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05.30.18 - CALIT2-developed device aids surgical procedure

Prototype gives physicians precision-controlled assistance
for surgical procedure


In the fall of 2016, UC Irvine biomedical engineer Michael Klopfer and physicians Dr. Kam Kaler and Dr. Ralph Clayman joined forces to solve a problem that had long plagued surgeons trying to remove kidney stones. In just 18 months, the trio developed and tested a device that improves the safety of a procedure known as a ureteroscopy.

The ureteroscopy eliminates the need for an incision, because instruments are passed through the urinary tract. Sometimes, however, the procedure can result in damage to the urinary tract’s sensitive tissue. The procedure involves inserting a ureteral access sheath (UAS), which serves as a protective tube for doctors guiding instruments through the patient’s ureter, a pipeline of smooth muscle through which urine passes on its way from the kidney to the bladder. In addition to protecting the tissue, the UAS opens a clear passageway from outside the body to the kidney, allowing doctors to more easily remove the stones.

Clayman, urology professor and dean emeritus of the UCI Medical School, pioneered the development of the modern-day UAS in the late 1990s, reducing operating time and enabling more urologists to utilize the minimally invasive procedure to remove the stones. Today, there are more than 10,000 ureteroscopies performed in the United States each year, and they are on the rise due to an aging, diet-challenged population.  

“Once the sheath is in place, my mother-in-law could pass the ureteroscope into the kidney,” Clayman jokes.

The problem was that inexperienced surgeons – and sometimes even those with experience – could inadvertently split a patient’s ureter or otherwise damage the tissue by applying too much force while inserting the sheath. In fact, medical research publications concluded a couple of years ago that urologists should consider eliminating use of the UAS device because there were too many injuries.

Kaler and Clayman conceived the idea of a device that could measure the force applied by the surgeon’s hand when deploying a UAS. But first, they had to define how much force was enough to damage a ureter during the insertion process. Lab experiments determined that a surgeon applying up to eight Newtons of force was not in danger of causing damage, but any force beyond eight Newtons could tear or even split the ureter.

The physicians brought their idea of a force-measurement device to CALIT2.

Klopfer, a CALIT2 technical manager, worked with Clayman and Kaler. He and his engineering team of students originally envisioned a glove embedded with sensors that could measure force during the procedure. After observing a kidney stone surgery, however, Klopfer, no stranger to translating laboratory research into technical devices, realized that their original idea of a sensor glove would interfere with the surgeon’s workflow. He and his team worked closely with the physicians to develop a prototype that attaches directly to the UAS.

The sensor device, which they named Safe Passage, is equipped with load-cell technology – similar to the technology used in a kitchen or bathroom scale – that weighs and converts force into an electrical signal. That signal sets off an LED color-coded alert system that illuminates green, yellow, orange and eventually red. The lights correspond to progressively insistent beeping sounds that inform the surgeon whether he or she is applying safe force or entering the danger zone. The surgeon can see and hear the alarm system while guiding the UAS into place.

The load-cell sensor device connects to a smart tablet using Bluetooth technology, but can be operated independently of the tablet during surgery. “The load cell is so sensitive that it will pick up the weight of a piece of dust,” Klopfer says.

Klopfer and his engineering students developed the device in-house at CALIT2, progressing from a CAD design to software programming and finally, circuit board integration. They milled the device case from a solid block of aluminum, then assembled the device, including the load cell, power supply and circuitry.

Klopfer chose to house the load cell in a rubber boot from a motorcycle mirror to protect it during the surgical sterilization process. When asked how he came up with the idea, he professed that the junkyard is to the engineer what the art museum is to the artist. He often tells his students to walk through the junkyard to see a myriad of old and new designs.

After Klopfer and his team designed the device, Kaler took it for a sensor test drive in their lab models.  “We created a few prototypes, but the surgeons chose the simplest design; they had very few revisions because of our early meetings and observations in the operating room,” Klopfer says, adding, “As da Vinci said, ‘Simplicity is the ultimate sophistication.’”

The definitive test came when the device entered the operating room. The surgeons used it in ureteroscopies on 34 patients, reporting not even one split ureter or ureteral complication.

“We are already onto the next generation,” Clayman says. Klopfer and his team are designing a small, disposal variety of the device, which is about the size of a 35 mm film canister.  It is spring-loaded, to measure force with a mechanical scale, has chimes and includes a threshold fail-safe that disengages force above a pre-determined level.

Clayman, Kaler and the UCI Endourology laboratory team are focused on reaching their goal of using the device on 200 patients and conducting additional lab research. Their findings were recognized recently with a second-place award for best science paper at the 2017 World Congress of Endourology, held last September in Vancouver, Canada.

“We no longer have to hit our heads up against the wall when we have an idea of how to solve an operating-room problem,” Clayman says. “We have CALIT2 and Michael and his team of engineers to transform our concepts into devices and UCI’s Applied Innovation to turn our prototypes into patents.”

The next step, according to Clayman, may be licensing the technology or creating a company to make the device readily and inexpensively available. “Our mission is to develop devices and techniques to empower more urologists to do a better job for more patients.”

As for Klopfer, who takes great pride in training students to solve technical problems, urologists and patients are not the only beneficiaries. “The students involved in Safe Passage feel a great sense of accomplishment in knowing their device can help people,” he says. “Helping students grow while helping the community is what CALIT2 is all about. This is what makes me excited to come to work every day.”

— Denise Carson