Hand workload, computer use and risk of severe median nerve lesions at the wrist.

OBJECTIVE To evaluate the effect of hand workload, especially computer use, on the incidence of severe, idiopathic median nerve lesions at the wrist (MNLW) in patients with idiopathic CTS. METHODS Data were prospectively collected for 444 patients with classic or probable CTS who were of working age and referred to our electrodiagnostic (EDX) laboratories. Clinical items recorded were age, gender, intensity of hand workload, BMI and bilaterality of the MNLW. EDX data recorded were results of needle examination of the abductor pollicis brevis (APB), distal motor latency (DML) to the APB and orthodromic sensory conduction velocity. MNLW was considered severe if the DML to the APB was ≥6.0 ms. Patients were divided into two groups: those exhibiting at least one severe MNLW or not. They were classified into three categories according to occupational activity related to the intensity of hand workload: (i) non-workers (reference category); (ii) white-collar workers using computers; and (iii) blue-collar or manual workers. We determined factors associated with severe and non-severe MNLW. RESULTS We investigated 92 patients with 119 severe MNLW and 352 with 589 non-severe MNLW. The risk of severe MNLW was similar for non-workers and blue-collar workers and was 2.5-fold higher than for workers using computers [adjusted odds ratio = 0.41; (95% CI)] after adjusting for age, gender and BMI. CONCLUSION Workers who use computers, who represent, in many countries, a large number of compensation claims, have a lower risk of severe MNLW as compared with blue-collar workers and also non-workers.