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PubMedDate not supplied

Nitinol compression staples for bone fixation in foot surgery.

We reviewed the use of compression staples made of the memory metal alloy nitinol for fixation in foot surgery. A retrospective study was performed of 31 feet in 27 patients who underwent arthrodesis or an osteotomy fixated using compression staples. OSStaples (BME, San Antonio, Texas) were used in 18 feet, and Memodyn staples (Telos Medical, Fallston, Maryland) were used in 13 feet. A total of 48 compression staples were implanted. The following procedures were performed and fixated using compression staples: 15 Akin osteotomies, 2 first metatarsal base epiphysiodeses, 3 first metatarsal-cuneiform fusions, 2 naviculocuneiform fusions, 3 calcaneocuboid fusions, 4 talonavicular fusions, 3 subtalar joint fusions, and 2 Evans osteotomies. In our clinical experience, compression staples provide an adequate source of internal fixation in foot surgery. Good bone apposition and stabilization and compression of the bone surfaces before staple fixation are important when using staple fixation to promote an optimal environment for bone healing.

Alloys↗

PubMed1998

ECG compression: evaluation of FFT, DCT, and WT performance.

This work investigates a set of ECG data compression schemes to compare their performances in compressing and preparing ECG signals for automatic cardiac arrhythmia classification. These schemes are based on transform methods such as fast Fourier transform (FFT), discrete cosine transform (DCT), wavelet transform (WT), and their combinations. Each specific transform is applied to a pre-selected data segment from the MIT-BIH database and then compression is performed in the new domain. These transformation methods are known as an important class of ECG compression techniques. The WT has been shown as the most efficient method for further improvement. A compression ratio of 7.98 to 1 has been achieved with a percent of root mean square difference (PRD) of 0.25%, indicating that the wavelet compression technique offers the best performance over the other evaluated methods.

Algorithms↗

PubMed1999

Changes in breast compressibility with age: implications for stereotactic biopsy.

OBJECTIVE: Stereotactic percutaneous core breast biopsy is a less invasive procedure than open biopsy. However, insufficient breast compression thickness can cause problems with this method, and has been noted particularly in elderly women. This study was conducted to determine the relation between breast compressibility and age. METHODS AND PATIENTS: A total of 312 women, aged 28 to 90 years, referred for screening or diagnostic mammography were prospectively evaluated. Routine craniocaudal and mediolateral oblique mammographic views were obtained and resulting compression thicknesses recorded. RESULTS: The greatest mean breast thickness was found in women 50 to 59 years of age, with younger and older women having less breast compression thickness. The decrease in thickness was statistically significant in women 70 years of age and older. In women older than 80 years, the percentage of breasts that compressed to less than 20 mm (the minimum thickness for safe passage of a core biopsy needle) was 53.8% in the craniocaudal view and 34.6% in the mediolateral view. CONCLUSION: Because of insufficient breast compression thickness, many elderly patients are not suitable candidates for stereotactic core breast biopsy.

Adult↗

PubMed1976

[Functionally stable osteosynthesis of the mandible by means of an excentric-dynamic compression plate. Results of a follow-up of 25 cases].

The stability of internal fixation is enhanced by axial compression on the fracture ends. If internal fixation of the mandible is achieved by a compression plate at the lower border of the mandible (compression side), distraction of the fracture ends on the occlusal side occurs which has to be counteracted without damaging the roots of the teeth on the occlusal side (traction side) or without damaging the inferior alveolar nerve. From experiments on models it was seen that an acceptable solution to this problem is given by the use of the combined compression plate and tension band plate or the "Excentric Dynamic Compression Plate" (EDCP). In this paper 25 clinical cases of internal fixation of the mandible by means of the EDCP are examined and discussed. The following relevant facts were reviewed on all patients: -- kind of trauma -- age -- dentition -- localization of the fracture -- local and general additional injuries -- time of operation -- material used for internal fixation -- type of occlusal immobilisation during operation -- use of antibiotics -- skin closure -- mobilisation -- hospital stay -- duration of work disability -- complications -- scarring -- neurological disablement -- malocclusion In this paper emphasis is layed upon internal fixation by means of the EDCP. The clinical evaluation of the 25 cases clearly demonstrates that the main indication for internal fixation with the EDCP is given in fractures of the horizontal ramus of the mandible, because in this localisation the plate has to be applied beneath the inferior alveolar nerve. A further indication for internal fixation with the EDCP are fractures of the angle of the mandible. In these cases the tension band principle by means of a tension banc archbar or a tension band plate cannot be applied, because of missing teeth on the proximal fragment, or a non erupted wisdom tooth. These indications can be summarized as follows: -- In fractures of the angle of the mandible--when ever possible compression plate and tension band plate, otherwise EDCP -- In fractures of the horizontal ramus--EDCP -- In fractures of the mandibular front--DCP.

Bone Plates↗

PubMed2001

Graduated compression stockings: knee length or thigh length.

The mechanisms by which graduated compression stockings prevent deep venous thrombosis are not completely understood. In the current study the physiologic effect of low-pressure graduated compression stockings on the venous blood flow in the lower limb and the practical aspects of their use were assessed. Patients having elective orthopaedic surgery at a university orthopaedic department were randomized into five groups to wear two different types of graduated compression stockings in thigh and knee lengths. Patients in the fifth control group did not wear graduated compression stockings. Venous occlusion strain gauge plethysmography was used to measure venous flow. After 20-minutes bed rest there was a highly significant increase in venous capacitance and venous outflow in patients in all of the four groups wearing stockings. There was no difference in the mean of the percentage change of venous capacitance in patients in the four groups wearing stockings. The knee length Brevet stockings were less efficient in increasing the venous outflow. There was no significant change in the venous capacitance and venous outflow in patients in the control group. Visual assessment of the fit and use of stockings was done, and patients' subjective opinion of comfort was sought. The knee length graduated compression stockings wrinkled significantly less, and significantly fewer patients reported discomfort with them. All stockings were reported to be difficult to use. Thigh and knee length stockings have a significant effect on decreasing venous stasis of the lower limb. Knee length graduated compression stockings are similarly efficient in decreasing venous stasis, but they are more comfortable to wear, and they wrinkle less.

Bandages↗

PubMedDate not supplied

Biomechanical analysis of compression screw fixation versus standard in situ pinning in slipped capital femoral epiphysis.

A slipped capital femoral epiphysis was created in 12 matched pairs of immature bovine femora using an anterior-to-posterior-directed shear force. All soft tissues, with the exception of the perichondrial ring, were removed before testing. One specimen from each pair was fixed with a single cannulated screw in standard fashion, whereas the contralateral specimen was fixed with a single screw that compressed the physis. The amount of compression achieved was quantified using Fuji film. Standard fixation yielded 1.4 MPa of pressure across the physis; compression fixation yielded 3.2 MPa, a 2.3-fold difference (p = 0.0001). The compression fixation was 47% more stiff than standard technique (p = 0.030), yet the differences in ultimate strength (p = 0.180) and energy absorbed at failure (p = 0.910) were not statistically significant. The stiffness of the compressed specimens remained less than that of the intact femora. Single-screw compression fixation of in vitro bovine femora was significantly more stiff than the current, widely used noncompression fixation technique, yet does not compromise the ultimate strength, energy absorbed, or the technical ease of single-implant fixation.

Animals↗

PubMedDate not supplied

[Chronic venous insufficiency and compression therapy].

INTRODUCTION: Disorders of venous circulation are among most frequent diseases in the human population. During recent years there has been increased interest in physiopathology of chronic venous insufficiency (CVI), due to development of more accurate diagnostic methods and new therapeutic techniques. Considering patophysiology of CVI and its consequences the crucial points are stasis and reflux of blood flow, with increase of intravascular pressure. CLASSIFICATION AND THERAPY OF CVI: Empirical experience and theoretical models suggest that progression of the disease can be stopped or reverted by correction of stasis. Today, this is the main direction in all therapeutic approaches. Compression therapy represents the most successful conservative technique. In this article we are presenting basic principles of the compression therapy of CVI. Evidence for the physiologic effect of compression therapy are decrease of edema, softening of lipodermatosclerosis, acceleration of venous flow, decrease in venous volume, blood shift into central compartments, reduction of venous refluxes, influence on arterial flow and improvement of microcirculation and lymph drainage. There are several types of compression devices: elastic stockings, elastic bandages, inelastic bandages, intermittent pneumatic compression devices. Other advantages of compression therapy are decrease of hospital treatment and better quality of life for patients with CVI.

Bandages↗

PubMed2001

Temperature fields during the development of autoignition in a rapid compression machine.

Temperature and concentration fields have been investigated in the cylindrical combustion chamber of a rapid compression machine (RCM) by schlieren photography, chemiluminescent imaging and planar laser induced fluorescence of acetone and of formaldehyde in a 2-dimensional sheet across the diameter. The timescale of particular interest was up to 10 ms after the piston has stopped. Experiments were performed in non-reactive and reactive conditions. Acetone was seeded in non-reactive mixtures. Combustion was studied first in a system containing di-tert-butyl peroxide vapour in the presence of oxygen. The decomposition of di-tert-butyl peroxide generates methyl radicals, which are then oxidised if oxygen is present. The overall reaction is exothermic and is characteristic of a conventional thermal ignition. In addition, chemiluminescence, resulting from CH2O*, accompanies the oxidation process. The combustion of n-pentane was then investigated at compressed gas temperatures that spanned the range in which there is a negative temperature dependence of the overall reaction rate, typically 750-850 K. The response to thermal feedback in this more complex thermokinetic system can be the opposite of the "thermal runaway" that accompanies di-tert-butyl peroxide combustion. The purpose of making comparisons between these two types of systems was to show how the temperature field generated in the RCM is modified in different ways by the interaction with the chemistry and to discuss the implications of this for the spatial development of spontaneous ignition. As the piston of the RCM moves it shears gas off the walls of the chamber. This probably creates a roll-up vortex, but more importantly it also collects gas from the walls and moves it across the cylinder head pushing it forward into a plug at the centre. Thus, soon after the end of compression there is an adiabatically heated gas which extends virtually to the wall, but this incorporates a plug of colder gas at its core. Diffusive transport will occur, but the timescale is relatively slow, and the effect hardly shows until at least 10 ms post-compression. The consequence of "thermal runaway" on a timescale that is compatible with the development of this temperature field is that the reaction rate in the adiabatically compressed toroidal region accelerates faster than in the core, and goes to completion first. A somewhat similar pattern emerges during n-pentane combustion when the initial condition is set at the lower end of the negative temperature dependent range. By contrast, at adiabatically compressed gas temperatures close to the upper end of the negative temperature dependent region, the reaction rate in the cooler core develops faster than that in the surrounding zone, and the temperature difference is rapidly smoothed out. This does not lead to spatial homogeneity in all respects, however, because different rates and extents of reaction generate different concentrations of intermediates. This stratification has implications for the eventual spatial evolution of spontaneous ignition.

Journal Article↗

PubMed2002

Evaluation of pulmonary arterial catheter parameters utilizing intermittent pneumatic compression boots in congestive heart failure.

The use of intermittent pneumatic compression boots to reduce the risk of deep venous thrombosis is contraindicated in patients with congestive heart failure (CHF) due to a theoretical increase in venous return to the heart and exacerbation of heart failure. This study evaluates intermittent pneumatic compression effects on pulmonary artery catheter parameters in CHF patients. We conducted a prospective within-patient study of CHF patients monitored by pulmonary artery catheterization. Hemodynamic variables were assessed with and without the use of intermittent pneumatic compression boots. A sample size of 18 patients was calculated a priori to obtain an 80 per cent power to detect a mean difference of 10 per cent. Twenty patients were studied; no patient suffered hemodynamic instability during the application of pneumatic compression; no statistically significant change in any hemodynamic parameters was noted. A trend toward decreasing mean arterial blood pressure (P = 0.057), pulmonary artery wedge pressure (P = 0.065), and systemic vascular resistance (P = 0.08) was observed. None were clinically significant. The application of intermittent pneumatic compression to the feet of patients in CHF does not significantly alter central hemodynamic parameters in CHF patients. This study suggests that intermittent pneumatic compression may be used in CHF patients for venous thromboembolic risk reduction.

Adult↗

PubMed2001

Microbiological contamination of compressed air used in dentistry: an investigation.

The purpose of this preliminary investigation was twofold: 1) to examine the possibility of cross-contamination between a dental-evacuation system and the compressed air used in dental operatories and 2) to capture and identify the most common microflora in the compressed-air supply. The investigation used swab, water, and air sampling that was designed to track microorganisms from the evacuation system, through the air of the mechanical room, into the compressed-air system, and back to the patient. Samples taken in the vacuum system, the air space in the mechanical room, and the compressed-air storage tank had significantly higher total concentrations of bacteria than the outside air sampled. Samples of the compressed air returning to the operatory were found to match the outside air sample in total bacteria. It was concluded that the air dryer may have played a significant role in the elimination of microorganisms from the dental compressed-air supply.

Aerosols↗

PubMedDate not supplied

Evaluation of sequential intermittent pneumatic compression for filarial lymphoedema.

BACKGROUND: Lymphoedema is a major cause of morbidity in patients with lymphatic filariasis. There is no effective medical treatment and the results of surgery are uncertain. There are very few published studies assessing the volumetric response to the use of sequential intermittent pneumatic compression (SIPC) in patients. METHODS: A 12-celled instrument capable of providing sequential compression from the distal to proximal direction was used in 28 patients with unilateral grades II (n=17) and III (n=11) filarial lymphoedema in a planned 4-week session. The patients were followed up for 6 months after compression therapy by water displacement volumetry. RESULTS: We found that 12 patients with grade II filarial lymphoedema had >26% reduction in oedema volume immediately after compression, but this reduction (>26%) was maintained in only 7 at 6 months. The corresponding figures for grade III filarial lymphoedema were 6 and 4, respectively. The effect in grade III was less sustained than grade II. No complications attributable to SIPC were seen. An added advantage of SIPC was a significant decrease in attacks of adenolymphangitis after compression when compared to pre-compression frequency. These observations were seen even with non-compliance to both foot care measures and use of bandages to maintain reduction in oedema volume. CONCLUSION: SIPC reduces morbidity in filarial lymphoedema though the effect is not sustained. It is simple, easy to use and could form part of the morbidity control programme for lymphatic filariasis.

Adolescent↗

PubMedDate not supplied

[Serous cystadenoma of the pancreas. An occasionally compressive tumor].

Serous cystadenomas of the pancreas are slow growing tumors, rarely compressive and therefore rarely symptomatic. Morphologically typical serous cystadenomas can be safely followed up. We report here three atypical cases of serous cystadenomas compressing either biliary, pancreatic main ducts or splenic vascular pedicle. We analyze from the literature the frequency of these various compressions by different types of cystic pancreatic tumors of the pancreas. Because of the rarity of pancreatic ductal and vascular compressions by serous cystadenomas, the occurrence of such compressions should lead to surgical resection to rule out a pre-malignant or malignant cystic tumor. On the contrary, compression of bile ducts by serous cystadenomas appears as relatively frequent and is therefore less suggestive of potential malignancy. A simple bilio-enteric by-pass can be performed when lesions are morphologically typical of serous cystadenomas and confirmed by surgical biopsy.

Abdominal Pain↗

PubMed2002

The application of a new predictive technique for lossless compression of medical images.

A new predictive technique for lossless compression is applied to CT and MR images in order to achieve high compression in the lossless mode. To accomplish this, a prediction value was obtained by assuming the horizontal and vertical components of each pixel. Wide and narrow predictive coding modes were adaptively selected to achieve an accurate prediction. The performance of the predictive technique was compared with the performance of four representative compression techniques in the lossless mode, using different types of CT and MR image sets with different bit rates. Overall, the proposed predictive technique yielded the best compression, particularly with the lower bit-rate images tested. While the compression results are largely dependent on the images used, the results confirm the strong potential of the proposed predictive technique as a strategy for obtaining high lossless-compression in medical images.

Humans↗

PubMed2003

[Study and clinical application of auto-compressive and anti-rotate intramedullary nail].

OBJECTIVE: To design an auto-compressive and anti-rotate intramedullary nail (ACACIN) and to evaluate the preliminary clinical efficacy on fixing adult femur fracture. METHODS: From January 1998 to June 2001, 23 patients with femur fracture were stabilized with auto-compressive and anti-rotate intramedullary nail. 2-4 elastic blocks were installed into the proximal and distal different distance of quincunx nail to defend rotate and axis compress. RESULTS: Fracture healing were obtained in all 23 patients treated with auto-compressive and anti-rotate intramedullary nail, the time of fracture healing was 6-13 weeks in 21 cases and 15-22 weeks in 2 cases of old fracture. There was no complication related to infection, nail break, abnormal union and joint ankylosis. The results were excellent in 19 cases, good in 3 cases, and moderate in 1 case according Kolmert's criterion for function; the effective rate was 95.7%. CONCLUSION: Auto-compressive and anti-rotate intramedullary nail has a suitable radian for adult femur, can afford stable fixation, anti-rotate and axis compress.

Adolescent↗

PubMed2002

Compression under a mechanical counter pressure space suit glove.

BACKGROUND: Current gas-pressurized space suits are bulky stiff shells severely limiting astronaut function and capability. A mechanical counter pressure (MCP) space suit in the form of a tight elastic garment could dramatically improve extravehicular activity (EVA) dexterity, but also be advantageous in safety, cost, mass and volume. The purpose of this study was to verify that a prototype MCP glove exerts the design compression of 200 mmHg, a pressure similar to the current NASA EVA suit. METHODS: Seven male subjects donned a pressure measurement array and MCP glove on the right hand, which was placed into a partial vacuum chamber. Average compression was recorded on the palm, the bottom of the middle finger, the top of the middle finger and the dorsum of the hand at pressures of 760 (ambient), 660 and 580 mmHg. The vacuum chamber was used to simulate the pressure difference between the low breathing pressure of the current NASA space suits (approximately 200 mmHg) and an unprotected hand in space. RESULTS: At ambient conditions, the MCP glove compressed the dorsum of the hand at 203.5 +/- 22.7 mmHg, the bottom of the middle finger at 179.4 +/- 16.0 mmHg, and the top of the middle finger at 183.8 +/- 22.6 mmHg. The palm compression was significantly lower (59.6 +/- 18.8 mmHg, p<0.001). There was no significant change in glove compression with the chamber pressure reductions. CONCLUSIONS: The MCP glove compressed the dorsum of the hand and middle finger at the design pressure.

Adult↗

PubMed2003

[Diffusion-weighted imaging of acute vertebral compression: Differential diagnosis of benign versus malignant pathologic fractures].

PURPOSE: Our purpose was to assess the value of diffusion-weighted steady-state free precession (SSFP) sequence for differentiating between benign and pathologic compression fractures. MATERIALS AND METHODS: Forty-nine patients with 63 acute vertebral compression fractures caused by osteoporosis (n = 23), trauma (n = 7), malignancy (n = 30), infection (n = 3) were examined with a diffusion-weighted SSFP sequence (diffusion gradient strength; 23 mT/m, diffusion pulse length 5 ms), T1-weighted turbo spin-echo sequence, and short-inversion-time (TI 150 ms) T2-weighted turbo inversion recovery sequence. The signal intensity characteristics were analyzed qualitatively and quantitatively for all sequences. Statistical analysis was performed with the Student's t test. RESULTS: In diffusion-weighted MR imaging, benign osteoporotic and traumatic fractures were hypo- to isointense to adjacent normal vertebral bodies. Pathologic and infectious compression fractures were hyperintense to normal vertebral bodies. Pathologic vertebral fractures had positive bone marrow contrast ratios at diffusion-weighted imaging, whereas non infectious benign vertebral fractures had negative values (p < 0.001). The difference in bone marrow contrast ratios for benign and pathologic compression fractures at T1-weighted TSE and T2-weighted turbo IR was not significant (p > 0.01). CONCLUSION: Diffusion-weighted SSFP sequence provides unique information that significantly impacts the accuracy of radiologic diagnosis. Diffusion-weighted SSFP sequence may allow the differentiation of acute benign osteoporotic fractures from malignant compression fractures. Acute benign osteoporotic or traumatic fractures show hypointense or isointense signal on diffusion-weighted sequences that reflects persistent free water proton mobility. Malignant compression fractures show hyperintensity compared with normal surrounding bone marrow probably due to altered water proton mobility within the neoplasm.

Adult↗

PubMed1992

Data compression of electrocardiograms for long-time digital recording in IC memory.

To realize a digital recorder capable of long-time recording of electrocardiograms (ECGs) in IC memories, the methods of data compression were studied and the accuracy of reconstructed ECGs from the compressed ones was evaluated. Concretely, the variant of MSAPA was used as a data compression algorithm in order to store ECGs in IC memories for 12-24 h. The fabricated digital recorder used an 8 bit CPU with the function of data compression and was capable of operating in real time at a sampling rate of 200 Hz. With bit compression, 24 samples of American Heart Association ECGs were compressed to an average value of 16.8% under the condition of an error limit of 30 microV (120 microV in QRS); the average maximum recording time in 1 Mbyte IC memories was 8.5 h. In a comparison of the reproduction accuracy and errors produced by a small analog tape recorder with those produced by the digital method, the digital system was shown to be superior to the analog system.

Algorithms↗

PubMed1992

[Theoretical and practical bases of compression].

The pressure applied by rigid or elastic compression of the skin surface of a limb is exerted as a function of two parameters. Pressure applied by an elastic tissue acts according to Laplace's law, varying with the tension of the elastic tissue and the radius of the curve of the area compressed. A rigid dressing acts solely by alternating working and resting pressures. Superficial pressure is transmitted to the extra- and intra-fascial compartments through the intermediary of an increase in tissue pressure. This pressure extension acts on all the compressible structures of the limb. It reduces the caliber of the veins in all compartments, and therefore the total venous blood volume of the limb, and increases the rate of circulatory return. The venous pressure adapts itself to the pressure of the dressing. The action on the vessel wall is seen as an increase in fibrinolytic activity and the proliferation of contractile myocytes. Its principal effect, however, is on vascular-tissue integrity: it diminishes interstitial edema and compacts the connective tissue fibrils, decongests the capillary endothelium and reduces the pericapillary sleeve of mucopolysaccharides. But it increases basal membrane thickness. Too high a pressure provokes collapse of the lymphangions. The rheologic action of the compression results in a decrease in blood viscosity. The effect of the compression is to induce local reabsorption of venous edema, while lymphatic edema is displaced towards the root of the limb to a zone where it may be reabsorbed. All these phenomena are reversible on removal of the compression treatment.

Arteries↗