Healing And Repair - Fractures Flashcards
What is a fracture
A fracture is present when there is loss of continuity in bone ranging from •multi fragmental •comminuted •hairline •microscopic •close fracture = no open wounds •open fracture = open wounded
Bone and cartilage cells
1)Osteoblasts - produce new bone
2)Osteocytes- maintain the bone (mature bone cells) osteoblasts become trapped in the matrix= osteocytes
Reduced ability to synthesis bone
Routine turn over of matrix
3) Osteoclasts- Remove bone tissue- reabsorb bone
4) Osteoprigenerator cells- periosteum and endosteum- mature to osteoblasts Differentiate into osteoblasts when required I.e fracture
Cartilage cells:
Chondroblasts chondrocytes and chondroclasts
Chondroplasts:
immature cells — Produce extracellular matrix
Chondrocytes:
Mature cells — maintain extracellular matrix
Chondroclasts- absorb cartilage
Fracture healing
Is a specialised type of wound healing involving a regeneration process rather than a repair process
Tissue formed in healing process is the same as the original tissue
Primary fracture healing
Occurs in the presence of rigid fracture fixation i.e. no movement at fracture site
Secondary fracture healing
Indirect bone healing with named stages and use of cartilage model
Occurs when there is a micro movement (stimulates repair process) at the fracture site
More common
Shafts or all long bones
Stages of secondary fracture healing in long bones
1) Haematoma
2) Cellular proliferation/cartilage model formation
3) Callus formation
4) Consolidation of callus
5) Remodelling
1)Haematoma
0-2 weeks
Haematoma occurs almost immediately after trauma occurs
Formation of a blood clot- occurs at time of fracture where there is rupture of localised blood vessels
Blood cells and platlets initiate a sequence of cellular events inflammatory response
Cellular proliferation and cellular differentiation eg osteoblasts and chrondroblasts
Torn blood vessels lead to necrosis bone end
New capillary buds sprout from undamaged vessels and grow towards the fracture site
2)Cellular proliferation and cartridge model formation
0-2 weeks
Cartilage replaces Haematoma
Cellular activity on exterior + interior of bone
Differentiation and proliferation of stem cells into chondroblasts and osteoblasts
Cartlidge laid down by chondroblasts gradually replacing the heamotoma
Chondrocytes proliferate and hypertrophy releasing contents in the extracellular matrix
Cartilage model = gel like fusion between bone ends not solid disrupted by excess movement
3)Callus formation
3-4 weeks UL
6-8 LL
New blood vessels bringing chondroclast and osteoblasts to fracture site
Osteoblasts lay down collagen and mineral salts to form woven bone
Chondroclasts remove Cartlidge model
External and internal bridging callus visible on x-ray
Callus formation contd
6-12 weeks
Periosteum re-formed
Blood clot almost replaced by cellular tissue
Necrotic bone ends reabsorbed
Outcome stage= fracture union
There is some rigidity at the fracture site and movement of the part is allowed
excessive movement gap in bone can delay this process
4)Consolidation of callus
6-8 weeks UL
12- 16 LL
Collagen fibers re-organised along lines of stress
Haversion systems start to reform in compact bone by the process of cutting cones
Outcome of this stage is sufficient bone strength to permit weight-bearing in normal use
5) Remodelling
12 weeks UL
24 weeks LL
strengthening of bone along stress linesI osteoblasts
Surplus bone slowly removed by osteoclasts
Morrow cavity reformed
This stage may last for 18 months to 2 years fixation metalwork remains in situ for this time period
Primary fracture healing process
Occurs when there is a rigid fixation by metalwork
Stem cells differentiate into osteoblasts straightaway to produce new bone not Condrablasts
Cutting cones process occurs at site i.e. osteoclasts tunnel across fracture site followed by information of new blood vessels and osteoblasts producing bone
Direct union without callus formation occurs
Structure and healing of cancellous
Short bone healing etc
Loose meshwork
No haversion system
More straight forward
lined with stem cells- osteoblasts for new bone production
New bone nerve fibres blood supply grow out from each fragment and unite in the middle (direct healing)
Blood vessels and nerves interweave
Process of fracture healing in cancellous bone
1) Haematoma
2) Proliferation of osteogenic cells at fracture surface
3) Intercellular metric slide down by osteoblasts
4) Calcification of matrix
5) Bone strength along lines of stress
