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Key omission: Coffee-based surgical stabilizing cap never tested in actual surgeries

How six cups of ground coffee can improve nose, throat surgery

Our Review Summary

This Vanderbilt University news release describes a tight-fitting silicone cap vacuum-packed with coffee grounds that tracks a patient’s head movement during surgery. With the help of a video, it does a good job of explaining how this “granular jamming cap” could improve upon currently used elastic headbands with double-stick tape, which it says are prone to slippage and don’t allow markers to cover the entire head. But costs aren’t addressed, and there are unacknowledged limitations with the research, which was published in March by the International Journal of Computer Assisted Radiology and Surgery. For one thing, the device hasn’t been tested in real surgeries. Further, researchers say coffee isn’t actually suitable for a surgical product because it biodegrades. So the headline’s assertion that “six cups of ground coffee can improve nose, throat surgery” is overblown. We also wish it had clearly explained how reducing head tracking errors could help patients.

The news release coincides with the presentation of the cap design at the International Conference on Information Processing in Computer-Assisted Interventions. It appears to be aimed at drumming up interest in order to attract an investor that could bring this product to market.


Why This Matters

Inventions are fascinating, especially if they involve familiar technologies like vacuum-packed coffee and silicone swim caps. But news releases should strive to go beyond “gee whiz” and explain how patients might benefit in terms of fewer harmful errors, quicker procedures, or lower costs. They also need to acknowledge the hurdles to widespread adoption. Science is rife with cool ideas that for one reason or another never took off. Remember inhalable insulin?

The project summarized in the release is part of the university’s technology transfer program. These projects exist to promote university-industry partnerships and often give an economic boost to businesses by commercializing products developed in a university lab. Releases on such projects must walk a fine line between serving the public’s interest (which should be their first priority) and promoting products for the marketplace.


Does the news release adequately discuss the costs of the intervention?

Not Satisfactory

There’s no discussion of how switching to the coffee-filled cap might affect costs. A silicone swim cap and six cups of coffee grounds run less than 20 bucks. But it’s safe to say this device will cost much more given the need for a potential investor to recoup the cost of clinical trials and other expenses related to getting a medical device to market. The news release suggests the cap may save time or prevent errors during surgery, which could reduce some health care costs.

Does the news release adequately quantify the benefits of the treatment/test/product/procedure?

Not Satisfactory

The news release says that researchers “designed three tests to determine how well this ‘granular jamming cap’ performed relative to the current headband in reducing targeting error:

  • They “bumped” both them from a number of different directions with a tennis ball filled with plastic particles swinging on the end of a string. They found that the cap reduced targeting errors by 83 percent.
  • They simulated the case where a cable or other piece of equipment is accidentally pushed against the two by applying forces ranging from four to six pounds in different directions. They determined that the cap outperformed the headband by 76 percent when the forces were applied to the headband and by 92 percent when they were applied to the markers.
  • They tested the effects of head repositioning by having an experienced surgeon reposition test subjects’ heads six to seven times. In this case, the cap proved to have 66 percent lower error rates than the headband.”

But the release doesn’t say how often these errors occur using the current headband method, so it’s impossible to know whether this is an improvement that would amount to a significant advance.

Also, the news release does not explain how these tests translate to something meaningful for patients, such as fewer surgical errors, shorter procedure times, greater safety, or lower costs.

It does state that in about one operation out of seven, the target error is so large that the surgeon is forced to “redo the registration process,” which orients the markers. But what that means is unclear. Does that prolong surgery to a significant extent? Does it result in greater risk or higher costs? The news release doesn’t say.

The gold standard for fiducial (or placement) markers is the use of anchors for attachment to rigid structures such as the skull. This approach is routinely used in proton beam therapy, for example, where precise location and targeting is necessary. The coffee ground cap was not tested against the anchored placement method but with what is recognized as a painless but flawed method.

Does the news release adequately explain/quantify the harms of the intervention?

Not Satisfactory

The news release mentions that the cap is “noninvasive” but doesn’t say whether there are any potential harms. Silicone allergies are purportedly rare, but they do exist.

The news release is silent on the issue of potential harm which is movement from anatomic landmarks. We aren’t sure that the lower error rate seen with the coffee cap is really an advantage.  An earlier publication from the group concluded:

Our results show that our granular jamming fixation prototype reduces registration error by 28%-68% (depending on bump direction) in comparison to a standard Brainlab reference headband.. Indeed the method appears to be better than the headband approach but it is unclear how it performs in comparison to anchored fiducial markers.

Does the news release seem to grasp the quality of the evidence?

Not Satisfactory

The news release doesn’t point out some important limitations. While the tests were intended to simulate what happens in an operating room, trials have not been performed showing that this device is safe and effective during actual surgeries. Also, the news release does not report the study’s assessment that the current design “is suitable for sinus surgery but not applicable to neurosurgeries approached via craniotomy,” a procedure in which part of the skull is removed.

The news release misses a key conclusion from the study: “Future work remains to make the granular jamming cap a robust clinical product. One objective is to replace the coffee grounds with a non-organic particle that does not biodegrade over time.” So while coffee grounds may have inspired this device, they’re unlikely to be part of a final product.


Does the news release commit disease-mongering?


No disease mongering here.

Does the news release identify funding sources & disclose conflicts of interest?


The news release says the research was supported by grants from the National Institutes of Health and the National Science Foundation. It states that one of the researchers now works for Eli Lilly and Company, and that the university is seeking a commercial partner to bring the device to market.

Does the news release compare the new approach with existing alternatives?


The news release does discuss the use of stabilizing markers and points to their downside. Unfortunately, the release ignores the potential upside of the gold standard approach, greater precision in registration and greater precision of therapy.

The news release says researchers believe the cap will “contribute to improving the guidance system’s accuracy” by increasing the number of markers used to indicate head positioning as well as improving the stability of the markers. Currently, stabilizing markers would involve “drilling and attaching the markers directly to the skull…which we don’t like to do because it is painful and it’s a step backwards from the majority of what we are doing,” said assistant professor of otolaryngology Paul Russell, who is collaborating with the engineers on the project.

Does the news release establish the availability of the treatment/test/product/procedure?


The news release does the minimum, saying “Vanderbilt University has applied for a patent on the design and the technology is available for licensing. (Interested parties should contact the Vanderbilt Center for Technology Transfer and Commercialization.)” A companion video states that “the next step is to work with a commercial partner to make it an FDA-approved product.”

Information on how long FDA approval could take, as well as a nod to the fact that this might never make it to market, would have made this better.

Does the news release establish the true novelty of the approach?


The news release states developers are presenting the “novel design and data on its effectiveness” at an upcoming scientific meeting. It also describes the cap as “an effort to improve the reliability of the sophisticated ‘GPS’ system that surgeons use for these delicate operations.”

Does the news release include unjustifiable, sensational language, including in the quotes of researchers?

Not Satisfactory

The news release maintains a restrained approach, with the exceptions of the headline and the lead. “How six cups of ground coffee can improve nose, throat surgery” is vague and misleading, since there’s no proven benefit yet. And it doesn’t strike us as accurate to describe this as “plopping six cups of coffee grounds on the heads of patients just before they are wheeled into the operating room to have nose or throat surgery.”

Total Score: 5 of 10 Satisfactory

Comments (1)

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David Salisbury

June 22, 2017 at 4:04 pm

Thank you for the review. It’s always helpful to have independent feedback.
However, I do think the reviewers were overly literal. Although the researchers intend to replace coffee grounds with plastic granules in the commercial version of the cap, the vacuum-packing qualities of ground coffee served as the inspiration for its development and all the prototypes have used ground coffee as jamming layer.
Furthermore, your reviewers seem to have totally misconstrued the purpose of the story. It was not written to try to attract a company to license the technology (although I would be happy if that occurs). It was written to illustrate the basic process of scientific/engineering innovation. In this case how engineers gain inspiration to create new and potentially beneficial new devices from unusual and unexpected sources–such as the behavior of coffee grounds when exposed to vacuum.