Summary
The purpose of this study was to compare the holding powers of 2.7 mm pre-tapped and
self-tapped screws placed closely together and tightened in small bones. Pairs of
metatarsals were collected from healthy, skeletally mature Greyhounds and part of
a 2.7 mm dynamic compression plate was fixed to the dorsal surface of each bone using
three 2.7 mm screws. Identical screws were used throughout but only one of each pair
of bones had threads pre-cut using a tap prior to insertion. All of the screws were
tightened before the constructs were mounted in a materials testing machine and the
centrally placed screw was loaded incrementally until failure. Load-deformation curves
were plotted and yield point, ultimate load to failure, stiffness and energy prior
to yield point were measured. Mean values were recorded for each parameter and Student's
T-test was used to test the null hypothesis that there is no difference in holding
power between pre-tapped and self-tapped screws. Significant mechanical differences
were not found between pre-tapped and self-tapped screws placed closely together and
tightened into small bones. Self-tapped screws can be considered for use in small
animal surgery even when multiple screws are to be placed closely together in relatively
small pieces of bone.
Keywords
Screws - pre-tapped - self-tapped
