• Dong-Ho Lee, Hyounmin Noh, Chang Ju Hwang, Choon Sung Lee, Kuniyoshi Abumi, and Jae Hwan Cho.
• Department of Orthopedic Surgery, Asan Medical Center, University of Ulsan College of Medicine, Seoul, Korea.
• Spine. 2017 Feb 1; 42 (3): E136E141E136-E141.

Study DesignA retrospective case-control study.ObjectiveThis study aimed (A) to compare entry points and trajectories of the cervical pedicle screw (CPS) between degenerative and nondegenerative spines, and (B) to evaluate the risk of facet joint violation by the CPS according to the degree of facet degeneration.Summary Of Background DataEntry point, trajectories, and risk of misplacement of the CPS have been widely researched; however, its application to degenerative cervical spine has to be elucidated.MethodsSixty patients who underwent cervical surgeries at our institution were classified into two groups according to cervical facet joint degeneration. A simulation program with 0.7-mm thickness axial computed tomographic images was used to evaluate facet joint violation by the CPS from C3 to C6. Horizontal and vertical offsets of entry points were measured from two different anatomical landmarks on lateral mass, namely the lateral notch and the center of the superior ridge. The transverse and sagittal angles of the screws were also measured. Facet joint violation was evaluated and classified into either "minor" (<50% of screw diameter) or "major" (≥50% of screw diameter).ResultsThe mean transverse and sagittal angles showed no difference between the two groups. However, a more superior vertical offset from the superior ridge in terms of entry point was observed in the degenerative cervical spine group at all levels (P = 0.001-0.026). In addition, facet joint violation was more frequently found in severely degenerated facet joints than in mild to moderately degenerated facet joints (P = 0.011).ConclusionThe entry point of CPS was moved more superiorly in the degenerative cervical spine in this study, which increased the risk of facet joint violation in our patients. Thus, surgeons need to modify the insertion technique of the CPS or to insert lateral mass screw instead of the CPS when it is considered to insert screws at the uppermost vertebra in the degenerative cervical spine.Level Of Evidence4.

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