The effect of impact tool geometry and soft material covering on long bone fracture patterns in children

Introduction: The effect of impact tool geometry and soft material covering on bone fracture patterns plays a major role in fracture patterns. However, the literature is nearly void of such studies and only general correlations between the fracture pattern and the mechanism underlying the insult were reported. Purpose: The aim of this study is to reveal the association between the geometry of the impact tool and the presence of soft material covering on bone fracture patterns. The Dynatup Model POE 2000 (Instron Co.) low energy pendulum impact machine was utilized to apply impact loading on fresh pig femoral bones (n = 50). The bone clamp shaft was adjusted to position the bone for three-point bending with additional bone compression simulating a situation occurring in pedestrian road traffic accidents. Five different tests using varying impact tool sizes with and without soft interface covering were carried out. Results: A significant positive correlation was found between the fracture features and the impact tool’s geometry. Only bones that were damaged by a rounded impact body result in a “false” butterfly fragment; in all other cases where the impact body is flat and wide, double trapezoid fragments are observed in the area of impact. The impacted aspect is the most affected. All fracture line features were significantly greater in bones subjected to an impact by tools without soft covering. With an impact with soft covering, the impacted aspect exhibits numerous unique fracture lines and a fragmented pattern. Our study clearly shows that impact tool geometry and soft material covering markedly affect the fracture pattern.