Korean J Neurotrauma.  2013 Oct;9(2):106-113. 10.13004/kjnt.2013.9.2.106.

Cervical Pedicle Screw Placement in Sawbone Models and Unstable Cervical Traumatic Lesions by Using Para-Articular Mini-Laminotomy: A Novice Neurosurgeon's Experience

• Yoon SD
• Lee JY
• Lee IS
• Moon SM
• Cho BM
• Park SH
• Oh SM

• KMID: 2156110
• DOI: http://doi.org/10.13004/kjnt.2013.9.2.106

Abstract

OBJECTIVE
This retrospective study was conducted to analyze the novice neurosurgeon's experience of cervical pedicle screw placement by using the technique with direct exposure of pedicle via para-articular mini-laminotomy.
METHODS
Fifteen sawbone models of subaxial spine were used (124 pedicles) to evaluate efficacy of repetitive training improving accuracy of cervical pedicle screw insertion. After that, we retrospectively reviewed 9 consecutive patients presented with traumatic cervical lesion. A total 38 cervical pedicle screws had been inserted. We analyzed the direction and grade of pedicle perforation on the postoperative computed tomography scan, and learning curve by using sawbone model.
RESULTS
In sawbone model group, the correct position was found in 102 (82.3%) screws, and the incorrect position in 22 (17.7%) screws. The incidence of incorrect screw position was 26.9% in the initial 9 sawbone model, and 0% after that. Among the 38 screws inserted in 9 patients, the correct position was found in 36 (94.7%) screws, and the incorrect position in a 2 (5.3%) screw. There was no neurovascular complications related with cervical pedicle screw insertion.
CONCLUSION
In vitro training to insert pedicle screw by using sawbone models could improve an accuracy of cervical pedicle screw placement by using this technique. Preliminary result revealed that cervical pedicle screw placement would be feasible and provide good clinical results in traumatic cervical lesions.

Keyword

Cervical pedicle screw; Laminotomy; Spinal instrumentation

MeSH Terms

Humans
Incidence
Laminectomy
Learning Curve
Retrospective Studies
Spine

Figure

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  FIGURE 1. Preoperative axial CT images (A: left-sawbone, right-patient) showing the diameter (arrow) and the convergence angle (θ) of the pedicle, and 3D reconstruction image of saw-bone (B) revealing the caudal angle between superior margin of pedicle (solid line) and imaginary line on which pedicle screw would be placed (dot line).

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  FIGURE 2. 2.5 mm diamond burr is used to perform para-articular mini-laminotomy (A). The laminotomy provides direct visualization of medial and superior wall of the pedicle (B). Burr is used to remove the outer cortex of the lateral mass over the entry point. The caudal angle (between solid and dot line) should be considered to determine the trajectory (C), and convergence angle should be determined under the direct visualization of the pedicle (D). P: pedicle, IF: inferior facet.

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  FIGURE 3. During the screw insertion, the pedicle should be visualized though the whole procedure (A). After the subperiosteal dissection of the pedicle, medial and superior wall of the pedicle (B, arrow) remained to be exposed by using a microdissector.

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  FIGURE 4. Grading system of the pedicle perforation. Grade 0: the screw is located within the pedicle (A). Grade 1: perforation less than 25% of the screw diameter (B). Grade 2: 25–50% of the screw diameter (C). Grade 3: over 50% (D).

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  FIGURE 5. During the procedure, pedicle perforation (arrow) is directly visualized on sawbone model (A), and post-procedural CT of sa bone model shows grade 1 perforation (B).

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  FIGURE 6. The number of total screws and screws showed incorrect position (>grade 2 perforation) in 15 consecutive cases of sawbone model. After initial 9 cases of sawbone model, there was no incorrect screw insertion.

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  FIGURE 7. Post-operative axial CT showing grade 3 perforation (A). Trajectory of the pedicle screw placement was indicated with dot lines. Due to an inadequate laminotomy, convergence angle underestimated along the lateral margin of the foraminotomy site (solid line). About 1–2 mm drilling of medial wall of lateral mass might be helpful to fully expose a proximal segment of pedicle (B).

Reference

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