Nonunion is a failure of healing of bone. It can be difficult to define; the most common definition is by the US Food and Drug Administration who defined it in 1986 as “when a minimum of 9 months has elapsed since injury and the fracture shows no visible progressive signs of healing for 3 months”. Different bones however heal at different rates, so some apparently slow fractures may heal without further intervention.
There are several factors that influence union, notably age, nutrition, co-morbidities (notably diabetes and vascular disease), medication use (steroids and NSAID drugs) and smoking. There are also local factors such as whether there was an open fracture, how ‘comminuted’ the fracture is (ie how many pieces), the energy transmitted to the soft tissues, and any crushing thereof, and if there might be infection present.
Simple aids to treatment therefore include smoking cessation, avoidance of anti-inflammatory drugs, adequate nutrition (including vitamin D and calcium).
Ideally a treatment should allow functional use of the limb, both to avoid stiffness but also use of a limb can promote healing.
Investigation may be necessary to exclude infection, and thus may include blood tests (notably White Blood Cell count (WBC), C-reactive Protein level (CRP) and ESR) Scans may also be needed (MRI or Nuclear Medicine scans such as SPECT-CT)
Nonunions can be broadly categorized into those that produce a lot of bone but it fails to join across the fracture (hypertrophic) and those where there is little biological activity (atrophic). Either can be infected. If infection is present, it is difficult to eradicate. Antibiotics can only get to infection via the bloodstream, so areas with poor or no blood supply can act as reservoirs for germs, notably any implanted metalwork or dead tissue particularly bone that has a poor supply to start with.
Treatment can involve a variety of techniques including bone grafting, more secure fixation, or the use of external fixators.
Other interventions such as the use of Low Intensity Pulsed Ultrasound (LIPUS) such as Exogen therapy, bone morphogenetic proteins (BMPs), callus distraction histiogenesis (Ilizarov technique) lie alongside the more classic treatments. Commonly however the problem lies with poorly vascularised bone, and commonly stimulus in the form of natural bone graft, stability and fresh bleeding bone ends is vastly more important than these adjuncts.