Preparation and Characterization of Injectable Brushite Filled-Poly (Methyl Methacrylate) Bone Cement

Abstract

Powder-liquid poly (methyl methacrylate) (PMMA) bone cements are widely utilized for augmentation of bone fractures and fixation of orthopedic implants. These cements typically have an abundance of beneficial qualities, however their lack of bioactivity allows for continued development. To enhance osseointegration and bioactivity, calcium phosphate cements prepared with hydroxyapatite, brushite or tricalcium phosphates have been introduced with rather unsuccessful results due to increased cement viscosity, poor handling and reduced mechanical performance. This has limited the use of such cements in applications requiring delivery through small cannulas and in load bearing. The goal of this study is to design an alternative cement system that can better accommodate calcium-phosphate additives while preserving cement rheological properties and performance. In the present work, a number of brushite-filled two-solution bone cements were prepared and characterized by studying their complex viscosity-versus-test frequency, extrusion stress, clumping tendency during injection through a syringe, extent of fill of a machined void in cortical bone analog specimens, and compressive strength. The addition of brushite into the two-solution cement formulations investigated did not affect the pseudoplastic behavior and handling properties of the materials as demonstrated by rheological experiments. Extrusion stress was observed to vary with brushite concentration with values lower or in the range of control PMMA-based cements. The materials were observed to completely fill pre-formed voids in bone analog specimens. Cement compressive strength was observed to decrease with increasing concentration of fillers; however, the materials exhibited high enough strength for consideration in load bearing applications. The results indicated that partially substituting the PMMA phase of the two-solution cement with brushite at a 40% by mass concentration provided the best combination of the properties investigated. This alternative material may find applications in systems requiring highly injectable and viscous cements such as in the treatment of spinal fractures and bone defects.

Nanotechnology for treating osteoporotic vertebral fractures

“…40 However, PMMA bone cements have clear disadvantages, including monomer toxicity, high polymerization temperature detrimental to tissue, a lack of biological potential to remodel or integrate into bone, and excessive stiffness that may cause fracture at the adjacent levels. 41 Among these problems, the lack of capability for osseointegration and excessive stiffness are intrinsic drawbacks that cannot be avoided by carefully adjusting the surgical procedure.…”

Biomechanical behavior of novel composite PMMA-CaP bone cements in an anatomically accurate cadaveric vertebroplasty model

“…Recently, a pre‐mixed cement system has been reported in the literature with the versatility to be tailored for specific applications . The system can incorporate CaP fillers imparting bioactive properties upon the cement without the aforementioned detrimental effects .…”

“…The system can incorporate CaP fillers imparting bioactive properties upon the cement without the aforementioned detrimental effects . The pre‐mixed system allows the cement to reach full swelling thus enabling the complete incorporation of CaP fillers .…”

“…It also has superior rheological properties compared to commercial cements, making injection easier at high viscosities, thereby decreasing the risk of extravasation . The pre‐mixed system allows the cement to reach full swelling thus enabling the complete incorporation of CaP fillers . Recent studies report the performance and efficiency of two composite cements, polymethyl methacrylate‐hydroxyapatite (PMMA‐HA) and PMMA‐brushite, in an in vitro porcine vertebroplasty model .…”

“…The pre‐mixed system allows the cement to reach full swelling thus enabling the complete incorporation of CaP fillers . Recent studies report the performance and efficiency of two composite cements, polymethyl methacrylate‐hydroxyapatite (PMMA‐HA) and PMMA‐brushite, in an in vitro porcine vertebroplasty model . These composite cements were shown to successfully stabilize the fractured porcine VBs and were able to withstand cyclic fatigue loading, however the pre‐mixed cements have not been tested using cadavers.…”