Development of Bioabsorbable Interference Screws: How Biomaterials Composition and Clinical and Retrieval Studies Influence the Innovative Screw Design and Manufacturing Processes

Abstract

The current development of bioresorbable materials provided the support for improvement of the clinical performance of the interference screws used during knee-ligament reconstruction. In general, commercially available biodegradable interference screws used in clinical practice are chemically based on degradable, but now a trend to use biodegradable composite materials using the same synthetic biodegradable polymers as matrix reinforced with biodegradable ceramics could be observed. Hydroxyapatite or tricalcium phosphate are used as ceramics in order to reduce the foreign body reaction and increase osteoconduction and mechanical properties of the biodegradable composite materials. In our study several new design features of an innovative interference screw were proposed in order to ameliorate press-fit fixation without damaging the graft based on clinical experience, retrieval analysis of some failed screw, and finite element simulation. We proposed a self-tapping screw with conical shape and three cutting flutes at the distal end and cylindrical shape at the proximal end. The clinical performance of an interference screw is assured by the combination between the clinical technique, screw design, and biodegradable composite material properties, which guarantees the integrity of the screw during insertion, the tissue regrowth, and the stability of fixation. © Springer Science+Business Media New York 2013.