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Biomedical subjects

E Bahniuk

Publications and source records attributed to E Bahniuk.

17 recordsLinked to original sources
PubMed1989

Age-dependent changes in the shear wave propagation through human skin.

We studied the potential use of the in vivo frequency response of human volar forearm skin as a means for evaluating skin age. The velocity and damping length of waves on the skin surface were correlated with chronological age. One hundred and fifty subjects from 1 to 95 years of age were studied. For the frequency spectrum from 800 to 2000 Hz, there was a linear correlation between the velocity of propagation and age. At 2000 Hz, the y intercept was 11.4 m/second and the slope was 0.245 m/second/year, r = 0.5500, p less than 1 x 10(-7). There was no correlation of velocity with sex, skin color, obesity, sun exposure, physical activity, or inpatient status.

Adolescent↗
PubMed1988

Some viscoplastic characteristics of bovine and human cortical bone.

Multiple cycle tensile creep tests were performed on human and bovine cortical bone specimens. The tests enabled total strain to be decomposed into elastic, linear viscoelastic, creep and permanent plastic components. The results indicate that a stress threshold exists; above which time dependent effects dominate material response and below which the behavior is primarily linear viscoelastic, with time effects playing only a secondary role. A constant stress above the threshold produces a constant steady state creep rate, with the magnitude of the creep rate being an exponential function of the stress magnitude. Additionally, it was found that a major portion of the inelastic strain is always recovered on unloading and that the accumulation of creep strain increases the material compliance on subsequent loadings below the threshold. These two factors suggest that a damage mechanism is responsible for the nonlinear behavior.

Adult↗
PubMed1986

Localization of foreign bodies in the spinal canal by computer-assisted biplanar digitizer.

This study is a report of the use of a computer-assisted biplane digitizer to locate shotgun pellets within the spinal canal in an incompletely paralyzed patient. It was necessary to determine if one or more shotgun pellets were located within the spinal cord of the patient. Because of the profusion of pellets it was not possible to determine which, if any, of the pellets were in the spinal canal by routine roentgenograms. The problem of determining the location of each pellet with respect to the spinal cord was resolved by the use of biplane radiography in conjunction with an x-ray digitizer and a computer program. This report presents the method for localizing foreign bodies and discusses the results of the procedure. It was concluded that the described method successfully located the position of pellets with respect to the spinal column and cord. This method may be useful for locating metallic fragments that have to be surgically removed in other patients sustaining spinal cord injury secondary to single missile wounds.

Adult↗
PubMed1986

The effects of the tibial femoral angle and of disuse on the strength of canine anterior cruciate ligaments.

Two series of tests were undertaken on dog legs. One series showed that the apparent distraction strength of dog cruciate ligaments depends on the relative angle of the tibia and femur during distraction. The second series documented bone resorption due to disuse. This series showed that mechanical strength was reduced and that there was a reduction in bone collagen due to disuse.

Animals↗
PubMed1985

Anisotropic yield behavior of bone under combined axial force and torque.

In this study the yield behavior of cortical bone was determined under combined loading conditions involving tension, compression and torsion. The axis of each test sample coincided with the long bone axis. To minimize viscoelastic behavior, tests were conducted using an effective strain rate in the range of 0.01-0.06 s-1. Experimental yield loci for bovine and human cortical bone were determined using a strain offset technique to determine the 'common yield point' for combined loading. Several failure criteria which have been used for composite materials were examined for applicability to the experimental results. Data were obtained for bovine and human tibial and femoral bone. The Tsai-Wu criterion was in best agreement to the test data, although Hill's criterion could describe the individual compression-torsion or tension-torsion regimes with good accuracy.

Animals↗
PubMed1983

Biplane radiographic measurements of reversible displacement (including clinical loosening) and migration of total joint replacements.

UNLABELLED: We studied nineteen total knee replacements and thirty-three total hip replacements with simultaneous biplane radiography to measure in vivo micromotion at the cement-bone interface. Spherical cobalt-chromium markers were embedded in the cement and cortical bone. Relative motion of the cement-markers was measured with respect to the markers in the cortical bone. Reversible displacement (relative motion during a change from non-weight-bearing to weight-bearing) and migration (relative motion over time from one non-weight-bearing study to another) were calculated. The resolution of the measuring system was 0.2 millimeter. The range for symptomatic reversible displacement was 0.4 to 4.5 millimeters, while that for asymptomatic reversible displacement was 0.3 to 1.9 millimeters. All reversible displacement of less than 0.4 millimeter was asymptomatic. Migration of as much as 2.1 millimeters occurred without concomitant reversible displacement. All radiolucent lines correlated with measured reversible displacement. Half of the patients who were evaluated two weeks postoperatively had measurable reversible displacement. CLINICAL RELEVANCE: Our findings were based on a small series from a selected population. The incidence of measured reversible displacement (75 per cent) was based on in vivo techniques and included symptomatic and asymptomatic reversible displacement; therefore, it was higher than the incidence of clinical loosening (9.6 per cent in our series). Simultaneous biplane radiography may become an important adjunct in the postoperative management of patients with a total joint replacement.

Follow-Up Studies↗
PubMed1982

A comparison of convergent and bi-plane X-ray photogrammetry systems used to detect total joint loosening.

X-ray photogrammetry is an accurate method of measuring structural displacements within the musculoskeletal system. Total joint implant alignment, migration and loosening are important clinical parameters which can be measured by X-ray photogrammetry. The purpose of this paper is to compare two different X-ray photogrammetry systems which are being used to study total joint parameters. The Seattle system uses a convergent geometry and the Cleveland system a bi-plane geometry. The accuracy of the two systems was compared by individually measuring the relative motion produced in an articulated plastic model. The model was designed to simulate the relative motion which can take place between the bone and a loose implant. The displacements of the model components were determined physically and photogrammetrically, and the error in the measurements was calculated for several conditions. Both systems measured relative component motion in the model with a root mean square error of 0.1 mm or less. In clinical use stainless steel markers are implanted in human subjects, and both systems measure distances with a r.m.s. error of 0.2 mm or less. The ease of usage, efficiency and flexibility of the two systems based on actual clinical experience reveals strengths and weaknesses in each which should be recognized when selecting a particular system.

Ankle Joint↗
PubMed1982

Isotopic evidence for resorption of soft tissues and bone in immobilized dogs.

UNLABELLED: Various experimental methods for producing bone and ligament atrophy have yielded contradictory results. These methods include denervation, immobilization (both internal and external), and disarticulation. We studied a model of internal skeletal fixation for twelve weeks in dogs that were chronically prelabeled with 3H-tetracycline, 45Ca, and 3H-proline. Bone resorption was analyzed by the loss of 3H-tetracycline, and bone and soft-tissue mass were analyzed by the radiochemical and chemical analysis of calcium and collagen. The strength of the anterior cruciate ligament was studied in tension to failure when a fast rate of deformation was applied. Failure of the femur-ligament-tibia complex occurred through the insertion of the ligament into the tibia for both the experimental and the control limbs. Loss of collagen was greater in the tibia and femur than in the lateral meniscus and anterior cruciate ligament, and correlated with a mechanical failure via bone. No evidence for collagen replacement in atrophied tissues was found, but one-half of the resorbed calcium was conserved. The marked loss of 3H-tetracycline indicated that bone atrophy was the result of increased resorption of bone rather than decreased bone formation. CLINICAL RELEVANCE: We have demonstrated significant atrophy of the soft tissues (lateral meniscus and anterior cruciate ligament) as well as of bone in immobilized joints of dogs. It is likely that the decrease in strength of the bone-ligament-bone complex is related to this atrophy of soft tissues and bone around the joint.

Animals↗
PubMed1982

Ski standards developed by the American Society for Testing and Materials.

Although it is not a glamorous or financially rewarding activity, the work of writing standards has been of benefit to the entire skiing community. The benefit or contribution of any particular standard varies, but the overall benefit of standards is real. The sport is safer and the responsibilities of various segments are clearer because of the efforts of the standard writers.

Equipment Design↗
PubMed1980

Comparison of fixation of spinal fractures.

Mechanical failure was induced in cadaver spines by applying flexion, extension, and lateral bending loads with continuous recordings of moment and rotation. Each spine was then stabilized with Harrington distraction rods, compression rods, and titanium mesh in sequence, and tested in a similar manner. The spines stabilized with mesh appeared stronger but less stiff than spines stabilized with Harrington rods.

Adult↗
PubMed1976

Characteristics of antifriction devices used for ski bindings.

These tests suggest that various antifriction devices do reduce the amount of torsion that can be transmitted to the skier's tibia during a slow twisting fall. It was shown that under various environmental conditions the antifriction devices are effective. Dirt negatively affected the performance of some devices. The importance of protecting bindings and antifriction devices from contamination cannot be overemphasized. It was shown that some antifriction devices perform better than others. In most instances the performance of the plate type of binding compares favorable with that of toe-heel bindings using antifriction devices. For the plate type of binding the dirt particularly had a detrimental effect. It should also be pointed out that these tests were run with one particular binding. These results would not necessarily be the same if the tests were conducted with another binding system. For instance, the limited motion of some of the antifriction devices (Lotork, Skidder) may impede their performance when used with bindings requiring a greater travel distance before release. The performance with other boot soles may be different from that with the particular boot sole used for these tests. Performance might be improved with a harder, smoother boot sole. Similarly, the effectiveness of the antifriction device may be reduced by the use of boot soles with a coarse pattern or relatively soft treads. In this test series a relatively small number of antifriction devices were evaluated. One should not presume that all devices will perform with equal effectiveness. Another factor, equally important, is the correction for the height of antifriction devices. Antifriction devices raise the boot sole from the ski surface, and if this change in height is not accounted for, the boot sole may effectively interfere with the operation of the toe or the heel unit. In summary, it can be stated that when properly applied and selected, antifriction devices make a significant contribution to skiing safety.

Athletic Injuries↗
PubMed1976

Theoretical estimation of binding release values.

In summary, it can be stated that the optimal binding setting for either the inadvertent release criterion or for the fracture criterion is a function of the binding characteristics. This study suggests that such binding characteristics should be a factor incorporated in recommended binding setting tables for the recreational skier. Bindings with large motions (large energy absorption capabilities) are most likely to meet both the fracture and inadvertent release criteria. Bindings with large motions are more likely to cause fracture if friction exists. This study emphasizes the necessity for reducing binding friction to an absolute minimum. Frictional resistance seriously compromises the performance of contemporary bindings.

Athletic Injuries↗
PubMedDate not supplied

Spinal cord monitoring of experimental incomplete cervical spinal cord injury: a preliminary report.

Incomplete spinal cord injuries occur as a result of contusion and mechanical compression of neural tissue. Anterior spinal cord compression may physiologically prevent optimal recovery of spinal cord function for varying periods of time. The aim of this research was to study an animal model of incomplete cervical cord injury with a spinal cord monitoring system utilizing computer-averaged cortical evoked potentials. Two animal models were utilized: a contusion injury by the weight drop method and an anterior cord compression injury. Results indicate that incomplete cord injuries of both types will recover depending upon the amount of initial force or energy applied and the length of time compression is applied. Thirteen compression and 14 contusion injuries were studied. Cortical evoked potentials measured in seventeen dogs paralleled the degree of cord injury as well as recovery.

Animals↗