Degenerative pathologies of the spine affect a large proportion of the increasingly ageing population, and are a major public health issue. When conservative treatments (physiotherapy, analgesics, infiltrations) fail, surgical treatment is preferred.

Traditionally, a simple lumbar recalibration operation is preferred (bilateral laminectomy decompression), but this may affect spinal stability. In cases of spondylolisthesis or preoperative instability, lumbar fusion (arthrodesis) is sometimes necessary to avoid the risk of major instability, but such an operation is not without risk and may require repeat surgery.

The development of new surgical techniques such as uni or bilateral laminotomies, which are less radical, has made it possible to avoid some arthrodeses. Nowadays, the emergence of new surgical techniques such as endoscopy has further reduced the risk of destabilization (shorter post-operative convalescence, less atrophy of the paraspinal muscles) and improved surgeon comfort (better vision and easier instrument handling).

Unilateral biportal endoscopy (UBE) is one of two endoscopic techniques and has proven its effectiveness for lumbar decompression in terms of clinical benefits. However, there is no scientific evidence on spinal stability after recalibration under UBE.

We believe that minimizing invasiveness with UBE during simple lumbar recalibration surgery can preserve spinal stability, thereby reducing the need for lumbar fixation and lowering the cost of care.

We therefore propose to study the maintenance of spinal stability using dynamic radiography at 3 months post-operatively in patients undergoing lumbar recalibration surgery with UBE.

Spinal stability is defined by the absence of abnormal mobility (sagittal translation of at least 3 mm) between flexion and extension movements and will be assessed on the 3-months postoperative dynamic radiography.

Patients will undergone an additional dynamic radiography 3 months after surgery to assess their spinal stability.

Inclusion Criteria:

• Patient ≥ 50 ans,
• Patient requiring single-level or 2-levels lumbar decompression surgery under UBE,
• Patients who underwent dynamic radiography within 3 months prior to surgery,
• Patient who received information on the study and who signed the consent form.

Exclusion Criteria:

• Presence of a mobile spondylolisthesis with a ≥ 3 mm difference between flexion and extension movements on preoperative dynamic radiography,
• Patient with history of lumbar arthrodesis,
• Patient not available for study follow-up.