Civil Engineering Reference
In-Depth Information
11.3
CAUSES OF REPETITIVE MOTION INJURY
There are several different factors that may play a part in causing cumulative trauma
disorder. For the individual case, it is often impossible to pinpoint a primary cause. One
must take a comprehensive look at all the various manual activities that may have
contributed to the RMI. It is not just a matter of inappropriate or aggressive work
methods, but also what type of activities are performed when one is off work. Leisure
activities such as knitting, carpentry, and tennis playing will also impact the likelihood of
developing RMI. Some of these factors are listed in Table 11.3 (Armstrong and Chaffin,
1979; Eastman Kodak Co., 1986; Putz-Anderson, 2005).
In addition, there may be psychological “causes” of cumulative trauma disorder. One
well-known incidence is the so-called RSI epidemic in Australia. During 1984, the
repetitive motion injury rate increased by a factor of 15 (from 50 to 670) among
employees of the Australian Telecom. However, the injury rate decreased, and by the
beginning of 1987 it was back to normal (Hadler, 1986; Hocking, 1987). This sudden
increase and subsequent drop in injury rate could be attributed to psychological factors.
Some operators may have heard that colleagues were having problems and would
interpret their own symptoms as being serious manifestations of RMI.
In the last couple of years, the RMI rate has increased in the U.S. and in Europe, and it
would be natural to assume that some of the reported injuries are psychological in nature.
But there is also a real problem, and the increased injury rate may be due partly to the
situation where it has become accepted in society to report RMI, whereas this was not an
accepted work injury in the past. Indeed, Hadler (1989) documented the types of back
injuries reported in Switzerland, Germany, and Holland. The legal definitions of back
injuries are different in these countries, and as a result different types of back problems
are reported. Society norms and acceptance seems to affect greatly the type of
occupational injuries that are reported.
Another example is for VDT workers. In the Scandinavian countries there were
frequent complaints of pain in the neck and shoulder in the end of the 1990s (Hagberg
and Sundelin, 1986), but RMI was rare (Winkel, 1990). In the U.S. the situation was
different, and carpal tunnel syndrome was frequently reported among VDT operators
(National Institute for Occupational Safety and Health, 1992). The shoulders and hands
are connected by the three nerves—see Figure 11.1(B)—and there may be a possibility
that the etiology of the injuries is the same, although the manifestation of complaints are
different, so as to conform to the local norms. Whatever reason employees may have
(physical or psychological), one must take
TABLE 11.3
Causes of Cumulative Trauma
Disorders
Inappropriate work methods
• Repetitive hand movements with high force
• Flexion and extension of hand
• High force pinch grip
• Uncomfortable work postures
