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.

Objective To investigate the causes and clinical significance of cement leakage into disc space during kyphoplasty. Methods Since 2002, 178 patients with osteoporotic vertebral compression fractures underwent kypboplasty and 15 of them were detected intradiscal cement leakage and followed up more than 2 years (mean 2 years and 8 months). The mean injection of cement in these patients was 4.2ml.The series comprised 10 females and 5 males, with an average of 71.2 years old ( range, 54～84 years old).Visual analog scale was used to score back pain pre- and postoperatively. The height and MRI index of the involved disc were recorded and compared. Results The discs involved were as following: T10-11 for 4 cases,T11-12 for 1, T12L1for 4, L1-2 for 2, L2-3 for 3, L3-4 for 1. Cement leakage was detected in the disc above the fractured vertebrae in 10 cases, and in the disc below the fractured vertebrae in 5 patients. The back pain significantly alleviated and the average visual analog scale (VAS) score was decreased from 8.5±2.1 preoper-atively to 3.3±1.4 postoperatively (P< 0.05). The anterior disc height was (5.1±2.1)mm preoperatively and (4.8±1.9) mm at the final follow-up, the middle disc height was (7.4±3.2) mm preoperatively and (7.3±2.9) mm at the final follow-up, the posterior disc height was (4.9±2.5) mm preoperatively and (5.0±1.8) mm at fi-nal follow-up, the heights of intervertebral space were well maintained. The signal intensity decreased and became inconsistent in some discs, and the preoperative MRI index significantly decreased from 25482.4± 3467.5 to 18927.6±2519.4 at the final follow-up (t=1.967,P< 0.05). Conclusion Pain relief is impressive in patients with intradiseal cement leakage during kyphoplasty. However, cement leakage into disc space may accellerate the process of disc degeneration.

Objective To evaluate the efficacy and safety of balloon kyphoplasty in the treatment of painful multi-vertebral osteoporotic compression fractures. Methods From October 2002 to April 2007, 42 patients (96 vertebrae) with painful multi-vertebral osteoporotic compression fractures underwent kyphoplasty. The group included 14 men and 28 women with an average age of 72.5 years (range 56-91 years). Each pro-cedure included insertion and insertion of balloon, fracture reduction and cement filling under "C"-arm monitoring. Preoperative and postoperative pain level, SF-36 score, vertebral height restoration, local kypho-sis correction and complications were recorded and analysed. Results All 42 patients tolerated the opera-tion well and were followed up for average 31.4 months (range 12-71 months). The mean VAS pain score decreased significantly from 7.1±2.4 preoperatively to 2.7±1.3 postoperatively, the mean height of anterior and medial vertebral body were (1.8±0.5) cm, (1.6±0.6) cm preoperatively and (2.3±0.6) cm, (2.2±0.7) cm postoperatively. No significant change of posterior vertebral height was recorded postoperatively.The mean correction of local kyphosis was 9.2°at each level. 6 of 8 subscahs measured by SF-36, including physical function, role function, bodily pain, vitality, role emotion, mental health, were significantly improved by the operation. Complications were found in 7 patients including 6 cases of cement leakage with no clinical symptoms (intradiscal cement leakage in two cases, paravertebral vessel leakage in two cases, paravertebral leakage in one case and cement leakage into canal in one case), and 1 case of pulmonary embelization with symptoms relieved after conservative treatment. Conclusion Kyphoplasty is effective and relatively safe for multi-vertebral osteoporotic compression fractures.

Objective To evaluate the long term outcome of spondylolytic spondylolisthesis treated with Steffee system and posterolateral fusion. Methods Thirty- four patients were followed up for an average of 77.2 months. The follow- up study include slipping percentage, slipping angle, heights of intervertebral space and foramen, fusion rate, screw broken rate and clinical outcomes. Results 1) Solid fusion was obtained in 88.2％ of patients. screw broken rate was 2.9％ . 2) Comparison of pre- and post- operative slip showed correction rate of 45.1％ . The heights of intervertebral space and foramen increased, slipping angle decreased. 3) During the period of follow- up, recurrence of deformity was found. 4) The subjective outcome was better than the objective outcome. Conclusion 1) Lumbar spondylolytic spondylolisthesis with radicular symptom need complete decompression and reduction as much as possible. 2) A positive slipping angle indicates significant shearing force and the need of an interbody fusion to restore the weight- bearing capacity. 3) Objective criteria is more suitable to evaluate surgical outcome.

Objective To evaluate the methods and results of revision surgery for posterior lumbar cage interbody fusion (cage-PLIF) with postoperative complications, and to analyse the surgical techniques for prevention of these complications. Methods From October 1996 to December 2002, 21 patients with postoperative complications of cage-PLIF underwent reoperations. There were 11 males and 10 females with an average of 43.4 years. The interval between primary and revision surgery ranged from 6 days to 1.5 years with an average of 0.6 year. 16 patients suffering from lumbar disc herniation were treated with the discecto-my and single uninstrumented cage fusion, 5 patients of lumbar spondylolisthesis were treated with cage-PLIF and pedicle screw instrumentation. The complications included cage displacement backward in 20 patients, forward in 1,and cage subsidence in 9 as well. 15 patients complained of low back pain wors-ening or leg radicular pain, of which 4 had intermittent claudication and 10 had leg numbness or weakness during rehabilitation. Revision surgery included re-implantation of the cage filled with iliac crest bone chips in 11 patients, iliac bone autograft after removal of original cages in 7 and decompression of involved nerve root witbout removal of migrated cage because of technical difficulty. Pedicle screw fixations were used in 12 and the intertransverse fusion both with autograft and allograft was added in 7. Results The mean follow-up was 14.2 months (ranged, 7 to 36 months). The cages presented slight retro-displacement in 4 patients shortly after reoperation, without involvement into spinal canal during the subsequent follow-up. Bony fusion occurred in 13 patients, and the pseudarthrosis in 3 patients without further migration of cages. The clinical symptoms relieved in 5 patients, improved in 9, no any change in 6, and worsened in 1. However, low back pain remained in 8 patients, and dysuria in 1 patiant at the last follow-up. Conclusion The results of revi-sion surgery are not satisfactory according to this study, the surgical treatments should be performed as soon as possible if conservative treatments is ineffective. The correct surgical indication and proper technical are the key of prevention of the postoperative complications.

Objective To evaluate the clinical results of self-designed anterior cervical low-profile plate system (ACLPS). Methods The anterior cervical plate system, composed of one plate, two locking caps and two types of screws. The system was made of medical titanium alloy possessing the following characteristics: low profile, instant locking, versatile use and unicortical screw fixation. 37 patients with cervical disorders were fixed with ACLPS after anterior spinal decompression and interbody fusion. The diagnosis included spondylosis in 8 cases, cervical intervertebral disk protrusion in 12, fracture and /or dislocation with paralysis in 14 and metastatic tumor in 3. The fusion were performed with autologous iliac crest bone graft for 29 patients while the others with cages. The fixed levels ranged from C3 to T1. Results 37 cases were followed-up for an average of 9.6 months, ranging from 6 to 12 months. Postoperatively all patients felt comfortable in neck without any foreign body sensation. No obvious complications such as wound infection, hematoma, asphyxia, nerve injury, laceration of spinal cord dura, leakage of cerebrospinal fluid, bleeding and nonhealing of the wound were observed. Solid interbody fusion were achieved in all cases. According to JOA scores, the total effective rate was 94.6% while the good rate was 83.8%. The radiograph confirmed that there was no dislocation or subsidence of graft, no obvious loss of intervertebral height, no loosening or failure of implant. Conclusion In regard to the high rigidity, good bony purchasing and easy handling, ACLPS is able to provide sufficient biomechanical stability and is an optional choice for clinical use.

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 describe the surgical technique for treatment of old traumatic posterior acetabular defects. Methods From March 1990 to March 1998, 6 patients were treated with a full thickness iliac crest autograft to reconstruct their posterior acetabular defects. There were 4 males and 2 females, the average age of the patients was 32 years. The acetabular defects were caused by traffic accident and delayed in treatment for 3 to 11 months. Results The duration of follow up was 2－ 10 years， the function of the hip joints were good in all of the patients, according to the criterion of d Aubigne six points. X－ ray film revealed that although the femoral head was not in exact congruence with reconstructed acetabulum, yet there was no dislocation. Slight degeneration was found in 3 cases. Conclusion Although this procedure did not exactly reproduce the anatomy of the hip joint, it restored the posterior stability, provided bone stock for the hip joints and prevented dislocation of the femoral head. So this procedure is useful for late total hip arthroplasty.

Objective To review the clinical results of cemented and uncemented revision total hip arthroplasty(RTHA). Methods The diagnoses included aseptic loosening of the femoral components in 23 cases, fractures around the tip of loosened femoral components in 3 cases. Of 26 cases, 10 cases(10 hips)underwent RTHA by the use of the second generation cementing techniques, 16 cases(16 hips)underwent uncemented RTHA with a long stem porous coated femoral component assisted with autografting. Results At an average of 6 years of follow- up for cemented RTHA, clinical results were evaluated as excellent or good in 5 hips(50％ ),fair in 3 hips(30％ ) and poor in 2 hips(20％ ), re- revision in 1 hip(10％ ). X－ ray film revealed definite loosening in 2 hips, probable loosening 1 hip, possible loosening 5 hips, and no loosening 2 hips. At an average of 5 years follow- up for uncemented RTHA,clinical results were evaluated as excellent in 9 cases(56％ ),good in 6 cases(38％ ), fair in 1 case (6％ ),no case need rerevision. X－ ray film revealed osseous fixation of the femoral components in 12 cases (75％ ), fibrous stability in 4 cases (25％ ). The apparent reconstitution of femoral bone structure present in the area of previous osteolysis or cortical thinning. Conclusion Clinical results of the uncemented RTHA are significantly superior to that of cemented RTHA. Reconstructing any structural bone loss with cancellous autograft and getting adequate mechanical fixation with a long stem porous- coated prosthesis may contribute to the good results of uncemented RTHA.