Application of the techniques of pedicle screw fixation in t horacolumbar spine has forcefully promoted the development of spinal surgery. Th e key to the techniques is that the pedicle screw insertion must be located into the sole exact routeway of the three-dimensional-space, that is, into the inn er vertebral body through the pedicle according to the exact arrow plane angle a nd horizontal plane angle. Recently great development has been made in the resea rch on the techniques of pedicle screw insertion in thoracolumbar spine, especia lly in the supervising means during operation. The means have been developed fro m the traditional X-ray perspective or photograph apposition to the application of computer-assisted technique. This paper reviews and discusses the current d evelopment and prospects in the research on the techniques of pedicle screw inse rtion in thoracolumbar spine.

0.05). Conclusion The study of the characteristic of track of percutaneous transpedicular puncture is good for the safe procdure under image guidance. The standard track is safe for transpedicular or parapedicular puncture. The percutaneous transpedicular puncturing sites can be located according to the spinous process.

[Objective]To study the changes of biomechanical efficiency of absorbable balloon vertebraplasty associated with pedicle screw system for treatment of thoracolumbar fracture.[Method]Six fresh adult thoracolumbar specimens were harvested and 10 segmental specimens(T_(11)~L_1、 L_(2~4)、 L_(1~3)) were processed.After burst fracture created by free-drop test,the specimens were braced and reduced by APF pedicle screw,then absorbable balloon were placed through the traumatic vertebral pedicle and were infused with autosolidification calcium phosphate cement to process vertebroplasty.The stiffness in middle vertebrae were measured under flexion,extension,lateral flexion and torsion stress before fracture and after absorbable balloon vertebroplasty respectively.[Result]The crushing strength in traumatic vertebrae after vertebroplasty with absorbable saeculi increased showed 8% under flexion,15% under extension and 9.8% under lateral flexion,but with significant increasing under extension(P0.05).[Conclusion](1)absorbable balloon vertebraplasty associated with pedicle screw system conduces to the reconstruction of traumatic vertebrae,and making postoperative spinal biomechanical characteristics approach the level before fracture;(2)Vertebroplasty with absorbable sacculus for treatment of thoracolumbar burst fracture based on the premise that avoid the potential danger induced by leakage of bone cement,and can reestablish intact corporeal structure of traumatic vertebrae and restore their height essentially,so that spinal physiologic curve can be gained to restore and maintain,tardive lumbodorsal pain and spinal cord injury and nerve injury caused by secondary kyphosis can be prevented,this can fundamentally solve complications left over by thoracolumbar burst fracture treated using pedicle screw system simply.The new method prorides a rational method for clinical treatment of thoracolumbar burst fractures.

[Objective]To investigate feasibility and efficacy of clinical application of endoscopic anterior cervical decompression and fusion.[Method]With Metrx MED system and modified working tube and decompression instruments,endoscopic anterior cervical decompression and fusion were performed on 15 patients with cervical spondylotic myelopathy.A paramidline right transverse incision of 2 cm long was made.A channel between the neurovascular and visceral sheath was created through finger dissection.The dilators were inserted sequentially.An original one arm working tube or a modified,shortened working tube with double arms was inserted over the dilators.Then decompression and fusion with autologus graft was performed under endoscope.[Result]Once the tubular retractor was stably fixed throughout the operation,releasing of the discomfort was observed.All the compression tissue such as soft disc tissue or hard osteophyte and anterior longitudinal ligament or dura sac were clearly visualized under the endoscope.Shortened working tube provided improved visual field and increased manipulation space for the decompression instrument.The double arms enhanced stability of the working tube but could not eliminate moving of it during operation.Intraoperative blood loss was 200 ml to 800 ml.The operation lasted 80 to 210 minutes.The incision healed in one week.Postoperative discomfort in laryngeal region was light.All of the cases showed thorough decompression on postoperative MRI films and gained better spinal cord function at postoperative follow-up.No surgery-related complication were encountered.[Conclusion]Endoscopic anterior cervical decompression and fusion based on the use of a working tube is technically feasible.Compared with conventional method,this technique has the advantages of improved intraoperative visualization,thorough decompression,minimal trauma,quicker recovery and improved cosmetic result.Disadvantages waiting for further improving include:limited manipulation space,discomfort and potential hazards to the surrounding structure resulted from moving of the working tube.

Objective To conduct biomechanical study and three dimensional finite element analysis on lumbar spondylolysis and spondylolisthesis treated with single vertebra reduction and fixation system(LSRF), and to evaluate the long term outcome of isthmic spondylolisthesis treated with direct repair and fixation with LSRF. Methods Biomechanical characteristics of LSRF was tested, and three dimensional finite element model of lumbar spondylolysis and isthmic spondylolisthesis was established, the stress of lumbar in spondylolisthesis was observed after fixation and reduction. Thirty two patients with spondylolysis and isthmic spondylolisthesis were treated with direct repair and fixation with LSRF designed by the authors from 1992 to 1995. Eighteen cases had spondylolysis, and the others accompanied with spondylolisthesis. The patients age was 28-46 years, with an average of 36.4 years. Results The biomechanical study and three dimensional finite element analysis showed that LSRF has good ability in reduction and rigid fixation. All patients were followed up for an average of 5.6 years. The latest radiographs showed that bony union occurred in 29 cases. There was no breakage and pullout of screws except dislocation of hook in 2 patients. By Henderson standard, the result was excellent in 22, good in 6, fair in 2, poor in 2. Conclusion LSRF has stronger fixation strength and higher fusion rate. Direct repair and fixation with LSRF is a good procedure for younger and middle aged patients with spondylolysis and isthmic spondylolisthesis.

Objective To study the variability of the parameters of the pedicle screw path and influencing factors of clinical significance. Methods A Picker PQ6000 Spiral CT was used to scan 736 vertebrae from C 3 to L 5 of 118 men and 80 women aged between 17 and 58. The largest transverse diameter, screw path length and e angle (the angle between the axis of the pedicle and sagittal plane) of each pedicle were measured. The contour of the vertebrae and the relationship of the sagittal axis of the spinal process, vertebral body and human body were inspected. Any discrepancy of these axes was measured and recorded. The gender, age, height and weight were recorded at the same time. Results Measurement of the biggest transverse diameter, screw path length and e angle at each vertebral level showed a wide range of value and quantity. Although the screw path length and the transverse diameter of the pedicle showed significant difference between man and woman, further covariance analysis for between subject effects revealed that no inter gender difference existed after the effects of height and weight were removed. Both height and weight showed significant positive correlation with the screw path length and transverse diameter of the pedicle, but no correlation with the e angle. Observation on the deformity of the vertebrae showed that the sagittal axes of the vertebral body and human body was discrepant in 14 thoracic and lumbar vertebrae; the sagittal axes of the spinal process and vertebrae was discrepant in 11 vertebrae; the transverse diameter of the pedicle was smaller than 4 mm in 14 vertebrae below T 9; 4 vertebrae showed lateral convex pedicle. Conclusion The parameters of the pedicle screw path varied in different subjects and different vertebral level with a large variability. The weight and height are two important factors to influence the parameters. Deformity is another factor which may lead to mistake of placement of the pedicle screw. To improve the accuracy of the pedicle screw, individual identification of the entering point and orientation should be considered and in some circumstances even special screws, should be used.

Objective To summarize the surgical techniques and results of displaced complex ac-etabular fractures.Methods Ninety-eight cases of complex type o f acetabular fracture with dislocation were treated with open reduction and inte rnal fixation from March 1990to Sept ember 1999.Of the 98cases,fractures of the posterior column an d wall was seen in 9cases,T -shaped in28cases,transverse and posterior wall in 22cases,anterior and hemi-transverse in 2cases,both column in 37cases.Kocher -Langenbeck approach was adopted in 28cases,ilio-inguinal approach in 21cases,extended iliofemoral approach in 16cases,and double approachs(K -L +ilio-inguinal)in 33cases.Results Sixty-two cases(63.3%)had anatomic reduction,32cases(32.7%)satisfactory reduction,4cases(4.1%)unsatisfactory reduction.The rates of anatomic reduction in the early 4.5years and the latest 4.5years of this study were 50.0%and72.4%respectively.Seventy-eight cases were followed up from 2to 10yea rs,excellent and good rate for clinical results in anatomic and non-anatomic reduction group were 83.9%and 36.4%respectively,the difference was very significant (P

Objective To review and analyze the complications of spondylolisthesis treated wi th BAK interbody fusion cages.Methods One hundred and eighteen patients wi th spondylolisthesis were treated with BAK interbody fusion ca ges,the intraoperative and postoperative complications were reviewed,which include dural tear,nerve root injury,unsatisfactory cage position,cage retropulsion,cage subsidence and postlaminectomy adhesive arachnoiditis.Results The intraoperative complication ra te was 11%and the most commonly seen were dural tear 4c ases(3.4%),nerve root damage 3cases(2.5%)and unsatisfactory cage position 9cases(7.6%),2cases had both dural tear and unsatisfactory cage position,1patient had both nerve root injury and unsatisfactory cage position.The postoperative c omplication rate was 7.6%,which chiefly consisted of cage retropuls ion 3cases(2.5%),cage subsidence 4cases(3.4%),and postlaminec-tomy adhesive arachnoiditis 2cases(1.7%),2cases of cage retropulsion and 2ca ses of cage subsidence show partial nonunion,2cases of cage subsidence had arachnoiditis.Conclusion As a new technique,lumbar interbody fusion with BAK cages are r apidly gaining popularity,however,the complications described here suggest the importance of selection s of surgical indications and proper manipulations.[

0.05).2)a.There was no severe side effects related to cement in 20dogs,and no pulmonary embolic necrosis was found in autopsy.Cement leakage was frequent which occupied the spinal canal no mo re than 1/4of the median sagittal dia meter without major neurological complication.The epidural leaks we re related to the vertebral morpholo gy.b.The average peak temperatures were 70.5℃at the core,53.5℃at the in terface,40.8℃at the anterior corte x,and 40.5℃in the spinal canal.The temperature above 50℃lasted for 2.9minutes at the core,and 1.3minutes at the interface.In pathological examination,necrosis of osteocytes was found focally at t he periphery of the cement,and resid ual bone in this area showed signs of acti ve remodeling.3)The procedure was technically successful in all pa-tients,with an average injection am ount of 6.3ml cement per vertebral body.No clinically significant com-plications were noted.The 3slight e pidural leaks,1slight neural foram ina leak,and 5paravertebral leaks detected with CT had no clinical importance.Partial or complete pain relief was achieved in all patients as-sociated with improved mobility,an d 1patient experienced transitory worsening of pain followed by significant pain relief.Patients with vertebra l haemangioma or compression fractu res were discharged in 1-4days(average,1.6days)after the procedure.Of the 26patien ts,22were followed up from 6to 24mon ths(average,13.5months),partial or complete pain relief were sustained in 21cases,the other one experienced relapse of pain following partial pain relief,which was related to the deterioration of the metastases.Con-clusion Minimal invasive PVP is a valuable alternative in the treatment of painfu l vertebral haemangioma,osteoporotic vertebral fractures,and osteolytic metastases or myelom a,providing acute pain relief and ea rly mobilization in appropriate patien ts.[

Objective To evaluate biomeehanic characteristics of lumbar spondylolysis and spondylolisthesis single vertebrae reduction fixation system (LSRF), and discuss its mechanism of reduction. Method Twenty-four adult isthmus lumbar vertebrae specimen were disconnected and fixed with LSRF, Hefti, Salib's method respectively, and the biomechanic characteristics of the fixation devices were tested. Isthmus of L5 in 4 adult spine specimen was destroyed under loading to produce the spondylolisthesis model, and reduction by LSRF. Result The LSRF has a good ability for reduction and its strength for reduction is 1.6, 2.7 times as high compared with the Hefti, Salib's methods respectively. The mechanism of reduction is that the LSRF used contacted point of lamina by lamina hook as the fulcrum, through the pedicle screw to pull the spondylolisthetic vertebrae, and reduce the anterior displacement of vertebrae. Conclusion LSRF gives rigid fixation and good reduction, and provides a new and effective method for lumbar spondylolysis and isthmic spondylolisthesis.