Comparison of morphology between patients with and without developmental spinal canal stenosis to inform the feasibility of C1Â lateral mass screw insertion in the atlas

The normally inserted C1 lateral mass screws have a diameter of 3.5-4.0 mm, and hence, the Tan method require a posterior arch height that exceeds this value. Our study provides evidence of a narrower posterior arch in Japanese individuals with developmental spinal canal stenosis. Therefore, the safe use of the Tan method to insert C1 lateral mass screws may be limited in Japanese individuals with developmental spinal canal stenosis.