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Biomedical subjects

G B Andersson

Publications and source records attributed to G B Andersson.

At least 19 recordsLinked to original sources
PubMed1999

Epidemiological features of chronic low-back pain.

Although the literature is filled with information about the prevalence and incidence of back pain in general, there is less information about chronic back pain, partly because of a lack of agreement about definition. Chronic back pain is sometimes defined as back pain that lasts for longer than 7-12 weeks. Others define it as pain that lasts beyond the expected period of healing, and acknowledge that chronic pain may not have well-defined underlying pathological causes. Others classify frequently recurring back pain as chronic pain since it intermittently affects an individual over a long period. Most national insurance and industrial sources of data include only those individuals in whom symptoms result in loss of days at work or other disability. Thus, even less is known about the epidemiology of chronic low-back pain with no associated work disability or compensation. Chronic low-back pain has also become a diagnosis of convenience for many people who are actually disabled for socioeconomic, work-related, or psychological reasons. In fact, some people argue that chronic disability in back pain is primarily related to a psychosocial dysfunction. Because the validity and reliability of some of the existing data are uncertain, caution is needed in an assessment of the information on this type of pain.

Epidemiologic Studies↗
PubMed1999

Comparison of five methods used to determine low back disorder risk in a manufacturing environment.

STUDY DESIGN: Five methods for quantifying work-related low back disorder (LBD) risk were used to assess 178 autoworkers from 93 randomly selected production jobs. OBJECTIVE: To determine if five occupational LBD risk evaluation methods yielded similar assessments of manual material handling tasks. SUMMARY OF BACKGROUND DATA: Several techniques are available for quantifying LBD risk in the workplace and are used in industry for job evaluation and redesign. It is unknown whether the methods yield similar results. METHODS: The five job evaluation methods were the 1993 National Institute for Occupational Safety and Health model, the Static Strength Prediction Program, the Lumbar Motion Monitor model, and two variations of the United Auto Workers (UAW)-General Motors Ergonomic Risk Factor Checklist. These methods were selected because they represent common practice within the automotive industry, the result of governmental efforts to protect the workforce, or models thought to be the most scientifically advanced. RESULTS: Intercorrelations between methods ranged between 0.21 and 0.80. Pairwise analysis of risk group classifications identified biases on the part of the National Institute for Occupational Safety and Health equation, which considered jobs to be of higher risk relative to other methods, and on the part of the Static Strength Prediction Program, which considered nearly all the jobs sampled to be low risk. CONCLUSIONS: There is little agreement among the five quantitative ergonomic analysis methods used. In part, this may be because of their differential focus on acute versus cumulative trauma, thereby suggesting that greater consideration needs to be given to the underlying causes of LBD within a facility before selecting an ergonomic evaluation method.

Ergonomics↗
PubMed1999

The effects of lifting speed on the peak external forward bending, lateral bending, and twisting spine moments.

Lifting tasks that involve twisting have been repeatedly implicated as contributing to the onset of occupational back injuries in epidemiological studies. The objective of this work was to quantify the three directional external moments acting on the spine during a sagittally symmetric and two asymmetric lifting tasks. A total of 15 subjects participated in the three lifting tasks. All tasks were performed at two qualitatively defined lifting speeds, 'slow' and 'fast', and with two load magnitudes: 10 and 20% of the subject's body weight. The mid-sagittal plane lifts were performed using two horizontal reach distances: 40 and 60 cm. A four-camera, two-forceplate motion and force measurement system were used to obtain the kinematic and kinetic data as the lifts were performed. A dynamic link-segment biomechanical model was used to quantify the reaction forces and moments at the ankle, knee, and hip and L5/S1 joints. Results from all tasks showed increased sagittal plane (forward bending) spine moments with the heavier load and at the faster lifting speed (p < 0.001). Spine lateral bending and twisting moments increased during the mid-sagittal plane lifts with the greater reach distance and the faster lifting speed, respectively. The twisting moments on the spine were greatest as subjects lifted from in front and placed the load to the side but were dependent upon the lifting speed and the load magnitude. The lateral bending moments increased during this same task with the heavier load. However, the spine lateral bending moments were greatest when lifting from one side to the other.

Adult↗
PubMed1999

Study on effect of graded facetectomy on change in lumbar motion segment torsional flexibility using three-dimensional continuum contact representation for facet joints.

Facet joints provide rigidity to the lumbar motion segment and thus protect the disk, particularly against torsional injury. A surgical procedure that fully or partially removes the facet joints (facetectomy) will decrease the mechanical stiffness of the motion segment, and potentially place the disk at risk of injury. Analytical models can be used to understand the effect of facet joints on motion segment stability. Using a facet joint model that represents the contact area as contact between two surfaces rather than as point contact, it was concluded that a substantial sudden change in rotational motion, due to applied torsion moment, was observed after 75 percent of any one of the facet joints was removed. Applied torsional moment loading produced coupled extension motion in the intact motion segment. This coupled motion also experienced a large change following complete unilateral facetectomy. Clinically, the present study showed that surgical intervention in the form of unilateral or bilateral total facetectomy might require fusion to reduce the primary torsion motion.

Finite Element Analysis↗
PubMed1998

A new culture system to study the metabolism of the intervertebral disc in vitro.

STUDY DESIGN: This study determined whether entrapment of a rabbit intervertebral disc in alginate gel helped to promote the retention of normal metabolic activities by the nucleus pulposus and anulus fibrosus in tissue culture. OBJECTIVES: To establish an in vitro culture system to study the metabolism of the intervertebral disc as a whole integral organ. SUMMARY OF BACKGROUND DATA: In vitro studies of the metabolism of intervertebral discs have been scarce because of the difficulties involved in maintaining the integrity of the tissues, especially that of the nucleus pulposus, in culture medium. METHODS: Rabbit intervertebral discs were embedded in alginate gel and maintained in culture for as long as 1 month. At weekly intervals, experiments were performed to measure the rate of proteoglycan synthesis and to characterize proteoglycans newly synthesized by cells in the anulus fibrosus and nucleus pulposus. In addition, at these same time intervals, the contents of sulfated proteoglycans, antigenic keratan sulfate, hyaluronan, and collagen in these two intervertebral disc tissues were measured to evaluate tissue integrity. Intervertebral discs cultured in medium alone were used as controls and analyzed in parallel. RESULTS: The anulus fibrosus and nucleus pulposus of intervertebral discs cultured in alginate gel sustained a higher rate of proteoglycan synthesis and maintained a higher content of extracellular matrix components than the respective controls at all times. CONCLUSIONS: This new alginate tissue culture system should prove useful for studying the metabolism of whole intervertebral discs.

Alginates↗
PubMed1998

What are the age-related changes in the spine?

Degenerative changes of the spinal column have long been and continue to be confused with the presence of spinal distress and pain. All parts of the spine undergo degenerative changes as we age. The purpose of this chapter is to describe the degenerative process and its clinical consequences. The disc degenerative process will be discussed; its consequences on the facet joint and osteophyte formation are considered. The prevalence of disc degeneration, the role of physically demanding work and leisure and the interference of spinal deformity is clarified. A section particularly important for the clinician deals with the clinical consequences of the degenerative process in disc herniation, degenerative spondylolisthesis, spondylolysis and stenosis. This chapter tries to put the degenerative changes of the spine into the context of a normal ageing process.

Aging↗
PubMed1998

Trunk kinematics and trunk muscle activity during a rapidly applied load.

This study investigated the trunk kinematics and electromyographic (EMG) activity of eight trunk muscles when "expected" and "unexpected" loads were applied directly to the torso. Twenty individuals (mean age: 25.1 yr; range 20-33 yr) participated in this mixed model study in which gender was the between-subjects factor, and expectancy and symmetry of the applied load were within-subject factors. The sudden load was delivered to the subject via a cable attached to a thoracic harness and motion was restricted to the lumbar spine by strapping the pelvis to a rigid fixation apparatus. Surface EMG was recorded bilaterally from the longissimus thoracis (LGT), erector spinae (ERS), rectus abdominis (RAB) and the external obliques (EXO). Trunk kinematics were measured with a Lumbar Motion Monitor. During expected loading conditions, the peak muscle activity was reduced for the RAB and EXO bilaterally, and for the ERS(R) (p < 0.01) relative to the unexpected conditions. Conversely, the normalized area of EMG activity prior to the onset of load was increased for the ERS and EXO bilaterally, and for the RAB(R) (p < 0.05) during an expected loading event. Trunk motion in the sagittal and frontal planes was reduced during expected loading. Activation of the trunk muscles just prior to a rapid loading event increases trunk stiffness, decreasing trunk displacement and peak muscle activity.

Adult↗
PubMed1998

Trunk muscle use during pulling tasks: effects of a lifting belt and footing conditions.

Pulling tasks require the torso to act as a rigid link in order to facilitate the force transmission between the ground and the hands. In this study, we tested the hypothesis that a lifting belt increases the rigidity of the torso, thereby increasing pulling strength or reducing trunk muscle forces, or both, as pulling tasks are performed. Twelve volunteers performed maximal and submaximal isometric pulling exertions; the latter were performed on nonslippery and slippery surfaces. Electromyographic data from 8 trunk muscles, trunk kinematic data, and ground reaction forces were sampled during each exertion. Results indicated that the lifting belt had no effect during maximal exertions on the maximal pull forces generated or the muscle recruitment levels, irrespective of the pulling posture. The lifting belt did not affect the EMG data obtained during the submaximal (40% of maximum) exertions, even when participants pulled on a slippery surface. However, the slippery surface increased the coactivation within the trunk musculature, perhaps stiffening the torso in the event of a slip. The absence of a statistical interaction effect between the lifting belt and the footing condition (slipperiness) indicates that the belt did not alter the coactivation pattern and hence was not relied upon by the participants as a protective mechanism. The data presented here will assist those who must make decisions regarding lifting-belt use and those who train individuals in manual materials handling techniques.

Adult↗
PubMed1998

A prospective study of 342 patients using transpedicular fixation instrumentation for lumbosacral spine arthrodesis.

The objective of this research was to determine the efficacy and safety of an experimental instrumentation device designed for transpedicular spinal fixation by evaluating fusion rates and clinical pain and function scores; to determine complication rates associated with the device; and to compare the obtained data with that previously published in the literature. Four hundred forty-two consecutive patients were enrolled in this 4-year, Food and Drug Administration-monitored investigational device exemption trial to undergo surgery for implantation of the device. Eighteen surgeons at 11 nationwide medical centers performed the operations and subsequent evaluations. The study population was derived from three diagnostic categories: degenerative disc disease, multioperated back, and vertebral fracture. The data source consisted of radiographs, clinical examination, and structured forms and questionnaires. Patients were evaluated preoperatively, intraoperatively, and postoperatively at 3, 6, 12, and 24 months. By the 24-month postoperative interval, attrition had reduced the study population to 342 patients, among whom bony fusion was obtained in 91.5%. Pain scores demonstrated a statistically significant improvement in clinical outcome. Intraoperative complications occurred in 21.9% of patients. Of the 442 study patients, 2.9% experienced device-related complications. Moreover, a total of 2,304 screws and bolts were implanted in this patient population. Of these, 0.39% were reported to have fractured. Among the 342 study patients observed during 24 months, the breakage rate of device components (bolt or screw) was 2.63%. These data compare favorably to existing reports of spinal arthrodesis effected with other types of instrumentation and without device implantation. In a 4-year trial, the experimental transpedicular fixation instrumentation produced successful spinal fusion in the majority of our study population, with acceptable complication rates.

Activities of Daily Living↗
PubMed1998

Diagnostic considerations in patients with back pain.

It should be obvious from this article that usually only a focused history and physical examination are needed to evaluate a back patient. A summary of guideline recommendations presented by the Agency for Health Care Policy and Research is provided in Table 7. If followed, few serious mistakes will occur, and a more cost-effective management of the back patient will be possible.

Back Pain↗
PubMed1997

Metabolism of the extracellular matrix formed by intervertebral disc cells cultured in alginate.

STUDY DESIGN: Cells from normal rabbit nucleus pulposus (NP) and anulus fibrosus (AF) were cultured in alginate beads for as long as 14 days to allow them to reform a matrix made up of two compartments: the cell-associated matrix (CM) and further removed matrix (FRM). At different time points, the CM and FRM made by each cell population were analyzed using histologic, biochemical, and immunologic assays. OBJECTIVES: To study the metabolism of normal rabbit NP and AF cells in alginate by characterizing the CM and FRM formed by each cell population, and to identify metabolic properties that may shed light on mechanisms at play in disc degeneration. SUMMARY OF BACKGROUND DATA: Little is known about the metabolism of intervertebral disc cells, in part because of the lack of microculture systems appropriate for the study of these cells in vitro. In recent studies from our laboratories, it was suggested that articular chondrocytes cultured in alginate beads remain phenotypically stable and reform a matrix similar to the one they populate in vivo. This culture system appears ideally suited for the study of intervertebral cells available only in limited numbers. METHODS: Rabbit NP and AF cells released from the matrix by sequential enzyme digestion were encapsulated in alginate beads (20,000 cells/bead) and cultured for as long as 14 days. At selected time points, beads were solubilized with calcium chelating agents, and the CM and FRM were isolated. The rate of 35S-sulfate incorporation into proteoglycans, and the contents of various extracellular matrix molecules (total sulfated proteoglycans, antigenic keratan sulfate, hyaluronan, collagen, and pyridinium crosslinks) were measured. RESULTS: Both NP and AF cells remained phenotypically stable in the alginate gel throughout the culture period and reestablished a matrix composed of CM and FRM compartments. The two cell populations exhibited numerous differences in their metabolic activities in vitro. Nucleus pulposus cells synthesized fewer proteoglycan and collagen molecules and were less effective in incorporating these into the CM than AF cells. CONCLUSIONS: Intervertebral disc cells, especially NP cells, are extremely sluggish in reforming a CM, a protective shell rich in proteoglycans and collagen molecules. This may help explain why damage to the NP often is accompanied by progressive degeneration of the disc in vivo.

Alginates↗
PubMed1997

Low back pain.

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Humans↗
PubMed1996

Disc herniation.

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Humans↗
PubMed1996

History and physical examination in patients with herniated lumbar discs.

To outline the usefulness of the medical history and physical examination in the diagnosis of herniated lumbar discs, and to review the essential properties of a test, including sensitivity, specificity, and clinical value. None of the tests that are part of a history and physical examination of a patient with a disc herniation has a high diagnostic accuracy by itself. This is because positive and negative predictive values of common clinical indicators are limited. Confirmatory tests are necessary for a definitive diagnosis when making management decisions. Combining the results of history and physical findings will increase the predictive value of these basic diagnostic tools.

Humans↗
PubMed1996

Consensus summary of the diagnosis and treatment of lumbar disc herniation.

Clinicians must not simply decide that a patient with symptoms and a positive diagnostic test has a reason for a specific treatment, and likewise clinicians must not decide that a patient with symptoms and a negative test does not have a clinically important problem. We must also consider the sensitivity, specificity and predictive value of the diagnostic test and the individual characteristics of the patient. Treatment outcome depends on many factors. Point of service decisions vs population based decisions are obviously different. Each patient presents to the treating practitioner on a given day, at a given time, and it is this picture upon which a plan of care is formulated.

Humans↗
PubMed1996

Bacterial discitis caused by limb gangrene requiring below-knee amputation.

Two patients presented with disabling back pain and were unable to participate in physical therapy activities after being admitted to an acute rehabilitation center. Both patients had bacterial discitis of the lumbar spine that was apparently caused by infected ischemic limb tissue, ultimately removed at below-knee amputation. The literature describes many cases of bacterial discitis infected from many sources, but not from ischemic limb tissue requiring subsequent amputation. Many such cases may exist, however, and earlier recognition of this condition will enable appropriate treatment before vertebral destruction and/or neurological sequelae.

Aged↗