SmartScrew technology reduces radiation exposure and OR time in MIS lumbar surgery

Megan Wood -   Print  |

Spine surgery is among the costliest procedures in healthcare today, and providers across the country are examining evidence-based practices to achieve high-quality outcomes while lowering the economic burden.

This content is sponsored by SpineGuard.


Spine fusion cases often require pedicle screw placement, in which the surgeon uses a four-step process: access the pedicle using a drill or awl; create a reproducible trajectory using a probe; tap the pedicle to help guide the screw in the bone; and then place the pedicle screws. This multi-step, multi-instrument process takes time, and each step frequently uses significant amounts of X-ray fluoroscopy to validate placement of each instrument to confirm optimal trajectory for final screw placement. However, surgeons are turning to minimally invasive procedures to achieve better results, creating a need for medical device innovation.


The minimally invasive advantage
Every minute a patient spends in the operating room increases the risk of infection and adds cost to spine fusion procedures. When surgeons perform MIS fusion procedures and reduce procedure time, they're able to consistently achieve better clinical outcomes and drive cost savings for the hospital. A 2016 study published in Spine assessed the quality and economic impact of minimally invasive versus open transforaminal lumbar interbody fusion and posterior lumbar interbody fusion. Compared to the open group, patients in the MIS group reported less blood loss and shorter lengths of stay. Additionally, researchers found the MIS group saw comparative cost savings from 2.5 percent to 29.3


Technavio analysts predict the global MIS spine market will grow at a compound annual rate of 7-plus percent through 2020. In the U.S. specifically, the report notes an increase in lumbar spine fusion cases through 2020.


The MIS technique presents some major drawbacks, however: Spine surgeons greatly depend on X-ray fluoroscopy and other intraoperative radiographic technologies during minimally invasive spine fusion procedures, which can result in increased surgical time and increased radiation exposure for the patient, OR staff and the surgeon.


"In an attempt to reduce the invasiveness of surgery, we have to rely on X-ray guidance in order to perform the operation through very small incisions," says Farhan Siddiqi, MD, assistant professor at Tampa-based University of South Florida and a surgeon at Tampa-based Florida Advanced Spine, Sports and Trauma Centers and Odessa, Fla.-based Trinity Spine Center.


A 2016 study published in Clinical Spine Surgery examined the radiation-related risks of minimally invasive transforaminal lumbar interbody fusion compared to open surgery. The 619-patient study found the minimally invasive TLIF patients experienced a 2.4-
fold increase in radiation exposure rate compared to open patients.


Enter the Zavation Z-Direct Pedicle Screw System featuring SpineGuard's Dynamic Surgical Guidance Technology (DSG™). The hybrid technology is the result of a 2015 co-development partnership between the companies. SpineGuard and Zavation worked together to develop a "SmartScrew" designed to streamline surgical steps while maintaining the accuracy for pedicle screw placement. Additionally, it's showing promise to reduce the use of intraoperative imaging in standard and MIS procedures. In October 2017, the two companies commercially released the screw system in the U.S. during the North American Spine Society annual meeting in Orlando, Fla.


Why smart screws are the smart choice
SpineGuard's DSG Technology differentiates various tissue types based on an analysis of the local electrical conductivity (cancellous bone, cortical bone, blood and soft tissues). Real-time feedback informs the surgeon of changes in tissue type by changes in the pitch and cadence of an audio signal and a flashing LED light. This in turn alerts the surgeon of potential pedicular or vertebral breaches during pedicle screw placement.


The DSG enabled Z-Direct Pedicle Screw System incorporates a single-use SpineGuard DSG pin embedded with a bipolar sensor that is inserted into the cannula of the Zavation Screwdriver/Pedicle Screw and connected to the electronic processor inside the single-use SpineGuard DSG handle. The combination of the Z-Direct Pedicle Screw System and DSG Technology creates a "smart screw," effectively reducing the steps of pedicle preparation before screw insertion.


Here's how it works:


  • The distal awl-like tip of the DSG pin facilitates entry into the pedicle and the bipolar sensor continuously checks for the proximity of the cortical walls of the pedicle, alerting the surgeon of the potential for cortical breach.
  • The design of the Z-Direct screw tip allows for quick purchase of the screw into the pedicle and redirection during insertion until the screw is past the pedicle isthmus.


"Rather than using fluoroscopy or image guidance, which have inherent errors associated with them, DSG guidance provides the surgeon feedback 'at-the-tip' of the screw to allow for moment-to-moment prediction of a potential breach, as well as the ability to adjust and redirect the screw at the optimal corridor of bone," says Larry Khoo, MD, of The Spine Clinic of Los Angeles.


Additionally, surgeons often use a K-wire for guidance during MIS procedures, a multi-step process to guide instruments and implants into and through the pedicle. DSG Technology can eliminate K-wires, meaning surgeons need to take just one step for pedicle screw insertion.


"Embedding DSG technology into a Zavation pedicle screw is novel and potentially game changing for surgeons performing minimally invasive spine fixation procedures. By combining these previously separate technologies, surgeons who wish to use a single-step pedicle screw insertion technique will have real-time navigation feedback, while eliminating multiple steps in the placement of these screws into the spine," says John Williams, MD, of SpineONE, a division of Ortho NorthEast in Fort Wayne, Ind.


Dr. Khoo adds, "Rather than Jamshidi needles, K-wires, awls, taps — all of which require more time, risk and radiation exposure to perform MIS spine fusion procedures — DSG smart screw placement can be achieved in a single step without sacrifice in accuracy. The attendant gains in safety and bone purchase of the screw make the combination of these technologies even more attractive."


The initial clinical results are in
Drs. Khoo, Williams and Siddiqi are participating in a clinical study investigating how to reduce radiation and operative time per screw level during minimally invasive lumbar spine surgery. The study involves a prospective registry of cases leveraging DSG smart screw instrumentation.


The researchers are examining the time of cannulation, radiation exposure, outcomes, complications and radiographic screw placement accuracy. The team is equipped with data from previously published studies on pedicle screw instrumentation placed with an open or MIS standard freehand technique. Dr. Khoo notes they will compare their findings with the data from these previous studies.


"Although early, this DSG single-step screw placement technique appears to have savings in surgical time, radiation exposure and trajectory readjustments as compared to traditional MIS screw cannulation," Dr. Khoo says.


Dr. Williams agrees, "Initial study results evaluating the benefit of combining DSG technology and pedicle screws show a reduction in both intraoperative radiation exposure as well as reduction in the time required to safely place a pedicle screw in the spine."


The DSG enabled Zavation Z-Direct Pedicle Screw System can reduce the need for X-ray fluoroscopy lowering the risk of radiation exposure to the patient, OR staff and the surgeon. It also allows for ideal screw placement and enhanced bone purchase to optimize pedicle screw constructs. Combined with the potential to reduce the overall surgical process, hospitals have a unique opportunity to decrease costs for spine fusion procedures.


"As familiarity and facility with the DSG-guided singlestep screw placement technique grows, there will be resultant savings in radiation exposure, surgical time and bone purchase quality," adds Dr. Khoo. "I would anticipate a significant financial cost savings as the DSG smart screws are used more widely over time in any given surgical institution."


More articles on MIS:
Titan Medical receives new patent for robotic surgery: 3 things to know
The evolution of endoscopic spine surgery — Key thoughts from Dr. Anthony Yeung
Dr. Nitin Kukkar brings spine surgery to Hopedale Medical Complex: 4 highlights

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