Annals of Occupational and Environmental Medicine

Original Article

A Case of Cubital Tunnel Syndrome Due To Repetitive Work: Jung Il Kim, Young Il Lee; Korean Journal of Occupational and Environmental Medicine 2006;18(2):156-162. Published online June 30, 2006; DOI: https://doi.org/10.35371/kjoem.2006.18.2.156

Abstract PDF: OBJECTIVE: To report one case of cubital tunnel syndrome due to repetitive work METHOD: The authors examined a worker who complained of severe muscle atrophy between the right thumb and index finger, claw deformity and numbness of the 5th finger. We evaluated him with physical examination, neurophysiologic studies (nerve conduction study, NCV; electromygraphy, EMG), plain Xray and magnetic resonance image(MRI) at the right elbow. We also investigated his occupational history, and analyzed his work motions, using rapid upper limb assessment (RULA) of the work cycle at his previous work site.
RESULT
The patient had been a ship welder for 17 years, followed by 6 years of dismantling boxes and loading/unloading materials. The latter job required inappropriate elbow posture such as repetitive flexion and extension. The NCV study revealed slow conduction velocity of the right ulnar motor and sensory nerve, decreased action potential of the right hand intrinsic muscles and flexor carpi ulnaris. The simple X-ray film showed normal finding, but MRI showed a finding compatible with cubital tunnel syndrome combined with enlargement of the right ulnar nerve at right elbow, 0.6cm intraarticular loose body and medial aspect of the medial epicondyle of the right distal humerus.
CONCLUSION
We confirmed the diagnosis of cubital tunnel syndrome that was related to his packing job which had demanded repetitive flexion and extension of elbow joint. At the time of writing, surgery was being considered as appropriate treatment.

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Original Article

Usefulness of Power Spectral Analysis for Measurement of Local Muscle Fatigue during Keyboard Task: Soon Young Kwon, Chung Yill Park, Jung Wan Koo, Hyeon Woo Yim, Kang Sook Lee; Korean Journal of Occupational and Environmental Medicine 1999;11(4):449-459. Published online December 31, 1999; DOI: https://doi.org/10.35371/kjoem.1999.11.4.449

Abstract PDF: OBJECTIVES
Work-related upper extremity disorders of the tendons, nerves, and musdes associated with. repetitive motion represent an increasing proportion of occupational illnesses, medical services, and workers' compensation costs. Severe local muscle fatigue may be a precursor of repetition strain injuries. The demand for objective and quantitative assessment of local muscle fatigue is now increasing. The purpose of this study is to determine the usefulness of power spectral analysis of individual muscle as one of the objective spectral parameters in quantification of local muscle fatigue.
METHODS
From 10 normal male without neuromuscular dysfuction, motor unit action potentials (MUAPs) of three muscles (upper trapezius, infraspinatus, and anterior deltoid) of left shoulder girdle were obtained. The surface electrodes were used and the changes of power spectrum according to frequency components were calculated per minute during the keyboard task for 30-minute period by power spectral analysis of MUAPs signal.
RESULTS
There was a linear relationship between median frequency (MF) and time flow in the upper trapezius muscle, however the same was not observed in other muscles. The MF slope of the upper trapezius muscle showed a decline of the MF over time and reflected the fatigue rate. Other spectral parameters, such as mean frequency and total power were not significantly correlated to time flow during the keyboard task in all three muscles. And no significant correlation was observed between keying rate and slope of median frequency of upper trapezius muscle.
CONCLUSIONS
Above results suggested that the power spectral analysis on median frequency in upper trapezius muscle would be useful in quantification of local muscle fatigue during the keyboard task and local muscle fatigue of shoulder was affected by static posture, not by keying rate.

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