Categorising bone defect hematomas - Enhance early bone healing.

Fracture hematoma formation describes a transitional phase that involves a dynamic and tightly choreographed interaction between the fibrin matrix, cells, and cytokines that guides the ensuing bone repair. Here we propose a novel hypothesis to explain why hematomas in conjunction with critical sized bone defects are prone to differentiate into fibrous tissues, which eventually results in non-unions of the bone. We postulate that certain hematoma qualities are triggers that influence cell biological behaviours and that the release of certain growth factors determines what pattern of remodelling will prevail: intramembranous or endochondral ossification. A detailed characterization of the structural parameters of hematomas will allow researchers to create a microenvironment that aids the migration of mesenchymal stromal cells into the hematoma where, once established, they accelerate the bone healing process. Such a strategy would be particularly useful when faced with the complications arising from large recalcitrant bone defects that often fail to heal naturally.