Vascular Pathologic Changes in the Flexor Tenosynovium (Subsynovial Connective Tissue) in Idiopathic Carpal Tunnel Syndrome

Principal Investigator: Peter C. Amadio, M.D.
Project Coordinator: Chunfeng Zhao, M.D. — zhao.chunfeng@mayo.edu

Figure 1: Control vs CTS (black color-elastin)

The histological features of the flexor tendon sheath in idiopathic carpal tunnel syndrome (CTS) typically reveal a non-inflammatory fibrous connective tissue, with thickening of the tendon sheath, fibrosis, edema, thickening of vessel walls, intimal hyperplasia, and thrombosis. These findings support the view that pressure in the carpal tunnel and ischemia are important factors in the etiology of idiopathic CTS. Elastin has an unanticipated regulatory function during arterial development, controlling proliferation of smooth muscle and stabilizing arterial structure. The purpose of this study was to histologically examine the vascular changes of the subsynovial connective tissue (SSCT) in patients with idiopathic CTS, compared with cadaver specimens as control, especially with regard to the amount and localization of elastin. The CTS patients had more vessels per unit area and thicker blood vessels but lower density of elastin within the vessels and around the vessels (Fig. 1).

These findings suggest that in patients with CTS the fibrosis of the SSCT has altered the gliding characteristics of the tendons, which may affect their ability to effectively and efficiently transmit load to the fingers, or to glide independently from each other, or from the nearby median nerve.