Bone adhesives for trauma surgery: A review of challenges and developments

The idea of being able to glue bone fragments with a suitable biocompatible adhesive remains highly attractive to orthopaedic surgeons. Yet despite decades of research, no suitable system that fully meets all the many requirements for such an adhesive has yet been identified. This article reviews the requirements and challenges of developing a bone adhesive for fracture repair and also the substantial progress that has been made. Developments in bone adhesives can roughly be classified into two groups: synthetic and biologically-derived/inspired. Early examples of synthetic adhesives include poly(methyl methacrylate) and related polymers, cyanoacrylates and polyurethanes. These materials are characterised by relatively good mechanical properties but often lack the required biocompatibility and biodegradability. More recent adhesive systems based on lactide–methacrylate chemistry therefore attempt to address these issues. Similarly, there is renewed interest in glass ionomer cements and calcium/magnesium phosphate cements. Biological adhesives include fibrin and gelatin-based systems. These have good biocompatibility and biodegradability but lack the cohesive strength to have good adhesion to bone and are used chiefly in soft tissue applications. Newer examples that are looking more promising include adhesives inspired by mussel adhesive proteins and the “sandcastle glue” of the marine worm Phragmatopoma californica. As well as the challenge to develop the adhesive systems themselves a further need is for greater consistency in the testing of adhesion to bone both in vitro/ex vivo and in vivo. Test methods in the literature are reviewed together with considerations for the design of such tests.