Summary
Mechanical testing was performed to evaluate an acrylic steel repair paste when used
in the construction of external fixators. Individual pin-bar-acrylic constructs were
compared with those made from Kirschner-Ehmer (KE) clamps or polymethylmethacrylate.
The constructs were subjected to cantilever bending forces, pin-pullout tests and
cantilever bending after undergoing cyclical fatigue. Forty mm segments of acrylic
were significantly stronger than medium ESF clamps. Twenty-five mm segments of acrylic
were of equivalent strength to clamps. Ten mm segments failed under physiological
loads expected from dogs greater than 20 kg and were less likely to provide adequate
pin coverage to protect against pin pull-put. The placement of a wire loop to secure
the pin-bar intersects made application of the acrylic easier but did not alter stiffness.
There was not any significant variation between different operators in the strength
of their constructs nor tolerance of their constructs to pin pullout. Cyclical loading
forces were applied to acrylic-pinbar units without significant loss of strength,
and acrylic and polymethylmethacrylate units did not show any difference in stiffness
after being subjected to cyclical fatigue. The acrylic steel repair paste is a handkneadable,
fast setting, inexpensive and readily available acrylic for use in the construction
of external fixators. It allows more flexibility in frame design than a clamp and
on the basis of mechanical testing offers a very stiff and secure substitute for KE
clamps or polymethylmethacrylate.
Keywords
Acrylic - polymethylmethacrylate - fixator - clamp
