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Biomedical subjects

I A Stokes

Publications and source records attributed to I A Stokes.

71 records · Page 4Linked to original sources
PubMed1987

Segmental motion and instability.

Seventy-eight patients were categorized as having degenerative instability in the lumbar spine, based on clinical symptoms and radiologic signs. Biplanar radiography was used to measure the angular and translational intersegmental motion components of flexion and extension of the lumbar spine. A comparison was made between this measured motion, the clinical symptoms, response to facet joint injection of anesthetic, and radiologic appearance of disc space and facets. The magnitude of the flexion motion and the magnitude of the anteroposterior (AP) shear motion accompanying the flexion was slightly less at symptomatic compared with nonsymptomatic levels. In most patients the AP shear motion at all levels was less than 3 mm (maximum 7 mm). The amount of forward shear motion correlated positively with the amount of flexion motion (r = 0.3). The shear-flexion ratio was significantly reduced at symptomatic levels of patients. Although this group of patients, taken as a whole, showed a tendency toward abnormal intersegmental motion of the lumbar spine, it was found that flexion-extension biplanar radiography was not useful in the diagnosis of lumbar instability.

Adult↗
PubMed1987

Trunk extensor EMG-torque relationship.

The integrated surface electromyogram (IEMG) of the lumbar erectores spinae and the torque generated were simultaneously recorded from 27 healthy subjects in the standing posture while they pulled isometrically against resistance provided by a harness around the shoulders. The IEMG-torque ratio (efficiency of electrical activity, or EEA) was used to characterize each subject. Individual recordings showed evidence of nonlinearity of the IEMG-torque relationship in that a statistically better fit to experimental recordings was obtained by using two straight lines with a breakpoint between them. However, with repeated testing, the gradients of these two lines were more variable than the slope of the single straight line fitted to the entire recording. The slope of the best fit line (EEA) was less for recordings made during torque decrease than for increasing-torque recordings. This also showed as a "hysteresis" pattern in the recordings. The coefficient of variability (within subjects) of the EEA was greater in day-to-day testing (24%) than with repeated pulls at the same testing session (14%). This was similar to variability of the maximum generated torque. About 25% of the variability between subjects was found to be due to anthropometric differences. The residual variability of the relationship would limit the accuracy of IEMG as a measure of muscular effort under changing torque conditions. However, the EEA may be useful for characterizing muscle performance, especially when maximum effort cannot be achieved.

Adult↗
PubMed1987

Measurement of the shape of the surface of the back in patients with scoliosis. The standing and forward-bending positions.

In order to determine if the configuration of the trunk is altered when a patient changes from an upright to a forward-bending position, the shape of the surface of the back of fifty-six patients who had adolescent idiopathic scoliosis was recorded, by means of Raster stereophotography, with each patient in three postures: standing erect, bending forward with the hands between the knees (forward bend 1), and bending forward with the hands touching the toes (forward bend 2). The effect of placing one foot on a block to produce a limb-length difference was also studied in the standing position (thirty patients) and in the forward-bending position (eighteen patients). The degree of rotation of the surface of the back and of kyphosis and lordosis of the surface of the trunk was measured from sections in the sagittal plane that were plotted from the computerized measurements of the surface of the back. Qualitatively similar rotation of the surface of the back was found in both the standing position and the forward-bending position. When the patient was in the forward-bending position, the degree of rotation of the surface of the back was minimally changed in the thoracic region but increased in the lumbar region. The amount of rotation of the surface of the back was similar in both forward bending with the hands to the knees and forward bending with the hands to the toes.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMed1986

Measurement of axial rotation of vertebrae in scoliosis.

The authors report a radiographic method for measuring the axial rotation of vertebrae in degrees and its use in 99 patients with adolescent idiopathic scoliosis. The offset of the pedicle images from the vertebral body center and a "depth" estimate measured radiographically in a population of patients with scoliosis permitted calculation of axial rotation by means of a simple mathematical formula. It was found that measurements of vertebral rotation can be made clinically from single-plane radiographs with a standard deviation of 3.6 degrees (95% confidence limit +/- 7.1 degrees) based on a study of known rotations of a radiographic phantom, and with a standard deviation of 2.44 degrees (95% confidence limit +/- 4.8 degrees) based on comparisons with three-dimensional measurements of the orientation of each vertebra derived from low-dose stereo films of a group of patients. Measurements from clinical films are unlikely to be made more accurately than this, because of inherent geometric constraints.

Adolescent↗
PubMed1984

The biomechanics of scoliosis.

A review of the epidemiology of scoliosis reveals that it is costly in human suffering and health care resources. The terminology is defined and classifications explained. The full geometric description of scoliosis includes the three-dimensional description of the vertebral column, as well as the rib cage. Stereoradiographic and stereophotogrammetric (Raster and Moire) techniques are introduced. The coupling in a kinematic sense between, for example, lateral bend and rotation is compared to the orientation coupling in scoliosis. Genetic, biochemical, hormonal, neurological, and mechanical factors do not as yet explain the etiology. Column buckling models do not incorporate coupling, especially that occurring in scoliosis and thus do not improve our understanding of the deformity or its progression.

Adolescent↗
PubMed1979

Tension and creep phenomena in peripheral nerve.

Tension introduced into peripheral nerves during their surgical repair may reduce the success of this procedure. Two mechanical factors are important; the tension required to effect a repair, and the rate at which this tension changes after surgery. These two factors have been investigated in the rat sciatic nerve. The results show an increasing resistance to elongation of the nerves with increasing tension. Under a constant elongation the tension in the nerves reduces by about 30 per cent in the first 10 minutes and by a small amount in the following 20 minutes.

Animals↗
PubMed1975

The neuropathic ulcer and loads on the foot in diabetic patients.

Normal subjects and diabetic patients with and without food ulcers have been studied using an apparatus which measures the loads on the foot during walking. Diabetic patients have alterations in loading which show as a lateral shift of the highest maximum load on the forefoot and a decrease in the load carried by the toes. There is a significant progression of these changes between normal subjects, diabetic patients with deformity of the foot but no ulcer, and diabetic patients with foot ulcers. All the patients with ulcers exerted maximum loads at the site of the ulcer.

Adolescent↗
PubMedDate not supplied

Biomechanical testing as an aid to decision making in low-back pain patients.

Frequently, the diagnosis of disease of the low back is a difficult matter due to the multitude of factors affecting the patient's symptoms. In this report an attempt is made to use biomechanical testing to objectify certain aspects of the diagnostic process. Our philosophy is that a biomechanical assessment is one of the disciplines that should be brought to bear on the low-back pain patient. A group of biomechanical tests has been developed by adding quantitative measurement techniques to certain standard clinical maneuvers: muscle testing, range of motion testing, and straight leg raising testing. Moire fringe topography is employed for studying posture. Results of application of these techniques to 117 patients and 10 controls indicate potential utility in the method for epidemiologic and clinical research.

Back Pain↗
PubMedDate not supplied

Influence of the hamstring muscles on lumbar spine curvature in sitting.

The hamstring muscles can restrict hip flexion, especially when the knees are extended. It was hypothesized that individuals with short or tight hamstrings would have abnormal tilting of the pelvis in some seated postures, with greater flattening or reversal of the lumbar lordosis. Healthy adults were studied. A toe-touch test was used to measure range of hip flexion. Lumbar spine curvature was measured in standing, in sitting with the knees flexed, and in sitting with knees partially extended. Large individual variations in range of hip flexion were found. Persons with a small range had the most pronounced change in spine curvature in the second seated posture. It is concluded that attention should be given to this effect of the hamstrings on the lumbar spine when workplaces are designed.

Female↗
PubMedDate not supplied

1980 Volvo award in clinical sciences. Assessment of patients with low-back pain by biplanar radiographic measurement of intervertebral motion.

Abnormalities of intervertebral joint motion including hypermobility, reduced mobility, torsional abnormality, and displacement of the center of rotation have been associated with degenerative change. However, measurement of these signs in plane X-ray films is handicapped by the three-dimensional motion and geometry of the spine. This study aimed to relate three-dimensional motion of the joints to their pathological state. We have used biplanar radiography to measure intervertebral motion during voluntary movements by patients with low back pain. Primary (or intentional) and coupled motions were measured by a refined technique, along with disc shear and facet joint motion. Abnormalities were found, especially in the "coupled" motions which were related to narrowed disc space, and to proximity to previous fusions. There was asymmetry of motion specific to joints with herniated nucleus pulposus.

Back Pain↗
PubMedDate not supplied

Forces under the hallux valgus foot before and after surgery.

Abnormalities in the hallux valgus foot and changes after surgery were investigated by measuring the distribuiion of load on the foot in walking. Hallux valgus was associated with reduced load imposed on the toes, and on the medial side of the forefoot, compared with a large sample of healthy feet. Abnormalities correlated with the degree of the deformity. Both Keller's operation and a wedge displacement osteotomy of the first metatarsal not only failed to restore normal loading but increased the abnormalities of loading seen preoperatively. A large decrease in the angle between first and second metatarsals as a result of surgery minimized this increase. A silastic arthroplasty did not carry high loads when used to treat hallux valgus, but near normal loads were imposed on it when used for hallux rigidus. Considerable variability was found in the loading distribution on the healthy feet. The distribution between first and second metatarsal heads was partially dependent upon their protrusions, relative to the direction of walking. The changes in the relationships between the loadings on the forefoot and skeletal shape in response to surgical operations are important for our understanding of treatment of the hallux valgus foot.

Adolescent↗