Chapter 8
Conclusion and future scope of present work
8.1
Introduction
In this thesis four case studies are discussed to find prevalence of occurrence
of CTS in workers of manufacturing unit in Northern part of India. Studies on
different group of subjects working in different type of assembly units reveal that
repetitive nature of job, cycle time of work, force applied during work,
demographics of workers, awkward posture of workstation etc. may lead to
occurrence of CTS. The effect of repetitive postural movements of upper extremities
on prevalence of CTS has been investigated. Further,out of the other upper
extremities (e.g. hand, wrist and shoulder), repetitive use of finger dominated
manual work are studied. It has been found that these types of works are playing a
vital role in the occurrence of CTS in assembly line of manufacturing units.
Prominent CTS symptoms responsible for occurrence of CTS have also been
identified for different assembly units. Following are the main conclusions of the
present studies:
8.2
Analysis for prevalence of CTS amongst automotive glass channel
rubber assembly line workers (Case No. 1)
In EPDM Automotive Glass Channel Assembly line initially the gender,
age, work with fingers, difficulty in grasping and hand grip strength are considered
to reveal their association with CTS occurrence in 145 workers. The participation
rate of the workers is 39%. This study emphasized the operation wise analysis
using different statistical tools and sEMG. Later, the symptomatic study of 60
workers has been considered to find out the association of symptoms with CTS
occurrence. Statistical tools and sEMG analysis have been used.
Outcome of the two different studies;
a) operation wise symptomatic
analysis for various demographics; b) occupational and personal risk factor based
symptomatic analysis are summarized in the following section.
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8.2.1 Operation wise analysis for occurrence of CTS symptoms in assembly
line workers
The results from the operation wise analysis for the occurrence of CTS
symptoms in assembly line workers are,
a) CTS severity has been observed significantly high in the old age group
(33yrs – 48 yrs) workers as analyzed through SPSS software package. In the
old age blood vessels may get damage leading to poor circulation.
b) Workers with high BMI rate have greater CTS risk.
c) It has been observed that there is no significant association between gender
groups (males and females) and CTS severity levels as the p-value is greater
than 0.05.
d) Chi-square test of independence reveals that workers performing ‘work with
fingers’ are more prone to CTS occurrence.
e) Using Chi-square test, it has been confirmed that the probability of having
CTS is more while having ‘difficulty in grasping’ in comparison to other
potential CTS symptoms. The value of χ2 obtained is 5.17 which is greater
than the standard value (3.84) at 95% confidence interval.
f) Spearman rho rank order test has also been applied through SPSS which
reveals that in moulding, trimming, clipping, tapping and inspection
operations, the group of workers performing ‘work with fingers’ and
finding difficulty in grasping are correlated to each other (‘work with
finger’ and ‘difficulty in grasping’). It has been reaffirmed by the manual
calculations using t-test.
g) The average of mean sEMG-RMS values of workers having CTS symptom
is found to be lower than that of healthy workers indicating poor muscle
activity amongst CTS sufferers. The mean sEMG-RMS values of CTS
sufferers performing different operations are in the range of 0.011 mV –
0.026 mV. On the other hand, for the healthy workers it is in the range of
0.156 mV – 2.665 mV.
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8.2.2 Occupational risk factor analysis for occurrence of CTS symptoms
The results from the occupational risk factor analysis for the
occurrence of CTS symptoms in assembly line workers are summarized as,
a) Results of occupational risk factor analysis of potential CTS symptoms are
in contradiction to operation-wise analysis. It shows that the female workers
are more prone to CTS occurrence than their male counterparts.
b) The analysis using SPSS indicates that a worker is likely to be CTS sufferer
after working for more than 10 years on the site. The hand grip strength is
also found to be significantly lesser (around 40%) in CTS sufferers than the
healthy workers.
c) SPSS based analysis of occupational risk factors also shows that heartbeat,
weight and BMI does not contribute significantly towards potential CTS
symptoms.
d) Analysis using one-way ANOVA indicates F-ratio of grip strength is
significant. Grip strength less than 35 kg and moderate tingling comes out to
be the most alarming symptoms for CTS occurrence among the workers in
the occupational risk factor analysis.
e) Analysis using sensitivity and specificity reveals that use of hands in highly
repetitive jobs has comparatively high prevalence ratio of CTS risk factors
and symptoms.
f) Reduced hand grip strength is one of the alarming symptoms of CTS as the
mean sEMG-RMS value for the affected workers is as low as 0.0283 mV.
g) Subjects with lower sEMG signals have also shown the presence of
nocturnal pain, tingling, weakness in wrist/hand, positive Tinel’s and
Phalen’s sign.
8.3
Comparison of CTS and productivity factors in traditional and semiergonomic shocker manufacturing unit (Case No.2)
In traditional and semi-ergonomic shocker manufacturing unit, different
demographic factors like age, BMI, hand grip strength and shoulder strength;
productivity factors like repetition per minute and cycle time, symptoms like
numbness, tingling and weakness, etc. have been taken to find out their relation with
CTS. Seventy workers from each industry are considered. The participation rate in
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traditional industry is 77% and in semi-ergonomic 87%. This study indicated the
comparison of CTS occurrence and productivity factors in both industries using
statistical tools and normative data to show the following conclusions:
a) The mean cycle time in different operations in semi-ergonomic assembly
unit is 12 % less than the traditional assembly unit. Production rate in the
semi-ergonomic
manufacturing
unit
is
34%
higher.
Number
of
operators/workers suffering from CTS in semi-ergonomic industry is around
30% less as compared to traditional industry. Average age in the two
industrial units under study has been considerably different. Traditional
industry has average age at around 40 years, while in the semi-ergonomic
industry workers are having average age of 29 years.
b) As the average age in the two industrial units under study is considerably
different, data has been also analysed for the same age group (20 yrs-40 yrs).
In the age group 20 yrs-40 yrs CTS sufferers in semi-ergonomic assembly
unit is around 20% less than the traditional assembly unit. Average shoulder
strength is
6% more and production output is
30% more in semi-
ergonomic assembly unit. Average shoulder strength and production output
of CTS sufferers is lesser than that of non-CTS sufferers in both the
industries.
c) There is more number of awkward posture work stations in the traditional
assembly unit but no correlation between number of awkward posture work
stations and CTS sufferers for a given operation might be established.
d) Workers in semi-ergonomic assembly unit share only 35.2% heavy load
work as compared to 64.8% of heavy load work by the workers in traditional
assembly unit.
e) Assessment of risk shows that operation involving prolonged/repeated
flexion and extension of wrist has higher risk of CTS occurrence.
8.4
Studies of hand arm vibration exposure on CTS symptoms and
occurrence (Case No.3)
In Gear manufacturing industry 116 workers have been working and their
participation rate is 89%. In this work side effect of hand arm vibration exposure has
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been studied on workers focusing on CTS occurrence. ANOVA, Chi square test,
Correlation analysis and electromyogram signal analysis are used to achieve the
objectives. Potential CTS symptoms, CTS symptoms severity scale and hand arm
vibration exposure are used to describe their relation with CTS occurrence.
Following are the conclusions:-
a) It has been found that there is no symptom at high and severe level in this
population. It might be due to that such persons are not able to perform their
duty and are absent or changed the job.
b) The most prevalent symptom at moderate level is numbness (57.8%),
followed by weakness (26.7%) and tingling (19.8%).
c) The most prevalent symptom at low level was tingling (48.3%), weakness
(43.1%) and wrist pain (38.8%).
d) The least prevalent CTS symptom is difficulty in grasping. There are 72.4%
workers who had no DIG symptom. There are 63.8% workers with no hand
pain and 52.6% workers with no wrist pain when observed independently.
e) Results showed that the vibration exposure time in a day has impact on
severity of CTS symptoms.
f) It has been found that there is good positive correlation of various potential
CTS symptoms with duration of job and these symptoms tend to increase in
severity as the duration/length of job increases.
g) There is no statistically significant association between any of the industrial
shop and CTS symptoms. Hence there is no significant impact of workplace
or type of work under study on severity or occurrence of CTS symptoms.
h) There is no significant correlation of severity of CTS symptoms with the
vibration amplitude exposure level. Correlation of sEMG and vibration
amplitude exposure level also verifies the same.
i) There is no statistically significant relationship between hand grip strength
and sEMG.
8.5
Study of pinch strengths and CTS occurrence in muffler assembly line
workers (Case No. 4)
In Muffler assembly line industry 123 workers have been considered and
their participation rate is 85%. Factors like age, CTS symptoms, level of repetitive
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work, pinch strength and hand grip strength are considered to find their association
with CTS occurrence using statistical tools and sEMG. Following are the
conclusions:-
a) It has been found that as the age and weight increases there are more chances
of having CTS symptoms. The statistical analysis revealed that the CTS
sufferers have less mean grip strength for dominant hand (Mean: 35.07 kg,
SD: 10.82 kg) in comparison to Non-CTS sufferer (Mean: 53.08 kg, SD:
7.12 kg). It has been concluded that CTS has potential impact over grip
strength of both hands. As the CTS severity increases, there is more chance
that workers might lose their strength for griping the objects.
b) It has been revealed by this study that there is no significant correlation
between BMI rate and any of the CTS symptoms. Thus BMI doesn’t have
any role in the occurrence of CTS symptoms for the present group of
subjects in muffler assembly unit.
c) There are negative moderate correlation between grip strength of dominant
/non-dominant hands and almost all CTS symptoms except for ‘difficulty in
grasping’ and ‘weakness’. ‘Wrist pain’ and ‘numbness’ has strong positive
correlation with CTS prevalence. The wrist pain and numbness may be
considered as strong indicators for CTS prevalence and may be used to
predict CTS in muffler assembly unit.
d) The pinch strengths of CTS sufferer are significantly (statistically) lower
than the non-CTS sufferers except in case of pulp pinch in supinated position
for non-dominate hand with digit II and III. It indicates that the worker with
CTS has low pinch strengths.
e) There is considerable difference in pulp pinch strength of individual digits.
Rank order of pulp pinch strength for individual digits is Digit III > Digit II
> Digit IV > Digit V for both dominant and non-dominant hand.
f) Workers with high CTS severity level have low sEMG values and lower
muscle activity. sEMG values tend to decrease for workers who have been
reported for wrist pain and numbness. Wrist pain and numbness has a
definite correlation to CTS occurrence in present group of workers.
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8.6
Future scope of the present work
In view of the conditions prevailing in the workers having repetitive nature
of work in different industries and the conclusions drawn from the present work,
following studies can further be conducted for minimizing the damage to the
workers.
i) Study on posture modification and its effect on lowering of CTS
occurrence may be taken up as a significant future work.
ii) Characterization of sEMG features and their correlation with CTS
occurrence may be explored.
iii) Continuous sensory monitoring system for human-machine interface
(force, twist, strain, fractional use of specific part of the hand etc.) may
be developed to analyze the occurrence of CTS.
iv) Based on the data of continuous sensory monitoring system and
suggested activities to reduce the CTS occurrence, reminder software
can be developed which may suggest activity and relaxation to avoid
CTS occurrence. It may be the part of a wellness program to operators/
workers.
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