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PubMed1996

Arthroscopic decompression of a ganglion cyst causing suprascapular nerve compression.

Ganglion cysts causing suprascapular nerve compression are an uncommon cause of suprascapular nerve compression. The advent of magnetic resonance imaging (MRI) and its application in patients with shoulder pain has improved the ability to diagnose cystic lesions causing extrinsic compression of the suprascapular nerve. Traditionally, treatment of suprascapular nerve compression by a ganglion cyst has required open cyst excision through either a deltoid and infraspinatus muscle takedown or a muscle splitting approach. We present three cases of suprascapular nerve compression by a ganglion cyst in which the cyst was decompressed arthroscopically. In each case the patient's symptoms resolved after arthroscopic cyst decompression, and a postoperative MRI does not demonstrate reaccumulation of the cyst fluid. Arthroscopic ganglion cyst decompression is a well-tolerated approach to this problem that avoids the morbidity of an open surgical procedure. The absence of recurrent cyst formation combined with resolution of the symptoms attests to the success of this method.

Adult↗

PubMed1992

[Chronic ulnar nerve compression syndrome at the elbow. Apropos of 74 cases].

Seventy-four patients were operated at Bichat hospital for chronic ulnar nerve entrapment at the elbow between 1982 and 1988. For 62 of them, the etiology of the compression was idiopathic and these cases were treated by neurolysis only or, if the nerve was unstable, by neurolysis associated with medial epicondylectomy. For 12 of them, the etiology of the compression was post-traumatic and these cases were treated by anterior subcutaneous transposition of the nerve using a fat sling. The average follow-up is 28 months and the results take into account the clinical preoperative grading according Mac Gowan's classification: grade I subjective symptoms combined with hypoesthesia in ulnar fingers grade II: weakness and wasting of the interossei combined with subjective symptoms, grade III: marked weakness and wasting of the interossei, adductor pollicis, and hypothenar muscles combined with anesthesia in ulnar fingers. The 62 idiopathic compressions treated by neurolysis only or, if the nerve was unstable, by neurolysis associated with medial epicondylectomy showed 51 very good and good results. The 12 post-traumatic compressions treated by anterior subcutaneous transposition of the nerve using a fat sling showed 9 very good and good results. The authors stress the importance of their approach which takes account of the clinical preoperative grading and the etiology of the compression in order to apply correct surgical treatment.

Elbow↗

PubMed2002

Wax beads as cushioning agents during the compression of coated diltiazem pellets.

Placebo particles were mixed with film-coated diltiazem pellets to evaluate them as cushioning agents during tabletting in order to protect the film coat from damage. The cushioning properties of alpha-lactose monohydrate granules, microcrystalline cellulose pellets and wax/starch beads were evaluated by comparing the dissolution profile of the coated pellets before and after compression (compression force 10 kN). Only the tablet formulations containing wax/starch beads provided protection to the film coat. However, the dissolution rate of tablets formulated with waxy maltodextrin/paraffinic wax placebo beads was too slow as the tablets did not disintegrate. Adding 50% (w/w) drum-dried corn starch/Explotab/paraffinic wax beads to the formulation was the optimal amount of cushioning beads to provide sufficient protection for the film coat and yield disintegrating tablets. Using a compression simulator, the effect of precompression force and compression time on the dissolution rate was found to be insignificant. The diametral crushing strength of tablets containing 50% (w/w) drum-dried corn starch/Explotab/paraffinic wax beads was about 25.0 N (+/-0.3 N), with a friability of 0.4% (+/-0.04%). This study demonstrates that adding deformable wax pellets minimizes the damage to film-coated pellets during compression.

Compressive Strength↗

PubMed1994

Pattern of disease in spinal cord compression on MRI scan and implications for treatment.

Recent trends in the management of bone metastases include the use of prophylactic bisphosphonates and low dose single fraction radiotherapy in favour of high dose fractionated radiotherapy. A recent animal model [1] suggests that cord compression is often associated with predominant soft tissue epidural disease, with bone collapse as a late event. In the present study, potential implications were investigated by retrospective evaluation of the pattern of disease on MRI scans of patients with spinal cord compression. The dominant component of spinal cord compression was determined in 62 patients. Two main patterns were identified, 45 (73%) had predominant soft tissue epidural disease and 15 (24%) had bone collapse. There were two with intrathecal deposits. The patterns were correlated with response to radiotherapy. Positive response was observed in 64% of those with soft tissue epidural disease and 27% of those with bone collapse. These data support the animal model, suggesting soft tissue epidural disease rather than collapse as the predominant cause of cord compression. This implies that prophylactic bisphosphonates alone would be unlikely to reduce the incidence of spinal cord compression. It also introduces concern about the long term safety of low dose single fraction radiotherapy for bone metastases in patients with a medium term life expectancy (e.g. > 2 years). These patients may benefit from more than a single fraction of radiotherapy to produce longer growth delay for sub-clinical epidural disease.

Adolescent↗

PubMedDate not supplied

The inverse effects of load transfer and load sharing on axial compressive stiffness.

BACKGROUND CONTEXT: The goal of spinal instrumentation is to stabilize involved motion segments while fusion occurs. Although some degree of load sharing is necessary for fusion, the ability of the instrumentation system to transfer the load may vary. PURPOSE: The purpose of this study is to formulate a mathematical relationship between load sharing and load transfer of specific spinal instrumentation systems using a well-accepted mechanical model. STUDY DESIGN/SETTING: Forty-eight American Society for Testing Materials standard ultra high molecular weight polyethylene cylinders were used as per designation F 1717-96, standard test methods for static and fatigue for spinal implant constructs in a corpectomy model. METHODS: Twenty-four spinal assemblies consisting of anterior plates, anterior rod, and posterior rods were subjected to compression bending tests using a MTS Bionix servo-hydraulic material testing apparatus. Each implant was tested in compression bending with and without the addition of a titanium load-sharing cage. The force applied was the independent variable, and the displacement was the dependent variable. The stiffness was determined for each setup with and without the addition of an anterior load-sharing cage. RESULTS: The average axial compressive stiffness of a system increased by a factor of 8.5 with the addition of the load-sharing cage. An inverse relationship existed between the compressive stiffness of the construct and its relative increase achieved with the addition of the load-sharing cage. The compressive stiffness of the system with the addition of the load-sharing cage approached that of the anterior device itself as the system flexibility increased. The ability of instrumentation systems to load share or load transfer and their respective stiffness was determined. CONCLUSIONS: The 5-mm rod screw posterior system was compared with the 7-mm Ti posterior system with the addition of one and two devices for transverse traction (DTTs). The rods with the increased diameter had a stiffness of 1723 n/mm with one DTT and 1815 n/mm with two DTTs. The addition of an anterior cage had little effect on the stiffness of these systems. Anterior plate and screw/rod systems were analyzed and showed similar mechanical behavior to the 5-mm posterior rod/screw systems. A significant increase in stiffness was realized with the addition of an anterior cage. A means to determine the load sharing/transferring properties of a spinal instrumentation system is presented. This technique will allow the amount of load transferred from the fusion mass to the instrumentation to be predicted.

Compressive Strength↗

PubMed2001

An evaluation of elastomeric impression materials based on surface compressive strength.

The setting times of seven commercially available elastomeric impression materials were determined using Wilson's reciprocating rheometer at temperatures 23 +/- 0.5 or 32 +/- 0.5 degrees C. The surface compressive strength and depression of these materials after setting time were measured using a rheometer (Fudoh). Each material was mixed according to the mixing proportion (base/accelerator or catalyst ratio) recommended by the manufacturer. The surface compressive strength and the depression of each material were measured by using a method which pressed the material to the edge of a sensitive rod (2.0 mm in diameter) connected to a load cell. In the case of silicone impression materials (additional type) at a temperature of 23 +/- 0.5 degrees C, the surface compressive strength and the depression of these materials were extremely stable after the setting time. However, the surface compressive strength of other materials except additional type materials increased markedly after setting time and the depression corresponding to the surface compressive strength decreased. These increased largely with the increase, in pressing speed to the sensitive rod. At 450 s from the setting time of all materials, there was an adequate correlation (r = 0.84) between measured values and theoretical values derived using the theory of elasticity.

Compressive Strength↗

PubMed1989

Hemicranial attacks or permanent hemicrania--a sequel of upper cervical root compression.

After many years of unsuccessful conservative treatment 16 patients suffering from hemicrania are relieved of their pain or are improved by operative treatment. Hemicranial attacks or permanent hemicrania is found to be caused by upper cervical nerve root compression. Vascular compression of C2 (n = 9) or scar tissue surrounding C2 (n = 1) or C3 (n = 1) is the pathology identified in cases of cervicogenic headache or "cluster headache-like" headache. Compression attributable to tumor, prolapsed disc, or spondylotic changes is found to be a cause of permanent headache. Only in those patients with permanent headache are radiological or electrophysiological findings helpful for diagnosis. In patients with hemicranial attacks and compression of nerve root C2 (n = 10) or C3 (n = 1), only vasoactive tests (provoking or relieving pain) or local anaesthesia prove to be helpful in diagnosing and localizing the origin of pain. The operation involves freeing the nerve roots from vascular compression. In two patients the C2 ganglion is resected. Thirteen patients subsequently become pain free. In three patients, hemicrania improves. Four of the 16 patients experience a recurrence of pain after the decompressive operation. After additional thermorhizotomy two patients have no further complaints and one patient has improved. One patient can tolerate his pain with occasional analgesics. The problem of referred pain into the fronto-ocular region is discussed.

Adult↗

PubMed2001

Evaluation of an acute nerve compression injury with magnetic resonance neurography.

Although magnetic resonance (MR) imaging is performed routinely, current techniques offer little for evaluation of the peripheral nervous system. An animal model was developed to evaluate the appearance and geographic changes associated with an acute nerve compression injury by MR neurography. Several measurements of signal intensity were made for the contralateral noninjured nerve and each sciatic nerve proximal to the site of compression (PN), at the site of compression (CN), and distal to the site of compression (DN) injury. Mean (+/-SEM) values of the MR nerve/muscle signal intensity ratio were 2.24 +/- 0.08 for normal nerve, 2.29 +/- 0.12 for PN, 3.11 +/- 0.31 for CN, and 4.33 +/- 0.47 for DN. There was a statistically significant geographic variation of nerve/muscle signal intensity ratios along the course of the nerve relative to the site of injury that MR neurography could detect. Magnetic resonance neurography may have significant potential to provide more information about problems such as brachial plexus injuries and peripheral nerve compression.

Analysis of Variance↗

PubMed1999

[Compression syndrome of the radial nerve in the area of the supinator groove. Experiences with 110 patients].

Both radial tunnel syndrome and posterior interosseous nerve (PIN) compression syndrome are caused by compression of the posterior interosseous nerve. There is a controversy about certain features of PIN compression especially with regard to diagnostic criteria and therapy as well as differentiation from tennis elbow. From 1992 to 1997, we operated 110 patients because of PIN compression. Diagnosis was based on clinical examination only. As a rule, we decompressed the PIN directly using an anterior approach. With regard to radial tunnel syndrome, we could review 69 from 103 operations with an average follow-up of 41 months. Using the criteria originally proposed by Roles and Maudsley, only 60% showed excellent or good results. The mean DASH score was 32. Recompression of the PIN by scarring was found in as much as 17% of patients and proved to be a serious complication of direct decompression of the PIN. Furthermore, 52% of our patients operated on because of PIN compression suffered from tennis elbow as well. We therefore believe that radial tunnel syndrome is a specific form of tennis elbow. From an anatomical point of view, the inseparable origin of the radial wrist extensors and supinator muscle seems to link tennis elbow and radial tunnel syndrome. To avoid recompression of the PIN by scarring, we have abandoned direct decompression and now routinely use Wilhelm's denervation procedure for the treatment of tennis elbow as well as radial tunnel syndrome. This procedure indirectly decompresses the PIN by cutting the superficial origin of the supinator muscle with consecutive relaxation of Frohse's arcade. Preliminary results are promising and show improvement of preoperative neurologic status by indirect decompression.

Adolescent↗

PubMed1998

Effects of hydroxyethyl-starch-bound deferoxamine on ischemia/reperfusion injury in chronic nerve compression.

The authors have demonstrated previously that pretreatment with deferoxamine, an iron chelator and antioxidant, at the time of release in acute nerve compression, provided protection against ischemia/reperfusion (I/R) injury. In the present study, they evaluated whether therapeutic intervention with hydroxyethyl-starch-bound deferoxamine (HES-DFO) at the time of release of the chronically-compressed peripheral nerve protects the nerve from I/R injury. The sciatic nerves of 43 male Sprague-Dawley rats, weighing 325 to 350 g, were subjected to 8 weeks of compression with Silastic tubing. The treatment group received intravenous HES-DFO (70 mg/kg) at the time of decompression, while the control group received an equal volume of intravenous hetastarch vehicle at the same time schedule and route. Nerve-tissue samples from the compression site, as well as contralateral noncompressed nerves, were assayed for malondialdehyde (MDA), a marker of I/R injury. The control group exhibited MDA levels up to five times normal, and did not return to normal for 21 days. In contrast, the HES-DFO group had MDA levels that were not statistically significantly different from normal levels. The results confirm that pretreatment with HES-DFO prior to the surgical decompression of chronically-compressed nerve provides marked protection against I/R injury.

Animals↗

PubMed1980

[Radial nerve compression syndrome at the elbow with reference to radiohumeral epicondylosis--clinico-anatomic studies].

Compression of the radial nerve in the angle of the elbow can manifest itself clinically as "epicondylosis" ("tennis elbow"). Operative findings and systematic necropsy studies point to four specific areas in which a compression of the radial nerve occurs: 1. Occasionally, firm connective tissue fibers running between the brachialis and brachioradialis extend over the radial nerve in the proximal part of the radial tunnel. 2. Blood vessels may cross the nerve in the angle of the elbow and cause compression. 3. The profundus branch of the nerve may be compressed by the tendon of the extensor carpi radialis brevis when the origin of the muscle is located far medially, and 4. by the tendon of the superficial part of the supinator (arcade of Frohse). These structures can lead to an entrapment neuropathy of the radial nerve, and thereby to an epicondylosis humeri radialis. In patients with clinical symptoms of "epicondylitis" feeling pain along the radial nerve upon application of pressure, the nerve should be exposed to that compressing structures may possibly be released operatively.

Elbow Joint↗

PubMed2006

Shear and compression differentially regulate clusters of functionally related temporal transcription patterns in cartilage tissue.

Chondrocytes are subjected to a variety of biophysical forces and flows during physiological joint loading, including mechanical deformation, fluid flow, hydrostatic pressure, and streaming potentials; however, the role of these physical stimuli in regulating chondrocyte behavior is still being elucidated. To isolate the effects of these forces, we subjected intact cartilage explants to 1-24 h of continuous dynamic compression or dynamic shear loading at 0.1 Hz. We then measured the transcription levels of 25 genes known to be involved in cartilage homeostasis using real-time PCR and compared the gene expression profiles obtained from dynamic compression, dynamic shear, and our recent results on static compression amplitude and duration. Using clustering analysis, we determined that transcripts for proteins with similar function had correlated responses to loading. However, the temporal expression patterns were strongly dependent on the type of loading applied. Most matrix proteins were up-regulated by 24 h of dynamic compression or dynamic shear, but down-regulated by 24 h of 50% static compression, suggesting that cyclic matrix deformation is a key stimulator of matrix protein expression. Most matrix proteases were up-regulated by 24 h under all loading types. Transcription factors c-Fos and c-Jun maximally responded within 1 h to all loading types. Pre-incubating cartilage explants with either a chelator of intracellular calcium or an inhibitor of the cyclic AMP pathway demonstrated the involvement of both pathways in transcription induced by dynamic loading.

Animals↗

PubMed2005

Induction of activating transcription factor 3 (ATF3) by peripheral nerve compression.

Nuclear translocation of activating transcription factor 3 (ATF3), used as a marker for neuronal injury, was studied by immunocytochemistry in sensory neurons in dorsal root ganglia and locally along the sciatic nerve after severe chronic nerve compression in rats. In compressed nerves (application of a narrow silicone tube), ATF3 immunoreactivity was seen in the nucleus of sensory neurons and in Schwann cells below the compression at two and four weeks. Removal of the silicone tube (decompression) at two weeks did not affect the number of ATF3-positive cell nuclei in dorsal root ganglia. No ATF3 immunoreactivity was found in undamaged nerves on the other side. Functional variables (toe spreading and muscle force) were impaired at two weeks, with partial improvement at four weeks. Nerve compression induces nuclear translocation of ATF3, a transcription factor associated with survival and regeneration of sensory neurons. The response is related to duration of compression and partly correlated to function.

Activating Transcription Factor 3↗

PubMed2004

A wavelet-packets based algorithm for EEG signal compression.

Transmission of biomedical signals through communication channels is being used increasingly in clinical practice. This technique requires dealing with large volumes of information, and the electroencephalographic (EEG) signal is an example of this situation. In the EEG, various channels are recorded during several hours, resulting in a great demand of storage capacity or channel bandwidth. This situation demands the use of efficient data compression systems. The objective of this work was to develop an efficient algorithm for EEG lossy compression. In this algorithm, the EEG signal is segmented and then decomposed through Wavelet Packets (WP). The WP decomposition coefficients are thresholded and those having absolute values below the threshold are deleted. The remaining coefficients are appropriately quantized and coded using a run-length coding scheme. The compressed EEG signal can be recovered by an inverse process. Extensive experimental tests were made by applying the algorithm to EEG records and measuring the compression rate (CR) and the distortion in signal segments. The WP transform showed a high robustness, allowing a reasonably low distortion after a compression-decompression process, for CR typically in the range 5-8. The algorithm has a relatively low computational cost, making it appropriate for practical applications.

Algorithms↗

PubMed2006

Microtubules can bear enhanced compressive loads in living cells because of lateral reinforcement.

Cytoskeletal microtubules have been proposed to influence cell shape and mechanics based on their ability to resist large-scale compressive forces exerted by the surrounding contractile cytoskeleton. Consistent with this, cytoplasmic microtubules are often highly curved and appear buckled because of compressive loads. However, the results of in vitro studies suggest that microtubules should buckle at much larger length scales, withstanding only exceedingly small compressive forces. This discrepancy calls into question the structural role of microtubules, and highlights our lack of quantitative knowledge of the magnitude of the forces they experience and can withstand in living cells. We show that intracellular microtubules do bear large-scale compressive loads from a variety of physiological forces, but their buckling wavelength is reduced significantly because of mechanical coupling to the surrounding elastic cytoskeleton. We quantitatively explain this behavior, and show that this coupling dramatically increases the compressive forces that microtubules can sustain, suggesting they can make a more significant structural contribution to the mechanical behavior of the cell than previously thought possible.

Actomyosin↗

PubMed1994

Quality assessment of DSA, ultrasound and CT digital images compressed with the JPEG protocol.

Digital diagnostic images from subtraction angiography, computer tomography and ultrasound grabbed at 640 x 560 pixel and 320 x 280 pixel, eight-bit resolution were compressed at seven different levels with the 'lossy' JPEG algorithm in order to decrease the computer magnetic memory space required for their storage. After reconstruction, the deformations caused by the process were assessed (i) qualitatively: a perception test was performed twice, by five radiologists, on a total of 14 images compressed at various levels and (ii) quantitatively: the average grey level value per pixel was calculated at each compression level from each system's residual images obtained by subtracting the compressed image from the original and taking the absolute value of the result. It was concluded that images compressed at a ratio of about 10:1 were indistinguishable from the originals and hence could be considered acceptable for clinical use.

Algorithms↗

PubMed1985

Spinal cord edema, 5-hydroxytryptamine, lipid peroxidation, and lysosomal enzyme release after acute contusion and compression injury in primates.

Physical and biochemical changes in the spinal cord of monkeys at 1/2, 2, and 4 hours following 200 g cm contusion injury and 50 g of compression injury and 2 hours of decompression following 4 hours of compression were studied. The pathophysiologic changes were milder in compression compared to contusion injury. Following contusion injury, at 1/2 and 2 hours there was significant increase in % water content, lipid peroxidation, and alpha-L-fucosidase. alpha-D-Mannosidase was significantly increased at all time periods, and beta-D-hexosaminidase was increased at 1/2 and 4 hours. At 4 hours following injury, serotonin (5 HT) and 5-hydroxyindole-3-acetic acid (5-HIAA) showed a significant increase. From 10 minutes to 2 hours there was increased platelet aggregation. In compression injury, a significant increase in water content and 5 HT was observed only at 1/2 hour. Lipid peroxidation had increased at all time periods, whereas B-D-hexosaminidase, beta-D-galactosidase, and 5-HIAA were increased at 2 hours. alpha-D-Mannosidase had increased at 1/2 and 2 hours, and alpha-L-fucosidase had increased at 4 hours. After 2 hours decompression following 4 hours compression, water content, beta-D-galactosidase, and alpha-D-Mannosidase were significantly increased. An attempt was made to correlate the findings and to understand the sequential pathophysiologic changes in the first 4 hours following spinal cord trauma, providing a baseline for evaluation of the efficacy of any therapeutic maneuvers.

Acute Disease↗

PubMed2006

Spatiotemporal pattern of macrophage recruitment after chronic nerve compression injury.

The contribution of macrophages to the pathogenesis of chronic nerve compression (CNC) injuries is presently unclear. We examined the time course and spatial localization of macrophage invasion from 24 hours to 28 days post-CNC injury with immunohistochemistry (IHC) and electron microscopy (EM). To clarify the differences in macrophage activity between different peripheral nerve injuries, we compared CNC injury to a nerve crush (CR) injury at similar time points. Entire counts of macrophages with ED1-immunoreactivity (IR) showed a slow, gradual increase in macrophage number from 24 hours to 28 days post-operatively in compressed sections. ED1-IR was greatest at the site of compression and in distal nerve segments with minimal immunostaining in proximal and normal sections. Quantitative analysis of ED1-IR after crush injury demonstrated a rapid time course of macrophage recruitment with ED1-IR peaking at 48 hours and declining to normal values as early as 21 days post-CR injury. Ultrastructural analysis with EM 14 days post-CNC injury revealed greater macrophage localization in the inner one-third region of normal nerves relative to the outer region. Differences in macrophage localization within inner and outer regions of compressed sections were negligible, as macrophages were found diffusely throughout the endoneurium by day 14. Our findings suggest that macrophage recruitment is dependent upon proximity to neural vasculature with relative macrophage density highest specifically around endoneurial blood vessels in both normal and compressed sections. Taken together, our results detail the unique spatiotemporal dynamics of macrophage recruitment early after CNC injury as distinct from a crush injury.

Animals↗