A potential mechanism of dural ossification in ossification of ligamentum flavum.

Ossification of the ligamentum flavum (OLF) mostly occurs in the thoracic spine, leading to thoracic spinal stenosis. Surgical treatment is considered as the best option for OLF patients. When the dura mater ossifies, the difficulty of surgery and the risk of complications significantly increase. The cause of dural ossification (DO) is still unknown. Based on the existing research and clinical studies, we propose a potential mechanism of DO in OLF. Firstly, with the progression of OLF, it will compress the dura mater and even the spinal cord. Then, with flexion and extension of spine, relative movement (friction) between the ossified ligamentum flavum and compressed dura mater will lead to local inflammation, subsequently causing dural adhesion. Finally, the adhesion tissue can serve as a pathway for the transportation of osteogenic cytokines (BMP for example) from the ossified ligamentum flavum to the compressed dura mater. Dura will ossify under exposure of these osteogenic cytokines. If this hypothesis is confirmed, it will contribute to the prevention and management of DO. For progressive OLF patients, early surgical treatment before DO should be recommended.