Three types of volar slab cast were evaluated by simulating a
flexion moment at the wrist. All cast types accommodatedapproximately 40–70 mm of deformation prior to failure. The
double thickness cast was the strongest supporting a load of
152 N. The reinforced single thickness cast supported a load of
126 N and the single thickness cast supported
66 N prior to
failure. Surprisingly all casts were found to be capable of providing
load support up to 60% of their original strength, even after initially
being loaded past their ultimate strength.
The much lighter (220 g) reinforced single thickness cast was
found to have equivalent strength and support to the heavier
double thickness cast (395 g) yet it was much stronger and similar
in mass to the single thickness cast (180 g). Therefore, the
reinforced single thickness cast should provide a stable, light,
cost-effective and relatively simple way of improving cast
application. The results suggest that by customising the geometry
of standard plaster casts the mechanical properties of volar slabs
can be improved significantly.