The role of proteoglycans in idiopathic carpal tunnel syndrome.

Decompression of the carpal canal is the most common hand surgery performed in the United States. Hand surgeons perform 460,000 carpal tunnel releases (CTR) each year, which cost the medical industry in excess of two billion dollars per year. The focus of this investigation was to identify the changes, which occur in the flexor tenosynovium of patients undergoing CTR at the connective tissue level. The connective tissues determine the amount and arrangement of macromolecules (fibers, proteoglycans, and glycoproteins) in the extracellular matrix. The proteoglycans are soluble macromolecules that have both structural and metabolic roles. Glycoproteins help to form the interstitial space, basement membrane and function as cell surface receptors. The mechanical function of the proteoglycans includes stabilization of the collagen fibers as well as function in the hydration of the tissues. It has been previous shown that changes in the oxygen concentration at the tissue level can alter the proteoglycans profile of the tissue. During periods of hypoxia, such as those obtained during repetitive motion CTS; the glycolytic pathway acts as the energy source for the tissue. Productions of chondroitin sulfates are a process consumes NAD and would be potentially toxic to the cells under anaerobic conditions. Production of keratan sulfate is NAD sparing product, and may act as a survival pathway for cells under adverse conditions. The disruption in the proteoglycan balance will allow for alterations in the ECM and changes in hydration status of the tissues may have serious implication in CTS because the carpal canal is anatomically very narrow and increases in volume within the canal can result in further compression of the nerve. Flexor tenosyioum was obtained from patients undergoing CTR and compared with control tissue for dermatan, keratan and chondroitin sulfate. The results show a greater density of keratan reactivity in CTS tissues identified by immunostaining. In addition to changes in proteoglycan content there was also an increase in new vessel formation in the CTS tissues. The data obtained suggests that the shifts in the proteoglycan ratios may render the tissues less able to withstand the compressive forces and therefore allow for more force to be placed on the median nerve within the carpal canal.