Feasibility and limitations of C1 lateral mass screw placement in patients of atlas assimilation
Section snippets
Patient population
In a period from April 2008 to March 2009, a consecutive group of 17 C1A patients with original computer tomographic (CT) data was prospectively collected, to study the morphological changes of C1 lateral mass and factors influencing C1 lateral mass screw placement. All 17 patients had AAD or AAI confirmed by reconstructed CT, and/or dynamic MR, in which ventral compression of spinal cord increased in flexion. Six of them had also Chiari's malformation and/or syringomyelia. 17 patients were
Morphological observation
In all 17 patients, C1A was diagnosed by reconstructed CT scan and characterized by C1 lateral mass and condyle fusion. C1 anterior and posterior arch fusion with foramen magnum was present in all but 3 patients. Four patients had Klippel–Feil syndrome, with C2–C3 fusion in 2, C2–C4 fusion in 1, and C4–C5 fusion in 2 patients. All patients had congenital basilar invagination, of which 14 had AAD, the mean atlantodens interval was 6.2 mm, and other 3 patients had AAI, in which ventral compression
Discussion
In the presence of atlas assimilation, occipitocervical fixation for stabilization of atlantoaxial dislocation seems to be a reasonable strategy of surgical treatment. Although direct screw implantation into the C1 lateral mass in the presence of atlas assimilation is relatively difficult and dangerous, the screw purchase is much stronger in the thick and large lateral mass than screw implantation in the relatively thin occipital squama [16], [18]. Goel et al. [2] first reported the use of C1
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