Three-Dimensional Printed Targeting Device for Scaphoid Fracture Fixation

Abstract

Background: Percutaneous guide wire insertion for scaphoid screw fixation can be challenging and often requires multiple attempts with significant radiation exposure to the surgical team. A 3-dimensional (3D) printed targeting device has the potential to reduce procedure time and intraoperative radiation exposure. Methods: Our targeting device protocol included a preprocedure computed tomography (CT) scan of a casted cadaver wrist, followed by 3D printing of a customized targeting guide. In a comparison trial, seven orthopedic surgery residents performed percutaneous scaphoid guide wire insertion on different cadaver specimens by both freehand technique and using our targeting device. Radiation exposure and procedure times were compared. All specimens underwent postprocedure CT to assess Kirschner wire (K-wire) accuracy, determined by central third placement. Pre- and postprocedure CT scans from the targeting device group were co-registered to compare planned and actual K-wire trajectories. Results: Using the freehand technique, mean fluoroscopy time was 120 seconds (standard deviation: ±53 seconds) generating 2.45 milligray of radiation. Average procedure time was 21 minutes with a mean of 6.4 (range: 3-9) insertion attempts. A single insertion attempt was made using the targeting device with an average procedure time of 30 seconds and no fluoroscopy exposure. Four K-wires were placed within the central scaphoid in both groups. Using the targeting device, average linear deviation from the planned trajectory was 2.1 mm, while the maximum linear deviation was 3.75 mm. Conclusion: When compared to freehand scaphoid guide wire insertion, our targeting device provides similar accuracy while significantly reducing intraoperative radiation exposure and procedure time.

Keywords: diagnosis; fracture/dislocation; research & health outcomes; scaphoid; specialty; surgery; trauma; treatment; wrist.

Figure 1.

Plastic window frame designed to be embedded in the cast and serve as the attachment site for the targeting device. The flanges allow fiberglass casting tape to secure the window frame in position over the scaphoid tubercle.

Figure 2.

The window frame (from Figure 1) now embedded in fiberglass casting material over the volar wrist of a cadaver arm. The black dot represents the scaphoid tubercle.

Figure 3.

With the window frame and cast in place, a computed tomography scan is performed. Thresholding of the bone is performed isolate a 3D representation of the bone. At this point, the scaphoid can be displayed alone and the desired trajectory defined.

Figure 4.

The black targeting guide has been positioned in the white window frame. The targeting device snaps into position when appropriately aligned. A nylon cable tie was added for security. A K-wire was inserted through the guiding cylinder of the targeting device and advanced with a wire driver.

Figure 5.

Computed tomography (CT) 3-D reconstruction demonstrating a Kirschner wire (K-wire) successfully entering the scaphoid after using our CT-guided procedure. The guiding cylinder of the targeting device can be seen surround the K-wire shaft.

Figure 6.

Example of co-registered pre- and postprocedure computed tomography images demonstrating the planned trajectory (solid green line) and the actual Kirschner wire (K-wire) trajectory (dashed red line). Osseous structures are comprised of blue dots and individual bones are labeled. The portion of the planned trajectory that travels within the scaphoid bone is defined by the solid red line. The agreement between the planned and actual trajectories is examined and the maximum deviation was measured.

Figure 7.

Co-registered pre- and postprocedure computed tomography (CT) images of the scaphoid demonstrating the CT-guided procedure attempt with the largest deviation from the center of its planned trajectory (thin solid line). The actual Kirschner wire (K-wire) trajectory (thick dashed line) measured 3.75 mm at its maximum point of deviation.