The Research On The Bone Cement Augmentation Of New Pedicle Screw

Objective:1. To infuse decalcifying solution by infusion pump into sheep lumbar vertebrae and place the anterior vertebral body into a glassware filled with decalcifying solution to establish a fast, biomechanical, high controllable model similar to osteoporosis in sheep lumbar vertebrae. 2. To research under what degree of osteoporosis, injecting PMMA into the PMI-NPPS will increase screw stability and reach the biomechanical level of vertebra with normal BMD. To provide the theory supports for whether the use of PMMA when we ues PMI-NPPS in patients with different degree of osteoporosis in clinical practice. 3. To study the relationship between the dose of PMMA and Fmax.To give effective theory supports to the the use of PMMA dosage in clinical practice.Methods:1. Making a special cylindrical perfusion connector and a systematic decalcying device 2. Making 80 fresh lumbar vertebras from 2.5-35 years sheep 3. Take specimens into the BMD tests after the preparation of dividing the specimens into four parts randomly by completely randomized design and decalcifying each one for 0h, 2h, 4h, 6h separately.( group A: no decalcification;group B: decalcified with 3%Hcl for 2 hours;group C:decalcified with 3%Hcl for 4 hours; group D:decalcified with 3%Hcl for 6 hours) 4. Statistical analysis is carried out on the BMD of all groups and work out the percentage of the BMD loss in group B、C and D. Take the four groups into the CT tests separately. 5. Inject the PMI-NPPS into the first half vertebra of group B(group B1)and inject the PMI-NPPS+1.5ml PMMA into the second half(group B2). Carry out the biomechanical test separately. Get the conclusions :is the biomechanical level of the second half not only much more better than the previous half, but also reach the the level of vertebra with normal BMD(group A)? 6. Take the group C and D into the same operation with step 5. 7. Make 50 vertebras of group C and divide them into five parts randomly by completely randomized design. Inject the PMI-NPPS+PMMA into the samples separately with different PMMA dose(0ml、0.5ml、1ml、1.5ml、2ml). And then do biomechanical tests in order to find the relationship between the PMMA dose and Fmax.Result:1. After decalcifying the vertebras for 2, 4, and 6 hours, the BMD of them decrease by 18.3%、28.0%、40.8% individually. 2. CT shows the vertebras with the normal BMD owns the characteristics of uniform density, clear pictures and high density. However, the vertebras experienced the decalcifying process reveal low density, this phenomenon becomes more obvious in the transverse process parts as well as in the middle of vertebras. The longer time the decalcifying process experience, the more obvious this trend will be. 3(1). Fmax and E in the group B2 is(936.60±70.16)N and(2.00±0.13)J,these present the radical difference after making a comparison with group B1(P<0.05),however, these don’t display the apparent differences while comparing with group A(P>0.05). 3(2). Fmax and E in the group C2 is(891.59±47.97)N and(1.89±0.07)J,these present the radical difference after making a comparison with group C1(P<0.05),however, these don’t display the apparent differences while comparing with group A(P>0.05). 3(3). Fmax and E in the group D2 is(531.50±35.61)N and(1.14±0.10)J.,these present the radical difference after making a comparison with group D1(P<0.05),meanwhile, these do display the apparent differences while comparing with group A(P>0.05). 4. Inject the PMI-NPPS+PMMA into the sample of group C with different PMMA dose,Fmax will increase when PMMA dose becomes higher and higher. Fmax is linearly associated with the PMMA dose, the linear regression equation isy=312.25x+418.75( R2=0.977)Conclusion:1. The method of placing the anterior vertebral body into a glassware filled with acid and infusing acid by infusion pump into sheep lumbar vertebrae can be useful for producing a quick and effective biomechanical model similar to osteoporosis, it provides reference data for biomechanical study. 2. Under the condition of osteopenia and osteoporosis,injecting PMMA into the PMI-NPPS will increase screw stability and reach the biomechanical level of vertebra with normal MBD. Under the condition of severe osteoporosis,injecting PMMA into the PMI-NPPS will increase screw stability but it cannot reach the biomechanical level of vertebra with normal MBD. It provides the theory supports for whether the use of PMMA when we ues PMI-NPPS in clinical practice. 3. Under the condition of osteoporosis,when we inject PMMA into the PMI-NPPS, Fmax of PMI-NPPS+PMMA will increase when PMMA dose rises within certain range, but we must consider the risk of bone cement leakage,which gives effective theory supports to the the use of PMMA dosage in clinical practice.