Prabhakar Pooja, Pierce William A, Standefer Karen D, Ho Christine A
UT Southwestern School of Medicine, Dallas, TX.
Texas Scottish Rite Hospital for Children, Dallas, TX; and.
J Orthop Trauma. 2020 Jul;34(7):e245-e249. doi: 10.1097/BOT.0000000000001735.
Acceptable amounts of malrotation after CRPP for pediatric supracondylar humerus fracture (SCHFx) have yet to be defined. This is an attempt to correlate radiographic parameters of a malrotated SCHFx with degrees of rotational malalignment to assist intraoperative assessment of reduction.
3D models of a left distal humerus were printed, simulating a transverse SCHFx with 5, 10, 15, 20, 25, and 30 degrees of malrotation. Four different scenarios were developed: (1) lateral cortical axis of rotation, (2) medial cortical axis of rotation, (3) centroid of the humerus longitudinal axis with the medial condyle rotated posteriorly, and (4) centroid of the humerus longitudinal axis with the medial condyle rotated anteriorly. Anteroposterior and lateral fluoroscopic views were taken with a consistent image profile. Five observers measured the amount of metaphyseal overhang on the lateral view and the width of the distal humerus just proximal to the fracture to establish amount of overhang as a percentage of distal humerus width. Regression analysis established "best fit" lines for the 4 scenarios. Ten observers used the observed characteristics of each type of malrotation and "best fit" lines to estimate axis and degrees of malrotation using the same fluoroscopy of the 24 models.
The intraclass correlation coefficient of reliability for percentage of metaphyseal overhang ranged from 0.775 to 0.987. Observers correctly predicted axis of malrotation in 76% and correctly predicted amount of malrotation in 75% of models.
Estimation of axis of malrotation and degrees of malrotation within 5 degrees in SCHFx can be predicted in 75% of our 3D printed models.
儿童肱骨髁上骨折（SCHFx）经儿童弹性髓内钉固定术（CRPP）后可接受的旋转不良量尚未明确。本研究旨在将旋转不良的SCHFx的影像学参数与旋转畸形程度相关联，以辅助术中复位评估。
打印左肱骨远端的3D模型，模拟具有5°、10°、15°、20°、25°和30°旋转不良的横行SCHFx。开发了四种不同的情况：（1）外侧皮质旋转轴，（2）内侧皮质旋转轴，（3）肱骨纵轴的质心且内侧髁向后旋转，以及（4）肱骨纵轴的质心且内侧髁向前旋转。以一致的图像轮廓拍摄前后位和侧位透视图像。五名观察者测量侧位片上干骺端悬垂量以及骨折近端肱骨远端的宽度，以确定悬垂量占肱骨远端宽度的百分比。回归分析为这四种情况建立了“最佳拟合”线。十名观察者利用每种旋转不良类型的观察特征和“最佳拟合”线，通过对24个模型进行相同的透视来估计旋转轴和旋转不良程度。
干骺端悬垂百分比的组内相关系数可靠性范围为0.775至0.987。观察者在76%的模型中正确预测了旋转不良轴，在75%的模型中正确预测了旋转不良量。
在我们75%的3D打印模型中，可以预测SCHFx中旋转不良轴和5°以内的旋转不良程度。
