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Biomedical subjects

J R Urbaniak

Publications and source records attributed to J R Urbaniak.

At least 19 recordsLinked to original sources
PubMed1997

Assessment of ischemia and reperfusion injury.

Direct videomicroscopy of the rat cremaster muscle microcirculation supplemented by animal models of replantation, vascular crushing, and muscle function after injury and recovery were used to investigate the occurrence of reperfusion failure. It is evident that failure of blood reflow may be induced by multiple factors that can be grouped into categories of ischemia, intimal damage, and systemic or local responses, which are referred to as the no reflow triad. The components comprising the 3 sides of the no reflow triad can interact with one another in an intricate manner, and any single factor or combination of factors is capable of triggering the events leading to reperfusion failure. The pronounced regional nature of reperfusion injury and the direct relationship between the severity of the observed vascular alterations and increasing duration of ischemia have been documented. The dynamic changes and histopathology of the microcirculation included constriction of the arteries, swelling of endothelial and leukocytes, and erythrocyte rouleaux formation during ischemia. As ischemia duration was lengthened, the degree of these changes increased correspondingly. The changes on reperfusion were disruption of blood flow patterns, vortex formation, regional stasis, adhesion and migration of leukocytes, focal hemorrhage, edema, vasospasm, and platelet aggregation. The deleterious effects of systemic acidosis, interstitial hemorrhage, denervation, and prolonged venous occlusion were subsequently documented. The application of information gained from this series of laboratory experiments has resulted in continued improvement in the success rate in clinical microvascular surgery.

Abdominal Muscles↗
PubMed1996

Functional effects of lymphotoxin on crushed peripheral nerve.

The effect of lymphotoxin (LT) on the functional recovery of crushed peripheral nerves was studied. Using a specially designed compression device, a 5 mm segment of the right sciatic nerve of rats was subjected to a 100 g crush load with a 2 hr duration. The rats in the experimental and control groups received two doses of LT (20 micrograms/kg each) or the same volume of saline, respectively, administered intraperitoneously 24 hr and 1 hr before the procedure. Walking track tests and histologic examinations were performed at intervals up to 56 days after the crush. Motor functional recovery in the LT pretreated group started at day 7 while the crushed limb in the control group remained totally dysfunctional. The sciatic functional index improved faster in the LT group than in the control group during the second week after the crush and reached a significant difference (P < 0.05) at day 18. Subsequently, both groups had a similar evolution. Histologic results paralleled the functional findings. In conclusion, LT can promote motor functional recovery of crushed rat peripheral nerve in the early stage of regeneration.

Analysis of Variance↗
PubMed1996

Protective effect of hypothermia on contractile force in skeletal muscle.

The clinical success of limb replantation and tissue transfer is partly dependent on the duration of ischemia experienced by the amputated part. This study focused primarily on the damage that occurs during this ischemic period. An experimental system was implemented that allowed the observation of contractile function in totally isolated skeletal muscle after ischemia. Contractile function was selected as an indicator of ischemic damage because normal function is the ultimate goal of replantation. All experiments were performed on the rat extensor digitorum longus. The muscles were subjected to ischemic periods of 1.5, 3.0, and 5.0 hours and were stored in either a hypothermic (4 degrees C) or a room-temperature (23 degrees C) environment during the ischemic interval. After the ischemic period, all muscles were transferred to a tissue bath and were subjected to contractility testing, followed by fatigue testing. In both groups, muscle function decreased as the ischemic interval was increased. A significant difference in function between the normal control and the muscles of both ischemic groups implied that ischemic injury had occurred in the hypothermic and room-temperature muscles, even with the relatively short 1.5-hour ischemic interval. After each ischemic interval however, the hypothermic muscles produced significantly greater contractile force than the room-temperature muscles in both the contractility and the fatigue tests. After 1.5 hours of ischemia, the contractile force in the hypothermic group was about three times as great as that observed in the room-temperature group. These results indicated that muscle function after a period of totally isolated ischemia is protected by hypothermic preservation. They also support the advisability of storage of amputated parts and free muscle flaps in hypothermic environments before replantation even after relatively brief intervals of ischemia.

Animals↗
PubMed1996

Protective effect of 21-aminosteroid pretreatment in peripheral nerve low-load crush injury in mature and immature rats.

The effects of U-74006F (tirilazad mesylate), a 21-aminosteroid antioxidant, on injured peripheral nerve were studied. Twenty-two immature and 44 mature rats were divided equally into two groups. The experimental group received two injections of 3 mg/kg of U-74006F at a 2 hour interval. The control group received the same volumes of a citrate buffer. A 5 mm segment of the sciatic nerve was subjected to a crush load of 100 g for 2 hours. Motor function (sciatic functional index) was assessed to day 48 postoperatively. There was total paralysis of the crushed limb in all rats the first week after crushing. The experimental group had a statistically significant improvement in motor function compared with the controls on days 14, 21, 25, and 28 for the mature rats and on days 11 and 14 for the immature rats. The mature controls attained complete recovery on day 42 and had a significantly slower recovery rate than the immature controls, which had recovered fully by day 25. The recovery rates were almost similar among mature and immature groups pretreated with U-74006F, both of which had fully recovered motor function by day 28. The results indicate that pretreatment with U-74006F can significantly promote peripheral nerve function after low-load crush injury and that the age of the animal influences the rate of peripheral nerve recovery.

Age Factors↗
PubMed1996

Tumor necrosis factor promotes motor functional recovery in crushed peripheral nerve.

The potential benefits of tumor necrosis factor pretreatment in promoting motor functional recovery of peripheral nerve following low load crush injury were examined. Using a specially designed crush device, rat sciatic nerve was subjected to a low load crush injury of 2-h duration. Recombinant murine tumor necrosis factor and saline were intraperitoneally injected into the experimental and control animals, respectively, prior to nerve crushing. Subsequent motor function was evaluated at intervals by measurement of the sciatic functional index. There was significantly (P < 0.05 to < 0.01) more rapid recovery in the tumor necrosis factor pretreated group as compared to the controls between day 14 and day 28. The sciatic functional index in the tumor necrosis factor group improved to -69.3 +/- 5.3 at day 14 and to nearly normal at day 21. In contrast, the sciatic functional index in the control group was -95.5 +/- 3.1% at day 14 and did not approach normal until day 42. Histological results paralleled the functional findings. The results suggest that tumor necrosis factor pretreatment has the potential to attenuate neurostructural damage and promote motor functional recovery in rat peripheral nerve.

Animals↗
PubMed1996

A surgical guide for identifying the lateral femoral circumflex vessels during free vascularized fibular transfer for avascular necrosis of the femoral head.

Free vascularized fibular transfer for avascular necrosis of the femoral head was developed in an attempt to preserve, rather than replace, the femoral head. In this procedure, the peroneal vessels of the autogenous fibular graft are anastomosed to recipient branches of the lateral femoral circumflex vessels. A problem with this procedure has been the difficulty in locating the lateral femoral circumflex vessels. An anatomic and surgical study was conducted to seek a consistent anatomic landmark for use in isolating these vessels. Ten cadaveric and 29 surgical hip dissections were performed. A falx, or fascial band, was consistently found approximately 10 cm distal to the anterior superior iliac spine; it is attached to the anterior intertrochanteric line of the proximal femur, with additional attachments to the investing fascia of the tensor fascia lata and rectus femoris muscles. Cautious release of this falx from superficial to deep leads to the fat layer surrounding the lateral femoral circumflex vessels. This study has shown that an anatomic landmark exists, which consistently leads to location of the lateral femoral circumflex vessels during a free vascularized fibular transfer. By incorporating the use of this landmark ito the authors' surgical technique, they have significantly reduced surgical dissection time and have provided a safe method for isolating the recipient vessels during this challenging operation.

Angiography↗
PubMed1996

Thrombosis and thrombolysis in crushed arteries with or without anastomosis: a new microvascular thrombosis model.

This study introduces a new rat thrombosis model in which a 2-mm segment of femoral artery is crushed by an impact load. Ninety-five femoral arteries were divided into five groups. The vessels in Groups I and 2 underwent only crush injuries with a 15-kg and 25-kg load, respectively. Group 3 vessels were not crushed, but did undergo vessel anastomosis by a standard microsurgical technique. The vessels in Groups 4 and 5 were crushed by a 25-kg load, and then divided and anastomosed. During the procedure, the vessel lumina were topically irrigated with saline (Group 4) or heparin solution (Group 5). Thrombosis and thrombolysis were evaluated at set time points up to 56 days after operation. While all vessels in Groups 1 and 3 remained patent, the rate of occlusive thrombus formation in Group 2 significantly (p < 0.001) dropped from 85 percent at day 1 to 11 percent at day 7. The intima and media in Groups 4 and 5 were severely disrupted and often occluded the lumen, Group 5 had a significantly (p < 0.01 to 0.001) lower rate of occlusive thrombus formation (40 to 45 percent) at days 1 and 7 than Group 4 (90 percent). Histology in Groups 2, 4, and 5 at day 1 showed no intimnal and almost no medial tissue left in the crushed area. The adventitia and remaining external elastic lamina were adherent to thrombus in the occluded vessels or covered by fibrin and platelet mesh in the patent vessels. The results documented that spontaneous thrombolysis occurs in thrombosed arteries following crush injury alone, but not in thrombosed arteries after crush injury followed by suture anastomoses. The degree of disruption of the internal elastic lamina and the presence of sutures appear to contribute to occlusive thrombus formation following crush injury and anastomoses. Topical irrigation with heparin solution, at the concentration routinely used clinically, significantly reduces the thrombosis rate at the anastomosis site in crushed vessels, but does not promote thrombolysis.

Anastomosis, Surgical↗
PubMed1996

Donor-site morbidity with use of vascularized autogenous fibular grafts.

One hundred and ninety-eight consecutive patients (247 vascularized fibular grafts) were studied to determine the prevalence of morbidity at the donor site after the grafts had been obtained. Objective motor weakness, subjective discomfort in the ankle and other sites in the leg, and sensory abnormalities in the lower limb (or limbs) from which the graft had been obtained were recorded. The average duration of follow-up was forty-seven months (range, twenty-four to 144 months). Kaplan-Meier analysis was used to estimate the prevalence of each finding for the entire cohort over time. Forty-seven (19.0 per cent) of the 247 lower limbs had at least one of the findings, and eighteen(24.3 percent) of the seventy-four limbs for which data were available at five years or more had findings at that time. Twenty-five (10.1 per cent) of the 247 limbs had evidence of motor weakness at three months postoperatively, although no limb had this finding subsequently. At five years or more postoperatively, the prevalence had decreased to two (2.7 per cent) of the seventy-four limbs. Twelve (4.9 per cent) of the 247 limbs had sensory deficits at three months; this increased to 11.8 per cent (95 per cent confidence interval, 7.7 to 17.7 per cent), according to the Kaplan-Meier analysis, at five years. Pain at sites other than the ankle was noted in nine (3.6 per cent) of the 247 limbs at three months and in 8.9 per cent (95 per cent confidence interval, 5.5 to 14.1 per cent), according to the Kaplan-Meier analysis, at five years. The prevalence of pain in the ankle also increased with time, from four (1.6 per cent) of the 247 limbs at three months to 11.5 per cent (95 per cent confidence interval, 7.4 to 17.6 per cent), according to the Kaplan-Meier analysis, at five years. Removal of a vascularized portion of the fibula is associated with a low prevalence of motor weakness and sensory deficits in the foot. The prevalence of pain in the ankle and lower limb increases with time, with some patients having a late onset of the symptoms. While free vascularized fibular grafts remain ideal for many applications, the morbidity must be weighed against the benefits.

Adolescent↗
PubMed1996

Complications of nonoperative and operative treatment of carpal tunnel syndrome.

The popularity of treatment of carpal tunnel syndrome has resulted in a significant number of complications. A rational plan of therapy is available for each category of complications of carpal tunnel syndrome. This article presents 14 of the most frequently encountered complications of treatment. Prevention and management of these complications are discussed.

Adrenal Cortex Hormones↗
PubMed1996

Load tolerance of tibial plateau depressions reinforced with a cluster of K-wires.

The efficacy of subchondral Kirschner wires in enhancing load tolerance of the tibial plateau articular cartilage was examined in a biomechanical study of cadaveric tibias. Seven patterns of K-wires were evaluated under axial loading equivalent to the maximum loading of the knee during normal gait. Subchondral K-wire reinforcement of tibial plateau depressions significantly enhanced load tolerance. This suggests that a subchondral cluster of K-wires in the treatment of tibial plateau fractures may protect the articular cartilage from the loss of reduction resulting from the forces applied to the knee during non-weight-bearing motion.

Analysis of Variance↗
PubMed1995

Effects of enoxaparin, standard heparin, and streptokinase on the patency of anastomoses in severely crushed arteries.

The effects of topical irrigation with three antithrombotic agents on the patency of anastomosed arteries following crush injury were examined. Following an impact crush injury with a 25 kg crush load, the femoral arteries of rats were divided and then anastomosed. During anastomoses, the vessel lumina were topically irrigated with saline, streptokinase, standard heparin, or enoxaparin (a low molecular weight heparin). The results were evaluated by patency test and histology up to day 56. The thrombosis rate at days 1 and 7 was statistically lower (P < 0.05) in the standard heparin and the enoxaparin groups than in the other two groups. The difference between the standard heparin and the enoxaparin groups was not statistically significant. Histology at day 1 showed that thrombus in the occluded vessels adhered to the exposed adventitia in the crushed area or the adventitia was covered by fibrin, red blood cells, and platelet mesh in the patent vessels. The results showed that 1) topical irrigation with standard heparin or enoxaparin solution significantly reduced the thrombosis rate at the anastomosis site of the crushed arteries; and 2) enoxaparin was as effective an antithrombotic agent as standard heparin when topically applied during microvascular anastomoses.

Administration, Topical↗
PubMed1995

Efficacy of recombinant human manganese superoxide dismutase compared to allopurinol in protection of ischemic skeletal muscle against "no-reflow".

A growing body of experimental data indicates that the "no-reflow" phenomenon is a type of reperfusion injury in skeletal muscle which may, in part, be mediated by oxygen free radicals, and thus may be attenuated by using agents that scavenge or inhibit formation of these reactive oxygen metabolites. This study was undertaken to assess the efficacy of recombinant human manganese superoxide dismutase (rhMnSOD) in reducing reperfusion injury in skeletal muscle. The specific advantage of this agent over other SOD types is a much longer plasma half-life (5 to 7 hr), allowing better equilibration between extra- and intracellular compartments. The rat cremaster model was used to study "no-reflow" in skeletal muscle. Reperfusion injury in the muscle was assessed by fluorescein dye perfusion, myocyte creatine phosphokinase (CPK) release, and contractile function in response to electrical field stimulation. Compared with untreated saline control animals, those treated with rhMnSOD after 5 hr of cremasteric ischemia, had a significantly higher percentage area of blood reflow (78 percent +/- 6 percent of normal), a greater percentage tetanic (66 percent +/- 9 percent of normal) and twitch (56 percent +/- 9 percent of normal) contractile strength, and less CPK release (21.5 percent higher than pre-reperfusion baseline CPK levels) (p < 0.05). Untreated saline control CPK release (21.5 percent higher than the prereperfusion level. Animals treated with allopurinol also had a significantly higher percentage twitch contraction (47 percent +/- 14 percent of normal) and a lower CPK release (11.1 percent of the prereperfusion value) 45 min after reperfusion than untreated saline controls.(ABSTRACT TRUNCATED AT 250 WORDS)

Abdominal Muscles↗
PubMed1995

Treatment of osteonecrosis of the femoral head with free vascularized fibular grafting. A long-term follow-up study of one hundred and three hips.

The results for 103 consecutive hips (eighty-nine patients) that had been treated with free vascularized fibular grafting because of symptomatic osteonecrosis of the femoral head were reviewed in a prospective study. The disease was associated with consumption of alcohol in 30 percent of the hips, use of steroids in 17 percent, trauma in 13 percent, and Perthes disease in 3 percent; in the remaining 38 percent, the condition was idiopathic. All patients, except for one who died of unrelated causes 4.5 years after the operation, were followed for at least five years. By the time of the most recent follow-up evaluation, a total arthroplasty had been performed in thirty-one hips: two of the nineteen that were in stage II, according to the criteria of Marcus et al., at the time of the operation; five (23 percent) of the twenty-two that were in stage III; seventeen (43 percent) of the forty that were in stage IV; and seven (32 percent) of the twenty-two that were in stage V. Kaplan-Meier survivorship analyses demonstrated that the probability of conversion to a total hip arthroplasty within five years after free vascularized fibular grafting was 11 percent for the stage-II hips, 23 percent for the stage-III hips, 29 percent for the stage-IV hips, and 27 percent for the stage-V hips. There was a trend toward a lower rate of conversion to a total hip arthroplasty in patients who were less than thirty years old, but this difference did not reach significance (p = 0.06). No association was found between a causative factor and the probability of conversion to a total hip arthroplasty. The average Harris hip scores had improved at the latest follow-up evaluation, compared with the preoperative values (p < 0.001). For the stage-II hips, the average score improved from 56 to 80 points; for the stage-III hips, from 52 to 85 points; for the stage-IV hips, from 41 to 76 points; and for the stage-V hips, from 36 to 75 points. An outcome questionnaire, completed for 73 percent of the hips, revealed that 59 per cent of the hips that had not been subsequently treated with an arthroplasty did not limit or only slightly limited the patient's ability to carry out daily activities, and 62 percent did not limit or only slightly limited the patient's ability to work.(ABSTRACT TRUNCATED AT 400 WORDS)

Adolescent↗
PubMed1995

Outcomes in surgical treatment of femoral neck fracture: analysis of failures secondary to osteonecrosis.

We analyzed failures of surgical treatment of femoral neck fractures due to osteonecrosis in a consecutive series of 26 patients with an average age of 31 (range, 10 to 49 years). These patients were referred for treatment of osteonecrosis that developed after internal fixation of a fracture of the femoral neck. The average Harris hip score at the time of referral was 59. The length of time from fracture treatment to the development of osteonecrosis averaged 22.5 months (range, 5 months to 13 years). All patients were symptomatic at the time of presentation. Internal fixation used at the time of the initial trauma included a variety of cannulated and noncannulated screws and sliding hip screws. Of the 27 fractures, 7 (26%) were nondisplaced, 20 (74%) were displaced, and 2 (7%) were open and displaced. Fifteen patients had previously had removal of hardware, making magnetic resonance imaging of the femoral head possible. Of those patients, 2 had involvement of 25% or less of the femoral head, 7 had involvement of 25% to 50%, 5 had involvement of 50% to 75%, and 1 patient appeared to have complete involvement of the femoral head. Among the displaced fractures, 30% (6/20) had a radiographically evident malreduction. Radiographs were adequate for evaluation of hardware placement in 78% (21/27) of the fractures. Central placement of the hardware was noted in only 9% (2/21). Superolateral positioning of the hardware within the femoral head was most frequently noted.

Adolescent↗
PubMed1995

Pathophysiology and related studies of the no reflow phenomenon in skeletal muscle.

Although the success rate of microvascular replantation and revascularization procedures has increased steadily since the 1960s, some replanted tissues do not reperfuse despite technically adequate arterial anastomoses. This failure of microvascular perfusion is termed no reflow. Much research has been directed toward discovering the etiology of no reflow since it was first described 25 years ago. Three pathophysiologic processes have been identified as playing a central role in the development of no reflow: intracellular calcium overload, oxygen-free radical medicated damage, and altered arachidonic acid metabolism. The first tissue believed to be injured irreversibly by these processes is the endothelium, which leads to dysfunction of the parenchymal cells. All 3 pathways are interrelated extensively, which allows for pharmacologic intervention at many different steps. Agents that have been shown to be beneficial in preventing no reflow include calcium channel blockers, prostaglandin analogs, thromboxane synthesis inhibitors, vasodilators, thrombolytics, and many antioxidants. Although they have been shown to be effective in various laboratory models, additional investigation is necessary before these treatments can be established in clinical use.

Animals↗
PubMed1995

The effect of exposure time on microsurgical anastomoses of experimentally crushed arteries.

Replantation after crushing amputation has a relatively low success rate. Although the mechanism of trauma is a major factor in failure, the time lapse before vessel anastomosis may also be a contributing factor. In this study, we observed the influence of the interval between vessel injury and surgical treatment on thrombus formation and healing after controlled crushing. Seventy-five Sprague-Dawley rats were used. A segment of femoral artery was clamped to create warm ischemia for 8 hours and crushed with a 15 kg load for one hour. After the loading device was removed the crushed segments were transected and the vessel ends exposed to the adjacent tissues and blood for 0, 2, 4 and 6 hours (groups II-V, respectively) prior to being anastomosed with standard microsurgical technique. The vessel samples were harvested at days 1, 2 and 7, respectively, and evaluated by light microscopy and scanning electron microscopy (SEM). The patency rate of the anastomoses was 97.3% at harvest and reendothelialization was completed at day 7. Three anastomoses with 4 or 6 hours exposure showed thrombosis, or clotting. The results indicated that up to 6 hours exposure time did not have a significant influence on thrombus formation or the healing process of vessels under the controlled conditions of this study.

Anastomosis, Surgical↗