principles of bone healing Flashcards
what are the three phases of bone healing?
- inflammatory
- restorative
- remodeling
when damage to a bone occurs what happens to induce the first stage of bone healing?
when damage to bone occurs there is lysis of osteocytes and dead soft tissue cells give off substaces that attract inflammotory celss (incl macrophages) which start to clear away the necrotic tissue - inflammatory stage starts
what is the fisrt step of the inflammatory phase when a frature occurs?
formation of a blood clot at the frature site, occurs within a couple of hours
what cells do the cleaing of the fracture site during the inflammatory phase?
phagocytes and macrophages
what is the importance of the clot formed during the inflammatory phase when a fracture occurs?
has a role in the process of neovascularisation to the fracture site
where can the clot that is formed at a fracture during the inflamatory phase be located?
within the periosteum or broken through the periosteum and around the surrounding tissues if the periosteum is broken
what is
compartment syndrome relating to the clot formed during the inflammatory phase of frature repair and what issue does it cause?
if the periosteum is broken when the clot forms it can invade the surrounding tissues and this can cause a large bleed in the muscle belly spaces which can go unoticed leading to blood loss and hypovolemic shock
what are the subdivisions of the restorative phase?
soft callus formation and hard callus formation
what is the structure of the soft callus like?
hypercellular fibrocartilaginous tissue
what is the function of the soft callus in the restorative phase?
it is elastic, but it starts to stabilise the fracture
how long does the soft callus restorative phase last?
4 day to 3 weeks
what results in the formation of a hard callus?
As the fracture is stabilised and blood supply is restored, the newly formed cartilage is progressively substituted by bone tissue by means of a process endochondral ossification (osteoblasts)
when does the formation of the hard callus begin and end?
begins 2 weeks after fracture and ends 6-12th week
what can interupt the ossification of the callus
movement of the fracture site
what occurs in the remodeling phase?
At the end of the restorative phase the ends of the bones are envoloped by a fusiform mass - callus (like a skin scar). this callus will start to remodel depending on the function of the limb and the way the facture has set (this affects the forces accross the limb)
how long does the remodling phase take?
months to years
in the restorative phase there are two types of healing that can be differentiated what are these and when are they found?
First intention (minimal bone callus formation) - occurs with surgical repair
Second intention (most common natural type of healing)
describe first intention bone healing
Healing by first intention is characterised by the direct formation of bone tissue in a fracture line without the creation or production of bone callus.
what conditions are needed for first intention healing of bones?
- Immediate stabilisation
- Good blood supply
- Perfect reduction of the fracture edges (reducible fracture)
- Absence of micromovements at the level of the fracture line
- Interfragmentary compression (Roux Law)
The patient’s own weight
Application of osteosynthesis systems that compress the fracture lines
Placement of osteosynthesis systems that redistribute the weight - Absence of infection
with first intestion healing of bones what thing needs to be maintained?
the blood supply must not be damaged esp the intraosseous supply
what is the speed of first intention bone healing? what is the down side of this?
The ossification by first intention takes place much faster than by second intention. However, at first, direct osteonal union is not as stable as primary healing with separation (due to the fact there is not a callus formed)
when does second intentionhealing of a bone occur?
- Late treatment
- Deficient reduction of the fracture or loss of fragments (so cant piece all together surgicaly)
- Poor blood supply
- Infection
- Absence of forces of compression
what is this xray an example of?
second intention healing, failed to achive reduction of site or compression
remodling is occuring in the third image and the wires are encased inside the hard callus that had formed
what is this xray and example of?
healing of bone by first intention
in wwhat cells does remodeling occur?
in osteoclasts
