Resorbable polymeric inserts as a means of enhancing fixation of fractures of porotic bones. I. Stability of mechanical properties and viscoelasticity of the inserts aged in vitro.

Abstract

A titanium screw-poly(L-lactide) medullary insert system intended for use in the fixation of porotic bone fractures was subjected to in vitro ageing at 37 degrees C and pH = 7.4 for up to 6 months. The pull-out force of the screw from the insert and the viscoelastic properties of the insert were measured. The pull-out force did not change up to 6 months of ageing, indicating that the polymeric insert provides a good purchase for the screws. The viscoelastic properties of the insert provides of bone and did not change substantially with temperatures up to 52 degrees C. This indicates that the medullary insert would maintain its properties in vivo even if the body temperature was increased. The molecular weight of the insert at 6 months was reduced by 60%, but the molecular weight reduction did not affect the mechanical properties of the insert.