Methodologic issues in low back pain research in primary care

STUDY DESIGN: Narrative review and discussion of the selected literature. OBJECTIVES: To discuss some important methodologic challenges in low back pain research in primary care. SUMMARY OF BACKGROUND DATA: Many methodologic problems must be confronted when conducting low back pain research. Some of these problems are back pain specific or specific to the primary care setting. METHODS: Methodologic problems related to four research issues will be discussed: study designs, definition of low back pain, determinants of low back pain, and outcome assessment. RESULTS: Two fundamentally different study designs are frequently used in low back pain research, namely observational studies and experimental studies. The definition of low back pain is typically restricted to a highly variables self-reported symptom, the sensation of pain in the back. There clearly is a need for an evidence-based classification system for low back pain. Because a tenable theoretical framework is lacking, it is difficult to know which determinants of low back pain should be quantified. Low back pain studies focus usually on health-related quality-of-life outcome parameters. The identification of the minimum clinically relevant changes for the most important outcome instruments needs further consideration. CONCLUSIONS: In years to come, low back pain researchers are challenged to overcome some of these (and other) problems to enhance the quality of low back pain research in primary care.     

Neuromuscular activity and electromyography in painful backs: Psychological and biomechanical models in assessment and treatment.

Reviews the literature related to myogenic back pain and EMG assessment and treatment. There is evidence to support a number of patterns of muscular involvement in back pain. It has been proposed that back pain may result from a pain-spasm-pain cycle related to both splinting or protective posturing associated with physical damage and psychological and environmental stress. In addition, it has been proposed that back pain may be due to a biomechanical process secondary to aberrant patterns of neuromuscular activity. There is electrophysiological evidence that suggests that some cases of back pain are related to elevated paraspinal EMG levels and some are associated with faulty muscular/biomechanical process. Thus, there appears to be a variety of myogenic etiologies to back pain, just as there are numerous structural and neurological etiologies. The anatomy and neuromuscular physiology of the back, EMG assessment data, and EMG biofeedback treatment data are reviewed. It is suggested that an assessment of general autonomic arousal in back pain patients may be beneficial in (1) identifying patients who could benefit from more general stress-management programs and (2) providing a database for this etiological position. (82 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Relationship between muscle fiber composition and functional capacity of back muscles in healthy subjects and patients with back pain

Back muscles are important to the stability of the lumbar spine. Muscle fiber composition may give some indication of the functional capacity of these muscles. This review explores the relationship between muscle fiber composition and functional capacity of back muscles. The reference values for the type and size of the muscle fibers found in the back musculature of healthy subjects and patients with back pain are also presented. A high percentage of type I fibers, which are larger in size than type II fibers, has been found in back muscles at the thoracic and lumbar levels. This is in accordance with the postural function of these muscles. The diameter of type II fibers is smaller in females than males, which may partly explain the lesser strength and greater endurance capacity of back muscles in females. Due to the limited amount of pertinent data, no conclusive evidence is available regarding age-related changes in muscle fiber composition in the musculature of the back. In patients with lumbar disorders, pathological changes and selective atrophy of type II fibers are seen, and these can be changed with adequate exercises. Further research is suggested to address issues related to gender, age, back pain, and exercise and their effects on the apparent back muscle fiber composition.     

Successful hormonal treatment of pulmonary parenchymal endometriosis

OBJECTIVE: Tobacco use and other behavioral factors are associated with chronic back pain. Anecdotes suggest excess caffeine use may also be associated with chronic back pain. We compared caffeine consumption by chronic back pain patients with caffeine consumption by controls. DESIGN: Retrospective case-control study. SETTING: A multispecialty outpatient facility. PATIENTS: Sixty new, consecutive patients with chronic back pain compared to 60 new, consecutive patients without chronic back pain. INTERVENTION: Patients were prospectively asked to complete an intake questionnaire. MAIN OUTCOME MEASURE: Daily caffeine consumption was estimated by analyzing the intake questionnaire. Differences between groups were analyzed by both normal and nonparametric statistics. RESULTS: Consumption of caffeine by patients with chronic back pain averaged 392.4 mg/day. Controls consumed 149.8 mg/ day, a significant difference (p = .0001). Men consumed 86% more caffeine per day than women (p = .02). Age and caffeine consumption showed little correlation (r = .126). CONCLUSIONS: Patients with chronic back pain consume over twice as much caffeine as patients without chronic back pain. Confounding variables and possible mechanisms associating caffeine with chronic back pain are discussed.     

How to recognize and treat specific low back pain?

A wide variety of mechanical and non-mechanical disorders are associated with the clinical symptom of low back pain. Mechanical disorders are the cause of the vast majority of low back pain. Despite this frequency, the specific cause of mechanical low back pain can not be elucidated in spite of extensive diagnostic evaluation in a majority of individuals. Specific causes of low back pain are associated with less frequently occurring systemic illnesses including rheumatic, infectious, neoplastic, gynaecological and vascular disorders. The diagnostic process is more successful in identifying systemic disorders as the specific cause of low back pain. Non-surgical management is effective therapy with most patients with mechanical disorders of any form. Systemic illnesses require interventions directed specifically at healing the affected organ system.     

Chronic low back pain

Most episodes of low back pain are mechanical in origin and resolve within a 12-week period. These acute episodes of back pain are associated with muscle strain and intervertebral disc herniation with radiculopathy. A smaller proportion of individuals have back pain with a duration greater than 12 weeks. These patients have back pain secondary to a wide variety of mechanical and nonmechanical disorders. The mechanical disorders associated with chronic low back pain include osteoarthritis and lumbar spinal stenosis; the nonmechanical disorders include infectious, neoplastic, rheumatologic, endocrinologic, vascular, and gynecologic. The clinical symptoms associated with each variety of disorder helps guide the appropriate diagnostic evaluation. Plain roentgenograms are useful in documenting the presence of spinal stenosis, benign or malignant tumors, osteoporosis, sacroiliitis, and spondylitis. CT scan is helpful in defining the bony alterations associated with malignant tumors and the vascular abnormalities associated with aneurysms. MR imaging is the technique of choice to document the extent of malignant processes and the presence of endometriosis in the pelvis. The therapy of these entities are specific for the disease entity causing the chronic low back pain. Although most of the disorders that cause chronic low back pain cannot be cured, therapy can decrease pain and improve function of the symptomatic patient.     

Oh, my aching back: evaluation and surgical treatment of lumbar spine disorders

Low back pain is a common cause of disability and reason for seeking medical care. Surgery rates for low back pain are escalating, and the overall costs exceed $1 billion. Primary care physicians are increasingly responsible for the initial evaluations and management of these individuals. Recognition of surgical indications by these physicians will decrease costs by initiating management and will limit morbidity by expediting appropriate referrals. The important aspects of the evaluation of low back pain are reviewed in this article. Surgical indications in low back pain including infection, tumor, degenerative conditions, and nonacute traumatic sequelae are discussed.     

Low back pain and its relationship to back strength and physical activity in children

OBJECTIVE: The objective of the study was to determine the occurrence of low back pain and its relationship to back strength and physical activity in children. METHODS AND MATERIALS: The study included 53 boys and 43 girls aged 10 to 19 years from a group of 116 children who had undergone isometric strength testing 4 years previously. No intervention was performed. Each child was asked five questions concerning low back pain. A questionnaire to quantify participation in athletic activities and manual labor was used as the basis for calculation of each child's activity level. Isometric back flexor and extensor strength were measured with the same method used 4 years previously. Statistical analyses were performed with appropriate correction for confounding factors. RESULTS: The frequency of low back pain and the relationship between low back pain and age, between low back pain and back strength, and between low back pain and physical activity were determined. There was a history of low back pain in 51%, and the frequency of low back pain in the past year was 35%. Eight percent of the children had been limited by low back pain, and 7% had seen a doctor for the pain. The first incident of low back pain occurred at a mean age of 12.3 years. The frequencies of a history of low back pain and of low back pain in the past year increased significantly with age (p = 0.02 and 0.01 respectively). Increased physical activity was significantly associated with a history of low back pain (p = 0.03), and increased back flexor strength was significantly associated with a history of low back pain and of low back pain in the past year (p = 0.03 and 0.008, respectively). The rate of low back flexor or strength over 4 years had a significantly positive association with the occurrence of low back pain in the past year (p = 0.008). CONCLUSIONS AND RELEVANCE: Low back pain is common in children, and, in contrast to adults, low back pain in these children was more common with increased physical activity and stronger back flexors. We believe the main causes of low back pain in children are musculotendinous strains and ligamentous sprains.     

Changes in canine saliva ion concentration induced by increased intraluminal pressure

Hydrostatic pressure was applied to a cannula inserted into Wharton's duct of adult dogs anesthetized with pentobarbital and the effect of pressure on saliva flow rate and ionic composition of saliva was measured. Increasing the back pressure on a secreting gland resulted in a decrease in flow rate. Over the range of 0-100 mmHg back pressure the decrease in flow was proportional to the applied back pressure. The potassium concentration of saliva collected in the absence of back pressure and at raised pressure was similar even though back pressure reduced flow. In contrast, sodium concentration decreased when back pressure caused salivary flow rate to be reduced. However, when examined at the same flow rates the concentration of sodium is increased when back pressure is applied to the gland as compared to absence of back pressure. Under conditions of constant stimulation the total output of sodium and potassium into saliva decreases as back pressure is increased; but when equal flow rates are compared total sodium output increases in the presence of applied back pressure, whereas potassium output remains constant.     

Pharmacologic therapies

Medical treatment of low back pain is at best palliative. While no drugs are specifically labeled for back pain treatment, analgesics, muscle relaxants, and corticosteroids are used in practice to augment rest and exercise programs. Invasive therapy remains contentious. This article reviews the available literature on the various pharmacologic therapies. In addition, newly postulated outcome measures for future back pain studies are discussed.     

Community studies of the health service implications of low back pain

STUDY DESIGN: Retrospective study using primary care physician case notes and a self-report questionnaire on the same randomly selected population sample. OBJECTIVES: To assess the prevalence, management, and outcomes of low back pain in the community, comparing, in the same random sample of registered patients, self-report questionnaire data and primary care physicians' records. SUMMARY OF BACKGROUND DATA: The financial and resource implications of low back pain are extensive. Data on consultations, investigations, and the management of low back pain are fragmentary and there are no comparisons estimating prevalence from case notes and self-report. METHODS: A retrospective study of prevalence, management, referral, and outcome covering the previous 12 months was carried out in three general practices using case notes and a self-report postal questionnaire on a sample of 900 patients over 18 years. RESULTS: Lifetime prevalence of low back pain was 62%. Annual prevalence was 48%, with 16% reporting low back pain at the time of report. Twenty-four percent consulted their primary care physician for low back pain, of whom 17% were referred to a hospital specialist. The annual consultation rate of patients with low back pain was similar to the rate for patients with chronic conditions. The activities of daily living were restricted in less than half, with few taking sick leave. The general health status of those reporting recent low back pain was significantly lower than those not reporting low back pain. Most felt that low back pain was self-limiting and would not consult health professionals for future episodes. There were substantial discrepancies between case notes recorded at consultation with the primary care physician and self-report regarding consultation and investigations. CONCLUSIONS: Prevalence rates were comparable with those reported in other studies. The significant discrepancies between data sources suggest patient recall bias or underrecording in case notes. The low consultation rate, time off, and day-to-day disability indicate that most episodes are self-limiting.     

Sclera fixation of posterior chamber lenses in vitrectomized eyes. Perfluorocarbon as an operative aid

OBJECTIVE: To discuss a case of chondromyxoid fibroma presenting with low back pain. CLINICAL FEATURES: A 50-yr-old man had an 8-yr history of low back pain. This was diagnosed and treated as arising from the disc and caused by spinal stenosis. Magnetic resonance imaging findings supported the clinical findings. Years later, a plain radiograph of the pelvis revealed an incidental abnormality of the right ilium, and the patient was subsequently referred to a musculoskeletal tumor center for treatment. INTERVENTION AND OUTCOME: The lesion was surgically removed and the defect was reconstructed via bone allograft. CONCLUSION: Such tumors are a rare cause of back pain. Tumors of the pelvis can at times present as back pain. In cases of refractory back pain, an X-ray of the pelvis can be a useful screening investigation. Chondromyxoid fibromas are rare tumors best treated by excision if they are amenable or by curettage and bone grafting procedures.     

Chronicity of back problems during working life

STUDY DESIGN: A follow-up study of a cohort of 444 patients aged 16 to 59 years who consulted with their general practitioners (GPs) in 1987-1988 for an incident episode of back pain. OBJECTIVES: To determine the proportion of patients with back pain in whom chronic back problems develop after a follow-up of 7 years, to compare health outcomes and labor force participation of patients with and without chronic back problems and to identify determinants of chronicity. SUMMARY OF BACKGROUND DATA: The incidence and prevalence of back pain are very high. A large proportion of the costs related to medical consumption, absence from work, and disability are probably caused by chronic back problems. It is unknown what proportion of back problems become chronic, especially after a long follow-up period, and which factors can predict chronicity. METHODS: Data on the course of the symptoms and medical consumption from the period between 1987-1988 and 1991 were gathered retrospectively. Data on several health outcomes, including LFP, and data on some work characteristics were collected prospectively in 1991. A more extensive data set on health outcomes including psychologic status and working situation was collected in 1994. RESULTS: Chronic back problems developed in 28% of the patients. These patients reported more pain, higher levels of medical resource consumption, worse health outcomes, and lower labor force participation. Episodes of back pain before 1987-1988, severe pain in 1991, and disability score in 1991 were positively associated with chronicity in 1994, difficulties with job performance in 1991, and frequent stooping in the subgroup of patients who held a paying job in the follow-up period. CONCLUSIONS: Even after a follow-up of 7 years, the proportion of people with chronic back problems was high. The consequences for quality of life, labor force participation, and consumption of medical resources are clear. Further research is necessary to examine determinants and ways to prevent chronicity.     

The course of back pain in primary care

STUDY DESIGN: Review paper of outcome studies among primary care back pain patients. OBJECTIVES: To determine the short-term and long-term pain and functional outcomes of patients with back pain who are seeking treatment in primary care settings. SUMMARY OF BACKGROUND DATA: Back pain has been viewed as running either an acute or a chronic course, but most patients experience recurrent back pain. This review summarizes outcome studies in light of the episodic course of back pain. METHODS: Studies reporting pain and functional outcome data for consecutive primary care patients with back pain were reviewed. RESULTS: Back pain among primary care patients typically is a recurrent condition for which definitions of acute and chronic pain based on a single episode are inadequate. Because a majority of patients experience recurrences, describing only the outcome of the initial back pain episode may convey a more favorable picture of long-term outcome than warranted. For the short-term follow-up evaluation, most patients improve considerably during the first 4 weeks after seeking treatment. Sixty-six percent to 75% continue to experience at least mild back pain 1 month after seeking care. At 1 month, approximately 33% report continuing pain of at least moderate intensity, whereas 20-25% report substantial activity limitations. For the long-term follow-up (1 year or more) period, approximately 33% report intermittent or persistent pain of at least moderate intensity, one in seven continue to report back pain of severe intensity, and one in five report substantial activity limitations. CONCLUSION: Results from existing studies suggest that back pain among primary care patients typically runs a recurrent course characterized by variation and change, rather than an acute, self-limiting course.     

Evaluating back pain in older patients

Low back pain in the elderly has a much wider range of possible causes than in younger patients. In addition to nonspecific mechanical causes, malignancy presenting as back pain occurs more often in older patients. Other systemic and visceral causes of back pain such as polymyalgia rheumatica, aortic aneurysm, Paget disease, Parkinson disease, and osteoporosis with compression fracture occur almost exclusively in persons over age 50. Keys to diagnosis and management of low back pain in older patients are presented.     

Back injury prevention interventions in the workplace: an integrative review

The purpose of this integrative review is to describe the state of knowledge about the effect of worksite back injury prevention programs on selected study outcomes. Fifteen experimental and quasi-experimental studies published between 1987 and 1994 were identified through a comprehensive literature search. The research studies were reviewed and analyzed using a data collection abstracting tool. Four types of back injury prevention intervention programs were identified: back belts, back schools, exercise/flexibility training, and educational classes. Positive program outcomes were reported for all four program types; however, the back school and the exercise/flexibility training programs were studied more frequently and demonstrated a greater proportion of positive results than the other two program types. Conclusions should be viewed cautiously due to the small number of studies reviewed and their methodological limitations. Implications for occupational health nursing practice and future research related to worksite back injury prevention are offered.     

Determinants of isokinetic and psychophysical lifting strength and static back muscle endurance: a study of male monozygotic twins

STUDY DESIGN: Retrospective cohort. OBJECTIVES: To determine the relative contributions of anthropometric factors, physical activity, back and neck pain, overall health, and familial aggregation (the combined effects of genetics and childhood environment) to different measurements of adult back muscle function. SUMMARY OF BACKGROUND DATA: Many methods of muscle testing are employed in the attempt to predict, prevent, treat, and rehabilitate low back pain. Poor correlations between the test results suggest that they are measuring different attributes and have different determinants. METHODS: Muscle function tests, magnetic resonance images, and a detailed interview were obtained in 65 pairs of monozygotic male twins. RESULTS: Familial aggregation was the strongest determinant of isokinetic and psychophysical lifting and static back endurance, explaining 56%, 32%, and 15% of the variances, respectively, beyond that which age alone predicted. Back pain and physical loading in work and leisure explained 2%, 0%, and 23% of the variances. CONCLUSIONS: The combined effects of genetics and childhood environment play a dominant role in determining adult back muscle function. Physical loading at work and leisure, back and neck pain history, overall health, and anthropometric factors had a comparatively minor role, suggesting that the potential of interventions to increase and sustain back muscle function in healthy adults, measured through these tests, may be limited. The relative contributions of constitutional, behavioral, and environmental factors differ substantially in the three tests, and provide insights into what these commonly used tests actually reflect or measure. This knowledge can be used to guide more appropriate selection and interpretation of results of back muscle function tests.     

Assessment of spinal musculature using surface electromyographic spectral color mapping

STUDY DESIGN: A technique is described for analyzing electromyogram data from lumbar spinal muscles, with special reference to discrimination of people with back pain. The ability to discriminate was evaluated in 99 people (61 healthy and 38 with chronic or acute back pain), and the influence of load was assessed. OBJECTIVES: To evaluate methods of analysis of complex electromyogram data and to assess correlation of electromyogram information with clinical condition in people with and without back pain. SUMMARY OF BACKGROUND INFORMATION: In previous analyses of electromyogram data, only a small part of the data have been used. Spinal muscular decompensation has been postulated in chronic low back pain, but there has been no direct demonstration of this phenomenon. Objective measures are still elusive. METHODS: Lumbar spinal surface electromyograms were recorded during an isometric lifting task. The data were represented graphically as color-coded plots of electromyogram frequency, time, and electromyogram amplitude. Spectral width at half-peak amplitude (spectral half width) was calculated from the digitized, summed data. Ninety-nine people were tested: 48 men (29 with no recent [in the past 2 years] history of back pain, 16 with chronic back pain, 3 with acute back pain) and 51 women (32 with no recent back pain and 19 with chronic back pain). RESULTS: Spectral color maps in people with chronic back pain were markedly different from those in healthy people. Spectral half width was greater in people with chronic back pain than in healthy people (P < 0.01). Blinded analysis of spectral color maps allowed discrimination of people with back pain from healthy people with a sensitivity of 76% and a specificity of 81%. People with a history of back pain had markedly variable half widths. CONCLUSIONS: A new method of analysis of electromyogram data from lumbar spinal muscles has allowed discrimination between people with back pain and healthy people. This provides direct evidence of a correlation between muscular electrical function, measured by electromyogram, and low back pain. This technique may have potential as an objective measurement tool.     

穿孔机前后台设备选型分析及工程应用

穿孔机前后台是穿孔机组中非常重要的辅助设备。简述了国内外穿孔机前后台的技术特点,并进行了设备选型分析。着重分析了包钢Φ159mm连轧管生产线穿孔机前后台的技术性能、设备结构及设计特点,该生产线穿孔机前台由液压推坯机和受料导槽组成,穿孔机后台采用顶头顶杆大循环系统,完全能够满足穿孔机组高节奏、高产能,穿孔毛管质量高的要求。     

天津钢管公司炼钢厂1#除尘反吸系统改造及袋式除尘分析

介绍了袋式除尘原理，针对公司炼钢厂除尘系统反吸风机经常发生故障停机，影响生产的问题，论述了取消反吸风机的理论依据和措施。