Unilateral Biportal Endoscopic (UBE) Treatment of Symptomatic Lumbar Facet Cysts After Interspinous Ligamentoplasty: Report of Two Cases and Literature Review.

Interspinous ligamentoplasty (ILP) is an effective, minimally invasive technique used to treat low-grade degenerative spondylolisthesis (DSL) and lumbar spinal stenosis (LSS). However, it may be associated with postoperative complications, including the formation of a facet cyst (FC). Various surgical strategies have been developed to address these clinical challenges. In recent decades, minimally invasive techniques, such as unilateral biportal endoscopy (UBE), have gained popularity for achieving adequate decompression while preserving segmental stability. We report two cases of patients with Grade I DSL and LSS who initially experienced symptomatic relief following treatment with ILP. Within months, both developed recurrent radicular pain and neurogenic claudication. Magnetic resonance imaging (MRI) revealed FCs at the previously decompressed levels. After the failure of conservative treatment, UBE-assisted cyst resection and decompression were performed. In both cases, operative time was brief, and patients achieved significant symptom resolution without perioperative complications. ILP may be a motion-preserving alternative to pedicle-based fusion for mild-to-moderate LSS with low-grade DSL. However, residual micromotion and facet stress may predispose to FC formation. UBE is a minimally invasive management alternative for cyst resection and nerve decompression, preserving facet integrity and potentially reducing the risk of adjacent segment disease. In patients with advanced instability, fusion may still be required. While early outcomes have shown to be favorable, the limited follow-up highlights the need for longitudinal studies to clarify long-term recurrence rates, indications for secondary fusion, and comparative outcomes against traditional fusion techniques. UBE may enable precise FC removal with minimal tissue disruption, offering an alternative option for recurrent radiculopathy after ILP. This approach may help preserve spinal motion while effectively addressing symptomatic lesions. Larger prospective studies with more extended follow-up periods are necessary to confirm these findings and refine treatment algorithms for FCs arising after ILP.