Highlights
- •Screw hole merging could markedly enhance fatigue lives of locking plates.
- •Partial thread removal could significantly increase the fatigue lives of plates.
- •Removing 1/3 of threads in merged hole does not affect the screw's holding power.
- •Offset holes in locking plates can reduce fatigue lives significantly.
Abstract
Background
This study investigated the effects of screw hole merging, thread removal, and screw
hole offset on the mechanical properties of locking plates.
Methods
Finite element models were used to develop the optimal design of the merged holes.
Four titanium locking plates with different hole designs were analyzed. Type I had
threaded round holes. Type II had merged holes. Type III had merged holes with partial
thread removal. Type IV had threaded offset holes. Mechanical experiments similar
to finite element analyses were conducted and compared. Screw bending tests were used
to assess the screw holding power.
Findings
Finite element analyses showed the optimal merging distance between two round screw
holes was 3.5 mm with 2/3 circumferences in each hole. The stresses of types II and
III were respectively 6.42% and 7.33%, lower than that of type I. The stress of type
IV was 1.66% higher than that of type I. In the mechanical tests, the fatigue lives
of types II and III were respectively 3.86 and 7.16 times higher than that of type
I. The fatigue life of type IV was 37% lower than that of type I. The differences
in the bending strengths of screws were insignificant.
Interpretation
Merging holes could mitigate screw hole stress and increase the fatigue lives of the
plates significantly. Partial thread removal could further improve the fatigue life.
Merging holes and thread removal did not decrease the screw holding power significantly.
The fatigue lives were significantly decreased in plates with offset holes.
Keywords
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Article info
Publication history
Published online: May 06, 2022
Accepted:
May 3,
2022
Received:
January 6,
2022
Identification
Copyright
© 2022 Elsevier Ltd. All rights reserved.
