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Bone Healing
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5 Key Points
1. Bone has an inner cancellous layer and an outer cortical layer.
2. Has periosteal, endosteal, epiphyseal and apophyseal blood supply.
3. Healing can be primary (no callus) or secondary (callus formation)
4. Stages are hematoma, inflammation, proliferation, callus, remodel.
5. Complications include non-union, malunion, & delayed union.
Bone Healing Anatomy
Bone is derived from mesenchyme through intramembranous and endochondral ossification to give an outer cortical layer and an inner cancellous layer.
Bone Structure
Bones have an outer cortical layer and an inner cancellous layer. Each structure has a specific purpose, as detailed below:
- Cortical: columnar structure and concentric layers connected by longitudinal Haversian canals (central blood vessel) and transverse Volkmann canals (nutrient vessels).
- Cancellous: loosely woven trabeculae of organic and inorganic bone.
These structures are both used in bone grafting.
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Fun Fact: cartilage is the precursor for bone formation endochondral ossification.
Bone Blood Supply
Bone receives more than one type of blood supply depending on its location and origin/insertions. The important vascular vessels are:
- Periosteal
- Apophyseal
- Endosteal (nutrient supply to the medullary cavity)
- Epiphyseal (growth plates)
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Memory hook for Bone Blood Supply: PEACE
· Periosteal
· Epiphyseal & Endosteal (nutrient supply to the medullary cavity)
· Apophyseal
· Canal of Volkmann (nutrient supply)
· Haversian Canals (central supply)
Types of Bone Healing
The type of bone healing is dependent on the removal of a fracture haematoma and the type of bone fixation performed. Absolute stability results in primary bone healing.
Primary Bone Healing
This occurs when absolute stability is provided to a fracture fixation resulting in no callus formation. Normal bone architecture is restored when osteoclasts provide a guide for blood vessels to cross the fracture site. A clinical example is a compression plate.
Key aspects to this type of bone healing are:
- No callus formation
- No inflammatory or proliferative phases of healing
- Haversian remodelling/osteonal bone remodelling
Secondary Bone Healing
This occurs when absolute stability is not provided to a fracture fixation resulting in callus formation. Clinical examples include K-wires, external fixators, and casting/splinting.
Key aspects to this type of bone healing are:
- Callus formation
- Fracture haematoma occurs
- Bone healing via endochondral ossification
This is different to bone graft incorporation seen in bone grafts.
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Fun Fact: a callus is soft, immature woven bone and hyaline cartilage created by osteoblasts and chondroblasts, respectively. It becomes a hard callus (mature woven bone) when the osteoid is mineralised with hydroxyapatite.
Stages of Bone Healing
There are 5 phases to bone healing: haematoma, inflammation, proliferation, callus formation, and remodelling.
Bone healing is reliant upon osteoblasts and osteocytes. They help form new bone and maintain calcium homeostasis.
The 5 phases of bone healing are as follows:
- Haematoma: a "haematoma" is formed at the fracture site.
- Inflammation: haematoma granulates & osteoclasts remove necrotic bone.
- Proliferation of periosteal and endosteal cells at the cortex.
- Callus formation & transformation from a soft callus (osteoid) to a hard callus.
- Remodelling of woven bone to lamellar bone
There are some similarities to bone and wound healing - but don't get confused!
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Memory Hook for "Bone Cells":
· OsteoBlasts Build bone by producing osteoid.
· OsteoCytes maintain Calcium hemostasis in the bone matrix.
· OsteoCLasts CLean up the bone (bone resorption)
Complications of Bone Healing
Successful bone healing requires several factors to work together. Sometimes this doesn't occur for a variety of reasons. This can lead to some of the following complications
- Malunion
- Non-union
- Delayed union
These complications can be treated by bone grafting.
Flashcards
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Evidence-based flashcards are designed for active recall and spaced repetition of the verified information you are currently studying.
They are continually updated and are for thePlasticsPro users.
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