Department of Orthopedic Surgery, Washington University School of Medicine, St. Louis, MO 63110, USA.
J Orthop Trauma. 2010 Feb;24(2):82-8. doi: 10.1097/BOT.0b013e3181b66f96.
Rotational malalignment during femoral nailing is common. The difference in cortical width of the proximal and distal fracture fragments, the cortical step sign, is a commonly used yet poorly studied method of evaluating rotational alignment. This study aims to critically analyze the cortical step sign in cadaveric specimens using radiographic and direct measurements.
One-centimeter segments from 20 cadaveric femora were harvested from the proximal, middle, and distal diaphyses. The medial and lateral cortical widths were measured in neutral and at 10 degrees , 20 degrees , and 30 degrees of internal rotation and external rotation directly from the gross specimens and indirectly using radiographs and cross-sectional imaging.
Anatomic, radiographic, and cross-sectional imaging measurements all demonstrated that cortical width changes with femoral rotation. Rotation (both internal rotation and external rotation) of the proximal and middle segments led to a decrease in medial cortical width and lateral cortical width in 70% to 100% of samples (up to 2.2 mm, or 20% of cortical width) indicating that the cortices are thickest directly medially and laterally in neutral rotation. In the distal femur, however, internal rotation and external rotation led to an increase in medial cortical width and lateral cortical width in 80% to 95% of cases (up to 1.75 mm), except in the case of the medial cortical width in internal rotation, which decreased in 80% of the specimens (up to 1.3 mm).
The cortical step sign, or incongruity of cortical widths on either side of a femur fracture, is indicative of rotational malreduction. Whether such malreduction is the result of internal rotation or external rotation, however, cannot be easily determined from this radiographic sign.
股骨钉固定时的旋转对线不良很常见。近端和远端骨折碎片皮质宽度的差异，即皮质台阶征，是一种常用但研究甚少的评估旋转对线的方法。本研究旨在通过尸体标本的放射学和直接测量来对皮质台阶征进行批判性分析。
从 20 具尸体股骨的近、中、远骨干段各采集 1 厘米的节段。直接从大体标本和间接通过 X 线片和横截面成像，在中立位和内旋 10 度、20 度和 30 度，以及外旋 10 度和 30 度时测量内侧和外侧皮质宽度。
解剖学、放射学和横截面成像测量均表明皮质宽度随股骨旋转而变化。近端和中段的旋转（内旋和外旋）导致 70%至 100%的样本（最多 2.2 毫米，或皮质宽度的 20%）中内侧皮质宽度和外侧皮质宽度减小，表明在中立位时皮质最厚直接位于内侧和外侧。然而，在远端股骨中，80%至 95%的情况下内旋和外旋导致内侧皮质宽度和外侧皮质宽度增加（最多 1.75 毫米），但内旋时的内侧皮质宽度除外，80%的标本中该宽度减小（最多 1.3 毫米）。
皮质台阶征，或股骨骨折两侧皮质宽度不一致，表明存在旋转对线不良。然而，根据这个放射学征象，无法轻易确定这种对线不良是内旋还是外旋的结果。
