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At least 883 records · Page 49Linked to original sources

PubMed2002

Does thigh compression improve venous hemodynamics in chronic venous insufficiency?

OBJECTIVE: The aim of this study was to investigate the hemodynamic effects of thigh compression in patients with deep venous incompetence. PATIENTS AND METHODS: This diagnostic test study was set in a municipal general hospital. Twelve patients with venous leg ulcers (CEAP classification, C6 Es Ad Pr; four men and eight women), with a mean age of 56.5 +/- 16.8 years, with popliteal venous reflux of more than 1 second detected with duplex scan, underwent investigation with the following methods: 1, the pressure exerted under thigh-length compression stockings class II and short-stretch adhesive compression bandages was measured with an MST tester (Salzmann, Switzerland) and a CCS 1000 device (Juzo, Germany), respectively; 2, the great saphenous vein and the femoral vein on the thigh were compressed with a pneumatic cuff (0, 20, 40, and 60 mm Hg) containing a window through which the diameters of these veins could be measured with duplex ultrasonography; and 3, with the same thigh-cuff occlusion procedure, the venous filling index (VFI) for each experiment was measured with air plethysmography. These values reflected the presence and extent of venous reflux in each experiment depending on the degree of venous narrowing. RESULTS: The mean pressure of a class II compression stocking was about 15 mm Hg at the thigh level, and adhesive bandages achieved a pressure of more than 40 mm Hg in the same location. A statistically significant reduction of the diameters of the great saphenous vein and the femoral vein could be obtained only when the cuff pressure on the thigh was equal to or higher than 40 mm Hg (P <.001). A reduction of the venous reflux (VFI) was achieved only with a thigh pressure of 60 mm Hg (P <.001). No significant reduction was seen of VFI with a thigh pressure in the range of the class II stockings. Previous investigations have shown that, in patients with deep venous incompetence, a pressure cuff on the thigh with 60 to 80 mm Hg is able to reduce ambulatory venous hypertension. CONCLUSION: Thigh compression as exerted with class II thigh-length compression stockings is not able to significantly reduce venous diameter or venous reflux. However, with a pressure of 40 to 60 mm Hg on the thigh that can be achieved with strongly applied short-stretch bandages, considerable hemodynamic improvement, including reduced venous reflux, can be obtained in patients with severe stages of chronic venous insufficiency from deep vein incompetence. The practical value of these preliminary findings should be investigated with further clinical trials.

Bandages↗

PubMed2003

A systematic review of pneumatic compression for treatment of chronic venous insufficiency and venous ulcers.

INTRODUCTION: As part of a reconsideration of coverage policy, the Centers for Medicare and Medicaid Services requested a systematic review of the evidence on the use of pneumatic compression devices in the home environment for treatment of chronic venous insufficiency (CVI) and venous ulcers. METHODS: Articles were found with a systematic literature search of MEDLINE, EMBASE, and AMED (Allied and Complementary Medicine) databases, hand searches of reference lists, and suggestions of experts. RESULTS: Eight trials that met the inclusion criteria, including several randomized control trials, were found. Most studies were small and may have been underpowered. However, several were well-designed randomized controlled trials. Three studies showed that the devices could alleviate symptoms of CVI. No studies directly measured whether the devices could prevent the occurrence of venous ulcers. Some studies on the treatment of venous ulcers did not show a benefit for pneumatic compression, but other studies showed a benefit for the devices in healing long-standing chronic ulcers that had not healed with other methods. No studies directly compared single-chamber and multiple-chamber devices or studied whether the effectiveness of the pump was dependent on types of treatment used concurrently with the pump. Few adverse events were reported in the trials. Patients generally expressed satisfaction with the pneumatic compression devices, and several studies reported higher compliance than with other compression methods. CONCLUSION: The available data cannot be relied on to inform the optimal choice of compression therapy or optimal protocol for patients with CVI or venous ulcers. Methodologically rigorous research designed to answer these questions would be useful for treatment decisions. The Centers for Medicare and Medicaid Services considered the results of this study and issued a decision that pneumatic compression will only be covered for patients with refractory edema with significant ulceration of the lower extremities after a 6-month trial of standard therapies, such as compression stockings, has failed.

Chronic Disease↗

PubMed2005

Excitatory monocyte chemoattractant protein-1 signaling is up-regulated in sensory neurons after chronic compression of the dorsal root ganglion.

Neuronal hyperexcitability in both injured and adjacent uninjured neurons is associated with states of chronic injury and pain and is likely subject to neuroinflammatory processes. Chronic inflammatory responses are largely orchestrated by chemokines. One chemokine, monocyte chemoattractant protein-1 (MCP-1), in the presence of its cognate receptor, the beta chemokine receptor 2 (CCR2), produces neural activity in dissociated neuronal cultures of neonatal dorsal root ganglion (DRG) neurons. Using a neuropathic pain model, chronic compression of the DRG (CCD), we compared anatomically separate populations of noncompressed lumbar DRG (L3/L6) with compressed lumbar DRG (L4/L5) for changes in the gene expression of CCR2. In situ hybridization revealed that CCR2 mRNA was up-regulated in neurons and nonneuronal cells present in both compressed L4/L5 and ipsilateral noncompressed L3/L6 DRGs at postoperative day 5 (POD5). The total percentages of compressed and noncompressed neurons exhibiting CCR2 mRNA transcripts in L3, L5, and L6 DRG were 33 +/- 3.5%, 49 +/- 6.2%, and 41 +/- 5.6%, respectively, and included cell bodies of small, medium, and large size. In addition, the preferred CCR2 ligand, MCP-1, was up-regulated by POD5 in both compressed L4/L5 and noncompressed L3/L6 DRG neurons. Application of MCP-1 to the cell bodies of the intact formerly compressed DRG in vitro produced potent excitatory effects not observed in control ganglia. MCP-1/CCR2 signaling is directly involved with a chronic compression injury and may contribute to associated neuronal hyperexcitability and neuropathic pain.

Animals↗

PubMed2003

Adhesive-cohesive model for protein compressibility: an alternative perspective on stability.

As a dynamic property of folded proteins, protein compressibility provides important information about the forces that govern structural stability. We relate intrinsic compressibility to stability by using molecular dynamics to identify a molecular basis for the variation in compressibility among globular proteins. We find that excess surface charge accounts for this variation not only for the proteins simulated by molecular dynamics but also for a larger set of globular proteins. This dependence on charge distribution forms the basis for an adhesive-cohesive model of protein compressibility in which attractive forces from solvent compete with tertiary interactions that favor folding. Further, a newly recognized correlation between compressibility and the heat capacity of unfolding infers a link between compressibility and the enthalpy of unfolding. This linkage, together with the adhesive-cohesive model for compressibility, leads to the conclusion that folded proteins can gain enthalpic stability from a uniform distribution of charged atoms, as opposed to partitioning charge to the protein surface. Whether buried charged groups can be energetically stabilizing is a fundamental, yet controversial, question regarding protein structure. The analysis reported here implies that one mechanism to gain enthalpic stability involves positioning charge inside the protein in an optimal structural arrangement.

Biochemical Phenomena↗

PubMed2000

The effect of brain compression under venous circulatory impairment.

It is well known that surgical obliteration of the cerebral veins with additional brain compression by retractors is dangerous. To evaluate the mechanism, we studied the change in cerebral microcirculation and parenchymal damage following brain compression with venous circulatory impairment using a rat model. The animals were divided into the following four groups (each n = 5) (1) a sham-operated control; (2) group A, one cortical vein occlusion; (3) group B, a 30 mmHg compression pressure; and (4) group C, one cortical vein occlusion with 30 mmHg compression. The cortical vein was occluded photochemically. Local cerebral blood flow (l-CBF) in the compressed area was measured by stationary laser-Doppler (LD) flowmetry and regional CBF (r-CBF) in the surrounding area was also measured by LD scanning technique for 120 min. l-CBF in the compressed area decreased significantly in groups B and C. A gradual and significant increase in group B and decrease in group C in r-CBF of the surrounding area were observed. Histologically, more extensive damage was observed in group C than in group A and B. The degree of hypoperfusion of the affected brain correlated well with the subsequent brain damage in the experiments. We demonstrated that, compared with vein occlusion or brain compression alone, the accumulated episode caused severe ischemia, then increased the vulnerability of the rat brain to tissue damage.

Animals↗

PubMedDate not supplied

A simulation trial of traditional dispatcher-assisted CPR versus compressions--only dispatcher-assisted CPR.

OBJECTIVES: Growing evidence indicates that it may not be essential to deliver ventilations in the first few minutes of CPR. We compared time to delivery of first compression in traditional CPR with ventilations and compressions to compression-only CPR performed by untrained laypersons assisted by a mock 911 dispatcher. METHODS: This randomized-controlled simulation study included a convenience sample of English-speaking emergency department visitors during a 6-month period. Exclusion criteria were prior CPR training or physical incapacity. A cardiac arrest scenario was presented to subjects who were then provided with one of two sets of telephone CPR instructions by a mock 911 dispatcher. One group received traditional CPR instructions (TCPR) and the second group received compression only CPR instructions (COCPR). Subjects performed CPR on a Laerdal Resusci-Anne CPR manikin and recording strips were analyzed for frequency and quality measures. Pre-and post-test questionnaires assessed subject fatigue and telephone instruction understanding. The primary outcome was the time interval from 911 call to initiation of chest compressions. Analysis included Student t-test, Chi-square, and Wilcoxon Rank Sum. RESULTS: Of 377 potential subjects, 54 consented to randomization. The data from 50 subjects were analyzed. Compared to group TCPR, group COCPR initiated chest compressions faster (72 vs 117 sec, p < 0.0001), completed four cycles of CPR faster (168 vs. 250 sec, p < 0.0001), and paused for a smaller percentage of the resuscitation (13% vs. 36%, p < 0.0001). Only 9% of ventilation opportunities in the TCPR group yielded ventilations of the correct volume. There were no differences between groups in perceived understanding of CPR instruction or fatigue. CONCLUSIONS: We have identified the potential timesavings that may occur during compressions-only CPR. Bystander resuscitation may be more efficient when ventilations are excluded from the CPR sequence.

Adult↗

PubMedDate not supplied

A randomized, controlled trial of the efficacy of closed chest compressions in ambulances.

OBJECTIVE: To examine the feasibility of closed chest compressions in ambulances. METHODS: Ten male emergency medical technicians performed closed chest compressions on a Laerdal Skillmeter Resusci Anne placed 1) on the ground, 2) on the stretcher of an MB 510 ALS ambulance, 3) on the stretcher of an MB 310 ambulance, and 4) on the stretcher of a VW T4 BLS ambulance for 2 minutes each. The authors noted the percentage of correct compressions as shown by the mannequin and counted the heart rate of the participants before and after each session. The authors compared the percentage of correct compressions and the increase in heart rate during the three ambulance sessions with those of the session on the ground by rank order test for paired observations. A p < 0.05 after Bonferroni correction (factor 3) was considered significant. RESULTS: The percentage of correct compressions was 90% +/- 7% on the ground, 77% +/- 19% in the MB 510, 60% +/- 31% in the MB 310, and 38% +/- 24% in the VW T4. Heart rate increase was 18 +/- 16 min-1 on the ground, 23 +/- 9 min-1 in the MB 510, 30 +/- 16 min-1 in the MB 310, and 32 +/- 13 min-1 in the VW T4. Only the difference in percentage of correct compressions between on the ground and the VW T4 was significant (p < 0.01 after Bonferroni correction). CONCLUSIONS: The percentage of correct compressions in all the vehicles tested was lower when compared with the percentage on the ground, and the increase in heart rate was higher. Only one of these results was statistically significant. A further study with more participants seems warranted.

Adult↗

PubMed2002

Treatment of femoral pseudoaneurysms. Percutaneous US-guided thrombin injection versus US-guided compression.

PURPOSE: Thrombin injection in femoral pseudoaneurysms has been suggested to be superior to traditional US-guided compression. Our aim was to evaluate results with compression therapy with special reference to use of thrombin in case of failure. We also studied 7 patients who underwent primary thrombin injection. MATERIAL AND METHODS: We retrospectively reviewed all (n=44) femoral artery pseudoaneurysms diagnosed at our department during October 1998-May 1999. US-guided compression with the Femostop device or US-guided thrombin injection (100-1000 IU) was the first choice according to the physicians' preference, followed by the other regime if the first choice was non-successful. RESULTS: Thirty-nine (89%) of the patients received anticoagulation treatment and/or concomitant antiplatelet drugs. Out of the 44 patients, 37 were treated with compression as the first choice. This regime was successful in 22 (59%). This group included 2 lesions that resolved spontaneously after initially failed compression and 1 deep venous thrombosis after treatment. The persistent 15 pseudoaneurysms after failed compression received thrombin injection, and it was also the primary therapy in 7 patients. Complete thrombosis within the pseudoaneurysm was immediately induced after treatment. One early recurrence required a second injection. No complication of thrombin was noted and no surgery was required. CONCLUSION: US-guided thrombin injection is an effective treatment for embolisation of pseudoaneurysms. The technique is superior to compression therapy.

Aged↗

PubMed2006

Effects of prolonged compression on the variations of haemoglobin oxygenation - assessment by spectral analysis of reflectance spectrophotometry signals.

The consequences of rhythmical flow motion for nutrition and the oxygen supply to tissue are largely unknown. In this study, the periodic variations of haemoglobin oxygenation in compressed and uncompressed skin were evaluated with a reflection spectrometer using an in vivo Sprague-Dawley rat model. Skin compression was induced over the trochanter area by a locally applied external pressure of 13.3 kPa (100 mmHg) via a specifically designed pneumatic indentor. A total of 19 rats were used in this study. The loading duration is 6 h per day for four consecutive days. Haemoglobin oxygenation variations were quantified using spectral analysis based on wavelets' transformation. The results found that in both compressed and uncompressed skin, periodic variations of the haemoglobin oxygenation were characterized by two frequencies in the range of 0.01-0.05 Hz and 0.15-0.4 Hz. These frequency ranges coincide with those of the frequency range of the endothelial-related metabolic and myogenic activities found in the flow motion respectively. Tissue compression following the above loading schedule induced a significant decrease in the spectral amplitudes of frequency interval 0.01-0.05 Hz during the pre-occlusion period on day 3 and day 4 as compared to that on day 1 (p < 0.05). In contrast, at a frequency range of 0.15-0.4 Hz, prolonged compression caused a significant increase in spectral amplitude during the pre-occlusion period in the compressed tissue on day 3 (p = 0.041) and day 4 (p = 0.024) compared to that in the uncompressed tissue on day 1. These suggested that the variations of the haemoglobin oxygenation were closely related to the endothelial-related metabolic and myogenic activities. Increased amplitude in the frequency interval 0.15-0.4 Hz indicated an increased workload of the vascular smooth muscle and could be attributed to the increase of O(2) consumption rates of arteriolar walls. The modification of vessel wall oxygen consumption might substantially affect the available oxygen supply to the compressed tissue. This mechanism might be involved in the process leading to pressure ulcer formation.

Animals↗

PubMed2001

Effectiveness of radiological image data compression.

This study was designed to evaluate effectiveness of radiological image data compression in terms of image quality and archiving material costs using DLT tapes, and to assess the relationship between loss of quality and cost savings. Six radiologists used Subjective Fidelity Criteria (SFC) in random fashion to evaluate the quality of 105 digitally acquired radiological images. In addition, 5 radiologists and 2 nonradiologists evaluated at random three phantom images exposed in conditions mimicking chest, bone, and colon examinations, displayed in five modes (a total of 15 images). Both patient images and phantom images were submitted to 3:1 (Ziv-Lempel method) and 10:1 compression (wavelet-based compression method). Cost information on material cost savings and the effect of compression on tape space requirements were compared. The results indicate that image quality was not degraded using either of the compression ratios. The interobserver proportion of agreement exceeded overwhelmingly the limit of a good proportion of agreement regarding each compression ratio and each image type. The divergence in the rest of the assessments was not consistent. The adoption of 10:1 compression would not bring a substantial decrease of archiving costs as compared to the total yearly operating costs, and especially as considering the consequences of possible image quality deterioration.

Chi-Square Distribution↗

PubMed2004

The effects of decompression and exogenous NGF on compressed cerebral cortex.

Using a rat epidural bead implantation model, we found that compression alone could reduce the overall and individual layer thicknesses of cerebral cortex with no apparent cell death. The dendritic lengths and spine densities of layer II/III and V pyramidal neurons started to decrease within 3 days of compression. Decompression for 14 days resulted in near complete to partial recovery of the cortical thickness and of the dendritic lengths of layer II/III and V pyramidal neurons, depending on the duration of the preceding compression. The recoverability was better following short (3-day) than long (1- or 3-month) periods of compression. The loss of dendritic spines nevertheless persisted. An intraventricular infusion of NGF was performed after decompressing the lesions following 3 days of cortical compression, and this increased the recovery of the spines but not the dendritic length of the cortical pyramidal neurons, nor did it alter the recovery of the cortical thickness. NGF also promoted the increase of the dendritic spines, but not the dendritic length of the cortical pyramidal neurons of normal animals. In short, the data show that a few days of compression alone can cause permanent cortical damage. Exogenous NGF, if applied topically, may restore the dendritic spine density of cortical neurons subjected to compression.

Animals↗

PubMed2001

The relationship of the compressive modulus of articular cartilage with its deformation response to cyclic loading: does cartilage optimize its modulus so as to minimize the strains arising in it due to the prevalent loading regime?

AIM: To investigate the relationship of the instantaneous compressive modulus with its deformation response to cyclic loading typical of that encountered at the knee joint during level walking. METHOD: The study was performed on 24 osteochondral plugs taken from three unembalmed cadaveric knees. As the compressive modulus of cartilage has been shown to vary topographically across the knee in an established manner, the specimens were taken from specific sites on the femur and tibia of each knee. All the cartilage specimens were immersed in Hanks' salt solution at 37 degrees C and were subjected to the same cyclic loading regimen that was representative of a typical walking cycle in a specialized indentation apparatus, for over 1 h. RESULTS AND CONCLUSION: The viscous and elastic components of matrix strain, the creep rate and the cartilage compressive modulus were measured. The latter was found to be significantly related to the strain response of cartilage to cyclic loading. Elastic strain varied exponentially with the compressive modulus; specimens with a modulus less than 4 MPa experienced elastic strains in the range 0.18-0.36, whereas stiffer specimens experienced strains between 0.05 and 0.13. Viscous strain varied linearly with cartilage stiffness and was as low as 0.02 at the lower values of the compressive modulus but increased to 0.22 for a compressive modulus of 18 MN/m(2). The rate of creep under cyclic load was inversely linearly related to cartilage stiffness. The strain response of soft specimens approached steady state by 200 cycles but that of stiff specimens did not approach it until 1300 cycles. It was hypothesized that the viscous strain response of cartilage can be explained in terms of differences in permeability between specimens of different compressive modulus, stiffer cartilage having a lower permeability than soft cartilage.

Cadaver↗

PubMed1988

Effect of cardiopulmonary resuscitation compression rate on end-tidal carbon dioxide concentration and arterial pressure in man.

The optimal rate of chest compression during CPR in man has been debated. Recently, the end-tidal carbon dioxide concentration (PetCO2) has been shown to correlate with cardiac output during CPR in experimental animals. Eighteen prehospital cardiac arrest patients were studied to determine the effect of external chest compression rate on the PetCO2 and BP in man when ventilation rate, ventilation inspiration time, applied compression force, and a 50:50 downstroke:upstroke ratio were held constant using a microprocessor-controlled CPR Thumper. Compression rate was increased from 60 to 140/min in 20 beat/min increments. The PetCO2 was 1.7 +/- 0.2% at a compression rate of 60/min and did not change significantly at increased rates. Systolic BP fell progressively from 59 +/- 5 mm Hg at 60/min to 46 +/- 4 mm Hg at 140/min. Diastolic BP remained approximately 23 mm Hg at all rates studied. Using a CPR manikin, we found that greater Thumper compression force was necessary to sustain the same sternal displacement and to achieve the same applied sternal pressure when the rate was increased due to a rate-limited fall in the compression duration.

Aged↗

PubMed1999

Quantifying the contribution of audibility to recognition of compression-amplified speech.

OBJECTIVE: The speech-recognition advantages of wide-dynamic range compression (WDRC) hearing aids are believed to be a direct result of improved audibility. The main objective of this study was to compare the relationship between increasing audibility and recognition for compression-amplified versus linearly amplified speech, using a quantitative measure of audibility. A second objective was to explore the adequacy of the Aided Articulation Index (Stelmachowicz, Lewis, Kalberer, & Creutz, 1994) in describing performance with WDRC-amplified speech. DESIGN: Sixteen listeners with mild to severe sensorineural hearing loss were tested on recognition of nonsense syllables that had been digitally processed with linear or WDRC amplification. Speech recognition scores were obtained for three input levels that differed in audibility relative to the listeners' hearing thresholds. An Aided Audibility Index (AAI), ranging from 0.0 (inaudible) to 1.0 (fully audible), was calculated for each listener and condition. This importance-weighted index represents the portion of the speech signal that is available to the listener. The relationship between audibility and recognition was then examined for each type of amplification. RESULTS: At low and moderate input levels, AAI values and corresponding recognition scores were higher for the compression-amplified than for the linearly amplified speech. At high input levels, AAIs and recognition scores were essentially the same for both types of amplification. Recognition scores increased monotonically as a function of the AAI for both linear and WDRC amplifiers. There was no significant difference between the functions for linearly amplified versus compression-amplified speech. In other words, a given increase in audibility resulted in the same increase in recognition for both types of amplification. CONCLUSIONS: Increasing the amount of audible speech information plays the same role in recognition for compression-amplified as for linearly amplified speech. This suggests that, at least for the conditions tested here, compression does not introduce detrimental changes to the speech signal that offset the benefits of improved audibility. Accuracy of the compression-amplified AAI can be improved by substituting measured speech ranges for the estimated speech ranges used in the standard AAI calculation. In the absence of measured speech ranges, the standard AAI provides a close approximation.

Aged↗

PubMed1993

The effect of irreversible image compression on diagnostic accuracy in thoracic imaging.

RATIONALE AND OBJECTIVES: Digital image compression reduces the storage requirements and network traffic on picture archiving and communications systems. Full-frame bit-allocation (FFBA) is an irreversible image-compression method based on the discrete cosine transform that provides for high compression ratios with a high degree of image fidelity. METHODS: One hundred twenty-two posteroanterior chest radiographs were obtained on patients in an ambulatory patient setting, including 30 cases of interstitial lung disease, 45 images containing combinations of lung nodules (N = 37) or mediastinal masses (N = 39), and 47 normal images containing none of the pathology for which we were testing. The images were digitized (nominal 2 K x 2 K x 12-bit resolution), printed on a 35 x 35-cm hard copy format, and compressed at an approximate compression ratio of 20:1. Observer performance tests were conducted with five radiologists using receiver operating characteristics analysis on digitized uncompressed and compressed hard copy images. RESULTS: There were no significant differences between the two display conditions for the detectability of any of the thoracic abnormalities. CONCLUSIONS: Our preliminary results suggest that irreversible image compression at ratios of 20:1 may be acceptable for use in digital thoracic imaging.

Algorithms↗

PubMed1998

Wavelet versus JPEG (Joint Photographic Expert Group) and fractal compression. Impact on the detection of low-contrast details in computed radiographs.

RATIONALE AND OBJECTIVES: The aim of this study was to evaluate different lossy image compression algorithms in direct comparison. METHODS: Computed radiographs were reviewed after compression with Wavelet, Fractal, and Joint Photographic Expert Group (JPEG) algorithms. For receiver operating characteristic (ROC) analysis, 54 thoracic computed radiographs (31 showing pulmonary nodules) were compressed with a ratio of 1:60. Five images of a test-phantom were coded at 1:13. All images were reviewed on a PC. Uncompressed images were reviewed at a PC and at a radiologic workstation (with image processing). RESULTS: For thorax images, decrease of diagnostic accuracy was significant with Wavelets. Fractal performed worse than Wavelets. No ROC curve was observed for JPEG due to poor image quality. No diagnostic loss was noted comparing PC and Workstation review. For low-contrast details of the phantom, results of Wavelet compression were equal to uncompressed images. Fewer true positives and increased true negatives were noted with Wavelets though. Wavelets were superior to JPEG, and JPEG images were superior to Fractal. Workstation review was superior to PC review. CONCLUSIONS: Only Wavelets provided accurate review of low-contrast details at a compression of 1:13. Frequency filtering of Wavelets affects contrast even at a low compression ratio. JPEG performed better than Fractal at low and worse at high compression ratio.

Algorithms↗

PubMedDate not supplied

Evaluation of vascular compression in trigeminal neuralgia by 3D time-of-flight MRA.

OBJECTIVE: Our goal was to assess the usefulness of 3D images in the preoperative evaluation of 16 patients with surgically confirmed trigeminal neuralgia. MATERIALS AND METHODS: The axial source images from 3D TOF MRA were evaluated for a total of 32 sides by two observers in a blinded manner, focusing on the presence of the neurovascular compression and the identification of compressing vessels. All 3D images including coronal orientation and gadolinium-enhanced images were reviewed retrospectively by another two observers together with the surgical findings. RESULTS: In the blinded study with axial 3D images, the sensitivity was 75 and 75% with a specificity of 75 and 69% for observers A and B, respectively. By reviewing the coronal images, the relationship between trigeminal nerve and vessels became clearer, especially in sandwich-type compression. With gadolinium-enhanced images, three vessels that were not shown in the nonenhanced images could be identified. On the asymptomatic side, vascular compression could not be excluded retrospectively in five cases. CONCLUSION: Nonenhanced axial images may not display small arteries or veins that are compressing the trigeminal nerve. Gadolinium enhancement will be necessary for those patients without demonstrable compression on nonenhanced examination. Coronal images are also helpful in the evaluation of vascular compression.

Adult↗

PubMed2003

Biomechanical evaluation of a new type of hip compression screw with retractable talons.

OBJECTIVES: We investigated the biomechanical performance of a compression hip screw with four reversibly deployable talons. We hypothesized that the talons would increase purchase strength of the lag screw and prevent rotation of the femoral head by resisting torsional forces between the lag screw and the femoral head. DESIGN: Reproducible, stable two-part intertrochanteric fractures were created on matched pairs of embalmed human femurs. Fractures were fixed using the compression hip screw with either the talons deployed (talon) or not deployed (screw) configuration. Pre- and postimplantation radiographs and dual energy x-ray absorptiometry scans were used to ensure geometric and balanced equivalency between contralateral limbs. Torsional tests were performed on femoral pairs at 1 Hz for 5000 cycles prior to torque failure. Compression tests were performed on femoral pairs with the screw in the inferior or central position. RESULTS: Peak torque and torque at 15 degrees of rotation were significantly greater for the talon versus screw device (6.5 +/- 1.7 Nm vs. 1.9 +/- 1.7 Nm for peak torque, P = 0.0002; and 4.2 +/- 2.0 Nm vs. 1.2 +/- 1.2 Nm for torque at 15 degrees rotation, P = 0.003). The peak compressive forces generated by the talon device were significantly greater than for the screw device in the inferior position (P = 0.005), with compression values of 1398 +/- 467 N and 713 +/- 323 N, respectively. Peak compression forces did not differ significantly between talon and screw devices in the central position. CONCLUSIONS: Talon deployment significantly improved interfragment compression and torsional strength. Engagement or penetration into or through the cortical bone at the base of the femoral head-neck junction in the inferior lag screw position is the critical technical step to maximize the talon purchase.

Adult↗