In the operating room, orthopaedic trauma surgeon David Kahler (right) and 4th-year resident John Thaller are assisted by a computer system that helps them more precisely and safely guide implant devices as they repair a hip socket fracture.

October 13, 2003 -- Fluoroscopy is an essential tool in the operating room for an orthopaedic surgeon. This standard portable X-ray imaging unit allows surgeons to repair severe bone fractures with very small incisions. But it has limitations: It exposes both surgeon and patient to significantly high levels of radiation – the equivalent during some procedures of 1,000 chest X-rays. And at times it requires the surgeon to resort to trial and error when inserting devices needed to mend broken bones.

At the University of Virginia Health System, these major drawbacks have been almost completely eliminated by bringing fluoroscopy into the realm of virtual reality.

Virtual fluoroscopy brings a computer and digital camera into the O.R., where they are interfaced with implant devices and a standard fluoroscopic unit – all equipped with high-tech reflectors that allow the camera to track their – and the patient’s – position during surgery. This system provides surgeons with mathematically precise, real-time guidance when planning and placing bone fixation guides and screws and tools to reduce the angle and gap between bone fragments (fracture reduction).

Computer Guidance Has Widespread Potential

UVa surgeon David Kahler, M.D., who specializes in orthopaedic trauma, has been a crusader for virtual fluoroscopy, a form of computer-assisted orthopaedic surgery with potentially broad applications. He was in fact the first in the United States to use it for hip socket and pelvic fractures – common injuries in car accidents – by adapting what is generally known as image-guided surgery (IGS), used by neurosurgeons since the 1980s. IGS is an emerging field in orthopaedics, where it’s being used not only in trauma cases but also in joint replacement, spine fusion and skeletal deformity correction. Eventually, Kahler believes, virtual fluoroscopy will prove to be suitable for the 70 percent of orthopaedic trauma cases that use fluoroscopy.

"In terms of volume of potential applications, virtual fluoroscopy represents the biggest advancement in computer-guided surgery in the past decade," says Kahler, who recently gave a presentation in Spain on the topic as the new president of the International Society for Computer-Assisted Orthopaedic Surgery. "It’s the Holy Grail for orthopaedic surgeons. It allows us to do a fracture reduction and place implants without having to do major surgical exposure. We’ve been able to do that in certain types of fractures simply by using a fluoroscopic unit in the operating room. But that only gives us one view at a time, and so we must position the guide wires or screws in one view, and then obtain additional images in other planes for trial and error placement. With virtual fluoroscopy we can store multiple X-ray images on a computer to create a multiplanar virtual model of a patient’s skeleton and let the computer show us the best path for these instruments – without having to expose our hands and the patient to repeated X-rays."

Kahler first brought a computer and camera to assist him in the operating room in the late 1990s. He has since shared at conferences worldwide the remarkable benefits he’s tracked over the past few years: He’s reported, for instance, that when using virtual fluoroscopy in more than 30 iliosacral screw placements for the repair of SI joint, sacral or crescent fractures, he noted no complications or screw malpositions. Furthermore, virtual fluoroscopy saved more than one minute of fluoroscopic time for each screw placement – equivalent to 250 chest X-rays – and saved on average 9.2 minutes per screw in operating time.

He’s also reported that he can do an entire intramedullary nailing of femoral shaft fractures with six seconds of fluoroscopy time instead of the three-and-a-half to four minutes it normally requires.

Other applications of computer guidance

These images show a guide wire’s computer-generated projected path (green line) and its actual path (red line) for insertion of a femoral mail. By using a computer to help plan and guide the tool’s insertion into the bone, a surgeon doesn’t need to take repeated X-rays and eliminates intraoperative radiation exposure.

Kahler is pleased to see his colleagues in the UVa Department of Orthopaedics utilizing IGS in their areas of expertise: Thomas E. Brown, M.D., plans to soon combine computer guidance to assist in minimally invasive hip replacements. D. Greg Anderson, M.D., has been using computers and cameras for the past two years to perform minimally invasive spinal fusions, known as microTLIF, for degenerative disc cases, mostly in the lower back.

This new approach to spine surgery has yet to be tested long-term, but Anderson believes it will one day show lasting benefits, mainly because it eliminates the need to destroy a portion of the large muscle group (by cutting through surrounding nerves) that is a person’s primary support when standing. Already this new approach has a significant advantage, enabling patients to return to work several weeks earlier compared with patients who undergo an open TLIF. Mark F. Abel, M.D., who specializes in pediatric orthopaedics, uses computer-generated images to help plan and execute the correction of congenital hip deformities through pelvic osteotomies. He is also using computer assistance to safely insert bone anchors into the spinal column for congenital spinal deformities. Abel notes: "This is an exciting area where techniques continue to evolve, but the techniques have already improved the safety and precision of these procedures."

IGS has been widely embraced by the European orthopaedic community, but hasn’t caught on as quickly among orthopaedic surgeons in the United States. "That is a mystery," says Kahler. "Although I think that people are still a little bit nervous about relying on a computer. But the truth is you’re doing a standard surgical procedure you’d do anyway. And you’re using the same images you would use. You’re basically just allowing the computer to help you do a better job. The computer is not doing the surgery. The computer and surgeon are working together to do a better job than either could do alone."

For more information contact:
David M. Kahler, M.D.
Ph: 434-243-0236
E-mail: dmk7y@virginia.edu