Secondary fracture healing processes are strongly influenced by interfragmentary motion. Shear movement is assumed to be more critical than axial movement, however experimental results are controversial. Numerical fracture healing models allow to simulate the fracture healing process with variation of single input parameters and under comparable normalized mechanical conditions. Therefore, a direct comparison of different in vivo scenarios is possible. The aim of this study was to simulate fracture healing under several axial and shear movement scenarios and compare their respective time to heal. We hypothesize that shear movement is always more critical than axial loading. For the presented study, we used a corroborated numerical model for fracture healing in sheep. Numerous variations of the movement amplitude, the fracture gap size and the musculoskeletal loads were simulated for comparable axial compressive and shear load cases. In all simulated cases, axial compressive load had less inhibitory influences on the healing process than shear load. Therefore, shear loading is more critical for the fracture healing outcome in general. Thus, our findings suggest osteosynthesis implants to be optimized to limit shear movements under musculoskeletal loading

Aims

Several previously identified patient-, injury-, and treatment-related factors are associated with the development of nonunion in distal femur fractures. However, the predictive value of these factors is not well defined. We aimed to assess the predictive ability of previously identified risk factors in the development of nonunion leading to secondary surgery in distal femur fractures.

Objectives

External fixators are the traditional fixation method of choice for contaminated open fractures. However, patient acceptance is low due to the high profile and therefore physical burden of the constructs. An externalised locking compression plate is a low profile alternative. However, the biomechanical differences have not been assessed. The objective of this study was to evaluate the axial and torsional stiffness of the externalised titanium locking compression plate (ET-LCP), the externalised stainless steel locking compression plate (ESS-LCP) and the unilateral external fixator (UEF).