Computer aided navigation is an interesting concept. However, there is no evidence that it leads to better clinical outcomes and fewer failures. On the other hand, there is ample evidence that surgeon experience has a dramatic effect on outcomes and complications.
One way to conceptulize this is that the experienced surgeon’s brain is a computer with much more sophisticated “software” than a navigation computer. When a computer is programmed, an algorithm must be created which has certain inherent limitations. Furthermore additional significant sources of errors are introduced by the registration of anatomic points for the navigation computer in surgery.
My personal opinion is that navigation that is based on a pre-operative CT scan data, which is being pioneered by Justin Cobb, has tremendous promise in the future to improve the results. At this point, we are still in the early development phase. It will probably add several thousand dollars to the cost of each operation.
In summary, I believe the right kind of navigation surgery based on accurate 3D CT scans holds tremendous promise for the future. It will still require an extensive amount of preliminary development work before it is ready for routine use.
Interestingly, an article just published in JBJS British by Olsen et al (91-B, 2009, pp 1281-86) confirms a low level of repeatability in computing the most basic measure of neck-shaft angle. There are much more important factors to proper alignment than the stem angle, but it turns out the navigation doesn’t even do well with this simple task. This points out that imageless navigation needs to be validated by CT before we give it any credibility.