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Biomedical subjects

R Ortengren

Publications and source records attributed to R Ortengren.

At least 37 records · Page 2Linked to original sources
PubMed1979

Vestibulospinal reflex activity in patients with adolescent idiopathic scoliosis. Postural effects during caloric labyrinthine stimulation recorded by stabilometry.

Postural sway has been quantified with stabilometry during caloric labyrinthine stimulation in an erect posture in 49 patients, aged 10--16 years, with adolescent idiopathic scoliosis. Thirty-two healthy children of the same age constituted a control group. The scoliotic patients tended to have an increased postural sway during labyrinthine stimulation on the convex side compared to the effects on the concave side. Significant differences were observed when left and right scoliotic patients were compared with the controls. The results can be explained by an asymmetric sensitivity in the labyrinth or by a dysfunction in the postural control mechanisms at the brain stem level.

Adolescent↗
PubMed1978

Postural equilibrium in adolescent idiopathic scoliosis.

Postural equilibrium has been quantified by stabilometry in 57 patients with adolescent idiopathic scoliosis aged 10-16 years. Treatment was required in 39 cases whereof 18 were placed under observation only. The control group comprised 32 healthy children of the same age. An experimental design was made to vary the degree of difficulty of upright standing in four different test situations. The postural sway was analysed in the sagittal and lateral direction as well as in the area of total sway. The scoliotic patients had a significantly poorer postural control compared with the healthy children in all the tests. The difference was most pronounced in tests in which the proprioceptive functions were most important for maintaining the postural equilibrium. The left convex patients had quantitatively more pronounced reactions than the right convex patients. Patients with small curvatures, i.e., patients placed under observation only, had significantly increased postural sway compared with patients with more severe deformity. This fact, together with findings in patients with double primary curvatures, and the results of the study of brace effects, indirectly indicate the possibility of a postural disequilibrium as a contributory causative factor in adolescent idiopathic scoliosis.

Adolescent↗
PubMed1977

Quantitative electromyographic studies of back muscle activity relatated to posture and loading.

The myoelectric activity of some of the posterior muscles of the back was studied quantitatively using signal amplitude estimation and power spectrum analysis. Surface electrodes were placed on both sides of the trunk at T4, T8, L1, L3, and L5 levels. Four different angles of forward flexion were studied during external loading of the spine with 200 N. At 30 degrees of forward flexion studies were made when the load was increased from 0 to 300 N. Asymmetric loading was studied with the trunk erect, in lateral flexion, and in rotation. The myoelectric activity increased when the angle of flexion increased and when the external load was increaed at a fixed angle of flexion. During asymmetric loading, comparatively higher activity was found on the contralateral side in the lumbar region and on the ipsilateral side in the thoracic region. The magnitude of the power spectrum changes correlated well with the amplitude of the myoelectric signal. Spectral changes increased when the signal amplitude increased, indicating localized muscle fatigue.

Adult↗
PubMed1975

The sitting posture: an electromyographic and discometric study.

The disc pressure of the third lumbar disc and the myoelectric activity of several muscles of the back were measured. Three standing and nine unsupported sitting positions were studied as well as eight support parameters and six sedentary tasks. 1. Myoelectric activity is about the same in standing and in relaxed unsupported sitting. In the unsupported sitting positions the highest level of activity is found in anterior sitting and the lowest in posterior sitting. In the muscles of the cervical and lumbar regions the activity is always lower than in the muscles of the thoracic region. The disc pressure is considerably higher in unsupported sitting than in standing. In the unsupported sitting positions the highest disc pressure is found in anterior sitting and the lowest in sitting straight. 2. Both the myoelectric activity and the disc pressure decrease when the back is supported. Of the support parameters, the backrest inclination is the most important, myoelectric activity and disc pressure both decreasing with an increase in inclination. The disc pressure is considerably reduced also when the lumbar support is increased and when armrests are used. 3. Myoelectric activity and disc pressure are both comparatively low in writing, higher in typing, and still higher in lifting. In the car driver's seat the disc pressure increases both when the gear is shifted and when the clutch pedal is depressed. When the gear is shifted, there is also an increase in myoelectric activity.

Adult↗
PubMedDate not supplied

Intradiskal pressure, intra-abdominal pressure and myoelectric back muscle activity related to posture and loading.

Intradiskal pressures, intra-abdominal pressures and myoelectric activities of posterior back muscles have been measured simultaneously in vivo in 4 subjects. Five different angles of forward flexion were studied while externally loading the trunk with 200N. At 30 degrees of forward flexion studies were made when the load was increased from 0 to 300N. Asymmetric loading was studied with the trunk erect, in lateral flexion and in rotation. The measurement parameter values all increased when the angle of flexion increased and when the external load was increased at a fixed angle of flexion. Linear relationships were established. During asymmetric loading pressure values and the myoelectric activity increased. The increase in myoelectric activity was comparatively greater on the contralateral side of the lumbar region and on the ipsilateral side of the thoracic region. The disk pressure, the intra-abdominal pressure, and the FRA-values were higher throughout when the trunk was loaded in rotation, than in lateral flexion.

Abdomen↗
PubMedDate not supplied

The influence of backrest inclination and lumbar support on lumbar lordosis.

The influence of backrest inclination and lumbar support on the shape of the lumbar spine in sitting positions has been studied radiographically on 38 healthy subjects. Four angles of backrest inclination and four different sizes of lumbar support were studied. In addition, the lumbar support was placed at three different lumbar levels. When sitting down from a standing position, the pelvis rotates and the lumbar lordosis decreases. Increases in the backrest-seat angle had only minor effect on the lumbar lordosis. A lumbar support, on the other hand, had a significant influence: the lordosis increased with increasing support. The location of the lumbar support with respect to the level of the spine did not significantly influence the measured angles.

Adult↗