Study On The Prevalence Of Low Back Pain In Foundry Workers And Its Risk Factors

Low back pain is a common musculoskeletal disorder. It is the first most common reason for visits to orthopedics, and third most common reason for surgery. Low back pain can be caused by injury, infection, degeneration, dysplasia, tumors and others. But occupational related low back pain are mainly caused by injury and degeneration, and the main features are pains and function restrictiveness, which lead to weakened work ability and downgraded daily life quality, even disability and cost a lot of money.Foundry has been one of the basic industries for centuries. It is regarded as an occupation with worst working environment. Although the working environment has improved for some degree with the development of industrial mechanization and automation, the problem of the safety and health of workers are still serious, especially for those with heavy work, who face many risk factors of musculoskeletal disorder.The current study revealed that the low back pain is highly related with exposure to ergonomic work place factors such as heavy work, lifting and overexert ion, bending and twisting, whole body vibration and static work postures. The health studies in foundry industry in the past, however, are mainly focused on the assessment of the physical and chemical hazards, or are limited to the investigation of musculoskeletal symptoms. Given that those factors have a composite effect, the distribution of the prevalence of the musculoskeletal disorder and its risk and contributing factors need to be explored.ObjectiveUsing cross-sectional epidemiology to examine and analyze the characteristics of the low back pain and its related consequences in foundry workers; conducting ergonomic audit of the work place factors, and then use work posture analysis to measure the different factors observed during physical work activities when completing the work tasks. Those results can then be used to assess the relationship between the physical load exposure effects and the low back pain, and further to reveal the high-risk occupations leading to low back pain in foundry, and thus to provide guidelines for improving working conditions of foundry workers and for preventing from low back pain. Subjects and Methods1 Subjects under investigation: Randomly sample three foundry factories in the Cixi city as on-site examination places, the qualified workers need to be employed for more than 12 months without any serious internal diseases and trauma. The total sample size is 617 workers, which are divided into four groups of auxiliary workers, lathe operators, cleaners and molders.2 Physical examination of the workers: Examined by an orthopedic surgeon, examination including palpation, sports function, sensory function and neural reflection.3 Questionnaire: Based on Nordic Questionnaire (Northern European standard questionnaire for the analysis of musculoskeletal symptoms), with additional questions such as the main features, timing, and contributing factors of the low back pain, the questionnaire is conducted by trained examiners.4 Measurements of the intensity of the pain: Using 3 different methods, i.e., visual analogue scales (VAS), verbal rating scales (VRS), and 6-point behavioral rating scales (BRS-S) to measure the intensity of the pain in workers with low back pain within past one year.5 Ergonomic work place analysis: systematic ergonomic audit of work place factors for the 4 groups in foundry using ergonomic work place analysis according to 14 different items including: working site, general physical activity, lifting, work posture and movement, accident risk, job content, job restrictiveness, worker communication, decision making, repetitiveness of work, attentiveness, lighting, thermal environment and noise.6 Method for the evaluation of postural load in foundry workers: using split-second observations to reveal the subject's posture in auxiliary workers, lathe operators, cleaners and molders. The OWAS analysis system, recommended by Finnish Institute of Occupational Health, with additional fine back postures, is used to analyze the work postures. Additional work phase and work tool related codes are added. The weight of each individual posture component is then calculated, and finally the individual posture and composite posture levels are determined.7 Assessment of the individual physical loads exposure: The posture index, loading index and manual operation index are determined based on foundry workers' work postures, loads and work phases. Those indexes are then multiplied by employment years to give the different kinds of physical loads of an individual, which are summed up to get the relative estimate of the physical loads of each worker. It is called physical load exposure index, which is a weighted index taking into consideration of postures, loads and manual operation factors.Results1 The prevalence of the low back pain: Results from orthopedic examination show that the workers have normal sensory and normal muscle strength. Only 3 positive cases are identified in straight leg lifting and extra-intense tests. The main features in positive cases are point tenderness in neck and back, with the highest prevalence of 29.2% of low back pain among all kinds of pains of the body parts in past year, followed by the pains in shoulders, neck and wrist. It shows the same trend in all kinds of workers. The overall prevalence in occupational low back pain is 23.3%, with the highest 29.9% in molders.The OR value of low back point tenderness in cleaners and molders are 6.16 and 11.90 respectively, and the OR value in their occupational low back pain are 2.13 and 2.56 respectively. There is no difference in the OR value of low back pain in all workers. After removing noise with Mantel-Haenzel method, the trend doesn't change among different sex groups; the OR value increases with the age or employment years.2 Intensity of the low back pain: the intensities measured from 3 different methods are all below medium level.3 Contributing and risk factors of low back pain: Overexertion, repetition and awkward posture are the top 3 contributing factors with a percentage of above 80% over all other factors. The risk factors that show up in the regressive model include smoking, lifting and use of vibration tools.4 Work place and postural analysis results: Molders have the most exposure to workplace factors including overexertion, heavy lifting, awkward work postures and movement, repetition and noise. Molders and cleaners need to correct the 3rd-level single posture as soon as possible. Cleaners have the highest percentage (52.6%) of 3rd-level+ composite posture, followed by molders (30.3%) and lathe operators (11.1%), and auxiliary workers the least (3.3%).5 Physical load exposure index: Molders have the highest with an average of 296.4, which is 10 times of that in auxiliary workers, and 2 times of that in lathe operators and cleaners. The prevalence of the occupational low back pain increases with individual physical load exposure index. Conclusion1 Cleaners and molders have the most serious low back pain symptoms among all foundry workers. The contributing factors include overexertion, repetition and awkward work postures. Risk factors include smoking, lifting, and use of vibration tools.2 Molders have the most exposure to ergonomic workplace factors, including overexertion, heavy lifting, awkward work posture, repetition and noise, over 85% work postures are unnatural postures.3 The prevalence of occupational low back pain increases with the individual physical load exposure index. Molders have the largest physical load exposure.Based on the results from the epidemiology investigation and the ergonomic evaluation, the group of molders has the highest risk of low back pain in foundry.