New classification of facet joint synovial cysts

Facet cysts develop due to degeneration of the zygapophyseal joints and can lead to radiculopathy and neurogenic claudication. Various surgical options are available for facet cyst excision. The aim was to facilitate surgical treatment of lumbar facet cysts based on a new classification. We retrospectively analyzed all patients of the last 10 years in whom a facet cyst was surgically removed (ipsilateral laminotomy, contralateral laminotomy, and segmental fusion). Several radiological parameters were analyzed and correlated with the patients’ outcome (residual symptoms, perioperative complications, need for re-operation, need for secondary fusion, facet cyst recurrence). One hundred eleven patients (55 women; median age 64 years) could be identified. Thirty-three (48%) of 69 cases, for which MRI data were available, were classified as medial facet cyst (compressing the spinal canal), 6 facet cysts were localized intraforaminal (9%) and 30 cases (43%) mediolateral (combination of both). The contralateral approach had the lowest rate for revision surgery (7.5%, p = .038) and the lowest prevalence of residual complaints (7.5%, p = .109). A spondylolisthesis and a higher/steeper angle of the facet joints were associated with poorer patient outcome. Lateral facet joint cysts are best resected by a contralateral approach offering the best outcome while medial cysts are suitable for removal by an ipsilateral laminotomy. The approach of mediolateral cysts can be determined by the width of the lamina and the angle of the joint. Segmental fusion should be considered in cases with detected spondylolisthesis and/or steep facet joints.