Morphology and TGF-beta1 Concentration's Analysis of Ligamentum Flavum of Patients with Lumbar Canal Stenosis and Lumbar Disc Herniation

Abstract

IntroductionThe most common spinal disorder in elderly patients is lumbar spinal canal stenosis, causing low back and leg pain, and paresis. The etiology of degenerative changes occurring in lumbar stenosis still remain unclear: some authors hypothesize the hyperplasia and others the hypertrophy of Ligamentum flavum (LF). The change of LF is known to be related to degenerative changes that are secondary to the aging process or mechanical instability. The study's objective is to analyze the LF of patients with lumbar canal stenosis and lumbar disc herniation to evaluate the morphology and the concentration of the Transforming Growth Factor-β 1 (TGF-β 1).Material and Method:The study is characterized by three phases: (A) Measurement of the thickness of the LF of patients with lumbar stenosis and/or herniated lumbar disc through the axial, T1 weighted images of the lumbo-sacral magnetic resonance imaging (MRI); (B) Removal of LF in patients undergoing intervention for lumbar stenosis and lumbar disc herniation (control group); (C) Optical microscopy study of the morphology of degenerated ligamentum and immunohistochemical analysis to assess the concentration of TGF-β 1 in the same. The analysis of the morphology of the ligamentum (meant as the increase of the fibers number or distension and relaxation of the same as a result of degenerative processes) and the presence or absence of a high concentration of TGF-β1 (then more fibroblasts involved in the degenerative process) can be important to clarify if there is an hypertrophy or hyperplasy of ligamentum flavum in lumbar canal stenosis. ResultsIn the current study we have showed that decreased elasticity of LF in the elderly is due to the loss of elastic fibers that are degenerated and a concomitant increase of collagenous fibers (hypertrophy); the concentrations of TGF-β1 of the LF measured in both lumbar spinal stenosis and disc herniations was higher than that of the latter. ConclusionThe current results suggest that LF of lumbar canal stenosis is hypertrophic: LF hypertrophy could be due to the thickening of the normal elastic layer as well as of the abnormal collagenous layer and to higher expression of TGF-β 1 by fibroblasts