Percutaneous “K-wireless” pedicle screw fixation technique

An evaluation of the initial experience of 100 screws with assessment of accuracy, radiation exposure, and procedure time

Steven M. Spitz, MD , Faheem A. Sandhu, MD , PhD, and Jean-Marc Voyadzis, MD

Object: Percutaneous pedicle screws are used to provide rigid internal fixation in minimally invasive spinal procedures and generally require the use of Kirchner wires (or K-wires) as a guide for screw insertion. K-wires can bend, break, advance, or pull out during the steps of pedicle preparation and screw insertion. This can lead to increased fluoroscopic and surgical times and potentially cause neurological, vascular, or visceral injury. The authors present their experience with a novel “K-wireless” percutaneous pedicle screw system that eliminates the inherent risks of K-wire use.

Methods: A total of 100 screws were placed in 28 patients using the K-wireless percutaneous screw system. Postoperative dedicated spinal CT scans were performed in 25 patients to assess the accuracy of screw placement. Screw placement was graded A through D by 2 independent radiologists: A = within pedicle, B = breach < 2 mm, C = breach of 2–4 mm, and D = breach > 4 mm. Screw insertion and fluoroscopy times were also recorded in each case. Clinical complications associated with screw insertion were documented.

Results: A total of 100 K-wireless percutaneous pedicle screws were placed into the lumbosacral spine in 28 patients. Postoperative CT was performed in 25 patients, thus the placement of only 90 screws was assessed. Eighty-seven screws were placed within the pedicle confines (Grade A), and 3 violated the pedicle (2 Grade B [1 lateral, 1 medial] and 1 Grade D [medial]) for an overall accuracy rate of 96.7%. One patient required reoperation for screw repositioning due to a postoperative L-5 radiculopathy secondary to a Grade D medial breach at L-5. This patient experienced improvement of the radiculopathy after reoperation. Average screw insertion and fluoroscopy times were 6.92 minutes and 22.7 seconds per screw, respectively.

Conclusions: The results of this study demonstrate that the placement of K-wireless percutaneous pedicle screws is technically feasible and can be performed accurately and safely with short procedure and fluoroscopy times.

Key Words: percutaneous pedicle screw; K-wireless; K-wire; minimally invasive; technique