ELECTROTHERAPY BLEEDING INFLAMMATION PROLIFERATION

ate treatment dose, with optimal treatment parameters (intensity, pulsing and time), the benefit of US is to make as efficient as pos- sible the earliest repair phase, and thus have a promotional effect on the whole healing cascade. For tissues in which there is an inflammatory reaction, but in which there is no ‘repair’ to be achieved, the benefit of ultrasound is to promote the normal reso- lution of the inflammatory events, and hence resolve the ‘problem’. This will of course be most effectively achieved in the tissues that preferentially absorb ultrasound ie. the dense collagenous tissues.

REMODELLING hours days weeks months

Figure 2: Enhancement of the inflammatory phase of repair in order to facilitate tissue repair

Many papers have concentrated on the thermal effectiveness of ultrasound, and much as it can be used effectively in this way when an appropriate dose is selected (continuous mode >0.5 W cm2

), the

focus of this paper will be on the non thermal effects on tissue repair and recovery from injury.

It is too simplistic to assume that with a particular treatment application there will either be thermal or non thermal effects. It is almost inevitable that both will occur, but it is reasonable to argue that the dominant effect will be influenced by treatment parameters, especially the mode of application ie. pulsed or continuous. Baker et al (9) have argued the scientific basis for this issue coherently.

Influence of ultrasound in soft tissue healing The effect of US during the repair process varies according to the primary events that are occurring in the tissues. During the inflammatory phase, US has a stimulating effect on the mast cells, platelets, white cells with phagocytic roles and the macrophages. By increasing the activity of these cells, the overall influence of therapeutic US is certainly pro-inflammatory rather than anti- inflammatory. The benefit of this mode of action is not to ‘increase’ the inflammatory response as such (though if applied with too greater intensity at this stage, it is a possible outcome) but rather to act as an ‘inflammatory optimiser’. The inflammato- ry response is essential to the effective repair of tissue, and the more efficiently the process can complete, the more effectively the tissue can progress to the next phase (proliferation) as illustrated in Figure 2.

Studies which have tried to demonstrate the anti-inflammatory effect of ultrasound have failed to do so (10), and have suggested that US is ineffective. It is effective at promoting the normality of the inflammatory events, and as such has a therapeutic value in promoting the overall repair events (11). Employed at an appropri-

During the proliferative phase (scar production) US also has a stim- ulative effect (cellular up regulation), though the primary active targets are now the fibroblasts, endothelial cells and myofibrob- lasts. These are all cells that are normally active during scar pro- duction and US is therefore pro-proliferative in the same way that it is pro-inflammatory - it does not change the normal events, but maximises their efficiency - producing the required scar tissue in an optimal fashion.

Research has demonstrated that low dose pulsed ultrasound increases protein synthesis and several research groups have demonstrated enhanced fibroplasia and collagen synthesis (12,13). Recent and growing evidence suggests that US also stimulates angiogenic effects.

The application of therapeutic ultrasound can influence the remod- elling of the scar tissue in that it appears to be capable of enhanc- ing the appropriate orientation of the newly formed collagen fibres and also to the collagen profile change from mainly Type III to a more dominant Type I construction, thus increasing tensile strength and enhancing scar mobility. Ultrasound applied to tissues enhances the functional capacity of the scar tissues. The role of ultrasound in this phase may also have the capacity to influence collagen fibre orientation.

Recent papers have identified the potential role for therapeutic ultrasound in relation to their capacity to influence various cytokines and mediators of the repair process. It is anticipated that this research area will grow significantly in the near future.

The application of ultrasound during the inflammatory, proliferative and repair phases therefore appears to be of value because it has the capacity to stimulate or enhance the normal tissue healing events and thus increase the efficiency of the repair phases. It would appear that if a tissue is repairing in a compromised or inhib- ited fashion, the application of therapeutic ultrasound at an appro- priate dose will enhance this activity. If the tissue is healing ‘nor- mally’, the application will, it would appear, speed the process and thus enable the tissue to reach its endpoint faster than would oth- erwise be the case. The effective application of ultrasound to achieve these aims is dose dependent.

Pulsed shortwave and laser therapy The effects of pulsed shortwave therapy and laser therapy in rela- tion to tissue repair are very similar to those identified for ultra- sound and a summary is included below. The question comes with

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