Effects of Hydrotherapy on Neuropathic Pain and Pain Catastrophization in Spinal Cord Injury: Study Protocol for a Randomized Controlled Trial

Spinal Cord Injury (SCI) is a spinal cord injury of traumatic origin with its main etiology being violence, which constitutes one of the greatest social and health problems worldwide. One of the complications with the greatest impact in people with SCI is Neuropathic Pain (NP). Pain, mainly chronic pain, has an effect on emotional states, cognition regarding pain and anticipation which leads to the catastrophization of the pain. This form of pain is related to chronic diseases that develop with pain of poor prognosis and are detrimental to quality of life therefore having enormous impacts on health systems. The physiological mechanisms of Hydrotherapy on pain are clear and there is evidence of its use in the management of painful syndromes of difficult treatments such as that for fibromyalgia and chronic lumbar pain, as well as its positive effect on pain perception. However, the effects of hydrotherapy on the NP of patients with SCI are unknown.

Randomized, controlled clinical trial of parallel groups. A randomized sequence will be carried out in balanced blocks to assign the intervention (Hydrotherapy) or the control (Standard Physical Therapy), to a sample of 28 participants, 14 for each group. Each of the interventions (hydrotherapy and physical therapy) will last 9 weeks, for a total of 18 sessions (2 weekly sessions). Two measurements will be made, baseline (pre-intervention) and a second time one month after the end of the intervention. The validated Spanish scales will be used: NP-4 (NP Screening), Numerical Pain Scale (END), PCS (Pain Catastrophization), SF-36 (Health-related quality of life) and WHODAS 2.0 (Disability). The primary outcome is the level of NP and its catastrophization, and the secondary outcomes are level of disability and quality of life. With 28 participants fully measured, it is possible to have 80% power to find differences between the groups with respect to the primary outcomes. All information will be analyzed using average comparisons with 95% confidence. The analysis will be carried out by Intention to Treat (ITT) taking all the randomized participants. Missing data will be processed through multiple imputation chains. Generalized mixed linear models will be used comparing the standardized baseline and post-intervention averages of each group and between each group, obtaining 95% confidence intervals and p-values. Subgroup analysis will be performed adjusting confounders and interactions. A significant difference will be considered when the value of p is less than 0.05. Cohen´s D will be calculated to identify the size of the intervention effect.

Discussion: The results will reflect the effect of the hydrotherapy on NP in patients with SCI. They will also permit the identification of potential changes in functionality levels or quality of life in the intervened population.