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Biomedical subjects

A B Schultz

Publications and source records attributed to A B Schultz.

At least 91 records · Page 5Linked to original sources
PubMed1983

Posterior element loads in lumbar motion segments.

This report concerns the manner in which the intervertebral disc and the posterior elements share loads placed on a lumbar motion segment. A two-dimensional biomechanical model was used to examine this. The model incorporated two rigid bodies to represent the vertebrae and six elastic springs to represent the tissues of the intervertebral disc and the posterior elements. Compression loads were resisted almost totally by the model intervertebral disc, but both the intervertebral disc and the posterior elements contributed substantially to resisting anteroposterior shear and flexion-extension loads. Motion segment morphology was a major determinant of load-sharing in model response to anteroposterior shear.

Intervertebral Disc↗
PubMed1983

Intervertebral disc pressures during traction.

Pressures in the third lumbar discs were measured in vivo during active and passive traction. During active traction an increase in pressure was always recorded, with larger increases corresponding to larger traction forces. During passive traction the pressure remained close to the resting pressure; sometimes slight increases were recorded, sometimes slight decreases. It is concluded that when traction is applied so that the back muscles contract, then disc pressures will increase.

Adult↗
PubMed1982

Analysis and measurement of lumbar trunk loads in tasks involving bends and twists.

Ten subjects performed isometric weight-holding and force-resisting work tasks while standing upright, both with and without a twist of the trunk; with the trunk bent laterally; and in postures involving combinations of bending and twisting. The lumbar trunk muscle contraction forces and the lumbar spine compression and shear forces imposed by these tasks were predicted using a biomechanical model. Myoelectric activity was recorded quantitatively at eight locations over the back muscles and at four locations over the abdominal wall muscles. Correlation coefficients from 0.67 to 0.88 were found between the predicted muscle contraction forces and the measured myoelectric activities when the predictions were made so as to minimize muscle contraction force per unit area. Trunk twisting and lateral bending were found to load the spine and trunk muscles less than trunk flexion or holding of weights in front of the body.

Adult↗
PubMed1977

Harrington rod distraction instrumentation: its effect on vertebral rotation and thoracic compensation.

The effects of Harrington rod distraction instrumentation on vertebral rotation and thoracic decompensation were investigated radiographically both pre- and post-operatively. A method for semiquantitatively evaluating thoracic decompensation is introduced to serve as an adjunct to the evaluation of spinal deformity. Although little derotation of the vertebrae occurs with lateral correction, thoracic decompensation should be significantly improved.

Adolescent↗
PubMed1976

Roentgenographic evaluation of vertebral rotation.

To examine the accuracy of vertebral rotation determinations made from roentgenographic pedicle-shadow offset measurements, roentgenograms were made of fifteen cadaver vertebrae with different sagittal and frontal inclinations and longitudinal axis rotations ranging from 15 degrees left to 45 degrees right. It was found that significant uncertainties arise when vertebral rotation is evaluated from measurements of pedicle-shadow offset: true and apparent offsets in a single vertebra differ markedly; vertebrae from different spines have different offsets for the same degree of rotation and the same inclinations; and changes in the sagittal and frontal inclinations of a single vertebra alter its offset in the same manner as changes in rotation. From these results, it seems unlikely that precise measurements of rotation changes in spines with mild or moderate scolioses, for example, can be made from anteroposterior roentgenograms.

Biomechanical Phenomena↗
PubMed1976

Milwaukee brace correction of idiopathic scoliosis. A biomechanical analysis and a restrospective study.

We analyzed the biomechanics of Milwaukee brace treatment of idiopathic scoliotic patients through simulation in five computer-constructed model spines. The contributions to correction of each component of the brace were examined in these model spines, and some of the mechanical principles that determine the outcome of brace treatment were studied. The validity of the stimulation findings was then tested by a retrospective analysis. Simulation was used to predict the outcome of milwaukee brace treatment in sixty-eight patients. In 81 per cent of these patients, the actual outcome agreed with the prediction. The study suggests that careful adherence to mechanical principles in the use of a Milwaukee brace will result in successful treatment of more patients.

Adolescent↗