Can Resorbable Fixation Screws Replace Titanium Fixation Screws? A Nano-Indentation Study.

PURPOSE: The aim of this study was to compare the nano-hardness and elastic modulus of titanium and resorbable screws and determine whether resorbable screws could completely replace titanium screws.

MATERIALS AND METHODS: The mechanical properties (nano-hardness and decreased elastic modulus) of TriMed titanium, resorbable Inion CPS, and Synthes RapidSorb samples were measured using a nano-indentation technique. In this study, a Hysitron TriboIndenter TI 950 with a resolution less than 1 nN and a displacement resolution of 0.04 nm was used for the nano-indentation tests. The unloading segments of the nano-indentation curves were analyzed using the method of Oliver and Pharr (J Mater Res 7:1564, 1992).

RESULTS: Statistical analysis showed that the values of the elastic modulus and nano-hardness of the TriMed titanium screws were significantly higher than those of the resorbable Inion CPS and Synthes RapidSorb screws (P < .05). A statistical difference was not observed between the values of the elastic modulus and the nano-hardness of the Inion CPS and Synthes RapidSorb screws (P > .05).

CONCLUSIONS: In this study, the resorbable screws were found to be soft and flexible compared with the titanium screw. According to the results of this nano-indentation study, resorbable and titanium screws cannot be used interchangeably.