The Evolution of Carpal Tunnel Syndrome

Carpal tunnel syndrome (CTS) has long been one of the most common work-related disorder as well as the most prevalent peripheral neuropathy. The syndrome is characterized by the weakness in the thumb, index and middle finger, numbness, tingling and even paralysis due to muscle atrophy. These symptoms result from the compression of the median nerve. There are many causes traditionally associated with the disorder including trauma, overuse and systemic conditions. While a great deal of information is known on the disorder, and in the recent years many steps have been taken and have been sucessful at reducing the disorder, the prevalence and cost to society is still very high. By re-examining the data using an evolutionary perspective to understand why the carpal tunnel is susceptable to the disorder compared to other species and what are current human patterns that increase an individual’s chance of developing CTS, the causes of the disorder can be better understood and more prevenative actions can be taken.

The wrist is made up of eight carpal bones which articulate proximally with the radius and ulna of the forearm and distally with the metacapals of the hand. The carpal bones are aligned in two rows. The proximal row containing the scaphoid, lunate, triquetral and pisiform and the distal row which consists of the trapezium, trapezoid, capitate and hamate. The ventral side of the carpal bones creates a concave cavity. This cavity is known as the carpal tunnel. The tunnel is formed by the the transverse carpal ligament (TCL) which stretch across the top of the carpal bones (Fig.1.) .

http://www.ortho-md.com/images/proceduresImg/Wrist1.jpg

Fig.1.

The TCL is a thick inflexible connective tissue that a...

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