Phase II: Repair phase

The term repair is synonymous with healing, whereas regeneration refers to the restoration of destroyed or lost tissue. Healing, which extends from the inflammatory phase (48 to 72 hours to approximately 6 weeks), occurs when the area has become clean through the removal of cellular debris, erythrocytes, and the fibrin clot.

Tissue repair is accomplished through three processes: by resolution, in which there is little tissue damage and normal restoration; by the formation of granulation tissue, occurring if resolution is delayed; and by regeneration, the replacement of tissue by the same tissue.  The formation of scar tissue after trauma is a common occurrence; however, because scar tissue is less viable than normal tissue, the less scarring the better. When mature, scar tissue represents tissue that is firm, fibrous, inelastic, and devoid of capillary circulation. The type of scar tissue known as adhesion can complicate the recovery of joint or organ disabilities. Healing by scar tissue begins with an exudate, a fluid with a large content of protein and cellular debris that collects in the area of the injury site. From the exudate, a highly vascular mass develops known as granulation tissue. Infiltrating this mass is a proliferation of immature connective tissue (fibroblasts) and endothelial cells. Gradually the collagen protein substance, stemming from fibroblasts, forms a dense, fibrous scar. Collagenous fibers have the capacity to contract approximately 3 to 14 weeks after an injury and even as long as 6 months afterward in more severe cases.

During this stage, two types of healing occur.

Primary healing, healing by first intention, takes place in an injury that has even and closely opposed edges, such as a cut or incision. With this type of injury, if the edges are held in very close approximation, a minimum of granulation tissue is produced.

Secondary healing, healing by secondary intention, results when there is a gaping lesion and large tissue lo~ leading to replacement by scar tissue. External wounds such as lacerations and internal musculoskeletal injuries commonly heal by secondary intention.

Regeneration

• The ability to regenerate is associated with nutrition, general health of the individual, and, most important, the type of tissue that has been injured.

Repair and regeneration depend on three major factors:

1. elimination of debris

2. the regeneration of endothelial cells

3. the production of fibroblasts, which compose connective tissue throughout the body and form the basis of scar tissue.

Phase Ill: Remodeling phase

Remodeling of the traumatized area overlaps that of repair and regeneration.

1. Normally in acute injuries the first 3 to 6 weeks are characterized by increased production of scar tissue and increased strength of its fibers.

2. Strength of scar tissue continues to increase from 3 months to 2 years after injury.

3. Ligamentous tissue takes as long as 1 year to become completely remodeled. 

• Forces applied to the ligament during rehabilitative exercise will develop strength specifically in the direction that force is applied.

• If too early or excessive strain is placed on the injury, the healing process is extended.

For proper healing of muscles and tendons, there must be careful consideration of when to mobilize the site. Early mobilization can assist in producing a more viable injury site; on the other hand, too long a period of immobilization can delay healing.

Chronic Inflammation

The chronic muscle and joint problem is an ever-present, self-perpetuating concern in sports.

1. If an acute inflammation reaction fails to be resolved in 1 month, it is termed a sub-acute inflammation.

2. If it lasts for months or even years, the condition is termed chronic.

Chronic inflammation result from repeated acute microtraumas and overuse.

1. The primary cells during chronic inflammation are lymphocytes and macrophages (monocytes), in contrast to neutrophils in acute inflammation.
2. It has been suggested that lymphocytes, although not normally phagocytic, may be used to stimulate fibroblasts to heal and to form scar tissue. 
3. Macrophages, present in both acute and chronic inflammation, are definitely phagocytic and actively engaged in repair and healing.

Major chemicals found during chronic inflammation

1. Kinins (especially bradykinin), which also cause vasodilation, increased permeability, and pain.

2. Prostaglandin can also seen in chronic conditions, causes vasodilation. Prostaglandin can be inhibited by aspirin.

Healing of Soft Tissue Types

Cartilage Healing

• Articular cartilage has limited capacity to heal.

• Cartilage in general has little if any direct blood supply.

Ligament Healing

Ligament healing follows the same course of healing as other vascular tissue.

• If proper immediate and follow-up management is done, a sprained ligament will undergo the acute, repair, and remodeling phases in approximately the same time period as other vascular tissues.

• Gradually a scar is formed. In the next months the scar matures along with a realignment of collagen fibers in reaction to joint stress and strains. Full ligament healing with scar maturation may take as long as 12 months.

Skeletal Muscle Healing

Skeletal muscles are unable to undergo the mitotic activity required to replace cells that have been injured. In other words, regeneration of new myofibrils is minimal.

Skeletal muscle healing and repair follow the same process as other soft tissue.

• Collagen fibers mature and become oriented along lines of tensile strength according to Wolff's law.

Nerve Healing

• Because of the special nature of nerve cells, once they die regeneration cannot take place.
• If a nerve fiber is involved rather than the cell, regeneration can take place. The closer the injury is to the cell, the more difficult regeneration becomes.
• For nerve regeneration to occur an optimal environment must be present.

Modifying Soft Tissue Healing

The healing process is unique in each athlete. In addition, different tissues vary in their ability to regenerate.

 Usually connective tissue will readily regenerate, but; as with all tissue, this possibility is dependent on the availability of nutrients.

Age and general nutrition can play a role in healing.

1. The older athlete may be delayed in healing when compared with younger athletes.

2. The injuries of an athlete with a poor nutritional status may heal more slowly than normal.

3. Athletes with certain organic disorders may heal slowly. For example, blood conditions such as anemia and diabetes often inhibit the healing process.

Management Concepts

Many of the current treatment approaches are designed to enhance the healing process. They generally come under the headings of drugs to combat inflammation, thermal agents, physical modalities, mobilization, and exercise rehabilitation.

Drugs to treat inflammation

There is a current trend toward the use of anti-prostaglandin medications, or non-steroidal anti-inflammatory drugs (NSAID's). The intent of this practice is to decrease vasodilation and capillary permeability.

Physical modalities

Both cold and heat are used for different conditions.

1. In general, heat stimulates acute inflammation and cold acts as a depressant.

2. Conversely, in chronic conditions, heat may serve as a depressant.

A number of electrical procedures are increasing in popularity for the treatment of inflammation stemming from sports injuries.

1. penetrating heat devices such as ultrasound therapy

2. electrical stimulation, including transcutaneous electrical nerve stimulation (TENS) and electrical muscle stimulation (EMS).

Exercise rehabilitation

A major aim of soft-tissue rehabilitation through exercise is pain-free movement, full-strength power, and full extensibility of associated muscles.

1. The ligamentous tissue, if related to the injury, should become pain free, have full tensile strength, and full range of motion.

2. The dynamic joint stabilizers should regain full strength and power.

Immobilization of a part after injury or surgery is not always good for all injuries.

• When a part is immobilized over an extended period of time, adverse biochemical changes occur in collagenous tissue.
• Early mobilization used in exercise rehabilitation that is highly controlled may enhance the healing process.