Design and Optimization of Resorbable Silk Internal Fixation Devices.
of current material options for internal fracture fixation devices have resulted in a
large gap between user needs and hardware function. Metal systems offer robust
mechanical strength and ease of implantation but require secondary surgery for removal
and/or result in long-term complications (infection, palpability, sensitivity, etc.).
Current resorbable devices eliminate ... read morethe need for second surgery and long-term
complications but are still associated with negative host response as well as limited
functionality and more difficult implantation. There is a definitive need for orthopedic
hardware that is mechanically capable of immediate fracture stabilization and fracture
fixation during healing, can safely biodegrade while allowing complete bone remodeling,
can be resterilized for reuse, and is easily implantable (self-tapping). Previous work
investigated the use of silk protein to produce resorbable orthopedic hardware for non-
load bearing fracture fixation. In this study, silk orthopedic hardware was further
investigated and optimized in order to better understand the ability of silk as a
fracture fixation system and more closely meet the unfulfilled market needs.
Solvent-based and aqueous-based silk processing formulations were cross-linked with
methanol to induce beta sheet structure, dried, autoclaved and then machined to the
desired device/geometry. Silk hardware was evaluated for dry, hydrated and fatigued
(cyclic) mechanical properties, in vitro degradation, resterilization, functionalization
with osteoinductive molecules and implantation technique for fracture fixation.
Mechanical strength showed minor improvements from previous results, but remains
comparable to current resorbable fixation systems with the advantages of self-tapping
ability for ease of implantation, full degradation in 10 months, ability to be
resterilized and reused, and ability to release molecules for osteoinudction. In vivo
assessment confirmed biocompatibility, showed improved bone deposition and remodeling
with functionalization and showed promising feasibility of fracture fixations with minor
adjustments to geometry. The proposed silk orthopedic hardware exhibits high potential
as a resorbable fixation system that can bridge the gap between the current materials
for internal fixation devices.
Thesis (M.S.)--Tufts University, 2014.
Submitted to the Dept. of Biomedical Engineering.
Advisor: David Kaplan.
Committee: Sam Lin, Fiorenzo Omenetto, and David Kaplan.
Keywords: Biomedical engineering, Biomechanics, and Materials Science.read less