| dc.description.abstract | Over the last decade, biodegradable screws and plates have received wide
acceptance over metallic fasteners for orthopedic fracture fixation. A biodegradable
fastener would gradually "disappear" during healing of a fractured bone or tissues,
therefore avoiding a secondary operation to remove that fastener. When using a metal
fastener, the current approach requires manual threading on a large bone fragment for
fixation. This technique is difficult when it is required to fixate a small bone fragment.
This study puts forth the development of a threadless, polymer based orthopedic fastener
for small fragment fixation which would provide stability and interfragmental
compression to the fracture site.
The fastener was designed with ratchets on its surface, which deflect during
insertion into the drilled hole in the bone and subsequently stiffen to hold the bone
fragments in place due to interference. The head of the fastener was developed
analogous to a Belleville washer which deflects during insertion of the fastener and
subjects the bone fragments to interfragmental compression. Finite element analysis
(FEA) was conducted to design the fastener profile and assess its performance. The
push-in and pull-out forces predicted by FEA were comparable to the experimental
results for the prototype of the microfasteners. The push-in force was found to increase
with increasing insertion depth and radial interference. The force required to initiate
pull-out was maximum and was reduced with reducing fastener bone contact. An
analytical model was proposed to explain the fastener bone interaction. It was found to
be in good agreement with the FEA and experimental results at low levels of
interference. | en |
