BACKGROUND: It has been demonstrated that pedicle screw internal fixation influencing factors involve screw structural morphology, thread parameter, bone density, moment size for tightening screw during operation, and depth of screw placement. There is little known about the correlation of pullout strength of spinal pedicle screw with device for transverse traction to extraversion angle. OBJECTIVE: To assess effect of the spinal pedicle screw with device for transverse traction on pullout strength at different extraversion angles. DESIGN: Repeated measurement. SETTING: Center for Bone Joint, the First Affiliated Hospital of Nanjing Medical University. PARTICIPANTS: This study was performed at Laboratory for Material Mechanics, Hehai University between June and November 2003. A total of 18 adult dried lumbar vertebrae (L1-5) were provided by Department of Anatomy, Nanjing Medical University, and recruited for this study. The protocol was approved by the hospital's Ethics Committee. The pedicle screw was made of stainless steel. Each pedicle screw had a diameter of 5.5 nun, total length of 150 nun (thread part 50 into included), and the same thread parameter. Electrical universal material machine (EW type) was provided by Laboratory for Material Mechanics of Hehai University. METHODS: Bone density was measured with a single photon bone density determinator. According to the bone density, the lumbar vertebrae were numbered and randomly divided into 3 groups with 6 lumbar vertebrae in each: extraversion angle 5 ° group, extraversion angle 15° group, and extraversion angle 30° group. ① Installation of pedicle screw and clamping apparatus: According to Wein-Stein method, one entry-point was selected at each side of lumbar vertebra, and at the sametime, extraversion angle 5°, 15° ,and 30° were respectively defined for extraversion angle 5° , 15° ,and 30° groups. A 50 mm-depth pinhole was drilled with a drill bit with a diameter of 3.0 nun. Pedicle screw was screwed into 50 nun, and its end part was connected to the device for transverse traction. Spinal vertebrae and the device for transverse traction were fixed with a specially made clamping apparatus. ② Determination of pullout strength and observation of pedicle and vertebral injury: Spinal vertebrae, on which pedicle screw and device for transverse traction were installed, was placed on a EW electrical universal material machine together with clamping apparatus for determining the pullout strength of pedicle screw. Sensor was connected to a computer to draw strength-displacement curve. The wave crest of the curve was considered the maximum pullout strength. At the same time, injuries to pedicle and vertebra caused by pullout of pedicle screw were observed. MAIN OUTCOME MEASURES: Pullout strength and injuries to pedicle and vertebra. RESULTS:①The mean maximum pullout strength of pedicle screw was respectively 0.878 167, 1.420 333, and 2.154 167 KN for extraversion angle 5° , 15 ° , and 30° groups. There was significant difference among the 3 groups (F = 12.554 22, P < 0.01). ② In the extraversion angle 5° group, 4 patients presented with cortical bone fracture which occurred at the entrance for pedicle screw, and 2 patients presented with fragmentation of junctional zone between pedicle and vertebral posterior edge; In the extraversion angle 15° group, 1 patient presented with cortical bone fracture which occurred at the entrance for pedicle screw, 4 patients presented with fragmentation of junctional zone between pedicle and vertebral posterior edge, and 1 patient presented with vertebral posterior coronal fragmentation; In the extraversion angle 30° group, 1 patient presented with cortical bone fracture which occurred at the entrance for pedicle screw, 2 patients presented with fragmentation of junctional zone between pedicle and vertebral posterior edge, and 3 patients presented with vertebral posterior coronal fragmentation. There was statistical significance in the intergroup rank-sum test (P < 0.01).CONCLUSION: During application of pedicle screw with device for transverse traction, proper accrescence of extraversion angle can increase pullout strength of the screw and enhance fixative strength, and excessive extraversion angle easily injures vertebra.

Objective To compare the clinical outcomes of dilator-kyphoplasty (DKP) and balloonkyphoplasty (BKP) in treatment of osteoporotic vertebral compression fractures. Methods From May 2007 to March 2009, 23 cases with 26 vertebrae were treated with DKP, while 29 cases with 29 vertebrae were treated with BKP procedures. The operating time, bleeding volume and injecting volume of cement were recorded during operation. The distribution of cement, the restoration of vertebral height and Cobb angle were observed. The patients' visual analogue scales (VAS) score and Oswestry disability index (ODI) score were evaluated after operation. Results There were no differences in operative time, bleeding volume of every vertebrae and cement injected volume between these two groups (P＞0.05). The vertebral height, Cobb angle, VAS and ODI scores were significantly improved than those of pre-operation in these two groups (P＜0.05). The height of the anterior vertebrae and Cobb angle in DKP groups were restored significantly than those in BKP groups (P＜ 0.05). There were 1 case (1 vertebra, 3.8%) underwent cement leakage in DKP groups and 5 cases (5 vertebrae, 17.2%) in BKP groups. Conclusion DKP and BKP were effective in the treatment of osteoporotic vertebral compression fractures. The height of the anterior vertebrae and Cobb angle in DKP groups were restored significantly than those in BKP groups.

OBJECTIVETo evaluate the safety and value of preoperative transarterial embolization of hypervascular vertebral tumors.

METHODSSixteen patients with hypervascular vertebral tumors underwent transarterial embolization before surgery. The lesions were located between the middle cervical and lower lumbar spine. Forty-one arteries were embolized with permanent particles injected through a microcatheter, including polyvinyl alcohol (PVA) particles (150 - 500 micro m) in 25 arteries and Dextran particles (150 - 350 micro m) in 16. Of these, 31 had pieces of gelatin sponge added for proximal pedicled embolization. The criteria for judging the effectiveness of embolization were completeness of tumor removal and estimated blood loss during surgery.

RESULTSThe particles were injected into the tumor feeders through superselection in 17 arteries or flow control in 24. Tumor embolization was defined as "total" in five patients, "nearly total" in eight, "subtotal" in two, and "partial" in another. There were no symptomatic complications associated with embolization. Tumors were entirely removed in all patients. The average estimated blood loss during surgery was 1510 ml (range of 200 - 6000 ml) for all 16 patients.

CONCLUSIONPreoperative embolization of hypervascular vertebral tumors is safe and effective. It can make complete resection of a tumor possible and can make a previously unresectable tumor resectable. Superselection or flow control is necessary to achieve effective devascularization and to avoid complications.

Adolescent ; Adult ; Arteries ; Embolization, Therapeutic ; methods ; Female ; Humans ; Male ; Middle Aged ; Retrospective Studies ; Spinal Neoplasms ; surgery