Disc degeneration is a progressive deterioration process of the intervertebral disc, which can manifest as significant low back pain and a loss of mobility that interferes with daily activities. This condition is naturally age-related and exacerbated by traumatic events, lifestyle factors, and individual genetic susceptibilities. Treatment for advanced disc degeneration typically involves surgery (spinal fusion) aimed at addressing and fusing the affected intervertebral discs using an interbody implant combined with a bone graft.

Although the use of interbody implants promotes temporary fusion, long-term success largely depends on the bone substitute used, with failure rates ranging from 10 to 20% (unsuccessful fusion, persistent symptoms, need for reoperation). Historically, autologous bone grafting was the standard, but it carries disadvantages related to pain and invasiveness. Synthetic, bioactive bone substitutes are now used, although their effectiveness varies.

Animal studies support the hypothesis that a new substitute based on specific osteo-immunology technology (MagnetOs, Kuros) could offer superior results compared to autologous bone grafts and competing osteo-inductive materials, while being minimally invasive. This study aims to evaluate its properties in terms of bone fusion and its impact on functional scores in patients, hypothesizing a significant improvement in fusion rates and functional scores with this new substitute.

Degenerative lumbar spine disease increasingly relies on surgery to treat and fuse one or more pathological intervertebral discs. The transabdominal retroperitoneal, or anterior, approach allows full access to and treatment of the diseased disc, enabling a more physiological restoration of spinal alignment. Implants placed in the interbody position provide immediate vertebral stabilization, while the bone graft or bone substitute added to the interbody implant enables long-term fusion through neo-ossification of the segment.

The quality and speed of fusion achieved largely depend on the bone substitute used, and this fusion is a key factor in obtaining good functional outcomes for the patient. In approximately 10 to 20% of cases, this fusion does not succeed, resulting in persistent pain symptoms and potentially requiring reoperation.

Historically, to achieve this fusion, autologous bone was harvested from another anatomical site, most often the iliac crest. This autologous bone graft requires an additional incision, which is often associated with pain and discomfort. For these reasons, synthetic or biologic bone substitutes have been developed by pharmaceutical engineering to avoid bone harvesting, and are now routinely used in clinical practice.

To date, many bioactive bone substitutes have obtained marketing authorization, but their effectiveness varies depending on their physicochemical composition. It is accepted that the fusion rate could improve by up to 60% depending on the bone substitute used.

Animal studies support the hypothesis that a new bone substitute, referred to here as Substitute A, based on specific osteoimmunology technology (MagnetOs, Kuros), is equivalent to the current gold standard (autologous bone graft) in terms of achieved fusion, and superior to competing osteoinductive products that are routinely used at Montpellier University Hospital and in most other hospitals to achieve spinal fusion (6). This suggests the possibility of achieving equivalent outcomes through a faster, less invasive, less painful procedure with no limitation on the volume of substitute used.

Due to its favorable characteristics, this product (Substitute A) was recently endorsed by the Commission for Medicines and Sterile Medical Devices (CMDMS) of Montpellier University Hospital, authorizing its appropriate use in this indication, though currently limited to a small number of batches. This project would allow us to demonstrate the benefits of Substitute A so that it could subsequently be adopted for routine use.

This trial is a single-center, prospective, randomized, controlled superiority trial, with single-blind evaluation of the primary outcome measure. This study aims to include 100 patients. A non-stratified randomization with random block sizes will be performed to allocate participants in a 1:1 ratio into the following groups: Group A receiving the investigational device (bone substitute, Magnetos Putty, Kuros Medical) and Group B receiving the routine treatment (bone substitute, GlassBone Putty, Noraker).

Simplified study calender:

Visit 1: Information between 6 months and 1 month before Day 0 Preoperative consultation to determine the indication for surgery and the date of the operation

• Presentation of the trial, description of the practical aspects of the study and randomization process
• Provision of the information sheet

Visit 1: Before the intervention (Day -1) Re-presentation of the trial, description of the practical aspects of the study and randomization process

• Verification of eligibility criteria
• Obtaining informed consent
• Collection of demographic data : age, sex, occupation, Body Mass Index (BMI), medication use, smoking, alcohol consumption, medical history)
• Health questionnaires : Visual Analogue Scale (VAS), Oswestry Disability Index (ODI)
• Collection of imaging data : high-resolution lumbar Computed Tomography (CT) scan and lumbar X-ray)

Visit 2: Day 0 (Surgical intervention day) Randomization will be performed at the earliest, the day before or on the day of the intervention.

Patients will be randomized into either the conventional or experimental arm. The allocated arm will be communicated to the neurosurgeon investigator responsible for the operation. The patient will remain blinded to their treatment group.

The surgical intervention will be performed according to the standard anterior lumbar fusion procedure, except for the bone substitute, which will vary according to randomization.

Visit 3: 3 months (+/- 15 days)

Following the usual care for patients who have undergone anterior lumbar interbody fusion:

• Low back and radicular pain (VAS)
• Functional score (ODI)
• Imaging for a 3-month assessment (high-resolution lumbar CT scan)
• Collection of additional data (return to work, medication use)

Visit 4: 12 months (+/- 15 days)

Following the usual care for patients who have undergone anterior lumbar interbody fusion:

• Low back and radicular pain (VAS)
• Functional score (ODI)
• High-resolution lumbar CT scan and lumbar X-ray in weight-bearing and dynamic positions
• Collection of additional data (return to work, medication use...)

Inclusion Criteria:

• Patients aged between 18 and 80 years inclusive
• Oswestry Disability Index (ODI) >25
• Chronic low back pain and/or radicular pain lasting for more than 6 months
• Failure of medical and rehabilitative treatment
• Patient presenting with one of the following: grade 1 degenerative spondylolisthesis without isthmic lysis, or disc degeneration, or mixed pathology (degeneration and lumbar stenosis)
• Patient eligible for anterior approach spinal fusion surgery with interbody cage

Exclusion Criteria:

• History of spinal surgery at the lumbar level, excluding isolated discectomies for disc herniation

• Confirmed osteoporosis

• Surgical fusion at an adjacent level

• Contraindication to Magnetos Putty or GlassBone Putty:

  1. Use of medications interfering with calcium metabolism
  2. Severe systemic or metabolic bone disorders affecting bone healing or lesions
  3. Untreated acute or chronic infection requiring appropriate therapy
  4. Patients with severe trauma and open external wounds near the defect site, at risk of infection
  5. Known allergy to bioactive glass or its components (Ca2+, PO43-, Na+, and Si(OH)4), polyethylene glycol, and/or glycerol
  6. Patients who have undergone or will undergo chemotherapy or radiotherapy at or near the implantation site
  7. Severe renal or hepatic infections
  8. Unrepaired dural tear in craniospinal surgery

• Patients requiring placement of more than one implant

• Subject unable to read and/or write fluent French, or illiterate

• Subject already participating in another interventional clinical trial that could interfere with this study

• Uncontrolled psychiatric illness

• Lack of written informed consent after a reflection period

• Individuals with a dependency or employment relationship with the sponsor or investigator

• Subject enrolled in another study with an ongoing exclusion period (Article L1121-12)

• Subject not affiliated with or not a beneficiary of the French social security system (L1121-8-1)

• Protected populations under French Public Health Code:

  1. Pregnant or breastfeeding women (L. 1121-5)
  2. Individuals deprived of liberty (art. L. 1121-6) (by judicial, administrative decision or involuntary hospitalization)
  3. Protected adults (under guardianship, curatorship, or legal protection) (L. 1121-8)

• Women planning to become pregnant within the year