|
|
Warning: include(electromagneticnavigation.htm) [function.include]: failed to open stream: No such file or directory in /home/content/p/a/t/pat45750/html/electromagneticnavigation.php on line 24
Warning: include() [function.include]: Failed opening 'electromagneticnavigation.htm' for inclusion (include_path='.:/usr/local/php5/lib/php') in /home/content/p/a/t/pat45750/html/electromagneticnavigation.php on line 24
Electromagnetic navigation: TKA tool for accurate bone cuts, soft tissue
balancing Link
http://www.orthosupersite.com/view.asp?rid=24918
By Susan M. Rapp
ORTHOPAEDICS TODAY INTERNATIONAL 2007; 10:20
November 2007
Results of total knee arthroplasty performed using electromagnetic
navigation systems have begun to show this technology’s potential as
an intraoperative asset for joint replacement surgeons.
But before orthopaedic surgeons can fully embrace this type of
navigation for regular use, the systems need to undergo more
improvements and refinements, according to Mark A. Hartzband, MD.
Hartzband has used electromagnetic navigation in more than 100 total
knee arthroplasty (TKA) cases over the past 2 years and analyzed its
pros and cons.
“There are some distinct positives. It is fast and it is easy. There
are no pins to bang into or get into your field. You don’t have to
modify your exposure,” he said in a presentation at the 10th Annual
Insall Scott Kelly Institute Sports Medicine and Total Knee & Hip
Symposium in New York.
Hartzband noted some system improvements are underway in the form of
new electromagnetic navigation instruments that are intuitive to use
and easy to align inside small incisions. They may eliminate
traditional instrumentation altogether.
With these developments on the horizon, he believes the popularity
of electromagnetic navigation systems should increase, although
system cost remains an issue.
“These are expensive systems and that has been what has limited
[their] growth in this marketplace,” Hartzband said.
Hartzband discussed the differences between electromagnetic
navigation and the more popular optical tracking systems. An
electromagnetic system eliminates the need for special cameras,
percutaneous pins and calibrating surgical instruments. “It is much
easier to handle in terms of line of sight than an optical system,”
he said
Hartzband uses electromagnetic navigation during TKA as a reference
point for making bone cuts and soft tissue balancing. “I prefer to
use it as a check rather than as a guide,” he said.
“It is a nice teaching tool as long as you don’t make it the only
teacher in the room,” he said.
After completing dynamic reference frame placement, the system
screen displays the tibial and femoral landmarks.
Once Dr. Hartzband makes the navigated cuts in the femur, he will
navigate the tibial cuts. After placing the components, he relies on
electromagnetic navigation to help complete soft tissue balancing
and check kinematics.
Electromagnetic navigation systems work via an electromagnetic field
generated by a hand-held emitter, which can be moved around the
operating field. Instruments are equipped with a magnetic coil
designed to work with the system. As each one is introduced it
disrupts the electromagnetic field. The system’s computer, which has
special tracking software, then recognizes the instrument and its
three-dimensional location in the surgical field.
Before starting a navigated TKA procedure, the surgeon inserts two
dime-sized dynamic reference frames (DRF) through small incisions
made above and below the knee joint and fixes them with cortical
screws.
The incisions are made in the anteromedial femur and inframedial
tibia.
The surgeon then digitizes the center of the hip on-screen and uses
that data and information from the DRFs as reference points for
finding tibial and femoral surgical landmarks.
“I think landmarking is really the secret difficulty in all these
navigated cases,” Hartzband said, adding that accurate landmarks are
essential for a good outcome. They not only define the knee’s
baseline kinematics before TKA, but improve the accuracy of
subsequent femoral and tibial bone cuts.
Electromagnetic navigation also avoids the need to place optical
pins, which can add up to 20 minutes to the surgery. “There is a
morbidity to drilling extra pin sites. … You always have the ugly
risk of a stress riser at a pin site and potential fracture,”
Hartzband said.
“It is particularly advantageous for complex cases, the problem
being you have to be good at the simple cases if you are going to
bring it into a complex case,” he said.
The system’s extramedullary technique for navigating bone cuts is an
advantage over ones that use intramedullary devices, since it does
not push any of the patient’s fat into the system.
For more information:
Mark A. Hartzband, MD, can be reached at Hartzband Joint Replacement
Institute, 10 Forest Ave., Paramus, NJ 07652, U.S.A.;
+1-201-291-4040; e-mail: mahartzband@aol.com. He has indicated he is
a consultant to and receives research support and royalties from
Zimmer Inc.
Reference:
Hartzband MA. Electromagnetic navigation in TKA. Presented at the
10th Annual Insall Scott Kelly Institute Sports Medicine and Total
Knee & Hip Symposium. Sept. 14-16, 2007. New York.
|
|
