The role of cerebrospinal fluid cross-section area ratio in the prediction of dural ossification and clinical outcomes in patients with thoracic ossification of ligamentum flavum

Abstract

Background It is imperative to preoperatively distinguish dural ossification (DO) and thus anticipate the risks and outcome of the surgery for patients with ossification of ligamentum flavum (OLF). However, studies have disagreed as to the efficacy of the radiographic signs or factors to predict DO and surgical outcome. In additon, the association between the cerebrospinal fluid cross-section area ratio (CCAR) and DO or clinical outcome had not been reported. The purpose of this study was to analyse CCAR and its role in prediction of DO and neurological function recovery rate in patients with OLF. Methods Fifty-two consecutive patients with OLF, who underwent posterior thoracic decompression and fusion between September 2012 and March 2019 at a single institution, were retrospectively reviewed. Demographic data, radiographic signs of DO, CCAR, pre- and postoperative modified Japanese Orthopedic Association (mJOA) score were recorded. Results There were 27 patients in the DO group and 25 patients in the non-DO group, with a mean age at surgery of 57.4 years and 53.9 years, respectively. No significant differences were found in sex, age, segment of maximum compression and preoperative mJOA score between the two groups. The receiver operating characteristic curve showed that the value of CCAR had a relatively high value for diagnosis of DO and prediction of neurological function recovery rate (P = .000). According to the value of CCAR, three zones were defined as DO zone (≤14.3%), non-DO zone (≥44.5%), and gray zone (14.3 to 44.5%). When the value of CCAR≤14.3%, the recovery rate was poor or fair, while it had good or excellent recovery when CCAR≥45.2%. Conclusion The value of CCAR had a high diagnostic value for prediction of DO and neurological function recovery rate in patients with OLF.

Three-dimensional imaging analysis for the diagnosis of dural ossification in thoracic ossification of the ligamentum flavum: a multicenter study

“…Although the 2D OR could reflect the degree of bilateral compression, it could not assess the range of compression (14). Several radiographic parameters have been linked to OLF compression in previous studies, including the sagittal, coronal, and axial dimensions, which highlights the inadequacy of assessment from only a single dimension (9,(12)(13)(14)(29)(30)(31). In contrast, the 3D OR could make up for this owing to its comprehensive assessment of OLF compression from multiple dimensions.…”

“…If the probability of DO could not be foreseen preoperatively, the risk of surgical complications, especially CSF leakage and spinal cord injury, would increase considerably (9). Although imaging signs such as the "comma sign" and "tram track sign" have been proposed for the diagnosis of DO, their misdiagnosis rates were reported to be 38.9%.…”

“…Additionally, the 2D OR showed a higher diagnostic coincidence rate compared with the 1D OR, but this difference was not statistically significant. In fact, the 1D OR could only assess the degree of unilateral compression of OLF (9). Although the 2D OR could reflect the degree of bilateral compression, it could not assess the range of compression (14).…”

“…Potential sequelae of chronic OLF are the compression and subsequent ossification of the dura mater, resulting in an inseparable osseous fusion between the ligamentum flavum and the dura mater (1,6,7). For surgeons, unforeseen dural ossification (DO) may increase the risk of intraoperative complications, such as cerebrospinal fluid (CSF) leakage and spinal cord injury (3,(7)(8)(9). Preoperative diagnosis of DO assists surgeons in making comprehensive preparations for the surgical procedure.…”

“…Furthermore, there are variations in how the slices through tissues are obtained based on the spinal curvature, especially for the upper or middle thoracic spine, which might lead to deviations in the results of conventional measurement methods (13)(14)(15)(16). Therefore, most of the current findings can only be applied to the lower thoracic spine, despite nearly 50% of DOs being located in the upper and middle segments (9,12,14,15).…”