Pediatric Supracondylar Fractures: Variation in Fracture Patterns and the Biomechanical Effects of Pin Configuration

Abstract

Transverse pediatric supracondylar fractures through the midolecranon fossa are frequently encountered and modeled in biomechanical studies. Our objective is to investigate the optimal pin configurations for low, sagittal oblique, and high fracture varieties that have not been previously investigated. A total of 100 synthetic composite pediatric humeri were tested. Three groups of 30 were used to simulate 1 of 3 fracture variations. Subgroups of 10 were stabilized with 2 lateral pins (2LP), 3 lateral pins (3LP), or cross K-wires (XP). The 90 fracture and 10 intact models were tested for anterior posterior (AP), medial lateral (ML), and rotational stiffness. In low fractures, AP, ML, and rotational stiffness of 2LP and 3LP were similar to intact. ML stiffness was less using XP. AP and ML stiffness of 2LP and 3LP were significantly greater than XP.In oblique fractures, AP, ML, and rotational stiffness of 2LP was similar to intact but 3LP was significantly less. AP and ML stiffness of XP was significantly less. 2LP demonstrated greater AP, ML, and rotational stiffness than 3LP and XP.In high fractures, all configurations demonstrated significantly less rotational stiffness than intact and AP stiffness similar to intact. Rotational stiffness of 3LP was greater than 2LP and XP. AP and ML stiffness were not different among configurations. 2LP are stiffer than 3LP and XP for sagittal oblique fractures. 2LP and 3LP stiffness were similar in low transverse fractures, and both constructs demonstrated greater stiffness than XP configuration. 3LP is preferable for high transverse fractures. XP were never stiffer than the lateral only constructs in any of the patterns tested. All-lateral pin constructs may provide adequate stiffness to maintain reduction of low transverse, sagittal oblique, and high transverse patterns of pediatric supracondylar humerus fractures without risk of injury to the ulnar nerve.