Mechanical testing of bone ex vivo.
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Bone and Bones↗
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The relationship between social stratification and all-cause mortality among children in the United States: 1968-1992.
BACKGROUND: US childhood poverty rates have increased for most of the past 2 decades. Although overall mortality among children has apparently fallen during this interval, these aggregate mortality rates may hide a disproportionate burden imposed on the least advantaged. This study assessed the impact of social stratification on long-term US childhood mortality rates and examined the temporal relationship between mortality attributable to social stratification and childhood poverty rates. METHODS: Using US childhood mortality data obtained from the Compressed Mortality File (National Center for Health Statistics) and a county-level measure of social stratification (residential telephone availability), I evaluated the impact of social stratification on long-term trends (1968-1992) in age-adjusted mortality and compared the resulting attributable proportions to trends in childhood poverty rates. RESULTS: Between 1968 and 1987 the proportion of US childhood deaths attributable to social stratification decreased from.22 to.17. Subsequently, it increased to.24 in 1992, despite continuous declines in overall childhood mortality rates. These proportions correlated strongly with earlier childhood poverty rates, taking into account an apparent 9-year lag. Among black children comparable trends were not observed, although throughout this time period their mortality rates were far higher than among the rest of the population and declined more slowly. CONCLUSIONS: Despite declining childhood mortality rates between 1968 and 1992, children living in the least advantaged counties continued to die at higher rates than those living in the most advantaged counties. This differential worsened considerably after 1987, and by 1992 had a substantive impact on US life expectancy at birth, resulting in perhaps the most significant (in terms of years of life lost) reversal in the health of the US public in the 20th century.
Adolescent↗
Automatic analysis of gated heart studies using a Galois lattice.
Gated heart studies are currently assessed using the parametric images of first harmonic phase and amplitude in addition to the original images. More information can be obtained by multi-harmonic analysis, but the quantity of information is too great to be assessed by visual methods alone. We propose an automatic diagnosis support system which will use all the additional information, compress and analyse the data, and present the results in a single image to assist the consultant in his or her diagnosis. Multi-harmonic analysis produces many parameters to describe features of the images. A set of parameters will be selected using guidelines that link parameters and intervals of their values to clinical conditions. Images are processed using these parameters and the results stored in a binary matrix. A Galois lattice structure is then derived from the matrix where a vertex of the lattice represents a 'significant' region of the heart together with a 'logic description' of this region. Using this, areas of clinical interest can be found and displayed on a diastolic image of the heart.
Data Interpretation, Statistical↗
A bone replaceable artificial bone substitute: morphological and physiochemical characterizations.
A composite material consisting of carbonate apatite (CAp) and type I atelocollagen (AtCol) (88/12 in wt/wt%) was designed for use as an artificial bone substitute. CAp was synthesized at 58 degrees C by a solution-precipitation method and then heated at either 980 degrees C or 1,200 degrees C. In this study, type I AtCol was purified from bovine tail skins. A CAp-AtCol mixture was prepared by centirfugation and condensed into composite rods or disks. The scanning electron-microscopic (SEM) characterization indicated that the CAp synthesized at 58 degrees C displayed a crystallinity similar to that of natural bone and had a high porosity (mean pore size: about 3-10 microns in diameter). SEM also revealed that the CAp heated at 980 degrees C was more porous than that sintered at 1,200 degrees C, and the 1,200 degrees C-heated particles were more uniformly encapsulated by the AtCol fibers than the 980 degrees C-heated ones. A Fourier transformed-infrared spectroscopic analysis showed that the bands characteristic of carbonate ions were clearly observed in the 58 degrees C-synthesized CAp. To enhance the intramolecular cross-linking between the collagen molecules, CAp-AtCol composites were irradiated by ultraviolet (UV) ray (wave length 254 nm) for 4 hours or vacuum-dried at 150 degrees C for 2 hours. Compared to the non cross-linked composites, the UV-irradiated or dehydrothermally cross-linked composites showed significantly (p < 0.05) low collagen degradation and swelling ratio. Preliminary mechanical data demonstrated that the compressive strengths of the CAp-AtCol composites were higher than the values reported for bone.
Animals↗
Efficacy of a 6-month treatment with Daflon 500 mg in patients with venous leg ulcers associated with chronic venous insufficiency.
AIM: Epidemiological data show that standard compression therapy for leg ulceration in chronic venous insufficiency (CVI) often fails to effectively improve patients' condition. This study assesses the contribution of Daflon 500 mg added to conventional therapy in the healing of hypostatic ulcers of CVI patients. METHODS: Patients of about 65 years were included, with ulcers > or = 2 and > or = 10 cm diameter on 1 or 2 limbs, Doppler ankle/arm pressure index > 0.9, and no recent history of skin graft. Controls (n=68) remained on compression alone while the tested group (n=82) also received Daflon 500 mg 2 tablets/day during 6 months. Treatment could be stopped as soon as the reference ulcer appeared fully healed. Primary endpoints were the rate of healed ulcers and the time to complete healing assessed by planimetry/photography and clinical examination. Variations of the ulcer surface, appearance of the skin, and clinical symptoms of CVI were the secondary criteria. RESULTS: Only 7% of Daflon 500 mg patients necessitated the full 6 month therapy. Whatever the lesion size, from W8 significantly more healed ulcers were observed under Daflon 500 mg (p=0.004), and the ulcer surface was more reduced (p=0.012). For large ulcers, the rate of healing was approximately 2-fold higher with Daflon 500 mg, and the percentage of ulcers healed before W24 was significantly higher (p=0.008). Heavy leg sensation was significantly improved by Daflon 500 mg from W4 (p < 0.05). No treatment-related side effects were reported and the acceptability was considered excellent by 85% of Daflon 500 mg patients. CONCLUSION: Six months of Daflon 500 mg in addition to compression significantly improve some clinical symptoms and accelerate the healing process in patients with ulcerous complications of CVI, with a good acceptability.
Aged↗
Magnetic resonance imaging of acute central cord syndrome: correlation with prognosis.
OBJECTIVE: To report the magnetic resonance imaging (MR) findings of acute cervical central cord syndrome and to determine their correlation with the prognosis. METHODS: MRI findings of 35 patients with acute central cord syndrome were studied and compared with the recovery rate of ASIA score at presentation and in follow-up. RESULTS: MRI data demonstrated spinal cord compression for 32 patients, spinal cord swelling for 16 patients, and abnormal signal intensity within the spinal cord for 19 patients, including 14 with edema and 3 with hematoma. No significant difference of the recovery rate was noted between the patients treated nonoperatively and operatively (P > 0.05). There was a significant inverse correlation between the recovery rate and the degree of spinal cord compression as shown in MRI scans (P < 0.01). The presence of hematoma in MRI scans was associated with poor prognosis, as demonstrated by a significant difference of the recovery rate (P < 0.01) among the patients with normal intensity, edema and hematoma within the spinal cord. CONCLUSIONS: MRI scans provide an efficient assistance for decision-making and accurate prognostic information regarding neurological function, and therefore should routinely be performed within the early phase of acute central cord syndrome.
Adult↗
[The modern concept of the tactics of conservative and combined treatment of limb lymphedema].
The paper is concerned with the general problems of the tactics and stages of conservative and combined treatment of limb lymphedema using compression therapy techniques. The data presented herein cover both our own studies and the reported materials which are grouped so as to understand the basic principle of the concept of combined therapy for lymph edema (CTLE). The treatment presumes the use of two main variants in the form of CTLE as an independent method of conservative treatment of lymphedema and CTLE as a program coupled with surgical operations. The treatment policy for lymphedema involves two basic stages: hospital and prophylactic. The hospital program of the CTLE includes technologies acting on different pathogenetic components of lymphedema. In primary lymphedema, the hospital treatment allows to minimize lymphedema to 36% and in secondary to 4-4% of the initial parameters. During the prophylactic period, edema regression is appreciably delayed or does not take place at all. The next stage aimed at edema decrease is followed by a course of hospital CTLE which, as dependent on lymphedema severity, is carried out 1-4 times a year. The main principle of a current approach to the treatment of lymphedema is based on the concept of multimodality independent or combined treatment. The accuracy of this principle observance predetermines the efficacy of the results obtained.
Bandages↗
[Discrimination of varieties of apple using near infrared spectra based on principal component analysis and artificial neural network model].
A new method for the discrimination of varieties of apple by means of near infrared spectroscopy (NIRS) was developed. First, principal component analysis (PCA) was used to compress thousands of spectral data into several variables and describe the body of spectra, the analysis suggested that the cumulate reliabilities of PC1 and PC2 (the first two principle components) were more than 98%, and the 2-dimentional plot was drawn with the scores of PC1 and PC2. It appeared to provide the best clustering of the varieties of apple. The loading plot was drawn with PC1 and PC2 through the whole wavelength region. The fingerprint spectra, which were sensitive to the variety of apple, were obtained from the loading plot. The fingerprint spectra were applied as ANN-BP inputs. Seventy five samples from three varieties were selected randomly, then they were used to build discrimination model. This model was used to predict the varieties of 15 unknown samples; the distinguishing rate of 100% was achieved. This model is reliable and practicable. So the present paper could offer a new approach to the fast discrimination of varieties of apple.
Malus↗
Chest radiography in the intensive care unit. Indications for radiography and effects of selective archiving of films.
Consecutive chest radiographs (n = 2,303) in 601 patients in the intensive care units (ICU) were analyzed with regard to main disease and indication. Two thirds of the patients were transferred for routine post-operative treatment, 14 per cent mainly for cardiopulmonary insufficiency. The remainder were referred because of various clinical conditions. The main indications for chest radiography were routine radiographic follow-up and/or control of the position of catheters, tubes, drainages etc. (50%). Obvious clinical indications appeared in only about 1/4 of the patients. When the patients were discharged from the ICU all chest radiographs were analyzed with regard to their predicted future value. Films considered not worth storing were removed and stored in a separate archive (57%). During a 15-month follow-up period none of the removed films were requested, indicating that a substantial number of films can be sorted out continuously. The possibility to reduce and to 'clinically compress' the amount of data in a future digital picture archive is emphasized.
Humans↗
Platelet activation following application of an Esmarch bandage and tourniquet in rabbits.
The present study evaluates platelet activation following application of an Esmarch bandage and a tourniquet, procedures commonly employed to provide a bloodless operative field during limb surgery. Platelet aggregation was increased in blood samples taken from rabbits 60 min after an Esmarch bandage was applied to one thigh and immediately released. When this treatment was combined with the application of a tourniquet for 60 min, a procedure which alone did not affect platelet aggregation, results were similar to those obtained following the Esmarch bandage alone. These data suggest that tissue compression produced by application of an Esmarch bandage, but not the ischemia derived from the tourniquet, produced platelet aggregation.
Animals↗
[Human circadian rhythms and the work and rest regimen: the hypothesis of the "coiled spring"].
Studies of human free-running circadian rhythms have been reviewed. The conditions of development of free-run of the circadian rhythms were considered. On the basis of these data a hypothesis of "compressed spring" was proposed. It claims that the human circadian rhythms synchronized within the 24 h day are instable and related to physiologic tension. It follows that in conditions of relative isolation (long-term space flight, submarine navigation, polar expedition), during the transition period after a trans-meridian flight, and during adaptation to a shift (especially, night) work it is advisable to arrange a work-rest schedule on the basis of a prolonged 25 h day.
Adaptation, Physiological↗
The anatomy and clinical significance of the collateral circulation between the internal and external carotid arteries through the ophthalmic artery.
Complete occlusion of the internal carotid artery is not necessarily associated with total disruption of cerebral blood flow distal to the site of the arterial obstruction. In fact, the flow of blood may be sufficient to maintain cerebral perfusion. This is accomplished by the shunting of blood from the external to the internal carotid artery by means of collateral circuits. While several major branch arteries of the external carotid artery may be recruited in this process, the ophthalmic artery is often the final common pathway before the anastomosis with the internal carotid artery. With the aim of elucidating these collateral circles, digital subtraction angiography was used to examine 100 patients with total occlusion of the internal carotid artery. These data were compared with those obtained using Doppler ultrasound, duplex scanning, and transcranial Doppler. Forty patients were excluded because there was no demonstrable collateral circulation, because the collateral circulation used the communicating arteries, or because the ophthalmic artery arose from the middle meningeal artery. Dynamic data were obtained by compressing the branches of the two external and common carotid arteries, and the blood vessels were identified by comparison with previous anatomic studies. We have constructed a precise map of the intra- and extracranial circles that connect the internal and external carotid arteries through the pathways that include the ophthalmic artery. This map demonstrates why apparently identical vascular occlusions may have divergent symptomatologies and clinical outcomes, which may range from the complete absence of symptoms to cerebral infarction.
Aged↗
Finite element analysis of indentation tests on pyrolytic carbon.
The stresses which cause failure at contact areas between leaflets and orifices in pyrolytic carbon heart valves are evaluated. These contact stresses have previously been studied using Hertzian crack models that apply to monolithic material. Many heart valves are not monolithic pyrolytic carbon but a pyrolytic carbon deposited on graphite. Contact loads on these layered structures cause initial cracking in the pyrolytic carbon at the interface between pyrolytic carbon and graphite rather than Hertzian surface cracks. Increasing the load on layered structures will cause a secondary cracking (of Hertzian cracks) on the surface. The contact loading was simulated with a 5.1 mm diameter ball pressing against a flat sample of graphite coated with 0.26 mm of pyrolytic carbon on each surface. Finite element analysis of this model calculated the stresses associated with a range of loads causing no cracks through initial interface cracks and secondary surface cracks to complete failure. The calculated stresses are correlated with parallel laboratory experiments. A failure criterion for contact stresses is developed. The initial cracks at the graphite/pyrolytic carbon interface occur when the tensile stress in the pyrolytic carbon reaches 207 to 276 MPa and the compression stress in the graphite reaches 414 to 483 MPa. These initial cracks do not propagate immediately to the surface since they run into a high triaxial compression stress field. Circular surface cracks occur at the edge of the ball/pyrolytic carbon contact area at higher loads. These cracks require a shear stress of about 241 MPa and also require a tensile stress component. The results provide a criterion for designing contact regions in pyrolytic heart valves.
Biocompatible Materials↗
Minimizing hypoxic injury during cardiac arrest.
Efforts to minimize hypoxic injury may gain insight from considering treatments directed at different levels of biological organization, from cellular physiology to societal norms. At the cellular level, it appears that cells do not actually die during ischemia, but rather during reperfusion or resuscitation. Free radicals are implicated because antioxidants reduce cell death from ischemia/reperfusion, but typically fail to protect when only given during reperfusion. In preliminary work, two synergistic antioxidants were seen to offer significant protection even if used only during reperfusion. These findings suggest some cell death may be treatable at reperfusion and antioxidants targeted specifically at radical generation hold promise as a future therapy. On the organism level, blood flow during cardiopulmonary resuscitation (CPR) may be improved with a new manual device that combines the advantages of active-decompression CPR with interposed-abdominal-compression CPR; preliminary hemodynamic data in animals are encouraging. Possible worsening of injury in the postarrest period may occur from overuse of beta-agonists, excessive defibrillation energy, untreated hypotension, and lack of attention to intensive care principals. At the societal level, we have failed to provide simple treatments that are known to save lives, particularly basic CPR and early defibrillation. Bystander CPR suffers from poor quality of performance and from lack of initiation due to concern over disease transmission. The technology for rapid public defibrillation exists, yet is not commonly employed. Collectively, survival likelihood may be predicted with a multifactor equation which may be useful as we develop future therapies.
Animals↗
[Abdominal compression as a method of resuscitation and assisted circulation].
Experiments on animals have been carried out to investigate the hemodynamic changes during manual abdominal compression (AC) under conditions of heart fibrillation and acute heart failure. The possibility to increase the efficacy of left ventricular bypass (LVB) has been studied. Manual AC enhanced the pressure and blood flow in low-pressure compartments and increased aortic systolic and diastolic pressure. It has been also noted that LVB efficacy was increased in simultaneous assisted perfusion and abdominal compression. The first clinical data confirm the experimental findings.
Abdomen↗
Permeability of human medial collateral ligament in compression transverse to the collagen fiber direction.
This study quantified the apparent and intrinsic hydraulic permeability of human medial collateral ligament (MCL) under direct permeation transverse to the collagen fiber direction. A custom permeation device was built to apply flow across cylindrical samples of ligament while monitoring the resulting pressure gradient. MCLs from 5 unpaired human knees were used (donor age 55 +/- 16 yr, 4 males, 1 female). Permeability measurements were performed at 3 levels of compressive pre-strain (10%, 20% and 30%) and 5 pressures (0.17, 0.34, 1.03, 1.72 and 2.76 MPa). Apparent permeability was determined from Darcy's law, while intrinsic permeability was determined from the zero-pressure crossing of the pressure-permeability curves at each compressive pre-strain. Resulting data were fit to a finite deformation constitutive law [Journal of Biomechanics 23 (1990) 1145-1156]. The apparent permeability of human MCL ranged from 0.40 +/- 0.05 to 8.60 +/- 0.77 x 10(-16) m(4)/Ns depending on pre-strain and pressure gradient. There was a significant decrease in apparent permeability with increasing compressive pre-strain (p=0.024) and pressure gradient (p<0.001), and there was a significant interaction between the effects of compressive pre-strain and pressure (p<0.001). Intrinsic permeability was 14.14 +/- 0.74, 6.30 +/- 2.13 and 4.29 +/- 1.71 x 10(-16) m(4)/Ns for compressive pre-strains of 10%, 20% and 30%, respectively. The intrinsic permeability showed a faster decrease with increasing compressive pre-strain than that of bovine articular cartilage. These data provide a baseline for investigating the effects of disease and chemical modification on the permeability of ligament and the data should also be useful for modeling the poroelastic material behavior of ligaments.
Anisotropy↗
Effect of loading rate and hydration on the mechanical properties of the disc.
STUDY DESIGN: The mechanical response of bovine intervertebral discs to axial compression at different loading rates and hydration levels was quantified. OBJECTIVES: To quantify the effects of hydration and loading rate on the mechanical response of the intervertebral disc to compressive axial load. SUMMARY OF BACKGROUND DATA: The disc is known to be viscoelastic, but there are few experimental data showing the effect of loading rate and hydration on its response to compression. METHODS: Hydration level reduced by creep-loading from a fully hydrated starting point. Four groups were tested: Group A: fully hydrated (n = 5), six loading rates, from 0.3 kPa/sec to 30 MPa/sec; Group B: after 30 minutes of creep (n = 4); and Group C: after 2 hours of creep (n = 4) under a static load of 1 MPa, loading rates 3 MPa/sec, 30 kPa/sec, and 0.3 kPa/sec; Group D: at 5-minute intervals, during an 8-hour period of creep (n = 3) under a static load of 1 MPa, loading rate 3 MPa/sec. Data normalized by disc area and height: nominal stress, strain, and modulus calculated. RESULTS: Group A: Modulus increased with load and rate of loading, with significant differences among the lower three loading rates. The highest three loading rates were significantly different from the lower rates, but not from each other. Group B: At the two higher loading rates, modulus was greater than in group A. At the lowest loading rate the modulus was similar to that in Group A. Group C: At the highest loading rate, the modulus was less than that of Groups A and B. At the lower two loading rates, the modulus was similar to that in Group A. Group D: The modulus increased in the first 30 minutes and decreased in the interval from 60 to 480 minutes. CONCLUSIONS: Intervertebral disc compressive mechanical properties are significantly dependent on loading rate and hydration.
Animals↗
Review of treatment results for ulnar nerve entrapment at the elbow.
A review of 50 published reports between 1898 and 1988, comprising more than 2000 patients treated for ulnar nerve compression at the elbow, demonstrated that little more than personal bias is available for guidance in selecting treatment. To provide uniform data, the degree of nerve compression of the patients from these articles was staged using a sensory plus motor classification based on contemporary concepts of the pathophysiology of chronic nerve compression. The results of these studies are reinterpreted in light of this staging system. This analysis suggests that for a minimal degree of compression, excellent results can be achieved in 50% of the patients by nonoperative techniques and in almost 100% of patients by any of five surgical techniques. For a moderate degree of compression, the anterior submuscular technique yields the most excellent results with the fewest recurrences. For a severe degree of compression, the anterior intramuscular transposition yielded the fewest excellent and the most recurrent results. This review suggests that an internal neurolysis, combined with an anterior submuscular transposition, may be the best approach when the ulnar nerve is severely compressed.
Elbow↗