Developers Take Pains to Develop Spinal Implant
Millions of Americans suffer
from back problems, prompting the
healthcare industry to pump large
sums of money and vast resources into
therapies and treatments each year.
In 2005, for example, $86 billion was
spent on treating back problems, up
65% from 1997. In the same period,
$24 billion was spent for in-patient
treatment of back ailments, including
surgeries. Thus, when Vertebral
Technologies Inc. (Minnetonka, MN;
www.vti-spine.com) decided to develop
an interbody fusion device for the spine
that relieves pain while providing a
customized fit for the patient, it knew
it was tapping into something big.
Used to relieve back pain after
other therapies have failed, InterFuse
fuses two vertebral bodies together.
“The device provides support and
stability at the intervertebral disk
space,” says Mark Rydell, design
engineer at Vertebral Technologies.
“It also allows for fusion across the
disk space through fenestrated areas
in the implant that are filled with
autologous bone.” Because the device
can be inserted via a 9-mm posterior
annulotomy—an incision through the
strong outer ring of fibers surrounding
the spinal disks—its implantation is
less invasive than surgery requiring an
abdominal incision.
Designing and fabricating the implant
entailed collaboration between Vertebral
Technologies and a group of materials
and service providers, including Invibio
Inc. (Woodbury, MN; www.invibio.
com), a vendor of medical-grade and
implantable biomaterials. “We chose
Invibio because it was the only company
at the time that made an implantable
grade of PEEK,” Rydell states. “Their
product is used in other fusion devices
and is known by the FDA.”
InterFuse can be implanted less invasively
than devices requiring abdominal incisions.
Invibio had been working with
Vertebral Technologies since its
inception on implantable devices,
states David Hawks, Invibio’s business
development manager. “For the
InterFuse device, we provided a
biomaterial that is mapped to the
specific needs of this minimally
invasive spinal device, considering
mechanical performance, the device’s
design requirements, and the delivery
approach.” Its PEEK Optima enabled
the development of a segmented
device with properties that could be
achieved through injection molding.
Medical Extrusion Technologies, Inc.
Innovative Solutions for Custom Extruded Tubings
Specialized Capabilities for Unique Process Requirements
After material selection, Vertebral
Technologies generated a device
design and then turned to Minnesota
Rubber and Plastics (Minneapolis;
www.mnrubber.com), a molder
and assembler of elastomer and
thermoplastic products. The vendor
molded the implant into a near net
shape and coordinated the manufacture
of the initial machined prototypes.
Facilities in California• Minnesota• Texas
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Prior to manufacturing, Minnesota
Rubber performed mold-flow analysis,
material molding characteristics, tool
design, and other engineering steps,
according to Jim Beyer, the company’s
technical sales representative. After
mold validation, adjustments were
made to provide a robust, capable, and
repeatable process. The dilemma, he
explains, was to design and build tooling
for injection-molded plastic components
that would enable the OEM to invest as
little money as possible while minimizing
postmold machining operations.
Minnesota Rubber decided that
for the initial iteration, the most cost-effective approach was to concentrate
all the smaller and larger part designs
into the three largest basic molded
components, or blanks, minimizing the
amount of PEEK Optima that would
have to be removed during machining.
Email your requirements for immediate
quotation to: MET@MedicalExtrusion.com
26608 Pierce Circle • Murrieta, CA 92562 • 800-618-4346 • PH: 951-698-4346 • FX: 951-698-4347• Email: MET@MedicalExtrusion.com
www.MedicalExtrusion.com
We put ALL the
Implant-grade PEEK Optima can
cost significantly more than titanium
and other standard implant materials,
remarks James Evans, president
and general manager of Rochester
Medical Implants (Rochester, IN;
www.rmi.us.com). Thus, the company’s
task was to devise a cost-effective
means of handling the InterFuse blanks
made by Minnesota Rubber and milling
them to the final specifications.
pieces together,
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The 16 different InterFuse part
sizes consist of three component
types each. With 48 assemblies to
machine, Rochester had to develop
a flexible programming scheme to
accommodate quick changeovers for
small product runs. Thus, it developed
three generations of custom fixturing,
each of which was achieved using
a formal Kaizen methodology that
enabled continuous improvement from
generation to generation. Based on this
approach, the company has developed
a five-axis process that enables it to
mill up to 30 InterFuse segments in
one machine cycle using a single CNC
vertical milling machine.
We create possibilities to improve quality of life
for humankind, one person at a time.
Ph: 651.633.4200 Fax: 651.633.5486 www.donatelle.net
See us at MD&M East 2009, Booth 842
Rochester helped decide which
features should be machined and which
should be molded, and it developed
a system for machining 48 different
segment shapes. —B.M.
