Quasi-static and dynamic bending stress of the pediatric femur for producing a femoral fracture

Abstract

At the Institute of Forensic Medicine of the University of Heidelberg, in the years 1986-1988 thigh loading tests were conducted in order to produce fractures in a total of 28 cadavers of babies and children who had died at ages ranging from 1 day to 6 years. In 18 tests a universal strength testing machine was used and each thigh was loaded quasi-statically from the outside with a blunt edge applied to the middle of the femur, bending it to the point of fracture. The loading velocity amounted 50 mm/min with a defined support distance. The breakage load amounted to 470 N in a 6-day-old baby and increased about evenly up to 2920 N in a 6-year-old child; however, in a newborn 2720 N was needed and in a 15-month-old child, 5700 N. The total deformation way ranged from 16 to 60 mm. The main types of fracture that occurred were: complete and incomplete transverse fractures, oblique fractures, Messerer fractures, and spongiosa fractures. Ten children ranging in age from 2 months up to 27 months were submitted to dynamical thigh loading by means of a failing weight impactor and a horizontal impactor. Only in one case did a transverse fracture occur, when the lateral thigh impacted on an edge at a falling height of 70-93 cm. The forces set up amounted to 320-600 N with the falling weight impactor and to 2370 N with the horizontal impactor. These results suggest that fracture of the femur does not occur if a baby or small child falls from a changing table or from an adult's arm.