Healing of Fractures

By Dr. Vishaal Bhat on Tuesday, 20 November, 2007 with 0 comments

Healing of fractures takes place by inflammatory and regeneration processes leading to reparation of bony tissue. Healing of bones is dependent on activity of osteoblasts, similarly to bone growth at young individuals or bone reconstruction at adults. The sources of osteoblasts are probably non-differentiated perivascular cells, capillary endothelia, monocytes and most likely also reticulous cells of bone marrow. A healing process begins with formation of hematoma at a breakage crevice and around it from broken vessels. Blood coagulum is the first bandage that joins a fracture. It is followed by formation of fibrin fibers network that is a basis for leading of growing bands of granulous tissue from the periosteum and the bone marrow, as well as Haver’s canals. A fracture provokes an aseptic inflammation of surrounding tissues accompanied by an edema and accumulation of cell elements. The amount of granulous tissue gradually increases which replaces hematoma between fragments. A capillary network is formed and growing fibroblasts create bands of ligamentous tissue strengthened by collagen fibers thus creating a primary fixing ligamentous callus.

According to course of healing process, two types of bone healing may be distinguished:

Primary bone healing

If bone fragments are left still and osteosynthesis is stable, bones heal by a contact way or by slit means, if a slit is present. It is a direct healing with absence of ligamentous callus. A fixation callus function is replaced by a rigid fixation by a splint. Contact healing takes place upon a close contact of both fragments which prevents growth of blood vessels from nearby areas, necrotic ends of fragments do not get resorbed and elimination and formation of a new bone take part simultaneously. Bone regeneration is provided by osteons growing at the rate of 0.1 mm per day thus making a bridge across a fracture line. At the osteon’s tip, osteoclasts form a resorption canal with a blood vessel, around which a bone is formed by osteoblasts.

Secondary bone healing

An indirect, secondary bone healing is typical for conservative therapy and surgical adaptive osteosuture that holds fragments together. Healing proceeds in two phases:

  • first, the above described primary fixation callus is formed which ensures a mechanical rest for healing

  • the callus is reconstructed and remodeled at the second phase: osteoblasts form an osteoid along blood vessels at the callus; this osteoid is gradually calcified and ligamentous fibers are built up at the bone.

  • Remodeling is the last phase of healing, during which periosteal and endosteal calluses are resorbed and bone marrow is remade.

Category: Pathology Notes



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