Physical modalities and pain control in rehabilitation: lights and shadows to dispel

In rehabilitation, methods so far proposed for controlling pain are essentially based on drugs, exercise, invasive and minimally invasive treatments, cognitive-behavioural procedures, and physical modalities.^{1, 2} Physical modalities have always been considered part of the DNA of Physical and Rehabilitation Medicine³ and a primary therapeutic element in pain control. Physical modalities, widely used in rehabilitation, are based on a broad range of thermal, electrical, mechanical energies, as well as on other sources of energy as the light itself. All these energies claim some clinical successes in controlling pain.⁴ Several guidelines recommend considering the use of non-pharmacological strategies, as physical modalities, to reduce or eliminate the need for medicines.^{5, 6} However, there is no incontrovertible evidence to support the use of specific physical modalities in the treatment of pain in general, although there is a sufficient theoretical basis for their use in controlling pain almost in any rehabilitation setting.

All of the reviews so far published highlight the difficulty of comparing the research results because of the lack of information about the method used and, in particular, the physical characteristics of the stimulus (e.g. intensity, frequency, duration, time and site of application), or the needed therapeutic dose, also in the most used form of physical energy used, namely electrical currents.⁷

Another critical aspect of the use of physical modalities is the mismatch between the clinical application and the neurophysiological background. A therapeutic approach based on pain mechanisms, as well as on robust clinical reviews, seems to be the only way of ensuring the correct clinical use of all of the possible physical therapies for pain.

This first series of review papers on physical modalities in rehabilitation has been dedicated to some physical energies that have often aroused enthusiasm and some disappointment: localised vibration, LL-LASER and transcranial magnetic stimulation. A narrative review is dedicated to the neurophysiological basis of the analgesic effect of localised vibration encompassing not only the well-established action on the spinal gate but also pinpointing quite interesting and not jet fully explored antinociceptive mechanisms.⁸ A more clinically based literature review is dedicated to the efficacy of low-intensity LASER and photobiomodulation therapy for pain control in some of the most common musculoskeletal conditions.⁹ An emerging role in pain control also in rehabilitation is that of transcranial magnetic stimulation. All the most recent acquisitions in this area are included in the review presented here with a very appealing title. It recalls us to the substantially actual anecdotical reports on the efficacy of physical modalities in controlling pain, and to the need to have sound and proof evidence of their clinical efficacy. In this specific field like never before and in any other physical treatments technical parameters are of paramount importance to activate specific neural pathways.¹⁰

Physical modalities and their technological evolution are advancing rapidly on the better utilization of already established knowledge and pushed further on by the most recent basic science acquisitions. This series of papers aims, at least, to partially fill the gap between basic science knowledge and clinical application of the most relevant physical agents, publishing reviews on both topics.