ORTHOPEDICS DESIGN >>
of the component in clay or wax, shipping it to the surgeon, and awaiting
approval or input. This process is
often repeated two or three times before a final design is achieved.
Required Technical Skills. Customizing implant design to achieve a perfect
fit requires that technicians have a rare
blend of skills. Designers must understand the specific target anatomy and
the mechanical aspects of joint components, and they must have a working
knowledge of manufacturing processes.
They should also be able to communicate with a surgeon. Without such
skills, producing a customized device is
difficult if not impossible.
Design Process Efficiency. Regardless of whether the orthopedic company
uses clay, 3-D modeling, or computer-aided design (CAD) tools to design the
implant, the traditional design process
involves iterations done on prototype
versions of the proposed design. These
prototypes often move back and forth
between collaborators with iterative
improvements. Surgeons mark changes
onto the model itself, and the model is
then sent back for modification. The
process is fraught with delays. Of the
three-month lead time, a significant
portion of it is lost to shipment or other
unusable time. Because a patient for a
replacement or customized implant is
usually more uncomfortable or more
ill than a typical case, such delays can
be a hardship for the patient.
Suitable Modeling Tools. The traditional CAD 3-D modeling tools used
to design other types of implants may
not be able to support the irregular
shapes and organic curves required in
most patient-specific implants. In addition, the skills needed may be difficult to acquire, resulting in only a few
trained technicians. Creating 3-D mod-
els may take several days as
the hardware and software
computes the math behind
the organic graphics.
Such delays often lead designers to explore nondigital
workarounds. For example,
designers may receive a surgeon’s
marked-up prototype, and then either carve the model out by hand or
place real putty or clay over the area to
be revised to create a physical copy of
the desired implant. If the physical copy
appears to be accurate, the designer
then scans it. Stepping in and out of the
digital work flow introduces imprecision for which the patient may suffer.
Manufacturing Equipment and
Techniques. New, specialized rapid-manufacturing equipment and techniques provide far greater efficiency
in small-volume or one-off runs for
producing a finished custom implant
in a high-strength material such as titanium (the material of choice for many
orthopedic devices). Few hospitals or
research institutions can afford to invest in high-end manufacturing-related
equipment.
Contract Manufacturing. The rise
of rapid manufacturing technologies
means that contract manufacturing
is now available for one-off or short-run projects, not just mass production.
Contract manufacturers may be better
able to justify the cost of dedicated,
expensive tools and manufacturing
options, because they are getting such
custom work from many sources, including teaching hospitals and pioneering surgeons. They are able to support
investments in the specialized people,
software, and output methods for customized implants.
Orthopedic surgeons and device companies may find that outsourcing part
This image shows the newly designed sec-
tion of a hip implant created by FreeForm
in blue. The existing implant is in red.
or all of the process for patient-specific
implants gives them the most flexibility.
The company can retain client contact
and coordination, but enable others
with better economies of scale to provide services that address selected parts
of the process.
Before and after x-rays showing preoperative (left) and postoperative hip condition.
Rise of Custom Technologies
Advances in imaging, design, and
manufacturing technologies are enabling increased availability of customization options. Modeling technologies,
sophisticated imaging, and advanced
manufacturing each play a role. In addition, interoperability between these
processes is crucial to the creation of
successful implants that ultimately lead
to improved patient outcomes.
3-D Modeling versus CAD.
Traditional 3-D modeling packages are best
suited for designing sleek, geometric,
and prismatic products that can be
readily calculated mathematically. They
can also be used for highly procedural
work flows. However, these modeling
systems are limited when it comes to
rapidly producing the complex, organic
shapes of the human body.
Additionally, once an organic-shaped
model is created, the time it takes to
render an image of that model is often
prohibitive. It’s not uncommon for technicians to report waiting 12 hours for
the image of a newly designed new hip
joint to render. When a change is made,
that 12-hour time lag begins again. In
addition, custom implants designed
to mend broken bones have irregular
