Ergonomics Expert Witness On Carpal Tunnel Syndrome Part 1

Ergonomics expert witness John D. Lloyd, Ph.D., M.Erg.S., C.P.E., writes on Carpal Tunnel Syndrome (CTS):

First described by Sir James Paget in 1865, carpal tunnel syndrome (CTS) is the most common example of a nerve compression disorder. Other terms used to describe this disorder include: writer’s cramp, occupational neuritis, partial thenar atrophy, and median neuritis.
is caused by restriction of the median nerve as it passes through the carpal tunnel, an anatomic space in the wrist bound on the palmar side by the inelastic transverse carpal ligament and on the dorsal aspect by the carpal bones. The 10 structures that transverse the carpal tunnel include the four tendons of the flexor digitorum superficialis, the four tendons of the flexor digitorum profundus, the flexor pollicis longus and the median nerve.

Robbins (1963) suggests three possible alternatives by which the cross-sectional area of the carpal tunnel may be compromised, thus reducing the available volume through which soft tissue structures pass:
1. Increase of volume of the contents of the carpal canal 2. An alteration of the osseus trough 3. Thickening of the transverse carpal ligament
The tendons which form a bridge between metacarpals in the hand and the flexor muscles of the forearm are lubricated along their path by tenosynovium, which allows the tendons to glide against each other. Personal factors or occupational conditions which cause irritation to or inflammation of the tendons can result in swelling and thickening of the tenosynovium. Since the median nerve is fragile compared to the surrounding structures, it compresses as the tendons swell, producing symptomatic experience of CTS.

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