Hi Pat,

Computerized navigation has been around for a long time, in
total hips, total knees, and now hip resurfacing. A lot of
surgeons, including me, have tried it out and not seen an
advantage in all but very exceptional cases. Yet other
surgeons use it on every case.

This is what I think about computerized navigation: It is a
tool which can narrow the “bell-curve” of component
position, but the curve still has some spread. That helps a
surgeon avoid “outliers”, or badly misplaced components.
Navigation does not make component position the exact same
every time, but it helps avoid those outliers. (If it was
the exact same every time there would be no bell-curve at
all.)

So, if a surgeon has no outliers, in other words if he is
doing a good job of keeping his personal bell-curve narrow,
there is no advantage to using computer navigation.
Alternatively, if a surgeon thinks he might accidentally
misalign a component so much that it would be considered an
outlier, the computer may prevent that.

Like any computer, what comes out depends on what went in.
Registering the anatomy (which tells the computer where
everything is) at the beginning of a computer-navigated
operation is not at all an exact science, but depends upon
knowledge and experience. It’s the same with mechanical
alignment jigs. With either method, one should hope that the
surgeon is ready to adjust the verdict of the computer or
the jig to place the component accurately in the bones which
are clearly visible.

Are there any downsides to using a computer? Well, there is
the extra time involved, which prolongs the surgery (think
infections, blood clots). There is extra expense. There is
often one more person in the OR, and more traffic in the OR
can lead to infection. There is the possibility of surgical
complacency if the doctor believes in the infallibility of
computers.

I have heard this discussed at resurfacing meetings, and
people whom I respect more than any others in this field
have tried navigation and declared it “useless”, and a
“waste of time”. While unwilling to go quite that far, it
does make me think I am fine in continuing with mechanical
jigs.

Your question about doctors not having 100% “retention” due
to component malposition requires a reply. Personally, I
have not had any failures in almost 600 resurfacings due to
component malposition. I have 1 femoral neck fracture due to
leg presses 8 weeks after surgery, and one pelvis fracture
resulting from trauma 2 years after resurfacing. That’s it.
But malposition is an important cause of fracture,
wear-related failure, and possibly pseudotumors as well, so
should be avoided.

Any surgeon “young” enough to learn hip resurfacing is
certainly young enough to learn the much easier task of
computer navigation, so people who consider someone too
“old” to learn navigation are being silly.

Similarly, a patient who would choose his surgeon based upon
their use of computer navigation is badly misguided. There
are many much more important issues to consider.

Having said all this, I wouldn’t be surprised if at some
point in the future surgical navigation becomes more
accurate, easier, cheaper, and quicker. Robots will
substitute for doctors. Surgeons will look back on the old
days and shake their heads in amazement that we used to do
all this by hand.

Peter Brooks MD, FRCS(C)
Cleveland Clinic