Low back pain is an important cause of disability worldwide. It has a high incidence rate and brings a huge burden to families and society. Intervertebral disc degeneration (IDD) is one of the leading factors causing low back pain and the pathological basis of degenerative disc diseases, such as intervertebral disc herniation and spinal stenosis. However, the etiology of IDD is complex, and the risk factors and specific mechanisms behind remain unclear. Some controversial views have also been observed. Surgery is often considered for patients with severe intervertebral disc diseases, but there is no effective treatment for IDD at the early and middle stages. It will be of great significance to in-depth explore the molecular biological mechanisms and related risk factors, which can bring benefits to the prevention, accurate diagnosis, early treatment, and rehabilitation of degenerative disc diseases. Refer to the literatures published in the past ten years, this paper describes the latest research progress on risk factors related to IDD in terms of aging, genetics, mechanical loading, low-grade infection, biological rhythms, smoking, metabolic disease, estrogen, and nutrition. The results show that IDD is affected by multiple risk factors. These factors can interact with each other, and lead to death, phenotypic transformation, and metabolic disorder of disc cells, leading to a reduction of extracellular matrix and an unbalanced microenvironment and eventually loss of structural integrity of intervertebral disc tissue and IDD. A good body clock, a controlled weight, an appropriate blood glucose level, adequate nutrition, no smoking, a good hormone level, moderate exercise, avoiding injury, and strict aseptic techniques in the clinic will bring benefits to the progress of IDD.

Objective To observe the solo-allied expression of Survivin, Smad4/dpc4 and APC gene, and study the relationship between the three genes and biological behavior of colorectal cancer. Methods The expressions of Survivin, Smad4/dpc4 and APC gene were detected by SP immunohistochem-istry among the cases from 40 eu-intestine ,80 large intestinal adenoma and 80 CRC. Results The positive rate of survivin protein in the eu-intestine, the large intestinal adenoma and CRC was 0,35.0% ,75.0% , respectively. The positive rate of Smad4/dpc4 protein was 100% , 95. 0% , 78. 8% , and the positive rate of APC protein was 100% ,80.0% ,45.0% , respectively. In the eu-intestine, APC + Smad4/dpc4 Z- expressed in 40 cases, with the incidence of 100%. In the large intestinal adenoma, APC + Smad4 expressed in 38 patients, with the incidence of 47. 5% , and the three genes expressed in 29 patients with the incidence of 23. 8%. In the CRC, two genes expressed in 57 patients, with the incidence of 71. 3% , and three genes expressed in 28 patients, with the incidence of 35.0%. Conclusion The detection of survivin was a new indicator in early diagnosis of CRC. It was significant in the diagnosis of CRC that energetic search for the positive rate level realm of survivin. The catastrophe or absence of Smad4/dpc4 gene not only induced the genesis of CRC but also encouraged its growth. Smad4/dpc4 was ant- carcinomatous gene intimately correlated to the CRC. Detection of APC gene had very important significance, it could be helpful to conduct the research of tumorous aetiology, nosogenesis and early diagnosis. The allied detection of Survivin, Smad4/dpc4, APC gene played a very important role in early diagnosing and healing the CRC.

Objective To investigate the risk factors and preventive measures for acute epidural hematoma after posterior thoracic spine surgery.Methods A retrospective study of 14 patients who developed acute epidural hematoma after thoracic spine surgery from May 2002 to May 2012 was conducted.There were 6 males and 8 females,aged from 41 to 69 years (average,61.2 years).There were 10 cases of thoracic spinal canal stenosis,3 cases of thoracic spinal meningioma,and 1 case of thoracic metastasis.About 3-14 h (average,6.6 h) after posterior thoracic spine surgery,the neurological deterioration was found,and according to the American Spinal Injury Association (ASIA) classification,there were 5 cases of grade A and 9 cases of grade B.The neurological function before evacuation of hematoma was compared with that after evacuation of hematoma and that at final follow-up.The correlations between hematoma compression time,neurological improvement rate and neurological function before evacuation of hematoma were statistically analyzed.Results After evacuation of hematoma,the ASIA classification of 14 patients was as follows:grade B in 1 case,grade C in 2 cases,grade D in 4 cases,and grade E in 7 cases.The hematoma compression time of 3 patients with grade B or C was more than 10 hours.Obvious difference of neurological function was found before and after evacuation of hematoma.The neurological improvement rate was 63.7％±23.3％ after evacuation of hematoma,which was negatively correlated with hematoma compression time and positively correlated with preoperative neurological function.The neurological function before evacuation of hematoma was significantly different from that at final follow-up.The neurological improvement rate was 86.97％±17.58％ at final follow-up,which was negatively correlated with hematoma compression time and positively correlated with preoperative neurological function.Conclusion The acute epidural hematoma after thoracic spine surgery could cause severe neurological deterioration.The neurological improvement was negatively correlated with hematoma compression time.Evacuation of hematoma must be done as soon as possible once progressive neurological deterioration is found.

Exosomes are vesicles with a double globular membrane of lipids that can be secreted by a variety of cells, including stem cells. Exosomes have unique biological characteristics and irreplaceable powerful functions which play an important role in intercellular communication. The various cytokines, signal proteins, lipids and regulatory nucleic acids contained in stem cell exosomes can play a protective role against the injury of kidney, liver, heart, blood vessels and nerves. Stem cell exosomes delay the process of intervertebral disc degeneration by inhibiting the apoptosis of nucleus pulposus cells and increasing the synthesis of extracellular matrix, etc. The mechanism of its role is mainly through miRNA and related signaling pathways. Exosomes contain complex components. Although the mechanism of action of exosomes in intervertebral discs has been preliminarily explored, the components contained in exosomes are complex and the specific situation has not been fully understood, which still needs further study. In this review, the characteristics and functions of stem cell exosomes, extraction, identification and storage methods, the impacttovarious other tissues, as well as the effects on intervertebral discs and their mechanisms were elaborated in order to provide a basis for the study of intervertebral disc degenerative diseases.

Objective:To evaluate the volume changes of cervical longus and cervical extensor after anterior cervical discectomy and fusion (ACDF), and the correlation with the clinical efficacy of patients.Methods:All of 57 patients with cervical spondylotic myelopathy who underwent single-segment ACDF surgery from January 2013 to December 2018 were analyzed. The follow-up time was 23.0±4.8 months (range 16-34 months). All included subjects underwent MR examination within 1 week before operation and 3rd, 12th months after operation and at the last follow-up. The axial section cross section area (AxCSA) of the cervical longus and the ratio of length to short diameter line (RLS) at the level of each disc of C 2-C 7 were measured on the axial T2WI. Calculate the volume of the cervical longus based on the layer thickness. At the same time, measure the cervical extensor cross-sectional area (CESA) of the same level including the multifidus, cervical semispinous muscle, semispinous head, splinter head, and cervical splinter muscles, and compare CESA with the corresponding vertebral cross-sectional area (VBA). The ratio is analyzed as the volume of the neck extensor muscle, namely CESA/VBA. At the 3rd and 12th months after operation and at the last follow-up, the axial pain was assessed by visual analogue scale (VAS) for assessing pain, and the modified Japanese Orthopedic Association score (mJOA) and the neck dysfunction index (NDI) were used to assess the functional status of the cervical spine. Analyze the morphological changes of thecervical longus and extensor cervical muscles before and after the operation and during the follow-up period, and analyze the correlation with VAS, mJOA, and NDI. Results:Compared with the preoperative period, the average AxCSA of the surgical segment decreased at the 3rd and 12th months after the operation and at the last follow-up. The difference was statistically significant ( F=24.113, P<0.05), which was changed from 140.84±19.51 mm 2 respectively reduce to 117.74±17.15 mm 2 ( t=6.714, P<0.05), 116.37±18.67 mm 2 ( t=6.841, P<0.05) and 116.27±18.65 mm 2 ( t=6.873, P<0.05). Compared with preoperatively, they were reduced by 16.40%, 17.37% and 17.45%, respectively, while the average RLS of surgical segments increased slightly, and the difference was statistically significant ( F=22.612, P<0.05), which increased from preoperative 1.97±0.67 to 2.73±0.60 (38.58% increased, t=6.380, P<0.05), 2.82±0.64 (43.15% increased, t=6.926, P<0.05) and 2.74±0.62 (39.09% increased, t=6.368, P<0.05). The volume of thecervical longus of the patients decreased after the operation, and the difference was statistically significant ( F=64.511, P<0.05), which decreased from 8853.48±458.65 mm 3 before the operation to 7834.53±461.59 mm 3 (11.51% decreased, t=11.822, P<0.05), 7926.42±456.24 mm 3 (10.47% decreased, t=10.819, P<0.05), 7892.38±450.78 mm 3 (10.86% decreased, t=11.283, P<0.05). There were no statistically significant differences in the non-surgical segment AxCSA, RLS and the volume of thecervical longus at the 3rd and 12th months after surgery and the last follow-up ( P>0.05). There was no statistically significant difference of CESA and CESA/VBA compared to preoperative in the surgical segment and non-surgical segment ( P>0.05). Pearson correlation analysis showed that the volume of cervical longus and VAS at the 3rd month ( r=-0.308, P<0.05), the 12th month ( r=-0.210, P<0.05) and the last follow-up ( r=-0.404, P<0.05) were negatively correlated; Among the volume of cervical longus and NDI in the 3rd month ( r=-0.511, P<0.05), 12th month ( r=-0.518, P<0.05) and the last follow-up ( r=-0.352, P<0.05), there was a negative correlation; However, there was no statistically significant correlation between the cervical longus muscle volume and mJOA at each follow-up time point ( P>0.05); There was no significant correlation between CESA/VBA and VAS, NDI, and mJOA at the 3rd, 12th and last follow-up ( P>0.05). Conclusion:The volume and morphology of cervical longus after ACDF was significantly reduced compared with that before the operation, but the volume and morphology of the cervical extensor muscle did not change significantly. ACDF surgery mainly affects the cervical longus corresponding to the surgical segment, and the volume is negatively correlated with the VAS and NDI during follow-up.

Objective:To investigate the effects of exosomes of human nucleus pulposus cells (NPCs) on the differentiation of urine derived stem cells (USCs) into nucleus pulposus-like cells.Methods:USCs and NPCs were isolated and cultured in vitro. The exosomes of NPCs were extracted and detected by Western-blot. USCs cytoplasm was transfected with GFP lentivirus, while nucleus was transfected with DAPI dye. The NPCs exosomes were transfected with PKH26 dye. After co-incubation for 12 h, USCs and NPCs exosomes were observed by macroscopy. USCs differentiation was induced by NPCs exosomes and non-contact co-culture methods. The relative expression of marker gene mRNA of nucleus pulposus cells in each group and the absorbance at 450 nm wavelength were detected.Results:The isolated USCs had the ability to differentiate into osteocytes, adipocytes and chondrocytes with high expression of marker CD29 (99.57%), CD44 (97.46%) and CD73 (97.71%) and with low expression of negative proteins CD31 (0.59%) and CD45 (0.19%). The isolated NPCs highly expressed nuclear pulposus cell marker COL2A1, ACAN and SOX-9. The exosomes extracted from NPCs showed high expression of exosome marker CD63, CD81 and Tsg101. After 12 h co-incubation, NPCs exosomes fused with USCs membrane and appeared in the cytoplasm of USCs. At 3, 5 and 7 days of co-culture, the absorbance value of USCs cells in exosome group (0.44±0.004, 0.76±0.004, 0.82±0.006) was higher than that in co-culture group (0.39±0.022, 0.63±0.035, 0.69±0.012) ( P<0.05). The mRNA relative expression of USCs nucleus pulposus marker genes ACAN (1.80±0.31, 3.50±0.21, 5.35±0.31, 7.46±0.12), COL2A1 (1.43±0.15, 4.33±0.23, 6.89±0.22, 8.11±0.31), SOX-9 (2.21±0.13, 3.13±0.11, 3.96± 0.14, 4.52±0.26) and HIF-1α (1.45±0.16, 2.14±0.21, 4.31±0.41, 4.01±0.25) in exosomes group were significantly higher than those in the control group ( P<0.05) at the 3rd, 7th, 14th and 21st days. The mRNA relative expression of USCs nucleus pulposus marker genes ACAN (5.69±0.21, 6.69±0.13), COL2A1 (6.33±0.17, 7.89±0.15), SOX-9 (4.19±0.29, 4.38±0.12), HIF-1α (4.49±0.32, 4.96±0.26) in exosomes group were significantly higher than those ACAN (3.69±0.35, 5.13±0.23), COL2A1 (3.40±0.16, 6.79±0.19), SOX-9 (2.26±0.32, 3.69±0.26), HIF-1α (2.39±0.11, 3.96±0.13) in non-contact co-culture group ( P<0.05) at the 14th and 21st days. Conclusion:Human nucleus pulposus exosomes could induce differentiation of human USCs into nucleus pulposus-like cells in vitro. Compared with non-contact co-culture, exosomes have higher induction efficiency and can better maintain the proliferation activity of nucleus pulposus-like cells

Objective To explore influences of the taper and connecting rib form on supporting performance of the stent, and provide an important scientific basis for structural design and clinical selection of the tapered stent. Methods A nonlinear finite element model for radial support performance of a novel balloon-expandable tapered stent was constructed, and the radial stiffness (RS) and stress distributions of the stent at different tapers (0°, 0.565°and 1.13°) and with different structural forms of stent linker (V-shape, I-shape, C-shape, S-shape, M-shape) were analyzed by plane compression. The relationship between structural design of the vascular stent and its radial support performance was studied. Results The RS of 0°stent, 0.565°stent, 1.13° stent was 2.51, 1.61, 0.85 N/mm, respectively. The RS of 0.565°stent and 1.13° stent was 35.86% and 66.14% lower than that of 0°stent (round straight stent), respectively. Except that the RS of C-shape linker stent was 1.48 N/mm, the RS of I, M, S and V-shape linker stents was not significantly different, which was 2.51, 2.61, 2.41, 2.52 N/mm, respectively, indicating that radial compression resistance of these four linker stents was almost the same. Conclusions Compared with traditional round straight stents, the RS of tapered stents will decrease, and the RS of stents will gradually decrease with the the taper increasing. Among all stent types in this study, except C-shape linker stents, the RS of other linker shapes has little effect on the RS of stents. The radial support performance of the stent can be improved by reducing the taper of the tapered stent, without changing the form of stent connecting ribs.

Objective:To explore the effect of minimally invasivetransforaminal lumbar interbody fusion (MIS-TLIF) on lumbar multifidus muscle using MRI techniqueandits clinical significance.Methods:From September 2016 to July 2019, 23 patients who underwent MIS-TLIF surgery for unilateral symptomatic disc herniation in unilateral segments (L 3,4, L 4,5, L 5S 1) of Qingdao University Affiliated Hospital were studied. Their lumbar MR examination was performed 1 week before surgery, and 3 and 6 months after surgery. The axial section of multifidus muscle cross section area (AxCSA) was measured on the axial T2WI image of each intervertebral disc level before and after the operation. The ratio of long and short lines (RLS) was calculated, andthe ratio of axial section of muscle fat infiltration cross section area (FLSA) and AxCSAwasrecorded as FLSA/AxCSA. The changes of various indexes of multifidus muscle in the affected side and the healthy side of the lumbar spine before and after the operation were compared, and the effect of the MIS-TLIF procedure on the morphology of the multifidus muscle was observed. Magnetic resonance spectroscopy (MRS) measurements of the muscle cross-section of the affected side were performed before and 6 months after the operation. The integral value of intracellular lipid (IMCL) and extracellular lipid (EMCL) of 1H spectrum muscle cells was compared, while the degree of fat infiltration was measured. Results:Patients with single-segment lumbar disc herniation had larger AxCSAin the healthy side than the affected side before surgery in surgical level ( t=6.611, P<0.05), and the muscle AxCSAin the healthy side was larger than the affected side in non-surgical levels ( t=-6.682, P<0.05), both suggested preoperative muscle volume advantage in the healthy side; no difference in bilateral AxCSA at 3 months was found after surgeryin surgical levels ( t=0.197, P> 0.05)and non-surgical levels ( t=-1.631, P> 0.05), which suggested bilateral muscle volume equal advantageat short-term follow-up. The FLSA/AxCSA of affected segment before and after 3 months was 9.5%±3.8% and 8.7%±1.5%, and the difference was statistically significant ( t=3.163, P<0.05); the RLS of affected segment before and after 3 months was 3.3%±0.24% and 2.7%±0.83%, and the difference was statistically significant ( t=3.42, P<0.05). The medians of EMCL/IMCL before and after 6 months of MRS were 2.010 and 1.475, respectively, and EMCL decreased after 6 months ( Z=0.48, P<0.05). Conclusion:Patients with single-segment lumbar disc herniation have different morphology of bilateral multifidus muscle before surgery. MIS-TLIF has little effect on the multifidus muscle of the surgical side. MIS-TLIF significantly reduces extracellular lipid accumulation, promotes intracellular transfer, and increases intracellular fat metabolism. Its retention of muscle attachment points and limited fixation can also reshape compensatory muscle atrophy.

Objective To explore the management strategy and indications for revisionary internal fixation after percutaneous kyphoplasty/percutaneous vertebroplasty (PKP/PVP) in cancellous vertebral fractures.Methods A retrospective analysis was made of the 676 cases of single-segment PKP/PVP at Department of Orthopaedics,The Affiliated Hospital to Qingdao University from January 2008 to January 2019.They were subjected to 4 different managements after their primary PKP/PVP:rehabilitation without any treatment in 637 cases,conservative treatment in 19 cases (including 3 ones who refused any revision),KP/VP revision in 12 cases and internal fixation revision in 8 cases.The rate of volume reduction after bone cement dispersion (Vx) was calculated using software Mimics 17.0 on the basis of primary CT data of all the patients.The correlation regression analysis was made between the revision rate and the approximate quantization value of Vx.The Glasgow Coma Score (GCS) of conscious state was used to evaluate the 39 patients after failure of their primary surgery before the surgical strategy for revision was worked out.The cobb angle,pelvic incidence angle (PI),pelvic inclination angle (PT),sacral inclination angle (SS),sagittal deviation (SVA),pain visual analogue scale (VAS) were measured and recorded before operation and at the last follow-up for the KP/VP revision group and internal fixation revision group,indicated as △cobb,△PI,△PT,△SS,△SVA and △VAS,respectively.The indexes were compared between the 2 groups.Results The incidence of osteoporotic vertebral fractures treated with internal fixation revision was 1.18％ (8/676).The correlation between Vx and revision rate was y =0.53 + 0.04x (P ＜ 0.05).The regression analysis showed that Vx was positively correlated with the revision rate (r2 =0.860,P =0.001) and the fitting curve was correlated (r2 =0.916,P =0.001).The GSC scores revealed 31 normal,6 mild disturbance and 2 moderate disturbance cases.There were no significant differences in gender,age or VAS scores between the KP/VP revision group and the internal fixation revision group (P ＞ 0.05).There was a significant difference in △cobb between the 2 revision groups (6.3° ± 7.5° versus 19.2° ± 14.8°) (P ＜0.05),but there were no significant differences between the 2 groups in △PI (4.1°±5.2° versus 3.3°±6.7°),△PT (0.7°±4.6° versus 0.4° ± 3.2°),△SS (3.7° ± 6.2° versus 3.1° ± 5.3°) or △SVA (-3.2 ± 11.9 mm versus-7.9 ± 9.5 mm) (P ＞ 0.05).Conclusions The outcomes of primary PKP/PVP have a great impact on the decision-making of internal fixation revision.The mode and extent of diffusion after initial vertebral cement perfusion are particularly related to the revision rate.The revision plan should depend on clinical symptoms.The internal fixation revision should be individualized to ensure the quality of life of the patients in line with the principles of "resolving symptoms" and "moderate correction".

BACKGROUNDThe objective of this study was to use three-dimensional finite element (FE) models to analyze the stability and the biomechanics of two upper cervical fixation methods: the C2 intralaminar screw method and the C2 pedicle screw method.

METHODSFrom computed tomography images, a nonlinear three-dimensional FE model from C0 (occiput) to C3 was developed with anatomic detail. The C2 intralaminar screw and the C2 pedicle screw systems were added to the model, in parallel to establish the interlaminar model and the pedicle model. The two models were operated with all possible states of motion and physiological loads to simulate normal movement.

RESULTSBoth the C2 intralaminar screw method and the C2 pedicle screw method significantly reduced motion compared with the intact model. There were no statistically significant differences between the two methods. The Von Mises stresses of the internal and external laminar walls were similar between the two methods. Stability was also similar.

CONCLUSIONSThe C2 intralaminar screw method can complement but cannot completely replace the C2 pedicle screw method. Clinicians would need to assess and decide which approach to adopt for the best therapeutic effect.