Ergonomic workplace assessment in orthotic and prosthetic workshops

1 Introduction

Musculoskeletal disorders (MSDs) are a worldwide concern [1–3]. These disorders mainly appear in the lower back, neck and upper body [4]. Despite the global trend to replace manual work with mechanized and automated systems, work-related musculoskeletal disorders (WMSDs) are the major cause of work time loss and increase workplace costs and injuries [5]. Risk factors for WMSDs have been found to include workplace activities such as heavy load lifting, repetitive tasks and awkward working postures. Demographic characteristics (i.e., age, gender, job tenure, etc.) and psychosocial factors are also known to be important predictive variables [6, 7]. These disorders can be prevented through proactive measures devised based on ergonomics assessments [8, 9].

Rehabilitation is a process that returns ability to injured limbs [10]. Orthotists and prosthetists are members of the rehabilitation team who are responsible for designing and producing orthoses and prostheses to control, compensate and prevent injuries [11]. In the orthoses and prostheses production processes, the staff is exposed to risk factors of musculoskeletal injuries [12]. Heavy load lifting, force exertion, repetitive movements, inappropriate static postures, vibration, contact stress, pinch grips and environmental factors have previously been identified as the main factors associated with musculoskeletal injuries in the orthotic and prosthetic processes [13–17].

In Iran, assistive devices (such as orthoses and prostheses) are produced clinically in workshops via different operations such as metal working, positive model rectification, sanding, drilling, sawing, etc. In these workshops, the majority of activities are carried out by manpower and the tasks are labor-intensive. Manual material activities (e.g., heavy load lifting, lowering and carrying), awkward and static working postures are very common and ergonomic aspects of working conditions are seldom considered. In general, a few studies have been conducted on occupational health and safety of orthotic and prosthetic personnel [12] and in particular, there has been no study specifically related to WMSDs in Iranian orthotic and prosthetic workshops that report the prevalence of symptoms and assess physical exposure to musculoskeletal risks. The present study was, therefore, conducted in these workshops with the following objectives:

To determine the prevalence of musculoskeletal symptoms among employees.

The results of this study may be considered as a basis for planning and implementing interventional ergonomics programs in the workplace and improving employees’ health and quality of working life.

2 Materials and methods

In this cross-sectional study which was conducted from August 2013 to February 2014 in 11 active orthotic and prosthetic clinics of Shiraz city, Iran, 42 employees including 29 males and 13 females with at least one year of job tenure participated. Employees with pre-existing musculoskeletal injuries were excluded from the study.

3 Results

The demographic characteristics of the 42 subjects (29 males and 13 females) participated in the study are shown in Table 1.

Table 2 presents the period prevalence (the past 12 months prior to the study) and point prevalence of musculoskeletal symptoms in different body regions of the individuals. As shown, lower back (42.9%), shoulders (40.5%) and knees (40.5%) symptoms were the most prevalent problems among the subjects during the last 12 months.

Workplace assessment revealed that awkward working posture, inappropriate workstation design, poor design of hand tools and harmful manualmaterial handling were notable ergonomics problems in the workshops. Figure 1 shows these issues in the workshops studied.

4 Discussion

The results of this study showed that the most commonly affected regions among the subjects were the lower back, shoulders and knees. The ergonomic assessments revealed that the main ergonomic problems in the workshops studied originated from awkward working posture, improper workstation design, poor design of hand tools and incorrect manual material handling. This indicated improper conditions necessitating ergonomics solutions. To improve working conditions, corrective measures should focus on these issues.

Specific recommendations would include correcting non-adjustable height and angle of working surface, working in static postures, repetitive movements especially of the upper body and working in standing position for long periods of time. Andersson et al. reported physical job demands (i.e., postures, loads and exertion) as important occupational health and ergonomic contributing risk factors of MSDs in Australian orthotic and prosthetic workshops [12].

In many studies [5, 20] awkward postureswere found to be the main associated factor for reported musculoskeletal symptoms. The main reason for static and awkward postures has been reported to be non-adjustable workstations [7]. Also, the results of Abaraogu et al. [5], Choobineh et al. [7] and Lin and Chan [20] studies demonstrated that improving working posture can be effective on reducing musculoskeletal injuries occurrence. Many of the existing workstations required undesirable postures (e.g., bent neck and rotated back), which represent ergonomic risks.

A poorly designed hand tool was another source of ergonomics shortcoming. Ergonomically designed hand tools causes neutral posture of hand and wrist, increases comfort and reduces the risk of musculoskeletal disorders in this region [21, 22].

Some of the tasks in orthotic and prosthetic clinics were such that subjects had to work in standing position for several hours. Since workstations were non-adjustable, subjects with different statures and body dimensions had to work at the same workstation.This condition could be a reason for awkward postures in the neck, shoulders and back.

Working with grinders, positive cast rectification and cutting were also performed at improper table height. Shoulder flexion and abduction of arms during the cutting with electric saw were also observed in the majority of the studied individuals (Fig. 2).

Additionally, work stations were not equipped with seat and footrest. Anti-fatigue mats were not provided for the staff who worked in standing posture for long periods either (Fig. 3).

In the shoe making operation, in shoe hammering awkward working postures in sitting position were observed in most workshops.

Manual handling of heavy plaster molds (more than 25 kg of weight) for various processes such as cast modification, lamination, making thermoplastic mold, preparation of negative and positive cast and filling the negative cast were common in almost all workshops (Fig. 4).

Working in constrained space and lack of mechanical aid or a co-worker to lift heavy objects (i.e., plaster molds) exerted high physical load on subjects’ musculoskeletal structure (Fig. 5).

This could be a reason for high prevalence of musculoskeletal symptoms in the lower back. The results of a previous study has shown that prevalence of back disorders in manual handling tasks is 8 times more as compared to that of tasks without manual handling [23]. Furthermore, several studies have shown that team heavy load lift might put less pressure on the spine than when the subject lifts the load alone[23, 24].

Work organization assessment revealed that no training programs existed in the workshops concerning proper work method, correct methods for manual material handling or appropriate use of hand tools and their maintenance. It is to be noted that most employees did not have relevant academic education or training. Since orthoses and prostheses must be produced quickly and precisely and delivered to the patient or client as soon as possible, no work pause or proper work-rest cycle might be devised. This could increase exposure time with MSDs risk factors. Andersson et al. indicated job design as an effective factor for MSDs in orthotic and prosthetic personnel [12].

General working conditions assessment of clinics indicated that use of proper ventilation especially for sanding operation and where chemicals (e.g., glue) were used was essential to capture airborne contaminants. Our observations indicated that appropriate personal protective equipment (PPE) such as respiratory masks and ear plugs were not used in the workshops, despite conditions where they would normally be recommended (Fig. 6).

Regarding to the cross-sectional design of the study and data collection by self-report method and observation, the findings of this study should be interpreted with caution. Self-report methodology may suffer from some weak points namely difficulty in recall, denial or deception. Additionally, since the study was limited to currently working employees, those who had left jobs due to musculoskeletal symptoms may have been excluded from the study and healthy worker effect might occur. Thus, the data may underestimate reported symptoms.

5 Conclusions

The findings of the present study, as a first ergonomics study in Iranian orthotic and prosthetic workshops indicated that symptoms from the musculoskeletal system were common among the subjects studied. The majority of the study population had experienced some form of symptoms from the musculoskeletal system during the last 12 months. Lower back, shoulders and knees symptoms were found to be the most prevalent problem among the individuals studied. This indicated that the problem of musculoskeletal disorders in orthotic and prosthetic workshops was serious and needed appropriate attention. This could be attributable to poor awkward working posture, inappropriate workstation design and inappropriate manual material handling. Therefore, any interventional ergonomic measures should focus on these problems.

Conflict of interest

The authors have no conflict of interest to report.