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Objective: To validate the hypothesis that there exists an optimal axial compression stress range to enhance tibial fracture healing., Methods: Rabbits with a surgically induced V-shaped tibial fracture were separated into 2 main groups: the control group (C Group, n equal to 6) without application of any axial compression stress stimulation postoperatively and the stimulation group (S Group, n equal to 90). The S Group was further divided into 20 subgroups (S11 to S54) in terms of 5 axial compression stress stimulation levels (112.8 kPa, 289.8 kPa, 396.5 kPa, 472.7 kPa, and 602.3 kPa) and 4 experimental endpoints (1, 3, 5 and 8 weeks after operation). A custom made circular external fixator was used to provide the axial compression stress of the fracture sites. Based on X-ray observation, a fracture healing scoring system was created to evaluate the fracture healing process., Results: At 8 weeks after operation, there existed a "arch shape" relationship between healing score and axial compression stress stimulation level of fracture site. The optimal axial compression stress stimulation ranged from 289.8 kPa to 472.7 kPa, accompanying the best fracture healing, i.e. the fracture line became indistinct or almost disappeared, and a lot of callus jointed the two fracture ends. Meanwhile, at 5 weeks after operation, corresponding to the relatively low healing scores, there was a fracture healing performance similar to that at 8 weeks. Besides, at 1 or 3 weeks after operation, for all the axial compression stress levels (0-602.3 kPa), no obvious healing effect was found., Conclusions: It is implied from the stated X-ray observation results in this study that the potential optimal axial compression stress stimulation and optimal fracture healing time are available. The axial compression stress level of 289.8-472.7 kPa and fracture healing time of more than 8 weeks jointly comprise the optimal axial compression stress stimulation conditions to enhance tibial fracture healing.

Objective: To prospectively evaluate the feasibility, safety and efficacy of the percutaneous pedicle screw fixation through the pedicle of fractured vertebra in the treatment of type A thoracolumbar fractures using Sextant system in the retrospective non-randomized case-control study., Methods: A total of 38 consecutive non-randomized patients with type A thoracolumbar fractures, which had been stabilized posteriorly from December 2006 to March 2009, were examined retrospectively more than 9 months after surgery. Twenty-one patients had been treated conventionally with open pedicle screw fixation (OPSF) and 17 patients received minimally invasive treatment with Sextant percutaneous pedicle screw fixation (SPPSF). As a method of evaluation, the incision size, the intraoperation and postoperative volume of blood loss, operation time, postoperative hospital stay, blood transfusion, the radiological assessment of the sagittal Cobb;s angle, vertebral body angle and vertebral body height were recorded and compared., Results: All patients were followed up for 8-24 months (average 11.6 months). There were significant differences in the incision size, surgical blood loss, surgical draining loss, operation time, hospital stay after operation, blood transfusion, the proportion of antalgic supplement and postoperative incisional VAS between the two groups (P less than 0.05). Mean preoperative kyphotic deformity was 16.0 degree and improved by 9.3 degree after surgery in OPSF group, but 15.2 degree and 10.3 degree respectively in SPPSF group. Mean preoperative angle of the fractured vertebral body was 15.9 degree and improved by 7.9 degree after surgery in OPSF group, but 14.9 degree and 6.6 degree respectively in SPPSF group. Mean anterior vertebral body height (% of normal) was 67.3% before surgery and 95.8% after surgery, but 69.1% and 90.1% respectively in SPPSF group. Mean posterior vertebral body height (% of normal) was 93.3% before surgery and 99.5% after surgery, but 88.9% and 93.3% respectively in SPPSF group. Among the patients whose 9-month follow-up films were available, 3.0 degree of kyphosis correction was lost in OPSF group, but 3.2 degree in SPPSF group. And 1.0 degree of the angle of the fractured vertebral body correction was lost in OPSF group, but 1.5 degree in SPPSF group. Then 3.0% of the anterior vertebral body height correction was lost in OPSF group, but 2.2% in SPPSF group. And 3.0% of the posterior vertebral body height correction was lost in OPSF group, but 2.5% in SPPSF group. The sagittal Cobb's angle, vertebral body angle and anterior height of the fractured vertebra were all significantly different in each group before and after operation (P less than 0.05). There were no significant differences in the postoperative sagittal Cobb's angle, vertebral body angle and the improvement of the vertebral body height and the kyphotic deformity correction between OPSF and SPPSF groups (P larger than 0.05), but there was significant difference in the postoperative anterior height of the fractured vertebra between the two groups (P less than 0.05)., Conclusion: The percutaneous pedicle screw fixation through the pedicle of fractured vertebra using Sextant system is a good minimally-invasive surgical therapeutic choice for patients with type A thoracolumbar fracture except for that the SPPSF has a little insufficiency in resuming the anterior height of the fractured vertebra compared with OPSF.

Objective: To investigate the surgical procedures, options and surgical indications for far-lateral lumbar disc herniation between three different minimally invasive procedures., Methods: From January 2000 to October 2006, 52 patients with far-lateral lumbar disc herniation (29 males and 23 females, with the average age of 41.5 years) were treated with minimally invasive procedures. All the patients were assessed by X-ray and CT. Some were given additional myeography, discography, Computerized tomography mye-lography (CTM) and MRI examination. Yeung Endoscopy Spine System (YESS), METRx and X-tube procedures were performed in 25, 13 and 14 cases, respectively. All patients were followed up for a mean period of 13.5 months. Clinical outcomes were assessed by visual analog score (VAS) and Nakai criteria., Results: The results indicated that the three procedures could significantly improve the radiating leg symptoms (P less than 0.05). The postoperative overall excellent and good rates of YESS, METRx and X-tube procedures were 84.0%, 84.6% and 92.8% respectively, with no statistical difference among three groups (P larger than 0.05). The YESS procedure had several advantages including shortest operation time, simplest anesthesia and least trauma as compared with the other two procedures, especially for simple type I far-lateral lumbar disc herniation. METRx procedure was specially suitable for simple type II. And the procedure of posterior endoscopic facetectomy, posterior lumbar interbody fusion and unilateral pedicle screw instrumentation with X-tube was designed for far-lateral disc herniation combined with degenerative lumbar instability., Conclusion: Minimally invasive strategies and options should be determined by different types of far-lateral lumbar disc herniation.

Objective: To evaluate the surgical procedure of endoscopic transforminal discectomy, bone grafting and Dynalok pedicle screw fixation under X-Tube operation system in the treatment of lumbar disc herniation combined with segmental instability and/or pars defected spondylolithesis., Methods: From June 2004 to May 2006, 42 patients with classic features of lumbar disc herniation combined with segmental instability and/or pars defected spondylolithesis underwent endoscopic transforminal lumbar interbody fusion (TLIF). Under the guidance of fluoroscopy, a 2.8 to 3.0 cm incision with 4.5 to 5.0 cm apart from the posterior middle line was made on the symptomatic side and the working portal (X-Tube) was docked unilaterally on the facet joint. A total facetectomy was then performed to expose neural foramina and nerve root. Discectomy and endplate preparation were completed through the tube. A Telamon cage was placed obliquely into the intervertebral space after interbody grafting, and then the Dynalok pedicle screw fixation system was performed. This procedure was accomplished on the lateral side when it is necessary., Results: Clinical outcomes were determined using the Oswestry Disability Index (ODI) which revealed that 62.2% of patients got excellent results, 29.2% good and 8.6% fair. The average hospital stay was 12.5 days (5-25 days). Operation time averaged 240 min (110-320 min), blood loss averaged 140 ml (80-420 ml) and incision length averaged 3 cm (2.8-3.2 cm). Five patients had complications including wound infection in 1 case, incision dehiscence and focal skin necrosis in 1, progressive radicular pain of contralateral leg in 1 and residual radicular numbness after transient radicular pain in 2., Conclusions: This surgical procedure of endoscopic transforminal diskectomy, bone grafting, cage placement and pedicle screw fixation can be effectively accomplished under X-Tube operation system with predominant benefits such as small incision, less stripping of paraspinal muscles, minimal blood loss and rapid postoperative recovery.

Objective: To study the expression regularity of vascular endothelial growth factor (VEGF) during the process of fracture healing, and the type of VEGF receptor expressed in the vascular endothelial cells of the fracture site., Methods: The fracture model was made in the middle part of left radius in 35 rabbits. The specimens from the fracture site were harvested at 8, 24, 72 hours and 1, 3, 5, 8 weeks, and then fixed, decalcified, and sectioned frozenly to detect the expression of VEGF and its receptor at the fracture site by in situ hybridization and immunochemical assays., Results: VEGF mRNA and VEGF expression was detected in many kinds of cells at the fracture site during 8 hours to 8 weeks after fracture. Flt1 receptor of VEGF was found in the vascular endothelial cells at the fracture site during 8 hours to 8 weeks after fracture, and strong expression of flk1 receptor was detected from 3 days to 3 weeks after fracture., Conclusions: The expression of VEGF and flt1 receptor appears during the whole course of fracture healing, especially from 1 to 3 weeks. Flk1 receptor is highly expressed in a definite period after fracture. VEGF is proved to be involved in the vascular reconstruction and fracture healing.

Objective: To study the effect of vascular endothelial growth factor (VEGF)and anti-VEGF on the expression of fracture healing-related factors and observe pathological changes at fractured sites., Methods: Fracture models were established in 105 New Zealand white rabbits and they were randomly divided into control group, VEGF group and anti-VEGF group. The relevant factors expression at fractured sites was assayed and pathological changes were observed in decalcified samples at 8, 24, 72 hours and 1,3,5,8 weeks after fracture., Results: After application of VEGF, the expression of BMP appeared earlier and expression time lasted longer. On the contrary, anti-VEGF completely inhibited the expression of BMP. The fractured sites were filled with fibrous callus, cartilaginous callus and bony callus at the 3rd week and woven bone was constructed at the 5th week. Fracture healing was accomplished at the 8th week in VEGF group. In anti-VEGF polyclonal antibody group, cellular necrosis increased at early period. Continuous focal necrosis was seen in the fractured sites from the 1st week to 5th week. Vascularization reduced obviously at the 3rd week., Conclusions: Fracture healing is a result of mutual regulation and coordination among many factors. VEGF may be an important factor in fracture healing.

Objective: To clone and identify one novel regeneration related gene H(3) (CA854305) from the differential expression genes library we had set up before., Methods: Use the method of Northern blot to detect the different expressions of the novel gene under different situations, employ the technique of in silico cloning to scan the span of the novel gene, and analyze their sequences. Also we used reverse transcription PCR to validate the largest open reading frame., Results: Northern blotting results of H(3) (CA854305) showed that the transplanted group had more efficient and extensive expression than untreated and uninjured groups 5 days after spinal cord injury, while the untreated group had more extensive expression than uninjured group. It implied that H(3) might have some relationship with nerve regeneration after spinal cord injury. From the results of in silico cloning we got a longest contig of 1635 bp and an largest open reading frame of 542 bp from 49 to 591 bp correspondent with the Cozak rules. Reverse transcription PCR validated the largest open reading frame sequence primarily., Conclusions: We got the sequence of novel gene H(3) which might be one of the regenerationjrelated genes. Key words:Gene library; Genes; Nerve regeneration; Spinal cord injuries.