Neck and upper limb disorders among slaughterhouse workers An epidemiologic and clinical study

The aim of the study was twofold, (i) to detect neck and upper limb disorders in slaugh- terhouse workers and (ii) to develop methods for the epidemiologic screening of these disorders. A total of 117 slaughterhouse workers underwent a physical examination of the neck and upper extremities and were interviewed for their subjective symptoms. In addition to a prestructured screening diagnosis, a clinical diagnosis was made. The prevalence of tension neck syndrome was 6.2 %, and that of tenosynovitis and peritendinitis of the wrist and forearm 4.4 %. The screening diagnoses were not always the same as the clinical diagnoses obtained in more-detailed examinations. However, the nine disorders in the screening method fairly well represented the disorders detected in the clinical examination.

The Finnish Occupational Disease Register has reported high incidences of occupational musculoskeletal disorders (including tenosynovitis and peritendinitis of the wrist and forearm region and humeral epicondylitis) among slaughterhouse workers (17). However no epidemiologic studies with clinical examinations have been done for the detection of neck and upper limb disorders in slaughterhouse workers. The subjective musculoskeletal symptoms of these workers have been screened in questionnaire studies (5,9).
Suggested causative factors of the disorders include repetitive work in meat cutting, fast work paces, and high resistance, especially of beef (9). In some slaughterhouses the temperature of the meat to be cut is low, and low temperatures increase both the resistance of the meat and the stress of the work. The diagnosis of musculoskeletal disorders is often difficult and confusing, both at clinics and in epidemiologic settings. Generally accepted and used diagnostic criteria exist for a few disorders only, whereas the criteria for such common disorders as tension neck syndrome, cervical syndrome, humeral epicondylitis, and tenosynovitis and peritendinitis of the wrist and forearm vary widely (18). Diagnostic criteria for these disorders would be of value in the comparison of research results.

Subjects and methods
The slaughterhouse under study in the present investigation employed a total of 119 butchers, meatcutters, and meat byproduct workers. Two were on sick leave because of illnesses not related to the study. Of the 117 workers examined, four were excluded from closer analysis, three because of a recent injury and one because of recent surgery for a habitual humeral dislocation. No one reported active rheumatoid arthritis. Eighty-two of the remaining 113 workers were men and 31 women: there were 52 cutters. 38 butchers, and 23 meat by-product' workers. Twelve cutters and eleven butchers were trainees who did the same work as their more experienced workmates.
The temperature of the meat to be cut varied between 0 and 7"C, and the temperature of the workplace was 10°C.
The slaughterhouse had been operating only seven years. At the beginning many young trainees were hired, and therefore the workers were very young. Their mean age was 31.8 (SD 9.3) years, 30.1 years for the men and 36.1 years for the women. The mean length of employment was 5.5 (SD 5.4) years. The work pace was reported to have been reduced by approximately 25 '70 for the two weeks preceding the examinations because of salary disputes; the reduced work pace was used throughout the study.
The screening method used in this study (18) was also used in two earlier epidemiologic screenings (6,8). According to the method a physiotherapist gives each subject a preplanned physical examination and interviews the subject, and the screening diagnosis is made by a predetermined set of criteria. The disorders and the criteria for the disorders, as well as the tests used and the symptoms recorded, are presented in table 1. In the present study the subjects were asked, at the end of the interview, to make a drawing of the pain experienced during All the workers were examined by the author. A neurological examination of the upper arms was added to the standard set of tests. The neurological examination tested for brachioradial and triceps deep tendon reflexes; shoulder elevation; and deltoid, biceps, triceps, lumbrical and interosseus functions (strength, with special reference to the difference between the sides). Sensitivity to light touch and pain in the upper arms was tested, as was sensitivity to vibration at the ulnar styloid processes and the lateral malleoli. Roos' elevated arm stress test for thoracic outlet syndrome (14) was also included in the standard set of tests. The subjective component of performing and judging each test was reduced by the procedure of first examining the subjects and then interviewing them.
The examination procedure was continued so that a clinical diagnosis could be obtained if the diagnosis based on the screening method conflicted with the pain drawing, if there was marked pain and no screening diagnosis was made, and if there was localized paresthesia, numbness, or a disturbed sensitivity to light touch or pain. At this stage other forms of the mentioned pain syndromes and differential diagnostics were also taken into consideration, as were some other common painful conditions and the most common distal and upper l i m b disorders (18)  So that the repeatability of the tests of procedure followed in making the diagthe screening method could be checked, 33 nosis is shown in fig 1, and the criteria persons were examined by a specially for clinical diagnoses are presented in trained physiotherapist. table 2. Pronator syndrome (1,11,16) Posterious interosseus nerve entrapment (Frohse's syndrome) (4. 15, 19) Ulnar nerve entrapment at the elbow (1) Ulnar nerve entrapment at Guyon's tunnel (1) Same as the criteria for the screening diagnosis (table 1); muscle pain or tightness upon neck movement not necessary (cases that also meet criteria for the clinical diagnosis of cervical syndrome classified as cervical syndrome) Pain radiating from the neck to the upper extremity or pain in the neck and numbness in the hand, limited neck movement, pain in the neck during neck movement (peripheral entrapment neuropathy of the upper arm excluded) Pain radiating to an upper extremity, positive elevated arm stress test (distal nerve entrapments excluded) Same as the criteria for the screening diagnosis (table I), but limited active abduction not necessary, pain in resisted isometric abduction possible Same as the screening diagnosis (table I) Pain, paresthesia or numbness in the fourth and fifth fingers, tenderness to palpation at the cubital tunnel, Tinel's sign at the cubital tunnel possibly present; diminished sensation in the fourth and fifth fingers and weakness of the inter0Ssei and the third and fourth lumbricales possible (ulnar nerve entrapment at the Guyon's tunnel, cervical syndrome, and thoracic outlet syndrome exluded) Pain, paresthesia, numbness and/or weakness of the fifth finger, tenderness to at the Guyon's tunnel possible, Tinel's sign at the Guyon's tunnel possible; dimmished sensation in the fourth and fifth fingers or weak abduction of the f~fth finger (ulnar nerve entrapment at the cubital tunnel, cervical syndrome, and thoracic outlet svndrome excluded)

syndrome. Other disorders occurred only seldom. Screening and clinical diagnoses
As the tests of the screening method revealed few positive signs, no statistical The results are presented as screening diagnoses and clinical diagnoses in table 3. analysis was necessary for the findings of According to the set of criteria seven the two examiners. There was a trend for the palpation tests of the neck and shoulworkers (five men and two women) had tension neck syndrome. The syndrome der region administered by the physiowas evenly distributed among the different therapist to reveal more positive results occupations and occurred in subjects of than the palpation tests administered by different ages. the author.
Six men were clinically diagnosed as having cervical syndrome. They represented different occupations. Four were over 40 years of age.
Five cases of peritendinitis were found in the forearm region of four workers (table 4). These cases did not meet the criteria of the screening method. Four were on the extensor side, one was on the flexor side, and one worker had peritendinitis on both the flexor and the extensor side of her forearm. Three of the workers were men.
In addition to the disorders contained in the screening method used, five cases of painful carpal ganglia were found. Four were on the volar side and one on the dorsal side of the wrist. All volar ganglions were found in cutters, and they were in the dominant hand. Three of these cutters were men, and one was a woman. Three cases were residual after earlier surgery. Two workers with a volar ganglion had nocturnal paresthesiae of the median area of the same hand, and one of them also had a positive Tinel's sign and Phalen's wrist flexion test that suggested carpal tunnel

Symptoms reported by the subject
In addition to their present symptoms the workers were also asked about pain or trouble in the neck and shoulders, the back, and the arms and hands during the past 12 months. Table 5 shows that neck and shoulder trouble was more common among women than men and, in both sexes, more common than back trouble. There were no appreciable differences between the sexes concerning arm and hand trouble. Neck and shoulder trouble, back trouble, and arm and hand trouble were found about as often in all the age groups.
The workers were also asked if a doctor had diagnosed tenosynovitis or peritendinitis of the wrist or forearm or humeral epicondylitis during the past 12 months. There were 15 (13.3 70) subjects who had had 18 (15.9 %) cases of tenosynovitis or peritendinitis and four (3.5 %) who had had epicondylitis. One worker had had both lateral epicondylitis and flexor tenosynovitis at the same time. Three workers had had tenosynovitis twice during the past year. Two workers who had experienced peritendinitis earlier also had peritendinitis at the time of the examination. All 15 workers who had previously had tenosynovitis or peritendinitis were men, cutters or butchers by occupation, and 12 of them were under 30 years of age. The workers with epicondylitis were 30 years or older.

Results
As shown in table 6, the prevalences of both tension neck syndrome and tenosynovitis and peritendinitis of the wrist and forearm were very low when compared with the corresponding values of three groups of 'predominantly female subjects examined by the same method. However, the five cases (4.4 70) of current peritendinitis agreed with the reported 18 clinical cases (15.9 %) of tenosynovitis or peritendinitis that had occurred during the past 12 months.  The fact that cases of tenosynovitis or peritendinitis were encountered during the past 12 months only among cutters and butchers and predominantly among young workers supported the concept that overexertion and lack of experience are its important causative factors (7). Furthermore, a recently terminated absence was the triggering factor in most current cases of peritendinitis.
The low prevalence of tension neck syndrome and peritendinitis of the forearm can most likely be attributed to two factors, (i) high selection and (ii) reduced work pace. The seven years that the slaughterhouse had been operating provided a suitable time for selection. Young, unfit workers had left the workplace, and the remaining workers became skillful in their work. The reduced work pace evidently had a direct effect on such signs as tenderness and swelling of the muscles and tendons, which were the objective criteria for tenosynovitis and peritendinitis.
The higher prevalence of neck and shoulder trouble in women (table 5) has been noticed also in other studies of working populations (5). The trend was the same in the "normal population" according to the preliminary reports of a recent Finnish study called "Mini-Finland." However the relatively high prevalence of neck and shoulder trouble also in men, which was higher than the prevalence of back trouble, is noteworthy. The situation was the reverse in the "normal Mini-Finland" population, for which back trouble was far more common in men than neck and shoulder trouble. Comparison of the frequencies of neck and shoulder trouble, back trouble, and arm and hand trouble among the men of this study with those among a group of Swedish slaughterhouse workers in similar occupations (table 5) showed that the frequencies for neck and shoulder trouble and for back trouble were approximately the same, whereas trouble in the arms and hands was more common among the Finnish slaughterhouse workers.
The occurrences of painful carpal ganglia, most of which were on the volar side of the wrist, should be noted. The carpal ganglion in itself does not often cause problems. All five ganglia found were painful, probably because of the work demands on the wrist.

The method
The validity of the screening method used for this study is unknown, nor can it be directly tested by this study, as the clinical and screening diagnoses were based partly on the same tests.
However the thorough physical exarninations did not reveal many cases of disorders not contained in the epidemiologic screening method. The cases of carpal ganglia were an exception. Much has been written lately about entrapment neuropathies and their relation to work (2). Two workers in this study group had symptoms that suggested carpal tunnel syndrome, and one worker had symptoms of a more proximal median nerve entrapment. No other symptoms or signs indicating entrapment neuropathy were encountered.
There were five cases of cervical syndrome, one case of thoracic outlet syndrome, three cases of supraspinous tendinitis, and five cases of peritendinitis of the wrist that could be diagnosed clinically (table 3). But these cases did not meet the set of criteria in the corresponding screening diagnoses of the method. Thus the criteria are "soft" for some disorders (eg, tension neck syndrome and bicipital tendinitis) and "hard" for most other disorders (eg, cervical syndrome, supraspinous tendinitis, tenosynovitis, and peritendinitis of the wrist and forearm). Cases diagnosed according to the "hard" criteria are very likely to be remarkably painful conditions not often encountered at workplaces. For epidemiologic purposes it would be more appropriate to use "softer" criteria so that disorders are detected in their early stages.
Testing the repeatability of the tests of the physical examination by having two persons examine the same individual contains many sources of error. As most of the test results rely on the subject's announcement of pain, paresthesiae, disturbed sensitivity, etc, it is probable that the subject learns the results of the test, the objectivity of the examination thereby being reduced.
Opinions differ about the value of physical examinations in epidemiologic studies. Comparisons between different groups of workers can be made on the level of subjective symptoms, objective signs, o r complexes of symptoms a n d signs. The "diagnoses" of the screening m e t h o d used i n t h e present study are an example of the last-mentioned type.
S o m e evidence has b e e n found which indicates t h e predictive value of certain s y m p t o m s a n d signs. Riihimaki et a1 (13) found that current n e c k pain better predicted t h e experiencing of neck pain after five years had passed t h a n did findings of degeneration i n cervical radiographs. In middle-age a n d older study groups degenerative changes cause s y m p t o m s a n d signs that cannot be singled out in a physical examination. T h u s t h e method would probably b e m o r e valuable w h e n relatively young populations are screened.