Comparative study of orthopaedic screws
Tuokko, Tiia Kirsikka (2016)
2016
Materiaalitekniikan koulutusohjelma
Teknisten tieteiden tiedekunta - Faculty of Engineering Sciences
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Hyväksymispäivämäärä
2016-11-09
Julkaisun pysyvä osoite on
https://urn.fi/URN:NBN:fi:tty-201610174602
https://urn.fi/URN:NBN:fi:tty-201610174602
Tiivistelmä
Anterior cruciate ligament (ACL) is one of the major ligaments in the knee. It can be injured during sports activities but is relatively easy to repair arthroscopically by using a graft and interference screws, for example. Increasing amount of interference screws are nowadays made from biodegradable material instead of traditional metal. The development of interference screws is heading toward composite materials due to the possibility to combine desired properties of different materials.
The aim of this study is to characterize and compare two interference screw pro- totypes made from composite material. The difference between the sample screws is the filler content, 30 w-% for RE0034 samples and 40 w-% for RE0036 samples. Mechanical properties of these samples were characterized by shear and pull-out tests and also some material analyses were performed to describe inherent viscosity, monomer content, thermal properties, dimension changes and mass loss.
Test results show that there are noticeable differences between the samples. Especially in shear test it is clearly seen after 4 weeks of degradation that RE0034 samples are significantly better than RE0036 samples. However, in pull-out test there is not that significant difference but that can be explained by the complex test method which describes fixation properties rather than pure material properties. In addition, material analyses support the observation that RE0034 samples are mechanically better, in other words, have slower degradation, than RE0036 samples.
Even though it can be concluded that RE0034 samples have better degradation profile compared to RE0036 samples, the decrease of mechanical properties is still too fast for interference screw-like application. This is due to the 12-week healing time of tendons which should be covered by the implant and now the strength retention is not sufficient. Nevertheless, this study provides good baseline data of the new composite material. Further material development and evaluation are needed to optimize the degradation behaviour of this composite material.
The aim of this study is to characterize and compare two interference screw pro- totypes made from composite material. The difference between the sample screws is the filler content, 30 w-% for RE0034 samples and 40 w-% for RE0036 samples. Mechanical properties of these samples were characterized by shear and pull-out tests and also some material analyses were performed to describe inherent viscosity, monomer content, thermal properties, dimension changes and mass loss.
Test results show that there are noticeable differences between the samples. Especially in shear test it is clearly seen after 4 weeks of degradation that RE0034 samples are significantly better than RE0036 samples. However, in pull-out test there is not that significant difference but that can be explained by the complex test method which describes fixation properties rather than pure material properties. In addition, material analyses support the observation that RE0034 samples are mechanically better, in other words, have slower degradation, than RE0036 samples.
Even though it can be concluded that RE0034 samples have better degradation profile compared to RE0036 samples, the decrease of mechanical properties is still too fast for interference screw-like application. This is due to the 12-week healing time of tendons which should be covered by the implant and now the strength retention is not sufficient. Nevertheless, this study provides good baseline data of the new composite material. Further material development and evaluation are needed to optimize the degradation behaviour of this composite material.