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PubMed2000

Insertion of autologous tendon grafts to the bone: a histological and immunohistochemical study of hamstring and patellar tendon grafts.

This study examined the structure of the insertion of autologous tendon grafts used for anterior cruciate ligament reconstruction. Biopsy specimens of the femoral paragraph signand tibial bone graft interface were obtained at revision surgery in 14 patients (6 with hamstring grafts, 8 with a patella tendon graft). The specimens were analyzed by light microscopy and immunohistochemistry (confirming type I, type II, and type III collagen). The insertions of hamstring autografts to the bone tunnel have three characteristic histological zones. Zone 1 is composed of the dense connective tissue of the graft. The collagen fibers of the graft enter the bone under oblique angles. Zone 2 is composed of woven bone with a sharp transition to the lamellar bone of the tibia (zone 3). Immunohistochemistry revealed the presence of type I and type III collagen within the dense connective tissue of the graft. The woven and lamellar bone showed positive immunostaining for antibodies against type I collagen only. This structure resembled a fibrous ligament or tendon insertion. In the majority of patients with a patella tendon graft the structure of the insertion resembled a chondral enthesis. The chondral insertion of the graft to the bone is composed of four characteristic zones. Between the dense connective tissue of the graft (zone 1) and bone (zone 4) there is a zone of fibrocartilage (zone 2). Close to the bone the fibrocartilage is mineralized (zone 3). Within the fibrocartilage the immunohistochemical analysis confirmed type II collagen. This structure resembled the chondral enthesis of the normal anterior cruciate ligament. However, in cases in which the distal bone bloc has been fixated outside the tibial tunnel, the tibial insertion of the patellar tendon graft resembled a fibrous insertion. While both types of tendon grafts heal to the bone of femur and tibia, the insertion of patella tendon grafts healing by bone plug incorporation resembles the chondral insertion of the normal anterior cruciate ligament and may have a more physiological connection to the bone than hamstring grafts.

Humans↗
PubMed2003

Mechanical testing of small fracture implants for comparison of insertion and failure torques.

INTRODUCTION: Small fracture screws are among the most commonly used implants in the field of orthopedic surgery. The goal of this study was to compare the insertion and failure torques of three screw types: cortical, partially threaded cancellous, and fully threaded cancellous from three manufacturers: Zimmer, Richards, and Synthes. MATERIALS AND METHODS: Each type of screw was subjected to biomechanical tests to determine the insertion ( n=6/group) and failure ( n=10/group) torques. RESULTS: Two-factor ANOVA tests were run to determine whether the insertion or failure torques were different for the different screw types and manufacturers. In the case of insertion torques, neither the screw nor the manufacturer had any significant effect. In the case of failure torque, significant differences were found based on both the screw type and the manufacturer, with the cortical screws manufactured by Zimmer being the strongest. Although there were strength differences, the most important comparison clinically is between the failure torque and the insertion torque of each screw. In all cases, the failure torques were approximately 20 times larger than the insertion torques, and therefore no failures should occur if only torsional loads are applied during insertion. This comparison shows that factors other than screw strength and manufacturing processes may be involved in cases of screw failure during insertion. CONCLUSION: All three screw types from all three manufacturers appear to be mechanically reliable, with the proper insertion to failure torque ratio. The surgeon's choice of implant should be based on other considerations.

Analysis of Variance↗
PubMed2005

Insertional torque of the lumbar pedicle screw during surgery.

The purposes of this study were to determine if the intraoperative insertional torque of pedicle screws correlates with the degree of osteoporosis and if insertional torque can be used as a predictor of screw loosening and clinical results in elderly patients. Pedicle screw fixation was performed in 25 patients. Their mean age at the time of surgery was 72.2 years (range 65-79 years). The mean follow-up period was 2.8 years (range 1.0-4.8 years). The insertional torque of the pedicle screws was measured using a Kannon-type torque wrench with a special connector. In the present study, 136 screws were evaluated. The mean insertional torque was 12.2 +/- 5.0 kgf x cm. A negative relation was found between insertional torque and the grade of osteoporosis. Roentgenograms showed the radiolucency of 18 screws in eight patients. Radiolucency appeared as early as 6 months postoperatively. However, there was no significant relation between insertional torque and the presence of screw loosening. Furthermore, there was no significant difference in the clinical results between patients with low insertional torque and those with high insertional torque. This study demonstrated that intraoperative insertional torque is not an objective predictor of screw loosening or clinical results.

Aged↗
PubMed2000

Inserts--megafillers in composite restorations: a literature review.

Modern insert systems have been available on the dental market since the late 1980s. In general, two major systems can be distinguished: those with and those without preparation instruments in combination with matching standardized inserts. It is claimed that one of the advantages of insert systems is the better marginal adaptation of insert/composite restorations compared to mere composite restorations: the integration of inserts reduces the polymerization shrinkage stress and lowers the overall coefficient of thermal expansion. In vitro data indicate that adapting the insert size to the most precise fit produces a quality of marginal adaptation comparable to that of ceramic inlays. Inserts also facilitate the establishment of a proximal contact. With respect to wear, no significant differences are detected between composite and insert restorations. The bond between insert and composite is susceptible to contamination during operative procedures. Short-term clinical investigations confirm in vitro findings regarding improved marginal adaptation and increased wear resistance. Long-term controlled clinical studies are in progress, but data are not yet available. Based upon the present in vitro and in vivo data it can be concluded that the insert technology shows promising results, but further investigations regarding, for example, stability of the insert/composite bond, fracture resistance of the overall restoration, and wear behavior are necessary to predict the clinical success of this alternative restoration procedure.

Ceramics↗
PubMed1991

Immediate postpartum IUD insertions in a Chinese hospital--a two year follow-up.

A data set consisting of 199 immediate postpartum IUD insertions performed at the Xuan Wu Hospital, Beijing, China was analysed in terms of insertion route, category of inserting personnel and device type. IUD expulsion and continuation of use were the outcome events of interest in this study. Based on our findings, the following hypotheses were derived for future confirmative studies: lower expulsion rates and hence, higher continuation rates of immediate postpartum IUD insertions are associated with (1) insertions through the abdominal incision wound for women who had a cesarean delivery as compared to immediate (less than 10 min) vaginal insertions in women with vaginal delivery; (2) obstetrician insertions, as compared to midwife insertions, and (3) use of the Delta T, as compared to that of the Delta Loop. For the derivation of the latter two hypotheses, only the vaginal insertions were studied.

Adult↗
PubMed1996

Perinatal diagnostic evaluation of velamentous umbilical cord insertion: clinical, Doppler, and ultrasonic findings.

OBJECTIVE: To evaluate the association between velamentous cord insertion and adverse pregnancy outcome in singleton pregnancies, and to assess the diagnostic usefulness of nonstress testing (NST) and Doppler ultrasound in this condition. METHODS: We retrospectively reviewed 12,750 consecutive singleton, chromosomally normal pregnancies from July 1989 through December 1993 at the University Hospital of Kuopio, Finland. Of these, 216 were complicated by velamentous umbilical cord insertion, whereas the remaining 12,534 were normal controls. Using multiple regression analysis, we evaluated the risks by noting adverse infant outcomes: low birth weight (LBW), small for gestational age (SGA), preterm delivery, fetal death, admission to a specific infant care unit, low Apgar scores, neonatal acidemia, and abnormal intrapartum fetal heart rate (FHR) patterns. At prenatal visits, NST and Doppler ultrasound examinations were carried out as a routine part of obstetric care. RESULTS: Even after we controlled for confounding factors, velamentous umbilical cord insertion was associated with higher risk of LBW (odds ratio [OR] 2.32), SGA (OR 1.54), preterm delivery (OR 2.12), low Apgar scores at 1 and 5 minutes (ORs 1.76 and 2.47, respectively), and abnormal intrapartum FHR pattern (OR 1.59). Only 5% of the patients with abnormal insertion showed pathologic NST results at prenatal visits. Ultrasonographic examination was carried out on 80 patients with velamentous umbilical cord insertion as a routine part of obstetric care, and in only one case was direct visualization of the abnormal insertion successful. After we excluded pregnancies with preeclampsia, abnormal umbilical artery Doppler velocimetry was found in none of the cases examined (n = 48). CONCLUSION: There were substantial differences in pregnancy outcome measures between the subjects with velamentous umbilical cord insertion and controls. Current antepartum methods of tracing uteroplacental problems are not effective in the prenatal detection of abnormal insertion. Therefore, in future studies, the use of other diagnostic tools, such as color Doppler imaging of cord insertion, should be evaluated in high-risk pregnancies followed-up because of fetal growth restriction.

Adolescent↗
PubMed1990

Sequence comparison of cellular and viral copies of host cell DNA insertions found in Autographa californica nuclear polyhedrosis virus.

The nucleotide sequence and structural characteristics of two nonhomologous host DNA insertions of Spodoptera frugiperda (fall armyworm) origin isolated from few polyhedra mutants of the baculovirus Autographa californica nuclear polyhedrosis virus (AcMNPV) have been determined. Neither of the host insertions contain long open reading frames suggesting that cellular genes were not introduced into the viral genome. One of the host DNA insertions, IFP1.6, terminated in short imperfect inverted repeats flanked by a duplication of the target sequence, TTAA. Analysis of three cellular copies of this host insertion isolated from a lambda genomic library of S. frugiperda DNA revealed the termini to be highly conserved and also flanked by the same TTAA sequence. IFP1.6 was shown to share homology with a putative host insertion described in the genome of a baculovirus exhibiting wild-type plaque morphology. The second of the host insertions, IFP2.2, had a structure unique among host insertions described in baculoviruses. It lacks terminal repeats but is flanked by duplications of the 8-bp target site sequence. The cellular copy of this insertion was conserved in comparison to the viral copy and was also flanked by a direct 8-bp repeat. This is the first report of the analysis of cellular copies of host DNA insertions frequently associated with baculovirus FP mutants.

Base Sequence↗
PubMed1990

Absorbed power deposition for various insertion depths for 915 MHz interstitial dipole antenna arrays: experiment versus theory.

Dipole antennas are commonly used in interstitial clinical hyperthermia treatments because of their compatibility with brachytherapy techniques and their good power deposition patterns when used in arrays. For accurate treatment planning, however, there must be a comprehensive knowledge base to predict the power deposition patterns when insertion depth is a non-resonant length. This is especially true for insertion depths that result in significant power deposition outside of the antenna junction plane and presumably outside of the tumor volume. A computer controlled measurement system was used with a muscle equivalent phantom to make measurements of specific absorption rate (SAR) or absorbed power per unit mass of tissue at 598 points in a plane. The diagonal plane was the measurement plane of choice because it characterized the SAR profiles at the array center as well as areas in the proximity of the antennas. Dartmouth dipole antennas were used (0.9 mm O.D.) in brachytherapy catheters with inner catheters (2.2 mm O.D./1.2 mm I.D.). The resonant half-wavelength of this dipole antenna/catheter combination is 7.8 cm. A choke modification of the dipole was also investigated. Four antennas were used in a boxlike configuration with 2.0 cm separation. Insertion depths of 5.9, 7.8, 9.8, 12.7, 15.6 and 17.6 cm were used. The hA subsection (junction to tip) was held constant at 3.9 cm. Plots were made of the experimental SAR data normalized to the maximum SAR measured in the plane. Theoretical plots were calculated in the same plane for each of the insertion depths. SAR comparisons were also made longitudinally along the central axis of the array and through the antenna junctions in the diagonal plane for resonant half-wavelength insertion depth. Experimental results verified theoretical predictions of the existence of a secondary hot-spot in the center of the array, but outside of the antenna junction plane and approximately a quarter-wavelength from the insertion point. This secondary hot-spot appears for all insertion depths greater than 10 cm. At longer insertion depths approaching a full wavelength, however, this secondary peak is not dominant. Choke antennas demonstrated a solution to the problem of shifting SAR patterns with varying insertion depths by restricting the active length of the antenna.

Absorption↗
PubMed2004

Glenoid suture anchor fixation strength: Effect of insertion angle.

PURPOSE: The purpose of this study was to determine the effect of varying insertion angles on the fixation strength of screw-in devices placed in the glenoid rim. Type of study Cadaveric biomechanical analysis. METHODS: Eighteen cadaveric glenoids had 3.0-mm cannulated screws inserted for a depth of 10 mm in all 4 quadrants: anterior superior (AS), anterior inferior (AI), posterior superior (PS), posterior inferior (PI). Screws were inserted along the orthogonal to the glenoid rim at the point of insertion or at angles that deviated from this vector by 20 degrees and 40 degrees. Load to failure was performed at 10 mm/s along the orthogonal to the point of insertion. RESULTS: For screws inserted orthogonal to the glenoid rim, the average load to failure was highest for the PS quadrant (733 +/- 369 N) and lowest for the AI quadrant (272 +/- 69 N). The AS and PI quadrants showed intermediate values (549 +/- 334 N and 484 +/- 141 N, respectively). Deviation from orthogonal correlated with decreased fixation strength. This decrease was statistically significant in the AS and PI quadrants, with deviation of 40 degrees, and in the AI quadrant, with deviation of 20 degrees, as well as 40 degrees. Conclusions Insertion angles for screw-in fixation devices should be orthogonal to the glenoid rim at the point of insertion to maximize strength. Deviation of 40 degrees from orthogonal compromises fixation in most quadrants and deviation as little as 20 degrees can compromise fixation in the AI quadrant. CLINICAL RELEVANCE: To maximize strength of labral reattachment to the bony glenoid, screw-in type fixation devices should be inserted as orthogonal to the glenoid rim as possible. This is especially true for Bankart repairs, because device pullout occurs at significantly lower loads in the anteroinferior quadrant compared with the other 3 quadrants. Deviating as little as 20 degrees further decreases fixation strength significantly.

Aged↗
PubMed2005

The anatomic characteristics of the tibial insertion of the posterior cruciate ligament.

PURPOSE: The purpose of the study was to better define the tibial insertion of the posterior cruciate ligament (PCL) and to identify landmarks that could be used to aid in placement of independent tibial tunnels for a 2-bundle PCL reconstruction. TYPE OF STUDY: Descriptive anatomic study. METHODS: Ten knees from 8 cadavers were dissected and the PCL was identified. The ligament was peeled away from its insertion and the sides of the insertion site were measured and recorded. The 4 corners of the insertion site were identified and marked. Observations were made of the morphology of the insertion site and the presence of any reproducible anatomic landmarks. A note was made of landmarks that could be easily identified on all of the specimens by direct vision and by palpation with a probe. RESULTS: The ligament consisted of 2 regions, 1 anterolateral, and 1 posteromedial, with a gradual change in the laxity of the ligament as the knee was passed through flexion and extension. The insertion site was situated in a depression between the plateaus of the tibia and extended below the articular surface. The average length +/- standard deviation of the 4 sides was 128 +/- 21.2 mm (medial side), 107 +/- 26.5 mm (superior side), 160 +/- 30.0 mm (lateral side), and 169 +/- 34.5 mm (inferior side). The shape and sides of the insertion site were visually similar among the 10 specimens. The superolateral and superomedial corners were both represented by depressions and a reproducible ridge represented the inferior border. These structures could be visualized as well as palpated on all specimens. CONCLUSIONS: Based on the findings of this study, we describe the anatomic characteristics of the tibial footprint of the PCL. Anatomic reference points that represent the corners of the tibial insertion of the PCL were identified by direct vision or palpation consistently on all specimens included in the study. These reference points could potentially aid in the placement of an anterolateral and posteromedial tibial tunnel for a 2 tibial tunnel PCL reconstruction. CLINICAL RELEVANCE: Reproducible anatomic reference points exist at the tibial insertion of the PCL that can be identified by direct vision and palpation. These reference points may potentially aid in the placement of separate tibial tunnels for a 2-bundle PCL reconstruction.

Cadaver↗
PubMed2004

An evaluation of electrode insertion techniques for measurement of redox potential in estuarine sediments.

E(h) measurements by electrodes are commonly used to characterize redox status of sediments in freshwater, marine and estuarine studies, due to the relative ease and rapidity of data collection. In our studies of fine-grained estuarine seabeds, we observed that E(h) values measured in intact sediment cores were influenced by different electrode insertion techniques. Sediment E(h) measurements generated via lateral insertion of platinum electrodes through silicone-filled ports in acrylic cores were systematically more positive (on the order of 10-100 mV) than profiles generated via vertical insertion of platinum electrodes downward through the sediment-water interface of the same cores. A review of the literature indicated that while researchers routinely use both insertion techniques to measure E(h), no discrepancy in output has previously been reported. We discuss the results of three experiments conducted to determine if the discrepancy in output was caused by electrode poisoning by sulfides during the stepwise vertical insertion technique, or was caused by contact of the electrode with the silicone plug during the lateral insertion technique. We conclude that contact between the platinum surface of the electrode and the silicone plug biases the E(h) measurements, resulting in erroneously positive E(h) values. Insertion of electrodes into sediment through silicone plugs produced E(h) values that were an average of 105.6 mV (+/-10.4 SE) more positive than values generated upon electrode insertion directly into sediment. Thus, we recommend against using an insertion technique where the platinum electrode remains in contact with the silicone plug, as this method results in misclassification of sediment redox state and estimated depth of the redoxcline.

Electrochemistry↗
PubMed2005

In situ gelling, bioadhesive nasal inserts for extended drug delivery: in vitro characterization of a new nasal dosage form.

The purpose of this study was the preparation and characterization of sponge-like, in situ gelling inserts based on bioadhesive polymers. Hydrophilic polymers (carrageenan, Carbopol, chitosan, hydroxypropyl methylcellulose (HPMC) K15M and E5, sodium alginate, sodium carboxy methylcellulose (NaCMC), polyvinyl pyrrolidone (PVP) 90, xanthan gum) were dissolved with/without the model drug oxymetazoline HCl in demineralized water and lyophilized into small inserts. The drug release, water uptake, mechanical properties, X-ray diffraction and bioadhesion potential of the nasal inserts were investigated. A sponge-like structure of nasal inserts was formed with amorphous, but not with crystalline polymers during the freeze-drying process. The insert hardness increased with the glass transition temperature of the polymer (PVP25<PVP30<PVP90). The bioadhesion potential was governed by the polymer ability to interact with mucin/agar (highest for carrageenan, Carbopol, xanthan gum and NaCMC). Inserts prepared from low molecular weight polymers resulted in polymer dissolution and fast drug release (HPMC E5, Na-alginate, PVP90). The drug release from inserts prepared from high molecular weight polymers (carrageenan, Carbopol, chitosan, HPMC K15M, NaCMC, xanthan gum) was a complex interplay of osmotic forces, water uptake and electrostatic interactions between drug and polymer. The drug release decreased with higher polymer content and increased drug loading of the insert. Bioadhesive nasal inserts have a high potential as new nasal dosage form for extended drug delivery.

Adhesiveness↗
PubMed2005

[Insertion problems, removal problems, and contraception failures with Implanon].

OBJECTIVE: Analysis of the results of a national pharmacovigilance study on Implanon, a contraceptive implant containing 68 mg of etonogestrel. PATIENTS AND METHODS: This survey concerns cases of pregnancies (contraception failures), of migrations and of insertion or removal problems with Implanon reported to French Regional Drug Pharmacovigilance Centres and to Organon SA between May 2001 and September 2002. RESULTS: In France, 39 unintended pregnancies were reported over 17 months. The pregnancies were in 77% of cases (N = 30) due to an insertion technique error (implant not found when pregnancy has been diagnosed). For 3 patients (7,6%), pregnancy was due to a failure of etonogestrel contraceptive effect, explained twice by its association with an enzymatic inductor drug. For 4 patients (10%), pregnancy was due to an untimely insertion (insertion after day 5 of menstrual cycle or woman already pregnant). For two patients, no information was available. The incidence of reported pregnancies in France is estimated at 0.359 / 10(3) implants [0.246-0.482], in accordance with a typical Pearl Index of 0.06 [0.04-0.08]. Twenty-eight suspected migrations (N = 11), problems or failures in removal of the implant (N = 11) and insertion difficulties (N = 6) were notified, corresponding to an incidence of 0.257/10(3) implants [0.162-0.363]. DISCUSSION AND CONCLUSION: Occurrence of pregnancy is possible with Implanon, due to errors in the insertion technique (device not really inserted) or to a non-respect of the SPC recommendations (drug-drug interaction or untimely insertion). Insertion problems can lead to localisation problems (implant not visible by X-ray) then needing further tests and even harmful practice (removal under general anaesthesia). That is why a real and strict training is highly recommended to physicians.

Adult↗
PubMed2006

Structural and functional analysis of the pre-pore and membrane-inserted pore of Cry1Ab toxin.

Bacillus thuringiensis produces insecticidal Cry proteins that are active against different insect species. The primary action of Cry toxins is to lyse midgut epithelial cells in the target insect by forming lytic pores on the apical membrane. After interaction with cadherin receptor, Cry proteins undergo conformational changes from a monomeric structure to a pre-pore-oligomeric form that is able to interact with a second GPI-anchored aminopeptidase-N receptor and then insert into lipid membranes. Here, we review the recent advances in the understanding of the structural changes presented by Cry1Ab toxin upon membrane insertion. Based on analysis of the Trp fluorescence of pure monomeric and oligomeric Cry1Ab structures in solution and in membrane-bound state we reported that oligomerization caused 27% reduction of Trp exposed to the solvent. After membrane insertion there is another conformational change that allows an additional rearrangement of the Trp residues resulting in a total protection of these residues from exposure to the solvent. The oligomeric structure is membrane insertion competent since more than 96% of the Cry1Ab oligomer inserts into the membrane as a function of lipid:protein ratio, in contrast to the monomer of which only 5-10%, inserts into the membrane. Finally, analysis of the stability of monomeric, pre-pore and pore structures of Cry1Ab toxin after urea and thermal denaturation suggested that a more flexible conformation could be necessary for membrane insertion and this flexible structure is obtained by toxin oligomerization and by alkaline pH. Domain I is involved in the intermolecular interaction within the oligomeric Cry1Ab and this domain is inserted into the membrane in the membrane-inserted state.

Bacillus thuringiensis↗
PubMed2005

Islet amyloid polypeptide inserts into phospholipid monolayers as monomer.

Amyloid deposits in the pancreatic islets of Langerhans are thought to be a main factor responsible for death of the insulin-producing islet beta-cells in type 2 diabetes. It is hypothesized that beta-cell death is related to interaction of the 37 amino acid residue human islet amyloid polypeptide (hIAPP), the major constituent of islet amyloid, with cellular membranes. However, the mechanism of hIAPP-membrane interactions is largely unknown. Here, we study the nature and the molecular details of the initial step of hIAPP-membrane interactions by using the monolayer technique. It is shown that both freshly dissolved hIAPP and the non-amyloidogenic mouse IAPP (mIAPP) have a pronounced ability to insert into phospholipid monolayers, even at lipid packing conditions that exceed the conditions that occur in biological membranes. In contrast, the fibrillar form of hIAPP has lost the ability to insert. These results, combined with the observations that both the insertion kinetics and the dependence of insertion on the initial surface pressure are similar for freshly dissolved hIAPP and mIAPP, indicate that hIAPP inserts into phospholipid monolayers most likely as a monomer. In addition, our results suggest that the N-terminal part of hIAPP, which is nearly identical with that of mIAPP, is largely responsible for insertion. This is supported by experiments with hIAPP fragments, which show that a peptide consisting of the 19 N-terminal residues of hIAPP efficiently inserts into phospholipid monolayers, whereas an amyloidogenic decapeptide, consisting of residues 20-29 of hIAPP, inserts much less efficiently. The results obtained here suggest that hIAPP monomers might insert with high efficiency in biological membranes in vivo. This process could play an important role as a first step in hIAPP-induced membrane damage in type 2 diabetes.

Amino Acid Sequence↗
PubMed2005

A comparison of chronic multi-channel cortical implantation techniques: manual versus mechanical insertion.

High-density multi-channel intra-cortical electrode arrays allow researchers to record simultaneously from populations of neurons for the purpose of understanding neural coding and plasticity. These devices have tens to hundreds of electrodes spaced within a few square millimeters. During insertion, the high-density probes can compress the cortex several millimeters prior to breaking through the pia. Compression of cortical tissue has been demonstrated to result in traumatic brain injury (TBI) which may be a major contributor to low electrode yield and decreased recording longevity. Two insertion techniques for chronically implanting multi-wire electrode arrays in layer IV of primary auditory cortex were compared. A mechanical insertion device, capable of rapidly inserting the electrode array without visible compression of the brain, was constructed. The neural responses to broadband clicks and pure tones recorded from the arrays inserted with the mechanical device were compared to the results from a manual insertion method using a micromanipulator. Both techniques result in a similar number of active channels directly following surgery with a mean signal-to-noise ratio of approximately 4.5. Over 60% of the animals implanted with the mechanical insertion device had driven activity at week 6 whereas none of the animals with manually inserted arrays exhibited functional responses after 3 weeks. This report provides initial evidence that mechanical insertion devices, which prevent cortical compression, increase electrode recording longevity.

Acoustic Stimulation↗
PubMed2006

Needle insertion into soft tissue: a survey.

Needle insertion in soft tissue has attracted considerable attention in recent years due to its application in minimally invasive percutaneous procedures such as biopsies and brachytherapy. This paper presents a survey of the current state of research on needle insertion in soft tissue. It examines the topic from several aspects, e.g. modeling needle insertion forces, modeling tissue deformation and needle deflection during insertion, robot-assisted needle insertion, and the effect of different trajectories on tissue deformation. All studies show that the axial force of a needle during insertion in soft tissue is the summation of different forces distributed along the needle shaft such as stiffness force, frictional force and cutting force. Some studies have modeled these forces. The force data in some procedures is used for identifying tissue layers as the needle is inserted or for path planning. Needle deflection and tissue deformation are major problems for accurate needle insertion and attempts have been made to model them. Using current models several insertion techniques have been developed which are briefly reviewed in this paper.

Adipose Tissue↗
PubMed1998

Changes in blood-brain barrier permeability associated with insertion of brain cannulas and microdialysis probes.

Blood-brain barrier (BBB) transcapillary transport was studied after insertion of cannulas and microdialysis probes into the brains of three groups of rats. Quantitative autoradiography was used to measure changes in BBB permeability around the insertion site. In the first group, BBB function was measured with 14C-sucrose at times from immediately, and up to 28 days, after insertion of a microdialysis probe. BBB function was disrupted biphasically: a 19-fold increase in the influx constant (K1) of sucrose occurred immediately after insertion with a second 17-fold increase at 2 days, followed by a slow decline to 5 times normal values at 28 days. In the second group, 14C-dextran (70 kDa) was used to measure BBB transcapillary transport; K1 was increased 90-fold after probe insertion. In the 3rd group, 14C-AIB (alpha-aminoisobutyric acid) was used to evaluate BBB transport after insertion of a 27 gauge cannula, which was used to infuse 1 microliter of saline over 5 min. The K1 of AIB was increased 25 times control values. We conclude that BBB transcapillary transport function is disturbed in response to insertion of brain cannulas and/or microdialysis probes, that BBB dysfunction is maximal at the cannula or probe tip, varies with time after insertion, may persist for at least 28 days after insertion, and occurs over a wide molecular range of solutes. These results suggest caution when using microdialysis as a method to study normal BBB function, and suggest that microdialysis may overestimate the rate of transfer into and out of the brain.

Animals↗