Femoral-shaft fractures and nonunions treated with intramedullary nails: the role of dynamisation.

Dynamisation of a previously interlocked intramedullary nail is believed to stimulate an osteogenic response due to increased load across the fracture site. The purpose of this study was to retrospectively investigate fracture patterns that could tolerate dynamisation without the risk of major complications. Thirty patients (24 males) with an average age of 33 years (17-90) were studied. As many as 21 suffered from a fresh femoral fracture, whereas the remaining nine patients suffered from femoral nonunions. Four patterns of osseous lesion were recognised in terms of mechanical stability under a dynamic nail and biological activity at the fracture/nonunion site: stable/hypertrophic, stable/atrophic, unstable/hypertrophic and unstable/atrophic osseous lesions. Complete union (within 6 months) occurred in 21 patients. Six fractures united within the 7th-11th post-dynamisation month and, in the remaining three cases, a nonunion developed. Significant femur shortening (>20 mm) was noticed in four patients and rotational malalignment in one patient. Logistic regression analysis revealed high odds ratio (OR=70, 95% confidence interval (CI) 2.5-1998) for the unstable/atrophic pattern of osseous lesion to develop major complications. In the unstable/atrophic pattern of osseous lesion, dynamisation should never be done, as it could lead to significant complications.