Prospective Observational Study of the Treatment of Mechanical Low Back Pain With High-Intensity Focused Ultrasound (HIFU) of the Lumbar Medial Branch.
Conditions: Lumbago
Sponsor: Consorci Sanitari de Terrassa

GENERAL INFORMATION 
Title: Prospective observational study of the treatment of mechanical low back pain using 
High-Intensity Focused Ultrasound (HIFU) of the lumbar medial branch. 
Version: Version 3, 28/11/2025 
Sponsor: Fundació Monclínic 
 
RESEARCH TEAM 
Principal Investigator: Carles Espinós Ramírez 
Collaborating Researchers: Guilherme Madaleno Dos Santos, Jordi Pérez Martínez 
 
PROTOCOL SUMMARY 
Main Objective: To evaluate the clinical efficacy of lumbar medial branch ablation using the 
HIFU technique at 1, 3 and 6 months. 
Primary Variable: Spanish version of the Oswestry Disability Index. 
Study Design: Prospective, descriptive, single-center observational study with 6-month 
follow-up. 
Population: Patients with mechanical low back pain without other associated clinical 
features (neuropathic pain characteristics or strong suspicion of pain originating in other 
anatomical areas that could cause low back pain) who undergo lumbar medial branch 
ablation using the HIFU technique. 
Total number of participants: Approximately 70–80 patients. 
Source of data: Primary source (directly from the patient). 
Additional procedures: Baseline assessment and questionnaire; lumbar medial branch 
ablation with HIFU; telematic follow-up questionnaires at 1, 3 and 6 months. 
 
BACKGROUND AND JUSTIFICATION: Chronic low back pain attributable to degeneration 
of the facet joints is a prevalent cause of disability, with a significant proportion of cases 
related to nociceptive conduction through the lumbar medial branch. Radiofrequency 
ablation (RFA) of the medial branch is the standard minimally invasive treatment for 

patients refractory to conservative therapy, although it may be associated with 
non-negligible local complications. In addition, medial branch RFA requires percutaneous 
insertion of probes, which may be uncomfortable for the patient and technically demanding. 
High-Intensity Focused Ultrasound (HIFU) is an emerging technology that enables 
non-invasive targeted thermal ablation of deep tissues by concentrating acoustic energy on 
the target nerve while preserving adjacent structures. Preclinical studies in porcine models 
have demonstrated that HIFU can denervate the lumbar medial branch with efficacy equal 
to or greater than RFA without significant adverse effects. 
Recent open clinical studies have confirmed the feasibility, safety and effectiveness of HIFU 
in patients with lumbar facet syndrome, showing response rates similar to RFA and absence 
of major complications. HIFU offers potential advantages such as non-invasiveness, reduced 
infection risk and the possibility of repeating the procedure without cumulative damage. 
The implementation of HIFU for lumbar medial branch denervation may represent a 
substantial improvement in the management of chronic low back pain, reducing the 
aggressiveness of the procedure and minimizing complications. This study protocol aims to 
collect data on the clinical efficacy of medial branch treatment with HIFU at our center as 
well as the degree of patient satisfaction. 
 
STUDY HYPOTHESIS: HIFU is an effective, safe and minimally invasive technique for 
lumbar medial branch ablation in patients with chronic mechanical low back pain. 
 
OBJECTIVES: To evaluate the clinical efficacy of lumbar medial branch ablation using HIFU 
at 1, 3 and 6 months and to assess patient satisfaction with the therapeutic procedure. 
 
STUDY VARIABLES: A structured questionnaire will record the following variables: patient 
demographics (age, weight, height), personal medical and surgical history, usual 
medication, and pain-related data. 
Pain variables include the Numeric Verbal Scale (0–10) at rest, during movement and 
average pain; Spanish version of the Oswestry Disability Index; Spanish version of the Pain 
Catastrophizing Scale; and the Brief Pain Inventory evaluating the impact of pain on daily 
activities. 
 
PATIENT FOLLOW-UP: Patients will be evaluated remotely at 1, 3 and 6 months. The 
following variables will be recorded: pain scores, Oswestry scale, catastrophizing scale, 

Brief Pain Inventory, perceived degree of improvement after treatment, changes in pain 
characteristics, and indication of any new therapeutic approach. 
 
STUDY DESIGN: This is a prospective descriptive observational study conducted at a single 
center. Recruitment will occur in person at the Pain Unit evaluation visit. Follow-up will last 
6 months and will be conducted remotely at 1, 3 and 6 months. 
The investigation involves a CE-marked medical device used according to its clinical 
indication for neuroablation of neural tissue. The system enables targeted thermal ablation 
of deep tissues in a non-invasive manner by focusing acoustic energy on the target nerve. 
 
PARTICIPANT SELECTION 
Recruitment process: Patients attending evaluation or follow-up consultations at the Pain 
Unit will be sequentially recruited. The study objectives will be explained and patients will 
sign informed consent if they agree to participate. 
Inclusion criteria: Age over 18 years; signed informed consent for data collection; 
mechanical low back pain with positive diagnostic medial branch block (pain reduction 
>30%) using local anesthetic. 
Exclusion criteria: Age under 18; mixed pain or suspected multiple etiologies (e.g., 
sacroiliac involvement); active systemic infection; pregnancy; prior spinal surgery at the 
treatment level; tumors, metastatic disease or osteoporosis in the treatment area; 
pacemakers or implantable generators; coagulation disorders or thrombocytopenia; 
vertebral fracture or compression at the treatment level; or health conditions 
contraindicating sedation or treatment positioning. 
 
STUDY PROCEDURES 
Description of the HIFU technique: Pre-procedure fluoroscopy is used to locate the 
medial branch. The patient is positioned prone with light sedation or local anesthesia. A 
HIFU transducer focuses acoustic energy on the nerve pathway while avoiding other 
structures. A single focused exposure lasting approximately 50 seconds with around 1000 
joules is delivered, aiming to reach temperatures of 80–85°C to induce thermal necrosis of 
the nerve. 
Post-procedure control: Immediate clinical response and possible adverse effects are 
evaluated. Follow-up includes pain scales and disability indices. 

 
FOLLOW-UP VISITS: Patients will receive telematic visits at 1, 3 and 6 months after lumbar 
medial branch ablation with HIFU. These follow-ups are standard practice in Pain Units to 
evaluate the effectiveness and safety of infiltrative techniques. 
 
STATISTICS 
Sample size: Between 70 and 80 patients will be sequentially included. 
Statistical analysis: Descriptive statistics will be used. Quantitative variables will be 
described using mean and standard deviation for normally distributed data, or median and 
interquartile range for skewed distributions. Qualitative variables will be summarized with 
absolute frequencies and percentages. Normality will be assessed using Shapiro–Wilk or 
Kolmogorov–Smirnov tests. 
 
ADVERSE EVENT MANAGEMENT: All suspected adverse events related to the HIFU 
procedure will be continuously monitored. Events will be recorded with description, date of 
onset, duration, severity, causal relationship with the procedure and interventions 
performed. 
Events will be classified as mild, moderate or serious adverse events according to 
regulatory definitions. Serious adverse events will be reported to the study sponsor within 
24 hours and to the relevant regulatory authorities and ethics committee according to 
applicable regulations. 
 
ETHICS AND LEGAL ASPECTS: Data collection will follow the principles of the Declaration 
of Helsinki, European and Spanish biomedical research regulations, and applicable medical 
device legislation. Data collection will begin after approval of the protocol by the hospital's 
Clinical Research Ethics Committee. 
Participants will receive information about the study and their participation will be 
voluntary. They may withdraw at any time without affecting their medical care. 
 
RISK-BENEFIT ASSESSMENT: This observational study does not introduce additional risks 
beyond those associated with standard HIFU treatment. Potential benefits include 
improvement of chronic low back pain. Possible risks include temporary discomfort, heat 
sensation, local redness or rare irritation of nearby nerve structures. 

 
DATA MANAGEMENT: Data will be coded so that patients cannot be directly identified. 
Only the principal investigators will have access to the coding key and the clinical records. 
The database will be stored in a password-protected Excel file on the institution's secure 
OneDrive. Only authorized investigators will have access. 
 
CONFIDENTIALITY AND DATA PROTECTION: Data processing will comply with the EU 
General Data Protection Regulation (GDPR) and Spanish data protection legislation. Data 
will be stored using coded identifiers and may only be accessed by authorized personnel, 
ethics committees or health authorities when required for verification. 
 
BIOLOGICAL SAMPLES: No biological samples will be collected in this study. 
 
FUNDING: This study does not receive external funding. 
 
DISSEMINATION POLICY: The investigators commit to making the study results public 
regardless of whether they are positive or negative.