Analyses of imaging presentations, full endoscopic and pathological features of a novel interlaminar ligament

To analyze the characteristics of an unnamed interlaminar ligaments(ILL) through magnetic resonance image (MRI), endoscopy and pathological examination.

A retrospective study was conducted to analyze the clinical data of patients who underwent posterior endoscopic surgery for lumbar disc herniation or lumbar spinal stenosis from January 2021 to February 2022 at our medical center. The height, width and cross-sectional thickness of the ligament was analyzed using T2 weighted MRI. Meanwhile, the morphological and pathological characteristics were also compared with those of the ligamentum flavum to highlight the differences between above mentioned ligaments.

Forty-three patients were included in this study, including 27 males and 16 females, with an average age of 46.6 ± 12.1y. There were 20 cases of lumbar disc herniation and 23 cases of lumbar spinal stenosis. The width, length, thickness of the ILL, the thickness of LF and surgical time in the lumbar disc group were 17.7 ± 3.5 mm, 4.3 ± 1.3 mm, 18.3 ± 3.5 mm, 5.3 ± 1.9 mm, 53.2 ± 14.5 min, respectively. In the lumbar spinal stenosis group, the corresponding parameters were 16.0 ± 3.1 mm, 4.1 ± 1.6 mm, 17.6 ± 4.8 mm, 6.3 ± 0.8 mm, 61.8 ± 12.4 min, respectively. The intergroup difference in thickness of the ligamentum flavum was statistically significant (P = 0.02). The difference in surgical time was also established(P = 0.04). Endoscopic differences were identified as to the location of the anchor points and appearances among the two ligaments. Significant differences in the density and direction of fibrous structures were also observed under biopsy. Under endoscopy, significant difference as to the grade of ILL thickness was established when compared regarding disease spectrum (P = 0.09.) CONCLUSION: The interlaminar ligament is a structure that has not yet been officially named, which has significant structural differences from those of the ligamentum flavum. For posterior endoscopic procedure, its clinical significance lies in its ability to serve as the endpoint of soft tissue channel establishment. The thickness of the ligamentum flavum in MRI and the thickness of ILL under endoscopy vary according to the disease spectrum.