Human atrophic fracture non-unions are not avascular

A small proportion of fractures progress to non-union. Non-unions are routinely classified into two groups either hypertrophic or atrophic according to their radiological appearance. It is a common preconception that non-unions with a hypertrophic appearance on X-ray are biologically active and vascular with potential to heal given the correct stable environment. Atrophic non-unions are considered to be avascular and inert and will not heal even under the correct stable environment. Non-unions are either infected or aseptic. In the present study, we tested the hypothesis that aseptic atrophic non-unions are less vascular than aseptic hypertrophic non-unions and healing fractures. Biopsies were taken from the fracture gap of patients with healing fractures, hypertrophic non-unions and atrophic non-unions. A dual labelling technique was used with antibodies against CD31 (JC70) and Collagen IV. Blood vessels were quantified using a Chalkley point eyepiece graticule. There was no statistically significant difference in the median vessel count between the three fracture groups. These findings do not support the hypothesis that established atrophic fracture non-union are less vascular than hypertrophic non-unions or healing fractures.