Cervical cord compression due to ossified posterior longitudinal ligament associated with diffuse idiopathic skeletal hyperostosis

Osterix is a key target for mechanical signals in human thoracic ligament flavum cells

Mechanical stress is considered to be an important factor in the progression of thoracic ossification of the ligament flavum (TOLF). To elucidate the mechanism underlying mechanical stress-induced TOLF, we investigated the effect of stretching on cultured flavum ligament cells derived from TOLF and non-TOLF patients. We found that the mRNA expression of alkaline phosphatase (ALP), osteocalcin, Runx2, and osterix, but not that of Dlx5 and Msx2, was significantly increased by stretching in TOLF cells. In addition, the effect seems to be finely tuned by stretching-triggered activation of distinct mitogen-activated protein kinase cascades. Specifically, a p38 specific inhibitor, SB203580, significantly inhibited stretching-induced osterix expression as well as ALP activity, whereas a specific inhibitor of ERK1/2, U0126, prevented stretching-induced Runx2 expression. We showed that overexpression of osterix resulted in a significant increase of ALP activity in TOLF cells, and osterix-specific RNAi completely abrogated the stretching-induced ALP activity, indicating that osterix plays a key role in stretching-stimulated osteogenic effect in TOLF cells. These results suggest that mechanical stress plays important roles in the progression of TOLF through induction of osteogenic differentiation of TOLF cells, and our findings support that osterix functions as a molecular link between mechanostressing and osteogenic differentiation.

[Surgical management of cervical radiculopathy in Forestier's disease. Case report and review]

Forestier's disease now called DISH (diffuse idiopathic skeletal hyperostosis) is a non inflammatory enthesopathy ossifying the anterolateral spine and sparing the disc and joint space in elderly men, mostly at thoracic levels. Radiology performed for minor trauma or to explore a stiff neck provides the diagnosis. The main differential diagnosis is ankylosing spondylitis presenting an inflammatory profile as well as previously existing alterations of the sacroiliac joint. Retinoic acid treatment or ossification of the posterior longitudinal ligament should also be discussed. Dysphagia is the most frequent symptom, but neurological signs are rarely observed. We report a case observed at the cervical level. Anterior decompression and cage-fusion was indicated. Ongoing hyperostosis was also documented. Surgery in DISH is mainly indicated for dysphagia and rarely after cervical trauma. Of note are associated lesions such as OPLL (ossification of the posterior longitudinal ligament) or synovial cysts responsible for the exceptional and severe myelopathy presentation. The neurosurgical community should become better aware of Forestier's disease.