Secondary Logo

Journal Logo


Editor’s Spotlight/Take 5: Does An Augmented Reality-based Portable Navigation System Improve the Accuracy of Acetabular Component Orientation During THA? A Randomized Controlled Trial

Leopold, Seth S. MD

Author Information
Clinical Orthopaedics and Related Research: May 2020 - Volume 478 - Issue 5 - p 931-934
doi: 10.1097/CORR.0000000000001216

Augmented reality (AR) technology is poised to transform the way people learn and perform orthopaedic surgery, a fact that probably generalizes across all surgical disciplines. Residents, fellows, and young attendings likely have enjoyed playing increasingly realistic games in augmented and virtual reality settings. But attendings in middle adulthood and beyond—that is, unless they have teenaged children or grandchildren—may never have strapped on a headset.

I hadn’t until this past Christmas holiday, when I visited with friends who have adolescent sons. They enjoyed watching me (a member of their parents’ generation) and the generation older than mine make ineffective movements in front of a roomful of people. Then they, and my daughters, proceeded to humiliate the oldsters with purposeful, effective feats in a variety of virtual spaces. But there’s nothing all that new there; I flew loops around my parents and grandparents with videogames when I was a kid.

What was different is that we played those games sitting down, and there was a clear separation between the characters on the screen when I played as a boy and the fully immersive experience we now can experience even with inexpensive virtual-reality gear.

Sachiyuki Tsukada MD, PhD

To put a fine point on it: at the Christmas party, we needed people to physically spot the older virtual newbies as we immersed ourselves in the AR milieu, after one of us (I’ll spare him the indignity of being named) fell over backwards during a virtual rock climbing simulation. Needless to say he wasn’t climbing anything in “real life”; he was standing on the carpet in the living room moving his arms seemingly at random until some sensation through the headset caused him to lean back and fall over like something in the old-growth forest. If you have not put on one of these headsets, there is no way to explain the experience; if you have, you don’t need the explanation.

Toys with the ability to simulate the world so effectively that they produce vestibular disorientation should offer us far more than simply the ability to giggle at our elders. They should disrupt the way we teach, learn, and practice tasks that have three-dimensional (3-D) psychomotor components.

And in some areas, they do. I spent yesterday in an immersive flight simulator learning the avionics system of an airplane I hope to fly soon. Without putting life or property at risk and without burning a gallon of gas, I practiced “buttonology” in the virtual clouds, shooting approaches and landings, while navigating in an immersive, realistic setting. Simulators like this are now available for planes that are nearly three-quarters of a century old; as I’ve said before [3], aviation hobbyists—amateurs—practice in virtual or AR settings, while surgical trainees and even surgeons practice in grandmothers’ bodies. This can’t continue.

For this reason, the article in this month’s Clinical Orthopaedics and Related Research®, “Does An Augmented Reality-based Portable Navigation System Improve the Accuracy of Acetabular Component Orientation During THA? A Randomized Controlled Trial” [6] gives me a lot of hope. This article comes from Sachiyuki Tsukada and his group in Ibaraki, Japan, and I like it for two reasons: The technology is fantastic, and it didn’t really work.

Wait, what? Didn’t work?

Nope. Turns out in this case, the surgeon was so accurate and precise without using an AR headset that although the technology helped to reduce the difference between desired and actual acetabular component alignment, the statistically apparent differences were so small as to be clinically unimportant (they were on the order of a degree or two in anteversion and cup abduction). The authors had the integrity to suggest that such small differences don’t justify the costs and potential risks of using this device, which adds surgical time and pins in the ilium. This doesn’t mean it might not help other surgeons, and there is little question in my mind that this tool would be invaluable to surgical learners.

But those are other questions for other studies to tackle. And no-difference studies are an essential part of forward progress, as are descriptive studies and studies that evaluate “difference” through different lenses altogether; we welcome them here at CORR® [4].

Still, given the rate at which we’re seeing tools like these change the world around us for the better (and safer)—in everything from aviation training, to the military, to rehabilitative medicine domains that but are a small hop away from surgical rehabilitation [1, 2]—do you doubt that virtual reality will be a larger part of our specialty in the years to come?

If you do, write a letter to the editor ( and tell me what I'm missing here. If you don’t, join me in the Take 5 interview that follows as Dr. Tsukada takes us behind the discovery, and charts a path from development to training and practice for tools of this sort.

Take 5 Interview with Sachiyuki Tsukada MD, PhD, senior author of “Does An Augmented Reality-based Portable Navigation System Improve the Accuracy of Acetabular Component Orientation During THA? A Randomized Controlled Trial” [6]

Seth S. Leopold MD:Congratulations on this fascinating and well-done randomized trial. Your paper got me thinking about the best applications for tools that deliver the kind of precision the AR unit you used are able to deliver. Your findings suggest, though, that the practices of very-experienced, precise, high-volume surgeons like you might not be the locus of greatest need. Where should we try these tools next in orthopaedic surgery (even outside of arthroplasty), and why do you think those settings are promising?

Sachiyuki Tsukada MD, PhD: Thank you, Dr. Leopold. It’s a great honor for us to report the result of our clinical trial about an AR-based navigation system for THA in CORR®. Next to THA, we have already tried to apply AR technology to navigation systems in TKA. AR technology visualizes reference lines in the surgical field during arthroplasty. For example, AR allows you to see the pelvic plane in the surgical field during THA and femoral and tibial mechanical axes in the surgical field during TKA [8]. We believe visualizing what we cannot see is useful for both high-volume and nonhigh-volume surgeons to precisely implant prostheses. In addition to visualization, AR helps surgeons spatially recognize positional information such as the depth of acetabular reaming and change in leg length.

Other than arthroplasty, AR technology goes well with arthroscopic surgeries and osteotomies. During arthroscopic anterior cruciate reconstruction, AR technology shows the entry point of tibial and femoral tunnels superimposed on the bone. During distal femur varus osteotomy, AR technology shows the bone cutting line superimposed on the femur. Adding the information of MR angiography or contrast-enhanced CT allows you to recognize the location of the popliteal artery during bone cutting.

Dr. Leopold:I have to imagine you’ve used this tool to help your residents in the laboratory learn surgical skills. What was that like and how did it compare to other tools you’ve used for that purpose?

Dr. Tsukada: Virtual reality technologies including AR technology are undoubtfully suitable to learning surgical skills. You can experience both success and failure during the surgical procedure through the use of virtual reality technologies. Compared to previous navigation systems, the AR-based system enables residents to easily recognize which factor causes error. Moreover, AR also allows the attending surgeon instructing the resident to know what is wrong. If the error results from incorrect registration of the anatomic landmarks, you can easily see the discrepancy between the bone and reference line in the surgical field. If the pelvis largely inclines, you can visually recognize the inclination in real time.

We believe virtual reality technologies have the potential to change the education of surgeons. For example, using a simulator in the virtual reality space, a surgeon in a certain country can get feedback from another surgeon in a different country in real time through the internet. Ponce and colleagues [7] have already reported the usefulness of telemonitoring during actual surgery. The mechanism is similar to that of an online game. Such potential is the most important difference from the other tools we’ve used before.

Dr. Leopold:All the same, a recentCORRarticle on using another high-tech approach to surgical education found that some very traditional approaches—including deliberate practice—were as effective in some ways as more intensive approaches, though the simulator they evaluated unquestionably made deliberate practice more effective [5]. Assuming we can develop effective virtual or AR teaching tools, what will it take to determine the best (and most efficient) ways to apply them to surgical education?

Dr. Tsukada: We read the study by Long and colleagues [5] with great interest. They used a wire navigation simulator for surgical education and compared three educational approaches with and without use of their simulator.

To apply the simulator with the use of virtual reality to surgical education, easy access to the simulator may be more important than developing new educational approaches. It is ideal that you will be able to access simulators using virtual reality as easily as reading textbooks. Using a laptop computer and a commercially available headset device, you can simulate surgery anywhere in your free time. These dreams may be realized faster than I expected due to the rapid advancements of technology.

Dr. Leopold:And related to that, I’ll adapt something I wrote [3] when we published that earlier article [5] and place it in the context of your work: even if your AR device should prove to be the most perfect AR tool humankind can devise for the insertion of acetabular cups (or for training surgeons to insert them), what about reaming glenoids? Cutting tibias during TKA (without cutting the popliteal arteries)? Placing pedicle screws? It seems impractical to develop a simulator or device for all or even many of the most-common kinds of orthopaedic procedures we perform. That being so, how do you see 21st-century surgical practice and training looking, vis-à-vis these virtual and AR tools?

Dr. Tsukada: I believe it may be practical to develop simulators for all orthopaedic procedures because the development of simulators using virtual reality is getting easier. Although simulators had been developed by commercial company corporations formerly, the current environment of technology allows you to make a simulator personally. As one example, our AR-based navigation system was developed by only one orthopaedic surgeon, Hiroyuki Ogawa MD, using commercially available computers and a 3-D printer for home use. Expanding the current simulator, we would like to develop a more patient-specific simulator in which we can perform simulated surgery for each patient and then upload the patient’s data to our laptop computer. If such a patient-specific simulator is developed, it is useful for high-volume surgeons who perform surgery of complicated cases.

Dr. Leopold:I’d like to explore your experience in the publication of what was, in essence, a no-difference trial. When we begin studies like this, we are often excited about the intervention we’re assessing, and we have high expectations for big impact. Personally, I think no-difference trials are just as exciting and important, but I also know that they can be something of a let-down. Would you share with readers how you see this, and some of the emotions you experienced with respect to this issue during the data analysis and publication process?

Dr. Tsukada: First, we would like to note that the accuracy of acetabular component placement was slightly better in the control group, manually placed by one high-volume surgeon, than previous similar studies. CT measurement showed that the difference between the targeted angle and measured angle was 3.4° ± 2.6° in inclination angle and 3.8° ± 3.0° in anteversion. To conclude the utility of our AR-based navigation, a multi-surgeon study is needed to improve the generalizability of the study design.

I believe that the no-difference trial must be valuable. Thus, I had no negative feeling when the data analysis showed a statistically significant difference but no minimally clinically important difference in this study. I also point out that the group of studies called “no-difference trials” really contains three important subgroups: (1) noninferiority trials, (2) superiority trials with no statistical difference, and (3) superiority trials with a statistical difference but an effect size smaller than the minimal clinically important difference. Our study was in this third subgroup. Such a result provides very important information to surgeons, every bit as much as a trial that demonstrates efficacy in excess of the minimum clinically important difference.


1. Alashram AR, Padua E, Hammash AK, Lombardo M, Annino G. Effectiveness of virtual reality on balance in individuals with incomplete spinal cord injury: a systematic review. J Clin Neurosci. 2020. [Published online ahead of print]. DOI: 10.1016/j.jocn.2020.01.037.
2. Karamians R., Proffitt R, Kline D, Gauthier LV. Effectiveness of virtual reality- and gaming-based interventions for upper extremity rehabilitation poststroke: a meta-analysis. Arch Phys Med Rehabil. 2019. [Published online ahead of print]. DOI: 10.1016/j.apmr.2019.10.195.
3. Leopold SS. Editor’s Spotlight/Take 5: do skills acquired from training with a wire navigation simulator transfer to a mock operating room environment? Clin Orthop Relat Res. 2019;477:2186-2188.
4. Leopold SS, Porcher R. Editorial: threshold p values in orthopaedic research—we know the problem. What is the solution? Clin Orthop Relat Res. 2018;476:1689-1691.
5. Long SA, Thomas G, Karam MD, Anderson DD. Do skills acquired from training with a wire navigation simulator transfer to a mock operating room environment? Clin Orthop Relat Res. 2019. [Published online ahead of print]. DOI: 10.1097/CORR.0000000000000799.
6. Ogawa H, Kurosaka K, Sato A, Hirasawa N, Matsubara M, Tsukada S. Does An Augmented Reality-based Portable Navigation System Improve the Accuracy of Acetabular Component Orientation During THA? A Randomized Controlled Trial Clin Orthop Related Res. 2020. [Published online ahead of print]. DOI: 10.1097/CORR.0000000000001083.
7. Ponce BA, Jennings JK, Clay TB, May MB, Huisingh C, Sheppard ED. Telemonitoring: use of augmented reality in orthopaedic education: AAOS exhibit selection. J Bone Joint Surg Am. 2014;96:e84.
8. Tsukada S, Ogawa H, Nishino M, Kurosaka K, Hirasawa N. Augmented reality-based navigation system applied to tibial bone resection in total knee arthroplasty. J Exp Orthop. 2019. [Published online ahead of print]. DOI: 10.1186/s40634-019-0212-6.
© 2020 by the Association of Bone and Joint Surgeons