Fractures and osteotomies that are stabilized with rigid compression plating undergo primary bone healing, also known as haversian remodeling. Absolute stability constructs, such as a compression plate, allow for bone healing without visible callus formation. Healing occurs via extension of clusters of osteoclasts (known as osteonal cutting cones) across the fracture site, along with osteoblasts depositing new bone and blood vessels to re-establish the haversian system.
Seconday bone healing occurs when fractures heal through callus formation. Relative stability constructs, such as an intramedullary nail, allow for some motion at the fracture site which leads to healing through a cartilage scaffold (endochondral ossification).
Illustration A demonstrates a transverse fracture stabilized with a compression plate. Illustration B shows a femoral shaft fracture that has healed through callus formation.
Answer 2: Secondary healing through callus formation occurs when fractures heal with some motion at the fracture site; for example intramedullary nailing of a diaphyseal femur fracture
Answer3: Primary healing is defined by the absence of visible callus
Answer 4: Endochondral ossification is bone generation or healing through a cartilage scaffold
Answer 5: Secondary healing does not occur through osteonal cutting cones as there not enough stability at the fracture site
Buckwalter JA, Einhorn TA, Simon SR (eds): Orthopaedic Basic Science: Biology and Biomechanics of the Musculoskeletal System. Rosemont, IL, American Academy of Orthopaedics Surgeons, 2000, pp 371-399
Koval KJ (ed): Orthopaedic Knowledge Update 7. Rosemont, IL, American Academy of Orthopaedic Surgeons, 2002, pp 19-29.