Healing of Injury

Healing of Injury

Healing of an injury consists of a number of overlapping phases that are generally recognised and can generally be applied to most tissues. Inflammation is a protective response that permits the body to rid itself of injurious agents, damaged cells and to repair tissues.

Basic normal steps of inflammation and repair:
Injury (eg trauma, infection)  acute inflammatory response (vasoconstriction  vasodilatation  formation of clot  phagocytosis)  proliferative and remodelling response (epithelisation  collagen production  contracture of wound  neovascularisation)  maturation phase (balance between collagen synthesis and lysis  collagen fibre orientation)  healed injury

The acute inflammatory response:
• occurs 0 to 72 hours after injury – begins after any disruption of the normal physiology of the tissues
• injury  cell necrosis; small capillary rupture  haemorrhage into tissues; capillaries then vasoconstrict after 5 – 10 minutes  then vasodilate  leakage of fluid
• platelets adhere to site of damage in capillaries
• fibrin and other clotting factors  block damaged capillaires and lymphatics (this ‘mesh’ blocks further drainage from injury site)
• classic signs of inflammation – pain, redness, swelling and heat
• chemical mediators are released – histamine (vasodilaion), serotonin ( increases capillary membrane permeability), heparin ( prevents occlusion of blood flow in capillaries), neutophil chemotactic factor ( attracts neutraophils), kinins ( increases capillary permeability), prostaglandins ( vasodilate and increased capillary permeability), leukotrienes ( attracts neutrophils), complement ( facilitate all aspects of acute inflammation)

Matrix and cellular proliferation phase:
• occurs 72 hours to 6+ weeks post initial injury – new tissue growth occurs
• macrophages predominate
• proliferation of capillaries and fibroblasts  synthesise collagen (initially type III) and proteoglycan matrix
• new vascular tissue (neovascularisation) occur by budding from capillaries (under control of growth factors)

Remodelling and maturation phase:
• occurs about 6 weeks to several months
• myofibroblasts interact with collagen  contraction of collagen  reorientate in direction of loading/stress
• decrease in capillaries
• Type I collagen fibres produced (stronger than type III)

Chronic inflammation:
• acute inflammatory response usually resolves in 3 – 10 days, if not  chronic inflammation
• chronic inflammation due to:
• infection
• granulomatous (eg tuberculosis)
• autoimmune inflammatory response (eg rheumatoid arthritis)
• constant irritation with mechanical stress

Time required for healing :
Generally:
Muscles – 6 weeks
Tendons and ligaments – 12 weeks
Bone and joints – 6 – 12 weeks

We have not yet got to this page to finish it yet. We will eventually. Please contact us if you have something to contribute to it or sign up for our newsletter or like us on Facebook and Instagram or follow us on Twitter.

Page last updated: @ 1:18 am