Effectiveness of an Invasive Physical Therapy Protocol in Primary Care Patients With Low Back Pain and Lower Extremity Irradiation. Randomized Controlled Clinical Trial

Low back pain or lumbar pain is the most frequent cause of incapacity for work in Spain, occupying first place among the most common pathologies diagnosed in this country, followed by cervical pain. Non-specific low back pain is the main cause of public spending on health care and labor concepts, with a prevalence of 80%. Furthermore, this pathology represents more than half (52.92%) of the diagnoses of chronic pain that is neither oncologic nor neuropathic. This situation generates high economic, health care and labor costs, representing an equivalent cost of between 1.7% and 2.1% of the Gross Domestic Product.

Low back pain is described as pain located between the lower limit of the ribs and the lower limit of the buttocks, the intensity of which varies according to posture and physical activity, and which is usually accompanied by painful limitation of movement. Approximately 40% of patients with low back pain present irradiation in the lower extremity. The chronification of low back pain can result in central sensitization, causing hypersensitivity to non-painful and painful stimuli even long after the onset of the acute episode of low back pain.

The approach to low back pain offers options such as the administration of drugs, prescription of physical exercise, pain education and modification of patients' habits. Minimally invasive techniques in the management of low back pain are arousing greater interest due to their great advantages. In the field of physical therapy, novel techniques have been developed in recent years, such as ultrasound-guided percutaneous musculoskeletal electrolysis and ultrasound-guided percutaneous neuromodulation, in which different types of electric current are applied through solid needles. Different mechanisms of action have been associated with these invasive techniques, such as a potential effect on the activation of descending pain inhibitory system pathways, the reduction of evoked motor potentials and an increase in intracortical inhibition, suggesting benefits in patients with central sensitization. The invasive techniques of electrolysis and neuromodulation have been applied in other studies at the nervous level, especially in the sciatic nerve at the piriformis and ischiotibial level, in the popliteal fossa and in the foot. It has given good results in lumbar pain. However, there is no study carried out in patients with low back pain and the presence of hernias or protrusions, nor is there any control of the evolution in the medium and long term.

The application of percutaneous neuromodulation has the capacity to modulate neuronal activity in the primary motor cortex, promoting transient and long-term neuroplastic effects. The modulation of this region is related to a decrease in pain due to the relationship with pain processing areas, such as the thalamus, cingulate cortex and periaqueductal gray matter. Electrical stimulation of the peripheral nervous system percutaneously activates a complex neural network that in turn involves a series of neurotransmitters and receptors, such mechanisms being able to promote segmental analgesia and extra-segmental analgesia. Some studies suggest that percutaneous neuromodulation therapy may have a possible beneficial effect in patients with central sensitization, producing improved conditioned pain modulation, reduced motor evoked potential and enhanced intracortical inhibition.

To the authors' knowledge, there are no studies that prove the effectiveness of these invasive techniques in the improvement of neurophysiological parameters in patients with low back pain with irradiation in the lower extremity, presence of hernias and/or protrusions. Taking into account the good empirical results found in private clinics and the precedents of other studies carried out with short-term follow-up in other regions, this treatment approach of outpatient application in primary care centers could mean a discharge of patients who are referred to the hospital for medical care, imaging tests and surgical interventions.