All Holmium Laser Fibers are the Same, Right? Part 2: So what happened? April 06 2016

So what happened?

At the time IQinc was sold, in 2006, we had been making SureFlex™ for a decade since the original BlackHole™ single use design was released. SureFlex had gone through multiple generations of design improvements as described in four US patents, now owned by Boston Scientific. We'd demonstrated to a Lumenis VP that we could deliver 100W from their VersaPulse laser, through our true 200 micron fiber while in a less than a 10mm bend radius: we labeled that fiber, the LLF200TG flagship fiber, at 50W maximum Ho:YAG for routine use. Heck, in an attempt to blow the Lumenis executive away, our CEO wrapped the fiber around a pencil and fired the VersaPulse at full power: that SureFlex 200 survived but I definitely would not recommend this test be repeated if you like your fingers unmarred by burns. 

Sectioned SureFlex 200 circa 2006

After AMS took over, they statistically validated our maximum power rating in 2007 (or before 2009) and kept the LLF200TG at 50W. About a year after that, AMS moved SureFlex manufacturing to the Laserscope facility, in San Jose. Shortly thereafter they down-rated the fiber to 25W maximum. In 2015, the SureFlex LLF200TG fibers that we acquired for our "Fiber IQ Test" survey of the competition were rated at 12W maximum, so it seems AMS down-rated the fibers once again. Beyond SureFlex, we’ve seen no clear leader in innovation since we left the field in 2006.

Stephen’s Law of Advancing Technology: Without a leader in innovation, product designs converge.

At the time IQinc was sold in 2006, we were also making AccuFlex™ holmium fibers for Boston Scientific. AccuFlex was very similar to SureFlex, and in that AMS owned Laserscope’s GreenLight laser for BPH and Boston was the marketing arm for Lumenis’ Ho:YAG for BPH, I suspect that the AccuFlex could have begun devolution prior to SureFlex (intentional or not). Whatever the situation, Boston saw the writing on the wall and began to develop their own fiber: AccuMax™ and Flexiva™ were born a few years later.

AccuMax and Flexiva are 242μm core fibers. They are not true 200μm cores so they are more rigid than our ProFlex 200. In fact, due to thicker glass cladding, the AccuMax and Flexiva are almost exactly as rigid as a 273μm fiber. (I call 273μm core fibers that are labeled as "200 micron" fibers 'false 200s'. I suppose I have to extend this moniker to Boston's fibers, too. They are 1.2 CCDR fibers CCDR is cladding to core diameter ratio and refers to the core and fluorine-doped glass cladding that is present on ALL holmium fibers, but at differing CCDR for different sizes. To get the rigid member diameter that is directly proportional to the fiber rigidity, multiply CCDR by the actual core diameter. 273μm core fibers are 1.1 CCDR so they're 300μm glass diameter. The Boston fibers are 242μm core at 1.2 CCDR so they're 290μm glass diameter or only 3% more flexible that a ProFlex 273. ProFlex 200 is 1.2 CCDR for a 240μm glass diameter).

Prior to testing and dissecting the Boston fibers, we at IQ have heard both glowing reviews and stories of woe for these fibers. When this entry originally appeared, I'd not yet tested, or even seen Boston's fibers, but now that I have I can state that these designs are not going to be compatible with some older lasers or even new lasers undergoing broad blooming. The extent of the limitations to their performance have not yet been determined by our controlled parameter testing. 

So far, like many fibers that populate the marketplace these days, the Boston fibers appear to function perfectly well under normal conditions and in normal surgical challenges. I'd be remiss if I failed to point out a misleading marketing statement. When the Boston brochure states, "Durable design and materials can withstand a 1.0 cm bend diameter at 50W", they mean what they say but the operative word is "can"; in testing 13 of 100 fibers so tested burned through*. I'm not sure what relevance or practical value a durability of 87/100 is.... When we say ProFlex 273 withstands a 1.6 cm bend diameter at 50W we append (p<0.001), meaning less than one in one thousand will burn through. 

While no laser fiber should see a bend of 1.6 cm diameter and definitely not a 1 cm bend, holmium lasers do regularly exceed normal output conditions during surgery and such divergent performance particularly occurs during atypical surgical sessions, e.g. difficult to access calculi where small, flexible fibers are an essential element of the surgical armamentarium. In other words, the laser focus tends to bloom and drift when the rod gets hot during prolonged use, and this happens most in cases where a stone's location requires use of fibers that are the most susceptible to being damaged by laser drift; using a small core fiber in 'normal surgery' is itself a bit abnormal.

Why do I test other companies' fibers? Well, IQ's R&D VP, Dr. Jason Guth, (Ph.D.) has developed a series of functional tests for holmium lithotripsy fibers that we call the “Fiber IQ Test”. The test was originally devised to validate that our new ProFlex design had met all of the design performance criteria, as established at the onset of the project. We expanded it to include all competitors’ products that we could gather in sufficient numbers for statistical significance. As of this revision, we've tested every major manufacturer's fibers except those that are locked to a single laser console by card, RFID or some other sales barrier said to be for convenience and safety...and we plan to test those, too, as time and funds permit.

We have now put a dozen competitors through our IQ Test and just one besides our own ProFlex has passed; we plan to publish our findings in the near future, but I can tell you now that 'Stephen’s Law' has been supported, so far. Our minimum acceptance criterion for fiber raw material eliminates some competition before testing begins, because the fiber is not adequately proof-tested (100 kpsi is the industry norm) -- a production test that weeds out major flaws; we test them anyway for our edification, and yours.

The ultimate test in the IQ Test series is passing full power with the fiber in tight bending: we establish a bend diameter than is >10% smaller than the tightest turn that any fully deflected ureteroscope can make, then we pump the maximum labeled power through the fiber, and no more than one in one thousand fibers can fail. (We perform both static bend testing -- constant diameter, raising power -- and dynamic bend testing -- maximum rated power, successively smaller bending -- and apply Weibull statistics to the data to determine the probabilities of failure under various conditions.) There are other tests, too, like small fibers passing a simulated scope channel in full deflection without damaging the scope channel or the fiber, a tensile strength test for the connector (how much force is required to pull the connector off the fiber or otherwise damage it) and simulated use testing on soft and hard kidney stone phantoms (where warranted).

If you think about it, aren’t our minimum performance criteria what you would want for a fiber that is passed through your urethra, bladder, ureter and into a kidney? You don’t want little pieces of quartz glass left behind in your lower pole, do you? And you sure don’t want a fiber to burn through the side of the ureteroscope or worse, perforating your bowel or something, do you? And while you probably don’t care too much about the fiber connector blowing apart and damaging the laser -- save the potential for drape fires and even shrapnel -- such failures could force the doc to use a more invasive or less effective alternative method if the laser is damaged. (Drape fires are much more common that you might think and fires in an OR are particularly dangerous due to the presence of pure oxygen and nitrous oxide. Conjures images of Apollo 1...)

Corollary to Stephen’s Law: Dollar-driven designs approach minimum acceptable performance.

So far our tests have confirmed that all competitors' holmium fibers are indeed about the same, the key phrase being 'our competitors'; ProFlex is standing tall as the technology leader but it has only been on the market for a few months. Our prediction is that the current condition will change – that brought about according to Stephen's Law and its Corollary -- once our  products spread throughout hospitals worldwide; specifically, the range of fiber performance will begin to broaden once again as others enter a renewed technology race.

If this sounds like a preferable environment to you – having the option to choose among a cheap fiber that usually works OK but sometimes blows your laser or scope, a fiber that delivers the highest performance that your laser offer without risking your equipment and several performance grades in between – you can help bring it about  simply by trying ProFlex LLF….and then spread the word that there is something new and different for holmium laser URS.

 * "Ureteroscopy -- Indications, Instrumentation and Technique", Manoj Monga, editor, Springer Science+Business Media, New York 2013, p. 165.

Next time on “All Holmium Laser Fibers are the Same, Right?” – Part 3: ProFlex' Connector Innards are Explained

BlackHole, SureFlex and GreenLight are trademarks of American Medical Systems, AccuMax, AccuFlex and Flexiva are trademarks of Boston Scientific, VersaPulse is a trademark of Lumenis and ProFlex is a trademark of InnovaQuartz. Copyright 2016.