The process of muscle-tendinous repair
The process of muscle-tendinous repair
Healing is a general term for the processes involved in replacement of dead and injured tissue by healthy tissue. The process of healing from injury or infection is extremely complex it requires the highly coordinated interaction of vascular, cellular, and chemical components to come to a successful resolution. The healing process that follows depends on the extent of the injury and the approximation of the wounds site's stump ends. Two types of tissue healing, primary and secondary intention. Healing by primary intention is whereby the separation of tissue is small and a line of cells binds the ends together. This type of healing arises in minor wounds. Healing by secondary intention arise in more severe wounds whereby the stump ends are further apart and cannot be bridged, the wounds heal by producing tissue from the bottom and sides of the wound to fill in the space around the wound. This may occur in second degree sprains where ligament tissue is torn and not surgically repaired; healing by secondary intention usually takes longer and results in larger scars. The difference between the two are Primary healing creates a minimal scar and occurs when the damaged edges of a wound are close to each other, whereas secondary healing produces a greater scar because the wound must heal by filling in tissue from the bottom and the sides of the wound.
Healing is a continuum of changing events. There are four phases designated by researchers and clinicians: bleeding, inflammation, proliferation and remodelling. There is an overlap of phases as the injury site heals, as the body steadily accomplishes the tasks in one phase the next phase evolves.
First phase is bleeding, when soft tissue is injured, blood vessels are usually damaged. Blood accumulates around damaged tissue and compresses adjoining tissues, which causes further tissue damage. Every effort should be made to reduce bleeding at the site of the injury. There are four methods that are appropriate in achieving this: rest, ice, compression and elevation.
Rest and compression following injury decrease bleeding and swelling. Ice, used immediately after injury, it is used to reduce tissue metabolism. Elevation reduces blood flow to area.
Second phase is the Inflammation phase; damaged cells release their chemicals, causing vasoconstriction and dilation, the intake of fluid between cells and the attraction of platelets and fast-moving white blood cells. Without inflammation body is unable to complete the healing process which would leave the wound unhealed. Series of events occur in this phase, there are two essential elements to the inflammatory events: Cellular events and Chemical Reactions. Common signs of inflammation include heat and redness, caused by leakage of fluid, cells and chemicals in the area. Swelling, pain and loss of function.
When an injury occurs, blood lymph vessel walls suffer damage. The local vasoconstriction that occurs in the small vessels is followed quickly by vasodilatation. Vasodilatation causes the blood and blood products into the injured site. Chemicals are released and other cells are attracted to the area. Platelets release phospholipids which stop the bleeding. Platelets bind to the collagen fiber stumps that were exposed by the injury.
"Platelets release other important substances such as fibronectin, growth factors and fibrinogen"
These are important in healing process. Fibronectin binds together fibrin and collagen witch form a lattice like complex and act like a plug witch stops the bleeding. This is temporary and fragile, but in early hours provides tensile strength. As healing progresses this plug is replaced by type III collagen. Later on area becomes stable, releasing fibrinolysin witch is an enzyme that allows draining of the excess fluid. First few hours, the body attempts to remove debris from the site by neutrophils (white blood cells), but presence is short lived they are replaced by monocytes and macrophages witch act as phagocytes to remove debris and dead tissue from the area.
Vascular permeability allows cells and chemicals that are in the blood stream to enter the injury site and perform their functions to heal the tissue. Histamine is released by cells that enter the area. Histamine a local hormone, whose function of vascular permeability is continued by serotonin and kinins that also enter the body. As healing progresses both seem to stimulate repair of the damaged area and stimulates the next stage of repair which is proliferation.
Occasionally the inflammatory process is not wholly successful. Pathogens are not removed from the body, the immune system continually attacks some type of tissue, or musculoskeletal structures never fully regain full function and the site is unable to proceed from the inflammatory phase to the proliferationphase. When this happens, the result is called chronic inflammation.
The third phase is the Proliferation phase where the goal is to dispose of dead tissue, mobilize fibroblasts and restore circulation. Once the macrophages have removed debris from the area, the next step in the healing process is the development and growth of new blood vessels and granulation tissue. This transition from debridement to angiogenesis and granulation tissue formation is the beginning of the proliferation phase. Angiogenesis occurs at a fast rate at this phase. Cells responsible for production of this new growth are fibroplasts. Other activities that indicate that the injury has started transition into the next phase include increased extracellular collagen production, increased proteoglycans and epithelial cell mitosis. Factors such as the size, site and type of tissue involved can affect the duration, Peacock 1984 states
"Generally, the phase is thought to last two to four weeks ".
Migration of fibroplasts is primarily responsible for the development of new capillaries and the extra cellular matrix. Fibroplasts release substances which include collagen, proteoglycans and elastin which are needed for scar tissue formation and proliferation. Fibroplasts lay down collagen and aid in new capillary growth.
Type III collagen is produced in the early days of healing it is weak and thin. By day seven there is a relevant amount of collagen by day twelve the immature type III collagen begins to be replaced by stronger type I collagen which adds strength to the site while this is going on hydraulic acid draws water into the area which allow additional room for the proliferating fibroplasts in the wound site.
The healing process now evolves to the final and longest phase of remodelling.
"This phase is generally thought to be about 12 month long, but may range from six months to eighteen months"
(Connolly 1988).Activity that continues into the remodelling phase is collagen transmission. As type I collagen is synthesised, type III is destroyed. As there is more Type I collagen, it becomes more insoluble and less resistant to damage. This strengthens the scars structure. The area becomes more stable and more permanent in its cellular and structural arrangement. The large number of capillaries that were needed to promote tissue growth is no longer needed and begins to recede.
Collagen strength is enhanced by the arrangement of collagen fibers. When collagen fibers are aligned in an organised manner, collagen can form the greatest number of cross links and therefore have optimal strength.
Visible changes can also been seen. These include the loss of the scars red colour. Swelling is diminished and wound sensitivity is also lessened.
There are a variety of factors that will affect regeneration and repair. The size of the wound, the greater the injury, the more time is needed for healing to occur. The bigger the damage of tissue and separation of tissue ends, more time is needed for the body to debride the area and connect the stump ends. The greater the injury the greater the scar tissue. Scar tissue can slow down rehabilitation and depending on where the scar tissue is .An infected wound or tissue will take longer to heal. If dead tissue is present, this needs to be removed surgically or naturally by phagocytosis such as macrophages, neutrophils before healing can be completed. Many modern therapeutic treatments may adversely affect a particular stage of the healing process, such as steroids, these inhibit the growth of new blood vessels and many macrophage functions. Immunosuppressive drugs will prevent the natural immune response involved in healing. Radiotherapy also destroys cells actively dividing. Age can be a factor that changes healing. A good blood supply is needed for any injury to heal properly. A poor blood supply delays or stop an injury from healing properly. Poor cardiac function with generalised, severe atherosclerosis leads to an inadequate blood supply to wounded tissues. Blood supply is often impaired with age. Many systematic diseases have secondary effects that adversely affect healing and repair such as diabetes mellitus, haematological diseases and immunosuppression. A sufficient diet is important to ensure healing processes can occur. Nutrition plays an important in healing, Low Vitamin C, or minerals leads to inadequate collagen formation and poor healing. Excessive movements are more likely to restart inflammation and take longer to repair.
Ligaments, tendons, muscle, bone and cartilage all follow the general healing process, but their healing also has aspects unique to their own cellular make up. Muscle has myogenic cells that are able to regenerate muscle tissue, bone has osteoblasts and tendons have tenocytes.
Methods of therapeutic intervention that could be incorporated into sports therapy clinical practise, promoting repair and recovery include electrical stimulation and thermal modalities such as ice, superficial heat and deep heat.
Cryotherapy (ice) decreases pain, swelling and bleeding,
Electrical stimulation is shown to enhance protein synthesis to promote healing in the first week. Used to relax muscle spasms.
"It also increases the tensile strength of tendons"
After the inflammatory phase heat can be introduced, it can be advantageous, increase circulation to encourage healing and better exchange of nutrients. Ultrasound has the benefit of producing thermal and mechanical effects. Ultrasound is believed to promote collagen, neovascular and myofibroblasts production. It also increases local blood flow, increases extensibility of connective tissue and decreases pain.
Therapeutic drugs are commonly used; the most frequently used of these are the non-steroidal anti-inflammatory drugs (NSAIDs). These reduce the effects of inflammation by altering chemical production or the impact of specific chemicals on the healing process. If administered properly, they can positively reduce the inflammation phase to promote healing.
Therapeutic exercise must be administered carefully without causing harm to the healing tissues if rehabilitation programs are to be successful. It is important to use exercises carefully and watch for adverse effects from the exercise.
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