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Back pain and peripheral join pain in an industrial setting
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Back Pain and Peripheral Joint Pain in an Industrial Setting John R. Jefferson, MSc, Patrick J. McGrath, PhD ABSTRACT. Jefferson JR, McGrath PJ. Back pain and peripheral joint pain in an industrial setting. Arch Phys Med Rehabil 1996;77:385-90. Objective: To develop a self-reported low back pain (LBP) questionnaire and assess its usefulness in (1) describing the incidence of LBP in an industrial setting, compared to medical records and workers' compensation statistics; and (2) targeting specific work sites where the levels and patterns of pain suggest a need for specific intervention. Design: Survey data used from questionnaires, company medical records, and workers' compensation statistics. Setting: Industrial work site: aircraft engine factory. Participants: All employees (n = 306). Interventions: Questionnaire data, including LBP history, demographics, and body pain diagram scores, were compared to medical records and workers' compensation data over a 1year period. The body pain diagram quantified on a scale of 0 to 10 the subjective level of pain "at the end of an average shift" for six body regions. M a i n Outcome Measures: Pain diagram scores for different body regions were compared using Pearson Product correlations. Intercorrelations of body region pain scores were examined by factor analysis. Differences in mean LBP scores according to history and demographics were compared using paired t tests and ANOVA (p = .05). Results: The 1-year incidence of LBP by questionnaire was 69.3%. Occupational Health records revealed only 27% of the same workforce formally complained of LBP, while only 2.3% of the workforce lost time from work because of LBP. A clinically significant level of LBP was reported by 41% of respondents. Their level of LBP was not related to history of LBP, age, height, weight, smoking history, or amount of time in their job. Their level of LBP was somewhat related to their level of neck and peripheral joint pain. Conclusions: This questionnaire appears to be potentially useful in (1) identifying workers who are symptomatic at an early stage of their LBP problem; and (2) identifying pain patterns in different areas of the plant.
© 1996 by the American Congress of Rehabilitation Medicine and the American Academy of Physical Medicine and Rehabilitation ATA ON LOW BACK PAIN (LBP) incidence are typically collected in one of three ways: (1) self-reported quesD tionnaires or interviews; (2) medical records; and (3) workers' compensation statistics. Each of these data sources is useful in From the Department of Physical Therapy, University of South Alabama (Mr. Jefferson), and the Department of Psychology, Dalhousie University (Dr. McGrath), Mobile, AL. Submitted for publication May 16, 1995. Accepted in revised form September 16, 1995. Supported by a grant from Pratt & Whitney Canada, Inc., and an unrestricted grant from Bristol-Myers Squibb. No commercial party having a direct financial interest in the results of the research supporting this article has or will confer a benefit upon the authors or upon any organization with which the authors are associated. Reprint requests to John R. Jefferson, MSc, Department of Physical Therapy, 1504 Springhill Avenue, Room 1214, University of South Alabama, Mobile, AL 36604-3273. © 1996 by the American Congress of Rehabilitation Medicine and the American Academy of Physical Medicine and Rehabilitation
0003-9993/96/7704-352653.00/0
defining different aspects of the magnitude of the LBP problem. Data from workers' compensation claims are full of inherent biases, ~ including the influence of working conditions and the socioeconomic situation of the worker. In the US, back problems account for 19% of all workers' compensation claims.2'3 Not all workers are covered by workers' compensation programs and not all workers with LBP file a claim or lose time from work. Presumably the percentage of the workforce that is affected by LBP is higher than the percentage that is included in workers' compensation statistics. Using medical records, particularly in industrial settings that have in-house Occupational Health facilities, defines a different segment of the LBP population, giving a different picture of the magnitude of the LBP problem. Medical records define the percentage of the workforce that formally complains of LBP, whether or not the LBP results in time lost. Although a high incidence of workers' compensation claims for LBP is clearly undesirable, a high incidence of workers reporting to Occupational Health may not be undesirable and, in fact, may actually be beneficial. For example, the Chelsea Back Program 4'5 encouraged early reporting of LBP complaints to Occupational Health. Over a 2-year period, the incidence of workers reporting to Occupational Health increased by 56%. In the same time period, however, the incidence of workers' compensation claims for LBP decreased by 50%. Presumably early reporting of LBP problems allowed for earlier, more effective intervention. Self-reported lifetime incidence rates for LBP range from 49% to 70% in industrialized countries, with 1 month to 1 year prevalences from 12% to 35%. 6-15 This defines an even larger group of individuals. It appears, then, that up to 70% of the population will complain of LBP at some time in their lives, if asked about it. Only a subset of that group will show up at Occupational Health for assistance and a smaller subset will lose time from work. The method of collecting LBP data will not only define a different subset of the LBP population, it will also influence the opportunities for prevention. Preventative treatment often becomes more difficult and expensive the longer the disorder is established. In the North American workforce, it appears that the 7% to 10% of back-injured workers who develop "chronic LBP" (remaining off work for 6 months or longer), are responsible for 75% of sickness absence days and compensation cOStS. 6'16A7 Ideally, strategies to prevent LBP from reaching this chronic stage should be implemented as early as possible. By the time a worker is on workers' compensation, his or her LBP problem has resulted in time off work, and the opportunities for prevention of recurrence or long-term disability are limited. Early reporting to Occupational Health may offer greater opportunities for prevention. By the time a worker has reported to Occupational Health, however, the worker's symptoms have usually become severe enough that they are interfering with normal function. Moreover, reporting to Occupational Health may also encourage them to develop a sick role. Prevention strategies should ideally intervene before symptoms become this severe. This necessitates using a measurement of the prevalence of LBP symptoms before they reach the severity that function is affected, ie, before the workers report to Occupational Health. The purpose of this study was to develop a self-reported back
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Body DiscomfortChart: Please completethe following body discomfort chart. Indicate how you usually feel attheend of a normal shift. Pleaseput a number in eachcircle on the diagram. The number code is just below the diagram. < You may also add your own circles for any body part and fill in a number. >
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pain questionnaire for use in an industrial setting and assess its usefulness in (1) defining the magnitude of LBP at that setting; (2) comparing the self-reported level of LBP with the incidence of LBP problems defined by medical records and workers' compensation statistics; and (3) targeting specific work sites where the level of LBP suggests a need for intervention. The incidence of self-reported peripheral joint pain was also investigated. A review of the literature revealed no published studies that correlate the incidences of self-reported LBP and peripheral joint pain in an industrial setting. It is not known whether there are pain patterns in the workplace that would give clues to the etiology. For example, widespread pain would suggest a systemic cause, whereas pain only in the lower back and soles of the feet may suggest an external factor, such as hard floors. METHODS
Subjects. A questionnaire was distributed to all 322 employees of an aircraft engine factory near Halifax, Nova Scotia. The return rate on the questionnaires, which were returned anonymously, was 95% (306/322). Measures. The questionnaire was two pages in length, with four sections: (1) self-reported LBP history; (2) a body discomfort diagram; (3) demographic information; and (4) open-ended questions on perceived problem areas. Respondents were asked: "Have you had any (upper or lower) back p a i n . . , in the past 24 hours . . . . in the past 3 weeks . . . . in the past 3 months and . . . in the past year?" They were also asked to indicate whether the LBP had interfered with their normal daily activities. The questionnaire did not question the workers about the suspected cause of their back pain, ie, whether it was related to work, home, or leisure activities. A body diagram was included (fig 1) with six body regions labeled: neck or upper back; low back or buttocks; shoulders Arch Phys Med Rehabil Vol 77, April 1996
or upper arms; hands; knees; and feet. Respondents were instructed to place a number in the circle beside each labeled body region that indicated their level of discomfort "at the end of a normal shift." A horizontal pain scale with circles numbered from zero to 10 was provided for reference. Zero was described as "no discomfort" and 10 was described as "extremely painful." No descriptors were given for numbers 1 through 9. The six body regions were chosen from a pilot body diagram that had originally included 28 body regions. The six regions chosen were those with the highest mean values from 111 pilot questionnaires. The following open-ended questions were asked: (1) What activities in your department do you find the most physical demanding on your upper or lower back? (2) Why are they so demanding? (3) What practical changes would you suggest to make these tasks easier? Treatment of data. Data analysis was performed using SPSS on an IBM compatible PC. Relationships between pain diagram scores for different body regions were determined using Pearson product moment correlation analyses. Intercorrelations of body region pain scores were examined by performing a principle components factor analysis. Differences in mean LBP scores according to LBP history and demographics (age, height, weight, and smoking history) were compared using paired t tests and analysis of variance (ANOVA) tests. These were evaluated for significance at a probability level of .05. RESULTS The incidence of self-reported LBP was as follows: 69.3% of respondents reported having had LBP within the past year; 50.0% of respondents reported LBP within the past 3 months; 33.7% of respondents reported LBP within the past 3 weeks; and 18.3% of respondents reported having had LBP within the past 24 hours. An incidence of 69.3% is somewhat higher than reported in the literature for a 1-year period, but is consistent with rates reported for a longer time frame. 644 Among the 69.3% of respondents that reported LBP, 41% indicated that their LBP had interfered with their daily activities. This means that 28.4% of the workforce reported LBP within the previous year that interfered with their daily activities. Data obtained from Occupational Health records indicated that 27% of the workforce presented to Occupational Health with complaints of LBP in the 1-year period before distribution of the questionnaire. In that same time period, only 2.3% of the workforce lost time from work because of LBP. The distribution of pain scores for the six body regions is shown in figure 2. Clearly, some body regions are reported as being more painful than others at the end of a normal shift. Because of the subjective nature of pain, it is inappropriate to compare pain scores between individuals. However, within individuals it is useful to compare pain scores for different body regions. Likewise, mean pain scores of a population for one body region can be compared with mean pain scores for other body regions within the same population. Thus, if a person or group of persons reports a "5 out of 10" for one body region and a "3 out of 10" for another body region, the former body region.canbe considered to be more painful, on average, than the latter. It is not known, however, whether there is a particular level of pain that can be considered as "clinically significant" across a group of subjects, either in terms of interference with normal activities, or in predicting long-term problems. Nor is it known how the significance of a particular pain level varies from one body region to another. Figure 2 shows that in the case of hand pain, 70% of respondents reported a zero pain level and only 15% of respondents reported a pain level of 3 or higher. In the
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case of LBP, however, 29% of respondents reported a zero pain level and 55% of respondents reported a level of pain that was 3 or higher. This suggests that LBP is a greater problem than hand pain for this plant. Workers' compensation statistics provide a different impression for this plant. During the 2-year period before questionnaire distribution, the number one cause of lost time was hand injuries, accounting for 45.2% of days lost, whereas LBP accounted for 36.1% of days lost. This was because a few employees with hand problems (eg, carpal tunnel) were responsible for a large percentage of total days lost. Thus, the questi0~nnaire data provides a different picture of the prevalence of LBP and extremity pain than that obtained from medical records or workers' compensation statistics. Figure 3 shows the mean pain scores for the six body regions across the whole plant, and for three selected departments. In "Dept. 14: Systems," workers are sedentary, spending most of their day at a desk. They reported, on average, a moderate level of neck pain and LBP, but low levels of upper and lower extremity joint pain. In "Dept. 3: Cutter Grind & Tooling," workers spend most of their day standing on the shop floor, operating manual and computerized machines. They reported, on average, a rather high mean level of spinal and lower extremity pain, with the average level of foot pain and LBP reported as greatei" than 5 on the pain scale. In "Dept. 8: Materials & Shipping," workers are in varied positions throughout the day, with frequent lifting and carrying, but infrequent static standing or sitting. They reported, on average, a low level of pain complaints in all body regions. The majority of the plant workers are on the shop floor, and in most of the departments LBP and lower extremity pain gave
the highest mean pain scores. The plant-wide mean level of self-reported LBP and foot pain were 3.16 and 3.65, respectively. The departments with the three highest reported LBP scores were also the departments with the highest reported foot pain scores. Plant-wide, however, there was only a small correlation between LBP and foot pain (r = .21, p < .001). Somewhat stronger correlations were found between foot and knee pain (r = .50, p < .001), hand and arm pain (r = .46, p < .001), and arm and neck pain (r = .46, p < .001). Table 1 shows the correlation matrix for all six body region pain scores. A principle components factor analysis on the six body region pain scores gave a 3 factor solution (table 2), with three rather distinct clusters or "pain patterns." These can be described as an upper extremity factor (factor 1), a lower extremity factor (factor 2), and a spinal factor (factor 3). Neck pain can be seen to influence both the upper extremity and spinal factors but LBP is not intercorrelated with either the upper extremity or lower extremity factors. There was a significant difference in the mean LBP scores of workers with a reported history of LBP versus those with no • eported history of LBP. Table 3 lists the mean LBP scores grouped by history of LBP. Three additional categories were added to the raw data in table 4. The "Acute" category was defined as reporting LBP either in the past 24 hours or in the past 3 weeks. The mean reported level of LBP in the Acute group was 4.5. "Nonacute" was defined as reporting LBP either in the past 3 months or the past 1 year, but not within the past Table 1: Correlation Matrix of Pain Scores From Six Body Regions (n = 285)
LBP Arm Hand Knee Foot
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.326* .460* .258* .065 ~ .133 t
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Table 2: Factor Analysis on Six Body Region Pain Scores: Rotated Factor Matrix Loadings (n = 285)
Table 4: Mean LBP Score According to Category
Variable (Body Region Pain Score)
Factor 1 (Upper Extremity)
Factor 2 (Lower Extremity)
Factor 3 (Spinal)
Neck LBP Arm Hand Knee Foot
46559 -.03603 .78360* .84164" -.02727 .22579
-.10020 .28757 .13765 .08057 .85897* .83235"
.70150* .83841* .28979 -.03450 .18427 .01782
Values listed are measurements of the correlation between observed measurements (body region pain scores) and three underlying factors. * These values highlight the strong intercorrelations of arm and hand pain to upper extremity factor, knee and foot pain to lower extremity factor, and neck and back pain to spinal factor.
3 weeks. The mean reported level of LBP in the Nonacute group was 3.2. "Chronic" was defined as reporting a history of both Acute LBP (ie, within the past 3 weeks) and Nonacute LBP (ie, within 3 months to 1 year). The mean reported level of LBP in the Chronic group was 5.3. An ANOVA on the No LBP, Acute, Nonacute, and Chronic groups showed a significant difference between mean LBP scores (/7 < .001). Table 4 also divides workers reporting a history of LBP into those who reported interference with Activities of Daily Living (ADL) (41%) versus those who reported no interference with ADL (59%). T tests performed on the mean LBP scores of workers reporting ADL interference versus no ADL interference revealed no difference between the two groups (Table 4). Workers who reported ADL interference, on average, did not report a higher level of LBP than workers reporting no ADL interference. There was a slight negative correlation between workers' reported level of LBP and the length of time in their current departments (r = -.12, p = .05). A t test of the mean LBP scores for smokers versus nonsmokers showed no significant difference between groups (p = .14). The nonsmokers had a slightly higher mean LBP score (n = 178, mean = 3.27) than the smokers (n = 75, mean = 2.76). An ANOVA for the variables of age, height, and weight versus LBP scores revealed no significant difference between groups (p values: age, p = .62; height, p = .52; weight, p = .13). Nonsignificant trends showed a higher mean LBP score with workers in the shortest height category and in the heaviest weight category. DISCUSSION
Prevalence of LBP The incidence of self-reported LBP (69.3%) was much higher than the incidence of LBP complaints reported to Occupational Health (27%), and much higher than the incidence of workers' compensation claims for LBP (2.3%). Although lifetime incidence rates for LBP of up to 70% are common in the literature, 1 year prevelances are typically less than 35%. 6-j5 It is not known whether the unusually high 1 year prevalence obtained here is specific to this particular plant or specific to this particular questionnaire. The workers were not questioned as to the Table 3: Mean LBP Score According to LBP History (n = 2851 LBP History No LBP LBP past LBP past LBP past LBP past
24hrs 3wks 3mos lyr
n
Mean LBP
84 52 98 146 201
1.02 5.17 4.94 4.49 4.06
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LBP History by Category
Mean LBP for Category
Acute Nonacute Chronic
4.50 3.22 5.30
No ADL Interference 4.54 2.99 5.16
Interference With ADL 4.45 3.63 4.71
p .842 .999 .940
Mean LBP scores according to whether the reported LBP interfered with ADL are also listed (p values from t tests).
cause of their LBP, nor was it assumed that any reported pain was related to the work environment. Only a minority of workers can attribute their LBP onset to an obvious, single spinal injury. ~8-2~In the absence of significant trauma, most LBP, like other musculoskeletal disorders, is probably caused by the cumulative effects of factors such as poor posture and faulty body mechanics. For most full-time employees, about half of their waking adult lives will be spent at, or traveling to and from, their workplace. Therefore, regardless of where the "onset" of LBP symptoms is reported, workplace activities will likely have played a part in the development of workers' LBP symptoms. The questionnaire data suggests a wide prevalence of LBPr whereas workers' compensation statistics alone might suggest that there is no significant problem with LBP at this particular plant. It appears that the workers' compensation statistics reveal only the "tip of the iceberg." The questionnaire may have identified a larger potential LBP problem at this plant than would otherwise have been evident. The average level of LBP for the whole plant was greater than 3 of 10, and in some departments the average LBP level was greater than 5 of 10, "at the end of an average shift." This is much higher than anticipated by the investigators. This plant is a highly robotized operation, with the latest in mechanized assistive devices and very low employee turnover and absenteeism rates. 24The job descriptions do not involve strenuous lifting, bending, or twisting tasks that would explain such a high level of low back discomfort. The mean level of LBP increased according to how recently the worker reported an "episode" of LBP within the previous year. The group with the highest average level of LBP was the "chronic" group, those workers ,who reported both acute and nonacute episodes (table 4). Thi]s, both the time since previous episodes and the frequency of previous episodes seems to influence the workers' perception of or susceptibility to daily LBP in the workplace. There was no difference in the mean LBP scores of workers who did or did not report interference with ADL during their previous episodes. This suggests that the severity of previous episodes does not have an influence on the perception of daily LBP in the workplace or, rather, that interference with ADL may not be correlated with pain. Other factors may be more important.
Implications for Intervention Although most patients recover spontaneously from acute episodes of LBP, many will suffer a recurrence, and subsequent injuries are often more severe and long lasting. 12'~5-28Workers who develop "chronic LBP" (remaining off work for 6 months or longer), are responsible for 70% to 79% of sickness absence days and compensation c o s t s . 3'6'14'16'17 AS the duration of LBP disability increases, the chances for successful return to longterm reemployment become progressively smaller.28~29 Preventative programs will not eliminate LBP, but they can potentially reduce the magnitude of the LBP problem, particularly if they can reduce the rate of recurrence and chronieity.3° Attempting to prevent LBP after a worker has already complained to Occupational Health, however, is akin to trying to
BACK AND PERIPHERAL JOINT PAIN, Jefferson
prevent heart disease after a patient has already complained of angina. Ideally, strategies to prevent LBP, or at least, to prevent loss of work-time due to LBP, should intervene before the worker' s symptoms become severe enough that he or she seeks medical aid. The use of questionnaire data may have the advantage of identifying workers at risk for debilitating LBP while their LBP problem is in an early stage of progression, ie, a stage in which the symptoms are not sufficiently severe to interfere with normal function of daily activities. Likewise, questionnaire data may provide an indication of the effectiveness of intervention strategies, such as ergonomic changes or back education. Reducing the mean LBP level from 5 to 2, for example, may be evidence of effective primary prevention long before the long-term effects of the intervention on workers' compensation statistics is known.
Pain Patterns Pain drawings have been used for back pain patients to help distinguish patients with distinct anatomic patterns of pain from patients with nonanatomic patterns of pain. Widespread pain in a nonanatomic distribution may reflect the affective component of patients' pain and their psychological distress.3~ The inclusion of peripheral joint discomfort in the body diagram provided a "control" for the workers' LBP complaints. If a worker complains of a discomfort level of 5 for LBP, but a level of 1 or 2 in other body regions, then it is more likely that there is a distinct LBP problem than if the worker complained of a discomfort level of 5 everywhere, which may be due to a systemic problem such as rheumatic disease. The correlation matrix (table 1) shows that there is a statistically significant correlation between spinal pain and peripheral joint pain. The correlation values, however, are not very large, ranging from .12 to .46. The intercorrelations from the factor analysis (table 2) suggests little correlation between spinal and peripheral joint pain, except for a moderate influence of neck pain on the upper extremity factor. The factor analysis suggests that there are three clusters or "pain patterns": neck and back pain; foot and knee pain; and hand and arm pain. These make sense conceptually because of the anatomic and ergonomic linkage of these body regions. Bent forward posture will affect neck and back pain, standing on hard floors will affect foot and knee pain, and gripping and lifting movements will affect hand and arm pai n . Use Of the body diagram may also prove useful as an outcome measure for ergonomic intervention. Changes to a work site may reduce discomfort in one body region, but increase discomfort in another region. The body diagram provides quantification of the workers' subjective complaints that can help influence decisions on the effectiveness of the intervention strategies employed. Targeting Work Sites The difference in pain scores in individual departments suggests that different intervention strategies may be needed in different areas of the plant. It also helps in formulating ideas as to the causative factors, or at least in identifying where further investigation is needed to ascertain the appropriate intervention. This is illustrated by the departments displayed in figure 3. In Dept. 14, for example, the high level of spinal joint discomfort but low level of peripheral joint discomfort fits with the sedentary job description. Interventions should include changes to seating and monitor heights and frequent breaks from sitting. In Dept. 8, there does not appear to be any significant problems, on average. Interestingly, this department, Materials and
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Shipping, is where the greatest amount of materials handling takes place, with frequent lifting, carrying, and bending while packing and unpacking parts of various sizes. Contrasting this is Dept. 3, an area reporting a high average level of spinal and lower extremity discomfort. This area involves much less lifting and carrying but, conversely, much more static standing and sitting while operating machines. This suggests that intervention may need to include more variation of job description, with less static loading. The high level of LBP and foot pain in this and other departments is interesting. The question arises as to whether these scores are related via a common causative factor--eg, the hard concrete floors. On face value, the hard floor is the most obvious explanation for the high level of foot pain and i t may also explain the high incidence of LBP. An alternate explanation however, is that the high incidence of LBP is due to the workers maintaining a static bent-forward posture over their machines, irrespective of the floor surface. Interpreting the pain patterns has implications for planning intervention strategies. If hard flooring is the cause, then efforts should be made to cushion the floor and/or reduce the amount of time standing. If faulty posture is the cause, then efforts should be directed towards back care education and training, and possibly ergonomic changes (eg, bench height and reach or use of footrests). Use of a questionnaire, with inclusion of a body diagram, may help direct and assess the effectiveness of intervention strategies. There was no attempt in this study to correlate the level of spinal or peripheral joint pain with worker productivity. It is not known what level of pain interferes with a worker's performance sufficiently to cause a decrease in productivity. Presumably this will vary with the specific job demands for a given joint region and will vary among different joints and between different workers. Use of a pain questionnaire in conjunction with productivity data may help assess not only the effectiveness of intervention strategies in altering workers pain levels but also the cost-effectiveness of these strategies. In addition, use of the questionnaire may have served a constrnctive role in management-employee relations. By including all employees in the distribution of the questionnaire, it makes them aware of management's efforts to identify LBP and peripheral joint problems at an early stage. This suggests that management is willing to listen to employee input and not rely only on compensation statistics in efforts to improve the work environment. This questionnaire has been neither validated nor tested for reliability in this setting. A pilot questionnaire was distributed to a group of the same employees (n = 151) 6 months previous to the present questionnaire. It contained the same questions on LBP history, but a different pain diagram. In the pilot data 74% of respondents reported having had LBP within the past year, suggesting that the 69.3% obtained here was not an anomaly. Because of the anonymity of both the pilot questionnaire and the present study, however, formal tests of validity or reliability were not possible. The reproducibility of self-reported LBP incidence has been estimated by Biering-Sorenson. 32 At intervals of 6 months the question of ever having had LBP was answered yes or no consistently by 81% of subjects on the two occasions. Westrin 26 reported an 87% concordance between two interviewers regarding the lifetime incidence of LBP. Most of his subjects were interviewed twice on the same day. It is not known how the reliability of self-reported LBP varies according to acuteness of the symptoms. The reliability of self-reported LBP over a 1-year period may be higher than that of lifetime incidence. The testretest reliability of the pain drawing instrument on chronic pain
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patients has been estimated by Margolis and coworkers 33 at 88.2% for an average time interval of 71 days. The relJroducibility of pain drawings for acute joint pain is not known.
SUMMARY The questionnaire obtained useful information at very little cost. It identified a widespread prevalence of LBP, which was not evident from medical records. This may encourage the implementation of intervention strategies at an early stage in workers' LBP complaints, hopefully to better prevent long term LBP problems. Inclusion of the body pain diagram was particularly useful. Although plant-wide there does not appear to be a strong correlation between spinal and peripheral joint pain, in specific departments, and especially in individual workers, there were definite and specific pain patterns. The questionnaire thus can help target specific departments (or individuals) where different complaints suggest the need for different interventions. It also raised new questions as to the etiology of LBP complaints by revealing different pain patterns at different job descriptions. It appears that the questionnaire will also be a useful tool for obtaining outcome measures of intervention strategies, for both spinal and peripheral joint complaints. The high rate of return suggests a high level of acceptance and ease of completion by industrial workers.
Acknowledgments: The assistance of Sharon Chisholm, RN, and Mabel Smith, RN, in data collection and that of Dr. G. Reid in data analysis are gratefully acknowledged. References 1. Abenhaim LL, Suissa S. Importance and economic burden of occupational back pain: A study of 200 cases representative of Quebec. J Occup Med 1987;29:670-4. 2. Klein BP, Jensen RC, Sanderson LM. Assessment of worker's compensation claims for back strains/sprains. J Occup Med 1984; 26:443-8. 3. Spengler DM, Bigos SJ, Martin NA, Zeh J, Fisher L, Nachemson A. Back injuries in industry: A retrospective study I: Overview and cost analysis. Spine 1986; 11:241-5. 4. Fitzler SL, Berger RA. Attitudinal change: the Chelsea back program. Occ Health Safety 1982;51:24-6. 5. Fitzler SL, Berger RA. Chelsea back program: one year later. Occ Health Safety 1983;52:52-4. 6. Frymoyer JW, Pope MH, Clements JH, Wilder DG, MacPherson B, Ashikaga T. Risk factors in low back pain. J Bone Joint Surg Am 1983;65:213-18. 7. Hirsch C, Jonsson B, Lewin T. Low back symptoms in a Swedish female population. Clan Orthop 1969;63:171-6. 8. Svensson H-O, Andersson GBJ, Johansson S, Wilhelmsson C. A retrospective study Of low back pain in 38- to 64-year-old women. Frequency and occurrence and impact on medical services. Spine 1988; 13:548-52. 9. Svensson H-O, Andersson GBJ. Low back pain in 40-47 year old men. I: Frequency of occurrence and impact on medical services. Scand J Rehabil Med 1982; 14:47-53. 10. Gyntelberg F. One year incidence of low back pain among male residents of Copenhagen aged 40-59. Dan Med Bull 1974;21:306.
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11. Biering-Sorenson F. Low back trouble in a general population of 30-, 40-, 50-, and 60-year-old men and women. Study design, representativeness and basic results. Dan Med Bull 1982;29:289-99. 12. Nagi SZ, Riley LE, Newby LG. A social epidemiology of back pain in a general population. J Chron Dis 1973;26:769-79. 13. Lloyd MH, Gould S, Soutar CA. Epidemiologic study of back pain in minors and office workers. Spine 1986;11:136-140. 14. Andersson GBJ, Pope MH, Frymoyer JW, Snook S. Epidemiology and cost. In: Pope MH, Andersson GBJ, Frymoyer JW, Chaffin DB, editors. Occupational low back pain: assessment, treatment and prevention. St. Louis: Mosby, 1991:95-113. 15. Nachemson AL. The lumbar spine: an orthopaedic challenge. Spine 1976; 1:59-71. 16. Bigos SJ, Spengler DM, Martin NA, Zeh J,Fisher L, Nachemson A. Back injuries in industry: a;retrospective study III: employeerelated factors. Spine 1986;3:252-6. 17. Abenhaim L, Suissa S, Rossignoi M. Risk of recurrence of occupational back pain over a three year follow-up. Brit J Ind Med 1988;45:829-3. 18. Andersson GBJ, Frymoyer JW. Treatment of the acutely injured worker. In: Pope MH, Andersson GBJ, Frymoyer JW, Chaffin DB, editors. Occupational low back pain: assessment, treatment and prevention. St. Louis: Mosby, 1991:183. 19. Troup JDG, Martin JW, Lloyd DC. Back pain in industry: a prospective study. Spine 1981;6:61-9. 20. Grieve GP. Common vertebral joint problems. 2nd ed. Edinburgh: Churchill Livingstone, 1988:188-189. 21. Manning DP, Mitchell RG, Blanchfield LP. Body movements and events contributing to accidental and non-accidental back injuries. Spine 1984;9:734-9. 22. McKenzie RA. The lumbar spine: mechanical diagnosis and therapy. Waikanae: Spinal Publications 1981:28. 23. Porterfield JA, DeRosa C. Mechanical low back pain: perspectives in functional anatomy. Philadelphia; Saunders, 1991:130. 24. Jones D. Robo-Shop. Globe & Mall Report on Business 1994; 10(9):54-62. 25. Leavitt SS, Johnston TL, Beyer RD. The process of recovery. Patterns in industrial back injury. Part 2: predicting outcomes from the early case data. Ind Med Surg 1971;40:7-15. 26. Westrin CG. Low back sicklisting. A nosological and medical insurance investigation. Scand J Soc Med [supp] 1973;7:1-116. 27. Horal J. The clinical appearance of low back pain disorders in the city of Gothenburg, Sweden. Comparisons of incapacitated probands and matched controls. Acta Orthop Scand [supp] 1969; 118:1109. 28. Magora A, Taustein I. An investigation of the problem of sickleave in the patient suffering from low back pain. lnd Med Surg 1969; 38:398-408. 29. McGill CM. Industrial back problems. A control program. J Occup Med 1968; 10:174-8. 30. Andersson GBJ. Concepts in Prevention. In: Pope MH, Andersson GBJ, Frymoyer JW, Chaffin DB, editors. Occupational low back pain: assessment, treatment and prevention. St. Louis: Mosby, 1991:2/1-6. 31. Ransford AO, Cairns D, Mooney V. The pain drawing as an aid to the psychological evaluation of patients with low back pain. Spine 1976; 1:127-34. 32. Biering-Sorenson F. A prospective study of low back pain in a general population, I: occurrence, recurrence and aetiology. Scand J Rehab Med 1983a; 15:71-9. 33. Margolis RB, Chibnall ST, Tait RC. Test-retest reliability of the pain drawing instrument. Pain 1988;33:49-51.
Back Pain and Peripheral Joint Pain in an Industrial Setting John R. Jefferson, MSc, Patrick J. McGrath, PhD ABSTRACT. Jefferson JR, McGrath PJ. Back pain and peripheral joint pain in an industrial setting. Arch Phys Med Rehabil 1996;77:385-90. Objective: To develop a self-reported low back pain (LBP) questionnaire and assess its usefulness in (1) describing the incidence of LBP in an industrial setting, compared to medical records and workers' compensation statistics; and (2) targeting specific work sites where the levels and patterns of pain suggest a need for specific intervention. Design: Survey data used from questionnaires, company medical records, and workers' compensation statistics. Setting: Industrial work site: aircraft engine factory. Participants: All employees (n = 306). Interventions: Questionnaire data, including LBP history, demographics, and body pain diagram scores, were compared to medical records and workers' compensation data over a 1year period. The body pain diagram quantified on a scale of 0 to 10 the subjective level of pain "at the end of an average shift" for six body regions. M a i n Outcome Measures: Pain diagram scores for different body regions were compared using Pearson Product correlations. Intercorrelations of body region pain scores were examined by factor analysis. Differences in mean LBP scores according to history and demographics were compared using paired t tests and ANOVA (p = .05). Results: The 1-year incidence of LBP by questionnaire was 69.3%. Occupational Health records revealed only 27% of the same workforce formally complained of LBP, while only 2.3% of the workforce lost time from work because of LBP. A clinically significant level of LBP was reported by 41% of respondents. Their level of LBP was not related to history of LBP, age, height, weight, smoking history, or amount of time in their job. Their level of LBP was somewhat related to their level of neck and peripheral joint pain. Conclusions: This questionnaire appears to be potentially useful in (1) identifying workers who are symptomatic at an early stage of their LBP problem; and (2) identifying pain patterns in different areas of the plant.
© 1996 by the American Congress of Rehabilitation Medicine and the American Academy of Physical Medicine and Rehabilitation ATA ON LOW BACK PAIN (LBP) incidence are typically collected in one of three ways: (1) self-reported quesD tionnaires or interviews; (2) medical records; and (3) workers' compensation statistics. Each of these data sources is useful in From the Department of Physical Therapy, University of South Alabama (Mr. Jefferson), and the Department of Psychology, Dalhousie University (Dr. McGrath), Mobile, AL. Submitted for publication May 16, 1995. Accepted in revised form September 16, 1995. Supported by a grant from Pratt & Whitney Canada, Inc., and an unrestricted grant from Bristol-Myers Squibb. No commercial party having a direct financial interest in the results of the research supporting this article has or will confer a benefit upon the authors or upon any organization with which the authors are associated. Reprint requests to John R. Jefferson, MSc, Department of Physical Therapy, 1504 Springhill Avenue, Room 1214, University of South Alabama, Mobile, AL 36604-3273. © 1996 by the American Congress of Rehabilitation Medicine and the American Academy of Physical Medicine and Rehabilitation
0003-9993/96/7704-352653.00/0
defining different aspects of the magnitude of the LBP problem. Data from workers' compensation claims are full of inherent biases, ~ including the influence of working conditions and the socioeconomic situation of the worker. In the US, back problems account for 19% of all workers' compensation claims.2'3 Not all workers are covered by workers' compensation programs and not all workers with LBP file a claim or lose time from work. Presumably the percentage of the workforce that is affected by LBP is higher than the percentage that is included in workers' compensation statistics. Using medical records, particularly in industrial settings that have in-house Occupational Health facilities, defines a different segment of the LBP population, giving a different picture of the magnitude of the LBP problem. Medical records define the percentage of the workforce that formally complains of LBP, whether or not the LBP results in time lost. Although a high incidence of workers' compensation claims for LBP is clearly undesirable, a high incidence of workers reporting to Occupational Health may not be undesirable and, in fact, may actually be beneficial. For example, the Chelsea Back Program 4'5 encouraged early reporting of LBP complaints to Occupational Health. Over a 2-year period, the incidence of workers reporting to Occupational Health increased by 56%. In the same time period, however, the incidence of workers' compensation claims for LBP decreased by 50%. Presumably early reporting of LBP problems allowed for earlier, more effective intervention. Self-reported lifetime incidence rates for LBP range from 49% to 70% in industrialized countries, with 1 month to 1 year prevalences from 12% to 35%. 6-15 This defines an even larger group of individuals. It appears, then, that up to 70% of the population will complain of LBP at some time in their lives, if asked about it. Only a subset of that group will show up at Occupational Health for assistance and a smaller subset will lose time from work. The method of collecting LBP data will not only define a different subset of the LBP population, it will also influence the opportunities for prevention. Preventative treatment often becomes more difficult and expensive the longer the disorder is established. In the North American workforce, it appears that the 7% to 10% of back-injured workers who develop "chronic LBP" (remaining off work for 6 months or longer), are responsible for 75% of sickness absence days and compensation cOStS. 6'16A7 Ideally, strategies to prevent LBP from reaching this chronic stage should be implemented as early as possible. By the time a worker is on workers' compensation, his or her LBP problem has resulted in time off work, and the opportunities for prevention of recurrence or long-term disability are limited. Early reporting to Occupational Health may offer greater opportunities for prevention. By the time a worker has reported to Occupational Health, however, the worker's symptoms have usually become severe enough that they are interfering with normal function. Moreover, reporting to Occupational Health may also encourage them to develop a sick role. Prevention strategies should ideally intervene before symptoms become this severe. This necessitates using a measurement of the prevalence of LBP symptoms before they reach the severity that function is affected, ie, before the workers report to Occupational Health. The purpose of this study was to develop a self-reported back
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BACK AND PERIPHERAL JOINT PAIN, Jefferson
Body DiscomfortChart: Please completethe following body discomfort chart. Indicate how you usually feel attheend of a normal shift. Pleaseput a number in eachcircle on the diagram. The number code is just below the diagram. < You may also add your own circles for any body part and fill in a number. >
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pain questionnaire for use in an industrial setting and assess its usefulness in (1) defining the magnitude of LBP at that setting; (2) comparing the self-reported level of LBP with the incidence of LBP problems defined by medical records and workers' compensation statistics; and (3) targeting specific work sites where the level of LBP suggests a need for intervention. The incidence of self-reported peripheral joint pain was also investigated. A review of the literature revealed no published studies that correlate the incidences of self-reported LBP and peripheral joint pain in an industrial setting. It is not known whether there are pain patterns in the workplace that would give clues to the etiology. For example, widespread pain would suggest a systemic cause, whereas pain only in the lower back and soles of the feet may suggest an external factor, such as hard floors. METHODS
Subjects. A questionnaire was distributed to all 322 employees of an aircraft engine factory near Halifax, Nova Scotia. The return rate on the questionnaires, which were returned anonymously, was 95% (306/322). Measures. The questionnaire was two pages in length, with four sections: (1) self-reported LBP history; (2) a body discomfort diagram; (3) demographic information; and (4) open-ended questions on perceived problem areas. Respondents were asked: "Have you had any (upper or lower) back p a i n . . , in the past 24 hours . . . . in the past 3 weeks . . . . in the past 3 months and . . . in the past year?" They were also asked to indicate whether the LBP had interfered with their normal daily activities. The questionnaire did not question the workers about the suspected cause of their back pain, ie, whether it was related to work, home, or leisure activities. A body diagram was included (fig 1) with six body regions labeled: neck or upper back; low back or buttocks; shoulders Arch Phys Med Rehabil Vol 77, April 1996
or upper arms; hands; knees; and feet. Respondents were instructed to place a number in the circle beside each labeled body region that indicated their level of discomfort "at the end of a normal shift." A horizontal pain scale with circles numbered from zero to 10 was provided for reference. Zero was described as "no discomfort" and 10 was described as "extremely painful." No descriptors were given for numbers 1 through 9. The six body regions were chosen from a pilot body diagram that had originally included 28 body regions. The six regions chosen were those with the highest mean values from 111 pilot questionnaires. The following open-ended questions were asked: (1) What activities in your department do you find the most physical demanding on your upper or lower back? (2) Why are they so demanding? (3) What practical changes would you suggest to make these tasks easier? Treatment of data. Data analysis was performed using SPSS on an IBM compatible PC. Relationships between pain diagram scores for different body regions were determined using Pearson product moment correlation analyses. Intercorrelations of body region pain scores were examined by performing a principle components factor analysis. Differences in mean LBP scores according to LBP history and demographics (age, height, weight, and smoking history) were compared using paired t tests and analysis of variance (ANOVA) tests. These were evaluated for significance at a probability level of .05. RESULTS The incidence of self-reported LBP was as follows: 69.3% of respondents reported having had LBP within the past year; 50.0% of respondents reported LBP within the past 3 months; 33.7% of respondents reported LBP within the past 3 weeks; and 18.3% of respondents reported having had LBP within the past 24 hours. An incidence of 69.3% is somewhat higher than reported in the literature for a 1-year period, but is consistent with rates reported for a longer time frame. 644 Among the 69.3% of respondents that reported LBP, 41% indicated that their LBP had interfered with their daily activities. This means that 28.4% of the workforce reported LBP within the previous year that interfered with their daily activities. Data obtained from Occupational Health records indicated that 27% of the workforce presented to Occupational Health with complaints of LBP in the 1-year period before distribution of the questionnaire. In that same time period, only 2.3% of the workforce lost time from work because of LBP. The distribution of pain scores for the six body regions is shown in figure 2. Clearly, some body regions are reported as being more painful than others at the end of a normal shift. Because of the subjective nature of pain, it is inappropriate to compare pain scores between individuals. However, within individuals it is useful to compare pain scores for different body regions. Likewise, mean pain scores of a population for one body region can be compared with mean pain scores for other body regions within the same population. Thus, if a person or group of persons reports a "5 out of 10" for one body region and a "3 out of 10" for another body region, the former body region.canbe considered to be more painful, on average, than the latter. It is not known, however, whether there is a particular level of pain that can be considered as "clinically significant" across a group of subjects, either in terms of interference with normal activities, or in predicting long-term problems. Nor is it known how the significance of a particular pain level varies from one body region to another. Figure 2 shows that in the case of hand pain, 70% of respondents reported a zero pain level and only 15% of respondents reported a pain level of 3 or higher. In the
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case of LBP, however, 29% of respondents reported a zero pain level and 55% of respondents reported a level of pain that was 3 or higher. This suggests that LBP is a greater problem than hand pain for this plant. Workers' compensation statistics provide a different impression for this plant. During the 2-year period before questionnaire distribution, the number one cause of lost time was hand injuries, accounting for 45.2% of days lost, whereas LBP accounted for 36.1% of days lost. This was because a few employees with hand problems (eg, carpal tunnel) were responsible for a large percentage of total days lost. Thus, the questi0~nnaire data provides a different picture of the prevalence of LBP and extremity pain than that obtained from medical records or workers' compensation statistics. Figure 3 shows the mean pain scores for the six body regions across the whole plant, and for three selected departments. In "Dept. 14: Systems," workers are sedentary, spending most of their day at a desk. They reported, on average, a moderate level of neck pain and LBP, but low levels of upper and lower extremity joint pain. In "Dept. 3: Cutter Grind & Tooling," workers spend most of their day standing on the shop floor, operating manual and computerized machines. They reported, on average, a rather high mean level of spinal and lower extremity pain, with the average level of foot pain and LBP reported as greatei" than 5 on the pain scale. In "Dept. 8: Materials & Shipping," workers are in varied positions throughout the day, with frequent lifting and carrying, but infrequent static standing or sitting. They reported, on average, a low level of pain complaints in all body regions. The majority of the plant workers are on the shop floor, and in most of the departments LBP and lower extremity pain gave
the highest mean pain scores. The plant-wide mean level of self-reported LBP and foot pain were 3.16 and 3.65, respectively. The departments with the three highest reported LBP scores were also the departments with the highest reported foot pain scores. Plant-wide, however, there was only a small correlation between LBP and foot pain (r = .21, p < .001). Somewhat stronger correlations were found between foot and knee pain (r = .50, p < .001), hand and arm pain (r = .46, p < .001), and arm and neck pain (r = .46, p < .001). Table 1 shows the correlation matrix for all six body region pain scores. A principle components factor analysis on the six body region pain scores gave a 3 factor solution (table 2), with three rather distinct clusters or "pain patterns." These can be described as an upper extremity factor (factor 1), a lower extremity factor (factor 2), and a spinal factor (factor 3). Neck pain can be seen to influence both the upper extremity and spinal factors but LBP is not intercorrelated with either the upper extremity or lower extremity factors. There was a significant difference in the mean LBP scores of workers with a reported history of LBP versus those with no • eported history of LBP. Table 3 lists the mean LBP scores grouped by history of LBP. Three additional categories were added to the raw data in table 4. The "Acute" category was defined as reporting LBP either in the past 24 hours or in the past 3 weeks. The mean reported level of LBP in the Acute group was 4.5. "Nonacute" was defined as reporting LBP either in the past 3 months or the past 1 year, but not within the past Table 1: Correlation Matrix of Pain Scores From Six Body Regions (n = 285)
LBP Arm Hand Knee Foot
Neck
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Hand
Knee
.326* .460* .258* .065 ~ .133 t
.228* .124 ~ .331" ,209*
.456* .149' .269*
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* p --< .001. t p < .01. * p --< ,05. p > .05 (NS).
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BACK AND PERIPHERAL JOINT PAIN, Jefferson !
Table 2: Factor Analysis on Six Body Region Pain Scores: Rotated Factor Matrix Loadings (n = 285)
Table 4: Mean LBP Score According to Category
Variable (Body Region Pain Score)
Factor 1 (Upper Extremity)
Factor 2 (Lower Extremity)
Factor 3 (Spinal)
Neck LBP Arm Hand Knee Foot
46559 -.03603 .78360* .84164" -.02727 .22579
-.10020 .28757 .13765 .08057 .85897* .83235"
.70150* .83841* .28979 -.03450 .18427 .01782
Values listed are measurements of the correlation between observed measurements (body region pain scores) and three underlying factors. * These values highlight the strong intercorrelations of arm and hand pain to upper extremity factor, knee and foot pain to lower extremity factor, and neck and back pain to spinal factor.
3 weeks. The mean reported level of LBP in the Nonacute group was 3.2. "Chronic" was defined as reporting a history of both Acute LBP (ie, within the past 3 weeks) and Nonacute LBP (ie, within 3 months to 1 year). The mean reported level of LBP in the Chronic group was 5.3. An ANOVA on the No LBP, Acute, Nonacute, and Chronic groups showed a significant difference between mean LBP scores (/7 < .001). Table 4 also divides workers reporting a history of LBP into those who reported interference with Activities of Daily Living (ADL) (41%) versus those who reported no interference with ADL (59%). T tests performed on the mean LBP scores of workers reporting ADL interference versus no ADL interference revealed no difference between the two groups (Table 4). Workers who reported ADL interference, on average, did not report a higher level of LBP than workers reporting no ADL interference. There was a slight negative correlation between workers' reported level of LBP and the length of time in their current departments (r = -.12, p = .05). A t test of the mean LBP scores for smokers versus nonsmokers showed no significant difference between groups (p = .14). The nonsmokers had a slightly higher mean LBP score (n = 178, mean = 3.27) than the smokers (n = 75, mean = 2.76). An ANOVA for the variables of age, height, and weight versus LBP scores revealed no significant difference between groups (p values: age, p = .62; height, p = .52; weight, p = .13). Nonsignificant trends showed a higher mean LBP score with workers in the shortest height category and in the heaviest weight category. DISCUSSION
Prevalence of LBP The incidence of self-reported LBP (69.3%) was much higher than the incidence of LBP complaints reported to Occupational Health (27%), and much higher than the incidence of workers' compensation claims for LBP (2.3%). Although lifetime incidence rates for LBP of up to 70% are common in the literature, 1 year prevelances are typically less than 35%. 6-j5 It is not known whether the unusually high 1 year prevalence obtained here is specific to this particular plant or specific to this particular questionnaire. The workers were not questioned as to the Table 3: Mean LBP Score According to LBP History (n = 2851 LBP History No LBP LBP past LBP past LBP past LBP past
24hrs 3wks 3mos lyr
n
Mean LBP
84 52 98 146 201
1.02 5.17 4.94 4.49 4.06
Arch Phys Med Rehabil Vol 77, April 1996
LBP History by Category
Mean LBP for Category
Acute Nonacute Chronic
4.50 3.22 5.30
No ADL Interference 4.54 2.99 5.16
Interference With ADL 4.45 3.63 4.71
p .842 .999 .940
Mean LBP scores according to whether the reported LBP interfered with ADL are also listed (p values from t tests).
cause of their LBP, nor was it assumed that any reported pain was related to the work environment. Only a minority of workers can attribute their LBP onset to an obvious, single spinal injury. ~8-2~In the absence of significant trauma, most LBP, like other musculoskeletal disorders, is probably caused by the cumulative effects of factors such as poor posture and faulty body mechanics. For most full-time employees, about half of their waking adult lives will be spent at, or traveling to and from, their workplace. Therefore, regardless of where the "onset" of LBP symptoms is reported, workplace activities will likely have played a part in the development of workers' LBP symptoms. The questionnaire data suggests a wide prevalence of LBPr whereas workers' compensation statistics alone might suggest that there is no significant problem with LBP at this particular plant. It appears that the workers' compensation statistics reveal only the "tip of the iceberg." The questionnaire may have identified a larger potential LBP problem at this plant than would otherwise have been evident. The average level of LBP for the whole plant was greater than 3 of 10, and in some departments the average LBP level was greater than 5 of 10, "at the end of an average shift." This is much higher than anticipated by the investigators. This plant is a highly robotized operation, with the latest in mechanized assistive devices and very low employee turnover and absenteeism rates. 24The job descriptions do not involve strenuous lifting, bending, or twisting tasks that would explain such a high level of low back discomfort. The mean level of LBP increased according to how recently the worker reported an "episode" of LBP within the previous year. The group with the highest average level of LBP was the "chronic" group, those workers ,who reported both acute and nonacute episodes (table 4). Thi]s, both the time since previous episodes and the frequency of previous episodes seems to influence the workers' perception of or susceptibility to daily LBP in the workplace. There was no difference in the mean LBP scores of workers who did or did not report interference with ADL during their previous episodes. This suggests that the severity of previous episodes does not have an influence on the perception of daily LBP in the workplace or, rather, that interference with ADL may not be correlated with pain. Other factors may be more important.
Implications for Intervention Although most patients recover spontaneously from acute episodes of LBP, many will suffer a recurrence, and subsequent injuries are often more severe and long lasting. 12'~5-28Workers who develop "chronic LBP" (remaining off work for 6 months or longer), are responsible for 70% to 79% of sickness absence days and compensation c o s t s . 3'6'14'16'17 AS the duration of LBP disability increases, the chances for successful return to longterm reemployment become progressively smaller.28~29 Preventative programs will not eliminate LBP, but they can potentially reduce the magnitude of the LBP problem, particularly if they can reduce the rate of recurrence and chronieity.3° Attempting to prevent LBP after a worker has already complained to Occupational Health, however, is akin to trying to
BACK AND PERIPHERAL JOINT PAIN, Jefferson
prevent heart disease after a patient has already complained of angina. Ideally, strategies to prevent LBP, or at least, to prevent loss of work-time due to LBP, should intervene before the worker' s symptoms become severe enough that he or she seeks medical aid. The use of questionnaire data may have the advantage of identifying workers at risk for debilitating LBP while their LBP problem is in an early stage of progression, ie, a stage in which the symptoms are not sufficiently severe to interfere with normal function of daily activities. Likewise, questionnaire data may provide an indication of the effectiveness of intervention strategies, such as ergonomic changes or back education. Reducing the mean LBP level from 5 to 2, for example, may be evidence of effective primary prevention long before the long-term effects of the intervention on workers' compensation statistics is known.
Pain Patterns Pain drawings have been used for back pain patients to help distinguish patients with distinct anatomic patterns of pain from patients with nonanatomic patterns of pain. Widespread pain in a nonanatomic distribution may reflect the affective component of patients' pain and their psychological distress.3~ The inclusion of peripheral joint discomfort in the body diagram provided a "control" for the workers' LBP complaints. If a worker complains of a discomfort level of 5 for LBP, but a level of 1 or 2 in other body regions, then it is more likely that there is a distinct LBP problem than if the worker complained of a discomfort level of 5 everywhere, which may be due to a systemic problem such as rheumatic disease. The correlation matrix (table 1) shows that there is a statistically significant correlation between spinal pain and peripheral joint pain. The correlation values, however, are not very large, ranging from .12 to .46. The intercorrelations from the factor analysis (table 2) suggests little correlation between spinal and peripheral joint pain, except for a moderate influence of neck pain on the upper extremity factor. The factor analysis suggests that there are three clusters or "pain patterns": neck and back pain; foot and knee pain; and hand and arm pain. These make sense conceptually because of the anatomic and ergonomic linkage of these body regions. Bent forward posture will affect neck and back pain, standing on hard floors will affect foot and knee pain, and gripping and lifting movements will affect hand and arm pai n . Use Of the body diagram may also prove useful as an outcome measure for ergonomic intervention. Changes to a work site may reduce discomfort in one body region, but increase discomfort in another region. The body diagram provides quantification of the workers' subjective complaints that can help influence decisions on the effectiveness of the intervention strategies employed. Targeting Work Sites The difference in pain scores in individual departments suggests that different intervention strategies may be needed in different areas of the plant. It also helps in formulating ideas as to the causative factors, or at least in identifying where further investigation is needed to ascertain the appropriate intervention. This is illustrated by the departments displayed in figure 3. In Dept. 14, for example, the high level of spinal joint discomfort but low level of peripheral joint discomfort fits with the sedentary job description. Interventions should include changes to seating and monitor heights and frequent breaks from sitting. In Dept. 8, there does not appear to be any significant problems, on average. Interestingly, this department, Materials and
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Shipping, is where the greatest amount of materials handling takes place, with frequent lifting, carrying, and bending while packing and unpacking parts of various sizes. Contrasting this is Dept. 3, an area reporting a high average level of spinal and lower extremity discomfort. This area involves much less lifting and carrying but, conversely, much more static standing and sitting while operating machines. This suggests that intervention may need to include more variation of job description, with less static loading. The high level of LBP and foot pain in this and other departments is interesting. The question arises as to whether these scores are related via a common causative factor--eg, the hard concrete floors. On face value, the hard floor is the most obvious explanation for the high level of foot pain and i t may also explain the high incidence of LBP. An alternate explanation however, is that the high incidence of LBP is due to the workers maintaining a static bent-forward posture over their machines, irrespective of the floor surface. Interpreting the pain patterns has implications for planning intervention strategies. If hard flooring is the cause, then efforts should be made to cushion the floor and/or reduce the amount of time standing. If faulty posture is the cause, then efforts should be directed towards back care education and training, and possibly ergonomic changes (eg, bench height and reach or use of footrests). Use of a questionnaire, with inclusion of a body diagram, may help direct and assess the effectiveness of intervention strategies. There was no attempt in this study to correlate the level of spinal or peripheral joint pain with worker productivity. It is not known what level of pain interferes with a worker's performance sufficiently to cause a decrease in productivity. Presumably this will vary with the specific job demands for a given joint region and will vary among different joints and between different workers. Use of a pain questionnaire in conjunction with productivity data may help assess not only the effectiveness of intervention strategies in altering workers pain levels but also the cost-effectiveness of these strategies. In addition, use of the questionnaire may have served a constrnctive role in management-employee relations. By including all employees in the distribution of the questionnaire, it makes them aware of management's efforts to identify LBP and peripheral joint problems at an early stage. This suggests that management is willing to listen to employee input and not rely only on compensation statistics in efforts to improve the work environment. This questionnaire has been neither validated nor tested for reliability in this setting. A pilot questionnaire was distributed to a group of the same employees (n = 151) 6 months previous to the present questionnaire. It contained the same questions on LBP history, but a different pain diagram. In the pilot data 74% of respondents reported having had LBP within the past year, suggesting that the 69.3% obtained here was not an anomaly. Because of the anonymity of both the pilot questionnaire and the present study, however, formal tests of validity or reliability were not possible. The reproducibility of self-reported LBP incidence has been estimated by Biering-Sorenson. 32 At intervals of 6 months the question of ever having had LBP was answered yes or no consistently by 81% of subjects on the two occasions. Westrin 26 reported an 87% concordance between two interviewers regarding the lifetime incidence of LBP. Most of his subjects were interviewed twice on the same day. It is not known how the reliability of self-reported LBP varies according to acuteness of the symptoms. The reliability of self-reported LBP over a 1-year period may be higher than that of lifetime incidence. The testretest reliability of the pain drawing instrument on chronic pain
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patients has been estimated by Margolis and coworkers 33 at 88.2% for an average time interval of 71 days. The relJroducibility of pain drawings for acute joint pain is not known.
SUMMARY The questionnaire obtained useful information at very little cost. It identified a widespread prevalence of LBP, which was not evident from medical records. This may encourage the implementation of intervention strategies at an early stage in workers' LBP complaints, hopefully to better prevent long term LBP problems. Inclusion of the body pain diagram was particularly useful. Although plant-wide there does not appear to be a strong correlation between spinal and peripheral joint pain, in specific departments, and especially in individual workers, there were definite and specific pain patterns. The questionnaire thus can help target specific departments (or individuals) where different complaints suggest the need for different interventions. It also raised new questions as to the etiology of LBP complaints by revealing different pain patterns at different job descriptions. It appears that the questionnaire will also be a useful tool for obtaining outcome measures of intervention strategies, for both spinal and peripheral joint complaints. The high rate of return suggests a high level of acceptance and ease of completion by industrial workers.
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