Recovery rates differ significantly across patients and in some circumstances recovery from injury can be hindered by individual, physical or psychosocial factors. These factors are important clinical considerations as they impact conservative management of injuries and prognosis.
To understand how recovery rates can be hindered, we first must understand the physiological processes of tissue injury and healing. Tissue injury follows three phases with some degree of overlap:
1. Inflammatory phase
Blood vessels widen in response to tissue injury and if damaged blood pools into tissue causing bruising. Blood and fluid leak out of blood vessels into the injured tissues. Lymphatic vessels are compromised causing redness, swelling and heat in injured tissues. This phase lasts 24-48 hours, but can persist for up to 2 weeks.
2. Proliferation phase
Tissues begin to regenerate as the body forms a permeable barrier, reinstates blood supply and supports the injured tissue. The formation of new blood vessels causes a surge of blood and important proteins and chemicals for tissue healing. At 3-5 days after injury, specialised cells responsible for producing collagen, elastin migrate to injured tissue to restore the shrinking wound. This phase typically continues for 2 weeks.
3. Remodelling phase
Tissue remodels as clots formed in the inflammatory phase are replaced with specialised functional tissues and Type 1 collagenous scar tissue. After approximately 1 month, the closing of the wound prompts the breakdown of Type 1 collagen, which is then replaced with stronger Type 3 collagen. At this stage, collagen is at 40% of its original strength and after 1 year is reaches approximately 70%.
Factors affecting recovery
These factors can be divided into individual, physical and psychosocial factors.
- Severity of tissue injury: a full grade 3 strain of a muscle will take longer to recover than a simpler grade 1 strain.
- Timeframe: acute (sudden) injuries tend to heal more effectively, while chronic (longstanding) injuries can persist.
- Recurring injuries: repeated injury to the same tissue reduces its ability to recover and tissue is replaced with less functional and supportive tissue.
- Age: patients over the age of 60 have a reduced rate of tissue recovery.
- Cigarette smoking and alcoholism: patients who smoke and excessively drink alcohol have a reduced rate of tissue healing.
- Medical or pre-existing conditions: patients who are immunosuppressed (i.e., cancer patients) or have autoimmune conditions (e.g., diabetes) experience reduced rates of tissue recovery.
- Drugs: prolonged use of corticosteroids suppresses the function of specialised cells that aim to recover injuries.
- Infections: such as bacterial infections that inhabit an open, uncleaned wound colonise and contaminate injured tissue.
2. Physical factors:
- Inactivity and obesity: increases the risk of tissue injury and also hinders the healing process.
3. Psychosocial factors:
- Stress, anxiety and depression: deregulates the immune system, which in turn delays and reduces tissue healing. Prolonged stress, anxiety and depression can also lead to chronic pain.
These factors determine not only your prognosis, but also direct conservative management. In most circumstances, tissue injury is minor and resolves relatively well, even with minimal intervention. However, in other cases, particularly where there is a combination of factors, tissue injury is compromised and may persist. It is clinically important to identify these factors and reduce their effect on tissue healing.