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| Dr. Paul Fedak |
October 26, 2010 (Montreal, Quebec City) — Superman avoided kryptonite, one of the few things that could bring him down, but cardiac surgeons might one day willingly embrace another form ofKryptonite (Doctors Research Group, Southbury, CT), used to seal the sternums of patients who go under the surgeon's saw.
Kryptonite, a bone cement that bonds the breastbone after CABG surgery, improves patient quality-of-life scores and spirometry measurements, reduces pain and physical disability, and cuts the amount of pain medication needed after surgery, according to results of the Sternal Innovative Closure with Kryptonite (STICK) study.
Led by Dr Paul Fedak (University of Calgary, AB) and presented this week here at the Canadian Cardiovascular Congress 2010, the study showed that when used in addition to traditional wires that close the chest, the bone cement completely seals the breastbone within 24 hours and is designed to be integrated with native bone as the body heals.
"A lot of medicine is moving away from invasive surgeries to procedures that can be done less invasively," said Fedak. "But patients often stay away from invasive procedures to their own detriment. There is a lot that we can do with an open chest cavity. And with open-heart surgery, it's usually not the heart the patient worries about, but rather the long, painful recovery associated with cutting open the sternum."
Tested in 55 Stable CABG Patients
Bone cement commonly used by orthopedic surgeons is known as polymethylmethacrylate (PMMA), but it is a "toxic, synthetic product" that doesn't fully heal, explained Fedak. The Kryptonite bone cement, on the other hand, is a biocompatible polymer made of triglycerides, extracted from the castor bean plant, and calcium chloride. The product exists in a liquid form but changes within minutes to moldable putty, eventually hardening into a light, porous, and strong bonelike substance within 24 hours.
"What's also very cool about it is that it creates a regenerative scaffold where native bone cells can enter into it and lay down new bone," said Fedak. "It actually heals and allows for osteointegration. Those properties, and the fact that it bonds very specifically to bone and not other tissues, like the heart, lungs, or other soft tissues, make it ideal for cardiac surgery. Adhesives haven't been used like this before. People have used all kinds of things to promote healing of the chest bone, but nothing that will turn it into a rock-solid stable sternum within 24 hours."
Last year, Fedak and colleagues tested the strength of the cement in cadavers, showing that it was able to withstand increasing forces designed to simulate coughing and flexion of the torso. In this latest single-center study, the group tested the use of Kryptonite in 55 stable patients undergoing CABG surgery. As noted, patients reported less pain, required fewer narcotics for pain management, and had improved spirometry measurements. In addition, two functional scales--health-related quality of life and physical disability--were also improved in patients treated with the bone cement compared with controls.
"After surgery, traditionally, patients have some degree of physical disability and dysfunction, and then over weeks they recover and get back to normal. In cardiac surgery, that normally takes about six to eight weeks. With Kryptonite, we're seeing it around four or five weeks. Patients had less pain, better breathing, and recovery time reduced by a couple of weeks."
There were no reported side effects or adverse outcomes, but surgeons need to be mindful of the chest tubes running underneath the breastplate as the sternum is closed so that these do not adhere to the glue. Currently, the glue has been tested only in stable patients, and investigators are cautious about using the cement in unstable patients or those at high risk for postoperative bleeding, mainly because it requires more time to reenter the chest cavity if needed.
To heartwire , Fedak said that cardiac surgery has evolved significantly over the past 50 years, with much research into minimally invasive procedures, on- and off-pump CABG surgery, and even robotics. One thing that hasn't changed during this period of innovation, he said, is how surgeons close the sternum, noting that wire cerclage closure of sternotomy is used just as it was when the procedure was first performed.
"The wires themselves are not a problem," he said. "It's just that we're asking them to do too much over too long a period of time. With the cement, we're using the wires for what they're good at, which is bringing the edges of the bone together, but they're not good at keeping that bone together over a long period of time. Now, with the cement, we're only asking the wires to work for the first day."
