41. Primary and secondary bone healing. Complications of the fractures treatment and therapy. Arthrodesis.

What are the two main types of bone healing?

Direct (primary) and indirect (secondary)

What is required for direct/primary bone healing?

Rigid stabilisation with compression of bone ends (contact healing)

What is the result of rigid stabilisation in primary bone healing?

Suppression of callus formation, direct re-establishment of the cortex

How can different types of primary healing be classified?

1. Gap healing

2. Contact healing

What are the two stages of gap healing (a type of primary bone healing)?

1. Filling of gap (less than 1mm) by direct bone formation, no connective tissue or fibrocartilage w/i gap preceding production of bone.

2. Longitudinal haversian remodelling reconstructs necrotic fracture ends & newly formed bone is resorbed & replaced w/osteons of original orientation

What characterises contact healing (a type of primary bone healing)?

Direct apposition of fragments, osteons grow across the fracture site, parallel to the long axis of the bone

What are the stages of indirect/secondary bone healing?

1. Haematoma and inflammation

2. Reparative phase

3. Bone remodelling

What occurs during the haematoma and inflammation phase of secondary bone healing?

Haematoma formation → attraction of inflammatory cells → swelling, vasodilation

Which inflammatory cells are involved in the haematoma and inflammation phase of bone healing?

Platelets, neutrophils, macrophages & mesenchymal stem cells

What is the role of the haematoma in fracture healing?

Immobilises the fracture site

What are the stages of the reparative phase of bone repair?

1. Soft callus formation

2. Cartilaginous callus

3. Hard callus formation

What occurs during the soft callus formation phase?

Granulation tissue forms a fibrous callus to stabilise the area as inflammation subsides

Which cells are involved in the soft callus phase?

Fibrocytes

What occurs during the cartilaginous callus formation phase?

Fibrous callus undergoes chondrogenesis → cartilage in the intercortical region

Which cells are involved in the cartilaginous callus phase?

Chondrocytes

What occurs during the hard callus formation phase?

Cartilaginous callus ossifies (endochondral ossification) into woven bone → osseous callus forms reinforcing the fracture

Which cells are involved in the hard callus phase?

Osteoblasts, osteoclasts

What occurs during the remodelling phase?

Woven bone is replaced by lamellar bone, excess callus is resorbed to match the original bone structure, restoring function

Which cells are involved in the remodelling phase?

Osteoblasts, osteoclasts & osteocytes

What are examples of complications of fracture treatment and therapy?

1. Delayed union

2. Malunion

3. Non-union

4. Excessive callus formation

5. Fracture disease

6. Pseudoarthrosis

7. Osteomyelitis

8. Others

What is delayed union?

Normal stages of fracture healing occur at a slower rate than normal.

What are some aetiologies of delayed union?

Severe soft tissue damage, poor blood supply, inadequate fixation, periosteal stripping, bone fragment removal.

What are the clinical signs of delayed union?

Pain, instability, lameness, muscle atrophy.

What are the treatment options for delayed union?

Rigid immobilisation, bone grafts, surgery.

What is malunion?

Normal fracture healing stages with malalignment.

What are some aetiologies of malunion?

Inadequate immobilisation, misalignment, premature fixator removal, trauma.

What is non-union?

Failure of a fracture to heal.

What is the aetiology of non-union of bones?

Inadequate immobilisation of fracture ends, resulting in movement of bones or disruption of blood supply

What are the two types of non-union?

Viable (biologically active; hypertrophic) and non-viable (biologically inactive; atrophic).

What characterises hypertrophic non-union?

Excessive fracture mobility with adequate blood supply → Excessive callus formation, "elephant's foot" sign.

What characterises atrophic non-union?

Reabsorption and rounding of bone ends due to inadequate blood supply & excessive mobility of bones.

What are some aetiologies of excessive callus formation?

Movement at the fracture site, infection, periosteal stripping, bone grafts.

What is fracture disease?

Joint stiffness and muscle wastage due to fracture.

What is pseudoarthrosis?

A false joint that forms due to a failure of fracture healing.

What is osteomyelitis?

Inflammation of bone and bone marrow. May result in delayed union or non-union

What are clinical signs of osteomyelitis?

Lameness, inflammation, swelling, redness → necrosis and fistula

What are some treatment options for osteomyelitis?

Drainage, necrotic bone removal, lavage, stabilisation, antibiotics (Amoxicillin/Clavulanate, G+ clindamycin or G- enrofloxacin).

What are some other complications of fracture treatment?

Ossification of stripped periosteum, neoplastic transformation, metallosis.

What is arthrodesis?

Surgical fusion of a joint to form one bone.

What are some indications for arthrodesis?

Dysplasia (e.g., shoulder), palmar/plantar instability.

How is arthrodesis performed?

1. Bone grafts either from a donor or from patients own body is put between two bones being fused, often w/ help of supporting metal implants to hold them together (screws, plates, fixators)

2. After surgery & healing (months to years…), two adjoining bones are fused & no motion takes place between them.

What is the outcome of arthrodesis?

Loss of joint motion, increased stability and weight bearing capacity.

Which joints can arthrodesis be performed on?

Most joints.

What is important for successful arthrodesis?

1. Removal of all cartilage

2. Alignment of joint surfaces.

Which fractures are most likely to become infected?

Open fracture with skin penetration.