Minimally Invasive, Stereotactic, Wireless, Percutaneous Pedicle Screw Placement in the Lumbar Spine: Accuracy Rates with 204 Consecutive Screws

Presented at SMISS Annual Forum 2014
By Blake Staub MD
With Paul Holman MD, Virendra Desai MD,

Disclosures: Blake Staub MD None Paul Holman MD B; Biomet Spine, Medtronic Spine Navigation. F; Biomet Spine, Medtronic Spine, Virendra Desai MD None,

Introduction:
Standard fluoroscopic and stereotactic CT-guided lumbar pedicle screw instrumentation has traditionally relied on the placement of Kirshner wires (K-wires) to ensure accurate screw placement. The use of K-wires, however, is associated with a known risk of morbidity due to inadvertent bending or ventral displacement into the retroperitoneum. We report our experience using a computer, image-guided, wireless method for pedicle screw placement.

Aims/Objectives:
To determine the accuracy and safety of lumbar pedicle screw instrumentation without the use of K-wires. We hypothesize that minimally invasive, wireless pedicle screw placement is as accurate and safe as the traditional technique utilizing K-wires, while decreasing operative time and inherently avoiding the potential morbidity associated with K-wires.

Methods:
A retrospective review was undertaken of the first 43 consecutive, stereotactically-guided, wireless lumbar arthrodesis cases. All the constructs were supplemented by either ALIFs, TLIFs, or XLIFs. The cases were performed using the O-arm (Medtronic, Sofamor-Danek, Memphis, TN) and Medtronic stereotactic instrumentation. After placing a percutaneous, navigation frame into the ilium, pilot holes were drilled with an extra long match stick burr within a navigated universal drill guide. The trajectory plan was then saved on the Medtronic Stealth Station prior to removal of the drill bit. Rather than inserting a K-wire at this point, the drill and drill guide were removed. Using the saved plan, the pilot hole is easily palpated and subsequently tapped with an image guided awl tip tap. The screws were then inserted using a navigated screw driver and the saved trajectory plan as a tactile and visual guide. An O-arm scan was then done to confirm screw placement.

Results:
There were 24 females and 19 males with an average age of 56. 204 pedicle screws were placed using the stereotactic, wireless technique. Only 2 screws were inaccurately placed and required repositioning. The overall accuracy was 99.2%. The two misplaced screws occurred in the same patient, were equally low, and were replaced with no increased patient morbidity.

Conclusions:
Wireless, percutaneous placement of lumbar pedicle screws utilizing CT-guided stereotactic navigation appears safe with extremely high accuracy rates of greater than 99%.