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Navigation can make a good surgeon better
Optimal alignment can be only 5 minutes away, with the benefit of avoiding surgical outliers.
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All good surgeons have great surgical instruments to use, why not include computers? We use computers everyday of our lives, with laptops, palm pilots, etc. Computers are already everywhere in our operating rooms — our anesthesiologists use them for their OR records, our nurses chart with them and our X-rays are only available on computer screens. The newer models for surgical navigation are smaller, are less expensive, have more memory, quicker, and they can solve some alignment problems.
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If you want to keep your knees aligned within ±3° and want to spend only 5 minutes doing it, use computer navigation.
It can make a good surgeon even better and help avoid outliers. We have digitized long-standing postop radiographs to show that computer navigation can improve alignment accuracy and improve component position.
It also can help us with soft tissue balancing. There are some cognitive pilot studies on fat embolism that show that manipulating the medullary canal can lead to problems.
If you do not want to violate the medullary canal, use computer navigation. This may ultimately be the most important reason to switch to computer navigation.
Most computerized navigation systems use an infrared camera to pick up a tracker on the femur and on the tibia. They can allow you to bring in navigated instruments and can be used with any implant system.
Getting optimal positioning
Image: Hofmann AA |
Computers can allow us to look at our results to see how close we are to optimal positioning. I have performed thousands of knee implant surgeries.
When I looked at my last non-navigated implants retrospectively with full-length radiographs, I found that I was aligned to ±3° in only 92% of the tibias and only aligned 90% of the time on the femoral side.
However, I was 100% aligned on the tibia and 98% aligned on the femur when I switched to computer navigation.
Computer navigation may sound a bit intimidating at first, but we only use five instruments: trackers on both the femur and the tibia, a pointer, a device that picks up the posterior condyles with a claw, and something we call “Mickey Mouse,” which is a navigated blade that tracks the position of the standard instruments.
The position of the femur and the tibia can be tracked by the camera through trackers, which are attached onto each of the bones with two 1/8 inch pins.
By taking the leg through 14 different positions, it mathematically calculates where the femoral head is.
I don’t need to make a hole in the femur and violate the medullary canal.
There are only seven reference points that you have to enter into the system:
- the femoral entry point;
- the posterior femoral condyles;
- where you would normally put the entry hole in the tibia;
- the PCL;
- the medial third of the tubercle; and
- the medial and lateral malleoli.
Now you are ready to operate. This only takes about 5 extra minutes. The remainder of the surgery uses standard instruments … the same instruments I use every single day.
Computerized navigation may help any surgeon, experienced or not, by letting him or her know the exact leg alignment while allowing use of standard instruments.
For more information:
- Aaron A. Hofmann, MD, can be reached at 50 N. Medical Drive, Room 3-B165, Salt Lake City, UT 84132-0001; 801-587-5400; e-mail: aaron.hofmann@hsc.utah.edu.
Reference:
- Hofmann AA. Navigation: Not ready for prime time — Disagree. Part of Symposium K; Controversial issues and hot topics in primary total knee replacement, given at The American Academy of Orthopaedic Surgeons 74th Annual Meeting. February 15, 2007. San Diego.