Validation of the Revised Strain Index for Predicting Risk of Incident Carpal Tunnel Syndrome in a Prospective Cohort

Abstract

The Revised Strain Index (RSI), a model that quantifies physical exposure from individual hand/ wrist exertions, tasks, and multi-task jobs, was used to quantify exposure for 1372 incident-eligible manufacturing, service and healthcare workers. Workers were followed for an average of 2.5 years (maximum 6 years) and had an average carpal tunnel syndrome (CTS) incidence rate of 4.6 per 100 person-years. Exceeding the a-priori RSI limit of 10.0 showed increased risk of CTS (Hazard Ratio (HR) ¼ 1.45, 95% CI: 1.11-1.91, p ¼ 0.01). There also was a dose-response relationship using proposed low (RSI 8.5, HR ¼ 1.00), medium (HR ¼ 1.42 (95% CI: 0.96-2.09, p ¼ 0.08)), and high limits (RSI > 15, HR ¼ 1.79 (95% CI: 1.19-2.69, p ¼ 0.01), respectively. RSI as a continuous variable showed CTS risk increased steadily by between 1.9% and 3.3% per unit increase in RSI (p 0.03). These results suggest that the RSI is a useful tool for surveillance as well as for job intervention/design and continuous improvement processes. Practitioner Summary The Revised Strain Index (RSI) quantifies physical exposure from individual hand/wrist exertions, tasks, and multi-task jobs. Increased cumulative RSI scores (i.e. daily exposure score) are associated with increased risk of carpal tunnel syndrome (CTS). The RSI is potentially useful as a risk surveillance and intervention design tool.

Work‐relatedness of carpal tunnel syndrome: Systematic review including meta‐analysis and GRADE

“…The remaining 97 articles were assessed in our full‐text screening. In total, 17 studies 9 , 24 , 25 , 26 , 27 , 28 , 29 , 30 , 31 , 32 , 33 , 34 , 35 , 36 , 37 , 38 , 39 were included and 12 of these studies were enrolled in our meta‐analysis. Three studies 26 , 28 , 29 used the same pooled cohorts with the same participants and because of that we chose study 27 with the most participants in the meta‐analysis.…”

“…All the studies are prospective cohort studies and were published between 2001 and 2021. The included studies were conducted worldwide with eight studies in the United States, 25 , 26 , 27 , 28 , 29 , 31 , 32 , 36 two in France, 9 , 33 three in Italy, 24 , 38 , 39 two in Finland, 30 , 37 one in Denmark, 34 and one in both the United States and France. 35 The total number of included workers was 1,051,707 and were all 18 years of age or older.…”

“…Six studies studied the association between the ACGIH Threshold Limit Values (TLV) and the incidence of CTS 24 , 25 , 27 , 32 , 38 , 39 ; four studies assessed the association between repetition and the incidence of CTS 26 , 28 , 29 , 39 ; Four studies studied the association between force duration and the incidence of CTS 25 , 26 , 28 , 29 ; Four studies assessed the association between vibration and the incidence of CTS 28 , 30 , 36 , 37 ; six studies assessed the association between force intensity and the incidence of CTS 26 , 28 , 29 , 33 , 34 , 39 ; two studies assessed the association between wrist bending posture and the incidence of CTS 9 , 28 ; three studies assessed the association between pinch gripping and the incidence of CTS 9 , 33 , 37 ; two studies assessed the association between computer/keyboard use and the incidence of CTS 35 , 36 and finally, two studies studied the association between a high Strain Index (SI) and the incidence of CTS. 27 , 31 The characteristics of the studies are described in Appendix 2 .…”

“…The SI is an index that assesses the physical exposure of the distal upper extremities based on frequency, duration, intensity and hand/wrist posture. 43 Kappellusch et al 31 defined the high exposure as SI > 10 and Garg et al 27 defined the high exposure as SI > 6.1 This meta‐analysis showed that there was high‐quality evidence that high exposure of SI is significantly associated with an increased rate of the onset of CTS (HR 1.58, 95% CI 1.09–2.30) (Figure 2H ).…”

Analysis of the Reduction of Ergonomic Risks through the Implementation of an Automatic Tape Packaging Machine

“…The standard ISO 11228–3:2007 recommends (SI) as a good method for an analytical evaluation [ 13 ]. The main objective of the methodology is to evaluate the risk of biomechanical overload related to repetitive movements, taking into account the forces applied by the hands and the postures adopted by the wrists during the work activity [ 14 ]. In [ 15 ], the SI was applied in the context of blacksmith jobs in Khorda district in Odisha (India) to review the status and discomfort levels of the village craftsmen manufacturing the agricultural appliances.…”