Thoracic ossification of the human ligamentum flavum: histopathological and immunohistochemical findings around the ossified lesion.
OBJECTIVE
The object of this study was to histopathologically and immunohistochemically characterize ossification of the ligamentum flavum (OLF) in samples of the thoracic spine harvested en bloc during surgery and to enhance the understanding of the ossifying process, particularly calcification and ossification.


METHODS
Samples of OLF plaque were obtained en bloc from 43 patients who underwent posterior decompression. The histopathological findings were correlated with radiological subtypes using computed tomography. The expression of type I and type II collagens, vascular endothelial growth factor (VEGF), transforming growth factor (TGF)beta, and bone morphogenetic protein (BMP)-2 was investigated.


RESULTS
Surgical decompression using the posterior floating and en bloc resection technique resulted in neurological improvement in 40 of 43 patients. Progression of the OLF lesion longitudinally and medially was associated with significant degeneration of elastic fibers, fiber bundle derangement, decrements in fiber diameter, and fragmentation. Calcification and ossification paralleled the degeneration of the elastic fibers, extended more medially, and fused in the central area. Expression of BMP-2, TGFbeta, and VEGF was significant in chondrocytes in the calcified cartilage and fibrocartilage layers, especially around the calcified front.


CONCLUSIONS
Histopathologically, the progress of calcification and ossification was closely associated with the degeneration of elastic fibers and with significant expression of BMP-2, TGFbeta, and VEGF in the ossification front.
Yayama
Takafumi
T
Departments of Orthopaedics and Rehabilitation Medicine, Fukui University Faculty of Medical Sciences, Fukui, Japan. yayama@fmsrsa.fukui-med.ac.jp
Uchida
Kenzo
K
Kobayashi
Shigeru
S
Kokubo
Yasuo
Y
Sato
Ryuichiro
R
Nakajima
Hideaki
H
Takamura
Takaharu
T
Bangirana
Alexander
A
Itoh
Hiroshi
H
Baba
Hisatoshi
H
D000368:Aged; D055396:Bone Morphogenetic Protein 2; D019485:Bone Morphogenetic Proteins / Q000378:metabolism; D019902:Chondrocytes / Q000378:metabolism; D024042:Collagen Type I / Q000378:metabolism; D024043:Collagen Type II / Q000378:metabolism; D019299:Decompression, Surgical; D018450:Disease Progression; D004547:Elastic Tissue / Q000473:pathology; D005260:Female; D006801:Humans; D007150:Immunohistochemistry; D017843:Ligamentum Flavum / Q000000981:diagnostic imaging / Q000601:surgery; D008297:Male; D008875:Middle Aged; D009422:Nervous System Diseases / Q000209:etiology; D009999:Ossification, Heterotopic / Q000150:complications / Q000000981:diagnostic imaging / Q000378:metabolism* / Q000473:pathology*; D013904:Thoracic Vertebrae; D014018:Tissue Distribution; D014057:Tomography, X-Ray Computed; D016212:Transforming Growth Factor beta / Q000378:metabolism; D042461:Vascular Endothelial Growth Factor A / Q000378:metabolism
C525718:BMP2 protein, human; D055396:Bone Morphogenetic Protein 2; D019485:Bone Morphogenetic Proteins; D024042:Collagen Type I; D024043:Collagen Type II; D016212:Transforming Growth Factor beta; D042461:Vascular Endothelial Growth Factor A