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Total Knee Replacement (TKR) surgeries are becoming increasingly common globally as
an effective measure to counter knee arthritis. Total knee replacement implants are very
advantageous in a sense that they offer 99% success rate to patients. This thesis presents
the design, simulation and additive manufacturing of a patient specific, Functionally
Graded Lattice Structure (FGLS) knee implant in Ti 6Al-4V alloy with specific reference
to the healthcare situation in Pakistan. This was to explore the local manufacturing facilities
of Pakistan as all knee implants are imported from abroad.
The strategy involved a high degree of workflow consisting of Computer-Aided Design
(CAD), finite element analysis (FEA), and topology optimization using nTopology to
create Gyroid-based lattice work. The structures were to resemble the trabecular bone
structure to ensure that stiffness discrepancies were minimized. This helped counter only
one drawback of solid knee implants, stress shielding.
The simulations of the physiological loading conditions (static and cyclic) demonstrated a
Von Mises peak of 620.45 Mpa and safety factor of 12.66 on the average and unlimited
predicted life of fatigue of over 10^7 cycles. The use of FGLS was effective in making the
weight of 490 g to 292, leading to a 40 percent weight reduction, with no structural integrity
lost. Selective Laser Melding (SLM) was used to fabricate the implant and the heat
treatment allowed stress relieving of the additively manufactured implant.
Compressive testing was also mechanically vindicated to be on an of average 95.02 kN
with little variation and Micro-CT scanning confirmed high dimensional fidelity and
showed internal lattice geometries without defects. According to this research, SLM
produced FGLS implants usage has proven to be an option to traditional prosthetics, which
is mechanically stable, biologically desirable, and cost-effective, and has a bright future of
being a locally manufactured orthopedics product.