Frequency and size of ossifications in the caudal attachements of the ligamentum flavum of the thoracic spine. Role of rotatory strains in their development

Abstract

Ossifications in the caudal attachments of the ligamentum flavum were studied on 121 dried thoracic spines. Most of them were aged. Frequency increased in a caudal direction. At T12, frequency depended on the orientation of the zygapophyseal joints of T11-12 which determined the range of rotation. When they were of thoracic orientation, allowing large range of rotation, ossifications were present in 83% of cases. If orientation was lumbar, allowing poor range of rotation, ossifications became much less frequent:33%. The size of ossifications was also studied. The smaller were in T1 and T2. In T11 and T12, size also depended on the orientation of the zygapophyseal joints of T11-12. If it allowed important range of rotation, ossifications were large sized. In the opposite case, they were small sized. Ossifications of caudal attachments of ligamentum flavum appear to be a normal feature of the aged lower thoracic spine. Their frequency in a given motion segment seems to be influenced by rotational strains.

Clinical characteristics and surgical outcome of thoracic myelopathy caused by ossification of the ligamentum flavum: a retrospective analysis of 85 cases

“…15,18,34,54,55 In our study, we also found similar results. In addition, it has been reported Clinical characteristics and surgical outcome of TM caused by OLF Z Li et al that the location of OLF is less vulnerable in mobile segments such as the cervical and lumbar vertebra than in the thoracic vertebrae.…”

“…In addition, it has been reported Clinical characteristics and surgical outcome of TM caused by OLF Z Li et al that the location of OLF is less vulnerable in mobile segments such as the cervical and lumbar vertebra than in the thoracic vertebrae. 26,30,40,55,56 This phenomenon gives us insight about the pathogenetic mechanism of OLF. On the basis of the literature review, we hypothesized that biomechanical and anatomical factors might have a key role in thoracic OLF progression.…”

“…In addition to the anatomical difference relating to mechanical stress involving constraints on the articular processes during segmental motion, this difference may also be attributed to increased instability in lower thoracic spine. 41,55,57 Compared with the middle thoracic spine, it seems to be more particularly easy to make degenerative processes on the lower thoracic spine owing to the high tensile force present on the posterior column. 22,55 Maigne et al 55 reported that OLF occurred most frequently at the lower thoracic spine especially at the thoracolumbar junction, and its appearance correlated with a unique orientation of the facet joints that generated increased rotatory instability and micromotion.…”

Thoracic Myelopathy Caused by Ossification of the Ligamentum Flavum

“…This region appears to be particularly prone to degenerative processes due to the high tensile force present on the posterior column. Maigne et al 7) showed a direct correlation between increased mobility of the spine and repetitive mild trauma to the ligamentum flavum with the frequency and size of the ossification in the thoracic spine. They reported that OLF occurred most frequently at the thoracolumbar junction and its appearance correlated with a unique orientation of the zygapophyseal joints that contributed to increased rotatory instability and micromotion 7) .…”

“…Maigne et al 7) showed a direct correlation between increased mobility of the spine and repetitive mild trauma to the ligamentum flavum with the frequency and size of the ossification in the thoracic spine. They reported that OLF occurred most frequently at the thoracolumbar junction and its appearance correlated with a unique orientation of the zygapophyseal joints that contributed to increased rotatory instability and micromotion 7) . Finally, OLF can be accompanied by certain metabolic diseases of genetic origin, such as hypophosphatemia 8,20) .…”