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Biomedical subjects

J Self

Publications and source records attributed to J Self.

17 recordsLinked to original sources
PubMed1991

Design and evaluation of a posterior laminar clamp spinal fixation system.

A new spinal instrumentation system for posterior applications was designed with the intent of minimizing intrusion of hardware into the neural canal during and postinsertion. Basic biomechanical measurements of posterior pullout strength led to the establishment of a clamp as an effective mechanism for gaining purchase on the vertebral lamina. These experiments defined the appropriate instrumentation size, as well as establishing that there was no loss of strength with the spinous process removed and the posterior laminar cortex compromised. There was no statistically significant difference between the maximum pullout strength achievable, using a band around the lamina as a control, and that produced by the implant system, in the thoracic spine. Comparative testing of a prototype system in flexion, extension, lateral bending, and torsion showed that the system, in general, had stiffness greater than segmental wiring and less than or equal to Cotrel-Dubousset fixation.

Biomechanical Phenomena↗
PubMed1989

Using nurses for preventive activities with computer assisted follow up: a randomised controlled trial.

OBJECTIVE: To assess whether an organised programme of prevention including the use of a health promotion nurse noticeably improved recording and follow up of cardiovascular risk factors and cervical smears in a general practice that had access to computerised cell and recall. DESIGN: Randomised controlled trial. SETTING: General practice in inner London. PATIENTS: All 3206 men and women aged 30-64 registered with the practice. INTERVENTION: The intervention group had their risk factors ascertained and followed up by the health promotion nurse and the general practitioner, whereas those in the control group were managed by the general practitioner alone. END POINT: Recording and follow up of blood pressure and cervical smears after three years. Recording of smoking, family history of ischaemic heart disease, and serum cholesterol concentrations were also examined. MEASUREMENTS AND MAIN RESULTS: When the trial was stopped after two years the measurements of blood pressure in the preceding five years were 93% (1511/1620) v 73% (1160/1586) (95% confidence interval for difference 17.5 to 22.7%) for intervention and control groups respectively. For patients with hypertension the figures were 97% (104/107) v 69% (80/116) (18.2 to 38.2%). For women the proportion who had had a cervical smear in the preceding three years were 76% (606/799) v 49% (392/806) (22.5 to 31.9%). Recording of smoking, family history of ischaemic heart disease, and serum cholesterol concentrations was also higher in the intervention group compared with the control group. CONCLUSION: An organised programme, which includes a nurse with specific responsibility for adult prevention, is likely to make an important contribution to recording of risk factors and follow up of those patients with known risks.

Adult↗
PubMed1989

The effect of local controlled release of sodium fluoride on the stimulation of bone growth.

This study was performed to test the feasibility of using a biodegradable delivery system for the local controlled release of sodium fluoride as a mechanism for the stimulation of local bone growth. Sodium fluoride grains were mixed with poly-DL-lactic acid (PLA), and the mixture was then dissolved in acetone. After driving off the solvent, sheets of this material were rolled into rods 3.2 mm in diameter and 28.6 mm long. These were inserted into the intramedullary canals of the right femora of adult New Zealand White rabbits. A sham implant, made the same way but containing no fluoride, was inserted into the contralateral left leg. The effects of three different concentrations of sodium fluoride, 0.125 g NaF/g PLA, 0.250 g NaF/g PLA, and 0.500 g NaF/g PLA, were determined after a 4-week implantation period. In a second set of experiments, the concentration was fixed at 0.500 g NaF/g PLA with implantation durations of 4, 8, and 16 weeks. Expressed in terms of property ratios (experimental/control), bending strengths of the femora were significantly raised in most groups with the notable exception of Group 3 (0.500 g NaF/g PLA, 4 weeks). Cross-sectional area ratios in the distal femora were increased in all groups compared to right/left values for a normal unoperated group (p less than 0.05), with the highest ratio being 1.50 (SD = 0.44) for Group 4 (0.500 g NaF/g PLA, 8 weeks). Only Group 4 animals showed significant (p less than 0.05) increases in midshaft area ratio and none had responses proximally. Growth rates, measured by sequential fluorochrome labeling of bone followed the area ratio data and were only significant for the distal femora.

Animals↗
PubMed1988

Comparative mechanical properties of various Kirschner wire configurations in transverse and oblique phalangeal fractures.

A biomechanical study assessed the comparative mechanical properties of various wire configurations used in transverse and oblique phalangeal fractures. The configurations included crossed, oblique, and intramedullary wire techniques using 0.028-inch diameter (d) or 0.035-inch d Kirschner (K) wires. Six different configurations were tested in both the oblique fracture pattern and in the transverse fracture pattern. The mechanical properties were determined after either oblique or transverse osteotomy and fixation of the proximal phalanx. Each fixation technique was tested in apex palmar, apex dorsal, and lateral bending, as well as in torsion and distraction. The results showed that of the configurations tested, four crossed 0.028-inch d Kirschner wires obtained the highest rigidity in the transverse fracture pattern and three oblique 0.035-inch d Kirschner wires obtained the highest rigidity in the oblique fracture pattern.

Aged↗
PubMed1988

CT diagnosis of circumcaval ureter.

Variability in the normal course of the ureter makes it difficult to differentiate a normal variant from a congenital anomaly or deviation caused by a mass. CT can be useful in making this distinction. We present five cases of circumcaval ureter in which contrast-enhanced CT, by showing the ureter passing posterior and medial to the inferior vena cava (IVC), provided the definitive diagnosis. In addition, we studied the position of the inferior vena cava in the midlumbar region in 100 consecutive contrast-enhanced CT scans and compared the results with the position of the IVC in our five cases of circumcaval ureter plus one case of circumcaval ureter taken from the literature. Whereas only 6% of the normal patients had an IVC lateral to the right pedicle of the third lumbar vertebra, all of the patients with a circumcaval ureter and the one case in the literature had the IVC lateral to the pedicle. Therefore, the finding of a laterally placed IVC on CT is suggestive but not pathognomonic of circumcaval ureter. Contrast-enhanced CT can be used to prove the diagnosis of circumcaval ureter, and lateral placement of the IVC on non-contrast-enhanced CT suggests the diagnosis.

Adult↗
PubMed1987

The effect of implant axial and torsional stiffness on fracture healing.

A study was performed to compare the mechanical properties of healing transverse femoral osteotomies fixed with either (a) plates of high or low axial stiffness (compression or slotted plates) but equivalent bending and torsional stiffnesses, or (b) rods of high or low torsional stiffness (solid or slotted rods) but equivalent bending and axial stiffnesses. Compression and slotted plates were implanted contralaterally in one group of adult mongrel dogs and solid or slotted rods were implanted contralaterally in a second group as fixation for transverse osteotomies. We found that the compression-plated femora regained strength and stiffness earlier than the slotted-plated femora and healed with less callus formation. The femora fixed with rods healed with no significant differences in properties at any time interval. Also, the femora fixed with rods had mechanical properties close to those of the slotted-plated femora and lower than those of the compression-plated femora at the same time intervals. We concluded that contact compression caused the differences in the healing results and was more important than differences in torsional or axial rigidity of the implant.

Animals↗
PubMed1977

Metabolic and endocrine studies in a case of lipoatrophic diabetes.

A 20-yr-old female with congenital lipoatrophic diabetes was studied, with the following findings: (1) Serum insulin levels increased after both oral glucose and intravenous arginine administration; there was no growth hormone response to the latter. (2) The infusion of insulin (0.1 units and 0.5 units/kg) during the fed state and following at 110-hr fast produced only minimal changes of various fuels measured, with the exception of a decrease in the branched-chain amino acids. (3) There was a minimal production of ketones during the 110-hr fast. (4) Matabolic expenditure was markedly increased during the postabsorptive state (65-75 kcal/hr/sg m); it fell into the normal range during the 110-hr fast (31-35 kcal/hr/sq m). (5) Following meals, the patient experienced complaints ranging from cold and shivering to feeling hot with gross diaphoresis. These findings were associated with intermittent lability of her skin temperature, which varied 1 degree - 2 degrees F during a 3-hr period. (6) Progressive increases in doses of regular insulin before each meal resulted in up to a total of 9000 units/day being required before normal blood glucose levels were achieved. (7) A 2-wk therapeutic trial of pimozide provided no significant changes in a variety of hormones and fuels in the basal state or following insulin perturbations. (8) A variety of pituitary hormones and pituitary target organ hormones were studied in both the hypothyroid (Hashimoto's thyroiditis) and euthyroid state (following thyroid replacement). All the hormone responses were normal except that growth hormone did not rise during the slow wave sleep in either thyroid state.

Adult↗
PubMedDate not supplied

A comparison of double-plate fixation methods for complex distal humerus fractures.

A modified method of fracture fixation of complex distal humeral fractures with medial and lateral plates and bolts was biomechanically tested and compared with previously described fixation techniques. Compressive stiffness coefficients were determined for three classes of fixation before and after fatigue cycling. This procedure was followed with compressive loading to failure. The results show that in the most unstable fracture type tested this new fixation method provides increased strength and stability. Early clinical follow-up examinations of patients treated with this technique show that this method is a reasonable fixation alternative for the complex distal humerus intercondylar fracture.

Adult↗