1. Armstrong, T.J., Castelli, W.A., Evans, F.G., Diaz-Perez, R. “Some histological changes in carpal tunnel contents under bi-mechanical implications.” J of Occupat Med, 1984; 26: 3: 197-201.
This article is the hallmark of incredibly poor pseudo-research. In my mind there has never been a worse article published on the potential association of occupation and carpal tunnel syndrome. The study initially uses as premise the previous studies that show that carpal tunnel syndrome occurs in occupational disease among those who perform repetitive tasks with their hands (this has never been proven). They then looked at cadavers ranging in age from 60-81 years, 3 each male and female cadavers. Overall, I don’t think this article should have ever been written, much less put into print.
2. Birkbeck, M.Q., Beer, T.C., “Occupational relation to the carpal tunnel syndrome.” Rheumatology and Rehab, 1975; 14: 4: 218-221.
This was a poor retrospective survey of 658 patients treated for carpal tunnel syndrome, of which 45% occurred bilaterally with a ration of female to male of 3 to 1. Overall, this study added nothing useful to the medical literature on carpal tunnel syndrome except confirming the frequently cited 3 to 1 female to male incident and the high bilaterality of the problem/b. Their diagnosis was confirmed on median motor conduction studies only, i.e. this meant that the majority of them had long standing CTS by the time of diagnosis and treatment. Only 49% were treated definitively with surgery. Supposedly 79% were doing “repetitive hand movements” at work. They noted that of the 492 women in this survey, 28% gave knitting as their main hobby, and this accounted for 51% when non-employed housewives were considered separately. Without specific reason with which to make this conclusion, the author summarized that even light, but highly repetitive movements of the fingers and wrists are likely to produce changes that cause carpal tunnel syndrome. They failed to explain why there are 3 times as many women in their series and they had no control in their series, plus it was retrospective. Additionally, the issues related to the patient selection were not addressed.
3. Falck, B., Aarnio, P. “Left-sided carpal tunnel syndrome in butchers.” Scand J Work Environ Health, 1983; 9: 291-297.
Poor case review. They were notable in noting that often there is a diffuse pain in the shoulder region of people treated for carpal tunnel syndrome. This study was prompted by having treated 2 butchers had undergone carpal tunnel release for their non-dominant hand. They went on to study butchers only from 2 slaughterhouses, i.e. selection biased. All participants were butchers, meat cutters were not included, and thus it is not clear how to translate this occupation from the country in which it was performed to the United States, where the term butcher is not even utilized anymore. The key issue is that all of them were described as heavily built, muscular, and to varying degrees obese. The body mass index of every butcher in the study was in the overweight or obese category, i.e. BMI greater than 25. Only 4 of their subjects would not have been considered over-weight using body mass index. The mean age was well over age 30. Those that developed and those that did not develop CTS in the limited study group, i.e. 19 butchers, worked in the field on the average of the amount of time. 53% had signs and positive NCS for CTS on their non-dominant hand. Clinical tests for CTS, i.e. physical tests, were considered rarely positive. They concluded that the time spent working, as a butcher, as well as the age of the butchers did not correlate with carpal tunnel syndrome. They tried to explain this by stating that this lack or correlation may be that those who have had symptoms may have moved on to other types of jobs. This type of selection is indicated by the fact that all 4 of the subjects who had been butchers for more than 30 years were free of subjective symptoms. They felt that the clinical tests proved to be of limited value for the diagnosis of the syndrome and the operation was simple and could be done under local anesthetic resulting in permanent relief of the symptoms. Overall, this was a nice study for looking at the problem of carpal tunnel syndrome-the physical characteristics of the people who present, the limitations of physical findings, the need to perform nerve conduction studies when evaluating a person and the ability to return to work in addition to the high frequency of involvement of the non-dominant hand. It is also notable for the consideration of natural selection that may occur in workers to leave jobs that they don’t find suitable based on physical characteristics, whereas those that don’t have mechanical complaints from their occupation may stay on their job indefinitely. There was no specific association with CTS and handedness in this report.
4. Feldman, R.G., Travers, Hyland, P., Chirico- Post, J., Keyserling, W.M. “Risk assessment in electronic assembly workers: Carpal tunnel syndrome.” JHS, 1987; 12: 849-855.
This without a doubt one of the most poorly performed, flawed studies that has ever been reported on attempting to tie workers and their tasks into development of CTS. This article has really not value for the educated reader, other than to demonstrate the severity of flaws that occur in typical study suggesting an occupational causation of CTS and/or the potential benefits of ergonomic modifications. One must be ever vigilant to not accept information from this type of poor quality source. Not only did the authors have a very low inclusion rate in evaluating workers at a given plant, i.e. just over 500 in a plant with over 700 workers, they then tested only a very small segment of them using an incomplete form of a test for entrapment neuropathy. Subsequent follow exam a year thereafter, they had further sampling error, testing 25% less of the already meager tested worker population. The workers were not matched for age, sex, handedness, or hours at work or duration of employment. The authors then attempted to ascribe problems with their job and the development/progression of signs and symptoms of carpal tunnel syndrome to their tasks. In the discussion section of their article, the authors then went on not only to make conclusions that were not validated by their study format, but they went on to make many grossly erroneous treatments regarding Raynaud’s syndrome and CTS, etc.
5. Waring III, W.P., Werner, R.A. “Clinical management of carpal tunnel syndrome in patients with long-term sequelae of poliomyelitis.” JHS, 1989; 14A: 885-869.