SUMMARY: Healing is an integrated process with a variety of components that have different time-frames. Repair of injured tissues can be impaired by a wide range of prior or new conditions, both physical and psychological. Chronic pain and incomplete healing are more common in those who are involved in litigation for financial compensation
Delayed or failed healing is a common issue affecting Quantum of Damages in Personal Injury litigation.
Although the processes of, and factors preventing, healing are best researched and documented for wound healing, the general principles are applicable to healing of other injuries, to greater or lesser extent.
Although the process is continuous, different overlapping stages 1 dominate at increasing time-intervals since injury:
Coagulation of the blood starts immediately, is an essential emergency response but by blocking off the smaller blood vessels has the adverse effect of locally compromising blood supply to the injured part.
Inflammation begins shortly after coagulation, lasts from a few days to weeks, is a defence against infections and forms a bridge between tissue injury and growth of new cells.
Within days, the major healing processes begin. Blood cells of various types are attracted to the injured site, multiply and begin defining the ultimate structure of the repaired tissue. The resulting scab forms an infrastructure for the development of the various components of the replacement skin, including a framework in which new blood vessels develop.
Remodelling can take up to a year and includes the formation of scar tissue and the generation of new skin. The fibres that develop haphazardly are aligned into the stress lines of the wound, but do not fully revert to their original "basketweave" organisation, function or strength.
Repair of injured tissues can be impaired by a wide range of prior or new conditions, both physical and psychological.
Factors 1 that interfere with healing may be pre-existing ("thin skull") or a concomitant result of the injury.
Local factors affecting wound healing:
Various growth factors have been identified. Applied to fresh wounds, they can enhance the ultimate function and appearance of the healed tissue. Hitherto, they have proved disappointing when applied to chronic wounds.
It is unclear how edema adversely affects healing, but reducing tissue fluid by raising and/or compressing the affected limb may increase the oxygen supply to the injured part.
Conditions that compromise oxygen supply to the tissues include heart and lung problems, reduced volume of circulating blood, excessive pain, both prescription and recreational drugs 2  that constrict blood-vessels, and hypothermia. Compromised oxygen supply increases susceptibility to infection.
Infection prevention requires an intact immune response of the White Blood Cells (WBC) to the local growth factors and other chemicals that are released by injured tissue, and a sufficient supply of oxygen that is used to form local oxidants, substances that destroy most of the potentially harmful bacteria in the wound.
Regional factors affecting wound healing:
Diffuse diseases of tissues can impair the supply of oxygen, chemicals and blood cells to the injured tissue, and the removal of fluid and "waste products" from the injured part. It is clinically observable that compromised nerve supply reduces and limits healing, though the mechanisms are even less clearly understood.
Systemic factors affecting wound healing:
How well the heart pumps and the lungs oxygenate the blood determines the delivery of nutrients and healing supplies to the area of injury. Similarly, partly at least because of the harmful effects of accumulated waste products, malfunctioning of liver and kidneys can slow and limit the processes of tissue repair.
Malnutrition, to a degree that is uncommonly seen in affluent Western countries, demonstrably inhibits healing. Both chronic infection and more particularly malignant disease compromise the immune response.
We have elsewhere discussed the adverse effect of smoking on healing after plastic surgery in general and mammoplasty in particular.
"Poorly substantiated claims of enthusiastic proponents of the field" have resulted in widespread scepticism.4 Nevertheless, there is a very large and rapidly growing body of evidence on psychological factors in 3 areas: readily measurable physiological effects, biomolecular changes and cellular responses.
For example, stresses such as bereavement and intense examination anxiety have a demonstrable adverse effect on immune functions. In experimental animals, inescapable (but not escapable) electric shocks have been shown to dramatically reduce rates of tumour rejection.
Just as Pavlov's dogs could be conditioned to salivate at the sound of a bell, a conditioning stimulus can be associated with administration of a substance that suppresses the immune response. When conditioning is complete, the stimulus alone triggers immunosuppression in the animal.
We have previously addressed the adverse effects of compensation on healing and the finding that pursuing a claim accounts for about 24% of the development of chronic pain. 5
Chronic pain and incomplete healing are more common in those who are involved in litigation for financial compensation.