BACKGROUND: The most commonly used rod-screw posterior spinal fixation system has some biomechanical drawbacks. The screw-plate system is more preferred for patients.OBJECTIVE: To prepare a new posterior spinal fixation system based on imaging results of distance between two pedicles,radian of spine flexion, extension and the height of intervertebral space of Chinese population.METHODS: The thoracolumbar data of 129 normal people were measured. According to the imaging measurements and relative documents, a device of gear-distraction plate (GDP) for spine reduction and fixation was designed. Eighteen fresh calf lumbar specimens were randomly divided into 3 groups, the test group was fixed by GDP and the other groups were fixed by CD and Steffee plate, respectively. The results of the displacement, strain, strength, stiffness and ultimate strength were measured under the states of vertical compression, flexion, extension and lateral bending respectively, and the results were statistically analyzed.RESULTS AND CONCLUSION: GDP could meet the need of strength and stiffness of human bodies. It showed superior to the CD and Steffee plate groups in strength and stiffness (P ＜ 0.05), with 13% or 14% torsion intensity greater than that of the CD or Steffee plate groups. The ultimate mechanical performance test showed that, the load bearing of the GDP group was greater than that of the CD and Steffee plate groups (P ＜ 0.05). The findings demonstrated that GDP for Chinese human presented with good biomechanical stability, which can promote vertebrae fracture union and prevent kyphosis relapses or vertebral height loses.

To explore the relationship of mieroglia activation,motoneuronal loss in the ventral horn of spinal cord and sciatic nerve regen-eration after the sciatic nerve injury,Sprague-Dawley rats were prepared a modal of the fight sciatic nerve crash injury.The immunoreactiv-ity(-ir)ofmicroglia and number of the motoneurons inthe ventral horn of spinal cord were detected at 3 and7 days,light and electron mi-croscopic detection of sciatic nerve degeneration and regeneration were performed at 4 weeks after the nerve injury.The results showed:(1)At 3 days after the sciatic nerve injury,OX-42-irinthe ventral horn of spinal cord begantoincrease significantly(P<0.05);(2)The number ratio of motoneurons in ventral horn of spinal cord in ipsilateral to contralateral for injury decreased markedly(P<0.05),in-dicating the numbers of ipsilateral motoneuroanl survival decreased;(3)Histological assessment showed the poor regeneration of the in-jured nerves;(4)Simvastatin(an inhibitor of cholesterol biosynthesis,having potential immunomodulatory capacities)facilitated the mi-eroglial activation.the motoneuronal survival and sciatic nerve regeneration were better than non-simvastatin-treated vehicle rats.The pres-ent results suggest that mieroglia activation in the ventral horns ofthe spinal cord may play an important protective role in the nerve regener-ation after peripheral nerve injury of the rat.