Dr. Brooks Discusses Computer Assisted Navigation for Hip Resurfacing

[Pat Walter]

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