136 - Biomechanical Characteristics of Cement/Gelatin Mixture for Prevention...

#136 Biomechanical Characteristics of Cement/Gelatin Mixture for Prevention of Cement Leakage in Vertebral Augmentation

Basic Sciences-Research

Poster Presented by: Z. Luo

Author(s):

B. Meng (1)
M. Qian (1)
Z.X. Zeng (1)
S.X. Xia (1)
H.L. Yang (1)
Z.P. Luo (1)

(1) Department of Orthopedics of (1) st Affiliated Hospital and Orthopedic Institute at Soochow University, Suzhou, China

Abstract

Purpose: Percutaneous vertebroplasty (PVP) or percutaneous kyphoplasty (PKP),as an important and effective surgical technique, has complications,especially cement leakage. The objective of this study was to evaluate whether or not the addition of gelatin micro-particles into the polymethyl methacrylate (PMMA) could reduce cement infiltration in vertebral cancellous bone.

Methods: Dynamic viscosity, permeability, compressive and bending tests were tested. Bone cement consisted of 10 g PMMA powder and 5 ml liquid monomer. Gelatin micro-particles were prepared in three size groups: 0-125 µm, 125-250 µm and 250-500 µm,and mixed with cement in different density(1%, 2% and 3%). The mixed cement viscosity was tested by NDJ-8S rheometer,which was recorded from 20% to 90% twisting every 30 seconds for 10 minutes.

Cylindrical core samples ( 13.3±0.2 mm in diameter,20.2±3.1 mm in height ) were harvested from fresh bovine vertebrae. Permeability of the cement mixture through the vertebra was tested on an Instron E10000 mechanical test machine and calculated using Darcy's law (Q=κA(Pb-P0)/µL).

The compression was performed at a rate of 5 mm/min with 4 mm maximum in deformation on cylindrical samples (6.0±0.1 mm in diameter and 13.0±0.1 mm in height). The speed of 4 mm/min was maintained in bending test on Rectangular cement blocks (75±0.1 mm in length, 3.3±0.1 mm in thickness and 10±0.1 mm in width).

The structures were examined by scanning electron microscopy (Hitachi Company, Japan) at an accelerating voltage of 15 kV. The specimens were sputter-coated with gold for 40 s at 100 mA using a sputter coater (Eiko, Hitachi, Japan).

Results: The 3% gelatin cement showed the highest viscosity and the most rapid increase in viscosity, and the largest size tested (250-500 µm) possessed the highest viscosity(p< 0.001).

Significant reduction of cement permeability in cancellous bone was determined after addition of the micro-particles. Micro-particles of 2% in density and 125-250 µm in size decreased the permeability by 1/3 without significant change in viscosity.

The biomechanical strength remained unchanged under compression, but decreased by up to 15-20% in bending with the increase of particle size and density.

Conclusion: Gelatin micro-particles significantly reduced PMMA permeability in vertebral cancellous bone, but did not affect compressive and flexural strength of the PMMA. The inclusion of gelatin could offer a more manageable approach for surgeons to prevent the cement from leakage in vertebral augmentation.