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Placement of C-7 intralaminar screws: a quantitative anatomical and morphometric evaluation
Mehmet Şenoğlu1, Fuat Özkan, Mustafa Çelik
1Departments of Neurosurgery, Kahramanmaraş Sütçüimam Universitesi School of Medicine, Kahramanmaraş, Turkey. mehmetsenoglu@hotmail.com
Object:
Crossing laminar screws at C-7 have been recently described as a method for the fixation of C-7. In this study the authors measured locations on axial CT scans to determine the feasibility of placing a screw in the C-7 lamina, and they evaluated the reliability of the surface of the dorsal arch of C-7 as a landmark for determining the optimal site of screw entry.
Methods:
A total of 207 axial CT scans of C-7 spines were evaluated, and 4 critical measurements were determined for screw entry points, trajectories, and lengths for placement of intralaminar screws.
Results:
The mean width of the right C-7 lamina was 5.9 mm (range 4.2-9.3 mm). The mean width of the left C-7 lamina was 6.0 mm (range 4.2-10.2 mm). The laminar width was too small (< 5.5 mm) in 37.7% of cases to accommodate a 3.5-mm diameter screw, given the desire for at least 1 mm of play on each side of the screw.
Conclusions:
These measurements provide guidelines for operating on the posterior aspect of C-7 and enhance the confidence of the surgeon. Viewing the anatomy of the C-7 laminae in detail through preoperative CT scanning can greatly assist the surgeon in choosing the fixation method. The width of the C-7 lamina is sufficient for intralaminar screw placement in more than 60% of patients.
