[General fracture principles and imaging characteristics]

In the process of fracture healing, two different types (direct and indirect) are observed, which can be distinguished by radiologic imaging. If a fracture insufficiently consolidates without further treatment, regardless of the duration of prior treatment, it is referred to as a "non-union". This occurs in about 10% of long bone fractures.

The aim of this article is to provide an overview of the classification of fractures, an explanation of fracture healing and non-unions as well as their radiologic characteristics.

The diagnosis of fractures is based on physical examination and x‑ray with a minimum of two planes. If a soft tissue defect or complex fracture is suspected, a CT or MRI should be considered. For the treatment of non-unions, it might be helpful to expand the diagnostics to a CEUS (contrast-enhanced ultrasound) or DCE-MRI (dynamic contrast-enhanced magnetic resonance imaging).

Non-unions represent a severe limitation for the patient's quality of life and are often associated with a long period of suffering. In recent years, CEUS has been shown to be a useful and precise method for the diagnosis and assessment of non-unions and as a surrogate parameter for fracture consolidation.