Search PubMed⌕ Search

Biomedical subjects

H J Sommer

Publications and source records attributed to H J Sommer.

At least 19 recordsLinked to original sources
PubMed2006

Superquadric modeling of cranial and cerebral shape and asymmetry.

A new method for quantifying cranial and cerebral shape and asymmetry fits symmetric superquadric geometric models to three-dimensional coordinate measurements. Asymmetry is quantified as radial residuals of the surface data points from their best-fit superquadric models. Twenty human crania, 10 magnetic resonance imaging (MRI) exocranial surfaces, and 10 corresponding MRI cerebral surfaces as well as two infant head casts were digitized and modeled using superquadrics. Superquadric parameters have simple geometric interpretation, are very reproducible, and demonstrated statistically significant differences between crania of Amerindian ancestry and MRI exocranial surfaces of European ancestry used in this study. Superquadric models demonstrated strong congruence between MRI exocranial and cerebral surfaces. Typical asymmetry was 1-5 mm. Lastly, polar contour plots of radial residuals for head casts before and after orthotic cranioplasty demonstrated the efficacy of using superquadrics to quantify positional plagiocephaly and synostosis of infant crania.

American Indian or Alaska Native↗
PubMed2005

Simplified overturn stability monitoring of agricultural tractors.

Agricultural tractors are the most common source of farm work fatalities in the U.S., with overturns the most common type of incident. For the year 2001, there were 15 tractor-related fatalities in Pennsylvania, 9 of which were due to tractor rollover. A new device using low-cost sensors and microcomputers was developed around a simplified mathematical model of an agricultural tractor to inform the operator of potential tractor instability. This device communicates the current rollover potential, along with a recent history of rollover potential, to the operator of the tractor via a simple bar-graph display. The device uses a single-chip accelerometer to sense the current rollover potential and a small microprocessor to analyze the accelerometer data, compensate for variations due to temperature, and then send this information to a visual display. The use of these low-cost "off the shelf" components enabled the fabrication of a very inexpensive sensor system. Because agricultural tractors have a long service life, it was important to make the device low cost and flexible. This could enable it to be sold as an aftermarket add-on for a variety of tractor models. The device is also capable of interfacing with newer on-board tractor systems via a CAN bus to make it more attractive to tractor manufacturers who may want to incorporate this device into new models. Work is continuing on the development of an improved display to inform the tractor operator of possible instability, including display ergonomic studies, investigation of threshold levels for alerting an operator of potential instability, and investigation into audible warning signals.

Accident Prevention↗
PubMed1999

Anesthesiology and intensive care during epilepsy surgery in children and adolescents.

Thus far there are no known studies of the management of anesthesiology and intensive care in cases of implantation of subdural plates for the purpose of determining the epileptogenic areal and of subsequent epilepsy surgery. Such operative measures are still considered too risky, especially in the case of small children. The authors report on cases of 45 children and adolescents who underwent this kind of surgery between December 1992 and December 1997 in Gilead hospital. In order to judge the anesthesiological risk the children were divided into three age groups: A, 1-5 years (n = 12); B, 6-11 years (n = 14); C, 12-18 years (n = 19). In none of these groups were there complications which in retrospect would have shed a negative light on the operation.

Adjuvants, Anesthesia↗
PubMed1999

Evaluation of a Treadmill with Vibration Isolation and Stabilization (TVIS) for use on the International Space Station.

A treadmill with vibration isolation and stabilization designed for the International Space Station (ISS) was evaluated during Shuttle mission STS-81. Three crew members ran and walked on the device, which floats freely in zero gravity. For the majority of the more than 2 hours of locomotion studied, the treadmill showed peak to peak linear and angular displacements of less than 2.5 cm and 2.5 degrees, respectively. Vibration transmitted to the vehicle was within the microgravity allocation limits that are defined for the ISS. Refinements to the treadmill and harness system are discussed. This approach to treadmill design offers the possibility of generating 1G-like loads on the lower extremities while preserving the microgravity environment of the ISS for structural safety and vibration free experimental conditions.

Equipment Design↗
PubMed1998

A three-dimensional musculoskeletal database for the lower extremities.

A three-dimensional musculoskeletal database of the lower extremities has been developed for use in human musculoskeletal models. The locations of idealized muscle attachments on the pelvis, both femurs, both tibias and fibulas, and both feet were accurately digitized for 52 dried skeletal specimens. The mean specimen heights were 177.5 cm (male) and 166.2 cm (female) and the mean specimen age at the time of death was 48.8 yr. Statistical accumulation and scaling techniques were used to generate highly representative normative models, which were divided into groups and tested for differences based on gender and race. From the test results, the pelvis was divided into a male model (RMS = 8.6 mm), a black female model (RMS = 7.0 mm) and a white female model (RMS = 7.3 mm). The foot was separated into black (RMS = 3.7 mm) and white models (RMS = 3.6 mm). Single models were used for the femur (RMS = 6.5 mm) and the tibia/fibula (RMS = 3.7). Containing over 12000 anatomical landmarks digitized from 52 dried skeletons, this study represents an improvement over previous databases by an order of magnitude.

Black People↗
PubMed1998

Cost analysis of hospital material management systems.

Integrated healthcare material management begins with manufactures of medical/surgical supplies, uses distributors and ends at the point of use at hospitals. Recent material management philosophies in the healthcare industry, such as just-in-time and stockless systems, are yet to be fully evaluated. In order to evaluate the cost effectiveness of each type of material management technique, a cost model for hospital materials management has been designed. Several case scenarios are analyzed and results are reported.

Cost Savings↗
PubMed1996

Ground reaction forces during locomotion in simulated microgravity.

BACKGROUND: Significant losses in bone density and mineral, primarily in the lower extremities, have been reported following exposure to weightlessness. Recent investigations suggest that mechanical influences such as bone deformation and strain rate may be critically important in stimulating new bone formation. HYPOTHESIS: It was hypothesized that velocity, cadence, and harness design would significantly affect lower limb impact forces during treadmill exercise in simulated zero-gravity (0G). METHODS: A ground-based hypogravity simulator was used to investigate which factors affect limb loading during tethered treadmill exercise. A fractional factorial design was used and 12 subjects were studied. RESULTS: The results showed that running on active and passive treadmills in the simulator with a tethering force close to the maximum comfortable level produced similar magnitudes for the peak ground reaction force. It was also found that these maximum forces were significantly lower than those obtained during overground trials, even when the speeds of locomotion in the simulator were 66% greater than those in 1G. Cadence had no effect on any of the response variables. The maximum rate of force application (DFDTmax) was similar for overground running and exercise in simulated 0G, provided the "weightless" subjects ran on a motorized treadmill. CONCLUSIONS: These findings have implications for the use of treadmill exercise as a countermeasure for hypokinetic osteoporosis. As the relationship between mechanical factors and osteogenesis becomes better understood, results from human experiments in 0G simulators will help to design in-flight exercise programs that are more closely targeted to generate appropriate mechanical stimuli.

Adult↗
PubMed1994

Foot inversion-eversion and knee kinematics during walking.

The purpose of this study was to monitor selected aspects of the three-dimensional kinematics of the knee during walking with regular shoes and with modified shoes that induced either pronation or supination of the foot. Steinmann traction pins were inserted into the right tibia and femur of five adult men who had apparently normal lower extremities. Target clusters mounted onto the pins were filmed by four cine cameras operating at 100 frames/sec. Two trials per subject were analyzed for each of the three experimental conditions: regular running shoes, running shoes with a 10 degree valgus wedge, and running shoes with a 10 degree varus wedge. The different types of footwear induced only minor kinematic changes at the knee during the stance phase of walking. The angular patterns of the tibiofemoral joint were modified by less than 1 degree, whereas the translatory patterns were altered by 2 mm. Immediately following foot-strike, the valgus-wedge shoes caused the tibia to rotate internally 4 degrees more than the varus-wedge shoes, but at the tibiofemoral joint no consistent differences in the pattern of internal-external rotation between normal and modified footwear were measureable. These findings suggest that, in the healthy lower extremity, increased internal and external tibial rotation is resolved at the hip joint, with changes at the tibiofemoral joint that barely are detectable with the techniques used in this study.

Adult↗
PubMed1994

Adaptation of the tear film to work in air-conditioned rooms (office-eye syndrome).

To detect mechanisms of tear-film adaptation to a dry climate, we investigated co-workers in our hospital with air-conditioned rooms. Three groups were formed according to the time of occupancy (6 months to 2 years, 2-4 years, and 4-6 years) and were compared with a control group. The number of patients with frequent dry-eye complaints increased up to 48%, reaching a steady state after 2-4 years. The breakup time was slightly reduced (decrease, 17.5%; P < 0.01) and also reached a steady state after 2-4 years. The tear-ferning test, however, showed a highly significant improvement (P < 0.01). A slight reduction in the Schirmer test was found. Our study indicates that improved tear quality is important for adaptation to long-standing increased evaporation of the tear film.

Adaptation, Ocular↗
PubMed1992

Three-dimensional kinematics of the human knee during walking.

Three-dimensional kinematics of the tibiofemoral joint were studied during normal walking. Target markers were fixed to tibia and femur by means of intra-cortical traction pins. Radiographs of the lower limb were obtained to compute the position of the target markers relative to internal anatomical structures. High-speed cine cameras were used to measure three-dimensional coordinates of the target markers in five subjects walking at a speed of 1.2 m s-1. Relative motion between tibia and femur was resolved according to a joint coordinate system (JCS). The measurements have identified that substantial angular and linear motions occur about and along each of the JCS axes during walking. The results do not, however, support the traditional view that the so-called 'screw home' mechanism of the knee joint operates during gait.

Adult↗
PubMed1989

[CT portography in malignant space-occupying lesions of the liver].

CT portography was performed in 32 patients with liver tumours and in four patients with cirrhosis of the liver, but without evidence of tumour, after angiographic injection of contrast into the superior mesenteric or splenic arteries. Compared with CT using no contrast, or contrast by intravenous injection, CT portography has the following advantages: better tumour detection, better detection of tumour size, better demarcation and localisation of tumours, better demonstration of the portal system, more inhomogeneity of the parenchyma. Of 12 patients with a number of tumours shown on CT, CT portography demonstrated tumours in four cases, which could not be shown by any other imaging method. Problems concerning CT portography in patients with cirrhosis of the liver are discussed.

Adult↗
PubMed1989

[Aggressive fibromatosis--a surgical problem disease].

The aggressive fibromatosis is a surgical problem disease. Two remarkable cases serve as examples to demonstrate the aggressive forms of extraabdominal fibromatosis. There is a tendency to locally invasive destructive growth without metastasising at any time and a markedly high relapse rate after surgery, a tendency that showed up clearly in our patients, too. The very multivarious nomenclature points out that about histiogenesis, pathogenesis and benignity of this excrescence still exists great obscurity. We report on the pathology and clinic of an aggressive fibromatosis of the thyroid gland region and of a thoracal aggressive fibromatosis in the right shoulderblade-region.

Adolescent↗
PubMed1989

[The subphrenic abscess. Surgical and/or percutaneous drainage].

The results indicate that the low risk percutaneous drainage of subphrenic abscesses is only feasible in carefully selected patients. The surgical intervention remains the method of choice for the drainage of subphrenic abscesses in conditions such as multiple and complicated abscesses, unfavourable access to the abscess cavities or other pathological conditions. An early and decisive diagnosis is crucial for effective treatment of subphrenic abscesses either by percutaneous drainage or surgical intervention and antibiotic therapy.

Adolescent↗
PubMed1987

Histomorphometric changes of osteosarcoma after chemotherapy. Correlation with 99mTc methylene diphosphonate functional imaging.

An investigation to correlate histologic changes in 12 osteosarcoma specimens from patients undergoing chemotherapy was performed using functional images of regional 99mTc methylene diphosphonate (MDP) plasma clearance rates assessed from dynamic bone scintigraphies taken during chemotherapy. Residual tumor cell viability was determined by microscopic examination of multiple thin sections from surgical specimens and quantitated by histomorphometry. Regions that showed decreases in 99mTc MDP plasma clearance of more than 20% were associated with areas of necrotic tumor, and regions that showed absent decline or increasing clearance rates were associated with high residual cell viability and incomplete response to chemotherapy. Therefore, functional bone scintigraphy allows an objective presurgical assessment of tumor response to chemotherapy.

Adolescent↗
PubMed1987

[Hyperlactacidemia in intestinal ischemia. I. Theoretical considerations].

Acute interruption of the blood flow of the bowel is a very severe disease. The very high lethality mainly depends on the difficulties in diagnosis. Laboratory findings were not considered until now. Earlier investigations have demonstrated the bowel's high demand for blood and oxygen and a specific high vulnerability by ischemia. Therefore anaerobic metabolism of the bowel should cause a high lactacidemia, even before necrosis.

Animals↗
PubMed1987

[The blood supply of manually sutured and stapled colonic anastomoses].

The blood supply of end-to-end staple and suture lines in the pig colon was compared. In 15 operated animals there was no anastomotic leak. Sporadic circumscribed areas of restricted circulation could be noticed in hand-sewn anastomoses. This effect was marked on the 7th and 14th postoperative day, when vascularisation of the anastomoses was increased. Such lack of vascular supply was not seen in stapled anastomoses. The intramural arteries passed through the B-shaped staples without hindrance. An unremarkable vascular pattern and a completed healing of the anastomoses were observed after 3 weeks in staple lines and after 4 weeks in suture lines.

Animals↗