Burghardt Rolf D, Herzenberg John E, Burghardt Manfred H
Abteilung für Kinderorthopädie, Altonaer Kinderkrankenhaus, Hamburg, Germany.
J Appl Biomech. 2011 Nov;27(4):385-91. doi: 10.1123/jab.27.4.385. Epub 2011 Aug 26.
Femoral lengthening with intramedullary nails can create alterations in the mechanical axis of the limb. This is based on the relationship of the anatomic femur axis to the mechanical femur axis, which is typically 5-9 degrees valgus. We developed trigonometric formulas to calculate the predicted change, using the lengths of the tibia, femur, and whole limb; the amount of lengthening; and the angle between the anatomic and the mechanical axis of the femur. We recognized three patterns depending on whether the overall limb mechanical axis is lateral (valgus), medial (varus), or straight through the center of the knee. The varus and valgus patterns lead to similar formulas. When the mechanical axis goes directly through the center of the knee joint, the formula simplifies. These formulas could be incorporated into digital radiographic programs to predict the change in mechanical axis deviation that will develop from lengthening along the anatomic femur axis with an intramedullary lengthening nail.
使用髓内钉进行股骨延长会导致肢体机械轴的改变。这是基于解剖学股骨轴与机械性股骨轴的关系，机械性股骨轴通常有5至9度的外翻。我们开发了三角公式，利用胫骨、股骨和整个肢体的长度、延长量以及股骨解剖轴与机械轴之间的角度来计算预测变化。根据整个肢体机械轴是外侧（外翻）、内侧（内翻）还是直接穿过膝关节中心，我们识别出三种模式。内翻和外翻模式会得出相似的公式。当机械轴直接穿过膝关节中心时，公式会简化。这些公式可纳入数字放射成像程序，以预测使用髓内延长钉沿解剖学股骨轴延长后机械轴偏差的变化。
