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Biomedical subjects

Suzanne L Miller

Publications and source records attributed to Suzanne L Miller.

16 recordsLinked to original sources
PubMed2007

The proximal origin of the hamstrings and surrounding anatomy encountered during repair. A cadaveric study.

BACKGROUND: Avulsion of the proximal origin of the hamstrings has become a more frequently recognized athletic injury. Most orthopaedic surgeons rarely operate in this anatomic area. The purpose of the present study was to define the anatomy of the proximal origin of the hamstrings and its relationship to neurovascular and muscular structures encountered during a repair of a complete avulsion. METHODS: Fourteen fresh-frozen hip-to-foot human cadaveric specimens were dissected in the prone position. The proximal origin of the hamstrings and its relationship to the surrounding neurologic and muscular structures were documented and measured with use of digital calipers. RESULTS: Six of the fourteen specimens were from female donors. The average age of the donors at the time of death was 68 +/- 13 years. The average height of the donors was 66 +/- 3.5 in (167 +/- 8.9 cm), and the average weight was 142 +/- 39 lb (64 +/- 17.7 kg). The semitendinosus and biceps femoris have a common tendinous site of origin on the ischium. A number of measurements were obtained. The musculotendinous junctions of the semitendinosus and biceps femoris separated at an average of 9.9 +/- 1.5 cm from the most proximal origin site on the ischium. The average distance from the proximal border of the semitendinosus/biceps femoris origin to the inferior border of the gluteus maximus was 6.3 +/- 1.3 cm. At the lateral border of the ischium, the average distance from the inferior gluteal nerve and artery to the inferior border of the gluteus maximus was 5.0 +/- 0.8 cm. The sciatic nerve was an average of 1.2 +/- 0.2 cm from the most lateral aspect of the ischial tuberosity. The site of origin of the semitendinosus/biceps femoris was oval, with average measurements of 2.7 +/- 0.5 cm from proximal to distal and of 1.8 +/- 0.2 cm from medial to lateral. The site of origin of the semimembranosus was crescent-shaped, with average measurements of 3.1 +/- 0.3 cm from proximal to distal and of 1.1 +/- 0.5 cm from medial to lateral. CONCLUSIONS: The semitendinosus and biceps femoris have a common tendon of origin on the ischium, and the semimembranosus originates just laterally. The proximal origin of the hamstrings has intimate relationships with the inferior gluteal nerve and artery and the sciatic nerve, which may be at risk during surgical dissection and retraction.

Aged↗
PubMed2006

The effects of maternal betamethasone administration on the intrauterine growth-restricted fetus.

Intrauterine growth restriction (IUGR) is associated with altered fetal cardiovascular function to ensure adequate perfusion of essential organs. IUGR fetuses are at risk of preterm delivery and so are likely to receive antenatal glucocorticoids to promote lung maturation. Because glucocorticoids alter vascular tone, we questioned whether such treatment may induce fetal cardiovascular alterations. Using pregnant sheep carrying twins, we induced IUGR at approximately 0.7 gestation by single umbilical artery ligation in one twin, using the other twin as a control. In each fetus, we monitored carotid blood flow and arterial blood gases. We administered 11.4 mg betamethasone (n = 5) or vehicle (n = 4) to the ewe on d 5 (BM1) and 6 (BM2) postsurgery. On d 7, fetal brains were collected for immunohistochemistry. In control fetuses, carotid blood flow decreased 3.5 h post-BM1 by 24% (P < 0.001), returning to baseline at 5.5 h. In IUGR fetuses, carotid flow decreased 2.5 h post-BM1 by 27% and then increased by 25% over baseline, peaking at 11 h (P < 0.001). Compared to control + saline, we observed a significant increase in oxidative damage (4-hydroxynonenal-positive cells) in the fetal hippocampus and subcallosal area of all treatment groups (IUGR + BM > IUGR + saline = control + BM). There was a significant correlation between carotid blood flow reperfusion after betamethasone and the number of 4-hydroxynonenal-positive cells in the cortex and hippocampus. These data suggest that antenatal betamethasone may induce brain injury in the IUGR fetus but not in the normally grown fetus.

Animals↗
PubMed2006

The role of corticosterone in prehatch-induced memory deficits in chicks.

We have previously shown that prehatch hypoxia (14% oxygen for 24 h), at E10 or E14 of chick embryonic development, produces significant memory deficits, with E10 hypoxia significantly affecting short-term memory and the subsequent formation of long-term memory, whereas E14 hypoxia only affects long-term memory. One of the consequences of hypoxia is the release of stress hormones and we found in this study that hypoxia at E10 or E14 induced a significant increase in circulating corticosterone immediately after the cessation of hypoxia (E11 and E15, respectively). Corticosterone levels remained significantly elevated at hatch in the E14 hypoxia group. This study describes the effect of a single, in ovo, injection of corticosterone on subsequent memory ability in hatched chicks. It was found that corticosterone (0.2 nmol/egg) at E10 or E14 mimicked the memory deficits produced by hypoxia at the same prehatch ages. Embryos treated with corticosterone at E10 had poor short-term memory at hatch, whereas corticosterone administration at E14 resulted in poor long-term memory. Embryos treated with corticosterone at E16 had raised circulating corticosterone levels at hatch, but did not have impaired memory. Treatment with corticosterone at E10, E12, E14 and E16 produced the same cognitive outcomes as hypoxia at the same prehatch ages. However, elevated plasma corticosterone levels at hatch did not necessarily cause the impaired memory processing. Raised levels were observed after treatment at E14 when memory processing was impaired, at E16 when memory was not impaired and not at E10 when memory was impaired. This suggests that an acute rather than sustained increase in plasma corticosterone at particular developmental ages is the cause of impaired memory processing seen at hatch.

Analysis of Variance↗
PubMed2005

Novel method for in vivo hydroxyl radical measurement by microdialysis in fetal sheep brain in utero.

Hydroxyl radical (.OH) is a reactive oxygen species produced during severe hypoxia, asphyxia, or ischemia that can cause cell death resulting in brain damage. Generation of .OH may occur in the fetal brain during asphyxia in utero. The very short half-life of .OH requires use of trapping agents such as salicylic acid or phenylalanine for detection, but their hydroxylated derivatives are either unstable, produced endogenously, or difficult to measure in the small volume of microdialysis samples. In the present study, we used terephthalic acid (TA), hydroxylation of which yields a stable and highly fluorometric isomer (excitation, 326 nm; emission, 432 nm). In vitro studies using .OH generated by the Fenton reaction showed that hydroxylated TA formed quickly (<10 s), was resistant to bleaching (<5% change in fluorescence), and permitted detection of <0.5 pmol .OH. In vivo studies were performed in fetal sheep using microdialysis probes implanted into the parasagittal cortex. The probe was perfused at 2 mul/min with artificial cerebrospinal fluid containing 5 mM TA, and samples were collected every 30 min. Fluorescence measured in 10 mul of dialysate was significantly greater than in the efflux from probes perfused without TA. High-performance liquid chromotography analysis showed that the fluorescence in dialysis samples was entirely due to hydroxylation of TA. Thus this study shows that it is possible to use TA as a trapping agent for detecting low concentrations of .OH both in vitro and in vivo and that low concentrations of .OH are present in fetal brain tissue and fluctuate with time.

Animals↗
PubMed2004

The effect of prenatal hypoxia and malnutrition on memory consolidation in the chick.

The contribution of hypoxia and malnutrition to cognitive impairments was investigated in chicks incubated in conditions of reduced gas exchange. Previous research has shown that reducing gas exchange during incubation by wrapping half the eggshell with an impermeable membrane results in impaired cognitive ability in young chicks. The results were interpreted within a three stage sequential model of memory using discriminated bead avoidance learning. Reducing gas exchange for 4 days from day 10 or 14, of the 21-day incubation, inhibits memory formation and consolidation into permanent storage. The nature of the cognitive deficit depended on the timing of the insult. Environmental hypoxia (14% oxygen), induced from days 10 to 14 and from days 14 to 18, replicated the memory deficits found previously when eggs were partially wrapped with a membrane. Oxygen is necessary to break down food and to provide energy to build tissue proteins, and therefore hypoxia (partial wrapping or environmental incubation) may indirectly cause malnutrition. Malnutrition, induced by removing 5%, 7.5% or 10% albumin from the egg prior to incubation, had no significant effect on memory consolidation. Raised corticosterone levels occurred in chicks malnourished by 5% and 7.5%, but brain sparing was only evident in chicks with 7.5% albumin removal. Hatch rates were very low in 10% malnourished chicks. Using the chick as a model of prenatal stress, we have been able to isolate the effects of hypoxia from contributing maternal factors.

Age Factors↗
PubMed2004

Cardiovascular and endocrine responses to cutaneous electrical stimulation after fentanyl in the ovine fetus.

OBJECTIVE: The purpose of this study was to determine whether physical stimulation is stressful to the ovine fetus, as judged from physiologic changes that are similar to those reported for other stressors (such as hypoxia); whether any stress response could be blocked by clinically used doses of fentanyl; and whether fentanyl alone had any potentially deleterious physiologic effects in the fetus. STUDY DESIGN: We investigated the effect of fentanyl analgesia on the cardiovascular and endocrine response to cutaneous electrical stimulation in the late gestation (>125 days) ovine fetus (n=7 fetuses). Chronically implanted catheters and blood flow probes were used to measure fetal arterial blood pressure, heart rate, carotid and femoral blood flow, pH, Po(2), Pco(2), lactate, cortisol, and beta-endorphin levels before, during, and for 1 hour after 5 minutes of cutaneous electrical stimulation to the lip, forelimb, and abdomen, in a crossover design. Clinically used 30 or 150 microg doses of fentanyl (which approximated 10 or 50 microg/kg estimated fetal weight) or saline solution were given intravenously to the fetus 2 minutes before stimulation. RESULTS: When compared with the control, stimulation caused a significant rise in fetal heart rate (P=.003; mean maximal rise, 48.6+/-14.0 beats/min, 0-10 minutes after the start of stimulation) but caused no change in any other parameters studied. Neither dose of fentanyl attenuated the changes in heart rate that were observed in response to stimulation alone. Fentanyl alone significantly increased fetal heart rate, carotid blood flow, and lactate and cortisol levels and significantly decreased pH and Po(2). CONCLUSION: Cutaneous electrical stimulation in the fetal sheep causes an increase in heart rate, which fentanyl does not block. Fentanyl itself has significant effects on the cardiovascular and endocrine system, which might adversely affect the fetus.

Analgesics, Opioid↗
PubMed2004

Hypoxia induced activin secretion by the fetoplacental unit: differential responses related to gestation.

OBJECTIVE: To determine whether activin A levels reflect oxygen availability in basal and hypoxic conditions in the late pregnant fetus and newborn lamb. DESIGN: In vivo animal experimental study. SETTING: Department of Physiology, Monash University. POPULATION: Chronically catheterised fetal sheep in late gestation. METHODS: Fetal hypoxia was induced at 125 (n = 4), 135 (n = 4) or 145 days ('term'; n = 3) gestational age by maternal nitrogen exposure, for 4 hours, during which maternal and fetal arterial, and amniotic fluid samples were collected. Lambs (age one, five and eight days; n = 3) were exposed to 1 hour of hypoxia via nitrogen exposure. MAIN OUTCOME MEASURES: Activin A, prostaglandin E2 (PGE2) and cortisol were analysed in plasma and amniotic fluid, and whole blood was used to determine Pao2, Paco2, %O2, lactate and pH. RESULTS: Basal activin A concentrations in the fetal arterial circulation remained unchanged between 125 days (0.230 [0.10] ng/mL) and term (0.28 [0.10] ng/mL), as did fetal oxygen saturation (59.11% [4.74%] to 52.25% [4.84%]) and pH (7.35 [0.02] to 7.37 [0.02]). Moderate fetal hypoxia (50% fall in fetal arterial %O2) produced a significant increase in circulating activin A (2.05 [0.67] ng/mL) and a significant decrease in pH (7.27 [0.03]) at 125 days of gestation, however, at 135 and 145 days, activin A and pH remained unchanged. Fetal activin A concentration was significantly correlated with pH (P = 0.036) but not %O2 (P = 0.072). Hypoxia in the lambs did not alter circulating activin A. CONCLUSIONS: In response to hypoxia, activin A is increased in the circulation of 125-day-old fetuses, but not in older fetuses. Fetal arterial activin A levels sensitively reflect pH but not oxygen saturation, with increasing activin A in conditions of metabolic acidosis.

Activins↗
PubMed2003

Magnetic resonance proton spectroscopy and diffusion weighted imaging of chick embryo brain in ovo.

Metabolic compensatory mechanisms may partly account for the decreased vulnerability to hypoxia observed in the developing brain. We used proton magnetic resonance spectroscopy and diffusion-weighted imaging to measure the cerebral concentrations of lactate and other metabolites, as well as the apparent diffusion coefficient (ADC) of tissue water, before, during and after hypoxia in anaesthetised chick embryos in ovo. Reducing the inspired oxygen concentration to 8% for 40 min caused a significant rise in both mean (+/-S.D.) lactate:creatine and alanine:creatine ratios from 0.58 (0.41) to 1.56 (0.56) and 0.14 (0.14) to 0.29 (0.17), respectively. Under similar hypoxic conditions, ADC did not change from a mean baseline value of 0.95 (0.09), but did fall to 0.40 (0.12) x 10(9) mm(2) s(-1) with further stepwise reductions in oxygenation. Moderate hypoxia increases lactate concentration in the developing chick brain without compromising cellular energy metabolism.

Adaptation, Physiological↗
PubMed2003

Anatomy of the posterior rotator interval: implications for cuff mobilization.

Release of the posterior rotator interval between the supraspinatus and infraspinatus tendons may be necessary to obtain appropriate mobilization for an anatomic rotator cuff repair. Ten cadaver shoulders were dissected to expose the region between the infraspinatus and supraspinatus from the spinoglenoid notch to the greater tuberosity. Measurements were made from the spinoglenoid notch to the glenoid rim, the glenoid rim to the confluence of the supraspinatus and infraspinatus musculotendinous junction, and from the confluence of the tendons to the insertion on the humerus. The histologic features of the posterior rotator interval were examined. The posterior rotator interval is a clear structure, consisting of the glenohumeral capsule medially, which fuses with the supraspinatus and infraspinatus tendons laterally. The average length of the posterior rotator interval was 77.8 mm which includes the distance from the spinoglenoid notch to the glenoid rim (25 mm; standard deviation, 2.89 mm; range, 21-28 mm), from the glenoid to the tendon confluence (25 mm; standard deviation, 1.95 mm; range, 21-28 mm), and from the tendon confluence to insertion (28 mm; standard deviation, 2.36 mm; range, 24-31 mm). Release of the posterior rotator interval can be important to realign the supraspinatus tendon if it is retracted and scarred at its posterior edge.

Arthroscopy↗
PubMed2002

Graft selection in anterior cruciate ligament reconstruction.

Selecting the appropriate graft for ACL reconstruction depends on numerous factors including surgeon philosophy and experience, tissue availability (affected by anatomical anomalies or prior injury or surgery), and patient activity level and desires. Although the patella tendon autograft has the widest experience in the literature, and is probably the most commonly used graft source, this must be tempered with the higher reported incidences of potential morbidity and pitfalls associated with its use. The hamstring tendons are gaining increasing popularity, mostly due to reduced harvest morbidity and improved soft tissue fixation techniques, and many recent studies in the literature report equal results to BTB ACL reconstruction with respect to functional outcome and patient satisfaction. On the other hand, many of these studies report higher degrees of instrument (KT-100) tested laxity for hamstring reconstruction, and some have reported lower returns to preinjury levels of activity. One question that remains to be addressed is how closely objectively measured laxity tests correlate with subjectively assessed outcomes and ability to return to high levels of competitive sports. Allograft use, which decreased in popularity during the 1990s, appears to be undergoing a resurgence, with better sterilization processes and new graft sources (tibialis tendons), leading to increased availability and improved fixation techniques. The benefits of decreased surgical morbidity and easier rehabilitation must be weighed against the potential for greater failure of biologic incorporation, infection, and possibly slower return to activities. In our practice, for high-demand individuals (those playing cutting, pivoting, or jumping sports and skiing) BTB tends to be the graft of choice. For lower demand or older individuals, hamstring reconstructions will be performed. Allograft tissue will be used in older individuals (generally over 45 years old), those with signs of arthritis (and compelling evidence of instability), or those individuals who understand the pros and cons of allograft use fully and do not want their own tissue used.

Anterior Cruciate Ligament Injuries↗
PubMed2002

Effects of chronic hypoxia and protein malnutrition on growth in the developing chick.

OBJECTIVE: The purpose of this study was to determine how chronic hypoxia and/or protein malnutrition in ovo affect growth in developing chicks. STUDY DESIGN: Chicken eggs were incubated under normoxic (21% oxygen; n = 30 eggs) or hypoxic (14% oxygen; n = 80 eggs) conditions. Hypoxia was imposed from day 0 (n = 38 eggs), day 10 (n = 22 eggs), or from day 0 to 10 (n = 20 eggs). Protein malnutrition alone (n = 20 eggs) or in combination with hypoxia (n = 24 eggs) was induced by removal of 10% of the estimated total albumin content of the egg. Embryos/chicks were killed and weighed at day 10, 15, or immediately after hatch; organs were removed and weighed. RESULTS: Embryos to which hypoxia was imposed from day 0 weighed less than control embryos at day 10, which stayed the same until hatch (64.67% +/- 3.56% egg mass vs 69.36% +/- 3.90% [mean +/- SD]; P <.05). Malnourished chicks at day 15 and at hatch (63.42% +/- 4.28%; P <.05) weighed less than control chicks, as did malnourished plus hypoxia chicks (59.74% +/- 3.41%; P <.001). Malnourished plus hypoxia chicks weighed less than malnourished chicks alone (P <.05). Embryos that were hypoxic from day 0 to 10 weighed less than control embryos at day 15 (P <.05), but not at hatch. At hatch, neither hypoxia nor malnutrition decreased crown-rump length. Brain and heart weights were increased in both malnourished groups, but not chicks that were hypoxic from day 0. CONCLUSION: Chick embryos exposed to malnutrition show asymmetric growth restriction with relative sparing of the brain and heart. Early growth restriction that was induced by hypoxia from the beginning of incubation is reversed by the restoration of normoxia at mid incubation.

Animals↗
PubMed2002

Comparison of intra-articular lidocaine and intravenous sedation for reduction of shoulder dislocations: a randomized, prospective study.

BACKGROUND: Acute anterior glenohumeral dislocations have been commonly treated with closed reduction and the use of intravenous sedation. Recently, the use of intra-articular lidocaine has been advocated as an alternative to sedation, since intravenous access and patient monitoring are not required. The purpose of this study was to evaluate the value of local anesthesia compared with that of the commonly used intravenous sedation during the performance of a standardized reduction technique. METHODS: In a prospective, randomized study, skeletally mature patients with an isolated glenohumeral joint dislocation and no associated fracture were randomized to receive either intravenous sedation or intra-articular lidocaine to facilitate reduction of the dislocation. Reduction was performed with the modified Stimson method. The two groups were compared with regard to the rate of successful reduction, pain as rated on a visual analog scale, time required for the reduction, time from the reduction until discharge from the emergency department, and cost. RESULTS: Thirty patients were enrolled in the study. Five (two in the lidocaine group and three in the sedation group) required scapular manipulation in addition to the Stimson technique to reduce the dislocation. The lidocaine group spent significantly less time in the emergency department (average time, seventy-five minutes compared with 185 minutes in the sedation group, p < 0.01). There was no significant difference between the two groups with regard to pain (p = 0.37), success of the Stimson technique (p = 1.00), or time required to reduce the shoulder (p = 0.42). The cost of the intravenous sedation was $97.64 per patient compared with $0.52 for use of the intra-articular lidocaine. CONCLUSIONS: Use of intra-articular lidocaine to facilitate reduction with the Stimson technique is a safe and effective method for treating acute shoulder dislocations in an emergency room setting. Intra-articular lidocaine requires less money, time, and nursing resources than does intravenous sedation to facilitate reduction with the Stimson technique.

Adolescent↗
PubMed2002

Failed surgical management of partial thickness rotator cuff tears.

Some authors have recommended that rotator cuff tears <50% of tendon thickness be debrided and those involving >50% of the tendon be treated with miniopen repair. We hypothesize that if indications for selecting between simple debridement and tendon repair were appropriate, then both groups should have comparable outcomes. Thirty-nine patients with partial rotator cuff tears met inclusion criteria and were available for retrospective analysis. Twenty-six percent of patients who underwent debridement and 12.5% of patients who had mini-open repair had unsatisfactory results according to Neer's criteria.

Adult↗
PubMedDate not supplied

Loss of subscapularis function after total shoulder replacement: A seldom recognized problem.

Little attention has focused on subscapularis integrity after total shoulder replacement (TSR). We have noted that several patients have loss of internal rotation and subscapularis function on follow-up, leading to our review of success in restoring subscapularis function after TSR. A retrospective review was done of the records of 41 patients after TSR performed between 1995 and 2000. Mean follow-up was 1.9 years. Terminal internal rotation was evaluated by the lift-off and belly-press examinations. Subscapularis function was assessed by the patients' ability to tuck in a shirt. The subscapularis was repaired anatomically in 9 cases and through bone tunnels in 32 patients. Abnormal results were found for 25 of 37 lift-off examinations (67.5%) and 24 of 36 belly-press examinations (66.6%). Of 25 patients with an abnormal lift-off finding, 92% reported reduced subscapularis function (Fisher exact test, P <.01). Despite meticulous attention to subscapularis repair, suboptimal return of function was found on clinical examination and assessment of activities of daily living.

Aged↗
PubMedDate not supplied

Melatonin provides neuroprotection in the late-gestation fetal sheep brain in response to umbilical cord occlusion.

Oxygen free radicals, including the highly toxic hydroxyl radical (*OH), initiate lipid peroxidation and DNA/RNA fragmentation and damage cells. The pineal hormone melatonin is an antioxidant and powerful scavenger of *OH. We hypothesized that maternally administered melatonin could reduce *OH formation, lipid peroxidation, and DNA/RNA damage in the fetal brain in response to asphyxia. In 15 fetal sheep, extracellular *OH was measured by microdialysis in white and gray matter of the parasagittal cortex. In 10 fetuses, asphyxia was induced by umbilical cord occlusion for 10 min using an inflatable cuff - the ewes of these fetuses received either intravenous melatonin (1 mg bolus, then 1 mg/h for 2 h; n = 5) or vehicle (1% ethanol in saline; n = 5), and results were compared to fetuses with sham cord occlusion and vehicle-infused ewes (n = 5). Hypoxemia, acidemia, hypertension and bradycardia produced by cord occlusion was similar in the melatonin- and vehicle-treated groups. In the vehicle-treated group, cord occlusion resulted in a significant increase in *OH in gray matter at 8-9.5 h after occlusion (p < 0.05); in contrast, there was no *OH change in the melatonin-treated group. After cord occlusion, lipid peroxidation (4-hydroxynonenal immunoreactivity) found throughout the brain of vehicle-infused ewes was significantly less in the melatonin-infused group. Melatonin had no significant effect on the distribution of DNA/RNA fragmentation, as shown by 8-hydroxydeoxyguanosine immunoreactivity. Thus, brief asphyxia results in significant and delayed entry of *OH into the extracellular space of cortical gray matter in the fetal sheep brain, and melatonin given to the mother at the time of the insult abrogates this increase. Melatonin, in reducing O2 free radical production, may be an effective neuroprotective treatment for the fetus.

Animals↗