BACKGROUND: With the fast development of computer technology,biomechanical study of cervical vertebra is not limited in animal or human corpses,because computer model can provide a more accurate model.OBJECTIVE: To develop a three-dimensional,finite element model of a human C2-7 based on previous studies,and to provide experimental data for the biomechanical study of the cervical spine.METHODS: A normal young 28-year-old male,without obvious cervical spondylosis history,was selected,and C-spine X-rays at posteroanterior,oblique,and over extension and over flexion position were performed to deplete cervical spondylosis.The CT scanning images were dealed with Software Mimics and Geomagic to obtain the finite element,and software ANSYS was used to study the response of the model.Under a 1.8 N·m segmenal movement and force displacement response were observed and compared with abroad experimental results.RESULTS AND CONCLUSION: The new finite element model was composed of six vertebrae(C2-7),five discs(C2/3-6/7)and main ligaments.The model consisted of solid elements with 23 348 nodes and 215 749 units.The results of the biomechanical study were better correlated with the available experimental data.It indicates that the finite element model of cervical spine at C2-7 can be used to imitate the biomechanical experiment of cervical spine.

Objective To report a newly designed method of cervical subtotal corpectomy with the posterior vertebral wall retention. Methods 89 cases of cervical spondylotic myelopathy(CSM) or cervical injury were treated with subtotal corpectomy with the posterior vertebral wall retention from March 2001 to March 2004. 61 males and 28 females, aged from 25 to 76 years(mean, 47 years) were included, which involved 62 cases of multiple level in CSM with or without radiculopathy, 14 fractures of cervical vertebral body with or without cervical dislocation, 13 cervical instability with or without cervical disc disease. Subtotal corpectomy with 2 mm retention in posterior wall of the vertebral body were performed, in which 23 cases' level were C4,55 C5 and 11 C6. Extensive decompression through intervertebral body space was performed and bone fusion with autogenous iliac bone graft or titanium mesh supplemented with anterior locking plates were used, the bone graft or mesh were impacted into the decompression slot between the upper to lower endplate as well as the preserved lateral and posterior wall stably. Bone fusion were assessed with roentgenogram during the 3rd, 6th, 12th month follow-up and neurological function was recorded. Results The average operation time is 100 min, ranged from 55-130 min, the blood loss were 120 ml, ranged from 30 to 300 ml. Neither plate or screw migration, nor bone graft loosening or subsidence were found in 77 patients with over 6 months follow-up. Bone fusion happened in all patients, and Frankel score improved 1.0 level averagely after operation. 3 patients with hoarseness recovered 2 weeks later. Conclusion Subtotal corpectomy with posterior wall of vertebrae retention was a feasible anterior decompression procedure with advantage of safety, completely decompression and reliable bone fusion. This method included double level of CSM, and cervical fracture as well as two level of local ossification of posterior longitudinal ligament.

L3、4,and there was no significatant difference between two sides,and the biggest inner diameter of the main vessels averaged 5.3?0.6 mm.[Conclusion]To begin with,the blood supply is adequate in the intertransverse area,and the distribution of blood vessels follows some regularities,so to be familiar with the anatomy and to operate carefully can reduce bleeding.In addition,ILIF in segment L3、4 and L4、5 is feasible.

Objective To report the clinical outcome of L3～L5 fractures treated with USS short segmental pedicel screw system. Methods From 1994 to 2004, 57 cases of lower lumbar fractures were treated, of which 21 cases were treated with USS pedicel screw system. There were 12 cases of L3 fracture, 8 cases of L4 fracture and 1 cases of L5 fracture. The intervertebral height and lumbar lordosis were evaluated both before and after operation, the spinal impingement of bone was evaluated on CT scan, the neurofunction was evaluated with Frankle system and the clinical outcomes were evaluated with Charles system. Results The operation time ranged from 90 min to 150 min, averaging 120 min. The bleeding volume ranged from 100 ml to 600 ml, averaging 350 ml. The Frankle scores increased from 3.7 to 4.5 after operation. The intervertebral height of the fractured vertebral body increased from preoperative 30%to 60%to postoperative 70%to 100%(averaging 87%). The lumbar lordosis angel increased from preoperative 35.2?8.3o to postoperative 38.3?10.2o. The mobilization time was 3d to 2w, and the time for resuming work was 3 to 6w. The 3 to 30 months follow ups (averaging 15m) showed that the clinical outcomes were excellent in 9 cases, good in 9 cases, fair in 2 in and poor in 1. Conclusion The advantages of treating the lower lumbar fractures with short segmental USS pedicel screw system are effective restoration of intervertebral body height, lumbar lordosis and spinal volume, prevention of long term lumbago and lumbar stenosis, as well as early mobilization and return to work.

Objective To investigate incidence,diagnosis and treatment strategy of delayed esophageal complications after anterior cervical spine surgery.Methods The clinical data of 2316 patients who had undergone anterior cervical spine surgery from January 2001 to December 2011 were analyzed.The delayed esophageal complications were defined as esophageal perforation,esophago-tracheal fistula,esophago-cutaneous fistula,diverticulum of esophagus,esophagopleural fistula and esophageal stenosis that occurred 2 weeks after spine surgery.Results Delayed esophageal complications occurred in 4 patients,and the incidence was 0.17％.Esophageal perforation occurred in 2 patients; the incidence was 0.09％.Case 1 was a 31-year-old man who was found to have esophageal diverticulum and perforation 7 years after anterior cervical spine surgery.Then he underwent removal of implant,excision of diverticulum,and repair of esophagus with sternohyoid muscle flap and omohyoid muscle flap.Case 2 was a 46-year-old man who was found to have esophageal diverticulum 3 years after cervical spine surgery.He also underwent removal of implant,excision of diverticulum,and repair of esophagus with sternohyoid muscle flap and omohyoid muscle flap.Case 3 was a 58-year-old woman who was found to have esophageal diverticulum 5 years after cervical spine surgery.She underwent removal of implant,excision of diverticulum,and repair of esophagus with sternocleidomastoid muscle flap.Case 4 was a 56-year-old woman who was found to have esophageal perforation 3 years after cervical spine surgery.She underwent removal of implant and repair of esophagus with sternocleidomastoid muscle flap.All 4 patients recovered after operation.Conclusion The incidence of delayed esophageal complications after anterior cervical spine surgery is low,and the diagnosis is difficult.X-ray,digestive tract radiography,and gastrointestinal endoscopy are the main diagnostic tools.Surgical treatment is the main and effective management.

BACKGROUND:Poly-D,L-lactic-co-glycolic acid (PLGA) that was characterized as absorbable,weak cytotoxicity,and adjustable hardness was ideal to be synthetized artificial spinal dura mater.Because of lacking of functional group at the surface of PLGA,it should be modified to fit the demand of satisfied biocompatibility.OBJECTIVE:To study the biocompatibility of PLGA membrane modified by type-Ⅰ collagen and chitosan.DESIGN,TIME AND SETTING:Contrast observation study,which was carded out in the Biochemistry and Molecular Biology Laboratory Shanghai University of Traditional Chinese Medicine from May to December 2007.MATERIALS:Porous PLGA membrane was provided by Jinan Banzheng Biology-Technology Co.,Ltd.,type-Ⅰ collagen by Sigma Company,USA,chitosan by Shanghai Qisheng Biological Agent Medical Apparatus and Instrument Company,and L929 L cell by Cellular Institute of Shanghai Academy of Life Science,Chinese Academy of Science.METHODS:PLGA membrane (P membrane),PLGA/type-Ⅰ collagen composite membrane (PG membrane),PLGA/type-Ⅰ collagen/chitosan (9:1) composite membrane (PGC 9:1 membrane) and PLGA/type-Ⅰ collagen/chitosan (5:5) composite membrane (PGC 5:5 membrane) were produced through a certain process.MAIN OUTCOME MEASURES:Contact angle,absorption rate and cytotoxicity were tested.Morphological changes of L929 L cell cultured for 1,3,and 7 days were observed under fiberscope.RESULTS:Contact angle was shown as PG membrane＜PGC 9:1 membrane＜PGC 5:5 membrane＜P membrane (P＜0.01 );absorption rate was shown as P membrane＜PGC 5:5 membrane＜PGC 9:1 membrane＜PG membrane (P＜0.01).L929 L cell was characterized as well distribution,expansion and appearance after inoculation of PG membrane,PGC 9:1 membrane and PGC 5:5 membrane.Cytotoxic experiment (MTT methods) showed that,on the 1st day,there was no significant difference in absorbency among groups (P＞0.05).On the 3rd and 7th days,there were significant differences between P membrane and PG membrane or PGC 9:1 membrane,and between PGC 9:1 membrane and PCK2 5:5 membrane (P＜0.05).PGC 9:1 membrane could further improve cell adhesion and proliferation,and PGC 5:5 membrane could inhibit cell proliferation and differentiation.CONCLUSION:Type-Ⅰ collagen and chitosan appended to the exterior of PLGA can enhance the biocompatibility of membrane.In terms of biocompatibility,PLGA/type-Ⅰ collagen/chitosan (9:1) composite membrane can be fit to the qualification as a type of material of artificial spinal dura mater.

BACKGROUND:As a traditional treatment for multilevel cervical myelopathy,nterior long-segmental decompression has the shortcomings of great operative trauma,high difficulty,low fusion rate,etc.,which can affect the postoperative efficacy.OBJ ECTIVE:To evaluate the clinical effects of three different anterior surgeries on multilevel cervical myelopathy.DESIGN:A comparative observation.SETTING:Department of Orthopaedics,Changzheog Hospital,the Second Military Medical University of Chinese PLA.PARTICIPANTS:Thirty-six patients with multilevel cervical myelopathy of 3 consecutive segments,who were surgically treated,were selected from the Department of Orthopaedics,Changzheng Hospital,the Second Military Medical University of Chinese PLA from June 1999 to June 2003,including 25 males and 11 females,35-62 years of age,the disease course ranged from 3 to 26 months. According to the clinical manifestations and imaging esults,they were diagnosed as multilevel cervical myelopathy,and they were not suffering from consecutive ossification of posterior longitudinal ligament and ossification of ligamenta flava. Informed contents were obtained from all the patients and their relatives.METHODS:All the patients were grafted with utologous bone. Autologous ilium or cancellous bone excluding vertebral body was filled into titan net or Cage,which were made of titan and characterized by high intensity,tolerance to decay,good biocompatibility,etc. According to the operative manner,the patients were divided into 3 groups:① two-level corpectomy with fusion group(long-segmental decompression group,n =11):There were 4 cases grafted with long-titan net,and 7 cases grafted with autologous iliac bone. Sub-total two-level corpectomy with fusion was performed. ②segmental decompression group(n =16):including 12 cases of titan net+cage graft,4 cases of autologous bone+cage graft. One-level decompression and sub-total single corpectomy with fusion were performed. ③three-level decompression group(n =9):Only discectomy without corpectomy was performed. After complete decompression,3cages were used to fill artificial bone or grafted with autologous bone.MAIN OUTCOME MEASURES:Cervical anteroposterior and lateral radiographies,flexion and extension radiograph were reexamined within 1 week and at 3,6 and 12 months postoperatively. The neurological function was assessed using the Japanese Orthopaedic Association(JOA) scoring method preoperatively and 3 months postoperatively. The total score was 17 points,the higher the score,the better the neurological function. The duration of operation,perioperative bleeding amount,length of stay,cost of hospitalization,graft fusion at 3 months postoperatively,improved JOA score at 3 months postoperatively were recorded in the three groups. The occurrence of postoperative complications was observed by means of return visit.RESULTS:All the 36 patients with multilevel cervical myelopathy were involved in the analysis of results. The mean duration of operation,mean perioperative bleeding amount and mean length of stay in the segmental-decompression group and three-level decompression group were obviously fewer or shorter than those in the long-segmental decompression group(P ＜ 0.05),and the average cost of hospitalization was obviously higher than that in the long-segmental decompression group(P ＜ 0.05). The postoperative improved JOA score and graft fusion rate were close among the groups(P ＞ 0.05).CONCLUSION:Segmental anterior cervical decompression is a recommendable technique for multilevel cervical myelopathy by comprehensively considering the fusion rate,recovery of neurological function,duration of operation,perioperative bleeding and length of stay.

Objective To assess the clinical effect and methods of posterior decompress and fixation for upper-middle thoracic fracture and dislocation. Methods Between September 2002 and September 2007,21 patients suffered from upper-middle thoracic fracture and dislocation were treated with posterior approach, which comprising 5 patients with compressed fracture,4 patients with burst fracture, 12 patients with fracture and dislocation. There were 12 cases companied by complete paraplegia, and 9 cases companied by incomplete paraplegia. All cases adapted to pedicle screw fixation system after decompression and reduction. Reduction or removal of fragments was done through posterior-lateral of the spinal canal for patients with fragments migrated into the spinal canal. The operation time,blood loss volume,preand postoperative transverse displacement degree and angle of the injured vertebra were recorded. The neurological function was assessed by Frankel criteria. Results The patients was followed up for (2.5 ± 0.5 ) years. The Frankel score increased from ( 1.0 ± 0.1 ) scores preoperatively to ( 1.3 ± 0.1 ) scores postoperatively. The incomplete paraplegia patients' score increased from (2.2 ± 0.2) scores preoperatively to (3.1± 0.2) scores postoperatively. The height of injured vertebral body, the interangle of vertebral body and spondylolistheses after operation increased comparing with those before operation(P ＜ 0.05 ). No implant loosening or breakage was found. Conclusions Severe spinal cord injury occurs in upper-middle thoracic fracture and dislocation.Unstable fracture should be treated with internal fixation and fusion in time. Decompression ought to be done in patients who suffering from incomplete paraplegia. Early operation takes advantages of immediate stability and a good improvement of the neurologic function.

BACKGROUND: Primate is the best animal to establish a model of spinal implants. However, ethics and cost limit its application. Mixed-breed dogs have similar anatomic structures as human. Moreover, it is easy to obtain with low cost, so it may replace primate to serve as models.OBJECTIVE: To determine the feasibility of canine lumbar spine to establish the anterior interfixation model following measurements of related anatomic data.METHODS: A total of 9 adult healthy dogs were selected. The transversal diameter, sagittal diameter and height of vertebral body and disc were measured, and the artificial vertebral body replacement was performed. Bone graft fusion was observed. RESULTS AND CONCLUSION: The transversal diameter, sagittal diameter and height of vertebral body and disc increasedgradually from L_(1) to L_(7), and the height was greatly exceeded its sagittal diameter. All dogs survived, but one was paraplegia. Allthe others stood and acted in 12 h to 72 h after operation. The fusion effect was proved to be good by imageology and histology. The establishment of models was simple and cost-effective, and the biocompatibility of bone tissues and implants, as well as thebone tissue ingrowth can be observed. The lumbar spine of dog can be used as an anterior interfixation model in vitro test.

Objective To compare the incidence of secondary surgical procedures after cervical disc arthroplasty vs anterior cervical discectomy with fusion in patients treated for symptomatic single level cervical spondylosis.Methods An online search of Pubmed, Medline, Ovid, Embase, Cochrane Library, CBM database, Wanfang data and VIP database were searched for prospective randomized controlled trial of cervical disc arthroplasty versus anterior cervical discectomy with fusion in incidence of secondary surgical procedures.Data were collected and extracted by two reviewers independently.Risk of bias was assessed using the criteria of Cochrane Reviews Handbook 5.1.0.Review Manager 5.2 software system was used to evaluate the data for Meta analysis.Results A total of 12 trials were included.Six of them were short-term follow up (two years).The 6 other trials were mid-and long-term follow up (mean 5.8 years).There are 4 trials with low risk of bias, 7 trials with moderate risk of bias, and 1 trial with high risk of bias.The results of meta-analysis showed there was no statistical difference in reoperation rate of adjacent level between the two groups at two years follow-up;however, the reoperation rate of non-fusion group was significantly lower in the non-fusion group compared with fusion group at mid-and long-term follow-up.The incidence of secondary surgical procedures at index level was higher in fusion group than in non-fusion group.No statistical difference was found between the two groups in using ‘ removal’ for secondary surgical procedure at two years follow-up;however, the rate of non-fusion group was significantly lower than fusion group at mid-and long-term follow-up.Conclusion Cervical disc arthroplasty was partly superior to anterior cervical discectomy with fusion in avoiding secondary surgical procedures of adjacent levels.However, non-fusion surgery doesn't have any advantages in short time (two years) follow up.Reducing the incidence of pseudarthrosis was an effective way to decrease the incidence of secondary surgery procedures in index level.