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Biomedical subjects

A I King

Publications and source records attributed to A I King.

At least 19 recordsLinked to original sources
PubMed1992

Computer simulation of occupant neck response to airbag deployment in frontal impacts.

A mathematical simulation was performed to study the potential of head and neck injury to an unbelted driver restrained by an airbag. The baseline study represented a 50th percentile male dummy driving in a compact car with the steering wheel perpendicular to the floor. The vehicle was moving at 48 km/hour at the time of impact. Model predictions were compared with sled test results. The data agreed reasonably well. A parametric study was performed to study the effect of changing the steering wheel angle and the size of the airbag. It was found that when the standard 20 degrees angle steering wheel was used, neck joint torques were decreased by 22 percent while the resultant head acceleration increased 41 percent from the base line study. When the vertical dimension of the airbag was reduced by 10 percent, neck joint torques were increased by 14 percent, while head acceleration showed a slight decrease of 9 percent.

Acceleration↗
PubMed1992

The effects of controlled mechanical loading on group-II, III, and IV afferent units from the lumbar facet joint and surrounding tissue. An in vitro study.

An in vitro model was developed to investigate the responses of afferent units in the lumbar spine to controlled loading as measured by a load-cell. The neuronal discharge was recorded simultaneously with loading. Three types of neuronal responses were observed. The first type of response involved phasic-type mechanoreceptors, which responded to movement, regardless of direction or initial position. The response did not outlast the movement phase of loading. These units may serve as velocity detectors. The second type of response was seen in slowly adapting low-threshold mechanoreceptors, which tended to respond to loading in the 0.3 to 0.5-kilogram range with an immediate and sustained increase in the rate of firing. This type of response appears to be associated with the activation of low-threshold group-II and group-III fibers, which were located in muscles and tendons inserting into the facet joint. The third type of response involved slowly adapting high-threshold mechanoreceptors, which could not be activated until a threshold of three to five kilograms had been exceeded. It appears that this type of response is at least partially due to the activation of high-threshold group-III and group-IV capsular afferent units, which may signal noxious mechanical stimulation.

Adaptation, Physiological↗
PubMed1991

Human head dynamic response to side impact by finite element modeling.

The dynamic response of the human head to side impact was studied by 2-dimensional finite element modeling. Three models were formulated in this study. Model I is an axisymmetric model. It simulated closed shell impact of the human head, and consisted of a single-layered spherical shell filled wiht an inviscid fluid. The other two models (Model II and III) are plane strain models of a coronal section of the human head. Model II approximated a 50th percentile male head by an outer layer to simulate cranial bone and an inviscid interior core to simulate the intracranial contents. The configuration of Model III is the same as Model II but more detailed anatomical features of the head interior were added, such as, cerebral spinal fluid (CSF); falx cerebri, dura, and tentorium. Linear elastic material properties were assigned to all three models. All three models were loaded by a triangular pulse with a peak pressure of 40 kPa, effectively producing a peak force of 1954 N (440 lb). The purpose of this study was to determine the effects of the membranes and that of the mechanical properties of the skull, brain, and membrane on the dynamic response of the brain during side impact, and to compare the pressure distributions from the plane strain model with the axisymmetric model. A parametric study was conducted on Model II to characterize fully its response to impact under various conditions.(ABSTRACT TRUNCATED AT 250 WORDS)

Biomechanical Phenomena↗
PubMed1990

Control of transmission of HIV and other bloodborne pathogens in biomechanical cadaveric testing.

The Bioengineering Center at Wayne State University uses universal blood and body fluid precautions when handling human cadavers in biomechanical testing. Our infection control protocol largely follows the precautions outlined by the Centers for Disease Control (CDC). In addition, we screen each cadaver for the human immunodeficiency virus (HIV) and the hepatitis B virus (HBV) before accepting a cadaver for biomechanical tests. This paper discusses acquired immunodeficiency syndrome (AIDS) and infection control guidelines by addressing the following: (a) what is AIDS? (b) How infectious is the HIV virus, which causes AIDS? (c) What precautions should be taken in cadaveric testing to safeguard against HIV and other bloodborne pathogens? The infection control procedures presented in this paper can be adapted to whole-body cadaveric testing or to the testing of tissue specimens.

Biomechanical Phenomena↗
PubMed1990

Mechanosensitive afferent units in the lumbar facet joint.

The purpose of this study was to characterize somatosensory units of the lumbar facet joint, which may play a central role in idiopathic low-back pain. A laminectomy was performed on the lumbar spine of adult male New Zealand White rabbits. Receptive fields of mechanosensitive afferent units were investigated in the lumbar facet joint and adjacent surrounding tissues, and electrophysiological recordings were obtained from filaments of the dorsal root. Twenty-four units were identified in the region of the facet joint: ten, in the capsule of the joint; twelve, in the border regions between capsule and muscle or tendon; and two, in the ligamentum flavum. Of these units, two had a conduction velocity that was slower than 2.5 meters per second (group IV), fifteen had a velocity ranging from 2.5 to twenty meters per second (group III), and seven had a velocity faster than twenty meters per second. Seven units had a von Frey threshold of more than 6.0 grams, thirteen had a threshold of less than 6.0 grams, and four were not examined. Seven units in the facet joint responded to movement of the joint. Fourteen other mechanosensitive units were found in the muscle, tendon, and interspinous ligament; seven had a conduction velocity of 2.5 to twenty meters per second, and seven had a velocity that was faster than twenty meters per second.

Animals↗
PubMed1989

Sensory innervation of soft tissues of the lumbar spine in the rat.

The purpose of this study was to investigate neurophysiologically and anatomically the soft tissues of the dorsal compartment of the lumbar spine in order to understand better their possible role in low back pain. The focus was primarily on the lumbar facet joint and supraspinous ligament of the Sprague-Dawley rat. Microdissection of the dorsal ramus and electrophysiological and neuroanatomical studies of the dorsal ramus and its terminations in paravertebral tissue revealed that (a) there are mechanosensitive, slowly adapting fibers in the rat lumbar facet joint capsule; (b) there are slowly adapting, mechanosensitive units in the rat supraspinous ligaments that respond to tensile loading; both types of mechanosensitive units have high threshold; (c) mechanical stimulation of these tissues sometimes elicits afterdischarges lasting several minutes; (d) many extracellular recordings from the medial branch of the dorsal ramus appear to be reflex activity to mechanical stimulation; (e) silver impregnation of the rat joint capsule reveals individual axons, very few of which were encapsulated, suggesting that they terminate in free nerve endings; and (f) the nerves of the rat facet joint capsule contain 68, 160, and 200 kdalton polypeptide subunits of neurofilament protein (NFP). These results indicate that neurons of lumbar facet joint capsules and ligaments in the back are sensitive to mechanical strain and that the higher threshold neurons may serve a nociceptive (pain) function.

Animals↗
PubMed1989

Biomechanics of the human chest, abdomen, and pelvis in lateral impact.

Fourteen unembalmed cadavers were subjected to 44 blunt lateral impacts at velocities of approximately 4.5, 6.7, or 9.4 m/s with a 15 cm flat circular interface on a 23.4 kg pendulum accelerated to impact speed by a pneumatic impactor. Chest and abdominal injuries consisted primarily of rib fractures, with a few cases of lung or liver laceration in the highest severity impacts. There were two cases of pubic ramus fracture in the pelvic impacts. Logist analysis of the biomechanical responses and injury indicated that the maximum Viscous response had a slightly better correlation with injury than maximum compression for chest and abdominal impacts. A tolerance level of VC = 1.47 m/s for the chest and VC = 1.98 m/s for the abdomen were determined for a 25% probability of critical injury. Maximum compression was similarly set at C = 38% for the chest and at C = 44% for the abdomen. The experiments indicate that chest and abdominal injury may occur by a viscous mechanism during the rapid phase of body compression, and that the Viscous and compression responses are effective, complementary measures of injury risk in side impact. Although serious pelvic injury was infrequent, lateral public ramus fracture correlated with compression of the pelvis, not impact force or pelvic acceleration. Pelvic tolerance was set at 27% compression.

Abdominal Injuries↗
PubMed1989

Experimental verification of facet load transmission by direct measurement of facet lamina contact pressure.

This paper presents results of a new measuring technique by means of which facet tip contact pressure data were obtained. The aim of the paper is to demonstrate by direct measurement the existence of a load transmission mechanism through the facet joint. Six lumbar spine motion segments were used in 21 tests. Simulated extensor muscle action was provided to overcome moments due to eccentric loads which represented body weight and an external hand-held load acting 340 mm anterior to the center of the disc. Facet pressure was measured in all cases when muscle load was applied to counteract body weight. This pressure increased when more muscle force was applied to balance the externally applied flexion moment. When the anterior load was released suddenly, there was a large increase in facet pressure with a concomitant decrease in disc pressure.

Adult↗
PubMed1989

Injury biomechanics research: an essential element in the prevention of trauma.

The central aspects of injury biomechanics research are defined and research approaches described. These aspects include the identification and definition of impact injury mechanisms, the quantification of biomechanical response to impact, the determination of impact tolerance levels, and the development and use of injury assessment devices and techniques for evaluating injury prevention systems. The current status of knowledge and technology is then reviewed for the head, cervical spine, thorax, abdomen, and lower extremity. Important gaps are identified, and research priorities emphasizing functional impairment are proposed.

Abdominal Injuries↗
PubMed1988

Localization of substance P and neurofilament immunoreactive fibers in the lumbar facet joint capsule and supraspinous ligament of the rabbit.

An indirect immunofluorescence method was utilized to identify substance P-like immunoreactive (SPLI) and neurofilament protein immunoreactive (NFIR) fibers in the lumbar facet joint capsule and supraspinous ligament of the rabbit. The results demonstrated a large population of NFIR fibers, indicating that these tissues are richly innervated, and a smaller population of SPLI fibers. In some fibers, neurofilament protein and substance P were colocalized. The data suggest that the facet joint capsule and the supraspinous ligament contain SPLI nociceptive fibers that could be a source of low back pain.

Animals↗
PubMed1987

New rehabilitation concepts in management of radical neck dissection syndrome. A clinical report.

The purposes of this article are to define radical neck syndrome and to present a new concept of using range-of-motion exercises combined with isokinetic muscle loading rehabilitation to provide the patient with a functional and pain-free shoulder. Each part of the rehabilitation program, including an exercise program that the patient continues at home, is explained in detail.

Exercise Therapy↗
PubMed1984

Mechanism of facet load transmission as a hypothesis for low-back pain.

Low-back pain has a complex and multi-faceted etiology. The articular facets have been shown to be load-bearing structures and may be a site for low-back pain. The aim of this paper is to establish the mechanism for the transmission of axial load across a facet joint and to propose a facet-related hypothesis for low-back pain. The mechanism of load transmission was studied by two methods. Lumbar segments were instrumented with an intervertebral load cell (IVLC) to measure disc load so that facet load could be deduced. The applied load was moved 10 mm anteriorly and 12.5 mm posteriorly from the center of the vertebral body. The facets then were separated from the body and loaded axially to determine their stiffness in tension and compression and to observe the failure mode of the joint. It was shown optically that compressive loading of the isolated facet joints was equivalent to spinal extension and tensile loading to spinal flexion. Lastly, a finite element model of a lumbar motion segment was developed to simulate the transmission of facet load and to study the effects of disc degeneration on facet loads. Results of the study on six lumbar segments revealed that the normal facets carried 3-25%. If the facet joint was arthritic, the load could be as high as 47%. Experiments on isolated facet joints revealed that they behaved as a stiffening spring in compression and were weak in tension.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1984

A review of biomechanical models.

This paper surveys biomechanical models of the nonimpact type, involving the musculo-skeletal system. Models of bones, joints and body segments, including human gait and motion of the whole body are discussed. In particular, stress analysis of bone, calculation of ligament and muscle forces across joints and the kinetics and kinematics of locomotion are discussed. The models are described in terms of the method of formulation, the method of solution and the realism of the results obtained. There is a need for more data on material properties of various body tissues and more experimental research to develop techniques for validating many of the models. Further work on the selection of appropriate objective functions for indeterminate problems is also required.

Aerospace Medicine↗
PubMed1982

Sweat gland tumors of the head and neck.

Surgeons performing soft-tissue surgery in the head and neck area occasionally will encounter other varieties of neoplasms, such as skin-appendage tumors, in addition to basal cell carcinoma and squamous cell carcinoma. Sweat gland tumors are the most common variety of the skin-appendage tumors and the most easily confused with basal cell carcinoma and squamous cell carcinoma. We report this case to illustrate this fact. The classification of sweat gland tumors and their suggested management are reviewed.

Adenoma, Sweat Gland↗