feature ADDITIVE MANUFACTURING
this purpose, but all have fallen short of the ideal, either in strength, required Disclaimer: The views expressed in this article are those of the author and do not
sterilisation method, available size, aesthetics, or tissue integration. reflect the official policy of the Department of Army, Department of Defense or US
Government.
The technology we selected for building our cranioplasty plates was the Electron
Beam Melting technique (EBM), which was commercialised by Arcam
3
. There are REFERENCES:
many reasons for this, including build speed, material certification, completed 1 Invibio Inc., 300 Conshohocken State Road, West Conshohocken, PA
part metallurgy and availability. Qualification data on the Electron Beam Melted 19428
Ti6Al4V-ELI for implants has been published in Bone Zone and other 2 Porex Surgical, Inc, 15 Dart Road, Newnan, GA 30265-1017
publications. Crucial criteria in our selection were material choice, the build 3 Arcam, AB, Krokslätts Fabriker 27A, SE-431 37 Mölndal, Sweden
speed (e.g. feasibility and cost) and the ability to provide certification of the 4 Materialise, Technologielaan 15, 3001 Leuven, Belgium
material to established ASTM standards for implantable medical devices. 5 SensAble Technologies, Inc., 15 Constitution Way, Woburn, MA 01801
The implants are designed after segmenting the CT scan data using Mimics
4
. i EOS GmbH recently announced, “EOS PEEK is the first PEEK material
3Matic
4
and/or FreeForm Modeling Plus
5
are used for the actual implant design. that can be processed on the high-temperature system EOSINT P 800.
The implant is designed with fixation plates already attached, and combination PEEK is considered to be one of the highest performing thermoplastic
mesh and solid where desired. The approval for the design is obtained from the polymers and as such is seen as a promising material for the future.
surgeon prior to sending the file to the EBM machine for building. A skull model The material is especially suitable for the medical industry because of
is created using a stereolithography machine and sent along with the completed its excellent properties, such as flame retardancy, biocompatibility and
implant to the surgeon. sterilisability.”
In order to prove the viability of the technologies' use for trauma patients, our
BIBLIOGRAPHY:
goal is to keep the entire process, from CT scan to delivery of the finished
C. Ngo, G. Kulesha, R. Zhang (2007). The Osseointegration of Porous
implant, to seven days. In most cases, we are successful. Some of the problems
Materials Using a Rabbit Femoral Defect Model. Materials & Processes
that we have encountered include intermittent build failures, machine availability
for Medical Devices Conference (pages 203¬-204). ASM International.
and shipping delivery delays.
Methner, M. (2007, March/April). The Clean Alternative. Time
Compression Technologies (pages 43-46).
Unlike milling machines, the EBM, DMLS, and SLM machines require constant
monitoring and checking to ensure that the part produced is actually within the
The 3D Medical Applications Center, part of the Department of
specifications prescribed and that no warping has occurred. The Ti6Al4V powder
Radiology at the Walter Reed Army Medical Center, Washington, D.C., is
must be monitored for oxygen content. The final part must be checked for
a complete bio-medical rapid prototyping and manufacturing service
accuracy, and testing performed on test coupons to ensure that the build
bureau. Funded by the Army Medical Department, we provide bio-
metallurgy is within specifications. Due to the expense of the equipment, most
models and implants to all military medical centres, as well as the
smaller manufacturers will not have backup equipment available, so careful
Veterans Administration Healthcare System. Established in October
preventive maintenance is a must to ensure machine availability and delivery
2002, with a grant from the Army Office of the Surgeon General, we
schedules.
opened for business in December 2003.
The bottom line for this entire process is the ability to build an implant that is
The 3D Medical Applications Center has been the primary medical rapid
designed for a specific patient's needs, that reduces the OR time requirement
prototype and implant provider for the United States Department of
significantly and provides better outcomes with more resistance to infection.
Defense since 2004. We have been very heavily involved in all types of
More than 40 cranial plates have been produced using this process, with an
reconstructive surgery involving combat trauma, as well as non-combat
average surgical time of 90 minutes from first incision to completion of suturing.
trauma and disease.
This compares with two to six or more hours previously. The time savings can be
directly attributed to the improved implant design and attached fixation. Large
While our primary mission is supporting our surgeons in their treatment
implants were previously multi-piece constructs and were slower to place and
of combat casualties, we have been heavily involved in many surgeries
fixate.
on family members and retirees. Our involvement has ranged from pre-
and post-surgical medical models, to custom PMMA
ABOVE LEFT: Patient specific bone plate built with EBM
ABOVE RIGHT: Bifrontal Ti mesh implant ready in operating theatre
(polymethylmethacrylate) and Ti6Al4V cranial implants, subperiosteal
dental implants, facial bone implants and custom fixation devices.
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