What are the characteristics of the primary bone healing process?

Primary osteonal reconstruction requires absolute stability with an interfragmentary strain of less then 2%. Contact healing or gap healing only occurs with anatomic alignment of the fracture ends with a maximum width of the gap of maximal 1mm. Another anatomical factor compromising the fracture healing is the intra-articular position of the fracture where the synovial fluid prevents blood clot formation thereby eliminating a factor contributing to bone healing.