The Effect of High-power Laser Therapy on Pain, Functional Disability, Range of Motion and Pressure Pain Threshold in Subjects With Radicular Low Back Pain Due to Intervertebral Disc Herniation

Overview

Low back pain is the predominant cause of disability on a global scale. In the year 2015, the worldwide point prevalence of activity-limiting low back pain stood at 7·3%, suggesting that at any given moment, 540 million individuals were afflicted. In that same year, low back pain emerged as the primary cause of involuntary labor leave and premature retirement within Europe. In the United States, 44% of patients have utilized their health insurance for low back pain at least once, and 1 to 2% (approximately 3 million individuals) exhibit symptoms of sciatica as a result of a lumbar intervertebral disc herniation. Given the prevalence of disorders attributable to L4-L5 and L5-S1 intervertebral disc herniation, it is imperative to consider the potential risks associated with both surgical and non-surgical medical interventions, such as corticosteroid injections. Laser therapy emerges as a viable modality within the realm of physical therapy, particularly in the mitigation of inflammation. The modulating effects of laser therapy on inflammation have been documented, with no significant side effects reported thus far. Should the efficacy of laser therapy be substantiated, it could be incorporated into the suite of treatments endorsed by authoritative guidelines pertaining to back pain. Patients afflicted with radicular back pain have been the beneficiaries of assistance from physiotherapists possessing specialized knowledge in effective dosimetry. The objectives of this assistance include the amelioration of pain symptoms, the enhancement of functional indicators, the augmentation of the range of motion, and the modulation of the pressure pain threshold, all without the concern of side effects. Furthermore, adherence to the correct treatment protocol is of paramount importance. The main objective of this study is to evaluate the effect of active high-power laser compared to sham laser on pain, disability, range of motion, and pressure pain threshold in patients with radicular low back pain due to lumbar intervertebral disc herniation.

Risk factors contributing to discopathy disorders encompass repeated asymmetric bending and straightening, which predominantly inflicts damage to the posterolateral portion of the disc. Age constitutes another significant risk factor, with the highest incidence observed between the ages of 30 to 50 due to the watery intervertebral disc. Malignant changes associated with infection, end-plate defect, disease, herniation, genetics, and lifestyle (such as smoking) can lead to a loss of organization of the annulus fibrosus (as seen in myxomatous disease) and a fibrotic nucleus. One of the principal causes of sciatica symptoms is the presence of inflammatory cytokines at the site of the nerve root. These cytokines are released upon damage to the nucleus pulposus, instigating inflammation throughout the surrounding tissues. Given that the majority of disc herniations occur within the canal, inflammation typically affects the nerve roots as well. Mediators such as TNF α, prostaglandin E2, the interleukin group, and phospholipase A2 are implicated in this process." In a study conducted in 1993 by Olmarker et al., an experiment was performed where a fragment of the nucleus was positioned adjacent to a pig's cauda equina nerve, devoid of any mechanical pressure. The conclusion drawn from this experiment was that radicular pain did not originate from a mechanical phenomenon, but rather it led to a reduction in sensation and a decrease in the nerve rate. In a separate group of pigs, a singular mechanical stress was introduced, and the lack of symptoms was subsequently demonstrated. The observations of both localized and extensive hyperalgesia indicate the possibility of pain sensitization. Certain chronic conditions, such as nonspecific shoulder pain, lower back pain, and upper limb disorders, have shown a heightened sensitivity to nerve touch. It has been proposed that this sensitivity of the nerves can be attributed to peripheral sensitization mechanisms, wherein neurogenic inflammation results in the sensitization of neural mechanoreceptors, also known as nervi-nervorum. Furthermore, central sensitization mechanisms may also play a role in nerve sensitization, where non-noxious stimuli from the mechanoreceptors undergo abnormal processing in the central nervous system. "Numerous studies have meticulously examined the available treatments for intervertebral disc lesions, encompassing both invasive and non-invasive approaches. Surgical interventions, a common modality, have been thoroughly evaluated. However, it is essential to note that patients who underwent surgery did not experience significantly greater pain relief or a more expedited return to work after a 4-year period compared to those who did not undergo surgery. Another invasive treatment involves the administration of injectable corticosteroids. A systematic review conducted by Yang et al. in 2020 meticulously compared physiotherapy interventions (excluding laser therapy) with epidural corticosteroid injections. Surprisingly, the long-term effects of epidural corticosteroid injections were found to be no more efficacious than those of physiotherapy treatments. In a 2015 study by Johnson et al., the pivotal role of TNF-α and IL-1β was elucidated. While these mediators are indispensable for normal physiological function, excessive secretion can indeed be detrimental. The study underscored the importance of precisely controlling the timing of inflammatory secretions and preventing an unwarranted surge in mediator levels to enhance the effectiveness of future treatments." In a 2015 guideline study of medical interventions, including medication, researchers found insufficient evidence to either accept or reject the effects of NSAIDs, muscle relaxants, oral corticosteroids, analgesics, and neuromodulators. Similarly, in a 2017 study by Ghaseem et al., although the evidence for laser therapy was limited, the guideline recommended the use of lasers for patients with low back pain. A study conducted by Maher et al. in 2004 examined the effectiveness of various physiotherapy treatments in systematic studies. Among these treatments, exercise therapy, laser therapy, and manual therapy were the most effective. However, treatments such as hydrotherapy, traction, magnet, and TENS lacked sufficient evidence. Recent studies by Alayat et al. in 2014 did not accept laser therapy as a standalone treatment; its effectiveness has been described only in combination with other physiotherapy treatments. "Laser, an acronym for Light Amplification by Stimulated Emission of Radiation, possesses three distinct characteristics in the realm of light: 1) Monochromaticity, 2) Coherence (identical phase), and 3) Collimation (high convergence). In this methodology, light energy is projected onto the tissues of the body and absorbed, thereby stimulating or inhibiting enzymatic activity at the cellular level. This instigates physiological reactions, as well as anti-inflammatory and analgesic processes. Laser therapy promotes interactions between the nucleus and the cytoplasm by augmenting physiological activity within the cell. Near-infrared wavelengths enhance the production of Adenosine Triphosphate (ATP) and alleviate pain and edema by stimulating Cytochrome c oxidase (CcO) at the mitochondrial level. Post-laser irradiation in tissues, there is an observed increase in the levels of beta-endorphins and morphine-mimetic substances, which are natural analgesics produced by the body. Furthermore, laser irradiation augments lymph flow, decreases prostaglandin synthesis, mitigates the severity of inflammation, and expedites wound healing by enhancing growth factors and phagocytosis, increasing cytokine secretion, promoting angiogenesis, and stimulating fibroblasts and keratinocytes. Therapeutic lasers, exhibiting a photobiomodulation effect and utilized for pain reduction, are categorized into two types: Low-Level Laser Therapy (power ranging from 5 to 500 mW) and High-Intensity Laser Therapy (power exceeding 500 mW). Laser power is defined as energy per unit time, hence, the use of a high-power laser enables energy to reach the target tissue in a shorter span of time, rendering it more suitable for the treatment of larger areas. According to the Arendt-Schulz law, a physiological response is elicited in the target tissue once sufficient energy has been delivered to it. In this context, the parameters of the laser and its therapeutic capabilities are of paramount importance." The objective of this study was to ascertain the impact of high-intensity lasers on patients suffering from lower back pain, accompanied by radicular pain in a lower limb, a condition attributed to intervertebral disc herniation. Existing evidence implies that the chronic stage of intervertebral disc herniation may involve inflammatory factors, which could be a primary cause of lower back pain with radicular pain. Given its anti-inflammatory properties and absence of side effects for the patient, the high-power laser could serve as an effective treatment modality in the realm of physiotherapy for patients experiencing radicular lower back pain. This, however, is contingent on the physiotherapist's understanding of dosimetry and the aim of specific dosing therapy. Conversely, the dearth of current research on high-intensity lasers and their impact on lower back pain resulting from intervertebral disc herniation, coupled with diffuse pain in the lower extremities, and the absence of an appropriate treatment protocol, such as the application of high-intensity lasers on pain propagation and proper dosimetry with clinical symptoms, led us to identify a need for community therapy in this study. The rationale behind selecting exercise therapy as a standard treatment for both groups was the advantageous effects of laser therapy when used in conjunction with exercise therapy. Current studies on the influence of motor control exercises on disc health and on patients with disc herniation suggest that this type of intervention surpasses other exercises (such as strengthening/resistance exercises, cardiovascular, etc.) and other conventional interventions (such as TENS). The treatment plan for patients with disc herniation can have a positive impact on the process of enhancing the reabsorption of herniated disc contents, disc height, disc diffusion rate, and the improvement of radicular symptoms.