Background: The objectives of this study are to identify radiological factors associated with good functional outcomes after the implantation of BDYNTM dynamic stabilization system in the setting of painful low-grade degenerative lumbar spondylolisthesis (LDS).

Material and methods: In this monocentric, retrospective study, we followed 50 patients, a 5-years period, with chronic lower back pain, radiculopathy and/or neurogenic claudication evolving for at least one year that failed conservative treatment. All patients presented low-grade LDS and underwent lumbar dynamic stabilization. Radiological and clinical outcomes were assessed pre-operatively and 24 months after surgery. Functional evaluation was based on the Oswestry Disability Index (ODI), the Numerical Rating Scale (NRS), and the Walking Distance (WD). Radiological analysis was based on lumbar X-rays and MRI parameters. Patients were divided into two groups according to the reduction in the postoperative ODI score (more or less than 15 points), and statistical analysis was performed between both groups to find predictive radiological factors for a satisfying functional outcome.

Results: Clinically, 80% (40 patients) had a satisfying functional result, and 20% (10 patients) were considered having a poor outcome according to the ODI score. Radiologically, the loss in segmental lordosis was statistically associated with bad functional outcomes (18° for ODI decrease >15 versus 11° for ODI decrease <15). There is also a tendency showing that a higher Pfirmann disc signal grade (grade IV) and a severe canal stenosis according to Schizas classification (grade C & D) are predictive of a poor clinical result, but that must be confirmed in future studies.

Conclusions: BDYNTM appears safe and well-tolerated. This new device should be effective for the treatment of patients with low-grade LDS. It provides significant improvement in terms of daily life activity and pain. Moreover, we have been able to deduce that a kyphotic disc is associated with a bad functional outcome after BDYNTM device implantation. It may represent a contraindication for the implantation of such DS device. Moreover, it seems that it is better to implant BDYNTM in LDS with mild or moderate disc degeneration and canal stenosis.