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Biomedical subjects

D K Dedrick

Publications and source records attributed to D K Dedrick.

12 recordsLinked to original sources
PubMed1992

Quantitative assessment of cartilage surface roughness in osteoarthritis using high frequency ultrasound.

Osteoarthritis (OA) is a common disease which affects nearly 50% of people over age 60. Histologic evaluation suggests that fibrillations approximately 20-150 microns are among the earliest changes in the articular cartilage. We propose a technique to quantify these surface fibrillatory changes in osteoarthritic articular cartilage by considering the angular distribution of the envelope-detected backscattered pressure field from an incident 30-MHz focused transducer. The angular distribution of the scattered acoustic field from an inosonifying source will directly relate to the distribution of surface fibrillatory changes. Data are presented for three different grades (400, 500 and 600 grit) of commercially available emory paper and three samples of osteoarthritic femoral head articular cartilage, which were visually assessed as having smooth, intermediate and rough surfaces, respectively. Our preliminary results indicate a probable monotonic relationship between articular cartilage roughening and the degree of broadening in the angle-dependent pressure amplitude. When applied to the emory paper, the technique indicates sensitivity to differences as small as approximately 5-10 microns in mean roughness. This procedure may provide an extremely sensitive and reproducible means of quantifying and following the cartilage changes observed in early osteoarthritis.

Cartilage, Articular↗
PubMed1992

The effects of intraosseous infusion on the growth plate in a nestling rabbit model.

STUDY OBJECTIVE: The objective of this study was to test the hypothesis that saline or bicarbonate infusion does not damage the growth plate in a nestling rabbit model. SETTING: Animal laboratory. DESIGN: In this prospective study, 22 tibias from nestling rabbits were randomized into control, puncture-only, physiologic saline, or bicarbonate infusion groups and killed three and five days after treatment for evaluation of injury. MEASUREMENTS: Bone injury was evaluated by microradiograph and by decalcified and undecalcified histology. RESULTS: Radiographs demonstrated loss of trabecular (ie, calcified) bone after infusion of both saline and bicarbonate solutions. Although no histologic damage to the cell lines of the growth plate was seen, newly formed bone trabeculae were seen in both infusion groups, suggesting injury and repair at sites of infusion. These findings were absent in control and puncture-only groups. No histologic or radiographic differences were seen between saline and bicarbonate infusions. CONCLUSION: The nestling rabbit provides a good animal model for evaluating the effects of intraosseous infusion on growing long bones and cartilage. Saline and bicarbonate infusions did not damage morphologically the metaphyseal growth plate but did cause loss of bone trabeculae that support the growth plate. The injury appeared to be repaired rapidly in these nestling rabbits.

Animals↗
PubMed1991

Forces acting during air and ground transport on patients stabilized by standard immobilization techniques.

OBJECTIVE: Transportation, whether by air or ground, exposes the injured patient to mechanical shocks and vibrations. These forces and their hazardous potential remain largely unknown. The purpose of this study was to identify, characterize, and compare the forces generated during patient transport in helicopter and ground ambulances. METHODS: Forces generated during transport were measured using an instrumented, low mass triaxial accelerometer fixed to a standard backboard. Measurements were recorded in three axes with an adult subject immobilized on the board during experimental ambulance and helicopter trials. Acceleration waveforms were analyzed in each mode of transport. RESULTS: Forces for both ground and air transport ranged 0.07g to 0.19g root mean square, and 0.32g to 0.83g mean peak. The vibrational forces in the helicopter were fairly discrete, located at 6.6, 19.5, and 39 Hz, and axis dependent. Ground ambulance vibrations were more diffuse, occurring below 1 Hz and between 10 and 15 Hz. Crest factor analysis shows that shocks were more uniform in the helicopter than on the ground, especially in the anterior-posterior axis. CONCLUSION: These data suggest that transportation by helicopter subjects supine patients to greater lateral and vertical forces, but smaller head to toe forces, than ground transportation (P less than .05). In general, the forces to which a backboarded subject is subjected during transport range from 0.32g to 0.83g, vary by direction, and are more predictable for air than for ground transport. The clinical significance of these measurements requires further study.

Acceleration↗
PubMed1991

Early bone changes in experimental osteoarthritis using microscopic computed tomography.

Alterations in trabecular subchondral bone have been measured using a microscopic computed tomography scanner in the guinea pig hind-limb myectomy model of osteoarthritis. These bone changes can be found as early as histologic changes in cartilage. To evaluate the influence of the myectomy on the animals, a gait study was performed. This data reveals an alteration in acceleration at the foot-flat phase of gait in the operated limb only, providing early quantification of the interaction between mechanics and biology.

Animals↗
PubMed1990

Sonographic evaluation of osteoarthritic femoral condylar cartilage. Correlation with operative findings.

Femoral condylar cartilage abnormalities were evaluated in patients treated with total knee arthroplasty, and real-time ultrasonic images were correlated with the abnormalities seen in the corresponding gross pathologic specimens. Subjective impressions of abnormalities on the images recorded on film correlated well with pathologic findings. Thickness measurements were easily made in normal images but proved difficult at sites of cartilage damage where the cartilage-bone and cartilage-soft-tissue interfaces became less clear. This study suggests that with further technologic refinement, this technique may provide a rapid and cost-effective method of assessing the integrity of femoral condylar cartilage.

Adult↗
PubMed1989

Defibrillation safety in emergency helicopter transport.

Rotary aircraft play a growing role in the transport of critically ill patients who may require emergency treatment, including defibrillation, during transport. The close quarters and proximity of vital electronic equipment have generated concern among personnel carrying out defibrillation in the air. We address the chief safety issues in helicopter defibrillation by providing measurements of the transient leakage current resulting from contact with a paddle and tested in-flight electronic interference and survey the defibrillation experience of helicopter programs. Our data show that airborne defibrillation is safe. A maximum of 1.5 mA of transient leakage current was measured from a standard battery-powered defibrillator, well within the accepted safety standard of 50 mA. In flight, there was no interference with the avionics or medical equipment, and adequate clearance was available for personnel. Of the helicopter programs surveyed, 69 (87%) had defibrillated in flight without incident. We conclude that defibrillation can be performed in the helicopter without hesitation whether on the ground or in the air, provided standard defibrillation precautions are observed.

Aircraft↗
PubMed1989

Emergency transport and positioning of young children who have an injury of the cervical spine. The standard backboard may be hazardous.

In ten children who were less than seven years old, an unstable injury of the cervical spine was found to have anterior angulation or translation, or both, on initial lateral radiographs that were made with the child supine on a standard flat backboard. In all ten patients, extension was the proper position for reduction of the injury of the cervical spine. Young children have a large head in comparison with the rest of the body. When a young child is positioned on a standard backboard, the neck may be forced into relative kyphosis. Supine and upright lateral radiographs that were made of seventy-two children who did not have a fracture also demonstrated more relative cervical kyphosis in younger children when they were in the supine position. Calculations from anthropometric data documented disproportionate rates of growth of the head and the chest. The circumference of the head grows logarithmically, but the circumference of the chest grows linearly. This disproportionate growth causes young children to have a relatively large head. When they lie supine, the neck is flexed. To prevent undesirable cervical flexion in young children during emergency transport and radiography, a standard backboard can be modified to provide safer alignment of the cervical spine. This can be accomplished by the use of a recess for the occiput to lower the head or of a double mattress pad to raise the chest.

Age Factors↗
PubMed1987

Resistance of rapidly expanded random skin flaps to bacterial invasion.

This study tested the hypothesis that rapidly expanded random pattern skin flaps demonstrate enhanced resistance to bacterial invasion from intradermal injection of Staphylococcus aureus in a porcine model. Sites for a 6 X 12 cm expanded, a 6 X 9 cm sham-expanded, and a 6 X 6 cm acute random pattern skin flap were outlined, but not elevated, on the backs of 14 white pigs. A 450-cc tissue expander inserted beneath the panniculus carnosus at the site for expansion was sequentially filled to the limits of skin viability each day for 5 days. At the sham site a tissue expander was similarly inserted but left unexpanded; the acute flap site was left undisturbed. On day 8, flaps were elevated, immediately sutured in place, and 0.1 ml of saline solution containing 10(7) Staphylococcus aureus inoculated intradermally at four corresponding sites in each flap and at three sites in normal skin. In seven animals these sites were at the proximal base of the flaps; in seven others the sites were distal. The resulting areas of erythema and skin ulceration were measured on each of the next 3 days and the measurements compared. At corresponding proximal sites, the mean area of erythema and ulceration measured over the next 3 days in expanded flaps (31.2 mm2) and in sham-expanded flaps (33.8 mm2) was significantly less than in acute flaps and control skin (47.5 mm2, 43.4 mm2, p less than 0.05). Measurements in the rapidly expanded flaps were not significantly different than those in the sham-operated expanded flaps.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1986

Complications of femoral neck fracture in young adults.

Femoral neck fractures are uncommon but serious injuries in young adults, with high rates of nonunion and avascular necrosis reported. This study was undertaken to examine the relationship between the mechanism and severity of injury, anatomic site of fracture, health status, and method of therapy on the incidence of these complications in young adults. The hospital records of 32 skeletally mature patients between the ages of 15 and 50 years (mean, 33) treated for femoral neck fracture between 1975 and 1982 were reviewed, and data analyzed for the 25 patients with a minimum 2-year followup (mean, 61 months). Data pertaining to the cause of injury, fracture pattern, prior health status, overall injury severity, method of fracture treatment, and long-term outcome were analyzed. Nonunion of the fracture site was observed in five (20%); avascular necrosis in nine (36%). Of patients with subcapital fracture 83% developed nonunion or avascular necrosis, compared to 21% with true femoral neck fracture (p = 0.05). There was no difference in cause of injury, overall injury severity, degree of comminution, displacement, method of treatment, or prior health status between those with and without complications. In this study, high rates of nonunion and avascular necrosis were seen after all types of femoral neck fracture in young adults, but were more often associated with subcapital fracture. These complications of hip fracture appeared to be independent of health status, method of treatment, or mechanism or severity of injury.

Adult↗