Ultrastructure of early calcification in cervical ossification of the posterior longitudinal ligament

Abstract

A case of ossification of the cervical posterior longitudinal ligament was investigated with the electron microscope. The posterior longitudinal ligament was composed of bundles of collagen fibers intermingled with occasional fibroblasts and rare blood vessels. Some ligaments contained matrix vesicles in the vicinity of degenerated cells. Hydroxyapatite crystals were frequently precipitated within the matrix vesicles. These findings are similar to the fine structure of the early stage of calcification in normal and pathological calcifying tissues described previously. In this study, the calcification process of the posterior longitudinal ligament suggests that matrix vesicles originate from degenerated cells, and acquire hydroxyapatite crystal deposits. Some eventually coalesce to form a large calcifying mass. Substantial amounts of collagen fibers comprising the ligament may serve an important role in orienting apatite crystal precipitation.

Sustained Osteomalacia of Long Bones Despite Major Improvement in Other Hypophosphatasia-Related Mineral Deficits in Tissue Nonspecific Alkaline Phosphatase/Nucleotide Pyrophosphatase Phosphodiesterase 1 Double-Deficient Mice

“…Because the PP i -generating effect of NPP1 is augmented by ANK-mediated PP i transport to the extracellular fluid, this could help explain the hypermineralization of ligaments and cartilage seen in humans and mice suffering from a genetic deficiency of ANK. 24,[37][38][39] In summary, new data are presented showing hypomineralization of long bones in Enpp1 Ϫ/Ϫ mice and that this deficit is more severe in the [Akp2 Ϫ/Ϫ ; Enpp1 Ϫ/Ϫ ] double deficiency. The hypomineralization observed in long bones of Enpp1 Ϫ/Ϫ mice may be related to relatively lower levels of endogenous NPP1 expression throughout the long bones.…”

Histological Changes of Ligamenta Flava in ‎lumbar Disc Herniation and Spinal Canal ‎stenosis

“…The greater frequency of calcified areas in stenotic patients could be related to the greater tendency of the tissue to undergo chondroid metaplasia or the greater amount of necrotic cells in these patients. Postacchini et al 18 , in his study found that the matrix vesicles originating from necrotic cells, in fact, were the initial calcification site in calcifying connective tissues, including the ligamentum flavum 3,4,19,20 . In our study, Cellular debris originating from necrotic cells, in fact, was the initial calcification site in calcifying areas.…”

“…n the last decades, several studies have analyzed the microscopic morphology of ligamenta flava. However, some studies were carried out in animals 1,2 , whereas others have concentrated on normal human ligaments or the calcification processes in ligamenta flava of the cervical spine 3,4 . Only three investigations have analyzed the microscopic morphology of ligamenta flava in patients with I lumbar disc herniation or spinal stenosis.…”