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Biomedical subjects

A Simkin

Publications and source records attributed to A Simkin.

At least 37 records · Page 2Linked to original sources
PubMed1985

A prospective study of the effect of a shock-absorbing orthotic device on the incidence of stress fractures in military recruits.

In a prospective study of stress fractures the hypothesis that a shock-absorbing orthotic device worn within military boots could lessen the incidence of stress fractures was tested. The incidence of metatarsal, tibial, and femoral stress fractures was lower in the orthotic group, but only the latter difference was statistically significant. The time of onset and the location of stress fractures between orthotic and nonorthotic users did not differ. These findings suggest that the incidence of femoral stress fractures, which are the most dangerous type of stress fracture because of their high risk of developing into displaced fractures, can be reduced by an orthotic device.

Fractures, Bone↗
PubMed1985

The normal range of subtalar inversion and eversion in young males as measured by three different techniques.

In a prospective study, 272 males aged 18 to 20 had goniometric measurement of their subtalar inversion and eversion by three different methods. Placing the ankle in dorsiflexion while performing the measurements decreased the mean inversion from 32 to 22 degrees but had little effect on eversion. The neutral position of the subtalar joint was found to have a mean value of 3 degrees of varus from the midpoint of the tibia. The technique for measuring subtalar motion as described by the Committee for the Study of Joint Motion of the American Academy of Orthopaedic Surgeons has less subjective variables than the other two methods used in this study. Its use is therefore recommended if comparisons are to be made between series.

Adolescent↗
PubMed1982

Effect of cholecalciferol derivatives on the mechanical properties of chick bones.

Chicks were depleted of vitamin D, divided into groups, and treated daily with (a) cholecalciferol, (b) 1 alpha-hydroxycholecalciferol [1 alpha (OH)-D3], (c) 24R, 25-dihydroxycholecalciferol [24R,25-(OH)2D3], or (d) 1 alpha (OH)D3 and 24R,25(OH)2D3. Two additional groups of chicks were studied, one that was continuously depleted of vitamin D, and another that was continuously supplemented with the vitamin, since day 1. After killing, the tibiae were removed and tested for their mechanical properties. Bending load was applied to the midshaft, and the intrinsic properties of this site, its quantity and geometry were analyzed. From a mechanical point of view, the weakest bones found were of birds depleted of vitamin D, whereas the strongest were of those treated with 1 alpha (OH)D3. Only the bones of the 24R,25(OH)2D3-treated or the 1 alpha (OH)D3 and 24R,25(OH)2D3-treated groups of birds showed mechanical properties comparable to those obtained with vitamin D-replete chicks.

24,25-Dihydroxyvitamin D 3↗
PubMed1981

The foot-ground pressure distribution following triple arthrodesis.

The present is a long-term follow-up study of patients who underwent triple arthrodesis for a variety of pathologic alterations. Utilizing a new method for both the qualitative and quantitative measurement of foot-ground pressure patterns, these patterns were recorded in forty control feet and twenty-six operated feet. In the patient group, less equal distribution of body weight between both feet was observed in comparison to the control group. In the latter, the main load underneath the foot was distributed underneath the forefoot and heel, while in the patient group, this load distribution had persistently shifted to the midfoot and heel, thus producing a completely different foot-ground pressure pattern. Furthermore, under the forefoot, the main load was located under the medial two rays in the control group, shifting towards the lateral rays in the patient group. The talo-navicular joint had the highest rate of non-union, but no positive correlation between that finding and persistent pain was found. Feet affected by neurological disorders often became pain-free following surgery, but none of the patients showed such post-traumatic relief.

Adolescent↗
PubMed1981

The dynamic vertical force distribution during level walking under normal and rheumatic feet.

Normal subjects and patients with rheumatoid arthritis and varying degrees of foot involvement have been studied using an apparatus which measures the dynamic force distribution under the foot during walking. There was a significant change in the walking pattern of the patients, expressed in slowing the speed of walking, lowering the heel-strike and push-off impacts, increasing the double-support period and reducing the amount of impulse taken by the forefoot. As a result, the localized peak loads and impulses were not higher than those of the control group, but moved from the medial side of the foot towards the centre, and the ratio of peak to average load (force concentration factor) at this region increased.

Adult↗
PubMed1977

Effect of local application of fluoride on healing of experimental bone fractures in rabbits.

The effect of local application of low fluoride concentrations on the healing of experimental bone-radii fractures in 20 rabbits was examined. No external fixation was required after the osteotomy and gelfoam being used as a medium for fluoride application. Histologic mineral and mechanical strength measurements were carried out on the healing callus. There were no significant changes in the ashpercentage and the fluoride concentration of the ash between the experimental and control callus. A significantly higher percentage of ossified tissue was found in the fluoride treated callus. The breaking strength was found to be significantly higher in the bone fractures treated with fluoride, whereas there was no notable difference between the surface areas. It is postulated that the greater amount of ossified tissues, the differences in organization of the bone trabecules, and/or an improved mineral crystallinity may be responsible for this result.

Animals↗
PubMed1976

The effect of fluoride on bone of rats fed diets deficient in calcium or phosphorus.

Four groups of weanling rats were fed for 2 weeks on a diet sufficient or insufficient in calcium and/or phosphorus. Each group was divided into four subgroups which were offered distilled water supplemented with 0, 50, 75, or 150 ppm fluoride. High levels of fluoride in drinking water inhibited weight gain. This inhibition was less in rats deficient in phosphorus than when normal-phosphorus diets were offered. At a low level, fluoride was without any effect on bone ash, thickness of femoral cortical bone, and mechanical strength, as measured by maximal load, ultimate stress to breaking, and limit of elasticity. Modulus of elasticity was decreased. At higher levels fluoride tended to decrease most of these parameters, except in rats deprived of both calcium and phosphorus. The effect of fluoride was modified by lack of dietary calcium and/or phosphorus and appeared to be weaker in rats deficient in these nutrients. Lack of dietary calcium and/or phosphorus decreased bone strength more than did fluoride content of water and of bone mineral. Concentration of bone ash and thickness of femoral cortical bone were closely correlated with parameters of mechanical strength.

Animals↗
PubMed1976

Achondrogenesis type I in three sibling fetuses. Scanning and transmission electron microscopic studies.

Three spontaneously aborted fetuses with Type I achondrogenesis in a family with a first cousin marriage are described. Studies by light microscopy revealed abnormal cartilage, enchondral, and periosteal bone, and normal tooth development with abnormal alveolar bone. Electron microscopic studies of cultured skin fibroblasts manifested structurally normal cells. Scanning electron microscopy studies had shown deficient intercartilaginous septa in the metaphysis, with abnormally large calcifying globules. In the diaphysis, the orientation of bone trabeculae and collagen fibers within the trabeculae was disturbed. The numerous osteocytic lucunae were wide and irregular in arrangement and shape. Type 2 achondrogenesis, as studied in these fetuses, is probably a widespread mesenchymal defect, manifested by abnormal calcification and ossification of enchondral and periosteal bone.

Achondroplasia↗
PubMed1975

The effect of fluoride alone or fluoride followed by calcium and vitamin D on disuse osteoporosis of the rat tail vertebrae.

The therapeutic effect of fluoride alone or fluoride followed by calcium and vitamin D administration on the osteoporosis induced by immobilization of the rat tail vertebrae was investigated. Tail immobilization was carried out by musclectomy and tendectomy. After 60 days of immobilization, the vertebrae were examined for bone mass, breaking strength, ash percentage and Ca, P and F content. NaF or Ca and vitamin D as separate treatments improved the osteoporosis induced by immobilization. The effects of NaF treatment were more pronounced than those of Ca and vitamin D. NaF and NaF followed by Ca and vitamin D produced a similar degree of improvement in breaking strength. The fact that fluoride and calcium and vitamin D were administered separately and sequentially may explain the absence of a synergistic effect.

Animals↗
PubMed1975

Effect of repletion with dietary calcium on composition and mechanical properties of bone of calcium-deprived rats.

Four groups of rats were fed a low-calcium diet (0.02%) and two groups a normal calcium diet (0.50%). After 2 weeks one group from each dietary calcium level was sacrificed and the femurs examined. The remaining three groups which had been kept on the low-calcium diet were then given diets richer in calcium: 0.25, 0.35 and 0.5%. The remaining group on the normal calcium diet continued receiving it. After two more weeks all animals were sacrificed and their femurs examined. Rats fed the low-calcium diet lagged behind in weight gain; ash content, breaking strength, and modulus of elasticity of their femurs were much lower than those of animals on the normal calcium diet. Feeding diets with increasing calcium content increased bone ash and improved mechanical properties. However, improvement of breaking strength and elasticity did not parallel strictly increases in mineralization. Repletion with a normal calcium diet (0.50%) failed to increase bone ash to normal levels but mechanical properties were improved by repletion with substantially lower dietary calcium levels. Maximal breaking strength was obtained by repletion feeding with a dietary calcium level which failed to increase bone ash. It seems that factors other than mineralization determine breaking strength and elasticity of bone recovering from calcium deprivation.

Animals↗