Objective To evaluate the accuracy and reliability of O-arm-based thoracolumbar pedicle screw installation.Methods A retrospective review was conducted on 75 patients who had undergone thoracolumbar pedicle screw fixation assisted with O-arm navigation (navigation group,n =32) and C-arm fluoroscopy (fluoroscopy group,n =43) from March to October 2014.All the patients were assessed with X-ray and CT images after operation.Accuracy of screw installation in both groups was compared.In navigation group,screw directions were measured on the sagittal and axial images of intraoperative navigation and post-operative CT scanning to evaluate the concordance.Results In fluoroscopy group,a total of 206 pedicle screws were placed with the one-time success rate of 93.2％ and accuracy of 90.8％ for screw placement,and one misplaced screw (grade llⅢ) led to L3 nerve root symptom.In navigation group,a total of 226 pedicle screws were placed with the one-time success rate of 100％ and accuracy of 96.9％ for screw placement,and no screw was grade Ⅲ.Further,there were no significant differences in screw directions on the sagittal and axial images between intraoperative navigation and postoperative CT scanning (P ＞ 0.05).Conclusion O-arm navigation that provides high-resolution images and high precision improves the accuracy of thoracolumbar pedicle screw installation,and possesses good reliability.

Objective To construct genipin-crosslinked rat acellular spinal cord scaffolds and evaluate their enzymatic degradation rate,biomechanical properties and cytotoxicity.Methods Rat spinal cord scaffolds were decellularized by chemical extraction and chemically crosslinked with 5 g/L genipin solution.Micro-structure of the uncrosslinked and genipin-crosslinked acellular spinal cord scaffolds were observed by HE staining and scanning electron microscopy and properties of pore size,porosity,water ratio,and degradation rate in 2.5 g/L trypsin enzyme solution were examined.Ultimate tensile strength and elastic modulus of normal rat thoracic spinal cord,uncrosslinked and genipin-crosslinked acellular spinal cord scaffolds were determined on Instron mechanical testing instrument.Rat bone marrow mesenchymal stem cells were cultured in lixivium of uncrosslinked and genipin-crosslinked acellular spinal cord scaffolds and MTT assay for relative cell growth rate was test to evaluate the cytotoxicity of scaffolds.Results The uncrosslinked and the genipin-crosslinked acellular spinal cord scaffolds possessed a similar three-dimensional mesh-porous structure with a mean pore diameter about 30 μm and a porosity over 80％,but there was a statistical difference between the two groups(P ＞ 0.05).Water ratio of genipincrosslinked scaffolds was (229.7 ± 12.5) ％,far lower than (283.4 ± 11.2) ％ of uncrosslinked scaffolds (P ＜ O.05) ; genipin-crosslinked acellular spinal cord scaffolds had lower weight loss at each time point than the uncrosslinked acellular spinal cord scaffolds (P ＜ 0.05),but the stability in trypsin,ultimate tensile strength and elastic modulus of acellular spinal cord scaffolds were significantly enhanced by genipin-crosslinking (P ＜ 0.05).Furthermore,no obvious cytotoxicity was observed in the uncroslinked and genipin-crosslinked scaffolds.Conclusions Rat acellular spinal cord scaffolds present no obvious change in structure after genipin-crosslinking,but there is significant improvement in the biomechanical properties and ability against enzymatic degradation and no marked cytotoxicity.Hence,the genipincrosslinked scaffolds are promising in tissue engineering for spinal injury.

Objective To observe three-dimensional structure and biological features of rat acellular spinal cord scaffold prepared by sonic oscillation and chemical extraction in order to offer an ideal scaffold for spinal cord tissue engineering research.Methods Rat spinal cord underwent acellular treatment with sonic oscillation and chemical extraction (Triton X-100 at volume fracture of 2％ and sodium deoxycholate at volume fracture of 2％) (acellular spinal cord group).In contrast with spinal cord tissue of normal rats (control group),general morphology,histology and ultramicro three-dimensional structure of acellular spinal cord scaffold were observed and aperture size,factor of porosity,water ratio,enzymolysis ratio and stability in water solution of the scaffold were also detected.Results Acellular spinal cord group showed effective removal of original cell components with factor of porosity for (94.57 ±3.45) ％ and water content for (88.62 ± 1.0) ％,and satisfactory three-dimensional structure with average aperture of 46 μm.Scaffold showed gradual degradation in enzymolysis solution and enzymolysis rate reached (69.03 ± 2.19)％ at 20 hours.Besides,scaffold showed stepwise disintegration in double distilled water and hydrolysis rate was (62.55 ± 1.70) ％ at 8 days.While,normal spinal cord showed close structure,generous neurons and myelin sheath with factor of porosity for (0.04 ± 0.02) ％ and water content for (62.4 ± 1.5) ％,and unobvious pore structure under scanning electron microscope.Normal spinal cord were degraded gradually in enzymolysis solution and enzymolysis rate was (37.62 ± 0.9)％ at 20hours.In the meantime,normal spinal cord were disintegrated gradually in double distilled water and hydrolysis rate was (40.97 ± 0.81) ％ at 8 days.Conclusions Acellular spinal cord scaffold prepared by sonic oscillation plus chemical extraction achieves complete removal of cell components,intact extracellular matrix,and satisfactory results in three-dimensional network structures,factor of porosity and water content.Also,the scaffold meets theoretical demands of tissue-engineered spinal cord scaffold and is an ideal alterative for tissue-engineered spinal cord scaffold.

Objective To evaluate the clinical outcome of artificial cervical disc replacement and cage fusion in the treatment of multi-segmental cervical disc herniation. Methods A total of 39 patients with multi-level cervical disc herniation were treated with disc replacement and adjacent segment cage fusion at one stage. There were 29 patients with two level cervical disc herniation, nine with three level cervical disc herniation and one with four level cervical disc herniation. Of the patients, there were 17 male and 22 female, aged between 35 and 63 years ( mean age 47 years). The herniated disc was located at C3-4 and C4-5 in two patients, C4-5 and C5-6 in 15, C5-6 and C6-7 in nine, C4-5 and C6-7 in three, C3-4,C4-5 and C5-6 in four, C4-5, C5-6 and C6-7 in five and C3-4, C4-8 , C5-6 and C6-7 in one. There were 18 patients with myelopathy and 21 with radieulopathy. The stabilization and the range of motion of implanted disc,the fusion of cage and the displacement of cage were observed on dynamic radiograph postoperatively. The clinical symptom and the neurological function were evaluated according to JOA score and odom' s criteria. Postoperative clinical symptoms and daily function were evaluated by using neck disability index (NDI) scale. Results Twenty-nine patients with bi-level cervical disc herniation underwent single level disc replacement and cage fusion on adjacent segment. Nine patients with three level disc herniation underwent single level disc replacement in seven and level cage fusion on adjacent segment in two. Twopatients underwent two level disc replacement and one level cage fusion. One patient with four level disc herniation was treated with two level disc replacement and two level cage fusion. The patients were followed up for from 6 moths to 3 years, which showed that definite stabilization was achieved for all disc with average range of motion for 9.3 degrees postoperatively. Solid fusion was achieved in all cage, with no subsidence or displacement of cage. The JOA score was increased from 9.1 to 13.2 at final follow up and the NDI (neck disability index) score decreased from 41.8 reduced to 29.5 at final follow up. The clinical success rate (excellent/good/fair) according to Odom' s Criteria was 85%. Conclusion Cervical disc replacement and cage fusion can attain definite stabilization and satisfactory mobility and provide a new effective treatment for cervical disc herniation. The long-term outcome needs further clinical followup.

ObjectiveTo retrospectively analyze the treatment of odontoid fractures using percutaneous and open anterior screw fixation,and compare the clinical and radiographic results of the two techniques.MethodsFrom March 2003 to May 2010,115 patients with odontoid fracture were treated with anterior screw fixation,and all patients were followed up.The mean age of the patients was 43.5 years (range,16-71).Forty-seven patients who underwent percutaneous anterior screw fixation were set as the percutaneous fixation group,including 42 cases of type Ⅱ odontoid fracture and 5 of rostral type Ⅲ fracture.Sixtyeight patients who received open anterior screw fixation were set as the open fixation group,composing of 61cases of type Ⅱ odontoid fracture and 7 of rostral type Ⅲ fracture.We compared the operative time,intraoperative blood loss,X-ray exposure time,fracture union and complications between the two groups.Results The average follow-up duration was 37.6 months with a range of 12-70 months.The gender,age,classification of odontoid fractures,time after the injuries and concomitant spinal injuries showed a similar pattern in both groups.The operating time and intra-operative blood loss in percutaneous fixation group were (40.3±9.5)min and (5.6±4.1) ml respectively,and in open fixation group were (62.9±15.3) min and (47.1±28.6) ml respectively,both of them were significantly superior in percutaneous fixation group than in open fixation group (P＜0.05).There was no statistical difference in radiation exposure time,fracture union and incidence of complication between the two groups.ConclusionComparing with open screw fixation,percutaneous anterior screw fixation is a safe and reliable procedure for treatment of type Ⅱ and rostral type Ⅲ odontoid fractures with potential advantages.

Objective To explore the fixation method of tibial helical plate for treatment of proximal and middle one-third of humeral fractures and evaluate the clinical outcome. Methods A review was performed on 15 patients with proximal and middle one-third of humeral fractures treated by tibial helical plate from May 2004 to February 2009. There were 10 males and five females, at age range of 19-65 years ( average 38.0 years). The surgical method was summarized and the shoulder function evaluated.Results The follow-up lasted for 7-24 months (mean 13 months) , which showed bony union in all patients, with mean union time of 4.7 months. There was no implant loosening or failure. According to Neer 's criteria, the result was excellent in seven patients and good in six, with excellence rate of 86.7%.Conclusions Open reduction and internal fixation using tibial helical plate is simple and effective for treatment of proximal and middle one-third of humeral fractures.

Objective To explore feasibility and therapeutic effect of posterior decompression by vertebral body resection, interbody bone fusion and transpedicular screw internal fixation in treatment of severe rotational throracolumar fracture and dislocation. Methods From October 2007 to July 2008, nine patients with severe rotational throracolumar fracture and dislocation classified as AO C types under-went decompression by vertebral boby resection, intervertebral bone fusion and transpedicular screw inter-nal fixation via a posterior midline small incision. There were eight males and one female, at age range from 23 to 54 years. All patients involved levels at T_(11)-L_2. According to AO classification, there were three patients with type C1 bursting fractures with rotational dislocation, five with distraction fracture com-bined with rotational dislocation and one with rotational distraction shear fracture/dislocation. The preop-erative Frankel Grading was Grade A in three patients, Grade B in one, Grade C in four and Grade D in one. Postoperative neurological status, the correction and loss of dislocation and the location and union of bone graft were reviewed. Results All patients received successful operation, with operation time of 3.5-5.8 hours (mean 4.4 hours), blood loss of 1 200-3 500 ml (mean 1 800 ml). The follow- up period in nine patients was 3-12 months (mean seven months). Postoperative X-ray photographs showed that the dislocation in all patients was reduced, the spine curvature was recovered to normal and the intervertebral bone graft was well fixed. Three patients at Frankel Grade A had no improvement, one at Grade B was improved to Grade C. Of four patients at Grade C, three patients were improved to Grade D. The follow-up showed bony fusion in all patients, with no loosening, dislocation or breakage of the internal fixation or implants. Conclusions For severe rotational throracolumar fracture and dislocation, decompression, reduction, fusion and fixation are rather difficult, while sufficient posterior decompression by vertebral body resection, rigid interbody bone fusion and transpadicular screw internal fixation can be an effective alternative measure.

Objective To investigate the effects of transplantation of oligodendrocyte precursor cells (OPCs) on axonal myelination after spinal cord injury in a rat model. Methods A rat model of spinal cord injury at the tenth thoracic vertebral level (T10) was produced by Allen weight-drop impact method. OPCs implantation was performed at the subacute stage of spinal cord injury. Effects of OPCs transplantation on axonal myelination after spinal cord injury were evaluated by HE staining, immunohistochemistry, myelin staining and transmission electron microscopy. Results The implanted cells were still observed in lesioned segments of spinal cord eight weeks after transplantation. The results of HE staining clearly showed better structure of spinal cord in OPCs-transplanted group than that of control group.Myelin staining also demonstrated that the amount of myelin in white matter of lesioned cord in the OPCs-transplanted group (7 802.42 ± 1085.58) was higher than that of the control group (5 055.98 ± 916.74)(P ＜0.01 ). Expression of myelin basic protein (MBP) was significantly increased in the OPCs-trans-planted group (8 544.44 ±812.78) as compared with that of the control group (5 243.83 ±808.27)(P＜0.01). Moreover, transmission electron microscopy further confirmed the improvement of micro-structure of myelination in OPCs-treated rats. Conclusion OPCs transplantation can improve axonal myelination in rat with spinal cord injury.

Objective To evaluate the in vitro biological safety of acellular spinal cord scaffold so as to provide theoretical basis for constructing the ideal tissue engineering scaffold of spinal cord.Methods A piece of thoracic spinal cord for 2 cm removed from SD rats was harvested and then was treated by freezing and thawing and chemical extraction with 3% sodium deoxyeholate and 1 KU/ml DNaseI and RNaseA. Gross observation and histological examination of the acellular spinal cord scaffold were carried out to learn the condition of the extracellular matrix scaffold. The biological safety of the acellular spinal cord scaffold was evaluated. Results In cross section, network of the extracellular matrix was presented in the scaffold. The cells, myelin and axons disappeared after the spinal cord was treated with sodium deoxycholate, DNaseI and RNaseA. Typical network of empty tubes were viewed in longitudinal sections. General toxic reaction, pyrogen test, hemolysis test and cytotoxicity test were conforming to the standard of materials. Conclusion As neotype tissue engineering material, the acellular spinal cord scaffold has satisfactory biological safety.

Objective To study the indications and clinical outcome of the upper cervical spine via the high anterior cervical retropharyngeal approach in treatment of upper cervical spine injuries. Methods There were 41 patients including 32 males and 9 females, at age of 12-67 years. Of all patients, there were 21 patients with Hangman fractures, two with fracture of C2 vertebral body, 12 with irreducible atlantoaxial dislocation secondary to os odontoideum, four with C1,2 tuberculosis and two with C2 gaint cell tumor. All patients underwent the high anterior cervical retropharyngeal approach to expose C1C3. C2,3 fusion followed by self-locking plate was performed for Hangman fractures and C2 fractures. Ventral reduction plud posterior aflantoaxial fusion was done for irreducible atlantoaxial dislocation secondary to os odontoideum. Lesion was cleared for tuberculosis and the tumor was resected and reconstructed. The neurological funcation was evaluated according to the ASIA criteria, the JOA score and Odom' s criteria. Results Successful exposure of arch of atlas to C3 was achived in all 41 patients, with satisfactory reducation, decompression, fusion, lesion resection and reconstruction. The trauma patients with normal neurological function showed no neurological deficit postoperatively, but those with quadriparesis had partial recovery. While the patients with illness obtained marked recovery of neurological function, with the JOA score from preoperative 8.9 to 12.5 at final follow-up. The clinical success rate (excellent/good/fair) reached 94. % according to Odom' s Criteria. Hypoglossal symptom was found in three patients and facial nerve symptom in two, without wound infection. Conclusions Via the high anterior cervical retropharyngeal approach, the upper cervical spine can be thoroughly exposed to facilitate reduction, decompression and reconstruction and maximally restore physiological function of the cervical spine in treatment of the upper cervical spine injuries.