Monofocal Distraction of Stiff Hypertrophic Nonunions. How and Why Does It Work? A Systematic Review and Mechanobiological Explanation

Stiff nonunions represent a unique subgroup of nonunions which pose distinct management challenges. Distraction of stiff nonunion, although seemingly counterintuitive, has for long been shown to provide predictable results. Potential advantages of such a management protocol include gradual correction of deformity and limb length; noninvasive nature with minimal insult to the local biology, and in some cases, resolution of infection. In the present article, we systematically review publications describing the results of monofocal distraction of stiff nonunions. An overall union rate of >95% without bone grafting was seen in 178 patients across 12 included publications. The theoretical mechanobiological explanation for the success of this management strategy is also explored.