Cobra Cast
Cobra Casts are frequently used
for MC fractures and many
casting departments use them
to treat tendon injuries. Fingers
should have padding wrapped
between them prior to casting
to prevent maceration and the
hand must be in the POSI (Figure
1) to safely rest the soft tissues
and
facilitate
faster
rehabilitation after casting.
Figure 3 shows a full Cobra Cast,
which will require splitting for
the first week to allow for
swelling.
The split would
completed at 1 week with
synthetic. The cast can stay
insitu for the healing period or,
providing it can be removed
safely, i.e. retaining reduction of
the fracture, be replaced with a
synthetic cast once swelling is
reduced. Complete casts are
more sturdy and harder for
patients to remove.
They,
therefore,
maintain
the
reduction better. However, the
cast often has to be changed at
1 week because they have
become loose due to the
reduction in swelling. (See
Figure 7 for information on
casting materials).
Finger Splints
Figure 3: Cobra Cast
normally be along the dorsal
surface but not over the
fractured metacarpal. In some
cases, a plaster slab in this
position is used as an
alternative.
Complete or Full Casts
If a full plaster cast is used the
cast must be split to allow for
swelling. The cast can then be
March 2018 L.O.G.I.C
Finger fractures may be
treated with buddy
strapping only, but
some require splints to
hold them out to length
and stop displacement.
These will normally be
buddy strapped after
their post reduction X-
ray.
Thumb Spica
The most common thumb
injuries
are
metacarpal
fractures and Ulna Collateral
Ligament (UCL) Injuries (Figure 4
& 5). X-ray should be taken
before stressing the UCL
because if there is an avulsion
fracture stressing it can cause
displacement. When testing the
UCL the uninjured thumb
should be assessed first for a
comparison and the thumb
should be stressed flexed to
isolate the tendon. If there is
significant laxity a thumb splint
or cast will be needed for 3
weeks. If there is no end point,
i.e. the joint keeps opening
when stressed because there’s
no tendon to hold it, referral to
hand surgeon for further
management is required.
Thumb spicas go from the tip of
thumb to wrist area the length
will depend on the injury. They
are two pieces of plaster slab
placed in a T shape on the
thumb, one length wise and one
across it, then bandaged on. For
a UCL, the thumb must not be
not abducted (sticking out) as
this further stresses the tendon.
Scaphoid Fractures
Although
many
casting
departments include the thumb
in a cast for a scaphoid fracture
(Figure 6), the Bone Shop has
found that this does not
improve healing and leaving the
thumb out enables more joint
movement and less joint
stiffness. Unless indicated by
pain on thumb movement, a
below elbow casts without the
thumb included is used. Clinical
scaphoid
fractures
with
tenderness in the anatomical
“snuff box” but no radiological
changes will be treated either in
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