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Pathogenesis of calcium crystal deposition in the ligamentum flavum correlates with lumbar spinal canal stenosis

T. Yayama, H. Baba, N. Furusawa, S. Kobayashi, K. Uchida, Y. Kokubo, S. Noriki¹, Y. Imamura¹, M. Fukuda¹

Division of Orthopaedics and Rehabilitation Medicine, Department of Surgery, and ¹Division of Tumour Pathology, Department of Pathological Sciences, University of Fukui Faculty of Medical Sciences, Fukui, Japan.

ABSTRACT
Objective
To investigate the histological and immunohistochemical properties of degenerative changes and calcium crystal deposition in the lumbar ligamentum flavum.

Methods
We examined the ligamentum flavum harvested from 119 surgical cases with symptomatic lumbar spinal stenosis. Sections of the ligament were examined by scanning electron microscopy (SEM), energy dispersive X-ray micro-analysis, and were immunostained for S-100 protein, vascular endothelial growth factor (VEGF), basic fibroblast growth factor (bFGF) and CD34. The results were compared with those of ligament tissue harvested from 10 cases of lumbar disc herniation.

Result
The elastic fibres of the ligamentum flavum showed regular, or sometimes irregular, and fragmented fibre bundles. Large areas of fibrosis with reduced elastic component and increased collagenous tissue were frequently seen in the degenerated ligaments. Calcium crystal deposits were observed in these fibrous ligaments, associated with many hypertrophic chondrocytes, and with small blood vessel formation. These chondrocytes stained positively for S-100 protein, VEGF and bFGF. Calcium pyrophosphate dihydrate crystals were identified in the calcium deposit area.

Conclusion
We believe that rupture of elastic fibre bundles is the first change to occur in degeneration of the ligamentum flavum. Calcium crystal deposition was seen within these fibrous and chondrometaplastic areas. Hypertrophic chondrocytes regulate crystal formation and tissue reconstruction by secreting cytokines.

Key words
Ligamentum flavum, elastic fibre, calcium crystal deposition.

Please address correspondence to: Takafumi Yayama, MD, Division of Orthopaedics and Rehabilitation Medicine, Department of Surgery, University of Fukui Faculty of Medical Sciences, Shimoaizuki 23, Matsuoka, Fukui 910–11, Japan.
E–mail: yayama@fmsrsa.fukui-med.ac.jp