Heavy keyboard use leads to changes in typists’ hands

December 22, 2004

If ever I undergo an imaging examination of my hands and wrists, the radiologist will need to know that increased fluid in my second and fifth flexor sheaths is probably quite normal because I am a regular typist.

If ever I undergo an imaging examination of my hands and wrists, the radiologist will need to know that increased fluid in my second and fifth flexor sheaths is probably quite normal because I am a regular typist.

A scientific poster at the RSNA meeting by researchers from King's College Hospital in London described the use of ultrasound to assess peritendinous fluid in the hands and wrists of asymptomatic individuals.

Previous studies have documented signs of tenosynovitis and carpal tunnel syndrome in people whose jobs involve repetitive hand use. On ultrasound, the presence of peritendinous fluid and tendon thickening is used to diagnose tenosynovitis. But because the presence of this fluid in the hand and wrist tendons has been documented in asymptomatic individuals, the clinical significance of this finding alone remains unclear.

The King's College team, led by V.R. Stewart, recruited 19 typists and 14 controls from among hospital staff members and their families. To qualify as typists, individuals had to have typed for more than 15 hours a week for at least six months, whereas the controls must have typed for less than 2.5 hours per week over the same period. Subjects with any history of other significant repetitive hand use, previous surgery or injury to the hand and forearm, connective tissue disease or arthritis, renal disease, diabetes, recent steroid therapy, and current pregnancy were excluded.

Ultrasound examinations were performed by one of the insitution's experienced musculoskeletal sonographers, David Elias, who did not see the results of an accompanying questionnaire. He used a high-resolution 8 to 13-MHz linear array transducer (Aloka Prosound SSD 550).

In all cases, fluid extended over a tendon sheath of under 2 cm. Fluid did not completely surround any tendons in the typists or controls, except in the case of extensor carpi ulnaris (ECU) palmaris longus, which was noted to be absent in 15% (10) of the 66 wrists. Bilateral absence was noted in 9% of subjects.

"Several tendons showed in excess of 1 mm of fluid within their tendon sheaths in controls, particularly the ECU tendon, which demonstrated up to 5 mm of fluid. We found that certain other tendons rarely demonstrated any fluid within their tendon sheaths, and therefore over 1 mm of fluid surrounding these tendons is more likely to be of significance," said the researchers.

With the exception of ECU tendons, circumferential fluid was not present. Thus, the fluid may suggest tenosynovitis on ultrasound. Fluid extended over a length of no more than 2 cm in any of the subjects, and, therefore, more extensive fluid may be suggestive of tenosynovitis.

Another finding was a significant increase in the mean maximum fluid depths for the left extensor pollicis longus and fifth flexor sheath. Because 30 of the 33 subjects were right-handed, this may have been due to the need for relatively increased activity in the nondominant hands of typists compared with controls.

The authors concluded that more studies involving a larger number of subjects are necessary to highlight any further differences between the hands and wrists of typists and nontypists.