarify the mechanism of Scriptaid-induced cell apoptosis. METHODS: The cell viability, cell cycle and cell apoptosis were measured by CCK8 assay and flow cytometry respectively, the relative target gene expression levels were detected by RT-PCR, the effect of Scriptaid on p21 promoter activity was detected by using luciferase reporter assay. RESULTS: Scriptaid inhibited IM9 cell viability in a dose-dependent manner. Scriptaid induced IM9 cell cycle arrest at G2/M phase in a dose-dependent manner. Scriptaid triggered IM9 cell apoptosis was obviously, the mRNA levels of apoptosis-related proteins Caspase 9, Caspase 3 and PARP1 were also activated. The apoptosis-associated factors BAD, PTEN and p21 increased following treatment with different dose of Scriptaid, meanwhile, p21 promoter activity was also activated significantly. CONCLUSION: HDAC inhibitor Scriptaid can promote IM9 cell apoptosis by transcriptional activation of p21 promoter in concentration-dependent manner.

A fluorescent τ-probe: quantitative imaging of ultra-trace endogenous hydrogen polysulfide in cells and in vivo.

Hydrogen sulfide (H2S) has been recognized as an important endogenous gasotransmitter associated with biological signaling transduction. However, recent biological studies implied that the H2S-related cellular signaling might actually be mediated by hydrogen polysulfides (H2S n , n > 1), not H2S itself. Unraveling such a mystery strongly demanded the quantification of endogenous H2S n in living systems. However, endogenous H2S n has been undetectable thus far, due to its extremely low concentration within cells. Herein, we demonstrated a strategy to detect ultra-trace endogenous H2S nvia a fluorescent τ-probe, through changes of fluorescence lifetime instead of fluorescence intensity. This τ-probe exhibited an ultrasensitive response to H2S n , bringing about the lowest value of the detection limit (2 nM) and a lower limit of quantification (10 nM) to date. With such merits, we quantified and mapped endogenous H2S n within cells and zebrafish. The quantitative information about endogenous H2S n in cells and in vivo may have a significant implication for future research on the role of H2S n in biology. The methodology of the τ-probe established here might provide a general insight into the design and application of any fluorescent probes, beyond the limit of utilizing fluorescence intensity.

Rcan2 and estradiol independently regulate body weight in female mice.

Rcan2 increases food intake and plays an important role in the development of age- and diet- induced obesity in male mice. However, in females, wild-type mice grow almost at a similar rate as Rcan2-/- mice on normal chow diet from 6 weeks of age. Here we showed that the ability of Rcan2 to promote weight gain was attenuated by energy expenditure mediated by 17ß-estradiol in female mice. Using ovariectomy-operated models, we found that 17ß-estradiol deprivation did not alter food intake, but induced more weight gain in wild-type mice than Rcan2-/- mice. If wild-type mice ingested equally as Rcan2-/- mice, in the same ovarian state they exhibited similar weight changes, but the mice in ovariectomized groups were significantly heavier than the ovarian-intact mice, suggesting that body weight is not only regulated by Rcan2, but also by 17ß-estradiol. Furthermore, we demonstrated that Rcan2 and 17ß-estradiol independently regulated body weight even on high-fat diets. Therefore, our findings indicate that Rcan2 and 17ß-estradiol regulate body weight through different mechanisms. Rcan2 increases food intake, whereas 17ß-estradiol promotes energy expenditure. These findings provide novel insights into the sexual dimorphism of body weight regulation.

Optimal Entry Point and Trajectory for Anterior C1 Lateral Mass Screw.

STUDY DESIGN: A radiographic analysis of the anatomy of the C1 lateral mass using computed tomography (CT) scans and Mimics software. OBJECTIVE: To define the anatomy of the C1 lateral mass and make recommendations for optimal entry point and trajectory for anterior C1 lateral mass screws. SUMMARY OF BACKGROUND DATA: Although various posterior insertion angles and entry points for screw insertion have been proposed for posterior C1 lateral mass screws, no large series have been performed to assess the ideal entry point and optimal trajectory for anterior C1 lateral mass screw placement. MATERIALS AND METHODS: The C1 lateral mass was evaluated using CT scans and a 3-dimensional imaging application (Mimics software). Measuring the space available for the anterior C1 lateral mass screw (SAS) at different camber angles from 0 to 30 degrees (5-degree intervals) was performed to identify the ideal camber angle of insertion. Measuring the range of sagittal angles was performed to calculate the ideal sagittal angle. Other measurements involving the height of the C1 lateral mass were also made. RESULTS: The optimal screw entry point was found to be located on the anterior surface of the atlas 12.88 mm (±1.10 mm) lateral to the center of the anterior tubercle. This optimal entry point was found to be 6.81 mm (±0.59 mm) superior to the anterior edge of the atlas inferior articulating process. The mean ideal camber angle was 20.92 degrees laterally and the mean ideal sagittal angle was 5.80 degrees downward. CONCLUSIONS: These measurements define the optimal entry point and trajectory for anterior C1 lateral mass screws and facilitate anterior C1 lateral mass screw placement. A thorough understanding of the local anatomy may decrease the risk of injury to the spinal cord, vertebral artery, and internal carotid artery. Delineating the anatomy in each case with preoperative 3D CT evaluation is recommended.

Comparison of occipitocervical and atlantoaxial fusion in treatment of unstable Jefferson fractures.

BACKGROUND: Controversy exists regarding the management of unstable Jefferson fractures, with some surgeons performing reduction and immobilization of the patient in a halo vest and others performing open reduction and internal fixation. This study compares the clinical and radiological outcome parameters between posterior atlantoaxial fusion (AAF) and occipitocervical fusion (OCF) constructs in the treatment of the unstable atlas fracture. MATERIALS AND METHODS: 68 consecutive patients with unstable Jefferson fractures treated by AAF or OCF between October 2004 and March 2011 were included in this retrospective evaluation from institutional databases. The authors reviewed medical records and original images. The patients were divided into two surgical groups treated with either AAF (n = 48, F/M 30:18) and OCF (n = 20, F/M 13:7) fusion. Blood loss, operative time, Japanese Orthopaedic Association (JOA) score, visual analog scale (VAS) score, atlanto-dens interval, lateral mass displacement, complications, and the bone fusion rates were recorded. RESULTS: Five patients with incomplete paralysis (7.4%) demonstrated postoperative improvement by more than 1 grade on the American Spinal Injury Association impairment scale. The JOA score of the AAF group improved from 12.5 ± 3.6 preoperatively to 15.7 ± 2.3 postoperatively, while the JOA score of the OCF group improved from 11.2 ± 3.3 preoperatively to 14.8 ± 4.2 postoperatively. The VAS score of AAF group decreased from 4.8 ± 1.5 preoperatively to 1.0 ± 0.4 postoperatively, the VAS score of the OCF group decreased from 5.4 ± 2.2 preoperatively to 1.3 ± 0.9 postoperatively. CONCLUSIONS: The OCF or AAF combined with short-term external immobilization can establish the upper cervical stability and prevent further spinal cord injury and nerve function damage.

A disputed evidence on obesity: comparison of the effects of Rcan2(-/-) and Rps6kb1(-/-) mutations on growth and body weight in C57BL/6J mice.

It is widely accepted that body weight and adipose mass are tightly regulated by homeostatic mechanisms, in which leptin plays a critical role through hypothalamic pathways, and obesity is a result of homeostatic disorder. However, in C57BL/6J mice, we found that Rcan2 increases food intake and plays an important role in the development of age- and diet-induced obesity through a leptin-independent mechanism. RCAN2 was initially identified as a thyroid hormone (T3)-responsive gene in human fibroblasts. Expression of RCAN2 is regulated by T3 through the PI3K-Akt/PKB-mTOR-Rps6kb1 signaling pathway. Intriguingly, both Rcan2(-/-) and Rps6kb1(-/-) mutations were reported to result in lean phenotypes in mice. In this study we compared the effects of these two mutations on growth and body weight in C57BL/6J mice. We observed reduced body weight and lower fat mass in both Rcan2(-/-) and Rps6kb1(-/-) mice compared to the wild-type mice, and we reported other differences unique to either the Rcan2(-/-) or Rps6kb1(-/-) mice. Firstly, loss of Rcan2 does not directly alter body length; however, Rcan2(-/-) mice exhibit reduced food intake. In contrast, Rps6kb1(-/-) mice exhibit abnormal embryonic development, which leads to smaller body size and reduced food intake in adulthood. Secondly, when fed a normal chow diet, Rcan2(-/-) mice weigh significantly more than Rps6kb1(-/-) mice, but both Rcan2(-/-) and Rps6kb1(-/-) mice develop similar amounts of epididymal fat. On a high-fat diet, Rcan2(-/-) mice gain body weight and fat mass at slower rates than Rps6kb1(-/-) mice. Finally, using the double-knockout mice (Rcan2(-/-) Rps6kb1(-/-)), we demonstrate that concurrent loss of Rcan2 and Rps6kb1 has an additive effect on body weight reduction in C57BL/6J mice. Our data suggest that Rcan2 and Rps6kb1 mutations both affect growth and body weight of mice, though likely through different mechanisms.

Construction of Finite Element Model for an Artificial Atlanto-Odontoid Joint Replacement and Analysis of Its Biomechanical Properties.

AIM: To investigate the stress distribution on artificial atlantoaxial-odontoid joint (AAOJ) components during flexion, extension, lateral bending and rotation of AAOJ model constructed with the finite element (FE) method. MATERIAL AND METHODS: Human cadaver specimens of normal AAOJ were CT scanned with 1 mm -thickness and transferred into Mimics software to reconstruct the three-dimensional models of AAOJ. These data were imported into Freeform software to place a AAOJ into a atlantoaxial model. With Ansys software, a geometric model of AAOJ was built. Perpendicular downward pressure of 40 N was applied to simulate gravity of a skull, then 1.53 N• m torque was exerted separately to simulate the range of motion of the model. RESULTS: An FE model of atlantoaxial joint after AAOJ replacement was constructed with a total of 103 053 units and 26 324 nodes. In flexion, extension, right lateral bending and right rotation, the AAOJ displacement was 1.109 mm, 3.31 mm, 0.528 mm, and 9.678 mm, respectively, and the range of motion was 1.6°, 5.1°, 4.6° and 22°. CONCLUSION: During all ROM, stress distribution of atlas-axis changed after AAOJ replacement indicating that AAOJ can offload stress. The stress distribution in the AAOJ can be successfully analyzed with the FE method.