Bioactive PMMA bone cement

Background

For more than 50 years PMMA-based bone cement has been in clinical use practically unchanged in its composition mainly in orthopaedic surgery for the routine fixation of joint endoprostheses.
Other areas of use are the filling and reconstruction of bone defects, and in recent years, PMMA-based bone cement is increasingly being used for minimal invasive stabilization of osteoporotic fractures especially of the vertebra (vertebroplasty). It is one of the most common biomaterials implanted with direct contact to bone tissue.

A considerable disadvantage of PMMA bone cements, however, is their poor bioactivity, or respectively, missing osteoconductivity. This prevents the implanted material from being actively integrated into bone, and instead, it is encapsulated by a connective tissue layer. A good fixation of bone cement can only be achieved by sufficient interlocking between cement and the surrounding cancellous bone. Reliable clinical results are therefore only achieved by demanding implantation techniques. At the same time, good penetration of the cement into cancellous bone complicates later implant revision, as it is always accompanied by loss of the reinforced spongiosa.

Bioactive PMMA bone cement

We develope bioactive PMMA-based bone cements, which show a significantly higher bone affinity index compared to conventional non-modified PMMA bone cements, indicating a highly significant increase in bioactivity. Furthermore, we could demonstrate that our bioactivation concept does not deteriorate important material properties like mechanics (compression strength, bending strength), setting reaction (doughing time and setting time, hardening temperature) and monomer release. Several commercial PMMA-bone cements were successfully subjected to our modification for bioactivity, demonstrating that this technology is of general applicability.

Figures

REM images of the surface of non-modified PMMA bone cement (above)
and of bioactivated PMMA-bone cement (below) (scale each 4 µm).

Publication

In September 2010 the results have been published to some extend:
Mechanical properties and drug release behavior of bioactivated PMMA cements.
Vorndran E, Spohn N, Nies B, Rößler S, Storch S, Gbureck U
J Biomater Appl 2010 Sep 6 online first

This project was supported by the German Federal Ministry of Education and Research (BMBF, Funding number: 01EZ0609).