Can We Estimate the Amount of Malrotation in Supracondylar Humerus Fractures After CRPP?

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.