.1. Nail Road Local Strengthening Plus Expansive Pedicle Screw Calf Vertebral Osteoporosis Biomechanical Model To Quickly Build To Improve The Study Of Pedicle Screw Fixation Strength

STUDY 1Since the introduction of the transpedicular screw system by Boucher in 1959 and the development of pediele serew systems from Roy-Cami1le system to RF system in the past two decades , the applications of this system in the treatment of degenerative disorders and unstable fractures, tumors of the spine have become very popular. The advantages of pedicle screw fixation are dependent on their ability to provide adequate stabilization until the fusion mass is stable. However,loosening and failure of the screws are among the most common complications reported, especially for osteoporosis.Many researchs have been carried out to slove the problem but not to be solved completely.So we discuss a new method to improve the fixation strength of pedicle screws in my current study by by using screw tunnel augmentation technique combined with expansive pedicle screws.Objective To evaluate the improvement of fixation strength by using screw tunnel augmentation technique combined with expansive pedicle screws. Method Injecting CaSO4 bone cement into the perine of pedicle screw tunnel by newly-designed instruments in order to augment the screw tunnel.Twenty lumbar vertebraes from five freshly deepfreezed human spine specimens were classified into 10 blocks by randomized block design. Four ways of fixations were used: A(common pedicle screws),B(common pedicle screws + screw tunnel augmentation technique),C(expansive pedicle screws + screw tunnel augmentation technique),D(common pedicle screws +filling CaSO4 bone cement into pedicle screws tunnel).Four ways of fixation were randomly used to the four screw tunnels of each block and then the maximum axial pullout strength(Fmax)and energy absorption were used for comparison.Results Mean of the Fmax and energy absorption of group C or D were significantly greater than those of group A(P<0.01)and group B(P<0.05). Mean of the Fmax and energy absorption of classB were also significantly greater than those of group A(P<0.01). There was no significant difference between class C and class D(P>0.05).Conclusions The fixation strength of pedicle screws might be improved by useing screw tunnel augmentation technique and it will be better if expansive pedicle screws were used at the same time.STUDY 2Though OP sheep model is a very classic animal model for biomechanical study and evaluation of pedicle screws it still has some isadvantages. Because the establishment of OP sheep model demonds at a period of at least 6 months and is easy to be influenced by mang factors and failed. So we try to establish an biomechanics model of osteoporotic vertebrae rapidly by decalcifing fresh calf lumber vertebraes with EDTA-2Na. Objective: To establish an biomechanics model of osteoporotic vertebrae rapidly by decalcifing fresh calf lumber vertebraes with EDTA-2Na.Methods:Thirty-two calf lumbar vertebraes from 4 fresh calves were classified into 8 blocks by randomized block design. Four kinds of treatments were randomly applied: group A(decalcified with EDTA-2Na for 3 weeks), group B(decalcified with EDTA-2Na for 2 weeks), group C(no decalcification), group D(decalcified with EDTA-2Na for 4 weeks). Bone mineral density (BMD)was determined by using dual-energy X-ray absorptionme try (DEXA). And then two pedicle screws were driven in each calf lumbar vertebrae. After that the maximum axial pullout strength(Fmax)and energy absorption were recorded. At last histopathological examination was done in the 4 groups.Results:Means of the BMD, Fmax and energy absorption of group B, A and D were significantly less than those of group C(P<0.01). Means of the BMD,Fmax and energy absorption of group A and D were significantly less than those of group B(P<0.01).There was no significant difference between group A and D(P>0.05).Histopathological examination revealed that the trabecular bones became thinner , their number decreased and the space between them widened , and the antrum of bone marrow enlarged in group A and D compared with group C.Conclusions:An biomechanics model of osteoporotic vertebrae can be established in calf by means of decalcifing fresh calf lumber vertebraes with EDTA-Na2 in several weeks.