Do variations in paraspinal muscle morphology and composition predict low back pain in men?

This longitudinal study aimed to clarify the longstanding controversy over whether variations in paraspinal muscle morphology (e.g., size, composition and asymmetry) are predictors of low back pain (LBP). A sample of 99 Finnish men were included in this population-based longitudinal study. Data were collected through a structured interview, physical examination and magnetic resonance imaging (MRI). Baseline measurements of the lumbar multifidus and erector spinae muscles were obtained from T2-weighted axial images at L3-L4 and L5-S1, and interview data were obtained at baseline, 1- and 15-year follow-ups. Few of the paraspinal muscle parameters investigated were predictors of change in LBP frequency, intensity or sciatica at 1- and 15-year follow-ups in the population-based sample, and findings were not consistent across muscles and spinal levels. However, greater multifidus and erector spinae fatty infiltration at L5-S1 was associated with a higher risk of having continued, frequent, persistent LBP at 1-year follow-up. None of the relationships observed was confounded by body mass index or the amount of physical activity at work or leisure. This longitudinal study provided evidence that variations in paraspinal muscle morphology on MRI have a limited, if not uncertain, role in the short- and long-term predictions of LBP in men.

Neck trouble in machine operating, dynamic physical work and sedentary work: a prospective study on occupational and individual risk factors.

A prospective study on the effects of occupational and individual factors on neck trouble was carried out among 1832 men representing static work with whole-body vibration (machine operators), dynamic physical work (construction carpenters) and sedentary work (office workers). Neck trouble and occupational and individual factors were inquired about via postal questionnaires in 1984 and 1987. Machine operating was associated with an increased risk to contract severe neck trouble, and machine operating and dynamic physical work were associated with persistently severe neck trouble. Other predictors for contracting severe neck trouble were age and current smoking. Physical exercise decreased the risk of persistently severe neck trouble. The results of our prospective study confirm the role of physical factors in neck trouble.

Determinants of psychomotor speed among 61 pairs of adult male monozygotic twins.

BACKGROUND: Declining psychomotor speed is an indicator of the aging process, and it is influenced by genetics and environmental factors. The present study examined the relative effects of familial aggregation (reflecting a combination of genetics and early environmental influences), and occupational, lifestyle, and health factors on psychomotor speed. METHODS: Hand and foot psychomotor speed was studied with 61 pairs of monozygotic male twins aged 35-67 years from the population-based Finnish Twin Cohort. The determinants of visual simple and choice reaction times were analyzed with multiple regression analysis. RESULTS: Familial aggregation, reflecting genetic influences and shared environmental effects, explained in mean 47% of decision times, 31% of movement times, and 37% of response times (decision time and movement time combined). Age, cardiovascular morbidity, lifetime vigorous and frequent exercise participation, and mean lifetime daily hours sitting at work explained 0-19% of hand psychomotor speed and 0-10% of foot speed, depending on the outcome. The predicted increase in decision times due to the presence of cardiovascular morbidity was 11-35 ms. The predicted increase for hand and contralateral foot response times between ages 45 and 55 was 18-41 ms. Smaller effects were noted for each year of strenuous exercise and each hour/day of average lifetime sitting at work. CONCLUSIONS: Results indicate that cardiovascular status, age, strenuous exercise, and work play a role in psychomotor speed, but a rather minor one. In contrast, genetic and shared early environmental influences as revealed from familial aggregation were relatively strong, yet a major proportion of the variability in psychomotor speed remained unexplained.

Experimental study on the repair of full thickness articular cartilage defects: effects of varying periods of continuous passive motion, cage activity, and immobilization.

In order to clarify the dose/response characteristics of continuous passive motion (CPM), the repair response of full thickness articular cartilage defects was studied in a rabbit model. The following combinations of CPM and immobilization (Imm) were utilized: CPM, 24 h/day; CPM, 8 h/day and Imm, 16 h/day; CPM, 2 h/day and Imm 22 h/day; Imm 24 h/day; and normal cage activity. These regimens were used only in the initial week and then all rabbits were permitted to move freely in their cages, except for a sixth Imm-CPM group that was kept immobilized in the initial week and then CPM 24 h/day for another week. The CPM 24 h/day and the CPM 8 h/day groups (groups 1 and 4, respectively) showed better repair than the other groups, i.e., better surface congruity, larger positive Safranin-O staining area, and greater number of chondrocytes in the repair tissue. The CPM 2 h/day group (group 3), however, showed only slightly better repair than the Imm group (group 4). The CPM following immobilization was not effective to overcome the harmful effect of immobilization. We conclude that in the present model, CPM for 8 or 24 h/day is effective for adequate cartilage repair even with some component of immobilization. Its application should be at least 8 h/day. On the contrary, if CPM is delayed for a week following immobilization, the effect of CPM on cartilage will be reduced.

Biomechanical time-tolerance of fresh cadaveric human spine specimens.

Changes in the biomechanical properties of fresh cadaveric spinal specimens due to long-term freeze storage and long test periods have been investigated. Fresh cadaveric specimens were divided into three groups: Group A specimens were tested fresh on the 1st day and 13 subsequent days; Group B specimens were tested on the 1st day, frozen in sealed bags at -18 degrees C for 21 days, and tested for 13 consecutive days after thawing; and Group C specimens were frozen for up to 232 days and tested for 14 consecutive days after thawing. We could not find any significant differences between the behavior of the three test groups. This implies that freezing and storage, even for long periods, do not significantly alter the physical properties of cadaveric spinal specimens. Concerning the differences observed on a daily basis, the mean value of the maximum displacement for the 1st day did not differ significantly from the corresponding mean value for the 13 consecutive days. This was true for all three groups, although there was some indication that the fresh group specimens showed greater variation than the two frozen groups.

Bone ingrowth into porous calcium phosphate ceramics: influence of pulsing electromagnetic field.

The effect of a pulsing electromagnetic field (PEMF) on bone ingrowth into porous hydroxyapatite (HA) and porous tricalcium phosphate (TCP) implanted in rabbit tibiae was studied. To quantitate the biological response, a recently developed method of surface measurement using a scanning electron microscope was used. The morphometrical findings in the HA pores demonstrated a significantly greater amount of bone and thicker bone trabeculae in the PEMF group as compared with the nonpulsed control group at 3 to 4 weeks postimplantation. No significant differences for these parameters were found in the TCP pores. Histologically, more bone and wider bone trabeculae were observed in the HA implants for the PEMF-treated animals at the early time periods when compared with those of the control animals. Alternatively, the histological findings of the TCP implants were similar between these two groups. These histological results tended to correlate with the morphometrical data. Together, these results suggest that accelerated bone formation and bone maturation occurred in response to PEMF in the HA pores but was without effect in the TCP pores. This stimulatory effect is most significant after 3-4 weeks of PEMF stimulation.

Three-dimensional load-displacement curves due to forces on the cervical spine.

Load-displacement curves were measured for six types of pure force loading of the cervical spine specimens obtained from fresh human cadavers. A new measuring and mounting technique was developed that yielded data for all of the functional spinal units for each specimen tested. All five of the coupled, as well as the main, load-displacement curves were studied. For anterior and posterior shear loadings, the main resulting motions were translation in that direction (1.6 +/- 0.3 and 1.9 +/- 0.3 mm), and the major coupled motions were flexion and extension (3.6 degrees +/- 1.2 degrees and 6.3 degrees +/- 1.2 degrees). The main motions with right and left lateral shear loadings were translations laterally (1.4 +/- 0.3 and 1.6 +/- 0.3 mm), and the major coupled motions were axial rotations (1.5 degrees +/- 0.6 degrees and 2.3 degrees +/- 0.6 degrees) and not lateral bending. For compression and distraction loadings, the main motions were translations in that direction (0.7 +/- 0.3 and 1.1 +/- 0.3 mm), and the major coupled motions were flexion and extension (2.0 degrees +/- 1.0 degrees and 2.8 degrees +/- 1.0 degrees) and lateral bending (1.4 degrees +/- 0.3 degrees and 1.9 degrees +/- 0.3 degrees). The neutral zones for anterior and posterior shear forces were 1.6 +/- 0.2 mm of translation and 5.8 degrees +/- 1.3 degrees of rotation, for lateral shear force 1.4 +/- 0.3 mm and 2.0 degrees +/- 0.5 degrees, and for compression/distraction 0.6 +/- 0.1 mm and 2.8 degrees +/- 0.9 degrees.

Disc degeneration and bone density in monozygotic twins discordant for insulin-dependent diabetes mellitus.

The effects of insulin-dependent diabetes mellitus on bone density and connective tissue degeneration have theoretical interest and practical relevance. Several experimental studies in animals have demonstrated the harmful effects of insulin deficiency on connective tissues. However, clinical studies in humans have produced somewhat contradictory results, most likely due to difficulties controlling for general degeneration and factors associated with diabetes. In nine pairs of monozygotic twins discordant for insulin-dependent diabetes mellitus, we compared femoral and lumbar bone mineral density (assessed by dual-energy x-ray absorptiometry) and spinal degeneration (assessed by magnetic resonance imaging). The bone densities were, on average, 0.1-0.3% lower (p = 0.87-0.96) in diabetic patients. However, after controlling for smoking, we found that the bone density in the femoral neck was 2.5% (0.025 g/cm2) lower in diabetic individuals than in their twins (p = 0.09). The five magnetic resonance imaging parameters used to evaluate disc degeneration did not differ between diabetic patients and their twins. In conclusion, our results provide no evidence that insulin-dependent diabetes mellitus has any major effect on bone density or disc degeneration.

Double-blind parallel study of meptazinol versus diflunisal in the treatment of lumbago.

Seventy out-patients with acute back pain participated in a double-blind comparative trial of the clinical efficacy and tolerance of orally administered meptazinol and diflunisal. Half of the patients received 200 mg meptazinol or 250 mg diflunisal 4-times daily for up to 3 weeks, depending on the duration of pain. Patients were examined 4 times at 1-week intervals for their capability to do daily tasks, for their capacity for forward bending, thoraco-lumbar torsion, straight leg raising, static hip flexion and sit-ups, and for subjective assessment of pain. Side-effects were recorded on a questionnaire. Both treatments produced marked improvement in most of the parameters assessed, often within the first week and, overall, the results were similar with the two drugs. Few side-effects were reported and those that were recorded were slight and similar in incidence apart from nausea in 5 meptazinol-treated patients and smarting and burning on urination in 2 patients receiving diflunisal.

The effect of lifelong exercise on psychomotor reaction time: a study of 38 pairs of male monozygotic twins.

PURPOSE: The aim was to study the effect of lifetime physical activity on psychomotor speed. METHODS: Foot and dominant hand visual simple and choice psychomotor reaction times were studied among monozygotic twins (38 pairs) aged 35-69, discordant for lifetime exercise histories. RESULTS: There was a trend that some components of psychomotor reaction time were faster for frequent than for occasional exercisers, but the findings were not consistent for the hand and feet. After controlling for occupational physical activity, only choice decision time for the hand (26 ms, P < 0.01) and choice reaction time for the contralateral foot (51 ms, P < 0.05) both remained 7% faster. There was no trend for systematic differences in reaction times between twins engaged in regular exercise versus their siblings exercising infrequently. CONCLUSIONS: Results suggest a somewhat smaller effect of exercise than reported in previous studies. Reaction time may be significantly affected only by vigorous, frequent exercise. Thus, health promotion through exercise may be unlikely to have notable effects on reaction time.

Lifetime exercise and disk degeneration: an MRI study of monozygotic twins.

Participation in some competitive sports has been shown to increase disk degeneration; however, the long-term effects of recreational physical activities are unclear. We investigated the effects of endurance exercise and power sports on disk degeneration in monozygotic male twins with contrasting lifetime exercise histories. The effects of endurance exercise were studied in 22 discordant twin pairs (mean lifetime frequencies of 3.9 vs 1.1 times/wk), and the effects of power sports were investigated in 12 discordant pairs (2,300 vs 200 h of weightlifting). The age range of the twins was from 35 to 69 yr. No differences in MRI findings between co-twins discordant for endurance exercise were found at any of the spinal regions. Subjects with more power sport involvement had greater disk degeneration in the T6-T12 region (P < 0.03), but similar findings were not present in the lumbar spine. Controlling for recalled back injuries, occupational loading, smoking, and driving did not significantly affect the results. No signs of beneficial or harmful effects of lifetime endurance exercise on disk degeneration were seen. Increased power sport participation was associated with slightly greater disk degeneration in the lower thoracic spine, but not in the lumbar spine.

Similarities in degenerative findings on magnetic resonance images of the lumbar spines of identical twins.

Although the etiology of most degenerative changes in the lumbar spine is unclear, genetic factors may play an important role. To investigate this link, we reviewed magnetic resonance images of the lumbar spines of identical twins to assess the degree of similarities in degenerative findings in the discs. Observers who were blinded to twinship evaluated sagittal T1-weighted and T2-weighted magnetic resonance images of the lumbar spines of forty male identical twins (twenty pairs) with respect to changes in the end plates, desiccation of the discs, bulging or herniated discs, and decrease in the height of the disc space. Similarities between co-twins were significantly greater than would be expected by chance. Whereas smoking status and age explained 0 to 15 per cent of the variability in the various degenerative findings in the discs, 26 to 72 per cent of the variability was explained with the addition of a variable representing co-twin status. These findings are compatible with a marked genetic influence and warrant further investigation.

The value of the axial view in assessing discograms. An experimental study with cadavers.

The clinical value of discography is controversial. An axial view of a discogram such as could be obtained with CT scans should increase the structural information regarding disc pathology, and clarify the relationship to disease of the facet joints as well. To evaluate this concept, 103 intervertebral levels in 23 cadaver specimens were studied by anteroposterior, lateral, and axial roentgenographic views. From these three views, a new classification for interpreting discograms was developed. The correlations between the three different views were good, confirming the potential value of CT axial views. However, in one fourth of the discs there were pathologic anatomic findings that could be seen only in the axial views. There were more severe osteoarthritic changes in the right than the left facet joint, and a discrepancy between facet arthritis and disc disease was also noted.

The influence of occupation on lumbar degeneration.

In many countries, back problems have been defined as occupational injuries. The belief underlying this injury model is that back symptoms are caused primarily by work-related mechanical factors that damage the structures of the spine, either through a single incident or repeated loading. Although the etiopathogenesis of degenerative findings in the disc and their relation to pain are poorly understood, changes in the disc are suspected of underlying many back symptoms. The focus of this article is on examining the relation between occupational factors and disc degeneration. Occupational factors suspected of accelerating spinal degeneration include accident-related trauma; heavy physical loading and materials handling, including lifting, bending, and twisting; prolonged sitting; and sustained nonneutral work postures and vehicular driving. There is evidence to suggest that occupational exposures have an effect on disc degeneration. However, these factors explain little of the variability in degeneration found in the adult population. Furthermore, the lack of a clear dose-response relation between time spent in various occupational loading conditions and degenerative findings adds to doubts about a strong causal link. The contribution of suspected occupational risk factors appears to be particularly modest when compared with familial influences, which reflect the combined effects of genes and early childhood environment. These findings challenge the dominant role assumed for occupational loading in disc degeneration and associated back problems, and suggest a more complex etiology.

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.

1990 Volvo Award in clinical sciences. Lumbar spinal pathology in cadaveric material in relation to history of back pain, occupation, and physical loading.

The occurrence of symmetric disc degeneration, anular ruptures, end-plate defects, vertebral body osteophytosis, and facet joint osteoarthrosis was examined radiographically and osteologically in 86 male cadavers for whom occupational, physical loading, and back pain histories were obtained from the men's families. History of back pain and the parameters of spinal pathology were related to the highest and lowest degrees of physical loading. In multivariate analyses, history of back injury was related to the occurrence of symmetric disc degeneration, anular ruptures, and vertebral osteophytosis. Symmetric disc degeneration was associated with sedentary work, and vertebral osteophytosis was related to heavy work. History of back pain was related to occupational physical loading after control for the effects of the other covariates. The results indicate that the least pathology stemmed from moderate or mixed physical loading, but the least back pain was associated with sedentary work.

Low-back pain and occupation. A cross-sectional questionnaire study of men in machine operating, dynamic physical work, and sedentary work.

The frequency of sciatic pain, lumbago, and nonspecific low-back pain (LBP) and factors related to these symptoms were determined among men occupied in machine operating (541 longshoremen and 311 earthmover operators), dynamic physical work (696 carpenters), and sedentary work (674 municipal office workers). Sciatic pain was more common among machine operators and carpenters than among office workers, and also more frequent among machine operators than among carpenters. The occupational differences were considerably smaller with regard to lumbago and nonspecific LBP. In multivariate analysis, occupation, age, reported back accidents, and postural load showed significant independent effects on the occurrence of sciatic pain. Allowing for other risk indicators, the relative risk was 1.3 contrasting machine operators with both office workers and carpenters, but carpenters had no excess risk as compared with office workers.

Plain radiographic, discographic, and direct observations of Schmorl's nodes in the thoracolumbar junctional region of the cadaveric spine.

The perceivability of Schmorl's nodes in plain radiographs and discograms in the thoracolumbar junctional region (T10-L1) of the cadaveric spine was assessed by comparing the radiologic measurements with bone measurements. Schmorl's nodes in bone specimens were encountered in 19 of 24 spines studied. They were more than two times as common between vertebrae T10-11 and T11-12 as between T12 and L1 (P less than 0.01). When the areas of actual Schmorl's nodes exceeded 0.5 cm2 (corresponding to an aperture with a diameter of 0.8 cm), 47% of the nodes were seen in plain lateral radiographs and 68% in discograms. When the area measured 0.5 cm2 or less, only 24% could be perceived in plain lateral radiographs and 23% in discograms. The clinical significance of Schmorl's nodes remains uncertain as long as they are difficult to detect in vivo.

Facet joint orientation, facet and costovertebral joint osteoarthrosis, disc degeneration, vertebral body osteophytosis, and Schmorl's nodes in the thoracolumbar junctional region of cadaveric spines.

The disc degeneration in the thoracolumbar junctional region (T10-L1) of 37 male cadaveric spines was recorded with the use of discography. From 24 of these spines the facet joint orientation and degenerative findings of the facet and costovertebral joints, vertebral bodies (osteophytosis) and discs, and Schmorl's nodes were recorded directly from bones. At T11-12, the most common site for the transitional zone between thoracic and lumbar facet type, there was a marked variation in the orientation of facets. The occurrence of degenerative findings and Schmorl's nodes at the three levels in the region differed. At T10-11, disc degeneration, vertebral body osteophytosis, and Schmorl's nodes were most common (anterior degeneration). At T12-L1, facet and costovertebral joint degeneration were dominant (posterior degeneration). At T11-12, disc degeneration, vertebral body osteophytosis, Schmorl's nodes, and facet and costovertebral joint degeneration all occurred (anterior and posterior degeneration). The results point to a pathoanatomic association between degenerative changes and facet orientation.

Digital assessment of MRI for lumbar disc desiccation. A comparison of digital versus subjective assessments and digital intensity profiles versus discogram and macroanatomic findings.

During magnetic resonance imaging, a vast amount of digital data on anatomic structures is translated into images, which are then assessed subjectively. The development of an objective, sensitive method to directly assess the digital data would have clear benefits, particularly for clinical research on disc degeneration. The study goals were to develop a method of digital assessment of disc desiccation and to compare digital signal intensity profiles with discographic patterns and macroanatomic findings. Proton density-weighted MRIs were obtained from 45 males (9-77 years) and digital analysis was done with a freely selectable region of interest facility. The adjacent cerebrospinal fluid (CSF) was used as a reference for disc signal-intensity scores, and the disc to CSF-intensity ratio provided "adjusted digital scores." The CSF-adjusted digital method yielded reproducible scores that correlated with the subjective assessments. However, the CSF-adjusted digital scores were more sensitive than the subjective assessments, identifying findings that otherwise were undetected in younger subjects. Additionally, 10 cadaveric spines were evaluated using MRI with T2 and proton density-weighted sequences, discography, and macroanatomic dissection. MRI disc-intensity profiles were determined along a midsagittal line drawn through the disc. The profile of the digital scores along this line was then compared with discograms and macroanatomic sections. In all cases of disc degeneration on discograms, changes were present in the intensity profile. Based on both the living subjects and the cadaveric specimens, the digital assessments and disc intensity profiles appear to demonstrate disc degeneration, particularly in early stages.