Stages of fracture healing

Hello students and my dear friends, today I'm going to discuss the healing of fractures of cortical bone & cancellous bone along with the factors affecting fracture healing.

Let's first discuss the stages of healing fracture of cortical and cancellous bone.

The healing of bone differs from soft tissue healing from the stage of granulation tissue formation.

STAGES IN FRACTURE HEALING( CORTICAL BONE )

1. Stage of hematoma
2. Stage of granulation tissue
3. Stage of callus
4. Stage of remodeling (consolidation)
5. Stage of modeling (remodeling)

1) STAGE OF HAEMATOMA

• It lasts up to 7 days
• Formation of hematoma after the fracture of the bone, between and around the fracture, as blood leaks out through torn vessels in the bone.
• From the fracture ends, the periosteum and local soft tissues are displaced. Because of this, ischemic necrosis of the fracture ends occur over a variable length(usually only a few mm).
• The blood supply in the area is thin, some oocytes die whereas others are stimulated to react afterward by modifying into daughter cells.
• Later, these cells contribute to the healing process.

STAGE OF GRANULATION TISSUE

• It lasts for about 2-3 weeks.
• Daughter cells produce cells in this stage which alters and designs to provide blood vessels, fibroblasts, osteoblasts, etc.
• Collectively they form soft granulation tissue in the spaces between the fractured segments.
• This cellular tissue eventually gives a soft tissue facility to the fracture; without any fundamental rigidity.
• The blood clot gives rise to loose fibrous tissue mesh.
• The loose fibrous mesh helps as a core for the ingrowth of fibroblasts and new capillaries.
• This clot is sequentially eliminated by macrophages, giant cells, and other cells arising in the granulation tissue.
• Granulation tissue further differentiates to create osteoblast then finally form bone.

STAGE OF CALLUS

• Last for about 4-12 weeks.
• The granulation tissue differentiates further and creates osteoblasts. An intercellular matrix becomes impregnated with calcium salts. This results in the formation of woven bone(callus).
• Usually, after 3 weeks of fracture, the callus is the first sign of union visible on X-Ray.
• It gives good strength to the fracture.
• Callus formation- Adults < Children ; Cortical bone < cancellous bone.

STAGE OF REMODELING

• Stage of consolidation.
• Woven bone is substituted by mature bone with a typical lamellar structure.
• It is a slow process and takes 1-4 years.

STAGE OF MODELING

• Stage of remodeling.
• The bone is gradually strengthened in this stage.
• At the endosteal and periosteal surfaces, the sharpening of cortices occurs.
• Weight-bearing stresses and muscle forces of a person when it resumes its activity are the major stimulus to this process which comes from local bone strains.

HEALING OF CANCELLOUS BONE

• Cancellous bones have a large area of contact between trabeculae as the bone is of uniform spongy texture and has no medullary cavity.
• The union can occur right between the bony trabeculae.
• Mature osteoblasts lay down the woven bone in the intracellular matrix and join the two fragments together.

PRIMARY AND SECONDARY BONE HEALING

• In primary fracture healing, bone healing occurs directly without the formation of callus.
• As there is no callus formation, it is difficult to evaluate union on X-Ray.
• Primary fracture healing occurs when edges are touching each other exactly.
• It occurs where the hematoma has been disturbed.

SECONDARY BONE HEALING

• This occurs where the hematoma is not disturbed.
• Healing occurs with callus formation.
• It can be evaluated on X-Ray.
• Eg. Comminuted fracture.
• It occurs in those fractures which operated without disturbing the fracture hematoma.

FACTORS AFFECTING FRACTURE HEALING

1. Age of the patient- Children > Adults > Old
2. Type of bone- Flat and cancellous bones > Tubular and cortical bones
3. The pattern of fracture- Spiral fracture > Oblique fractures
4. Immobilization-  not necessary to immobilize all fractures( fractures of ribs, scapula) they heal itself anyway; some fractures need immobilization and still not heal( fracture of the neck of femur).
5. Compression at fracture sites- it enhances the rate of the union of cancellous bone.
6. Open fracture- they often go into delayed union and non-union.

Hope you all find this helpful for you, if you have any query related to this topic or any other topic then you all are free to contact me via contact us or you can also ask your doubts on the comment box. Thank you! 

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