The main objective of this study is to estimate the cost-effectiveness of ozone therapy in patients on the waiting list for surgery due to disc herniation.

A cohort study (patients on the waiting list for surgery due to herniated disc) will be carried out, to which the treatment with ozone will be offered, without giving up the planned surgical intervention.

The main objective of this prospective, post-authorization follow-up study is to estimate the cost-effectiveness of ozone therapy (compared to standard care) in patients with disc herniation waiting for surgery (by microdiscectomy). Besides utilities of patients with disc herniation on a waiting list for surgery will be estimated, social/economic burden of disc herniation will be quantified and a decision aid will be developed and applied.

The main outcome measures are "Direct hospital cost", "Percentage of executed surgeries" and "Change in sciatic pain". In addition, data on health-related quality of life and resource utilization will be collected which will permit to estimate the incremental cost-effectiveness ratio (ICER), comparing incremental costs and quality adjusted life years (QALY).

The variables will be collected at the beginning, on the day of treatment and at 1, 3, 6, 12 and 24 months. The enrollment period will be 24 months. The follow-up period will be 24 months.

The results of the study will allow a better understanding of the value of ozone therapy in the management of patients on the waiting list for herniated disc surgery. In addition, it will contribute to the development of a more patient-centered health system.

Inclusion Criteria:

• Diagnosed with a herniated and not calcified lumbar disc that presents as: not migrated protrusion and/or extrusion.
• Evaluated and diagnosed by the Neurosurgery Department, having been chosen as an appropriate candidate for surgery consisting in discectomy or microdiscectomy, after meeting the following two criteria: 1) Sciatic pain, with a visual analogue scale (VAS) intensity ≥ 5, despite 6 weeks of conservative management, wether it exists lumbar pain or not and 2) Radiating pain that matches the MRI image showing one or more herniated discs (not to be considered those patients with two herniated discs and symptoms attributable to only one of the herniated discs).
• Included in the surgery waiting list for a discectomy or microdiscectomy.
• Patients who have signed and dated the study 's specific informed consent.

Exclusion Criteria:

• Patients who do not meet all the inclusion criteria.
• Calcified and/or migrated herniated disc, and/or with a severe neurological deficits (cauda equine syndrome).
• Herniated disc with surgical indication of laminectomy and/or arthrodesis (massive extrusion, sign of instability or other conditions under the neurosurgeon judgment).
• Relevant clinical paresis that does not improve despite 6 weeks of full conservative management (patients with severe pain and mild paresis that only shows up in the physical exam are not to be excluded, but those who present with paresis as the main symptom -"clinically relevant"- must be).
• Simultaneous symptomatic cervical or dorsal herniated discs.
• Previous lumbar spine surgery.
• Concomitant spine conditions that may be causing symptoms or have indication for surgery (such as fractures or tumors).
• Known allergy to ozone.
• Those who are uncapable to fill in the scales used to measure variables in the study, like the visual analogue scale (VAS), Roland-Morris and SF-12 questionnaires.
• Those who are unable or do not wish to fulfill the study 's protocol (answer questions to collect the data).

Adults with symptomatic lumbar herniated disc in whom conservative medical management has failed and: 1) in whom discectomy or microdiscectomy is indicated, 2) have been included in surgery waiting list by the Neurosurgery Department, 3) who meet criteria for potential benefit with ozone therapy and 4) who accept participating in the study by answering/filling in the specific study questionnaires (wether they accept or not the ozone therapy).