Injury phase

The Injury phase is the first and shortest phase of secondary fracture healing. It overlaps with the second phase, the inflammatory phase. In extreme cases, bone fragments can injure internal organs during the injury phase.

What is the injury phase?

A bone fracture can be primary and direct or secondary and thus indirect. In a primary fracture, the fragments are in contact or at least not much further than a millimeter apart. In the case of a secondary fracture, however, there is a gap that must grow together as the fracture heals.

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During secondary fracture healing, cells such as osteoblasts bridge the gap with a so-called callus made of mesenchymal cells, which is mineralized with calcium and thus stabilized in the later phases of fracture healing.

The healing of indirect fractures is called secondary fracture healing. It consists of five different phases. The injury phase is the first phase of the healing process. The following phases are the inflammation phase, the granulation phase, the callus hardening phase and the remodeling phase, which consists of modeling and remodeling the bone.

Function & task

Human bones are alive. They are accompanied by permanent growth and restructuring processes, which are also summarized as ossification. Osteoblasts build bones and osteoclasts remove bone tissue. This enables bones to adapt to changed conditions. In this way, after fractures, they can grow back together and even regenerate completely.

In primary fractures, the periosteum is not destroyed and the fragments can be connected by capillary-rich connective tissue. More complex in secondary fracture healing. The regeneration takes place in five phases, which initiate callus formation to bridge the gap.

The first phase of secondary fracture healing is the injury phase. Fractures are caused by direct or indirect force that overstrains the elasticity or strength of the bone. The bone is completely severed because it can no longer withstand the forces acting on it. Two or more fragments form and the bone loses its stabilizing function.

The injury phase or Phase of the fracture begins with the onset of violence. It only ends when there are no more forces acting on the bone or the surrounding tissue. The affected area absorbs the entire energy of the violence.

The injury phase is the shortest phase of the secondary fracture healing and usually does not last longer than a few seconds. During this phase, the extent, the angle and the exact location of the fracture are decided. The cortex, bone marrow, periosteum and surrounding tissue are severed or at least injured during the injury phase.

A hematoma then forms in the fracture gap. It bleeds into the bone fracture as numerous blood vessels in the immediate vicinity have been destroyed. The hematoma spreads along the crevice. At this point the fracture phase overlaps or merges with the inflammation phase.

Illnesses & ailments

Various complications can arise during the injury phase of secondary fracture healing. Depending on the location and severity of the violence, the bone fragments can damage organs in the immediate vicinity, for example, and thus cause severe internal bleeding.

Apart from this extreme case, the broken ends can move more or less far out of their physiological position, depending on the angle of the force. They then have to be brought back into a position that is as precisely as possible to the anatomy, otherwise the accompanying damage will quickly worsen or the bone fragments will grow together in a malposition. The repositioned bones must also be prevented from leaving the anatomically correct position during healing.

Fractures are more common in diseases such as glass bone disease or osteoporosis. Those affected by vitreous bone disease suffer from a mutation on chromosome 7 and 17. This genetic material codes for the protein collagen type I. The protein is an essential component of connective tissue. Since connective tissue plays a crucial role in bone formation, those affected suffer from abnormally structured bones with high fragility.

Osteoporosis patients also suffer from broken bones more often. This disease is characterized by decreased bone density. Those affected suffer from a disproportion between bone-building osteoblasts and bone-removing osteoclasts. An imbalance occurs during the permanent demineralization and remineralization of the bone substance.Bone mass is broken down by the osteoclasts to a greater extent than the osteoblasts produce bone mass. A slight imbalance is physiological, especially in old age. In the later decades of life, bones become more fragile due to age-physiology than they are at the beginning of life. In osteoporosis patients, however, there is a pathological imbalance in the activity of the osteoblasts and osteoclasts.