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Biomedical subjects

D G Wilder

Publications and source records attributed to D G Wilder.

At least 37 records · Page 2Linked to original sources
PubMed1994

L4-5 isthmic spondylolisthesis. A biomechanical analysis comparing stability in L4-5 and L5-S1 isthmic spondylolisthesis.

The authors have previously reported that the L4-5 isthmic spondylolisthesis lesion often progresses more than the L5-S1 lesion in adult patients. This biomechanical study compares the in vitro stability of the L4-5 isthmic spondylolisthesis lesion compared with the L5-S1 isthmic lesion. The authors also analyzed the role of the L5 iliolumbar ligament as a contributing factor to stability. Six fresh frozen human cadaveric specimens (L4 to the sacrum including the iliolumbar ligamentous complex) were tested by applying 10 Nm flexion-extension moments. Sagittal plane motion was measured with the specimens intact and after sequential transection of the pars interarticulares at L4 and L5 and finally with the iliolumbar ligaments cut at L5-S1. L4-5 and L5-S1 both showed significant increases in rotation with the pars defect compared with normal (L4-5 = +2.0, L5-S1 = +3.2 degrees). Decreased translation of L5-S1 occurred with pars defect at this level. There were no significant differences at the L5-S1 level after sectioning of the iliolumbar ligament. Calculating the percentage difference from normal, L4-5 with a pars defect exhibited significantly greater relative motion compared with L5-S1 with the same defect; 12% more rotation, 33% more shear, and 43% more axial translation. The iliolumbar ligament did not appear to contribute to these differences because there was no significant change in the L5-S1 kinematics after its transection. These results support the hypothesis that L4-5 pars defects are more unstable than L5-S1 lesions. The iliolumbar ligament could not be implicated as the major contributing factor in these differences.

Biomechanical Phenomena↗
PubMed1994

The effect of vibration on back discomfort and serum levels of von Willebrand factor antigen: a preliminary communication.

The von Willebrand factor (vWf) is a complex protein whose release is a marker for endothelial damage; serum levels of its antigen (vWFAg) can be used as a marker for such changes. We measured the levels of back discomfort and vWFAg in 11 subjects following 25-min periods of (1) lying down, (2) sitting upright, (3) vibrating whilst sitting and (4) sitting upright. Back discomfort appeared and vWf levels were significantly increased following sitting upright, compared with lying flat, and increased further following vibration. They fell thereafter with a period of sitting still upright. These results demonstrate that vibration has a significant effect in increasing back discomfort and the serum levels of vWFAg, and it is possible that vibration may induce vascular damage within the spine.

Adult↗
PubMed1993

The biomechanics of vibration and low back pain.

This work is a review of the mechanical factors related to low back pain production in a vibration environment. The sitting posture is an extreme orientation for the lumbar intervertebral disc that 1) increases its internal pressure, 2) increases its anteroposterior shear flexibility, while: 3) decreasing its resistance to buckling instability and 4) stressing the posterior region of the disc. Vibration is an additional mechanical stressor. Several studies suggest that the following preventive measures be taken to reduce the risk of low back pain due to driving: 1) minimize the vibration reaching the driver, 2) avoid lifting or bending immediately following driving, and 3) walk around for a few minutes following driving.

Automobile Driving↗
PubMed1991

Whole-body vibration exposure in subway cars and review of adverse health effects.

New York City Transit Authority subway operators have a high prevalence of back problems. To evaluate a possible dose-response relationship for whole-body vibration, we studied subway car vibrations measured and analyzed according to the International Standard Organization 2631 and Verein Deutscher Ingenieure 2057 standards. Vibration transducers in triaxial orientation were mounted in a disc pad directly on the subway operator's seat. The relatively high lateral and vertical accelerations, primarily the combined effects, may all contribute to the high rate of musculoskeletal complaints, especially of the lower back. Other factors aggravating whole-body vibrations include primitive ergonomic cab and seat design, forced body posture, high noise levels, and organizational work stress.

Back Pain↗
PubMed1989

Trunk muscle electromyography and whole body vibration.

By measuring the electromyographic (EMG) activity of the paraspinal muscles, we have estimated the average and peak-to-peak torque imposed on the spine during whole body vibration. Six subjects had surface electrodes placed on their erector spinae muscles at the L3 level. The EMG-torque relationship was estimated by having each subject perform isometric horizontal pulls in an upright seated posture. The subject was then vibrated vertically and sinusoidally in a controlled, flexed, slightly lordotic seated posture, in 1 Hz increments from 3 to 10 Hz at a 0.1 g RMS seat acceleration level. Between vibration readings taken at each frequency, a static reading was also taken with the subject maintaining the same posture. The entire vibration-static 3-10 Hz test was repeated for reliability purposes. Specialized digital signal processing techniques were developed for the EMG signals to enhance the measured cyclic muscle activity and to allow automatic measurement of the time relationship between the mechanical displacement and the estimated torque. We found significantly more average and peak-to-peak estimated torque at almost all frequencies for vibration vs static sitting.

Acceleration↗
PubMed1989

Quantitative measures of neurological function in chronic neuromuscular diseases and ataxia.

Interexaminer and intraexaminer reliability were determined for 30 quantitative measures of neurological function, including sensory threshold, tendon reflexes, maximum isometric strength, and timed tests and coded ratings of functional ability, in patients with Charcot-Marie-Tooth disease (n = 30), idiopathic polyneuropathy (n = 16) and spinocerebellar degeneration (n = 30). Five of 6 sensory and reflex measures had interexaminer reliability greater than 0.80 when the neurologists' examinations were 1 h apart; 2 of 7 achieved this level when the examinations were separated by 1 month. Interexaminer reliability between physical therapists was greater than 0.80 for 19 of 20 measures of strength and functional ability. Intraexaminer reliability coefficients greater than 0.80 were found for 13 of 24 sensory and reflex measures, 28 of 30 isometric strength measures, 24 of 30 timed tests and 5 of 6 coded ratings of functional ability. Electro-oculography, oral diadochokinetic syllable rates, hand and foot accelerometry, and tracings of sine and square waves were examined as quantitative indices of ataxia for patients with spinocerebellar degeneration. Of 11 measures of ataxia, only the oral diadochokinetic syllable rate test had acceptable reliability.

Activities of Daily Living↗
PubMed1989

Determinants of vocational disability in patients with low back pain.

Eighty-seven unemployed subjects with low back pain were recruited from an orthopedic back pain clinic and were given a battery of physical and psychologic tests. Subjects were contacted six months later to determine their current compensation status and whether they had returned to work. Age, length of time out of work, how much they had lifted in their previous job, the number of weeks they had been compensated, current activity levels, leg pain, and various psychologic factors significantly differentiated those who worked from those who did not. Physical examination findings and testing of the ability to lift were not significantly related to return to work. It is suggested that demographic, job-related, and psychologic factors should be emphasized, rather than only physical capacity, in the evaluation of vocational potential and the assessment of disability in patients with low back pain.

Adult↗
PubMed1989

The balance point of the intervertebral motion segment: an experimental study.

A loading or "balance" point was sought that could serve as a functional reference for mechanically testing spinal motion segments. This point is located above the in-vitro motion segment where, when an axial compressive load is applied, the segment exhibits minimal coupled rotation. The balance point is a reliable indicator of the mechanical characteristics of the segment. Segments exhibited increasing rotation as axial compressive loads were applied further and further away from the balance point. The location of the balance point was significantly affected by sustained static or cyclic flexion-compression loading and by brief flexion-compression overloads.

Biomechanical Phenomena↗
PubMed1988

The biomechanics of lumbar disc herniation and the effect of overload and instability.

A multipart study has been performed to provide a mechanical explanation for the epidemiologic association between sitting in static (e.g., factory or office) or vibration (e.g., car or truck driving) environments and acute herniated lumbar discs. It was shown that a 1 h exposure to sitting environments caused significant changes in the mechanical properties of the lumbar intervertebral disc. During many of the latter tests, specimens were unstable (exhibited by a sudden, large flexion and/or lateral bend rotation response to an axially applied load). This showed that a motion segment in the lumbar spine could suddenly buckle and apply a tensile impact loading to the posterolateral region of the disc. We also demonstrated that a combined lateral bend, flexion, and axial rotation vibration loading could cause tracking tears proceeding from the nucleus through the posterolateral region of the anulus. It suggests that a mechanism for disc herniation is mechanical changes leading to instability of the motion segment. These experiments complete the argument that lumbar disc herniations can be a direct mechanical consequence of prolonged sitting in static or vibration environments.

Aged↗
PubMed1987

Internal displacement distribution from in vitro loading of human thoracic and lumbar spinal motion segments: experimental results and theoretical predictions.

Small metal markers are implanted within intervertebral discs and their displacements in response to a complex load (flexion, compression, and anterior shear) are measured radiographically. These are contrasted to the displacements predicted by a finite element model (FEM) that uses 20 constant-strain triangular elements and is based upon a linear elastic isotropic material. The central portion of the disc (nucleus pulposus) moves posteriorly and oppositely to the FEM prediction. The anterior and posterior portions of the disc agree more closely with the FEM than the central portions of the disc. In general, the FEM predicts much more accurately the up-down displacement components than it does the anterior-posterior components. The measured displacements provide a new class of information concerning the function of the interior of the disc, and also provide a new basis for validation of FEMs that attempt to mimic real intervertebral disc behavior. Implications for understanding of disc function and pathology are discussed.

Aging↗
PubMed1987

The response of the seated human to sinusoidal vibration and impact.

Low back pain has been shown to occur more frequently among vehicle drivers than in representative control groups. Thus the response of the human to vibration and impact is of interest. This study investigated the response of the spine to both impact and sinusoidal excitation in either a relaxed or erect seated posture. The sinusoidal testing apparatus used was a resonating system consisting of two parallel wooden beams, simply supported, and the impact testing apparatus a bearing-guided, spring-suspended platform, struck from below. Ten subjects (5 males, 5 females) were evaluated using both methods. Transfer functions were compared at 2-4 Hz, 4-8 Hz and 8-16 Hz intervals using a sign test. Although in 24 comparisons of either test method (vibration or impact) or posture (erect or relaxed) where eleven showed differences significant at the p less than .05 level, only 2 out of 24 comparisons were the differences distinct enough to be significant (at the p less than .01 level). Both of these latter differences were due to test method while the subjects were sitting erect. In those instances where there were no significant differences due to test method, the impact method may be a viable replacement for the vibration test method. Where the levels of significance are higher (p less than .01 or p less than .05), further study of the magnitude of the differences is indicated and may reveal further insight into the seated individual as a system.

Adolescent↗
PubMed1985

The relationship between anthropometric, postural, muscular, and mobility characteristics of males ages 18-55.

Three hundred twenty-one males, ages 18-55, had standardized tests to determine height, weight, Davenport Index, leg length inequality, determination of flexion and extension torques, flexion/extension balance, range of motion, straight leg raising, and lumbar lordosis. A total of 106 (33.0%) had never experienced low-back symptoms; 144 (44.9%) had or were having moderate low-back pain (LBP); and 71 (22.1%) had or were having severe low-back symptoms. These three subgroups showed no significant differences in height, weight, Davenport Index, lumbar lordosis, or leg length inequalities. LBP patients had less flexor and extensor strength and were flexor overpowered, had diminished range of motion for spinal extension and axial rotation (P = 0.003, P = 0.0005), and diminished straight leg raising capacity (P = 0.04). A multivariate correlation matrix demonstrated no typical pattern of associated abnormalities except a diminished spinal range of motion in one plane was associated with the anticipated diminishment in all other planes of motion, and often with greater restrictions of straight leg raising tests.

Adolescent↗
PubMed1984

Spine radiographs in patients with low-back pain. An epidemiological study in men.

A cohort of 321 men between the ages of eighteen and fifty-five was randomly selected from a group of 1221 men who had been surveyed by a questionnaire. They then had radiographs made of the lumbar spine. Of the 292 subjects fulfilling the criteria for inclusion in the study, ninety-six (32.9 per cent) had never had low-back pain, 134 (45.9 per cent) had had or were having moderate low-back pain, and sixty-two (21.2 per cent) had had or were having severe low-back pain. In the three groups there was a similar frequency of transitional vertebrae, Schmorl's nodes, the disc vacuum sign, narrowing of the disc space between the third and fourth lumbar and the fifth lumbar and first sacral vertebrae, and claw spurs. When there were traction spurs or disc-space narrowing, or both, between the fourth and fifth lumbar vertebrae, an increased incidence of severe low-back pain was evident. There also was a significant association of these two radiographic findings with symptoms (pain, weakness, and numbness) in the lower limbs. The measured lumbar lordosis, the length of the transverse process of the fourth lumbar vertebra, and the relationship between the fourth and fifth lumbar vertebral bodies with reference to the intercristal line had no association with the low-back pain. Increased lumbar lordosis had a significant association with decreased disc-space height and wedging deformity of the disc between the fourth and fifth lumbar vertebrae.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗