The Biomechanical And Cement Leakage And Cement Dispersivity Study Of The Different Bone Mineral Density Embalmed Vertebral Body After Vertebroplasty

Objective: Percutaneous vertebroplasty is an effective and rapid method in treating osteoporotic vertebral compression fracture,it can not only relief or relieve the pain,but also recover the stability of the spine.Clinical workers use PKP in the treatment of osteoporotic compression fractures consider that the patients with low bone mineral density has more desirable in the recovery of vertebral height and kyphosis angle.Foreign scholars Xie W and other studies consider that the risk of bone cement leakage will lead to increased in the patients of high bone mineral density.But some academicians experimentally believed that the vertebral body of low bone mineral density are more likely to occur cement leakage in PVP.Previous studies have shown that the recovery of the intensity and stiffness after PVP is influenced by many factors,such as the type of vertebral fracture,the amount of bone cement,the injection time,the injected location and the biological characteristics of bone cement.Whether the recovery of intensity and stiffness,the leakage rate of bone cement,and the diffusion of bone cement in vertebral body are affected by bone mineral density has few reported in recent years.The purpose of this study is to explore the differences of biomechanical and cement leakage among different bone mineral density(BMD)embalmed vertebral body after vertebroplasty.Methods:45 vertebral bodies were harvested from nine embalmed cadavers.T11-L3 centrums were dislodged.The fractures,tumors and congenital malformation were ruled out by X-ray.Each specimen resected the paravertebral muscles,the upper and lower endplate and the intervertebraldisc,the anterior and posterior longitudinal ligament and soft tissue.45 single free specimens were made.BMD of the vertebral body was measured using Dual Emission X-ray Absorptiometry DEXA.According to their BMD,vertebral bodies were divided into 3 groups: preferable bone mass group(A,n=10),general bone mass group(B,n=10),poor bone mass group(C,n=10).All specimens were selected to made into compression fracture model by the biomechanical machine for further test.Each vertebrae was then compressed at a speed of 5mm/min until the vertebral body fractured.The fracture was confirmed by the nonlinear deformation in a real-time load-deformation graph.After fracture,vertebroplasty was done using low-viscosity bone cement(doughing time)from the same manufacturer by pedicle with 2.5ml bone cement injection for each vertebral body,all vertebral bodies underwent unilateral vertabroplasty.Position of needle and bone cement were monitored via C-arm X-ray machine.The cement leakage rate and distribution of cement were assessed with the reference of postoperative CT scan.The biomechanical testing was carried out before the fracture and after cement injection.Before testing,the initial load of 100 N was applied to the specimen in order to simulate the physiological state of the vertebral body and reduce the creep.Every vertebral body specimens were compressed at a speed of 5mm/min up to 500 N.The pressure and the linear displacement are respectively recorded by the sensor in the test machine and output to the computer.The intensity and stiffness of the vertebral body after bone cement injected were recorded.The difference of intensity between the three groups was analyzed by multiple mean comparison,The difference of the recovery in stiffness between the groups was tested by the rank sum test of multiple sample mean.The Fisher exact probability method was used to determine the difference of leakage rate between the groups.Results:In group A,B and C the intensity after cement injection were(5178.43±903.17)N,(4630.49±504.542)N and(3476.67±757.29)N.The stiffness were(427.01±171.85)N/mm,(302.76±70.95)N/mm and(385.67±101.49)N/mm.After vertabroplasty the intensity was statistically significant between 3 groups(F =13.772,P=0.000),the stiffness was no significant difference(X2=4.376,P=0.112).The leakage rate was higher in group A than in group B and C.Conclusions:The results of this study indicate that : The BMD,maximum load strength and bone cement leakage rate were positively related after vertebroplasty.The recovery of stiffness was not influenced by BMD.The higher the bone density,the better the diffusion of bone cement in the vertebral body.The results of this study can provide theoretical reference for clinical treatment.