Eduardo Myung1; José Domingos Neto1; Guilherme Augusto Murta1; Anielle Vieira1; Paulo Rogerio Gomes de Lima1; Leandro Lessa1; Wanderley Marques Bernardo2
BACKGROUND: Low back pain is a considerable global public health problem. Use of back belts in occupational settings arises from the expectation of countless biomechanical benefits, which together would contribute to the prevention of this problem.
OBJECTIVE: To orient students, physicians and health institutions on the use of back belts, lumbar support or braces for prevention of low back pain or injury among asymptomatic workers.
METHOD: The present guideline was developed based on a systematic literature review; 809 studies were located in database MEDLINE and 571 in EMBASE and Cochrane CENTRAL. Evaluating back-belt use as preventive intervention against low back pain demands quantifying benefits, harms and difficulties to implementation, as well as the methodological quality of primary studies.
CONCLUSION: Despite the weak benefits reflected in the individual, partial and isolated results of a few studies, there is no consistent evidence for the use of back belts, lumbar supports or braces for primary prevention of low back pain or occupational low back injury among workers. According to the available evidence, back-belt use is not associated with reduction of absenteeism.
Keywords: orthotic devices; primary prevention; low back pain.
INTRODUÇÃO: Lombalgia é um problema internacional importante de saúde pública. O uso de cinta lombar no meio ocupacional emerge da expectativa de inúmeros benefícios biomecânicos que, em conjunto, promoveriam a prevenção desse problema.
OBJETIVO: Orientar estudantes, médicos e estabelecimentos de saúde sobre o uso de cinta lombar, suporte ou órtese lombar como prevenção da lombalgia ou de lesões lombares em trabalhadores sem sintomatologia atual.
MÉTODO: Ela foi desenvolvida a partir da revisão sistemática da literatura: da base de dados MEDLINE, foram recuperados 809 trabalhos e das bases EMBASE e Central Cochrane, 571. Avaliar a cinta lombar como intervenção preventiva de lombalgia envolve a quantificação de benefícios, malefícios e facilidade de sua implementação, assim como a qualidade metodológica dos estudos primários.
CONCLUSÃO: Apesar do benefício demonstrado fracamente em resultados individuais, parciais e isolados em poucos estudos, não há evidência consistente que sustente a utilização de cinta lombar, suporte ou órtese lombar na prevenção primária da lombalgia ou de lesões lombares ocupacionais em trabalhadores. As evidências, agrupadas, apontam para ausência de redução de absenteísmo com o uso da cinta lombar.
Palavras-chave: aparelhos ortopédicos; prevenção primária; dor lombar.
To establish the efficacy of back-belt use as method for primary prevention of occupational low back pain.
DEGREES OF RECOMMENDATION AND STRENGTH OF EVIDENCE
A: experimental or observational studies with better consistency;
B: experimental or observational studies with less consistency;
C: case reports/uncontrolled studies;
D: opinions without critical assessment, based on consensus, physiological studies or animal models
Low back pain is a considerable global public health problem. A systematic review published in 2015 by Brazilian authors compiled national and international studies on the prevalence of chronic low back pain. The global prevalence of chronic low back pain is estimated as 4.2% among individuals aged 24 to 39 years old, and 19.6% among the ones 20 to 59 years of age. Among Brazilian older adults, the estimated prevalence is 25.4%1. According to another systematic review published in 2017, low back pain is a significant complaint in emergency departments, corresponding to 4.39% of the patients seen2.
Other systematic reviews analyzed the prevalence of low back pain or spine disorders among specific populations of workers. Degenerative lumbar spine disease affects 19% (544 out of 2,449) surgeons or interventionists3, has an annual prevalence of 17 to 94% among athletes4, and was found among 51.1% of civil construction workers5. According to the 2016 Social Security Statistical Yearbook, dorsalgia (ICD M54) represented 6.15% of occupational diseases, ranking third in prevalence6.
Several individual risk factors were associated with low back pain in systematic reviews, which reinforces the preventive role of occupational medicine in the control of individual risk factors related to low back pain, such as obesity7,8, smoking9 and depression10.
In regard to occupational risk factors, a systematic review of prospective studies published in 2014 found a statistically significant relationship between low back pain and biomechanical factors: odds ratio (OR) 1.11 (95% confidence interval–CI 1.05–1.18) per 10 kg lifted and OR 1.09 (95%CI 1.03–1.15) per 10 lifts/day. The authors estimated that lifting loads over 25 kg and lifting at a frequency of 25 lifts/day increases the annual prevalence of low back pain by 4.32 and 3.50%, respectively11.
The use of back belts in occupational settings derives from the expectation of countless biomechanical benefits which together might prevent the occurrence low back pain: redistribution of spinal forces during lifting as a result of increased intrabdominal pressure, decreased muscle fatigue and biomechanical strain as a result of increased muscle support, decreased range of motion, improved posture, and a sense of safety12.
Assessment of back belts as preventive intervention against low back pain requires quantifying benefits, harms and difficulties to implementation, as well as analysis of the methodological quality of primary studies. For the present guideline, we selected a systematic review13, five clinical trials14-18, and five observational studies19-24.
Studies on low back pain should face the methodological challenge posed by the need for a consistent selection of study populations, which not seldom exhibit heterogenous health profiles, comorbidities, etiology, frequency, pain severity and job activities. These factors hinder the assessment of the purely preventive value of back belts, as well as the generalization of results. This heterogeneity reinforces the relevance of the quality of randomization in clinical trials in a way to homogenize such factors. The level of the evidence resulting from cohort studies tends to be lower compared to randomized clinical trials precisely due to the lack of random allocation.
None of the analyzed clinical trials exclusively included participants without history of low back pain, and thus all of them investigated combinations of primary and secondary low back pain prevention13 (A). Five studies reported to have included workers with history of low back pain13-17 (A), while two did not provide information on the history or current state of low back pain13,18 (A). All the cohort studies included participants with history of low back pain. This factor is a consistent predictor of relapse25 (A) which might thus potentially influence the prevalence of low back pain found in studies.
In regard to the job activities considered in the clinical trials, two studies recruited populations of home care attendants14,15 (A), one warehouse workers18 (A), and two airline baggage handlers16,17 (A). The cohort studies included supermarket employees19 (B), employees in the retail-trade home improvement industry20 (B), forklift workers21 (B), hospital employees22 (B), and a military population23 (B).
The methodological quality of most of the selected clinical trials was limited13 (A). In the studies by Walsh and Schwartz18 (A), Roelofs et al.14 (A) and van Poppel et al.16 (A) the random sequence generation was adequate. Only in the studies by Roelofs et al.14 (A) and van Poppel et al.16 (A) allocation was adequately concealed. The study by Kraus et al.15 (A) did not randomize individuals, but nine home care agencies to the control and intervention groups. In none of the studies the participants or outcome examiners could be blinded to intervention, which is relevant for ruling out placebo effect13 (A).
As to the benefits measured in the analyzed studies, Chart 1 summarizes the results of the clinical trials and Chart 2 the ones of the observational studies (Appendix 1).
Absenteeism is a relevant outcome, because it is an indirect indicator of severe low back pain and reflects changes in the natural history of disability. None of the clinical trials investigated statistically significant or considerable reduction of absenteeism. Low adherence to back-belt use reduced the statistical power of the studies conducted by Reddell et al.17 (A) and van Poppel et al.16 (A). Walsh and Schwartz18 (A) found significant reduction of absenteeism of just 2.6 days. Among the selected cohort studies, only the one by Mitchell et al.23 (B) analyzed absenteeism as outcome of interest, which was nonsignificant among the participants without history of low back pain.
In regard to the incidence of low back pain, Kraus et al.15 (A) and Roelofs et al.14 (A) analyzed statistically significant reduction of pain, the results being favorable to the group that used back belts. In the study by Kraus et al.15 (A), the benefit was only marginally significant, rate ratio (RR) 1.36 (95%CI 1.02–1.82), which reduced the odds of clinical relevance of the measured benefit. In the study by Roelofs et al.14 (A) discrete reduction of incidence with the use of back belts, of -52.7 (95%CI -59.6–-45.1) days per year, was attended by discrete reduction of the intensity of pain and improvement of functioning. However, these benefits did not result in significant decrease of absenteeism.
Among the cohort studies, only the one by Wassel et al.19 (B) was prospective and had a reasonable sample size. These authors did not measure benefits after six-month follow-up of black-belt users versus non-users in a population of workers. The study by de Kraus et al.20 (B) found difference in the occurrence of occupational low back injury between back-support users and non-users of 10.4 per million working hours, RR=1.52 (95%CI 1.36–1.69). These authors did not analyze degree of adherence, absenteeism, severity of pain or concomitant influence of other interventions.
As to harms, the analyzed studies only considered isolated reports of physical or thermal discomfort. Using back belts was not associated with impaired muscle strength13, (A)24 (B).
Adherence to back-belt use was heterogeneous among the clinical trials, varying from 43 to 92%. However, the methods to assess adherence are not independent from the participants' memory and subjectivity when questionnaires are administered. Only the study by Roelofs et al.14 (A) consistently measured adherence to back-belt use by means of individual diaries; yet, back belts were used just 5.5 days per month, on average.
The scientific evidence gathered consistently points to lack of benefit in terms of reduction of absenteeism with the use of back belts. Preventive benefits relative to the prevalence and severity of low back pain were not consistent among the analyzed studies, having isolated and marginally significant results in some studies.
It is worth calling the attention to the difficult application of the notion of primary prevention vis-à-vis the available evidence, given the high frequency of inclusion of populations with and without history of low back pain in the analyzed studies.
Our conclusions agree with the ones of other systematic reviews on the subject of interest13,26, as well as with the institutional scientific position of National Institute for Occupational Safety and Health (NIOSH)27 (D) and Canadian Centre for Occupational Health and Safety (CCOHS)28 (D).
Despite the weak benefits reflected in the individual, partial and isolated results of a few studies, there is no consistent evidence grounding the use of back belts, lumbar support or braces for primary prevention of low back pain or occupational low back injury among workers. The available evidence indicate lack of reduction of absenteeism in association with the use of back belts.
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2. Edwards J, Hayden J, Asbridge M, Gregoire B, Magee K. Prevalence of low back pain in emergency settings: a systematic review and meta-analysis. BMC Musculoskelet Disord. 2017;18(1):143. https://dx.doi.org/10.1186%2Fs12891-017-1511-7
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4. Farahbakhsh F, Rostami M, Noormohammadpour P, Zade AM, Hasanmirzaei B, Jouibari MF, et al. Prevalence of low back pain among athletes: A systematic review. J Back Musculoskelet Rehabil. 2018;31(5):901-16. https://doi.org/10.3233/BMR-170941
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7. Walsh TP, Arnold JB, Evans AM, Yaxley A, Damarell RA, Shanahan EM. The association between body fat and musculoskeletal pain: a systematic review and meta-analysis. BMC Musculoskelet Disord. 2018;19(1):233. https://doi.org/10.1186/s12891-018-2137-0
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11. Coenen P, Gouttebarge V, Van Der Burght AS, van Dieën JH, Frings- Dresen MH, van der Beek AJ, et al. The effect of lifting during work on low back pain: a health impact assessment based on a meta-analysis. Occup Environ Med. 2014;71(12):871-7. https://doi.org/10.1136/oemed-2014-102346
12. Minor SD. Use of back belts in occupational settings. Phys Ther. 1996;76(4):403-8.
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14. Roelofs PD, Bierma-Zeinstra SM, van Poppel MN, Jellema P, Willemsen SP, van Tulder MW, et al. Lumbar supports to prevent recurrent low back pain among home care workers: a randomized trial. Ann Intern Med. 2007;147(10):685-92.
15. Kraus JF, Schaffer KB, Rice T, Maroosis J, Harper J. A field trial of back belts to reduce the incidence of acute low back injuries in New York City home attendants. Int J Occup Environ Health. 2002;8(2):97-104. https://doi.org/10.1179/107735202800339073
16. van Poppel MN, Koes BW, van der Ploeg T, Smid T, Bouter LM. Lumbar supports and education for the prevention of low back pain in industry: a randomized controlled trial. JAMA. 1998;279(22):1789-94.
17. Reddell CR, Congleton JJ, Dale Huchingson R, Montgomery JF. An evaluation of a weightlifting belt and back injury prevention training class for airline baggage handlers. Appl Ergon. 1992;23(5):319-29.
18. Walsh NE, Schwartz RK. The influence of prophylactic orthoses on abdominal strength and low back injury in the workplace. Am J Phys Med Rehabil. 1990;69(5):245-50.
19. Wassell JT, Gardner LI, Landsittel DP, Johnston JJ, Johnston JM. A prospective study of back belts for prevention of back pain and injury. JAMA. 2000;284(21):2727-32.
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24. Kurustien N, Mekhora K, Jalayondeja W, Nanthavanij S. Trunk Muscle Performance and Work-Related Musculoskeletal Disorders among Manual Lifting with Back Belt Wearing Workers. J Med Assoc Thai. 2015;98(Suppl. 5):S74-80.
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APPENDIX 1 – METHODS
1. Clinical question
Does using back belts, lumbar support or braces (primarily) prevent the occurrence of low back pain or injury among workers currently without any symptom?
2. Eligibility criteria
PICO components (P — population or problem, I — intervention, C — control, and O — outcome);
Randomized clinical trials; observational cohort studies; systematic review with or without meta-analysis (the latest);
Without language or time restrictions;
Full-text available or abstract describing the necessary data.
Population outside occupational environments or settings;
Studies on the treatment of low back pain or injury.
3. Article search
The search began on 20 April 2017 for relevant articles, based on their title and abstract. The selected articles were subjected to full-text analysis for relevance vis-à-vis the research question. The articles retrieved from all the searched databases were reunited, and two investigators analyzed their methodological quality. Articles with poor methodological quality could be excluded in this stage. Figure 1 depicts the absolute number of articles retrieved from each database, the ones selected for review, and the included and excluded ones.
#1 (Occupational diseases OR workplace OR worksite OR worker OR workers OR work or working);
#2 (Low back pain OR lumbago OR low back injury OR lumbar injury);
#3 (Protective devices OR belts OR belt OR support OR devices);
#4 (prevention and control) OR (prevention & control*).
(Occupational diseases OR workplace OR worksite OR worker OR workers OR work or working) AND (low back pain OR lumbago OR low back injury OR lumbar injury) AND (protective devices OR belts OR belt OR support OR devices) AND ((prevention and control) OR (prevention & control*).
4. Critical assessment
The research question was framed according to the PICO process. Based on this format and Descritores em Ciências da Saúde (DeCS — Health Science Descriptors) and synonyms we defined the search strategy for each database. Levels of evidence were established per study type according to the Oxford classification29.
5. Methods for data extraction and analysis of results
From the evidence included we extracted the data needed to ground, in a document, recommendations answering the clinical question as a function of the characteristics of patients and interventions, comparisons and the outcomes established in the eligibility criteria.
The search for scientific information allowed retrieving 809 studies from database MEDLINE and 571 from EMBASE and Cochrane CENTRAL. Following application of the eligibility criteria and removal of duplicates, 67 articles were selected based on their titles and abstracts for full-text analysis. Further 55 articles were excluded for the following reasons: did not comply with the PICO frame (6); exercise/ ergonomics (17); exercise/education (10); narrative reviews (7); guidelines (2); case series/editorials (2); not focused on prevention (4); non-occupational (1); outdated systematic reviews (4); other (3). Therefore, 11 studies were selected (5 randomized clinical trials, 1 systematic review and 5 observational cohort studies) to ground the present guideline (Figure 1).
7. Evidence application — recommendation
The recommendations were made by the authors of the present technical guideline, considering the characteristics of the synthesized evidence. The recommendations were subjected for validation to all the members of our working group. The degree of recommendation directly derives from the strength of evidence the included studies as per the Oxford classification29 and the GRADE system30.
8. Conflict of interests
The authors declare there is no conflict of interests in regard to the present review.
11 de Julho de 2018.
Aceito em 11 de Novembro de 2018.
Fonte de financiamento: nenhuma