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Biomedical subjects

T Hansson

Publications and source records attributed to T Hansson.

At least 73 records · Page 4Linked to original sources
PubMed1993

Structural properties of the anterior longitudinal ligament. Correlation with lumbar bone mineral content.

The relationship between the amount of bone in the lumbar spine and ligamentous properties has not been studied. This article reports the tensile structural properties of bone-ligament-bone preparations of the anterior longitudinal ligament from 15 human lumbar spine segments. Significant correlations were found between the vertebral bone mineral content expressed as BMC (g/cm) and BMA (g/cm2) and BMD (g/cm3) and the structural properties of the vertebral bone-anterior longitudinal ligament-bone complex determined at yield and failure. These findings suggest that the amount of bone tissue in the spine may be functionally related to structural properties of the spinal ligaments.

Adult↗
PubMed1993

Reduced bone mineral content in adult patients with growth hormone deficiency.

Bone mineral content was measured in a follow-up study of adult patients with hypopituitarism and growth hormone deficiency. There were 95 patients (59 males, mean age 54.0 years, range 21-74 years; 36 females, mean age 53.5 years, range 31-73 years). Routine replacement therapy with cortisone acetate and L-thyroxine was given. All males that were gonadal deficient were on proper testosterone therapy, except in four patients who were treated separately. Bone mineral content (g/cm) was measured using dual-photon absorptiometry in the third lumbar vertebra. Bone mineral content in the patients was compared with a control population (N = 413, 25-74 years of age). Bone mineral content was significantly lower in males (N = 55, p < 0.05) compared with controls. In females, bone mineral content was significantly lower both among the subjects with untreated gonadal deficiency (p < 0.001) and among those with treated gonadal deficiency and normal premenopausal gonadal function (p < 0.005) compared with controls. To summarize, patients with hypopituitarism on routine replacement therapy but not growth hormone have a lower bone mineral content than the controls. The reduced bone mineral content might be a result of untreated growth hormone deficiency.

Adult↗
PubMed1993

B-scan ultrasonic measurement of the lumbar spinal canal as a predictor of industrial back pain complaints and extended work loss.

B-scan ultrasonic measurements of lumbar spinal canal diameter were examined as predictors of industrial back pain complaints and extended work loss. Baseline data were collected on 3,020 Washington State aircraft manufacturing workers, and over a mean 3.7-year follow-up period 352 subjects reported industrial back pain complaints. Mean canal measurements of subjects with industrial back pain complaints were smaller at all spinal levels than in subjects without complaints. The mean differences between the groups, however, were extremely small (0.07 mm to 0.51 mm), and not all levels were statistically significant. The relative risk for an L5-S1 measurement 2 standard deviations below the mean was 1.4, yet the measurement explained less than 1% of the uncertainty in predicting complaints. No association was found between canal measurements and claims with extended work loss of greater than one month. The imprecision of the measurements and poor predictive ability indicate that B-scan ultrasonography, as used in this study, is of dubious screening value.

Absenteeism↗
PubMed1992

A method for the intravital measurement of interspinous kinematics.

A novel non-radiographic technique for objectively quantifying quasi-static or dynamic intervertebral motion of a spinal motion segment in vivo in human subjects is presented here. The intervertebral motion device (IMD) is an instrumented linkage transducer system which can continuously measure over time two-dimensional sagittal plane rigid-body motion. Three custom-built omega-shaped displacement transducers are utilized. The IMD is rigidly fixed to the spinous processes of the lumbar motion segment by means of two intraosseous pins. Knowing the mechanoelectrical behavior and geometric configuration of the IMD, the relative spatial motion between the vertebral bodies can be resolved into sagittal rotation, axial translation, and anterior-posterior shear translation. Static calibrations of the IMD in the ranges of +/- 4 degrees rotation and +/- 4 mm translation determined the absolute maximum errors to be 0.2 degree and 0.07 mm for rotation and translation measurements, respectively, with corresponding variances of 0.1 degrees and 0.03 mm. For use in the vibration environment, negligible motion artifact content was detected in the IMD output signals when excited at discrete frequencies of 5.0 and 8.0 Hz. The first natural frequency of the IMD, specific for this design, was measured at 16.25 Hz. This technique may be used to study in vivo the spinal kinematics in healthy lumbar motion segments and in patients suspected of having segmental instability, and can perhaps be of clinical diagnostic significance.

Bone Nails↗
PubMed1992

Accuracy, precision, and homogeneity effects in the determination of the bone mineral content with dual photon absorptiometry in the heel bone.

In this work the distribution of bone mineral content (BMC) in the calcaneus has been studied by means of dual photon absorptiometry. The bone mineral content determined according to the described method is corrected for the amount of fat and lean soft tissue in the path of the radiation beam. It is found that the bone mineral content shows a large variation in the calcaneus. There does, however, exists a homogeneous region in the central part of the calcaneus. The in vitro precision of the technique has been determined to be 1.02%, and the in vivo precision has been found to be 2.8%. The correlation coefficient between ashed bone mass and measured BMC value was 0.97.

Absorptiometry, Photon↗
PubMed1992

Measurement of height loss during whole body vibrations.

An experimental, in vivo study was performed to measure height changes in subjects exposed to whole body vibrations while seated. Twelve women, with an average age of 22 years, were exposed to sinusoidal vibrations for 5 mins. The vibration frequency was 5 Hz, and the acceleration was 0.1 g Rms. The height loss stemming from vibration exposure was compared with that experienced while sitting without being subjected to vibrations. The height losses that always occurred from the two exposures were corrected for the effect of posture change. The height loss from vibration was significantly greater than when no vibration was present. Height loss due to posture change was responsible for approximately 50% of the total height loss. From this study it was concluded that whole body vibrations cause increased height loss.

Adult↗
PubMed1992

The mechanism of initial flexion-distraction injury in the lumbar spine.

The threshold for flexion-distraction injuries was determined on lumbar functional spinal units exposed to a combined flexion-shear load in the sagittal plane. The specimens could resist a bending moment of 121 Nm and a shear force of 486 N at the first sign of a permanent deformation of the osteoligamentous components, which occurred at 78% of the assumed ultimate strength of each specimen. The flexion angulation was 16 degrees. The bone mineral content determined in adjacent vertebrae by means of dual photon absorptiometry was an accurate predictor of structural properties of the entire functional spinal unit even at the first sign of a substantial structural injury and not only at ultimate failure as previously demonstrated.

Bone Density↗
PubMed1992

Different regiospecificity in the hydroxylation of the antidepressant desmethylimipramine between rat brain and liver.

Incubation of the tricyclic antidepressant desmethylimpramine (DMI) with rat liver or brain microsomes in the presence of NADPH or t-butyl-hydroperoxide (TBH) revealed different regiospecificities in the hydroxylation reactions between the tissues. In brain preparations 10-OH-DMI was formed in reactions supported by NADPH or TBH, whereas in the latter case also an unidentified metabolite could be detected. Inclusion of exogenous NADPH-cytochrome P450 reductase in the brain preparations caused a 10-fold higher rate of 10-hydroxylation but no 2-OH-DMI could be detected. By contrast, liver microsomal preparations in the presence of NADPH catalyzed formation of both 2- and 10-OH-DMI, whereas only 10-OH-DMI was formed in TBH-supported reactions. The results indicate that antidepressant drugs can be metabolized in brain with different stereospecificity as compared to liver.

Animals↗
PubMed1992

The value of preemployment roentgenographs for predicting acute back injury claims and chronic back pain disability.

Preemployment roentgenographs have long been used in industry to screen job applicants. Roentgenographs have had little effect, however, in curbing the cost of back problems in industry. This study evaluates the capabilities of preemployment roentgenographs for predicting acute back injury claims within the longshoring industry and for predicting back problems that lead to back disability of more than six months. The data indicate that lumbosacral roentgenographs are not helpful in predicting who is more likely to make a back injury claim, or those few who make up the vast majority of the costs for industrial back pain by becoming disabled for more than six months. Lumbosacral roentgenographs have little link to back disorders and may be viewed as discriminatory. The radiation exposure is not justified by their predictive value as a preemployment screening tool.

Acute Disease↗
PubMed1992

A longitudinal, prospective study of industrial back injury reporting.

The authors prospectively evaluated 3020 volunteers of the Boeing-Everett plant to assess risk factors that predispose workers to file industrial back injury claims. During four years of follow-up observation, more than 279 subjects reported acute back problems. The effect of the only predictive physical variable was explainable by a history of medical treatment. The most predictive individual factors were (1) job task dissatisfaction and (2) distress as reported on Scale 3 of the Minnesota Multiphasic Personality Inventory (MMPI). This data perhaps explains why the focus on purely physical and injury-related factors has met with little success in dealing with what has become the most expensive orthopedic problem. Clinically, nonphysical factors that significantly impact the reporting of back injuries may also affect patients' responses to medical treatment.

Accidents, Occupational↗
PubMed1991

The impact response of the seated subject.

An impact method for establishing the dynamic response of the seated subject is introduced. The method employs a pendulum to apply the impact to the suspended seat. Pins are placed in the spinous process at L3. Highly reproducible results are obtained. The results were not affected by the amplitude of impact, implying a linear system. A marked peak of transmissibility is found in the 4-5 Hz range and an attenuation peak is found close to 8 Hz. Both muscle contraction and postural changes affect the dynamic response. A relaxed posture shows greater gain and attenuation peaks. A valsalva stiffens the system and reduces the effective damping. The vertical response of the body probably shows in the 5-6 Hz peak, while the rotational response is probably encompassed in the 8 Hz attenuation peak.

Adult↗
PubMed1991

Bone mineral content in relation to lactation history in pre- and postmenopausal women.

Bone mineral content in the lumbar spine was studied in relation to lactation history and number of live births in 126 pre- and postmenopausal Swedish women. Total number of months of breastfeeding was significantly associated with low bone mineral content, and the strength of the association was greatly enhanced by statistical adjustment for menopausal status and body weight. Women with higher parity also had lower bone mineral content, but this observation could be attributed to more breastfeeding among that group.

Bone Density↗
PubMed1991

Workload and musculoskeletal problems: a comparison between welders and office clerks (with reference also to fishermen).

Previous studies have shown that subjective as well as clinical shoulder signs and symptoms are more common among welders than among office clerks. In the present study we wished to further evaluate the influence of different jobs on musculoskeletal problems, as well as the relationship between objective signs and subjective symptoms. This study confirmed that symptoms and signs from the shoulder were more common among the welders, who also had more subjective symptoms and clinical signs from other parts of the musculoskeletal system. Range of motion in different joint systems was, however, similar in the two groups except in external rotation of the shoulder, where welders had a more limited range. The degree of co-existence of subjective symptoms and clinical signs differed between different parts of the musculoskeletal system and was low particularly in the low back, hips, and ankles. This indicates low validity of many common clinical methods for determining musculoskeletal dysfunction. General health was good in both vocational groups and isometric strength for the welders was intermediate between that of office clerks (who had lower strength) and that of fishermen (who had higher strength, as disclosed in a previous investigation). To a similar degree welders and fishermen also had objective signs from most parts of the musculoskeletal system, whereas subjective symptoms from some parts of the body and medical consultations due to these problems were more common among welders. Atrophied shoulder muscles were more common among welders than among fishermen, whereas crepitations in the shoulder tended to be more common among the fishermen. This indicates that heavy dynamic work and prolonged static work may both induce shoulder injuries, but of different types.

Adult↗
PubMed1991

Intervertebral motion during vibration.

Vibration exposure is widely recognized as a risk factor for low back pain. An experimental protocol was designed to quantify the intervertebral motion response in human subjects to sinusoidal vertical vibration at 5 and 8 Hz, and at a variety of acceleration levels. Intervertebral motion in the mid-sagittal plane was measured using a transducer linkage system attached to pins placed directly into the spinous processes of adjacent vertebrae. The postures of the subjects were carefully controlled. The effects of forward flexion, arm support, gravitational load, and sitting on a cushion were evaluated. The rigid body motion of the superior vertebra with respect to the inferior vertebra was expressed in terms of relative sagittal plane rotation, axial translation, and anterior-posterior shear translation. It was found that the lumbar motion segments exhibited coupled periodic behaviour in response to sinusoidal vertical vibration, with up to 1 mm peak-to-peak displacement in the axial direction. The greatest intervertebral motion occurred when the subject was exposed to 5 Hz vibration as compared to 8 Hz. For a constant frequency of 5 Hz excitation, the peak-to-peak amplitudes of the computed motions tended to increase as the acceleration level increased. In the flexed posture, with no arm support, the active trunk musculature helped reduce the intervertebral motion. Additional gravitational load on the shoulders caused increased relative axial displacement. A polyethylene foam cushion placed on the seat reduced vibration transmission at 5 Hz excitation and consequently decreased the intervertebral motion.

Adult↗
PubMed1991

Clinical implications of vibration-induced changes in the lumbar spine.

There are strong indications that whole body vibrations are involved in the pathophysiology of different spinal aberrations known or assumed to generate back pain and sciatica. There also are several possible pathogeneses for these pathologic changes, although the proofs still are inconclusive or lacking. A better understanding of the relationships between vibration and spinal disorders in the near future will help us to prevent the occurrence of some of the problems causing pain and disability.

Back Pain↗