Viper Prime System

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Viper Prime System

Pujan Kavakebi, Andreas Korge, Christian Mazel, Emiliano Vialle

Fig 1 The new instrument, the Viper Prime inserter, eliminates the need for Jamshidi needles, taps, and guide wires. The screw has to be loaded onto the inserter, which requires that the screw size (length and diameter) is selected based on preoperative imaging and planning.

Viper Prime is the next generation system for minimally invasive pedicle screw and rod placement from a posterior approach. It allows the surgeon to provide immobilization and stabilization of spinal segments as an adjunct to fusion in the treatment of acute and chronic instabilities or deformities of the thoracic, lumbar, and sacral spine.

The Viper Prime system introduces a novel technique for percutaneous pedicle screw placement that eliminates the need for Jamshidi needles, guide wires, and pedicle preparation instruments. Utilizing an innovative self-starting screw tip design and a stylet (guide wire) that is fully controlled by the screwdriver, surgeons can target pedicles and insert the screw with one single instrument (Fig 1).

The surgeon is therefore able to realize the benefits of minimally invasive surgery without the need for guide wire management and complex instrument systems.

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The last resort and ultimate treatment option for low back pain is fusion surgery, which is performed worldwide in more than 1 million cases per year. Acceptable clinical results are achieved in only 65% to 75% of cases, which emphasizes the need for improvement in this surgical procedure. In one of seven cases there is an approach related problem, which explains the demand for optimizing the surgical approach and technique.

Minimally invasive techniques to perform spinal stabilization have gained popularity in recent years due to the demonstration of reduced complications, less blood loss, and less perioperative muscular damage during the procedure compared to conventional open spine surgery. Additionally, minimally invasive approaches yield less postoperative pain, less narcotic usage, a shorter hospitalization, and quicker recovery than traditional open surgery.

Whilst existing minimally invasive systems (eg, Expedium Spine system, Viper 2 system) offer substantial benefits, there are still some procedure-related disadvantages. Surgeons are often required to navigate small channels involving several procedural steps, instrument passes, and management of guide wires. To streamline the surgical procedure, the Lumbar Degenerative Expert Group (LDEG), together with DePuy Synthes, have developed the new Viper Prime system as the next generation system for minimally invasive pedicle screw and rod placement from a posterior approach.

Innovative design features of Viper Prime

In the fully retracted position the stylet extends 3 mm beyond the tip of the screw, which allows proper docking to the vertebral body (Fig 2). The stylet is advanced by turning the red stylet control handle clockwise. The extension of the stylet relative to the screw tip is displayed by the red line visible through the drive tube window on the stylet depth gauge. There is also an audible click every 1 mm of extension.

Since the stylet is controlled by the inserter, this technique is safer and requires less radiation as compared to traditional techniques where Jamshidi/guide wire positions need to be established freehand and to always be checked by fluoroscopy.

Fig 2 Insertion of the pedicle screw using the Viper Prime inserter.

The surgeon uses the Viper Prime inserter for targeting, establishing the trajectory with the stylet, and advancing the screw in one single procedure (Fig 3). The stylet can be extended up to 25 mm to define the correct transpedicular corridor.

Once the stylet has been extended to establish the trajectory, the surgeon must hold the red stylet control handle while rotating the proximal modular handle (palm handle or T-handle) of the inserter clockwise to advance the screw into the pedicle over the extended stylet (Fig 4). It is critical to always hold the red stylet control while advancing the screw. Holding the red stylet control handle will retract the stylet as the screw is advanced into the pedicle. If the red stylet control handle is not held, the stylet will remain extended and advance in front of the screw, potentially leading to an anterior wall breach, neurological damage, or damage to the great vessels.

Fig 3 The Viper Prime inserter assembly is inserted through the incision (and through an optional dilator) to dock the stylet tip on the bony anatomy of the desired level. Targeting, establishing the trajectory, and advancing the screw in one single procedure is achieved without changing the instrument.

Fig 4 Insertion of the screw over the stylet.

In addition to the standard screw the Viper Prime system also offers a cortical fix fenestrated screw (Fig 5). This screw has two different thread shapes (quad lead thread and dual lead thread) designed to optimize the purchase in the pedicle as well as in the vertebral body. The fenestration allows for the option of cement delivery (with CONFIDENCE High Viscosity Spinal Cement) for augmented screw fixation in patients with poor bone quality (eg, osteoporosis).

Fig 5 The X-Tab Head and Cortical Fix Fenestrated Screw.

Viper Prime's reduced number of procedural steps and instruments improves the quality of life for the surgeon and nurses. All the instrumentation fits neatly into a 1-level case to minimize the amount of product on the back table in the OR.

The new insertion technique reduces the time to complete screw insertion compared to traditional minimally invasive techniques by about 33%. This was shown by a cadaveric evidence generation study conducted by 8 surgeons across 7 levels each (Fig 6).

Fig 6 Cumulative time (by percentage) for each step in the Jamshidi/guide wire technique compared to the Viper Prime system technique. The screw and tap steps are analogous to the screw placement step. The Jamshidi and guide wire steps are analogous to the targeting step.

The instrumentation is available to accommodate both a standard fluoroscopic MIS procedure along with a navigated inserter (Fig 7), which is compatible with the Brainlab, Stealth, and Stryker navigation systems. In the navigated version, due to safety reasons (no fluoroscopic control) the stylet only comes out by 5 mm.

Fig 7 Navigated inserter.

Case provided by Pujan Kavakebi, Innsbruck, Austria

Case: 52-year-old with low back pain

A 52-year-old male patient presented with low back pain and S1 radicular pain on the left side for 3 weeks. The laboratory tests of the blood showed enhanced inflammation signs. The MRI showed an infection of the L5/S1 disc (Fig 1). Indications for minimally invasive spondylodesis with intervertebral cage (Figs 2-6).

Fig 1 Preoperative MRI image showing an infection of the L5/S1 disc.

Fig 2 Intraoperative image of the distracting tool.

Fig 3 Navigated Viper Prime inserter.

Fig 4a-d Intraoperative screenshot of navigation in L5.

Fig 5a-d Intraoperative screenshot of navigation in S1.

Fig 6a-b The postoperative x-rays.

Overview of MIS pedicle screw insertion and Viper Prime technique

Presentation delivered by P. Kavakebi (Austria) and A. Korge (DE) in 2017.

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