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PubMedDate not supplied

The consolidation and compressibility properties of some novel directly compressible filler-binders.

The aim of this study was to investigate the consolidation and compressibility properties and also the dilution potentials of some novel directly compressible filler-binders. For this purpose, Ludipress and Cellastose 80 (one-body compounds), Tablettose 70 and Tablettose 80 (alpha-mono agglomerated lactose) were selected. They were diluted at predetermined percentages with Spherolac 100 which is a coarse sieved hydrous crystalline lactose. The consolidation and compressibility properties of the prepared powder mixtures were determined. The experimental data were evaluated by using a computer programme (Basic 80).

Algorithms↗

PubMed1990

[Deformation phenomena occurring during compression. III. Changes of maximal compression strength in quasi-static condition].

Four materials of different properties in respect of compressibility, lactose, sodium chloride, microcrystalline cellulose (Avicel PH 101) and so-called simple granulate were investigated. In function of time and that of actual pressing force decrease of axial force on upper punch were measured in quasi-state. Evaluating relations it was established that both pressing time and pressing force had influence on deformation structural changes occurring inside compressed form. Furthermore, summing up of results showed that useful conclusions could be drawn from diagrams--which represented decrease of force--to compressibility properties of materials too.

Cellulose↗

PubMed1985

External skeletal fixation of canine tibial osteotomies. Compression compared with no compression.

In this study we compared the effects of compression on the maturity and pattern of osseous healing in canine tibial osteotomies that were fixed with an external fixation system at a single time-period, ninety days after osteotomy. The in vitro model demonstrated that compression increased rigidity of fixation. Relative to the rigidity of the intact tibia, this increase was small. Estimation of osteotomy-site bone blood flow at ninety days by 85Sr clearance and torsional testing to failure of the healed osteotomies were used to compare the maturity of bone union in each group. The pattern of healing of the osteotomy was evaluated by quantitative histological determination of new-bone formation and porosity. All of the osteotomies healed by the ninetieth day. We found no significant difference at that time in osteotomy-site bone blood flow or strength of healing of the osteotomy, although the compression-treated osteotomies healed with higher torsional stiffness. No differences were demonstrated between the two groups in the pattern of healing of the osteotomy. In both groups there was a significantly greater amount of periosteal new-bone formation in the relatively less rigidly fixed antero-posterior plane when compared with the mediolateral plane. Primary bone-healing of both the contact type and the gap type was seen in both groups. There were no significant complications and the pin-loosening rate was similar in both groups.

Animals↗

PubMed1993

Long-term time-lapse cinemicrography of human erythroblasts under compression and without compression--direct measurement of generation time of each maturation stage.

The in vitro proliferation and the successive morphological alterations of single human erythroblasts were recorded for 5 days by time-lapse, phase-contrast cinemicrography. To visualize their fine structures more clearly, we introduced a new device to compress the erythroblasts under a cover slide. Appropriate compression did not significantly affect the capacity of the erythroblasts to proliferate and differentiate, although compression produced a slight tendency towards shorter generation time. The directly measured generation time was 24.5 +/- 4.5 h (mean +/- S.D.) for generation -1 (one generation prior to the orthochromatic erythroblast stage); 18.4 +/- 3.0 h for generation -2; and 18.3 +/- 4.1 h for generation -3 [corrected], these being arranged in inverse order of cell lineage. The cell size became progressively smaller and the nucleus-to-cytoplasm ratio decreased along with the maturation of the erythroblasts, showing a distinctive distribution range for each generation. Progression of hemoglobinization was simultaneously recorded qualitatively by Soret band absorption micrography. Cell movements characteristic for each maturation stage, e.g. perimitotic bleb-throwing of immature erythroblasts and vigorous movements of orthochromatic erythroblasts, heralding enucleation, were also clearly recorded. The method described here will be useful for the direct study of the dynamic morphology of the erythron in normal and abnormal states.

Cell Differentiation↗

PubMedDate not supplied

Sensitivity and specificity of MRI in detecting malignant spinal cord compression and in distinguishing malignant from benign compression fractures of vertebrae.

The accuracy of magnetic resonance (MR) imaging in the detection of metastatic compression of the spinal cord and the cauda equina (MCCE) in 75 patients with known primary malignancy outside the central nervous system is determined retrospectively by comparing the MR results with findings of myelography, surgery, clinical follow-up and autopsy. The sensitivity is 93%, the specificity 97% and the overall accuracy 95%. The signal intensity measured in the sagittal MR images of a collapsed vertebral body is divided by that of an average of three adjacent normal vertebrae to form a signal intensity ratio (SIR). The SIRs of 41 metastatic and 15 post-traumatic collapsed vertebrae are calculated. A ratio of 0.8 has the most differentiating power. All benign and one malignant compressed vertebrae have SIRs greater than 0.8.

Cauda Equina↗

PubMedDate not supplied

An in vitro biomechanical comparison of a limited-contact dynamic compression plate fixation with a dynamic compression plate fixation of osteotomized equine third metacarpal bones.

OBJECTIVES: To compare the monotonic biomechanical properties and fatigue life of a broad, limited contact, dynamic compression plate (LC-DCP) fixation with a broad, dynamic compression plate (DCP) fixation to repair osteotomized equine 3rd metacarpal (MC3) bones. STUDY DESIGN: In vitro biomechanical testing of paired cadaveric equine MC3 with a mid-diaphyseal osteotomy, stabilized by 1 of 2 methods for fracture fixation. ANIMAL POPULATION: Twelve pairs of adult equine cadaveric MC3 bones. METHODS: Twelve pairs of equine MC3 were divided into 3 test groups (4 pairs each) for (1) 4-point bending single cycle to failure testing, (2) 4-point bending cyclic fatigue testing, and (3) torsional single cycle to failure testing. An LC-DCP (8-hole, 4.5 mm) was applied to the dorsal surface of 1 randomly selected bone from each pair. One DCP (8-hole, 4.5 mm broad) was applied dorsally to the contralateral bone from each pair. All plates and screws were applied using standard AO/ASIF techniques to MC3 bones that had mid-diaphyseal osteotomies. Mean test variable values for each method were compared using a paired t-test within each group. Significance was set at P<.05. RESULTS: The mean 4-point bending yield load, yield bending moment, composite rigidity, failure load, and failure bending moment of LC-DCP fixation were significantly greater (P<.01) than those of broad DCP fixation. Mean cycles to failure for 4-point bending was significantly (P<.001) greater for broad DCP fixation compared with broad LC-DCP fixation. Mean yield load, mean composite rigidity, and mean failure load in torsion was significantly (P<.02) greater for broad LC-DCP fixation compared with broad DCP fixation. CONCLUSION: Broad LC-DCP offers increased stability in static overload testing, however, it offers significantly less stability in cyclic fatigue testing. CLINICAL RELEVANCE: The clinical relevance of the cyclic fatigue data supports the conclusion that the broad DCP fixation is biomechanically superior to the broad LC-DCP fixation in osteotomized equine MC3 bones despite the results of the static overload testing.

Animals↗

PubMedDate not supplied

An in vitro biomechanical comparison of a prototype equine metacarpal dynamic compression plate fixation with double dynamic compression plate fixation of osteotomized equine third metacarpal bones.

OBJECTIVES: To compare the monotonic biomechanical properties of a prototype equine third metacarpal dynamic compression plate (EM-DCP) fixation with a double broad dynamic compression plate (DCP) fixation to repair osteotomized equine third metacarpal (MC3) bones. STUDY DESIGN: In vitro biomechanical testing of paired cadaveric equine MC3 with a mid-diaphyseal osteotomy, stabilized by 1 of 2 methods for fracture fixation. POPULATION: Twelve pairs of adult equine cadaveric MC3 bones. METHODS: Twelve pairs of equine MC3 were divided into 3 test groups (4 pairs each) for (1) 4-point bending single cycle to failure testing, (2) 4-point bending cyclic fatigue testing, and (3) torsional testing. The EM-DCP (10-hole, 4.5 mm) was applied to the dorsal surface of one randomly selected bone from each pair. Two DCPs, 1 dorsally (10-hole, 4.5 mm broad) and 1 laterally (9-hole, 4.5 mm broad) were applied to the contralateral bone from each pair. All plates and screws were applied using standard AO/ASIF techniques to MC3 bones that had mid-diaphyseal osteotomies. Mean test variable values for each method were compared using a paired t-test within each group. Significance was set at P<.05. RESULTS: Mean 4-point bending yield load, yield bending moment, bending composite rigidity, failure load and failure bending moment of the EM-DCP fixation were significantly greater (P<.0001) than those of the double broad DCP fixation. Mean cycles to failure in 4-point bending of the EM-DCP fixation was significantly greater (P<.0008) than that of the double broad DCP fixation. Mean yield load, composite rigidity, and failure load in torsion of the EM-DCP fixation were significantly greater (P<.0035) than that of the double broad DCP fixation. CONCLUSION: The EM-DCP provides increased stability in both static overload testing and cyclic fatigue testing. CLINICAL RELEVANCE: Results of this in vitro study support the conclusion that the prototype EM-DCP fixation is biomechanically superior to the double broad DCP fixation for the stabilization of osteotomized equine MC3.

Animals↗

PubMed2006

Manual chest compression vs use of an automated chest compression device during resuscitation following out-of-hospital cardiac arrest: a randomized trial.

CONTEXT: High-quality cardiopulmonary resuscitation (CPR) may improve both cardiac and brain resuscitation following cardiac arrest. Compared with manual chest compression, an automated load-distributing band (LDB) chest compression device produces greater blood flow to vital organs and may improve resuscitation outcomes. OBJECTIVE: To compare resuscitation outcomes following out-of-hospital cardiac arrest when an automated LDB-CPR device was added to standard emergency medical services (EMS) care with manual CPR. DESIGN, SETTING, AND PATIENTS: Multicenter, randomized trial of patients experiencing out-of-hospital cardiac arrest in the United States and Canada. The a priori primary population was patients with cardiac arrest that was presumed to be of cardiac origin and that had occurred prior to the arrival of EMS personnel. Initial study enrollment varied by site, ranging from late July to mid November 2004; all sites halted study enrollment on March 31, 2005. INTERVENTION: Standard EMS care for cardiac arrest with an LDB-CPR device (n = 554) or manual CPR (n = 517). MAIN OUTCOME MEASURES: The primary end point was survival to 4 hours after the 911 call. Secondary end points were survival to hospital discharge and neurological status among survivors. RESULTS: Following the first planned interim monitoring conducted by an independent data and safety monitoring board, study enrollment was terminated. No difference existed in the primary end point of survival to 4 hours between the manual CPR group and the LDB-CPR group overall (N = 1071; 29.5% vs 28.5%; P = .74) or among the primary study population (n = 767; 24.7% vs 26.4%, respectively; P = .62). However, among the primary population, survival to hospital discharge was 9.9% in the manual CPR group and 5.8% in the LDB-CPR group (P = .06, adjusted for covariates and clustering). A cerebral performance category of 1 or 2 at hospital discharge was recorded in 7.5% of patients in the manual CPR group and in 3.1% of the LDB-CPR group (P = .006). CONCLUSIONS: Use of an automated LDB-CPR device as implemented in this study was associated with worse neurological outcomes and a trend toward worse survival than manual CPR. Device design or implementation strategies require further evaluation. TRIAL REGISTRATION: clinicaltrials.gov Identifier: NCT00120965.

Aged↗

PubMed2005

Percutaneous compression plating versus compression hip screw fixation for the treatment of intertrochanteric hip fractures.

Percutaneous compression plate (PCCP) devices are used for the fixation of intertrochanteric hip fractures by a minimally invasive technique. One hundred and eight patients who underwent this procedure were retrospectively compared with 155 patients who underwent compression hip screw (CHS) fixation. The general characteristics of the two groups, including age, sex, side of injury and co-morbidities assessed by the ASA score were similar. The operative time was significantly shorter in the PCCP group (67 versus 87 min, p=0.00). Postoperative blood transfusions were not required in 40% of the patients in the PCCP group compared to 24% of the patients in the CHS group (p<0.01). The rate of systemic postoperative complications was lower in the PCCP group (p=0.02) both in univariate and multivariate analyses. A considerable reduction was observed in cardiovascular complications (OR=3.1, p<0.05). Length of hospitalisation, implant failure and mortality rates were not significantly different between the two study groups. We conclude that the PCCP device offers several advantages over CHS device and may improve the current treatment of intertrochanteric hip fractures while maintaining a similar success rate in fracture fixation.

Aged↗

PubMed2002

Visualization of bed compression in an axial compression liquid chromatography column.

The consolidation of a packed bed undergoing axial compression was studied in glass columns using an on-column visualization process. In this visualization process the refractive indices of the mobile phase (carbon tetrachloride) and the stationary phase (YMC C18 silica) matched perfectly, hence the otherwise opaque stationary phase became transparent to the eye. Alumina layers, which have a different refractive index, were placed at regular intervals along the column bed. These layers were therefore visible and their movement could be tracked during the axial compression of the bed. Consequently, the Young's modulus could be measured at three radial locations and at four bed depths below the head fitting. Theresults showed that the bed was heterogeneous in packing density, both radially (with the bed density increasing from the column center toward the wall) and axially (with the density increasing from the column top toward its center). Furhermore, the bed was shown to be non-symmetrical about the column axis. This was thought to be due to the column inlet head fitting making contact with the packing material on one side of the column first, rather than making contact with the entire cross section of the packing simultaneously.

Carbon Tetrachloride↗

PubMed1997

Effects of simulated mouth-to-mouth ventilation during external cardiac compression or active compression-decompression in a swine model of witnessed cardiac arrest.

STUDY OBJECTIVE: To assess the effects of simulated mouth-to-mouth (MTM) ventilation on blood gases, gas exchange, and minute ventilation during external cardiac compression (ECC) or active compression-decompression (ACD) in a swine model of witnessed cardiac arrest and bystander CPR. METHODS: Twenty swine were anesthetized, intubated, ventilated with room air, and monitored for aortic and right atrial pressure and blood gas sampling. After 1 minute of ventricular fibrillation cardiac arrest, ECC or ACD was manually performed at a rate of 100 per minute for 12 minutes. Animals in the room air group had their endotracheal tubes open to air, whereas those in the MTM group were mechanically ventilated with a gas mixture of 16% oxygen and 4% carbon dioxide. Arterial and venous PO2, PCO2, and pH values; oxygen consumption (VO2); carbon dioxide production (VCO2); and minute ventilation (VE) were measured at baseline and 1, 5, 9, and 13 minutes after induction of cardiac arrest. RESULTS: MTM ventilation did not alter arterial or venous PO2 values in comparison with room air but did result in higher arterial PCO2 values at 5 and 9 minutes (although the mean PCO2 was 40 mm Hg or less [5.3 kPa] in all groups) and significant central venous hypercarbic acidosis at 9 and 13 minutes. Arterial PO2 values were greater in the ACD than the ECC groups at 5, 9, and 13 minutes, although all groups maintained acceptable PO2 (mean values > or = 60 mm Hg [8.0 kPa]) through 9 minutes of CPR and through 13 minutes in all but the ECC-room air group. PCO2 values were lower in the ACD groups beyond 1 minute, with the ACD-room air group showing extreme hyperventilation (mean PCO2 < or = 20 mm Hg [2.7 kPa]). MTM ventilation resulted in negative VO2 and VCO2 for the first few minutes, reflecting changes in pulmonary gas stores. As equilibrium was approached, VO2 and VCO2 approached zero in all groups, reflecting low cardiac output. MTM ventilation did not improve VE over room air at any time during ACD. It did improve VE during ECC, but only at the 12th interval. CONCLUSION: In this swine model of witnessed CPR, simulated MTM ventilation was not beneficial for blood gases, gas exchange, or ventilation during ECC or ACD CPR.

Animals↗

PubMed1995

Effectiveness of pneumatic leg compression devices for the prevention of thromboembolic disease in orthopaedic trauma patients: a prospective, randomized study of compression alone versus no prophylaxis.

A prospective, randomized clinical trial in 304 orthopaedic trauma patients with hip and pelvic fractures was conducted to investigated the effectiveness of pneumatic sequential leg compression devices (PSLCDs) for the prevention of thromboembolic disease. The control group received no specific form of prophylaxis. Patients were followed by venous Doppler, duplex can, and ventilation perfusion lung scans. The study end-point was documented pulmonary embolism and/or deep vein thrombosis. The incidence of a venous thromboembolic event in the control group was 11% and in the experimental group 4%. This difference was statistically significant (p = 0.02). These patients were also stratified into hip and pelvic fracture groups. In the hip fracture patients, the control group had a thromboembolic event incidence of 12% and the experimental group 4%. This difference was also statistically significant (p = 0.03). In the pelvic fracture group there was a thromboembolic incidence of 11% in the controls, demonstrating this patient population to be at significant risk. In this group, the PSLCDs were not statistically shown to be effective. Pneumatic leg compression devices are effective in reducing the incidence of thromboembolic events in patients with hip fractures.

Adult↗

PubMed1995

A mechanical comparison of the dynamic compression plate, limited contact-dynamic compression plate, and point contact fixator.

Cortical bone porosis associated with the dynamic compression plate (DCP) prompted the development of the limited-contact dynamic compression plate (LC-DCP) and the point-contact fixator (PC-Fix) to increase bone vascularity. However, the comparative fixation characteristics of the three designs are unknown. Transverse fractures were physiologically created in paired cadaveric sheep tibiae, which were plated before torsion testing and four-point bending to failure. The tibiae were grouped randomly and compared as follows: DCP versus LC-DCP, DCP versus PC-Fix, and LC-DCP versus PC-Fix. Mean torque to failure demonstrated no significant difference between the three plates (p < 0.33). Mean bending stiffness, gap opening, and moment to failure also demonstrated no significant difference between the three designs with p < 0.29, < 0.13, and < 0.16, respectively. The LC-DCP and PC-Fix have torsion and bending properties comparable with the DCP in the fixation of simple transverse diaphyseal fractures.

Animals↗

PubMed1975

Intertrochanteric osteotomy for osteoarthritis of the hip. A radiological assessment of non-compressive and compressive methods.

A radiological review of two groups of intertrochanteric osteotomies of the femur for primary osteoarthritis of the hip has been made. Each group oroginally consisted of forty-one hips. In one group a Wainwright straight V-spline without compression had been used for fixation, and in the other group an AO angled plate with compression. The time for bony union was equal in the two groups but the incidence of non-union was lower in the AO group. Regression of cysts and of bone sclerosis was more frequent in the Wainwright group, possible as a consequence of the greater medial displacement and varus angulation.

Adult↗

PubMed1987

Two-state compression of spectral tilt: individual differences and psychoacoustical limitations to the benefit from compression.

A psychoacoustic rationale was developed for a hearing aid design in which compression of spectral tilt was incorporated without any instantaneous nonlinear distortion. This involved switching between a 'flat' and a 'rising' frequency response; the switching was done slowly to avoid audible transients and was controlled by feedback derived from comparison of output levels in low- and high-frequency channels, approximating voiced/unvoiced detection. The effect of this switching process was to narrow the distribution of spectral tilt values compared with the input. Asynchrony between the switching and the triggering speech structures was avoided by also delaying the signal path. Unfortunately, hearing-impaired listeners performed more poorly on the switching system than on either of the control 'flat' or 'rising' frequency-responses. An explanation is offered (on the basis of growing evidence from perceptual experiments) of the perceptual importance of temporal envelope contours within individual frequency bands. It was possible, in part, to predict individuals' results in the switching condition from age and audiometric or psychoacoustic characteristics. The results suggest a modification to the switching design, and they point to an intrinsic limit to the ability of all hearing aids of the compression type to enhance intelligibility.

Adult↗

PubMedDate not supplied

[Perforation of the large intestine caused by compressed air. Experimental studies reconstructing compressed air insufflation].

A foreign worker died after a compressed air injury. The insufflation of high pressure air into the anus caused multiple ruptures in the part anterior of the dilated sigmoid and colon descending. For the reconstruction of the case it was necessary to know the minimum distance between the nozzle and the gluteal region. Experimental work has shown that clothing does offer protection against the high pressure air and colon perforations can only be expected if there is a small distance between the jet of the compressed air and the anal region.

Air Pressure↗

PubMed1983

Early progressive kyphosis following compression fractures. Two case reports from a series of "stable" thoracolumbar compression fractures.

In an 18-year-old man and an 18-year-old woman, significant kyphotic deformity progressively developed in the course of the healing of apparently stable thoracic compression fractures. The common features were: (1) multiple adjacent fractures; (2) location in the thoracic spine; (3) associated thoracic injury; and (4) youth. The possibility of early progressive kyphotic deformity should be carefully monitored so that appropriate treatment can be instituted before the deformity becomes significant. Although both isolated fractures and multiple-level fractures of the thoracolumbar spine occur predominantly between T12 and L2, there is a secondary area that is predisposed to compression fractures in sequence from T5 to T7.

Accidents↗

PubMed1990

Metastatic spinal cord compression. Occurrence, symptoms, clinical presentations and prognosis in 398 patients with spinal cord compression.

We reviewed all medical records concerning patients suffering from spinal cord or cauda equina compression (SCC) secondary to cancer, in the eastern part of Denmark, from 1979 through 1985. During the period the incidence of SCC in cancer patients went up from 4.4% to 6%. However, this increase was not significant. The series comprised 398 cases, with carcinoma of the prostate (19%), lung (18%), breast (14%) and kidney (10%) accounting for 61%. The symptoms were evaluated in accordance with the patients rating of pain, motor deficits, sphincter control and paraesthesia, whereas the clinical manifestations were classified on the basis of motor deficit and bladder dysfunction. During the period preceding the diagnosis of SCC, 83% of the patients suffered from back pain, 67% from deteriorating gait and 48% had retention of the urine. In 35% of the patients there was no sphincter disturbance and 10% had normal sensory function. The outcome of treatment was estimated by changes in motor deficits and sphincter function, and depended primarily on the patients condition at the time of the diagnosis. Of the patients who were able to walk before treatment, 79% remained ambulatory, whereas only 18% of the non-ambulatory patients regained walking ability. Patients treated by decompressive laminectomy followed by radiotherapy apparently had a better response than patients treated with surgery or irradiation alone, but when the patients pre-treatment motor function was taken into account, no significant difference was observed. The study may call for a properly randomized trial with careful stratification of tumour biology, performance status and neurological deficits.

Adolescent↗