The effect of sagittal and rotational malalignment of distal humeral fractures on elbow mobility: a cadaveric study

This study aims to investigate the correlation between axial and sagittal malrotation of distal humerus fractures and elbow mobility. A transverse distal humerus fracture was generated in 5 cadaveric specimens. Rotation of the distal humeral fragment was performed on the medial column with a stable lateral column, as well as rotation of the lateral column with a stable medial column. Elbow flexion and extension range of motion were measured and repeated with an additional 5° and 10° of sagittal flexion and extension fracture deformity. All 4 fracture types suffered extension loss with increasing rotation. A peak extension loss was found within the range of 10-14° rotational deformity. A significant decrease in flexion of up to 50° was found in type MS2 fractures due to the interference of the radial head and the humeral metaphysis. Conversely, increased flexion motion was found in MS1 types. Fracture types and rotational malalignment should be considered when analyzing distal humeral fractures to predict future mobility with conservative treatment. The radial head seems to be the dominant factor in type MS fractures to predict flexion increase or limitation, while the extension limitation will gradually increase in both LS and MS type fractures. Future in vivo radiological and clinical studies are needed to validate these results. Level of Evidence: 3b.