Enhancement of acrylic bone cement in vertebroplasty

Vertebroplasty is a new technique in orthopedic surgery for stabilizing fractured vertebra. In this technique acrylic bone cement as a biocompatible material is injected through a cannula inside of vertebra. There are several concerns in this technique that the most serious one is cement leakage out of vertebra. The main reasons are improper viscosity and lack of visibility. Clinicians who practice vertebroplasty use commercial highly concentrated radiopaque acrylic bone cement (more than 25%BaSO[subscript 4] or ZrO[subscript 2]) or a cement with manually added radiopaque agents. High density materials with attenuation under X-ray are good alternatives compared to conventional radiopaque agents (BaSO[subscript 4] or ZrO[subscript 2]) in acrylic bone cement for application in vertebroplasty. In the first part of this study, thermal and rheological properties of modified acrylic bone cement with conventional radiopaque agent (Barium Sulfate, BaSO[subscript 4]) are studied. Additions of barium sulfate are in the form of substitute or excess. In substitute formulation, barium sulfate is replaced with the same weight of powder and liquid to powder ratio kept constant. In the excess formulation, barium sulfate added as excess and liquid to powder ratio decreased. In the second part of this study, high density radiopaque agents are used as alternative radiopacifier. Experimental design technique is used to study the effect of X-ray conditions, concentration, type, and size of radiopaque agents on the visibility of bone cement. The visibility of bone cement was quantified by the measurement of contrast index. In the first project, it was found that the setting time increased with the increase of concentration of radiopacifier in substitute formulation of barium sulfate bone cement. With increase of barium sulfate concentration, excess formulations showed higher residual monomer but for substitute cement, we had a decreasing trend. Acrylic bone cements with excess formulation had higher initial viscosity compared to reference or substitute but the variation of viscosity with time was lower for substitute formulation and cements had higher working time. In the second project, contrast index was the same for barium sulfate, tungsten, and zirconium in the lower voltage but in higher voltage of X-ray lamp, tungsten and zirconium gave higher contrast index. Variation of current in X-ray lamp changed the contrast index of cement slightly compared to the effect of voltage. Bone cement with nano tungsten had higher contrast index compared to the cement with micro size tungsten although micro size zirconium as radiopacifier gave higher contrast index than nano size zirconium