Soft Tissue Injury

Soft tissue injury

When injury or trauma occurs producing forces necessary to damage soft tissues it is important to consider what happens to these tissues at a cellular level. The secondary injury model described by Merrick (2002) considers there to be two stages following tissue injury, namely the primary and secondary injury response:

• the primary injury is considered to be the damage to cells caused by the direct injury mechanism, be that a crush, contusion or strain force. The cells damaged by this mechanical force may have their cell membranes disrupted causing a loss in homeostasis and subsequent cell death. Many types of tissue may be involved, including ligament, tendon, muscle, nerve and connective tissues;

• secondary injury is thought to be caused by physiological responses to the initial primary injury. This occurs to tissues at the periphery of the injury to those cells not damaged by the primary injury. It is hypothesised that this damage may occur by two means. These are hypoxic (or maybe better described as ischaemic) and enzymatic mechanisms.

Ischaemic mechanisms

There are several proposed causes of ischaemia (reduced blood flow) to the damaged tissue, including haemorrhaging from blood vessels, increased blood viscosity secondary to inflammatory responses and increased extravascular pressure secondary to oedema. This reduced, or absent, blood supply will deprive cells which may have survived the primary injury of vital oxygen causing them to rely on the anaerobic energy systems which only have a short timescale (possibly up to six hours). If the ischaemia prolongs, many of these cells will subsequently die.

Enzymatic mechanisms

The lysosomes of those cells destroyed or damaged in the primary stage will produce enzymes that may damage and destroy neighbouring cells. This often occurs as a result of damage to the cell membrane, which causes the cells to swell and eventually die.

PHASE 1: BLEEDING (0–10 HOURS)

This is a relatively short phase that will depend upon the initial injury type, the tissues damaged and the severity of injury. If there has been an injury to soft tissues some degree of bleeding will occur. When capillaries and small blood vessels sustain primary injury, blood will escape into surrounding tissues and, depending on the location, may gradually track distally as a result of gravity. The type of tissue involved and the type of injury will determine the degree of bleeding in terms of amount and duration.

If very vascular tissue is damaged (e.g. muscle) a larger amount of bleeding will occur in comparison with less vascular tissues, for example ligament and tendon. The bleeding phase may only last a period of a few minutes or hours, but in large muscle contusion injuries, for example, bleeding may continue to a small degree for up to 24 hours (Watson 2004).

PHASE 2: INFLAMMATION (0–4 DAYS)

Inflammation is a complex biochemical and cellular process which is still not fully understood. It can be triggered by many factors other than injury, such as infection and pathology. Following an injury or pathological process there is an immediate inflammatory response. Scott et al. (2004) describe inflammation as a complex process that can be viewed at four levels: clinical, physiological, cellular and molecular, and suggest that it is the application of clinical reasoning skills that allows us to define which level is relevant in any given situation.

PHYSIOTHERAPY INTERVENTIONS

IN PHASES 1 AND 2 (0–72 HOURS POST-INJURY)

When considering the physiotherapy approaches that we can employ at these early stages of tissue injury, we must consider the physiological processes occurring and the aims and physiological responses to treatment.

When treating any patient with an acute injury, for example a ligament sprain or a muscle contusion, the aims of treatment must be decided in specific relation to the individual, in order to plan treatment accordingly.

General physiotherapy aims of early phase management (phases 1 and 2)

The aims are:

• to reduce pain;

• to limit and reduce inflammatory exudates;

• to reduce metabolic demands of tissue;

• to protect newly damaged tissue from further injury;

• to protect the newly-forming tissue from disruption;

• to promote new tissue growth and fibre realignment;

• to maintain general levels of cardiovascular and musculoskeletal fitness/activity.

The PRICE principles

PRICE is a mnemonic for the principal interventions commonly used in the immediate early stages following tissue injury. PRICE stands for :

• protection;

• rest;

• ice;

• compression;

• elevation.

These interventions together are applied in principle to address the seven aims of early phase tissue injury and healing management. These interventions are discussed below. The reader is also referred to the guidelines written in conjunction with the Association of Chartered Physiotherapists in Sports Medicine (ACPSM), on the immediate management of soft tissue injury using the PRICE principles.