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Watt Happened?

January 6, 2012

Reshaped rib graftsOne day in the early 2000s, postdoctoral student Sergio Diaz-Valdes arrived at the Beckman Laser Institute, part of the University of California at Irvine, and was ready to get started. His lab chief Dr. Brian Wong had just handed him a project that, if all went well, would culminate in a significant scientific advance and maybe even a paper worthy of a high-impact journal.  

Wong wondered, in lay terms, whether cartilage reaches a Goldilocks temperature during laser surgery.  In other words, when pulsed with light energy (heat spiking in some cases as rapidly as 10 degrees C per second within its target), does cartilage reach a “just-right” temperature?  That would be a best-of-both-worlds point at which cartilage cells remain alive and fully viable but also undergo electrochemical reactions that make the tissue softer and more pliable. If so, Wong and colleagues could define the exact parameters of this just-right temperature window, maximize them to reshape the tissue with precision, and hopefully move ahead to make scalpels, incisions, and invasive plastic surgery obsolete for facial cartilage.  

Diaz-Valdes tirelessly pursued the project.  But as the weeks passed, Goldilocks was nowhere to be found.  It turns out lasers heat cartilage to a critical threshold and, once reached, denature it.  Frustrated at the negative outcome, Diaz-Valdes decided to conduct one last mock scientific experiment.  He would zap his cartilage specimen with electricity and watch it shrivel.  So Diaz-Valdes attached the cartilage to an aluminum can, inserted electrodes into the tissue, and plugged his creation into a five-watt power outlet. 

Enter serendipity.  Unbeknownst to Diaz-Valdes, the outlet was on the fritz and emitted only about 20-30 milliamps, or roughly one-fiftieth of the power produced by a standard cell phone charger.  Instead of frying the cartilage, Diaz-Valdes had turned it into an electrochemical crock pot that slow cooked the cartilage, maintaining the viability of its cells and inducing electrochemistry.  

“Sergio inadvertently turned the cartilage specimen into an electrochemical cell,” said Wong, an NIDCR grantee.  “We had oxidation reduction reactions occur at the anode and cathode [electrodes].  “In a thousand years, I would have never thought of doing this – ever.” 

The researchers named the process electromechanical reshaping (EMR), and the Wong Lab has spent several years researching its potential surgical applications to reshape cartilage. “Can you imagine sticking extremely low voltage electrodes into facial cartilage, causing electrochemical reactions, and reshaping their structure?” said Wong.  “But that’s our vision now.” 

The lab’s latest experimental foray involves the costal margin rib, the cartilage in the middle of the chest that runs along the edge of the eighth through 10th ribs.  Surgeons often use the costal rib as a source of cartilage to reconstruct badly damaged tissues of the head and neck.  The problem is crafting the rib grafts to create the precise curves and angles that match those of the original facial cartilage remains more of an art than an exact science. 

But EMR one day could make the process much less cumbersome and relatively inexpensive.  In the September issue of the journal Laryngoscope, the scientists report initial success in animals mechanically deforming and reshaping rib grafts.  The reshaping protocol worked like this: 

  • The scientists use a plastic, hand-held tool, or jig, to bend 145 rib grafts to a sharp, 90-degree curve.  The grafts were 24 by 8 millimeters with a thickness that ranged between 0.71 and 0.08 millimeters.
  • They insert platinum needle electrodes into the cartilage through pre-drilled holes in the jig.  The electrode leads were connected to a direct power supply to provide low-level voltage for minute increments, from one to five.
  • The researchers then place the grafts into a rehydrating phosphate buffer solution for 15 minutes.  Previous work has established that EMR neither denatures protein nor causes cell death in the cartilage, leaving the tissue healthy and functional.

In this study, the researchers worked out the optimal time and voltage to reshape the grafts. They found, as a rule of thumb, that increased voltage and application time led to the most effective reshaping.  They detected the onset of reshaping at three volts and signs of saturation at five volts.  At seven volts, resistive heating becomes detectable, bringing the increased likelihood of tissue warping and damage.  The optimal time of EMR was five minutes.  The authors concluded, “EMR provides a novel method to bend and shape costal cartilage grafts for use in facial plastic surgery . . . Animal studies are needed to examine the long-term healing response of treated cartilage and are warranted before clinical trials.”

 

  • Manuel CT, Foulad A, Protsenko DE, Hamamoto A, Wong BJ, Electromechanical reshaping of costal cartilage grafts:  a new surgical treatment modality,” Laryngoscope 2011 Sept;121(9):1839-42.

 

 

 

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This page last updated: February 26, 2014