Pathologic Changes of Blood vessels and Extracellular Matrix in the Subsynovial Connective Tissue of Idiopathic Carpal Tunnel Syndrome

Oh, Jin Rok; Hwang, Sung Kwan; Kim, Yong Min; Sim, Young Joon

Abstract

PURPOSE
The purpose of this study is to investigate pathologic changes of blood vessels and perivascular tissue in subsynovial connective tissue (SSCT) of idiopathic carpal tunnel syndrome (CTS) by examining elastin distribution and vascular morphology and by observing ultrasturctural changes of extracellular matrix using transmission electron microscope (TEM).
MATERIALS AND METHODS
The Verhoeff-van Gieson stain was used to identify histopathology and to localize elastin in the SSCT of the middle finger flexor digitorum superficialis (FDS) within the carpal tunnel in ten CTS patients and ten cadaver specimens as control group. In each specimen, the elastin density within and around vessels was calculated with image analyzing software including Adobe photoshop 6.0 and Scion image analysis. The vessel number per unit area and the mean thickness of vessel walls were also calculated. The ultrastructural changes of SSCT were compared between the specimens of both groups by TEM.
RESULTS
The mean elastin density within vessels was 0.10 +/- 0.03 (p=0.001) in the CTS group and 0.18 +/- 0.04 in the control group. The mean elastin density around vessels was 0.15 +/- 0.04 in the CTS group and 0.23 +/- 0.04 in the control group (p=0.002). The mean number of vessels per unit area (0.00155 mm2) was 0.36 +/- 0.12 in the CTS group and 0.15 +/- 0.10 in the control group (p=0.002). The mean thickness of blood vessels was 38.10 +/- 20.60 micrometer in the CTS group and 18.90 +/- 3.68 micrometer in the control group (p=0.023). In general, the severer the vascular hypertrophy and obstruction, the less elastin noted within and around blood vessels. The TEM showed some important ultrastructural changes in SSCT of CTS. Generally, SSCT contained two kinds of cells, fibroblast-like cells and macrophage-like cells. And these cells and elastin were dispersed among collagen fibrils. In SSCT of control group, the collagen fibrils showed round margin and uniform diameter in transverse section, and showed similar thickness in longitudinal section. However, in SSCT of CTS, the collagen fibrils had irregular margin called "spiraled collagen"and variable diameter in transverse section, and uneven thickness in longitudinal section. In addition, the elastolysis and the phagocytosis of the changed collagen fibrils were observed.
CONCLUSION
SSCT of CTS showed significant decrease of elastin density within and around vessels along with degenerative histopathological vascular changes. In addition TEM revealed ultrastructural abnormalities like metamorphosis of collagen fibrils, phagocytosis of spiraled collagen fibrils and elastolysis. Therefore, it is suggested that pathology of CTS may involve active cellular processing related to ischemic cellular environmental changes in carpal tunnel as well as well known pathology of nerve.