Study design: An examination of surgical cases of membranocystic lesions in the lumbar yellow ligament between the fourth and fifth lumbar vertebrae.
Objectives: To report the incidence and pathogenesis of membranocystic lesions of the yellow ligament in surgical specimens.
Summary of background data: The membranocystic lesion has been observed not only in membranous lipodystrophy, but also in other conditions. However, there has been no report concerning this lesion in the yellow ligament.
Methods: Forty-four yellow ligaments excised in surgery were histologically reviewed. In eight cases, S-100 expression was investigated. In two cases, ultrastructural findings were examined.
Results: Membranocystic lesions were present in 8 (18%) of the 44 cases. The cases with the lesions had undergone surgery for spondylolisthesis (4 cases), sequestration-type disc herniation (2 cases), postradiation status (1 case), and spinal stenosis (1 case). Histologically, in all 8 cases, fibrosis was present around the lesion. In 5 of the 8 cases, chondrocytes were observed adjacent to the lesion, and nuclei positive for S-100 protein were observed in 4 cases. Nuclei of chondrocytes adjacent to the lesion also were positive for S-100 protein. Ultrastructurally, irregularly shaped cystic spaces surrounded by an electron-dense membranous structure, which were identical to those of membranous lipodystrophy, were observed.
Conclusions: These results suggest that degeneration of the chondrocytes has a causal relationship to the formation of membranocystic lesions in the yellow ligament.