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This screen shot demonstrates the computer-predicted position of a femoral fracture during manipulation. The image at the lower right shows the calculated antetorsion and femoral length, which can then be matched to the data obtained for the contralateral intact femur during the reduction.
Courtesy of David M. Kahler, MD

AAOS Now

Published 8/1/2008
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Annie Hayashi

Computer-guided surgery: Is time invested well or wasted?

Computer navigation for femoral fracture reduction

“With computer-guided surgery, we now have a tool that can reduce fractures with a high degree of accuracy,” David M. Kahler, MD, of the University of Virginia, told participants at the AAOS/Orthopaedic Research Society Advanced Imaging and Computer-Assisted Surgery of the Knee and Hip research symposium. “Femoral fractures are an ideal application for this technology.”

“Computer-guided surgery enables orthopaedic surgeons to precisely match the length and the rotation of the intact femur when inserting a femoral nail and locking it in place,” he said. “Using standard tools, up to 30 percent of femoral fractures are either short or significantly malrotated.”

Dr. Kahler also pointed out that computer-guided surgery can reduce the time fluoroscopy is used to as little as 15 seconds—considerably less than the 3 minutes required during the standard technique—exposing both the patient and the surgeon to less radiation.

A useful alternative
Although preparation time for computer-guided surgery is longer, the navigational planning and elimination of repetitive fluoroscopy can reduce the time required for the actual surgery. Using navigation for a femoral fracture requires approximately 20 to 25 minutes of preparation before the surgery actually starts.

Tracking stars are attached to the proximal and distal fracture fragments and images are taken that will be stored and used throughout the surgery. “Well-leg data” is also gathered for comparison purposes. Finally, the unreduced fracture is manually segmented for the fracture reduction.

Dr. Kahler uses computer-guided surgery on a selective basis. “For a short oblique fracture when I am not worried about length, I wouldn’t use navigation because I do think it adds some operating room time despite the benefits and reduction in radiation exposure,” he said.

Navigation: Does it help?
“Orthopaedic surgeons are now able to take stored images of the unreduced fracture in the operating room and, by attaching trackers to either side of the fracture and using the computer, predict where the fracture is going when it is manipulated,” explained Dr. Kahler.

“Instead of having our hands in the C-arm beam while we’re pushing a fracture into place and trying to pass a guide wire across a femoral fracture, we are able to manipulate the fracture with a reduction rod and see, in real time, where the fracture is going without actually doing ongoing real-time imaging.

He finds computer-guided surgery to be a very satisfying procedure. “I can leave the operating room with a report that shows that the operated femur is 442 mm long and 22 degrees in anteversion, for example, and that the contralateral leg is 421 mm and 19 degrees in anteversion. The anatomy of the contralateral side has been almost precisely matched, which should be the goal of fracture surgery.”

Annie Hayashi is the senior science writer for AAOS Now. She can be reached at hayashi@aaos.org