Biomechanical Comparison Between Unilateral And Bilateral Percutaneous Vertebroplasty For Osteoporotic Vertebral Compression Fractures

Background:The osteoporotic vertebral compression fracture(OVCF)is the most common type of OP-related fracture.OVCF has an incidence of 7.8/1000 person-years at 55–65 years.At 75 years or older,the incidence increases to 19.6/1000 person-years in females and5.2–9.3/1000 person-years in males.Pain is the most common symptom.To solve this problem,percutaneous vertebroplasty(PVP),a minimally invasive surgical technique,was developed in recent years.PVP can quickly stabilize the facture and relieve pain through the percutaneous injection of bone cement into the fractured vertebral body.Currently,PVP has been widely used in clinical practice to treat OVCF and can be divided into unilateral percutaneous vertebroplasty(UPVP)and bilateral percutaneous vertebroplasty(BPVP).However,with the development of the PVP promotion and research,postoperative complications of PVP can adversely affect patients’ long-term quality of life,such as recompression of the PVP-operated vertebrae,new fractures at the neighborhood vertebrae,bone cement leakage,degenerative disc disease(DDD),and pulmonary embolism.Postoperative complications of PVP are closely related to biomechanics,and at present there is little biomechanical evidence on UPVP and BPVP.Therefore,from the perspective of biomechanics,it is necessary to explore which injection methods can reduce the incidence of complications after PVP.Objective:The purpose of this study was to compare biomechanical differences between UPVP and BPVP by 3D model and biomechanical simulation software,and to explore the effects of different approaches on postoperative complications of PVP.Methods:Based on the computer tomography image of a healthy subject,the heterogeneous assignment finite element(FE)model of T11-L1 was constructed and validated by using Mimics 21.0,Magics 21.0,3-matic 13.0,Hyper Mesh 20.0 finite element analysis software.A compression fracture of the vertebral body was performed at T12.UPVP and BPVP were simulated by the difference in the distribution of bone cement in T12.A moment of 7.5 Nm combined with a pre-compressive load of 500 N was implemented to simulate spinal flexion,extension,left/right lateral bending,and left/right axial rotation.Stress distributions and the maximum von Mises stresses of vertebrae and intervertebral discs in the fractured model,UPVP and BPVP were compared.In addition,the rate of change of maximum displacement of T12 between UPVP and BPVP was also evaluated.Results:There were no obvious high-stress concentration regions on the anterior and middle columns of the T12 vertebral body in BPVP.Compared with UPVP,the maximum von Mises stress on T11 in BPVP was lower under left/right lateral bending,and the maximum von Mises stress on L1 was lower under flexion,extension,left/right lateral bending,and left/right axial rotation.For the T12-L1 intervertebral disc,under all loading conditions,the maximum von Mises stress of BPVP was less than that of UPVP.The rate of change of maximum displacement of T12 after BPVP was less than that after UPVP under the six loading conditions.Conclusion:BPVP could balance the stress of the vertebral body,reduce the maximum stress of the intervertebral disc,and offer advantages in terms of stability compared with UPVP.In summary,BPVP could reduce the incidence of postoperative complications and provide promising clinical effects for patients.