Objective: To compare the benefits, with regard to low back pain (LBP) symptoms, of a thermal cure and a dry rehabilitation treatment.

Methods: Randomized therapeutic trial including patients with LBP, randomly divided into two groups. Thermal cure consisted of underwater shower, massage-jet showers, hydro-massage, pool rehabilitation and peloid therapy. Dry rehabilitation consisted of analgesic physiotherapy, muscle strengthening and group physical rehabilitation. The primary endpoint was based on the Visual Analog Scale (VAS) of pain at day 18 (Day 18). The other outcome measures were the Oswestry Disability Index (ODI), the Short Form-36 (SF36) questionnaire and spine mobility. Follow-up was carried out for 12 months.

Low back pain (LBP) is a very common pathology affecting more than 80% of the population. The pain and the limitation of movements cause significant functional discomfort, resulting in some form of disability and an added handicap. It therefore constitutes a major public health problem due to its impact on the quality of life and its high socio-economic cost.

The medical care for LBP aims to reduce pain and thus improve the functional capacities of patients. Among non-drug adjuvant treatments, the role of thermal cure is far from clear. Indeed, even if the use of thermo-mineral waters for therapeutic purposes is a very old and widespread practice in rheumatology, the study of the efficiency of thermal cures in the treatment of LBP, in particular compared to dry rehabilitation, has been the subject of only a limited number of medical publications. In Tunisia, the Tunisian Hydrotherapy Office estimates that at the end of 2017 the number of spa guests reached 51,324 for all the thermal resorts. However, there are no studies evaluating the effectiveness of such treatments.

We report the results of a randomized therapeutic trial, carried out with the aim of comparing the clinical effects of thermal cures and dry rehabilitation on common LBP.

Patient selection The selection of patients to be referred to the thermal center was made among patients treated in the rheumatology department of the Mongi Slim Hospital; a university hospital center located in La Marsa and not related to the thermal center. The inclusion visit allowed the investigating doctors to collect demographic data and clinical history, in order to verify the inclusion criteria and to have the informed consent signed in French or in Arabic depending on patients' choice.

Randomization The choice of the type of treatment to be delivered was determined by means of randomization provided by the senior investigator in accordance with the Zelen method. Neither the doctors participating in the study nor the patients were informed beforehand of the type of treatment that will be delivered, thermal cure (group 1) or dry rehabilitation (group 2). Each group of patients was unaware of the existence of the other group and its type of treatment.

To calculate the number of subjects required in a group, we set alpha risk at 0.05, beta risk at 0.2 and the minimum difference of pain VAS to be highlighted between the 2 groups at 20 out of 100.

To generate the randomization sequence, we randomly established a list of numbers using the EpiTable program in Epi Info (6.04d version), assigning treatment 1 to odd numbers and treatment 2 to even numbers. The number of patients was balanced after each 20-number sequence. Two groups of 37 patients each were formed. The patients were divided into 4 contingents.

Study protocol The thermal treatment and physical rehabilitation therapy were administered at the same spa center of Jbal EL Ouest, situated to the west of the city of Zaghouan, 50 km from Tunis. Patients were accommodated in the care center for 18 days. Treatments were delivered in the morning on a daily basis, except on Sundays. The thermal treatment used hot, chlorinated and sodium water. Every day, the patients received 4 out of the 5 following treatments: underwater showers (15 minutes), shower-massage (10 minutes), hydromassage (20 minutes), swimming pool rehabilitation (20 minutes) and application of heated peloid (15 minutes). The physical rehabilitation treatment was delivered in dry and included an analgesic physiotherapy based on electrotherapy (30 minutes) and muscle strengthening, as well as group rehabilitation.

Monitoring of care progress, compliance and tolerance during the treatment was carried out by the thermal center doctor.

Inclusion Criteria:

• Patients with low back pain (LBP) evolving for more than 12 weeks.
• Visual analog scale (VAS) of pain greater than 30.

Exclusion Criteria:

• Patients with a loss of autonomy or with impaired intellectual abilities
• Patients with contraindications to a thermal cure (infectious or progressive inflammatory pathologies, unbalanced blood hypertension, decompensated heart disease, respiratory failure, decompensated neurological or psychiatric illness, age greater than 75 years, pregnancy, purulent skin lesions).
• Patients having undergone an epidural infiltration (within 3 months) or spinal surgery (within 1 year)
• Patients who received physical rehabilitation or balneotherapy during the year preceding inclusion, and finally patients using stage 3 analgesics (World Health Organization classification).

Neither the doctors participating in the study nor the patients were informed beforehand of the type of treatment that will be delivered, thermal cure (group 1) or dry rehabilitation (group 2).

Each group of patients was unaware of the existence of the other group and its type of treatment.