The Debate Over Computer-Assisted Tools in Total Hip Arthroplasty

    All orthopaedic surgeons have the same treatment goals for their patients who need total hip arthroplasty (THA):

    • Alleviate pain and improve function
    • Minimize complications, such as dislocation and wear
    • Perform the procedure in manner that is reliable, reproducible, and efficient

    How they achieve these goals is a matter of debate: Should surgeons routinely use high-tech instrumentation, such as computers and robots, to improve acetabular cup positioning? Or is the less time-consuming, less expensive, low tech option of manually positioning the cup the better choice?

    Lawrence D. Dorr, MD, Medical Director of the Dorr Arthritis Institute, Centinela Hospital Medical Center, in Inglewood, California, and Mark W. Pagnano, MD, Professor of Orthopedics at Mayo Clinic, Rochester, Minnesota, presented their differing views at the recent ICJR West meeting in Napa, California.

    PRO: Lawrence Dorr, MD

    Dr. Dorr’s experience with computer navigation to assist in positioning the acetabular cup began as a research project. He liked the precision that navigation provided, and since then, he has used either a computer or a robot for all his THA cases.

    He contends that surgeons have difficulty with cup positioning when they do not use a computer because during surgery, all they see is the acetabulum; they cannot see the relationship of the acetabulum to the pelvis and the pelvis to the body. On the operating table, the pelvis is tilted to the longitudinal axis, which affects its relationship to the acetabulum.

    Dr. Dorr’s research has shown that:

    • About 16% of patients have a tilt that is greater than 10º, which has an effect on cup positioning
    • The acetabulum has an average inclination of 55º and an average anteversion of 12º, which affects the surgeon’s ability to balance coverage of the natural angle of the acetabulum with the 45° of inclination he or she is trying to achieve.

    Dr. Dorr shared data from his own research of manual vs. computer-navigated cup positioning. When manually estimating cup position, 10% of the cups he placed were 10º off, and 25% are 5° to 10º off. When using computer navigation to determine cup position, he was within 5% of precision in all cases.

    Dr. Dorr said that despite the advances made in techniques to cover technical errors, such as anterior incisions, large heads, mobile cups, and operation room imaging, THA revisions continue to increase. He concluded that when all else fails, surgeons should consider improving their technique using high-tech instrumentation, such as computer and robotic navigation, that has shown 90% to 95% precision.

    Con: Mark W. Pagnano, MD

    Dr. Pagnano disagrees. He contends that computer navigation remains without proven clinical benefit. That would be acceptable if computer navigation was new, he said, but it is in its second decade and should be showing clear patient benefits by now – in other words, improved clinical outcomes, such as lower dislocation rate, greater range of motion, and improved durability and functioning.

    A meta-analysis of three randomized controlled trials of 250 patients, in fact, showed that placement of the acetabular cup within a defined alignment did not clearly translate into better clinical outcomes, Dr. Pagnano said.

    Although computer navigation allows the surgeon to hit a specific target compared with manual instruments, Dr. Pagnano noted a number of problems with the technology:

    • There is considerable confusion in describing the inclination and anteversion targets for THA.
    • The right target for individual patients is unknown.
    • Factors other than component orientation may be more important in dislocation and durability.

    Research has failed to sort out these issues, Dr. Pagnano said. In fact, studies with computer navigation contribute to the confusion by using different definitions of the targets in different planes (saggital, coronal, transverse) and even use different targets within the same study.

    Computer navigation remains a cumbersome, time-consuming, and expensive too without clinical benefit, Dr. Pagnano said. However, it is a good research tool that can be used to capture data that may eventually be used to help improve navigation.

    The future, Dr. Pagnano said, may include a return to image-based systems due to marked advances in 3-D imaging that eliminate errors inherent in surgeon entry of data.

    For now, the power of the computer likely lies outside the operating room for the typical THA surgeon, Dr. Pagnano said.

    Watch the presentations by Dr. Dorr and Dr. Pagnano by clicking thebuttons below