|James Bono, MD|
Hospitals across the United States are exchanging their old image-storage libraries for picture archiving and communications systems (PACS) because of the time and effort it saves in acquiring, storing, and retrieving information that was once saved on film. Until recently, however, one problem remained that often took radiologists back into the dark ages of film. The problem was this: How can an orthopedist use PACS to perform preoperative planning?
Orthopedists constitute one of the largest customer groups of hospital radiology departments because of the planning that is needed to perform hip replacement or reconstructive surgery on a knee. They use hard-copy radiographs in planning for the replacement of a damaged joint, for example, by placing an acetate prosthesis template over the problem area on the image and measuring to determine the proper fit. These templates are provided by prosthesis manufacturers in various sizes.? Though many hospitals have PACS to store images from many modalities, they may still print film for orthopedic surgeons to use in their planning.
“In a filmless environment, how could an orthopedist plan for surgery?” Lenny Reznik, Agfa’s representative for orthopedic products, asks. “When a site went to PACS, that created a problem for orthopedists because there was no film to use for their surgical planning. Printing film for orthopedists prevents the hospital from gaining the full benefit of its investment in PACS.”
Weaning Orthopedists from Film
In response to this problem, Agfa, working in conjunction with physicians from New England Baptist Hospital, Boston, designed the IMPAX OT3000 for Orthopedics system. The system is the same as a radiology PACS, but it also has special software that has been added to aid physicians in planning for surgery. The tools that the system employs allow the surgeon to overcome the problem of the template overlays and improve on some other areas of planning. “We worked with leading orthopedic prosthesis device manufacturers and we were able to license digital copies of their templates,” Reznik says.
|Steven Wetzner, MD, (left) and Ron Williams, PACS Administrator|
Agfa then created a library of these digital templates so that surgeons could sit at a workstation and choose templates of different sizes and shapes and overlay them digitally on the displayed image. The surgeon can size an implant at the workstation and? be reasonably sure that the calculations are correct. Digital images allow the use of the radiographic image and the template in a more efficient manner.
James Bono, MD, an orthopedic surgeon at New England Baptist Hospital and associate professor at Tufts University School of Medicine, Boston, was one of the design consultants on the project and thinks that it is a dream machine. “I think it’s the greatest thing since sliced bread,” he says. “The efficiency of surgical planning is a now at a new height. Remember, the accuracy of planning is only as good as the accuracy of surgical techniques. If your measurements are to the millimeter, but your technique is only accurate to within 10 mm, then such a precise planning tool is not necessary, but if technique is precise, then the tool must also be precise.”
Bono, along with Steven Wetzner, MD, chair of radiology at New England Baptist Hospital and professor at Tufts University, helped come up with the parameters of the system. “My part was to identify problems with the current way of doing things,” Bono says, “and then create the tools that allow determination of magnification and determination of bone diameter (to select the size of the implant), along with developing a tool that determines any leg-length discrepancy.”
Importing the templates
Bono also helped to evaluate the tools that allow the importation of digital templates that replicate the templating process that had been done manually. He uses the analogy of an architect using a blueprint to explain what happened during a hip replacement before the introduction of the IMPAX 0T3000. “If you had an architect make up a blueprint, and the scale of the drawing was, perhaps, 5% off, and you gave those plans to the builder, the builder would then build the house with blueprints that were out of scale with the rulers and measuring tools used to cut the materials. Nothing would fit,” he says. “That is what we have been doing in hip surgery, up to this point. The preoperative planning measurement tools have been out of scale with the actual tools and instruments that are used during surgery. That can sometimes lead to variation in implant size and leg length.”
The other problem with presurgical planning on film, Bono explains, is the magnification of images. On film, the image is magnified in large patients who have more soft tissue and undermagnified in thinner patients. The surgeon must then calibrate what the percentage of magnification is and make corrections before the surgical procedure. If there is significant magnification, this can lead to surgical error and inefficiency. Using a marker of known size-such as an osteonic marker or a coin-taped to the side of the bone during imaging, the surgeon calculates the percentage of magnification and adjusts accordingly. This is done by calculating the difference between the marker on the film and the known size marker.
“A patient having a radiograph taken typically lies down on the table. The beam is placed over the body part and stays at a fixed height over the table,” Bono says. “Consequently, large patients’ bones are closer to the beam and thin patients’ bones are farther away from it.” The closer the bone is to the x-ray beam, the larger the shadow that is cast on the film. A heavier patient and a smaller patient can have the same size bone, but they will appear to be of different sizes on the radiograph.
“That is not a problem unless you are trying to fit a prosthesis into the bone, in which case your measurements will be thrown off by the errors in magnification,” Bono says. “For example, the heavier patient’s bone will appear bigger, leading the surgeon to believe that a larger prosthesis is necessary when a smaller one would be a better fit.” Conversely, the smaller patient’s radiograph, in which the bones appear smaller than they actually are, can lead to the placement of an undersized prosthesis, which could loosen prematurely. Add to this the problem of differing levels of magnification between the radiograph and the acetate template used to fit the prosthesis and it is easy to see why surgeons encounter problems in ensuring that patients get implants of the right size.
Correcting Film Shortcomings
In hip-replacement, historically, there has been a discrepancy between the magnification of the radiograph and that of the template, Bono explains. The orthopedist has needed to rectify the difference between the two. That can be done by adjusting the magnification of the radiograph to match that of the template or vice versa (or devising a conversion table).
“The workstation allows us to determine the magnification of the radiograph and then import the templates digitally, to scale,” Bono says. “The accuracy that I have now has never before been possible to achieve.”
IMPAX for Orthopedics helps the surgeon deal with nearly all problems at the click of a mouse The system allows the physician to adjust contrast levels for overexposed or underexposed images and adjust the magnification of the image to fit the magnification of the acetate template.
“The surgeon can now take all the measurements necessary for templating and not only speed up the process, but also use the system’s potential for templating accuracy,” Reznik says. “We believe that we have developed something that gives the orthopedist more powerful tools to do presurgical planning.”
The software provides the surgeon with on-screen tools for calibration and the placing of templates. Then, the surgeon can save the templated image for further use in Joint Photographic Experts Group (JPEG) format. The result is improved tools for preoperative and postoperative management, notes Bono, as well as better preoperative and postoperative patient care. “Surgical planning is now at a new height,” Bono says. “I feel that surgical outcome is improved, and by that I mean selection of the proper size implant and more accurate placement of the implant to restore leg-length equality.”
The other advantages that the system has over film are that it allows patients to be educated more efficiently and gives orthopedists the ability to follow their patients’ progress. “Patients need to be educated,” Bono says, “and a digital format, with pointers and zoom features, allows better understanding of the abnormalities on the image. This, in turn, explain the patient’s disease more clearly.”
Follow up care is eased
The other benefit is that postoperative follow-up care now becomes as easy as searching for the original image and comparing it to a current image in order to detect any problems that may be developing. “The ability to follow patients over time allows closer scrutiny and measurement of implants to detect loosening or wear of the prosthesis,” Bono says.
Bono says that other surgeons have reacted to the system with astonishment. “People’s jaws drop when they see this,” he says, “particularly if they are younger surgeons who see the benefit in terms of…efficiency.”
Beyond the accuracy of measurements and the ability to improve patient care, the station also brings New England Baptist Hospital closer to its goal of becoming a filmless hospital, and it has improved work flow and economic efficiency, Wetzner says. The eventual goal is to allow all physicians to access the information from their offices and view it on their own web browsers. “I believe that it does improve the quality of preoperative planning that the orthopedist provides for the patient,” Wetzner adds,? “and it allows them to be more precise in their measurements.”
He continues, “We have been involved in PACS for 6 years and we are creating a completely digital department, from immediate image review to Internet access from physicians’ homes and offices. This allows us to be complete in our mission to be filmless, and it stops us from having film images that we do not want to refile.”
Ron Williams, PACS administrator at New England Baptist Hospital, says, “Without a doubt, our work flow has improved. Our film budget has dropped by 80%, and most of our printing is done for patients who take film to other facilities that are not PACS equipped.” He notes, “Hospitals are required by law to keep images on file for 7 years. We don’t destroy any images because we do chiefly orthopedics. When we went to PACS, most of our images were stored digitally.”
Williams says that his job is to bring physicians into the PACS era. The training that is needed to use the new system is not difficult or time-consuming. Surgeons are given some basic training to familiarize them with using different tools; they then are allowed to explore how the system works on their own. Williams reports that surgeons find it easy to embrace this new technology.
Bono, whose specialty is hip and knee replacement, says that the system that is now in place is specifically for hip-replacement surgery, but there are other components in the works. “Agfa is moving on to the development of a knee workstation that would do many of the same things that the hip workstation does,” he says, “but that would, in addition, allow us to plan the correction of angular deformity.” Angular deformity is corrected through osteotomy (removing part of the bone to allow the leg to heal straight).
Agfa also plans to include voice-recognition software in the system and to increase the efficiency of record keeping by integrating radiology images and medical records.
Bruce Bean is a contributing writer for Decisions in Axis Imaging News.