C H A P T E R. Assessment of Work-related Musculoskeletal Disorders & Postural Stress. Posture & Stress

Transcription

1 C H A P T E R 3 Assessment of Work-related Musculoskeletal Disorders & Postural Stress Posture & Stress 56

2 3.1. Abstract Background: The goldsmiths used to work in particular working postures for prolonged time. The workers reported to have discomfort in body parts during general health investigation by the WHO-QoL 100 questionnaire. The discomforts were assumed to be the effects of long work hour in static postures. Secondly, the significant predominant postures were also needed to be identified to confirm whether those could actually impart musculoskeletal problems among the workers. Methods: Out of a total 276 screened personnel, 147 actively involved in the jewellery manufacturing units responded to have discomfort. Based on consent, minimum experience criterion and active medical condition, 12 were excluded and 135 personnel were finally recruited. They were categorized as fabricator/manufacturers (n=89), melting staffs (n=14) and polishing/buffing staffs (n=32) according to their specific jobs. A modified version of Nordic musculoskeletal disorder questionnaire was administered to seek information on body parts discomfort and a body parts discomfort (BPD) scale was used to rate the degree of discomfort. The most predominant working postures were analysed using two posture assessment tools, rapid entire body assessment (REBA) and rapid upper limb assessment (RULA). Results: The workers reported discomfort in the trunk, especially the back and waist. Upper and lower back and waist were the three regions where the workers used to maximum discomfort and the trend was continuous among the workers of all the three groups. Over 30% of the manufacturing staffs reported discomfort in these three areas whether the response rates were low in the other two groups. The posture assessment tools identified all the predominant working postures as moderate to high risky. Although the frequency of response varied between the groups and the working postures were found risky, the degree of discomfort did not differ much by job type. Median values of the BPD ratings for all the body parts areas were below the midline value of the scale and none of the regions was found under high stress. Conclusion: As a result of continuous work in sitting posture, the goldsmiths developed musculoskeletal problems in different body parts although the problems were not found alarming. The posture assessment tools although indicated the postures highly risky, those assessment tools were not very much appropriate to evaluate the classical Indian postures. Therefore, there is a necessity to design a posture assessment tool for Indian and Asian ethnic postures. 57

3 3.2. Introduction Acute or chronic musculoskeletal problems among industry workers are generally either the outcomes of improper design of the workstations or long work hours in awkward postures. It has long back been reported by the National Institute of Occupational Safety and Health (NIOSH) that the prevalence of low back pain is mainly due to inappropriate workplace (NIOSH, 1997) and there are innumerable studies, which have also demonstrated that the rates of low back disorders vary greatly by industry, occupation and job type within a given industry or facility. It has earlier been observed that the workers engaged in jewellery manufacturing industries used to work in congested workplaces for a long work hour (Chapter 2). Most of the workstations in this industry are poorly designed and such workstations can also contribute to the probability of work-related musculoskeletal disorders (WMSDs) among the workers. As obtained from the health and quality of life related questionnaire (WHO-QoL 100 questionnaire), the prevalence of body parts discomfort was found significant among the goldsmiths although the responses varied greatly in respect to the degree of severity. It is well-known fact that the knowledge of proper material handling as well as the physiologically suitable posture is lacking in the developing countries and therefore the prevalence of musculoskeletal disorders is very obvious (Asogwa, 1987), especially in the unorganized sectors. Many times, it has also been observed that the discomfort increases with the advancement of age as workers refuse to undertake new ideas of a modern workplace (Acheson, 1972). There are still very few reports available, which have described the healthrelated issues of the workers associated with small-scale jewellery manufacturing industries. Although, some initiatives have been taken till date to evaluate the working postures in several small-scale informal sectors of India, there is merely any significant report that has evaluated the probabilities of work related musculoskeletal disorders among the goldsmiths in a systematic way. This present study was aimed to identify the predominant postures adopted by the goldsmiths and evaluate those postures in terms of severity of risks. Similarly, the feelings of discomfort of the workers for those postures were also evaluated. 58

4 3.3. Objective In this chapter, the postures, which the goldsmiths have adopted for their work, have been scrutinized. The main purpose of the study was to- (i) (ii) (iii) (iv) Evaluate the prevalence of discomfort/pain in any body part due to work. Rate the feeling of discomfort by a discomfort rating scale. Study the postures and identify the awkward ones. Evaluate the awkward postures by standard posture assessment tools. 59

5 3.4. Methods Study population The present study recruited participants from the large population of the goldsmiths screened previously. Detailed information about the recruitment of the study participants were discussed in the previous chapter (Chapter 2). In brief, a total of 276 persons were preliminary screened that included 198 jewellery manufacturing workers and 78 reference personnel who were mainly the sales persons and office workers at the jewellery houses. Of those 198 participants actively involved in the manufacturing processes, 8 had withdrawn from the study. Among the rest, 147 reported to have any discomfort/pain in the body parts during general health study. Out of those 147, 135 personnel were recruited in this study based on the inclusion criteria: (1) having a minimum one year exposure in jewellery industries; (2) not having any serious medical injury/active medical condition in last three months; and (3) willingness to cooperate. Figure 3.1 illustrated the schematic diagram of the selection process of the participants. Sales staffs (n=78) Excluded (n=12) Experience<1 year: n=3 No consent: n=6 Active medical condition: n=3 Fabricators (n=89) Total Screened (n=276) Goldsmiths (n=198) Discomfort reported (n=147) Recruited (n=135) Melters (n=14) Withdrawn (n=8) Polishers (n=32) Figure 3.1. Schematic representation of recruitment of the study participants Recruited participants were categorized as manufacturers/fabricators (n=89), melting staffs (14) and polishing staffs (32) based on their types of job. Working postures adopted by the melting staffs were same as of the polishing staffs and due to very small number of participants from former group they were merged with the polishing staffs. Reference staffs (sales persons and office workers) were not included 60

6 for comparative analysis as they did not have comparable work schedules and working postures like the workshop staffs Anthropometric measurements Height and weight of the participants were measured by standard anthropometric rod and properly calibrated weighing machine respectively. Body mass index (BMI) and body surface area (BSA) were calculated according to the formulae reported previously Questionnaire study An interviewer-administered Nordic musculoskeletal questionnaire was used to seek information about the power and zone of discomforts [Kuorinka et al. 1987]. The questionnaire was translated to Bengali and then back translated into English. The Bengali-translated version of this questionnaire was pre-validated [Sett and Sahu 2010]. The questionnaire contains several open and close-end questions that help acquiring information about discomfort at neck, shoulder, upper and lower back, hand, buttock, knee and ankle before, during and/or after work [Annexure-IV]. Those observational data were analysed further to find out the areas of feeling of maximum discomfort. To rate the degree of discomfort, a body parts discomfort rating (BPD) scale was used [Jacquelin et al. 1994]. It is an 11 point rating scale from 0 to 10, where 0 and 10 indicate no and maximum discomfort at a particular location of the body, respectively. This tool is frequently used to get score-based information of subjective feeling of discomfort by rating in this 0-10 point scale (Figure 3.2). The workers were asked to rate their feeling of discomfort in that scale. The same practice of rating a particular zone of discomfort during a particular work was repeated for each individual for minimum three times after 1 day interval to avoid variability. Deviations of the ratings more than 1% (e.g. if individual s first rating was 5 and second was 3 or 7), were not considered as true score and were eliminated. 61

7 Figure 3.2. Body parts discomfort (BPD) Scale Assessment of the working postures Two standard methodologies, rapid entire body assessment (REBA) and rapid upper limb assessment (RULA) were used to assess the stress of workers for all predominant postures by scoring them according to their severity of stress. REBA was first described by Hignett and McAtamney in the year 2000 and is one of the most widely used posture assessment tools. It is a score-based information assessment tool comprising of items including required or selected body posture, forceful exertions, type of movement or action, repetition, and coupling. Responses of the selected items are given specific scores, which altogether undergo a systematic process to evaluate whole body postural stress and risks associated with job tasks. The REBA worksheet has been provided in the annexure [Annexure-V]. Since, the goldsmiths belonged to sedentary class of workers and their tasks needed more usage of upper limbs (neck, shoulders, arms) compared to the lower limbs (legs), a more proficient posture assessment tool, rapid upper limb assessment (RULA) was used to stratify the postural patterns of the upper limbs only. RULA first described by McAtamney and Corlett (1993) is also a score-based information tool containing items of upper and lower arm position, wrist twist and position and neck and trunk position. Like REBA, this also evaluates the scores systematically for a particular job task. RULA worksheet has also been provided in the annexure [Annexure-VI]. First, all the different tasks were captured into motion pictures using a camcorder (Sony, India). Then, the recordings were freeze-framed and the awkward postures were selected. Freeze-framed images were analyzed using ergonomical 62

8 assessment software, ErgoFellow V2.0 (Brothersoft Inc., USA). REBA and RULA scores were obtained from that software. Stick diagrams of the postures were made for visual perception and critical evaluation of those postures Statistical analyses Demographic measures were presented as means (SD). Comparisons of baseline characteristics between the three groups (fabricators, melting staffs and polishing staffs) included Kruskal-Wallis test for non-normal distributions. Groupwise comparison of feeling of discomfort of a particular body part was analysed by chi-square (χ 2 ) test. Individual responses of body parts discomfort ratings for a particular location of the body during a particular job were obtained from all respondents (average values of the BPD scores were calculated from who responded only) and median value was calculated. Individual responses of discomfort of all body parts during a particular task were also obtained and expressed as median. Level of significance for all pair-wise comparison was taken as P<0.05. All analyses were performed in SPSS (version 20). 63

9 3.5. Results Demographic features Demographic features of the all participants have been presented in Table 3.1. Although, the polishing staffs were of higher age group than the fabricators, the difference did not turn out statistically significant. Although the polishing staffs were having higher BMI than the manufacturing/fabricating staffs (23.5 vs kg/m 2 ), the difference was not found statistically significant. Other anthropometric variables (height, weight and BSA) were found moderately similar among the fabricators and the polishing staffs. Table 3.1. Baseline characteristics of the personnel identified for the study Parameters Manufacturers (n=89) Melting staffs (n=14) Polishing staffs (n=32) P value Age (Year) 36.3 (2.4) 35.8 (2.9) 37.3 (3.8) 0.43 Height (Meter) 1.67 (0.15) 1.70 (0.11) 1.66 (0.18) 0.17 Weight (Kg) 62.4 (5.6) 62.7 (4.1) 63.2 (8.1) 0.29 BMI (Kg/M 2 ) 22.4 (2.5) 21.7 (3.1) 22.9 (2.8) 0.61 BSA (M 2 ) 1.77 (0.26) 1.79 (0.31) 1.77 (0.38) 0.31 Data presented as mean (SD). P values were calculated by Kruskal-Wallis test of nonnormal data. Significance level P<0.05. Abbreviations were mentioned previously Assessment of the questionnaire responses Categorical information of feeling of discomfort by the study participants as assessed from the questionnaire has been presented in the following figure (Figure 3.2). The rates of response for the neck and shoulder regions were moderately higher among the melting staffs (21.4% for each of the regions) compared to the fabricators (12.4% and 5.6% for neck and shoulder, respectively) and the polishing staffs (9.4% and 6.3% for neck and shoulder, respectively) although the difference was not statistically significant (p values for neck and shoulder: 0.52 and 0.11). However, it was observed that the areas of maximum discomfort among the goldsmiths had been upper and lower back and waist. The percentages of discomfort in those areas were higher than all other body parts and the trend was consistent even after stratification 64

10 of the goldsmiths by their job type although the statistical difference between these three groups were not established (P values for upper back, lower back and waist were 0.13, 0.11 and 0.15, respectively). Figure 3.3. Prevalence of body parts discomfort among the goldsmiths by work category Table 3.2. Body parts Complaint of discomfort by the goldsmiths in different body parts Fabricators (n=89) Melting staffs (n=14) Polishing staffs (n=32) N BPD N BPD N BPD Head 7 3 (2-4) (1-2) (1-3) Neck 11 4 (2-6) 3 2 (1-2) 3 2 (1-3) Shoulder 5 3 (1-5) 3 2 (2-3) 2 3 (2-4) Upper Back 27 2 (1-4) 3 2 (2-3) (2-4) Lower Back 39 4 (2-5) 5 4 (3-5) 8 4 (4-5) Waist 28 3 (1-4) 4 3 (2-4) 5 3 (2-3) Knee 8 2 (1-4) NR (1-2) Data presented as n (%) [Discomfort] or median (range) [BPD rating] unless otherwise indicated. P values were obtained from χ 2 test. Values for maximum discomfort do not add up to 100% due to multiple non-exclusive response categories. N: frequency of responses; NR: No Response 65

11 The perceived discomfort levels of the goldsmiths for each of the selected body parts were presented in the table 3.2. The degree of discomfort felt by the workers was not found high for any of the body parts for any kind of specific activity, e.g., fabricating, melting or polishing of the jewellery products. The median values of the BPD scores were in the safer zone (less than the middle value, 5), which indicated that the personal discomfort level was not very acute in terms of the job-associated musculoskeletal problems Evaluation of the working postures The most widely used posture in the jewellery manufacturing industries is the sitting posture especially the ground sitting. Other postures depend on the type of the task, varying from semi-squatting to standing. Analyses of the most frequent working postures as assessed by REBA and RULA were presented in Table 3.3. From the table below, it was obtained that all of the predominant postures were medium to high risky according to the scores of REBA. Scores obtained from RULA also indicated all the predominant postures under moderate risks. However, median body parts discomfort scores of all of the predominant postures ranged between 2-4 and the minimum and maximum score given by the workers for any of those postures remained within 0-6 of the BPD scale. These scores reached maximally up to the midpoint of the BPD scale (medium level of discomfort), which meant that the degree of discomfort were not significantly higher for those postures adopted by the workers. Area-specific BPD scores for each of those predominant postures were also found within permissible limit and did not deviate much from the mid-value. Workers who generally required sitting on the ground for minute and precision works complained about mild to moderate discomfort at neck, upper and lower trunk although the median values for all BPD scores remained within safe limit. Standing postures that involve bending or twisting of trunk might have some effects on the waist but did not have influence on other body parts significantly. Secondly, those standing postures were for very short duration (not more than 10 minutes at a stretch) and thus, those postures did not affect any body part significantly. 66

12 Table 3.3. Characterization of the predominant postures and assessment of postural strain Type of posture Posture Stick diagram Score (Risk level) REBA RULA BPD rating (whole body) Organ specific BPD rating Semi-squatting 5 (Medium) 5 (Change needed) 4 (2-5) Head Neck Shoulder Upper Back Lower Back Waist Knee 1 (0-2) 3 (1-5) 3 (2-5) 2 (1-4) 4 (3-5) 3 (2-5) 3 (3-5) Ground sitting with crossed legs 8 (High) 3 (Change needed) 4 (3-6) Head Neck Shoulder Upper Back Lower Back Waist Knee 1 (0-2) 4 (3-6) 2 (1-3) 4 (3-6) 4 (4-6) 3 (2-5) 2 (1-4) Ground sitting with crossed legs 7 (Medium) 3 (Change needed) 3 (2-4) Head Neck Shoulder Upper Back Lower Back Waist Knee 3 (2-4) 2 (1-3) 2 (1-4) 4 (2-4) 2 (1-3) 1 (0-2) Table continued 67

13 Type of posture Posture Stick diagram Score (Risk level) REBA REBA Score (Risk level) Organ specific BPD rating Standing with bent waist 10 (High) 5 (Change needed) 4 (3-5) Head Neck Shoulder Upper Back Lower Back Waist Knee 4 (3-5) 3 (1-4) 3 (2-4) Front bent 9 (High) 5 (Change needed) 2 (0-3) Head Neck Shoulder Upper Back Lower Back Waist Knee 2 (1-3) 1 (0-2) Ground sitting with crossed legs 7 (Medium) 3 (Change needed) 4 (3-6) Head Neck Shoulder Upper Back Lower Back Waist Knee 2 (1-4) 5 (4-6) 3 (1-4) 2 (1-4) 4 (2-4) 4 (3-6) 1 (0-2) Values of BPD scales were presented as median (range). 68

14 3.6. Discussion The study presented an insight of the prevalence of musculoskeletal disorders among manual jewellery manufacturing workers. This study also highlights the predominant postures adopted by the goldsmiths for their regular work and the relationship between the postures and postural stress. It was observed that the feelings of discomfort in the upper and lower back and waist were mostly prevalent among the goldsmiths even after stratification by their job types. The most predominant posture, which has been adopted by the goldsmiths, is sitting on the ground. According to them, this is the most relaxed and appropriate posture for their job. However, according to necessity of different other tasks, they move around and adopt some different other postures while operating some specific instruments. Score-based evaluation systems (REBA and RULA) have graded those predominant working postures as moderate to high risk. It is inevitable that sustained working in those postures could contribute extensively to the occurrences of MSDs in the trunk, including back and waist. Apart from the sitting postures, other standing postures during handling of different instruments were also found strenuous, but the most important fact is that apart from the sitting postures, the durations of the handling of machines are relatively very low. This very short time fails to impose significantly to the bones and muscles of the workers in spite of the exposure to those postures. Musculoskeletal problems are one of the most predominant physiological hazards among the small-scale industries, especially in India. Sitting for a long work hour may impose load on the vertebral column leading to the musculoskeletal problems in the upper and lower back regions. There are a number of studies, which are similar in the settings and are relevant to the present studies in regard to the postural pattern of the workers and nearly all of those studies have shown that continuous sitting on ground affects to the vertebral column. Roy and Dasgupta (2008) found prevalence of musculoskeletal disorders among a group of home-based food products (papad) makers in which the workers used to sit on the ground for a prolonged working hour. Similarly, among a group of garment factory workers, Saha and colleagues (2010) found musculoskeletal problems as one of the commonest 69

15 morbidities. In another preceded study on the garments factory workers by Bandyopadhyay and colleagues (2012), more than 30% workers reported to have discomfort in the upper and lower back regions. Zari industry workers whose working patterns and postures match largely to those of the goldsmiths also complained to have work-related musculoskeletal disorders in different body parts [Sharma and Mahajan, 2013]. The investigators found alarmingly high (almost 100%) prevalence of pain in the upper and lower back of the workers who spent more than 30 years in that industry. The lower experienced group (who had years experience) also showed had a significantly high prevalence of pain in the upper limbs. Of those workers, a significant number of respondents complained about neck and shoulder pain, which are other target organs of WMSDs. In 2010, Ghosh and colleagues received a significant complaint rate of musculoskeletal problems from the jewellery manufacturing workers. In their study, 75% of the workers complained to have low back problems, the rate being higher than that of the present study (overall 39% workers complained about low back pain). This might be because in their study, they did not follow any inclusion-exclusion criteria in the selection process. Furthermore, they did not divide the goldsmiths by work type, which according to the present study, played important role in the assessment of discomfort. A number of systematic studies have been conducted to evaluate various working postures among Indian unorganized working groups and nearly all of those studies have identified Indian standard sitting postures (mainly the ground sitting posture) highly strenuous, however, many researchers believe that traditional Indian sitting style is beneficial. Although the goldsmiths used to work in sitting posture for a long work hour, they do not work continuously for a long time. Thus, their responses on the BPD scale did not go very high. Although, the MSDs related to awkward sitting postures have been extensively studied in various aspects as well as in various industrial setups, Indian traditional ground sitting postures have not been studied. In one report, Bae and colleagues (2012) described the structural aspects of sitting on chair and sitting on ground. Although they showed that ground sitting may reduce lordosis of the spinal curve thus attribute to low back pain, they also concluded that sitting on ground with a lordotic lumber groove may reduce the chance of low back pain. Apart from the study there is no report that has been able to describe the Indian postures clearly. Moreover, 70

16 the classic posture assessment tools such as REBA, RULA or OWAS (Ovako working posture analysis system) best describe the western sitting postures, but fail to evaluate the Indian postures. Thus, these western posture assessment tools are not very much appropriate to evaluate these postures. That is why in spite of high risk ratings of the postures, the complaint of musculoskeletal problems was relatively low. 71

17 3.7. Conclusion There is a prevalence of musculoskeletal problems among the goldsmiths engaged in the manual jewellery manufacturing processes. The long work hour in the cross-legged ground sitting postures impose adverse effects on different body parts of the workers such as the upper and lower back and waist. The most predominant working postures adopted by the goldsmiths were found to be in the moderate to high zones of risk according to two posture assessment tolls, REBA and RULA, however the subjective feelings of discomfort among the workers were not found very high. Although, the posture assessment tools are widely used in the western parts of the globe, these are not much useful to assess typical Indian sitting postures. Thus, more detailed studies are required with biomechanical monitoring systems to assess those postures. 72