Fracture healing Flashcards
Compare and contrast cancellous and compact bone
Cancellous bone
- (also known as trabecular bone or medullary sponge)
- Made up of bony trabeculae
- Makes up the epiphysis e.g. of long bones
- Contains red bone marrow
### Compact bone
- Made up of Haversian systems
- Comprises the diaphysis e.g. of long bones, lining the medullary cavity
Both are mature types of bone.
List and describe the two main forms of bone
- Bone exists in 2 main forms
- Lamellar bone: Regular parallel bands of collagen arranged in sheets. Replaces woven bone in development by undergoing remodelling to have collagen fibres in parallel. Lamellar bone is mature bone, and is found in two types: compact and cancellous
- Woven Bone: Immature form with randomly arranged collagen fibres in osteoid. Remodelled to form lamellar bone. Found in
- Foetal bone development. If not foetal, then produced when osteoid is rapidly produced e.g. …
- Healing fracture
- or a developmental disease e.g. Paget’s disease of bone:
Describe endochondral ossification
- Mechanism by which a long bone ^[also found in vertebrae, pelvis] grows in length
- Occurs by bone replacing cartilage
- Osteoblasts line a cartilage precursor
- Chondrocytes hypertrophy, degenerate, and calcify
- Vascular invasion of cartilage occurs followed by ossification
Describe intramembranous ossification
- Direct replacement of primitive mesenchymal by bone
- Found in vault of skull, maxilla, and most of mandible
- Mechanism by which a long bone grows in width
- Osteoblasts differentiate directly from preosteoblasts
- Does NOT involve cartilage ?
Define fractures
A fracture is a break in the continuity of bone.
Fractures can be complete or incomplete. A simple fracture involves a clean break with little damage to surrounding tissues and no break in the overlying skin. If the overlying skin is perforated and there is a wound extending to the fracture site, the fracture is open, and there is a risk of infection
List the types of fractures
- Linear (oblique/transverse) vs Comminuted (complex)
- Complete vs incomplete
- Displaced vs non-displaced
- Open vs Closed
List the three causes of fracture
- Trauma: mechanical force
- Pathological: Bone weakened by another primary process
- Stress
Describe pathologic fractures
A pathologic fracture is any fracture that occurs in diseased bone.
Both neoplastic and non-neoplastic diseases of bone may be responsible.
Pathologic fractures are typically low impact fractures.
Describe stress fractures
Stress Fracture
is a fracture occurring in normal bone that has been subjected to excessive and repetitive trauma resulting in cumulative micro- fractures. Over time, these microfractures exceed the capacity of the normal healing process, resulting in the development of a macroscopic fracture (also known as a fatigue fracture).
Patients are usually long-distance runners, ballet dancers, footballers, and others who undergo regular intensive training. Pain, localized tenderness, and swelling gradually develop; initially, X-rays are normal, but a bone scan or MRI will usually allow diagnosis to be made.
What is a callus?
Defined as a composite mass of tissue that forms at a fracture site to establish continuity at bone ends, which is sometimes felt as a mass.
Calluses may be invisible initially, taking time to become visible on traditional radiographs!
Describe primary fracture healing
Primary Fracture Healing
occurs with anatomic reduction and rigid internal fixation ^[meaning what exactly?]. It is an attempt by the cortex to re-establish new Haversian systems, and thus it has a normal homeostatic bone metabolism.
There is little or no periosteal response and therefore no callus formation - just intramembranous ossification.
Describe secondary fracture healing
- Typical fracture repair model: occurs in a majority of fractures
- Secondary fracture healing involves periosteal reaction ^[note: any injury to bone can cause a non-specific periosteal reaction] and thus callus formation
- Involves both endochondral and intramembranous ossification
- healing is enhanced by movement- and inhibited by rigid fixation
Describe haematoma formation
A haematoma is an an accumulation of blood within the tissues that clots to form a solid swelling. Injury, disease of the blood vessels, or a clotting disorder of the blood are the usual causative factors. ^[OxMed]
Steps of haematoma formation:
- Hematoma forms in medullary cavity and surrounding soft tissue (48-72 hours)
- Bone necrosis and hypoxia stimulate
- Phagocytes and lysosomes (clear debris) -
-
- Forms fibrin mesh to form ‘scaffold’ ^[aka clotting?]
- New capillaries grow from periosteum (7-10 days)
Describe granulation tissue formation
- 2-12 days
- Organization of blood clot
- New capillary formation
- Influx of fibroblasts, mesenchymal stem cells, and macrophages
Describe soft callus and hard callus
- Soft callus
- Influx of fibroblasts and osteoblasts from periosteal layer
- Produce a fibrocartilaginous callus (soft callus)
- Soft callus is formed by an unorganized network of woven bone
- Average lasts for 3 weeks - Hard callus
- Hard callus – a gradual connection of bone filament to the woven bone (Acts like a temporary splint)
- Bone is beginning to strengthen and immobilize
- If proper immobilization does not occur; cartilage will form instead of bone**
