NMP‐modified PMMA bone cement with adapted mechanical and hardening properties for the use in cancellous bone augmentation

Abstract

The use of polymethylmethacrylate (PMMA) to reinforce vertebral bodies (Vertebroplasty) leads to an increase in the Young's modulus of the augmented vertebral body. Fractures in the adjacent vertebrae may be the consequence thereof. Hence, PMMA with a reduced Young's modulus may be suitable for vertebroplasty. The goal of this study was to produce and characterize stiffness-adapted PMMA cements. Modified PMMA bone cements were produced by adding N-methyl-pyrrolidone (NMP). Young's modulus, yield strength, polymerization temperature, setting time, and hardening behavior of different cements were analyzed. Focus was on the mechanical properties of the material after different storage conditions (in air at room temperature and in PBS at 37 degrees C). The Young's modulus decreased from 2670 MPa (air)/2384 MPa (PBS) for the regular cement to 76 MPa (air)/320 MPa (PBS) for a material composition with 60% of the MMA substituted by NMP. Yield strength decreased from 85 MPa (air)/78 MPa (PBS) to 2 MPa (air)/24 MPa (PBS) between the regular cement and the 60% composition. Polymerization temperature decreased from 70 degrees C (regular cement) to 48 degrees C for the 30% composition. The hardening behavior exhibited an extension in handling time up to 200% by the modification presented. Modification of PMMA cement using NMP seems to be a promising method to make the PMMA cement more compliant for the use in cancellous bone augmentation in osteoporotic patients: adjustment of its mechanical properties close to those of cancellous bone, lower polymerization temperature, and extended handling time.

The mechanical behavior of PMMA/bone specimens extracted from augmented vertebrae: A numerical study of interface properties, PMMA shrinkage and trabecular bone damage

“…The remaining three were augmented with a modified low-modulus cement. In this case, the same preparation procedure was used, but 50% of the Vertecem monomer was replaced with NMP (1-Methyl-2-Pyrrolidone, Sigma Aldrich, Buchs, Switzerland) as described in Boger et al (2009). Vertebroplasty was performed via a unipedicular approach by an experienced surgeon as in clinical practice.…”

The effects of bone and pore volume fraction on the mechanical properties of PMMA/bone biopsies extracted from augmented vertebrae

“…The standard cement (Vertecem, Synthes GmbH, Oberdorf, Switzerland) was prepared according to the manufacturer's instructions. The same procedure was used for the lowmodulus cement, but 50% of the monomer was replaced with NMP (1-methyl-2-pyrrolidone, Sigma Aldrich, Buchs, Switzerland) as described in Boger et al (2009). Vertebroplasty was performed by an experienced surgeon under continuous radiographic monitoring with an eight gauge side opening needle in a unipedicular approach.…”

“…In other studies (Baroud et al, 2003;Boger et al, 2008), PMMA was injected into trabecular bone biopsies, which may lead to different cement porosities compared with vertebral augmentation. The mechanical behaviour of such composites is important for understanding biomechanical changes in the spine after augmentation and, therefore, for the development of new cement materials such as low-modulus cements (Boger et al, 2009).…”

The effect of standard and low-modulus cement augmentation on the stiffness, strength, and endplate pressure distribution in vertebroplasty

“…The same was used for the low-modulus cement, but 50% of the liquid monomer phase was replaced with NMP (1-methyl-2-pyrrolidone, Sigma Aldrich, Buchs, Switzerland) as described in [21]. The cranial/caudal surfaces were covered with hard plastic disks.…”