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Computer-assisted surgical navigation of the hip is a relatively
new field. Dr. Murphy first performed computer-assisted peri-acetabular
osteotomy in 1995 and total hip replacement in 1997 with most
primary total hips being replaced routinely with computer-assistance
beginning in 2001.
Regarding total hip arthroplasty, the two most important
technical challenges are accurate placement of the acetabular
component and accurate measurement of leg-length change during
surgery. These two problems can typically be very well managed
using computer-assisted surgical navigation. Proper acetabular
cup positioning can be challenging because the patient's pelvis
moves around during hip replacement surgery and it's impossible
to know the exact position of the pelvis at the moment that
the acetabular cup is being inserted unless the motion of
the pelvis is tracked during surgery. Even taking xrays during
surgery has limitations because the exact angle of the xray
is not known so precise measurements are difficult to make.
Acetabular component malposition can lead to an increased
likelihood of a number of problems including accelerated wear
of the hip, bone loss around the hip due to the wear debris,
impingement of the components, or dislocation of the hip and
can lead to repeat surgery for any of these problems. Using
computer assistance to measure the position and orientation
of the acetabular cup during its insertion is a very important
application of surgical navigation since improved component
positioning inevitably leads to a lower incidence of all of
these problems.
Computer-assisted surgical navigation involves fixing reference
frames to the pelvis and the femur. Reference frames are shaped
a bit like small starfish and are temporarily fixed to the
bone with small pins. An infrared stereoscopic camera can
follow the movements of the reference frames during surgery
so that the surgeon knows exactly where the bones are during
surgery. All of the important surgical instruments also have
reference frames on them. Since we can track the positions
of the bones and surgical instruments simultaneously, it is
possible to measure the position of the instruments and implants
within the bone so that important decisions about size, position
and alignment of the components can be accurately tracked
during surgery.
We have performed computer-assisted total hip replacement
in more than 600 procedures to date. This is the largest series
of image-guided, computer-assisted total hip replacements
in the United States. Data of acetabular cup position in hips
replaced with and without surgical navigation clearly show
that surgical navigation greatly improves the accuracy of
acetabular cup placement. In addition to navigation of acetabular
component insertion, we have developed very efficient methods
of measuring leg-length change during surgery which greatly
facilitate our ability to assess the leg length change being
achieve at surgery compared to our surgical goals.
Most of these computer-assisted total hip replacements are
also performed using tissue-preserving, minimally invasive
techniques. The combination of less-invasive surgical techniques
and image-guided surgical navigation holds much greater promise
than either of the new techniques alone. When considering
all of these issues though, each patient should remember that
the true goal of hip replacement surgery is to have a well
functioning hip for 10 or 20 years. Whether a patient can
walk well without crutches at 3 or 6 or 9 or 12 weeks isn't
really the most important issue. All of our newer techniques
must always be thought of with the long-term goals in mind.
For more information about computer-assisted surgical navigation,
click on the references below.
Publications:
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