BACKGROUND:A new type of medical titanium alloy Ti2448 (Ti-24Nb-4Zr-7.9Sn) is by far the lowest initial modulus of titanium alloy, with the initial modulus of about 40 GPa, the average Young's modulus<20 GPa, and tensile strength of about 900 MPa;human tissue biocompatibility and mechanical compatibility are excellent. OBJECTIVE:To investigate the biomechanical properties of a new low elastic modulus spinal pedicle screw fixation system and compare it with Ti6Al4V pedicle screw. METHODS:Totally 60 fresh human cadaveric thoracic vertebrae were randomly selected:on one side, pedicle new low modulus Ti2448 pedicle screws, as the experimental group;on the other side, pedicle screw Ti6Al4V, as control group. The maximum bending load and maximum load displacement, maximum torque and maximum axial pul ing force of the two groups were detected. RESULTS AND CONCLUSION:There was no significant difference in the maximum bending load, maximum load displacement, maximum torque and maximum pulling force between the two groups. The results show that the maximum bending strength, the maximum torque and maximum pul out force in low elastic modulus of Ti2448 pedicle screw fixation system are consistent with the Ti6Al4V screws, which can meet the needs of internal fixation on spinal biomechanics strength.

Objective To evaluate the efficacy and surgical technique of percutaneous transforaminal endoscopic lumbar intervertebral disc discectomy (TES) for senile lumbar intervertebral disc protrusion.Methods Twenty-three patients with senile lumbar intervertebral disc protrusion were admitted to percutaneous TES from April 2009 to April 2010. Surgical segments included L4-5 in 11 cases, L5-S1 in 9cases,L3-4 in 3 cases. There were 10 contained and 13 non-contained,6 disc herniation in or out of the foramen and 1 recurred. Nine simple cases were treated by TES and 14 cases with narrow foramens treated by intervertebral foraminal plasty at the same time. Visual analogue scale (VAS),Oswestry disability index (ODI) and the modified MacNab criteria were employed to evaluate the clinical outcome. Results There was no dural matter tear and intraoperative neurovascular injury. Two patients suffered transient hyperalgia in lower limbs which were healed after 1 week by conservative treatments. All patients were followed up with mean period of 6-12(9.53 ± 3.02) months. The VAS of sciatica decreased from(8.3 ± 1.2) scores preoperatively to (3.7 ±2.1) scores at three days postoperatively and ( 1.5 ± 1.2) scores at the last follow-up visit (P＜0.01). The ODI decreased from 53.3 ± 24.0 preoperatively to 26.2 ± 15.0 at three days postoperatively and 20.4 ± 6.0 at the last follow-up visit(P＜ 0.01). There were 18 excellent,3 good and 2 fair outcomes according to modified MacNab criteria with the excellent to good rate of 91.3% (21/23). Conclusion TES is applicable for senile lumbar intervertebral disc protrusion, which has the advantages of minimal invasion, less haemorrhage,early function recovery and it is a safe and effective method.

Objective To explore clinical the characteristics and countermeasures of osteoporotic vertebral fractures treated with percutaneous vertebroplasty. Methods From March 2005 to March 2008,64 patients (totally 86 vertebra) with osteoporotic vertebral fractures undergoing percutaneous vertebroplasty were retrospectively analyzed. The level of fracture was between T5 to L5. The symptomatic fractured vertebrae were determined with combination of regional pain, X-rays and MR images. The postoperative effect were evaluated by the visual analog score (VAS) and Oswestry disability index (ODI). Results All the patients were followed up 12 - 23 ( 13.40 ± 1.03 ) months. The VAS decreased from (8.3 ± 1.2) scores to bdfore surgery (2.3 ± 1.4) scores after surgery and to (2.5 ± 1.1 ) scores at the last follow-up time(P ＜ 0.01 ). The ODI decreased from (62.0 ± 2.3 ) scores before surgery to (23.1 ± 2.5 ) scores after surgery and to ( 26.3 ±2.4) scores at the last follow-up time (P ＜0.01). The back pain of all patients were relieved to different degrees postoperatively. No severe complications including pulmonary embolism occurred. Conclusions The key point is to find the symptomatic fractured vertebrae not only based on preoperative X-rays but also the MR images, especially fat-compressing MR images. Only when the fractured vertebrae demonstrate low intensity on T1WI MR image and high intensity on T2WI or fat-compressing MR image can be considered new fractures. The injection should reach the new fractured part and if necessary the bilateral approaches should be considered and the injection can be separated for several steps in multi-segments fracture. PMMA should be injected after the bone cements are solid enough so as not to develop complications such as pulmonary embolism.