Mechanical Properties of Blood-Mixed Polymethylmetacrylate in Percutaneous Vertebroplasty

Abstract

Study DesignMechanical study of polymethylmetacrylate (PMMA) mixed with blood as a filler.PurposeAn attempt was made to modify the properties of PMMA to make it more suitable for percutaneous vertebroplasty (PVP).Overview of LiteratureThe expected mechanical changes by adding a filler into PMMA included decreasing the Young's modulus, polymerization temperature and setting time. These changes in PMMA were considered to be more suitable and adaptable conditions in PVP for an osteoporotic vertebral compression fracture.MethodsPorous PMMA were produced by mixing 2 ml (B2), 4 ml (B4) and 6 ml (B6) of blood as a filler with 20 g of regular PMMA. The mechanical properties were examined and compared with regular PMMA(R) in view of the Young's modulus, polymerization temperature, setting time and optimal passing-time within an injectable viscosity (20-50 N-needed) through a 2.8 mm-diameter cement-filler tube. The porosity was examined using microcomputed tomography.ResultsThe Young's modulus decreased from 919.5 MPa (R) to 701.0 MPa (B2), 693.5 Mpa (B4), and 545.6 MPa (B6). The polymerization temperature decreased from 74.2℃ (R) to 59.8℃ (B2), 54.2℃ (B4) and 47.5℃ (B6). The setting time decreased from 1,065 seconds (R) to 624 seconds (B2), 678 seconds (B4), and 606 seconds (B6), and the optimal passing-time decreased from 75.6 seconds (R) to 46.6 seconds (B2), 65.0 seconds (B4), and 79.0 seconds (B6). The porosity increased from 4.2% (R) to 27.6% (B2), 27.5% (B4) and 29.5% (B6). A homogenous microstructure with very fine pores was observed in all blood-mixed PMMAs.ConclusionsBlood is an excellent filler for PMMA. Group B6 showed more suitable mechanical properties, including a lower elastic modulus due to the higher porosity, less heating and retarded optimal passing-time by the serum barrier, which reduced the level of friction between PMMA and a cement-filler tube.

Physical and mechanical characterization of a porous cement for metaphyseal bone repair

“…Anh et al . 17 mixed blood in cement samples, but the reduced Young's modulus has not reached the level of the cancellous bone (545.6 MPa). He et al 23 produced a porous cement by mixing PMMA with NovaBone(r) and chitosan.…”

“…It achieves maximum temperatures lower than the solid cement during drying, thus, decreasing the risk of necrosis. 17 The interconnected pores could allow the fluid to circulate freely, thus reducing the nutritional deficiency of neighboring regions. 18 Furthermore, it can allow invasion of bone tissue within the macropores accompanied by vascular neogenesis.…”

Osteoporotic vertebral compression fractures augmentation by injectable partly resorbable ceramic bone substitute (Cerament™|SPINE SUPPORT): a prospective nonrandomized study

“…However, data on its mechanical and bone integration properties are clear. PMMA Young's modulus (1.8-3.1 GPa) is significantly higher than the normal bone thus interfering mechanically with the load stresses and preventing surrounding bone remodeling; in case of osteoporotic bone, PMMA strength is 8 to 40 times higher [34][35][36][37][38]. Such high stiffness may account for the risk of recollapse of the spared, not impregnated, cancellous bone of the same vertebral body and for the risk of incidental adjacent fractures.…”

Management of osteoporotic vertebral fractures

“…Vertebroplasty mainly involves the application of polymethylmethacrylate (PMMA) to the fracture. This procedure is considered to be very successful in the stabilization of fractured osteoporotic vertebral body and in pain relief 40. A possible alternative is to inject calcium phosphate cement into a vertebral fracture, while in kyphoplasty a balloon is inserted to create space in the fractured vertebra, to restore its height and shape, before the balloch it is removed and the cement is delivered to the resulting space.…”