The Turning of the Screw

The quest for the best operative techniques and technologies in pedicle screw placement has taken a significant step forward with the introduction of a smart freehand drill that has made a remarkable contribution in the field of spine surgery.

PediGuard™, an FDA-cleared Class II medical device manufactured by SpineVision, is making auspicious inroads into the U.S. market after an encouraging debut in Europe. It is the only device of its kind for real-time detection of possible breach of the vertebral cortex during pedicle screw site preparation.

The device is another tool to cover the surgeon’s back. It features both visual and audio alerts during pedicle screw pilot-hole drilling. For the surgeon in the trenches navigating the pedicles, these rich cues are an indication of a change in electrical conductivity at the tip of the device helping him to analyze the type of tissue in contact with the tip. The PediGuard™ device can reduce the need for intra-operating imaging, and may also decrease the average screw placement time. This can result in a significant reduction of the average radiation exposure, a welcome benefit for surgeons concerned about cumulative lifetime radiation exposure, especially as “acceptable” levels of radiation exposure are continually being revised downward.

Pesky Pedicle Screw

Here is where the wheat is separated from the chaff: effective pedicle screw placement demands surgical perfection. Unfortunately, the current success rate does not approach 100 percent, even when using computer-assisted surgery (CAS) protocol. Depending on the method used to determine perforation and on the type of cases studied, published rates of pedicle perforation range from 10-40 percent ^1-3. But it’s the “bread and butter work,” as former SRS president Courtney W. Brown, MD calls it, of spine surgeons everywhere and any tool that enhances the success of those procedures is a welcome asset.

Fluoroscopy has become one of the most frequently performed procedures in the O-R today for pedicle screw placement. But the perforation rate continues to be a significant problem and with an average drilling of four-to-six holes in a degenerative spine and 26 holes in scoliosis cases, that’s a lot of opportunity for the procedure to go awry.

The percutaneous procedure used in minimally invasive surgeries makes it particularly challenging to correctly place screws as the anatomical landmarks are not visible. It has the added disadvantage of increasing the use of X-Rays, at a time when more and more voices can be heard on the dangers of radiation exposure during spine surgery to the patient, the surgeon and the OR staff.

A Two-Fold Advantage

Surgeons across the country are breathing a collective sigh of relief as the much-anticipated preliminary data from an ongoing post-market multi-site, randomized study led in the USA by Randal (“Randy”) Betz, MD, an orthopaedic spine surgeon and Chief of Staff at Shriners Hospitals for Children, Philadelphia, (ClinicalTrials.gov identifier: NCT00549627) have now been released ⁴.

They show that the use of the FDA-cleared PediGuard™ medical device results in a significant two-fold reduction in breaches for patients having had surgery for degenerative conditions with titanium screws between T12 and S1, and a six-fold reduction in medial breaches as compared to the traditional freehand technique. So far, the results also suggest an approximate 10% decrease in average screw-placement time, and an impressive 25-30% reduction of the average number of fluoro shots. Additional data for the more challenging thoracic and spinal deformity cases are expected later this year.

European data has already found a strong clinical trend that using PediGuard™ makes spine surgery safer⁵. Dr Brown says that he’s currently looking forward to reading the final results of the American study with regards to further potential benefits on the PediGuard™ device.

The younger surgeons are eagerly embracing the new technology.
“I started using PediGuard in January 2007 because of its accuracy first and secondarily, because of the safety issues,” says Milan W. Mody, MD, an orthopedic surgeon and assistant professor at the Willis-Knighton Health System & LSU Health Sciences Center. “If I had to rank my reasons for using PediGuard, I would say I use it 51% for the sake of accuracy and 49% for the radiation safety.” Dr. Mody’s bio states that he is “one of the few spine surgeons in the country to have received advanced surgical training from both neurosurgeons and orthopedic spine surgeons.”

“Less use of fluoroscopy per case means significantly less accumulated radiation exposure,” said Randal R. Betz. “With PediGuard, you’re cutting down on radiation—and that’s huge.” “Using PediGuard, I have a 90% chance of placing all my pedicle screws properly, compared to an 80% or less chance using standard manual technique,” adds Randal R. Betz “Given the solid published clinical data from Europe in combination with our preliminary data, this is a very significant clinical trend toward making spine surgery even safer for patients. If the trend continues, I see no reason why PediGuard can’t become standard of care for spine surgery. Anything we can do to help us get a safer screw insertion is certainly worthwhile, given that published rates of pedicle screw misplacements can range as high as 40%.”

For the spine specialist, there is an initial steep learning curve in the highly specialized technique for placing pedicle screws; however, the learning curve for the PediGuard™ device is not considered steep. Surgeons possess appropriate technological backgrounds and are generally known for being savvy when it comes to new technologies, but also the use of PediGuard™ has the unique advantage that it requires no change in surgical technique or procedures. Surgeons are taught how to interpret the alert signals of the user-friendly device at a workshop before they use it in the OR. Practice. Practice. Practice. And away you go. “I used it three or four times at a workshop to really feel it,” says Dr. Brown.