Unilateral Posterior Stabilization in Adult Spinal Pathologies: Comparative Clinical, Radiological, and Complication Outcomes of Dynamic Versus Rigid Systems

Background and Objectives: Unilateral spinal stabilization has emerged as a less invasive alternative to bilateral fixation in the management of lateralized spinal pathologies. While both rigid and dynamic systems are utilized, comparative data regarding their clinical efficacy, radiological outcomes, and complication profiles—particularly in multilevel applications—remain limited. Materials and Methods: A retrospective, two-center analysis was conducted on 113 patients who underwent unilateral posterior spinal stabilization between 2019 and 2023. Patients were divided into unilateral rigid stabilization (URS, n = 41) and unilateral dynamic stabilization (UDS, n = 72) groups. Pathologies of the patients include disc herniations, foraminal and spinal stenosis, tumoral lesions and spondylolisthesis. Clinical outcomes were assessed using the Visual Analogue Scale (VAS) over a 24-month follow-up. Radiological parameters included fusion status, superior adjacent disc height, and foraminal height index. Complication rates, including adjacent segment degeneration (ASD), pseudoarthrosis, and screw loosening, were analyzed according to type-of-stabilization and construct length (two, three, or four levels). Results: Both URS and UDS groups demonstrated significant VAS improvement at final follow-up, with no significant differences between groups (p < 0.001). Fusion rates were significantly higher in the URS group (85.37% vs. 27.78%, p < 0.001), while pseudoarthrosis (39.02% vs. 16.62%, p = 0.081) were more frequent in URS. No cases of rod fracture or infection were observed. Complication rates, particularly ASD, increased with longer constructs (6.56%, 21.21%, vs. 31.58% p = 0.01), independent of stabilization type. Conclusions: Unilateral stabilization—whether rigid or dynamic—offers effective symptom relief with reduced surgical morbidity. However, dynamic systems may provide biomechanical advantages by preserving motion and minimizing adjacent segment stress. While rigid constructs yield higher fusion rates, they are associated with increased complications. These findings support the use of dynamic stabilization, particularly in multilevel constructs, and highlight the need for patient-specific surgical strategies to optimize outcomes and mitigate long-term complications.