The most stable pinning configurations in transverse supracondylar humerus fracture fixation in children: A novel three-dimensional finite element analysis of a pediatric bone model.

PURPOSE

This study aimed at finding out the effect of exit height, trajectory and number of pins on the stability of cross and divergent-lateral pins used in the fixation of extension-type, transverse supracondylar humerus fracture (SHF) in children, based on finite element analysis.

METHODS

Distal humerus model consisting of the ossific nucleus of the capitellum (ONC) and distal cartilage of a 6-year-old boy was developed via three-dimensional finite modeling. Various cross and divergent-lateral pinning models with either two or three pins were simulated on an extension-type, transverse SHF and tested in six loading directions.

RESULTS

Two-cross pins and 2-divergent-lateral pins were more stable against torsional and translation forces respectively, while 3-cross pins were the most stable against all forces. The cross pins exiting at the upper border of the distal metaphyseal-diaphyseal junction (MDJ) had the best stiffness among the 2-cross pins, while the lateral pins with a middle third ONC distal pin provided the best stiffness among the 2-lateral pins. A third olecranon fossa pin greatly enhanced stability of the 2-lateral pins.

CONCLUSION

For typical transverse fractures, 2-cross pins are found to be superior to 2-divergent lateral pins only against torsional forces. Pins exiting at the upper border of the MDJ provides the best mechanical stability with 2-cross pins. Two-divergent-lateral pins with a distal pin going through the middle third of the ONC provides the best mechanical stability against translation forces for these transverse fractures. Three-cross pins however offer the best mechanical stability against both translation and torsional forces. This study offers important clues in the preoperative evaluation and management of extension-type supracondylar fractures in children.