Biomedical subjects

A V Seaber

Publications and source records attributed to A V Seaber.

At least 19 recordsLinked to original sources

PubMed1995

An electromyographic study of arm muscles during climbing.

Upper extremity muscle injuries from rock climbing are common. Knowledge of the activity of specific muscles during climbing may allow the development of training programs to reduce these injuries. This study evaluated the electrical activity of the first interosseous (IN), brachioradialis (BR), flexor digitorum superficialis (FD), and biceps brachii (BB) muscles in seven climbers by integrated electromyography (IEMG) during finger-tip pull-ups. The climbers, with forearms pronated, performed three consecutive pull-ups. Each pull-up consisted of: (1) hanging using four fingers of each hand, (2) pull-up to maximum elbow flexion, (3) slow return to starting position. The IEMG during maximum voluntary contraction (MVC) was obtained for each muscle separately, and the IEMG was normalized to MVC. During hanging, FD showed the highest normalized IEMG (0.64 +/- 0.20). During pull-up, the highest IEMG was produced by FD (0.69 +/- 0.25) and BR (0.67 +/- 0.19), while BB showed only 0.33 +/- 0.12 and IN 0.09 +/- 0.06. During lowering, FD again had the highest IEMG (0.74 +/- 0.24), while the EMG from BR was decreased to 0.42 +/- 0.14 and BB to 0.15 +/- 0.15. BR and BB showed an abrupt peak in EMG during pull-up and lowering, as opposed to FD which remained constantly highly activated, which suggests that FD does not contribute to elbow flexion even though it crosses the elbow joint. The high activation of FD and BR may explain their elevated incidence of injury during climbing. Thus, a reduction in climbing-related muscle injuries may be achieved by a training program that emphasizes conditioning of the BR and FD muscles.

Adult↗

PubMed1992

Combined effect of acute denervation and ischemia on the microcirculation of skeletal muscle.

Using direct in vivo videomicroscopy and a fluorescein dye technique, reperfusion injury after 3 h of ischemia was studied in the acutely denervated cremaster muscle of the rat. Compared with normally innervated controls, ischemia-induced reperfusion injury was more severe in the denervated group and included a delay of blood flow recovery, vortex formation, edema, hemorrhage, and vessel spasm. Vessel size was reduced at the arteriole and small artery level, and there was a decrease of reactive hyperemia. The injury mechanism may be related to a loss of active vasomotion and vascular response to vasoactive substances after denervation. The results suggest that shortening the ischemia time of denervated tissues may reduce ischemia-induced reperfusion injury. Similarly, given the same ischemia time, improved tissue reperfusion may be expected if the nerve supply is maintained.

Animals↗

PubMed1992

The Achilles Functional Index.

The literature regarding the management of spontaneous rupture of the Achilles tendon is controversial and confusing. The relative infrequency of the condition in any one center prohibits the completion of well-designed clinical studies. Many of the disputes could be addressed and innovations tested if an appropriate animal model were available. We present a method for evaluating Achilles tendon function from measurements of the prints, preserved in bromphenol-blue-impregnated photocopying paper, of the hindfeet of walking rats. The stimulus for this study was derived from de Medinaceli's method for assessing the functional condition of rat sciatic nerves (de Medinaceli L, Freed WJ, Wyatt RJ: An index of the functional condition of rat sciatic nerve based on measurements made from walking tracks. Exp Neurol 77:634-643, 1982). Four variables were measured from these walking tracks, and comparisons between the damaged (experimental) and intact (normal) side were converted to proportional deficits. The relative contribution of each parameter to the overall deficit was determined by multiple linear regression analysis, and the variables were weighted accordingly to obtain an "Achilles Functional Index" (AFI). A sham operation produced no functional deficit, whereas animals subjected to a 0.5-cm midsubstance Achilles tendon defect demonstrated a markedly impaired AFI. Animals with repaired transected Achilles tendons also demonstrated a significant, but less severely impaired AFI. The functional deficit in this repair group returned to control values by postoperative day 15, whereas animals with a defect remained impaired at day 15. Furthermore, an excellent correlation was found between the functional recovery and biomechanical properties (ultimate failure load) of the healing tendon (r = 0.94; p less than 0.001).(ABSTRACT TRUNCATED AT 250 WORDS)

Achilles Tendon↗

PubMed1992

The functional recovery of peripheral nerves following defined acute crush injuries.

This study evaluates the effect of crushing load on functional recovery of the sciatic nerve. Male Sprague-Dawley rats were divided into five groups: sham operation, resected sciatic nerve, and 100 g (13 mm Hg/mm2), 500 g (50 mm Hg/mm2), and 15,000 g (1,000 mm Hg/mm2) of sciatic crush load (groups 1-5). In groups 3-5, a 5-mm segment of sciatic nerve was crushed for 10 min using a specially designed crushing device. Motor functional recovery was assessed from hind-limb walking tracks by calculating a sciatic functional index. There was no detectable functional deficit in the group receiving sham operations, while the resected sciatic nerve group exhibited complete dysfunction for the full duration of the experiment. All groups subjected to crush exhibited an initial deficit that gradually recovered to normal by day 14 (100-g crush), day 39 (500-g crush), and day 53 (15,000-g crush). Histological changes were also related to the initial crushing load and the length of the recovery period. Results indicate that the crushing device described is able to administer an adjustable, defined crush injury to the rat sciatic nerve, and that the functional deficit resulting from such an injury can be easily monitored with a sciatic functional index. The rate of recovery of crushed nerves was directly related to the initial load. All crushed nerves recovered in this experiment, even after the application of a 15,000-g load for 10 min.

Animals↗

PubMed1992

Hemodynamic and histological differences in end-to-side anastomoses.

An end-to-side anastomosis is often a necessity in replantation surgery. This study examines the effects of elliptical versus slit arteriotomy and the angle of anastomosis on vessel patency and aneurysm formation. Forty male rats were divided into four groups of ten rats each. The right and left common iliac arteries were selected as a model. The results showed no significant statistical difference in patency rates among our four experimental groups. The end-to-side anastomotic technique of choice uses the elliptical arteriotomy placed at a 90 degrees angle. It provides good visualization and easy suture placement.

Anastomosis, Surgical↗

PubMed1992

The effect of extracorporeal shock wave lithotripsy on the prosthesis interface in cementless arthroplasty. Evaluation in a rabbit model.

The effect of extracorporeal shock wave lithotripsy on interfacial strength between prosthesis and bone in cementless arthroplasty was examined using a rabbit model. Paired femora, each implanted with fiber mesh porous coated titanium implants, were harvested from rabbits 15 weeks after implantation. In group I, one femur from each pair was exposed to lithotripsy treatment consisting of 2,000 shocks at 20 kV. In group II, one femur from each pair was exposed to 2,000 shocks at 26 kV. Contralateral femora from each pair served as controls in both groups. Mechanical pushout tests were conducted on the implants using a 1321 Instron testing machine at a constant rate of 1 mm/minute. Shock waves generated at 20 kV were found to have no significant decrease on either the prosthesis/bone interfacial strength or energy to failure of cementless implants. Shock waves generated at 26 kV produced a mean 17.45% decrease in the prosthesis/bone interfacial strength, which approached statistical significance (P = .062), and a 7.84% mean decrease in the energy to failure (P = .268). However, in four of the seven group II specimens, cortical fractures occurred. These findings suggest that lithotripsy will not aid in the removal of uncemented porous coated devices and lithotripsy inadvertently focused at an uncemented device will not disrupt significantly the prosthesis-bone interface.

Animals↗

PubMed1992

Revision arthroplasty facilitated by ultrasonic tool cement removal. An evaluation of whole bone strength in a canine model.

Ultrasonic driven tools have been developed to facilitate the removal of bone cement during revision arthroplasty. The effect on whole bone strength of cement removal by ultrasonic tools was examined in a canine femur model. Paired, fresh-frozen canine femora were divided into two groups. In group A, one femur from each pair was subjected to cement extraction with ultrasonic tools. In group B, one femur from each pair was subjected to manual cement extraction. Contralateral femora from each pair served as controls to determine the strength of intact femora. Torsional fractures were produced using a servocontrolled hydraulic testing machine (Minneapolis Testing System, Minneapolis, MN). Maximum torque, maximum angle, and energy capacity to failure were determined. Results were recorded as a reduction in percent value of the tested specimen versus the contralateral control. When comparing femora with cement removal by ultrasonic tools to the contralateral control femur, there were no statistical differences in ultimate torque (P = .83), maximum angle (P = .89), and energy capacity (P = .74) by analysis of variance. In addition, there were no significant differences between the group with ultrasonic tool cement removal and the group with manual tool removal. The authors conclude that in this canine model, removal of cement with ultrasonically driven tools has no adverse effects on whole bone strength.

Animals↗

PubMed1992

Reversing nerve-graft polarity in a rat model: the effect on function.

To evaluate the effect of nerve-graft polarity on function, a 1-cm segment of sciatic nerve was excised and reoriented in three groups of 20 adult Sprague-Dawley rats. In one group, the nerve was cut and anastomosed in the original orientation to act as a control. In the second group, the nerve-graft polarity was reversed 180 degrees. The final group underwent reversal of polarity 180 degrees and was rotated 180 degrees, (i.e., the posterior tibial nerve fascicles proximally were opposite to the peroneal nerve fascicles distally). Functional recovery was evaluated using Bain's modification of de Medinaceli's sciatic functional index (SFI). Rat-track analysis was performed over a 120-day period. Histologic correlation was also performed at the time of sacrifice. From our study, we concluded that reversing nerve-graft polarity, with or without rotation, does not influence subsequent function in this model.

Anastomosis, Surgical↗

PubMed1992

Vasodilator action of pentoxifylline on microcirculation of rat cremaster muscle.

Pentoxifylline improves microvascular blood flow in conditions of vascular insufficiency. The clinical benefits of pentoxifylline have been attributed to its effects on the cellular elements of whole blood, although a few studies suggest it may also be a vasodilator. The purpose of this study was to determine whether pentoxifylline has a vasodilator effect on the luminal diameter of small arteries preconstricted with norepinephrine and on resting small arteries in the rat cremaster muscle. Intravital videomicroscopy was used in order to observe directly the vasodilator capacity of topically applied pentoxifylline. The results reveal that pentoxifylline (100 microM and more) can significantly dilate small arteries preconstricted with norepinephrine. Pentoxifylline had no effect on the diameter of resting small arteries. These results suggest that vasodilation may play a role in the ability of pentoxifylline to improve arterial blood flow.

Animals↗

PubMed1991

The effect of acute denervation on the microcirculation of skeletal muscle: rat cremaster model.

Although tissue is denervated during replantation of a severed part, tissue transfer, or muscle transplantation, there are few studies concerning the effects of acute denervation on muscle microcirculation. We have described a surgical procedure that totally denervates the rat cremaster muscle. Histological examination of the denervated tissue has given convincing evidence of nerve degeneration and skeletal muscle atrophy, accompanied by electrophysiological evidence of total denervation. The diameters of each component of the microcirculation were measured before and after denervation. Arterioles and arteries ranging in size from 10 to 70 microns in diameter were found to increase significantly in size immediately after acute denervation. Larger arteries and veins did not undergo significant diametrical increases. These findings suggest that total acute denervation significantly increases the diameter of small arteries and arterioles, thereby decreasing the resistance in the arterial bed and increasing blood flow. Since this phenomenon is of limited duration (20 min), it would appear to be ineffective in enhancing reperfusion and oxygenation at the time of reattachment of amputated parts or during vascularized tissue transfers, until methods of prolonging it for several hours or more are found.

Animals↗

PubMed1991

Inhibition of epinephrine-induced vasospasm with adrenoreceptor blockade in the rat cremaster muscle.

This study demonstrates that intravenous epinephrine causes arterial vasospasm, but not venous constriction, in the microcirculation of the rat cremaster muscle. This effect can be blocked by a smooth muscle relaxant such as papaverine or an alpha receptor antagonist such as phentolamine. Circulating vasospastic agents such as epinephrine are important determinants of microcirculatory blood flow, and inhibition by pharmacologic means may enhance blood flow and survival in microvascular surgery.

Animals↗

PubMed1991

Morphologic and morphometric analyses of rat femoral arteries after crush injury.

Replantation after crush amputation has a relatively low success rate. An arterial crush injury was produced in rats under a range of pressure (8.5 to 2,551 g/mm2) and durations (10 to 60 minutes). The degrees of vessel injury and thrombus formation were evaluated as functions of both crush force and duration, and the healing process was followed for 8 weeks. Crushing resulted in morphologic damage to the arterial wall but did not impair patency. Damage was directly proportional to crush pressure and duration. Intimal denudation caused flat platelet adhesion but no thrombus formation or thrombosis. Re-endothelialization was completed by 2 weeks. Intimal hyperplasia appeared at 1 week and consisted of endothelia in the most luminal layers and smooth muscle in the deeper layers. the internal elastic lamina was intact in all specimens and was thought to minimize platelet aggregation on the arterial wall after denudation of the intima.

Animals↗

PubMed1991

Prosthetic silicone scaphoid strains: effects of intercarpal fusions.

To assess stress shielding by partial intercarpal fusion, strains within a silicon scaphoid prosthesis were measured in five fresh upper extremities while the wrist was moved through a functional range of motion before and after capitate-lunate and capitate-hamate-lunate-triquetral intercarpal fusions. Capitate-lunate fusions resulted in an overall 18.4% reduction in compressive strains and a 10.8% reduction in tensile strains. Capitate-hamate-lunate-triquetral fusions reduced compressive strains by 28.5% and tensile strains by 26.3%. Radially deviated positions and positions of extension produced no reduction in strains with the partial fusions. Modest strain shielding can be obtained with partial intercarpal fusions. The effect, however, is position dependent, and whether this degree of strain shielding can reduce the incidence of particulate synovitis remains unknown.

Arthrodesis↗

PubMed1991

Screw-augmented fixation of acetabular components. A mechanical model to determine optimal screw placement.

Sixteen embalmed hemipelves were used to determine the optimal acetabular screw placement to provide maximal screw pull-out strength in unicortical and bicortical screw fixation. The anterior column, superior ilium, posterior column, ischium, and pubis regions of the pelvis were tested using 6.5-mm titanium alloy screws and a hydraulic servo-controlled 1321 Instron testing machine. Force vs displacement data were acquired. Bicortical fixation was stronger than unicortical fixation in the four zones compared. This difference was significant in the superior ilium, posterior column, and ischium. The anterior column could not accept unicortical screws due to inadequate bone depth, which ranged between only 6 mm and 10 mm. Bicortical fixation was significantly greater in the superior ilium, posterior column, and ischium than in the anterior column or pubis. Unicortical fixation was greatest in the superior ilium. This information may aid decisions concerning the positioning of screws to augment acetabular component fixation.

Acetabulum↗

PubMed1990

Vasodilator action of prostaglandin E1 on microcirculation of rat cremaster muscle.

Vascular spasm is often present after microsurgical procedures, and its presence or absence can greatly influence the success rate of such operations. Prostaglandin E1 (PGE1) is known to be a potent vasodilator and antiaggregator of small blood vessels. Using intravital videomicroscopy in the rat cremaster model, this study visually and quantitatively monitored changes in vessel diameter to observe the effect of PGE1 on the microcirculation and compared its action with that of 1% lidocaine. The results suggest that PGE1 (10 micrograms/ml) can significantly relieve epinephrine-induced vasoconstriction at the terminal arteriole, arteriole, and small artery level (vessel diameters 10-50 microns). The vasodilatory action of PGE1 is reflected by an increase in vessel diameter, and PGE1 may have a role in reversing vascular spasm after microsurgery, enhancing the survival rate of replanted extremities.

Administration, Topical↗

PubMed1990

The relationship of functional return to varying methods of nerve repair.

This experimental study correlated varying methods of nerve repair with the degree of functional return using the rat sciatic nerve as a model. Six groups of adult male Sprague-Dawley rats (300 to 350 g) had their left sciatic nerve crushed (Group 1), transected and not repaired (Group 6), or transected and repaired using four methods that varied the degree of axonal alignment (Groups 2, 3, 4, and 5). Functional return was evaluated weekly using the sciatic functional index (SFI) and histology. Group 1 (crush) had a significantly better functional return than the other groups (p less than .001). Group 6 (no repair) had a significantly worse functional return than the other groups (p less than .001). Groups 2, 3, 4, and 5, regardless of the precision of axonal alignment, experienced the same degree of functional return (p less than .05). In all groups, with the exception of Group 1 (crush), the degree of functional return was poor. As multiple modifications in conventional microsurgical neurorrhaphy have not resulted in a significant functional improvement, factors not addressed by current techniques apparently compromise clinical results. Further improvement in the results of neurorrhaphy will require modifications in our techniques beyond presently conventional microsurgical methods.

Animals↗

PubMed1990

A comparative study of the effect of arterial and venous occlusion after various periods of ischemia.

The author attempted to quantify any additional tissue damage resulting from one hour of venous occlusion after controlled periods of ischemia in skeletal muscle, compared to equal time periods of ischemia. The rat quadriceps muscle was used. pH and temperature were monitored during the experiment and the damage was evaluated on histochemical sections. Of the other two parameters monitored in this study, the pH recovery rate during reperfusion best reflected tissue perfusion and served as a predictor for the extent of tissue damage, when global ischemia or the combination of ischemia and postischemic venous stasis did not exceed five hours. Apart from the nonstained lethally damaged areas, interstitial tissue edema and cellular infiltration were constant findings in all muscles that sustained ischemia or ischemia and subsequent venous occlusion. However, both findings were more pronounced in the muscles that underwent venous obstruction. Muscle fibers were more edematous after venous occlusion, compared to ischemic muscles. Thrombosed veins and collapsed arteries, surrounded by excessive edema and inflammatory reaction, were common in muscles after ischemia and venous occlusion. Comparing the difference in percent of lethal damage from one hour of postischemic venous stasis versus the damage from additional ischemia of equal duration, findings demonstrated comparable damage when reperfusion was established in less than five hours.

Animals↗

PubMed1990

The effects of exposure of articular cartilage to air. A histochemical and ultrastructural investigation.

The effects of exposure of articular cartilage to air and the potential for reversibility of the histological and ultrastructural changes that were produced by this exposure were investigated in the knee joint of the rabbit. After a medial parapatellar arthrotomy and lateral dislocation of the patella, the surface of the articular cartilage was exposed to air for one, two, and three hours in forty-five rabbits. Reversibility of the changes was assessed in fifteen rabbits after exposure of the cartilage to air for three hours, closure of the joint, and six weeks of recovery. Histochemical and ultrastructural changes were evaluated, with use of the contralateral non-exposed knee joint as a control. Depletion of glycosaminoglycans in the matrix of articular cartilage, as indicated by a loss of surface staining with toluidine blue, occurred after one hour of exposure to air. Ultrastructural changes occurred in chondrocytes throughout the full thickness of articular cartilage after one hour of exposure. Increases in the time of exposure to air resulted in more pronounced ultrastructural abnormalities in chondrocytes throughout the entire thickness of the articular cartilage, but there was no apparent irreversible cellular injury. Six weeks after arthrotomy, the chondrocytes had fully recovered from the changes that had been noted immediately after exposure to air, and they were devoid of degenerative changes. The cells showed ultrastructural evidence of increased metabolic activity in the nucleus and cytoplasm. In addition, the chondrocytes had partially restored the depleted glycosaminoglycans.

Air↗