The Role of the Ligamentum Flavum Area as a Morphological Parameter of Lumbar Central Spinal Stenosis

Abstract

Background: Hypertrophy of the ligamentum flavum (LF) has been considered as a major cause of lumbar central spinal stenosis (LCSS). Previous studies have found that ligamentum flavum thickness (LFT) is correlated with aging, disc degeneration, and lumbar spinal stenosis. However, hypertrophy is different from thickness. Thus, to evaluate hypertrophy of the whole LF, we devised a new morphological parameter, called the ligamentum flavum area (LFA). Objectives: We hypothesized that the LFA is a key morphologic parameter in the diagnosis of LCSS. Study Design: Retrospective observational study. Setting: The single center study in Seoul, Republic of Korea. Methods: LF samples were collected from 166 patients with LCSS, and from 167 controls who underwent lumbar magnetic resonance imaging (MRI) as part of a routine medical examination. T1- weighted axial MR imageswere acquired at the facet joint level from individual patients. We measured the LFA and LFT at the L4-L5 intervertebral level on MRI using a picture archiving and communications system. The LFA was measured as the cross-sectional area of the whole LF at the L4-L5 stenotic level. The LFT was measured by drawing a line along the side of the ligament facing the spinal canal and along the laminar side of the ligament curve and then measuring the thickest point at the L4-L5 level. Results: The average LFA was 96.56 ± 30.74 mm2 in the control group and 132.69 ± 32.68 mm2 in the LCSS group. The average LFT was 3.61 ± 0.72 mm in the control group and 4.24 ± 0.97 mm in the LCSS group. LCSS patients had significantly higher LFA (P < 0.001) and LFT (P < 0.001). Regarding the validity of both LFA and LFT as predictors of LCSS, Receiver Operator Characteristics (ROC) curve analysis showed that the best cut-off point for the LFA was 105.90 mm2 , with 80.1% sensitivity, 76.0% specificity, and area under the curve (AUC) of 0.83 (95% CI, 0.78 – 0.87). The best cut off-point of the LFT was 3.74 mm, with 70.5% sensitivity, 66.5% specificity, and AUC of 0.72 (95% CI, 0.66 – 0.77). Limitations: The principal methodological limitation was the retrospective observational nature. Anatomically, degenerative lumbar spinal stenosis can involve the central canal, foramina, and lateral recess. However, we focused on LCSS only. Conclusions: Although the LFT and LFA were both significantly associated with LCSS, the LFA was a more sensitive measurement parameter. Thus, to evaluate LCSS patients, the treating doctor should more carefully analyze the LFA than LFT. Institutional Review Board (IRB) approval number: S2015-1328-0001 Key words: Ligamentum flavum, ligamentum flavum area, ligamentum flavum thickness, lumbar central spinal stenosis, hypertrophy of the ligamentum flavum, morphological parameter, crosssectional area, optimal cut-off point

A Modified Laminotomy for Interlaminar Endoscopic Lumbar Discectomy: Technical Report and Preliminary Results

“…LDH in elderly patients are often complicated by canal stenosis resulting from the hypertrophy of the facet joints and ligamentum flavum. [19][20][21] Under such circumstances, these pathologies may be the main culprit responsible for sciatica or claudication and thus, discectomy alone may not be promising in relieving neurological symptoms. Instead of discectomy, decompression of the narrowed spinal canal should be the focus of the surgery.…”

Investigating Research Hotspots and Publication Trends of Spinal Stenosis: A Bibliometric Analysis During 2000–2018

“…Regarding the reason for thickening, studies have identified the epiligament in the ligamentum flavum, comprising collagenous fibers, while enlargement of the epiligament led to more collagenous than natural elastic fibers and canal tapering. Furthermore, the ligamentum flavum area has been compared with more sensitive measurement parameters than the ligament flavum thickness, playing a more valuable role (17). Close to the ventral wall of the canal, the herniation of intervertebral disc would narrow the spinal canal.…”

Lumbar Spinal Stenosis and Minimally Invasive Lumbar Decompression: A Narrative Review

“…13 Regarding the mechanism of the dynamic component of LSS, several articles have reported that posture-induced or axial pressure-induced elastic deformation of LF was the main contributor. [14][15][16][17][18][19][20][21] Lumbar extension or standing position may cause two adjacent laminas to move closer, followed by LF thickening and infolding. By contrast, lumbar flexion or lying flat position may cause the two-adjacent lamina to separate, resulting in the stretching and thinning of LF as well as the disappearance of LF infolding.…”