Effects Of Different Concentrations Of MC-PMMA Bone Cement On The Compressive Strength And Stiffness Of Porcine Osteoporotic Vertebra In Vitro

Objective:The modified vertebral model of porcine osteoporosis was strengthened with modified MC-PMMA bone cement with different MC/PMMA ratios,and the changes in compressive strength and stiffness of the strengthened model were observed to explore the most appropriate MC-PMMA concentration ratio in PVP surgery.Methods:Twenty-five fresh and normal adult male Bama miniature pigs with 150 thoracolumbar vertebrae were measured,and the bone density of each vertebral body was measured using a dual-energy X-ray bone densitometer.Then the specimens were treated with EDNA-NA₂decalcification solution to obtain the model of osteoporotic vertebral body in porcine.A dual-energy X-ray bone densitometer was used to screen pig vertebral models that met the osteoporosis criteria?-3.5<T value?-2.5?.A total of 128 vertebral models met the standard.Using the digital random method,120 osteoporotic vertebral models were randomly selected and randomly divided into 6 groups?A,B,C,D,E,F?,each with20 vertebral models.Group A is regarded as a blank group.In the experiment,MC-PMMA bone cement was divided into 5 groups according to different MC/PMMA ratios:0%,5.0%,10.0%,15.0%,and20.0%,which were injected into groups B,C,D,E,and F respectively.In the 5 groups of vertebrae,1 ml of MC-PMMA material was injected into the pedicle of both vertebrae?0.5ml left and right?.Each saline cement strengthened vertebral body was wrapped with normal saline gauze and placed in a double-sealed plastic bag.To simulate physiological conditions,the strengthened vertebral body was placed in a 37?incubator for 24 hours to make bone cement fully aggregate with the vertebral body.Then the enhanced vertebral body with good dispersion of bone cement was obtained under three-dimensional spiral CT.Finally,the average compression strength and stiffness of the vertebral bodies of each group were measured by compression mechanics experiments using a high-frequency fatigue tester.Results:1.The average BMD of all vertebrae before decalcification was1.200±0.046 g/cm2;the average of BMD after decalcification of meet the standard of vertebrae was 0.700±0.030 g/cm².The difference was statistically significant?P<0.05?.2.Bone mineral density between vertebral bodies after decalcificat-ion:Group A:0.716±0.031 g/cm2;Group B:0.696±0.023 g/cm2;Group C:0.702±0.041 g/cm²;Group D:0.685±0.028 g/cm²;Group E:0.706±0.024 g/cm²;Group F:0.697±0.026 g/cm²,there is no statistically significant difference between the groups?P>0.05?.3.The vertebral body resistance of each group Compressive strength:Group A:6.27±0.46 MPa;Group B:16.31±0.78 MPa;Group C:14.98±0.49 MPa;Group D:14.92±0.38 MPa;Group E:14.68±0.29 MPa;Group F:15.31±0.31 MPa.After osteoporotic vertebral body of B-F group was strengthened with MC-PMMA bone cement with different concentrations,the compressive strength of vertebral body of each group was significantly enhanced,and there was no significant difference between the strength comparison groups?P>0.05?.4.The stiffness value of each group:Group A:762±75 N/mm;Group B:1372±70 N/mm;Group C:1314±86 N/mm;Group D:1007±78 N/mm;Group E:959±77 N/mm;group F:1350±66 N/mm.With the change of MC-PMMA bone cement concentration,the stiffness of the strengthened vertebral body changes,and when the MC concentration is 15%,the stiffness of the corresponding strengthened vertebral body is the lowest.Conclusions:1.After vertebroplasty,the MC-PMMA bone cement with different proportions significantly increased the vertebral strength.2.When the MC concentration in MC-PMMA bone cement is 15%,the stiffness of the vertebral body after strengthening is the lowest.