J Korean Neurosurg Soc.  2015 Jul;58(1):9-13. 10.3340/jkns.2015.58.1.9.

Pedicle Screw Placement in the Thoracolumbar Spine Using a Novel, Simple, Safe, and Effective Guide-Pin : A Computerized Tomography Analysis

• Hyun SJ
• Kim YJ
• Rhim SC
• Cheh G
• Cho SK

• KMID: 2067098
• DOI: http://doi.org/10.3340/jkns.2015.58.1.9

Abstract

OBJECTIVE
To improve pedicle screw placement accuracy with minimal radiation and low cost, we developed specially designed K-wire with a marker. To evaluate the accuracy of thoracolumbar pedicle screws placed using the novel guide-pin and portable X-rays.
METHODS
Observational cohort study with computerized tomography (CT) analysis of in vivo and in vitro pedicle screw placement. Postoperative CT scans of 183 titanium pedicle screws (85 lumbar and 98 thoracic from T1 to L5) placed into 2 cadavers and 18 patients were assessed. A specially designed guide-pin with a marker was inserted into the pedicle to identify the correct starting point (2 mm lateral to the center of the pedicle) and aiming point (center of the pedicle isthmus) in posteroanterior and lateral X-rays. After radiographically confirming the exact starting and aiming points desired, a gearshift was inserted into the pedicle from the starting point into the vertebral body through the center of pedicle isthmus.
RESULTS
Ninety-nine percent (181/183) of screws were contained within the pedicle (total 183 pedicle screws : 98 thoracic pedicle screws and 85 lumbar screws). Only two of 183 (1.0%) thoracic pedicle screws demonstrated breach (1 lateral in a patient and 1 medial in a cadaver specimen). None of the pedicle breaches were associated with neurologic or other clinical sequelae.
CONCLUSION
A simple, specially designed guide-pin with portable X-rays can provide correct starting and aiming points and allows for accurate pedicle screw placement without preoperative CT scan and intraoperative fluoroscopic assistance.

Keyword

Pedicle screw; Guide-pin; Accuracy; Computerized tomography

MeSH Terms

Cadaver
Cohort Studies
Humans
Spine*
Titanium
Tomography, X-Ray Computed
Titanium

Figure

• 

  Fig. 1 Photograph (upper left) and schematic illustrations show the precise dimensions of the specially designed guide-pin with a ball maker. The guide-pin is composed of stainless steel. The guide-pin with a ball maker defines the ideal starting point by a ball marker located 15 or 20 mm proximal to the tip and the aiming spot by the tip of the guide-pin.

• 

  Fig. 2 A novel guide-pin was inserted into the pedicle to identify the correct starting point (A : the laminar 2-3 mm lateral to the center of the pedicle) and aiming spot (B : center of the pedicle isthmus).

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  Fig. 3 Steps required for pedicle screw fixation with the specially designed guide-pin. Step 1 : complete exposure of the bony anatomy; step 2 : starting point burr (2 mm) with alleged recommendation; step 2-1 : Define the ideal starting point and aiming spot using C-arm or portable postero anterior/lateral X-rays; step 3 : the gearshift insertion according to the X-rays; step 4 : inner pedicle palpation and length measurement; step 5 : tapping and repalpation; and step 6 : screw placement slowly.

• 

  Fig. 4 Adjusting the starting point and aiming spot after complete placement of guide-pin. Guide-pin A : starting point (ball marker) looks okay (2-3 mm lateral to the center of the pedicle) but tip of the guide pin violated medial wall of the pedicle. Ideal targeting (arrows) : same starting point but near perpendicular gearshift insertion required.

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  Fig. 5 Coronal and sagittal plane radiographs should confirm the harmonious position of the screws by the surgeon.

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