Work‐related carpal tunnel syndrome: What's important?

Normally, an editorial discusses the background of reasonable work, its scientific merits, and then the context of its findings. The main point in the study by Thiese et al. in this issue of the journal, regarding the association between wrist ratio and carpal tunnel syndrome (CTS) and its effect modification by obesity, is almost totally beside the point in the larger context. Focusing on an arbitrary measure of wrist anthropometrics redirects focus from higher risk occupational factors, obfuscating useful and potentially preventable measures, in favor of creating “diagnostic” cut-points of debatable value. So, let us turn things around a bit and start from that context. The National Institute of Occupational Safety and Health, in 2000, funded a consortium of 6 centers to track more than 3,500 workers across regions of the USA to try to determine, prospectively, risk factors for work-related upper extremity musculoskeletal disorders (WRUEMSKs). The main purpose of these studies was to clarify, after years of heated debate, the relative contribution of various types of common physical work exposures and the risk of incident WRUEMSKs. Being a prospective cohort study, it promised to offer some of the most valid information to date, at least indirectly offering a clearer window into the causation of these disorders. In general, these studies were carefully done and, in spite of some heterogeneity in how each center conducted the studies, common case definitions of some of the WRUEMSKs, including CTS, were implemented across the 6 centers. The consortium CTS case definition included both typical symptoms and signs, and nerve conduction studies. This is a key point: a proper case definition of CTS for research purposes requires appropriate symptoms and signs and electrodiagnostic studies (EDX). This may be particularly critical for CTS cases in the workers’ compensation policy arena. Outcomes of various surgical procedures tend to be much worse in workers’ compensation than in non–workers’ compensation populations. Harris et al. included 10 studies of CTS, with the compensation patients experiencing a >4-fold increase in unsatisfactory outcomes compared with the non-compensation patients. In addition, 47% of hand surgeons reported in a national survey that, if CTS symptoms are typical and there is a positive response to steroid injection, there is no need to conduct EDX before performing CTS surgery. These types of results regarding poorer outcomes of CTS surgery in workers’ compensation, and attitudes of orthopedic surgeons, has led the Industrial Insurance Medical Advisory Committee of the Washington State Department of Labor and Industries to mandate EDX in combination with appropriate symptoms and signs for CTS before authorizing surgical decompression for work-related CTS. Greater specificity is warranted when a normally effective CTS decompression procedure is considered in an injured worker population. Thus, in workers’ compensation systems, abnormal EDX findings alone are not sufficient to corroborate a diagnosis of CTS. Abnormal EDX results alone are fairly common, and only 23% of workers with abnormal EDX alone followed prospectively eventually develop true CTS. In addition, some investigators have shown that testing for EDX post-offer but pre-employment is not a worthwhile endeavor. Dale et al., in a large retrospective cohort study of 1,648 newly hired manufacturing production workers, showed no association between abnormal pre-placement EDX results and incident CTS; they concluded that EDX screening is ineffective as a preventive strategy for CTS. The study by Thiese et al., from 2 consortia centers among the 6 centers originally funded to conduct a large prospective study of risk factors for CTS, reports negative findings related to physical risk factors and CTS. None of the specific findings Correspondence to: G.M. Franklin; e-mail: meddir@uw.edu