Agriculture is a very demanding activity, and it its association with several musculoskeletal disorders is well known. The musculoskeletal symptom most frequently reported by agricultural workers is low backpain (LBP) [1]. The proportion of farmers reporting LBP varies between 31% [2] and 50% [3], with the highest prevalence among those engaged in agricultural activities for more than 25 hours per week [4]. Other studies have indicated a high prevalence of musculoskeletal symptoms among farmers for shoulders (25.9%), knees (23.6%) and the cervical spine (22.4%) [5].

A systematic review of literature on musculoskeletal disorders in agriculture concluded that the spine is the most studied body region, followed by lower and upper extremities. This review highlighted the necessity to conduct studies focused on specific types of farming, physical exposures specific to the workers’ tasks and specific body parts [8].

Among agricultural work activities, dairy farming is of particular interest in occupational medicine because of the variability of tasks and exposure to a variety of biomechanical risks. There are evidences that both male and female workers perceive the milking routine tasks performed repetitively to cause more musculoskeletal discomfort than heavier tasks performed on a non-routine or seasonal basis [9]. As for dairy workers, researchers have identified heavy lifting loads and repetitive motions contributing to adverse musculoskeletal effects on the lumbar spine, shoulders, necks, hands and wrists [10]. According to existing literature [11, 12], the milking tasks requiring particular hand and wrist intensive efforts in terms of the repetitive physical exposures are:

In each phase, parlor design and anthropometric and cows’ body characteristics also affect the levels of physical overload [14]. The three common milking systems used in Italy include the rotary, the parallel and the herringbone design systems (Fig. 4).

In each of the three parlor configurations, workers perform the same four primary milking tasks described above. Although workers may rotate from station to station or from cow to cow, it is evident that awkward postures, repeated exertions, velocity of wrist movements of flexion and extension, radialulnar deviation and are the main biomechanical risks affecting the upper limbs [16–18]. The introduction of the new loose housing milking systems has increased hand wrist extension and repetitiveness [16] as well as static load but reduced muscular rest [19]. Industrialization has also brought about an increase of the time spent in milking activities and therefore the levels of workers’ exposure to these risk factors [13].

The main symptoms resulting from the above-mentioned exposures are tingling, numbness, pain and/or reduced muscle strength [13, 20]. In some cases, symptoms are accompanied by evidence of entrapment of the median nerve at the level of the elbow and the wrist (Carpal Tunnel Syndrome) [16, 21–23]. In this light, the median nerve seems to be the most sensitive target of the repetitive forceful handwork [24], but other soft tissues of the area may be affected [25].

Most of the available studies on workers’ wrists and nerves have been conducted with ultrasound examination, which seems to be highly sensitive for detecting abnormalities, but unable to provide information regarding the severity of the changes [27]. For this reason, an ultrasound approach must be accompanied by physical examination and symptoms reported by individuals [28].

Available data suggest the existence of a significant health risk, but the information comes from very small study groups [8, 13, 14, 17, 19, 20]. The main reasons for this situation are, from one side, the well-known poor access of rural workers to health surveillance at the workplace, and, from the other side, the fact that using ultrasonography is still time consuming, not easy to conduct at the workplace, and therefore non-adequate for screening activities.

As highlighted in other studies, there is paucity of data describing standardized scanning methodology and standardized definitions of Ultrasound pathologies [28]. Therefore, there is a growing need for additional studies specifically focused on defining a screening method that is able to allow the involvement of larger groups of workers and to perform routine health surveillance of workers at the workplace.

The aim of this cross-sectional pilot study was to define a study protocol adequate to identify hand and wrist disorders among milking parlor workers, and suitable to conduct a relatively rapid assessments of the wrist district even on large groups of workers.

The present pilot study was conducted on a group of 14 male dairy parlor workers selected among the enterprises being provided with occupational health surveillance by the International Centre for Rural Health of the University Hospital San Paolo of Milan, a World Health Organization Collaborating Centre. Twenty-two healthy male participants were selected as a control group, paired with the exposed participants for gender, age and ethnicity. None of the control participants had ever been engaged in agricultural activities or jobs requiring manual handling of heavy loads or repetitive hand motions.

The experimental approach, approved by the Human Ethics Committee of the University Hospital San Paolo, was based on three components: 1) the identification of workers’ symptoms through the administration of a questionnaire, 2) ultrasound imaging (ultrasonography) of the wrist region performed with portable ultrasound instrumentation, and 3) a physical examination of the upper limb including standardized clinical tests. Before participation, the involved participants had been informed about the approach and the aims of the study and provided informed consent.

All the following activities were conducted at the workers’ workplace, in rooms made available by the employers and declared adequate to the study by the research group.

Since most of the milkers were migrants, with a low educational level, the questionnaire was completed with a graphic representation of a human body on which the workers were asked to indicate the body areas where symptoms such as pain, tingling/numbness, weakness, night symptoms were present. In addition to symptoms, the following information was collected from all participants: nationality, gender, age, education level, occupational history, body weight, height, exercise habits, handedness, duration of present job, hours worked per day, and the presence of manual materials handling tasks during the work shift. We also asked the milkers to estimate the number of animals milked per day and about the type of milking system (rotary, parallel or herringbone) and milking cluster characteristics they used during their work-shift.

The ultrasonography (US) examination was performed by a sonographer according to the European Society of Musculoskeletal Radiology’s protocol (ESSR) [29, 30], with the examination of more than 20 body areas adequate to investigate specific wrist’s districts with ultrasonography (“acoustic windows”) in both wrists (Table 1). The ultrasonography equipment (Venue Scan, Venue 40, GE Healthcare®) allowed the researchers to store the examination for further evaluation and discussion with other hospital experts in the final evaluation of all cases.

Wrist was investigated through the determination of the following parameters for each acoustic window selected: US texture, shape, range and pattern of motion. For the classification of the ultrasound study results, we adopted the grading system proposed by Yoon et al. [31] and by Wakefield et al. [28]. In particular, differing from the original protocol, we divided the results in two main categories (0 = normal/expected and 1 = abnormal). This in order to give, in the frame of a preventive approach, particular attention to preclinical and very early changes, fundamental for secondary prevention. However, since a dichotomous classification does not discern the severity of changes in the ultrasound signal detected, the following classification criteria were created for nerve and tendon findings

All milkers and controls underwent a clinical examination of the upper limbs, performed by an occupational health physician. The clinical examination included an evaluation of symmetrical posture of the clavicles, hypersensitivity to palpation, hyperextension and hyperflexion of the fingers; Finkelstein test, Phalen’s maneuver; Tinel’s sign, wrist radial and ulnar reflexes, elbow, wrist, finger range of motion (ROM), and sensitivity to an upper limb tension test of the median nerve [32]. Since most of the available data suggest an impairment of median nerve, we completed the physical examination of the workers with the pinch-holding-up activity (PHUA) test [33]. We chose this test, among the others available for the purpose [34–36], because pinching activity seems to be particularly significant in milking tasks. Only one test was applied among the various tests available because of the need of defining a screening procedure, to be easily and rapidly performed at the workplace. Evaluation was performed asking the workers to lift with the pulps of thumb and index finger to 5 cm above the table top, a small metal clip for 5 seconds. Results were dichotomously classified (0 = normal; 1 = reduced gripping capacity).

The majority of the variables from the questionnaire and clinical examinations were dichotomous and classified as either absent or present.

Statistical analyses were performed with SPSS PC version 22. Differences between groups (milkers and controls) were assessed with Chi Square and Fisher tests with statistical significance set at p ≤ 0.05.

We studied a group of 14 dairy parlors workers and 22 controls. There were no significant differences between exposed and controls for the potential confounding factors of age, gender, and ethnicity (Table 2). The milkers were engaged in their work activities for periods ranging from 0.5 to 40 years (median = 15.5 years).