横截面积与前后径是否矛盾？

The spinal cord in adults ends at the upper border of the first lumbar vertebral body and continues as nerve roots, the cauda equina. The central canal anteroposterior diameter ranges from 15 to 23 mm. Commonly, the threshold for radiographic lumbar spinal stenosis is an anteroposterior diameter of less than 12 mm, with relative spinal canal stenosis, and less than 10 mm, with absolute spinal stenosis [7, 44]. Alternatively, some clinicians define spinal stenosis not on a specifically quantified diameter but as relative reduction in cross-sectional area with mild as narrowing of the anteroposterior diameter canal by one-third or less, moderate by narrowing by one- to two-thirds, and severe as more than two-thirds [7, 11].

成人的脊髓终止于第一腰椎椎体的上缘，延续为神经根，即马尾神经。腰椎中央管前后径为15~23mm。通常，影像学上腰椎管相对狭窄的界值为前后径小于12mm，小于10mm为绝对椎管狭窄^[7,44]。除此之外，一些临床医生对椎管狭窄的定义不是基于具体的量化直径，而是相对减少的椎管横截面积。前后径狭窄1/3以下为轻度，中度为1/3～2/3，超过2/3为重度狭窄^{[7, 11]}。

横截面积与前后径是否矛盾？