Purpose: The normal anterior translation of the articular surface of the distal humerus with respect to the humeral diaphysis facilitates elbow flexion. We hypothesize that there is a correlation between anterior translation of the distal humeral articular surface and flexion after open reduction and internal fixation (ORIF) of a fracture of the distal humerus.
Methods: Two independent observers evaluated 141 lateral radiographs of patients more than 6 months after fracture of the distal humerus and 155 lateral radiographs of patients without injury of the distal humerus. The distance between the most anterior point of the distal humerus articular surface, perpendicular to the humeral shaft, from the anterior border of the distal part of the humeral diaphysis, was measured on lateral radiographs as a percentage of the width of the humeral shaft.
Results: The technique of measuring anterior translation of the distal humeral articular surface had good intra- and interobserver reliability. The most anterior point of the distal humeral articular surface lies an average of 11.7 mm (range, 6.8 to 17.0 mm) in front of the most anterior border of the humeral shaft in normal distal humeri, which represents 62% of the humeral shaft diameter (range, 33% to 91%). There was a limited but significant correlation between flexion and anterior translation as a percentage of the humeral shaft diameter in distal humeri after fracture that was maintained in multivariable statistical models.
Conclusions: Using a reproducible technique for measuring anterior translation of the distal humerus, there was a correlation between anterior translation of the distal humeral articular surface and elbow flexion after ORIF. Although the weakness of the correlation emphasizes that limitation of elbow flexion after ORIF of a distal humerus fracture is multifactorial, reduced anterior translation of the distal humeral articular surface might be a contributing factor.
Type of study/level of evidence: Prognostic IV.