06/07/2016 Jeff Root
When capturing casting for orthotics, should you bill a casting fee? (Steven Latter, DPM)
While the subject of casting originally began as a
billing question, it has turned into a much broader
and more complex discussion. Although it may seem
rudimentary, let’s review the objectives when casting
the foot for the manufacture of custom, functional
type foot orthoses. The purpose of casting is to
create a three dimensional representation of the
foot. While that sounds simple enough, we must ask
what areas or surfaces of the foot need to be
captured in the cast and what position should the
various joints of the foot be placed in during the
casting process?
When casting for a functional type foot orthosis,
ideally we want the cast to be an accurate anatomical
model of the plantar surface of the foot, the
posterior surface of the heel (for bisection
purposes), the medial and lateral sides of the foot
and the toes. The more anatomical surface (i.e.
information) the lab has when making the orthosis,
the better. A properly taken plaster-of-Paris (POP)
cast reflects these surfaces and also captures skin
lines and other anatomical features and landmarks. In
addition, a POP cast enables the practitioner to
determine the specific position of the joints of the
foot during casting, which directly influences the
three dimensional contour of the negative cast and
the resulting orthosis.
In summary, the ideal cast will enable the
practitioner to position the joints of the foot in
the desired position, will capture all necessary
surface areas and ideally will provided skin lines,
lesions, bony prominences and any other important
anatomical features. For these reasons, many people
consider POP to be the gold standard by which all
other methods of casting or scanning should be
judged. The primary disadvantages of POP casting are
that it is more time consuming, messy and requires
cleanup.
An impression foam cast (IFC) is quicker and cleaner.
The primary disadvantages of an IFC is that it
provides less anatomical contour and information and
the joints of the foot cannot be positioned like they
can in a POP suspension cast because impression foam
casting is a semi-weight bearing casting technique.
An IFC is especially problematic when trying to
position the midtarsal joint during casting. When
comparing the contour of a POP cast to an IFC of the
same foot, there is a considerable loss of foot
contour and arch height in the IFC due to ground
reaction force, especially in more mobile type feet.
While some orthotic manufacturers advocate
accentuating the medial arch by intentionally
plantarflexing or supinating the forefoot in the
impression cast, the position of the midtarsal joint
is still greatly influenced by ground reaction force.
Resin casting socks (RCS) are quicker and less messy
than POP, do enable suspension casting and therefore
the ability to positon the joints of the foot. The
disadvantages are that there is some loss or change
in anatomical contour due to the nature of the
casting material, tension from the elastic band,
tissue compression and the fact that there is a
plastic bag between the foot and the skin.
POP, IFC and RCS all produce negative, physical
models of the foot. These models can be used to
create POP positive casts for use with traditional
orthotic manufacturing techniques (i.e. manual
fabrication) or can be scanned to create digital
files for use with computer aided design and
manufacturing (CAD/CAM) systems. It is important to
note that with most, if not all CAD/CAM systems, the
superior aspect of the negative cast (POP or RCS)
must be cut off so that the laser can “see” the
interior, plantar surface of the cast during the
scanning process. This will result in some loss of
surface area and data but it is necessary to prevent
the laser’s view from being obstructed by the walls
of the negative cast. This is not necessary when
scanning an IFC since the foam is compressed, causing
the cast to become vertical along the outer margins
of the foot.
Many, if not most labs use CAD/CAM systems for
manufacturing the majority of their orthoses. There
are a number of different manufacturing systems in
use today. The nature and capability of these
different systems vary and is an important factor in
the quality of the finished orthosis. The cast or
scan of the foot is really just the beginning of the
process.
The use of technology to take the place of the
aforementioned physical casting methods is an
important consideration for the practitioner. Some
electronic casting systems use laser light while
others use white light or even pressure to create a
digital model of the foot. How is the practitioner
supposed to determine or compare the accuracy of one
system to another? Without some type of independent
testing, verification and certification, they have no
way of verifying the capability of the system to
replicate the shape of the foot. One cannot simply
assume that all these systems are equally accurate,
especially given their significant technological
differences.
While these casting systems were originally larger
and more expensive, recent technology has made the
use of IPads and smartphones an option for creating
digital files for producing orthoses. These newer
systems present a whole new set of challenges. For
example, a 3D scanner can be attached to an IPad. The
scanner (IPad) must be held several feet away from
the foot and it must be moved all around the foot in
order to capture the foot’s surface. As a result, it
may not be possible for the practitioner to hold the
foot and scan it at the same time. While these
scanners are capable of capturing a great deal of
surface area, they may require an assistant and/or a
change in casting technique. Some companies advocate
just letting the foot hang during scanning. This
technique is inconsistent with the needs of the
practitioner who wants to manually position the
joints of the foot during casting.
In this age of evidence based medicine there is
little evidence that the practitioner can use to
evaluate and select one of these electronic casting
systems. Logically, some systems do seem to have some
advantage when we compare the digital file (output)
of one system to another. For example, a pressure mat
system is similar to impression foam in that the
practitioner can’t position the midtarsal joint in
the same way they can with a non-weight bearing
system and there will be some loss of contour due to
pressure acting on the plantar surface of the foot.
So if placing the foot in a non-weight bearing
position, placing the joints in a specific
position/relationship, capturing the non-weight
bearing contour of the foot and capturing the
posterior surface of the heel for bisection purposes
is important to the practitioner, then they need to
choose a foot scanner that is capable of achieving
these goals.
It has been my experience that no casting material,
technique or system is right for everyone and each
has advantages and disadvantages. The practitioner
must decide what they what to achieve with their
orthoses and which casting method or system can best
help them achieve their goals. They must weigh out
the advantages and disadvantages of each option when
making their decision. For some, the quality of the
cast is their highest priority while for others it
may be ease of use, cost, profit, efficiency, space,
etc. In most cases it is a balance of several key
factors that helps determine what is best for the
individual practitioner. For example, reduced
turnaround time and reduced shipping costs might sway
the practitioner to use a foot scanner in spite of
some of the scanners negative characteristics.
Determining which casting techniques and systems are
worthy of reimbursement or how much that
reimbursement should be will no doubt create
passionate debate, especially by those who have a
vested interest in it. Ultimately, one can only hope
that scientific evidence and not just clever
marketing is what practitioners base their decisions
on. Clearly we have a long way to go until we have
sufficient evidence to guide us on this subject.
Jeff Root, President, Root Laboratory, Inc.
