Bone healing can involve a combination of primary and secondary processes based on the stability throughout the construct.įailed or delayed healing can affect up to 10% of all fractures and can result from factors such as comminution, infection, tumor, and disrupted vascular supply. During this article, we will work through each of these steps in order and detail before touching on primary healing, factors affecting fracture healing, and methods of stimulation of fracture healing. And it occurs via endochondral bone healing. These fixation modalities achieve a mechanical strain between 2-10%. The other type is secondary bone healing which occurs in non-rigid fixation modalities such as braces, external fixation, plates in bridging mode, intramedullary nailing. It is an intramembranous bone healing that occurs through Haversian remodeling. There are two main modes of bone healing primary bone healing is dictated by absolute stability constructs that achieve a mechanical strain below 2%. In contrast, a strain >10% results in non-union or delayed union. Primary bone healing ensues with mechanical strain below 2%, whereas secondary bone healing ensues when the mechanical strain is between 2 and 10%. The amount of the involved strain dictates the biological behavior of the cells involved in the healing process and, consequently, the type of bone healing. An appropriate mechanical stimulation, such as strain, facilitates tissue formation at the bony ends. The type of fracture healing is governed by the achieved mechanical stability at the fracture site and, consequently, the strain.

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