Open Fusion Research Articles

Treatment of Symptomatic Distal Interphalangeal Joint Arthritis with Percutaneous Arthrodesis: A Novel Technique in Select Patients

Arthrodesis of the distal interphalangeal (DIP) joint is a reliable means of achieving pain relief in a symptomatic DIP joint afflicted by a variety of degenerative, inflammatory, or posttraumatic conditions. Successful arthrodesis is more reproducible when rigid compression of the joint is achieved. The emergence of an increasing number of commercially available headless or variable pitch compression screws reflects the growing trend among hand surgeons to utilize rigid stabilization of the DIP joint so that motion at more proximal levels can be initiated immediately without affecting arthrodesis rates. Successful closed percutaneous DIP arthrodesis can be achieved in a patient with hypertrophic osteoarthropathy, passively correctable deformity, and patients at increased risk for perioperative soft tissue complications associated with open arthrodesis. We present a novel percutaneous DIP fusion technique utilizing a cannulated headless compression screw in a select group of patients. The sagittal plane diameters of the distal and middle phalanges are templated. Cannulated headless compression screws, 2.4 and 3.0mm, with short or long terminal threads at the leading end of the screw are selected based upon patient-specific anatomic considerations. Pain-free status and radiographic fusion were achieved in both patients (gout arthropathy, n = 1; posttraumatic arthritis, n = 1) at an average of 6weeks postoperatively. Our current indications, along with pearls and pitfalls with this technique, are reviewed. In select patients, this percutaneous DIP joint arthrodesis is advantageous in comparison with open fusion techniques.

P106. Outcomes of Minimally Invasive Surgery (MIS) Compared to Open Fusion for Spondylolisthesis

BACKGROUND CONTEXT: Spondylolisthesis is a well-defined and focal structural abnormality that can cause significant mechanical back pain, neurogenic claudication, and radiculopathy. Numerous studies have reported excellent outcomes for the surgical treatment of spondylolisthesis in patients that fail to respond to conservative treatment. Although the efficacy and outcomes of open spinal decompression and fusion has been validated for spondylolisthesis, the morbidity associated with open surgery is undesirable.

The Treatment of Concomitant Spine and Hindfoot Injuries

Objective. To analyze diagnosis and treatment results of 38 patients with concomitant injuries to the spine and hindfoot. Material and Methods. Thirty eight patients with concomitant injury to the spine and hindfoot were treated. One group of patients received surgical treatment of injured segments, and another was treated conservatively. All patients have undergone X-ray examination of the injured foot in two planes, estimation of calcaneostragaloid angle and Boehler angle. The spine was studied for the presence of muscle strain and kyphosis. Spondylography in two planes was performed for the assessment of kyphotic deformity, compression degree, and fracture stability. Results. Complete correction of kyphosis was achieved in 86.0% of the second group patients; and in 80.0 % of the first group patients. The mean value of Boehler angle was 21° ± 3° in surgery group and 4° ± 6° in conservative group. In the group of patients with conservatively treated calcaneus fractures the events of posttraumatic arthritis were detected in 9 (64.2%) cases, in the group of operated patients they were detected in 2 (67.0%) cases. Conclusion. Concomitant spine and hindfoot injuries are in most cases the result of catatrauma. The most efficient and reasonable technique of hindfoot fracture treatment is open reduction and fusion with plate and screw instrumentation with utmost accurate reconstruction of joint surfaces.

Extrusion of transmitter, water and ions generates forces to close fusion pore

During exocytosis the fusion pore opens rapidly, then dilates gradually, and may subsequently close completely, but what controls its dynamics is not well understood. In this study we focus our attention on forces acting on the pore wall, and which are generated solely by the passage of transmitter, ions and water through the open fusion pore. The transport through the charged cylindrical nano-size pore is simulated using a coupled system of Poisson–Nernst–Planck and Navier–Stokes equations and the forces that act radially on the wall of the fusion pore are then estimated. Four forces are considered: a) inertial force, b) pressure, c) viscotic force, and d) electrostatic force. The inertial and viscotic forces are small, but the electrostatic force and the pressure are typically significant. High vesicular pressure tends to open the fusion pore, but the pressure induced by the transport of charged particles (glutamate, ions), which is predominant when the pore wall charge density is high tends to close the pore. The electrostatic force, which also depends on the charge density on the pore wall, is weakly repulsive before the pore dilates, but becomes attractive and pronounced as the pore dilates. Given that the vesicular concentration of free transmitter can change rapidly due to the release, or owing to the dissociation from the gel matrix, we evaluated how much and how rapidly a change of the vesicular K +–glutamate − concentration affects the concentration of glutamate − and ions in the pore and how such changes alter the radial force on the wall of the fusion pore. A step-like rise of the vesicular K +–glutamate − concentration leads to a chain of events. Pore concentration (and efflux) of both K + and glutamate − rise reaching their new steady-state values in less than 100 ns. Interestingly within a similar time interval the pore concentration of Na + also rises, whereas that of Cl − diminishes, although their extra-cellular concentration does not change. Finally such changes affect also the water movement. Water efflux changes bi-phasically, first increasing before decreasing to a new, but lower steady-state value. Nevertheless, even under such conditions an overall approximate neutrality of the pore is maintained remarkably well, and the electrostatic, but also inertial, viscotic and pressure forces acting on the pore wall remain constant. In conclusion the extrusion of the vesicular content generates forces, primarily the force due to the electro-kinetically induced pressure and electrostatic force (both influenced by the pore radius and even more by the charge density on the pore wall), which tend to close the fusion pore.

Percutaneous Axial Lumbar Interbody Fusion (AxiaLIF) of the L5-S1 Segment: Initial Clinical and Radiographic Experience

Anterior access to the L5-S1 disc space for interbody fusion can be technically challenging, frequently requiring the use of an approach surgeon for adequate exposure. We reviewed our experience with a novel minimally invasive technique for L5-S1 interbody fusion that exploits the presacral space and its relative dearth of critical structures. 35 patients (20 F:15 M, mean age 54 years) were included in this analysis. Average follow-up was 17.5 months. Back pain was secondary to lumbar degenerative disc disease (DDD), degenerative lumbar scoliosis, or lytic spondylolisthesis. All patients had radiographic evidence of L5-S1 degeneration and underwent percutaneous paracoccygeal axial fluoroscopically-guided interbody fusion (axiaLIF) with cage, local bone autograft, and rhBMP. Mean operative time for the L5-S1 axiaLIF procedure was 42 minutes. Twenty-one patients underwent axiaLIF followed by percutaneous L5-S1 pedicle screw-rod fixation. Two patients underwent axiaLIF followed by percutaneous L4-L5 extreme lateral interbody fusion (XLIF) and posterior instrumentation. Ten patients had a stand-alone procedure. Unfavorable anatomy precluded access to the L5-S1 disc space during open lumbar interbody fusion in 2 patients who subsequently underwent axiaLIF at this level as part of a large construct. Thirty-two patients (91%) had radiographic evidence of stable L5-S1 interbody cage placement and fusion at the last follow-up. The percutaneous paracoccygeal approach to the L5-S1 interspace provides a minimally invasive corridor through which discectomy and interbody fusion can safely be performed. It can be used alone or in combination with minimally invasive or traditional open fusion procedures. It may provide an alternative route of access to the L5-S1 interspace in those patients who may have unfavorable anatomy for or contraindications to the traditional open anterior approach to this level.

Minimally invasive image-guided direct repair of bilateral L-5 pars interarticularis defects

Lower back pain from spondylolysis historically has been treated with a variety of options ranging from conservative care to open fusion. The authors describe the novel technique of minimally invasive bilateral pars interarticularis screw placement by utilizing intraoperative 3D imaging and frameless navigation in a 17-year-old male athlete. This technique is a modification of the open technique first described in 1970 by Buck and has the advantages of minimal dissection requirements with improved screw trajectory visualization. The patient's postoperative course is discussed, followed by a brief literature review of pars interarticularis defect treatment.

Hypotonicity and peptide discharge from a single vesicle.

Neuroendocrine secretory vesicles discharge their cargo in response to a stimulus, but the nature of this event is poorly understood. We studied the release of the pituitary hormone prolactin by hypotonicity, because this hormone also contributes to osmoregulation. In perfused rat lactotrophs, hypotonicity resulted in a transient increase followed by a sustained depression of prolactin release, as monitored by radioimmunoassay. In single cells imaged by confocal microscopy, hypotonicity elicited discharge of the fluorescently labeled atrial natriuretic peptide cargo from approximately 2% of vesicles/cell. In contrast, KCl-induced depolarization resulted in a response of approximately 10% of vesicles/cell, with different unloading/loading time course of the two fluorescent probes. In cell-attached studies, discrete changes in membrane capacitance were recorded in both unstimulated and stimulated conditions, reflecting single vesicle fusion/fissions with the plasma membrane. In stimulated cells, the probability of occurrence of full fusion events was low and unchanged, whereas over 95% of fusion events were transient, with the open fusion pore probability, the average pore dwell-time, the frequency of occurrence, and the fusion pore conductance increased. Hypotonicity only rarely elicited new fusion events in silent membrane patches. The results indicate that, in hypotonicity-stimulated lactotrophs, transient vesicle fusion mediates hormone release.

Temperature Dependence of Fusion Kinetics and Fusion Pores in Ca2+-triggered Exocytosis from PC12 Cells

The temperature dependence of Ca2+-triggered exocytosis was studied using carbon fiber amperometry to record the release of norepinephrine from PC12 cells. Single-vesicle fusion events were examined at temperatures varying from 12 to 28°C, and with release elicited by depolarization. Measurements were made of the initial and maximum frequencies of exocytotic events, of fusion pore lifetime, flux through the open fusion pore, kiss-and-run versus full-fusion probability, and parameters associated with the shapes of amperometric spikes. The fusion pore open-state flux, and all parameters associated with spike shape, including area, rise time, and decay time, had weak temperature dependences and activation energies in the range expected for bulk diffusion in an aqueous solution. Kiss-and-run events also varied with temperature, with lower temperatures increasing the relative probability of kiss-and-run events by ∼50%. By contrast, kinetic parameters relating to the frequency of exocytotic events and fusion pore transitions depended much more strongly on temperature, suggesting that these processes entail structural rearrangements of proteins or lipids or both. The weak temperature dependence of spike shape suggests that after the fusion pore has started to expand, structural transitions of membrane components are no longer kinetically limiting. This indicates that the content of a vesicle is expelled completely after fusion pore expansion.

Conserved Leucines in N-Terminal Heptad Repeat HR1 of Envelope Fusion Protein F of Group II Nucleopolyhedroviruses Are Important for Correct Processing and Essential for Fusogenicity

The heptad repeat (HR), a conserved structural motif of class I viral fusion proteins, is responsible for the formation of a six-helix bundle structure during the envelope fusion process. The insect baculovirus F protein is a newly found budded virus envelope fusion protein which possesses common features to class I fusion proteins, such as proteolytic cleavage and the presence of an N-terminal open fusion peptide and multiple HR domains on the transmembrane subunit F(1). Similar to many vertebrate viral fusion proteins, a conserved leucine zipper motif is predicted in this HR region proximal to the fusion peptide in baculovirus F proteins. To facilitate our understanding of the functional role of this leucine zipper-like HR1 domain in baculovirus F protein synthesis, processing, and viral infectivity, key leucine residues (Leu209, Leu216, and Leu223) were replaced by alanine (A) or arginine (R), respectively. By using Autographa californica multicapsid nucleopolyhedrovirus (AcMNPV) as a pseudotype expression system, we demonstrated that all mutant F proteins incorporated into budded virus, indicating that leucine substitutions did not affect intercellular trafficking of F. Furin-like protease cleavage was not affected by any of the leucine substitutions; however, the disulfide bridging and N-linked glycosylation patterns were partly altered. Single substitutions in HR1 showed that the three leucine residues were critical for F fusogenicity and the rescue of AcMNPV infectivity. Our results support the view that the leucine zipper-like HR1 domain is important to safeguard the proper folding, glycosylation, and fusogenicity of baculovirus F proteins.

Subnanometer Fusion Pores in Spontaneous Exocytosis of Peptidergic Vesicles

Kiss-and-run exocytosis, consisting of reversible fusion between the vesicle membrane and the plasma membrane, is considered to lead to full fusion after stimulation of vesicles containing classical transmitters. However, whether this is also the case in the fusion of peptidergic vesicles is unknown. Previously, we have observed that spontaneous neuropeptide discharge from a single vesicle is slower than stimulated release, because of the kinetic constraints of fusion pore opening. To explore whether slow spontaneous release also reflects a relatively narrow fusion pore, we analyzed the permeation of FM 4-64 dye and HEPES molecules through spontaneously forming fusion pores in lactotroph vesicles expressing synaptopHluorin, a pH-dependent fluorescent fusion marker. Confocal imaging showed that half of the spontaneous exocytotic events exhibited fusion pore openings associated with a change in synaptopHluorin fluorescence but were impermeable to FM 4-64 and HEPES. Together with membrane capacitance measurements, these findings indicate an open fusion pore diameter <0.5 nm, much smaller than the neuropeptides. In stimulated cells, >70% of exocytotic events exhibited a larger, FM 4-64-permeable pore (>1 nm). Interestingly, capacitance measurements showed that the majority of exocytotic events in spontaneous and stimulated conditions were transient. Stimulation increased the frequency of transient events and the fusion pore dwell time but decreased the fraction of events with lowest measurable fusion pore. Kiss-and-run is the predominant mode of exocytosis in resting and in stimulated peptidergic vesicles. Stimulation prolongs the effective opening of the fusion pore and expands its primary subnanometer diameter to enable hormone secretion without full fusion.

Intraoperative electromyography monitoring in minimally invasive transforaminal lumbar interbody fusion

Minimally invasive transforaminal lumbar interbody fusion (TLIF) is an increasingly popular method for achieving lumbar decompression and fusion. The procedure is technically more demanding than open fusion, with correspondingly more theoretical risk of complication. The authors describe the use of intraoperative electromyography (EMG) as an adjunct to surgery to reduce the risk of complications. Between August 2005 and April 2006, 25 consecutive patients underwent minimally invasive TLIF in which a total of 105 pedicle screws were placed. Intraoperative EMG was performed and included passive recordings during decompression and interbody graft placement, as well as active recording during the placement of the pedicle access needle and testing of the pedicle tap. A uniform protocol for active monitoring was used, with the pedicle access needle set at 7 mA. To assess hardware placement, all patients underwent postoperative radiography and 20 underwent postoperative computed tomography (CT) scanning. In no patient did the authors observe significant EMG activation during decompression. In five cases, intermittent nerve root firing was noted after the interbody graft was placed, but this did not correlate with any postoperative deficits. Using the active stimulation protocol, 76.2% of screw placements required one or more changes to the trajectory of the pedicle access needle. With successful placement of the pedicle access needle, in all 105 screws, the pedicle tap nerve root stimulation threshold was greater than 15 mA. Postoperative radiography was performed in all patients and CT scanning was performed in 20 patients (with 85 screws being placed). Postoperative imaging revealed only three cases of pedicle breach. In all cases, the breach was at the lateral wall of the pedicle and not thought to be clinically relevant. A continuous stimulation pedicle access needle alerts the surgeon to incorrect medial trajectories and may lead to safer pedicle cannulation. As a result of electrophysiological feedback, the pedicle access needle trajectory was altered in 76.2% of the reported cases. The use of the authors' protocol resulted in a 0% incidence of clinically relevant malpositioned hardware and a low overall neurological complication rate. Intraoperative nerve root monitoring is a useful adjunct to minimally invasive TLIF.

Enterobacterial Small Mobile Sequences Carry Open Reading Frames and are Found Intragenically–-Evolutionary Implications for Formation of New Peptides

Intergenic repeat units of 127-bp (RU-1) and 168-bp (RU-2), as well as a newly-found class of 103-bp (RU-3), represent small mobile sequences in enterobacterial genomes present in multiple intergenic regions. These repeat sequences display similarities to eukaryotic miniature inverted-repeat transposable elements (MITE). The RU mobile elements have not been reported to encode amino acid sequences. An in silico approach was used to scan genomes for location of repeat units. RU sequences are found to have open reading frames, which are present in annotated gene loci whereby the RU amino acid sequence is maintained. Gene loci that display repeat units include those that encode large proteins which are part of super families that carry conserved domains and those that carry predicted motifs such as signal peptide sequences and transmembrane domains. A putative exported protein in Y. pestis and a phylogenetically conserved putative inner membrane protein in Salmonella species represent some of the more interesting constructs. We hypothesize that a major outcome of RU open reading frame fusions is the evolutionary emergence of new proteins.

Assessment of three major decomposition techniques for sample preparation during elemental analysis of granite rocks

Three main rock-decomposition techniques; microwave oven, open beaker acid and basic fusion were examined in an attempt to establish the most appropriate method for the decomposition of granite rocks for elemental analysis. Standard reference rock material NIM- SARM-I was dissolved using each of the digestion techniques and the solutions analyzed using an Inductively Coupled Plasma-Mass Spectrometery (ICP-MS) analytical system. Element concentration data for Al, Cr, Mn, Fe, Na, Mg, K, Ca, Ti,Co, Ni, Cu, Zn, Ga, As, Rb, Sr, Y, Ba, La, Ce, Pr, Nd, Sm, Ru, Gd, Th, Dy, Ho, Lu, Pb, Cd, Th, and U were obtained. This work shows that no single decomposition technique can adequately attack all the mineral structures containing the elements as is evidence in the agreement or disagreement of the results when compared with the SARM-I certified values. Nigerian Journal of Physics Vol. 16(2) 2004: 15-20

Structural transitions in the synaptic SNARE complex during Ca2+-triggered exocytosis

The synaptic SNARE complex is a highly stable four-helix bundle that links the vesicle and plasma membranes and plays an essential role in the Ca2+-triggered release of neurotransmitters and hormones. An understanding has yet to be achieved of how this complex assembles and undergoes structural transitions during exocytosis. To investigate this question, we have mutated residues within the hydrophobic core of the SNARE complex along the entire length of all four chains and examined the consequences using amperometry to measure fusion pore opening and dilation. Mutations throughout the SNARE complex reduced two distinct rate processes before fusion pore opening to different degrees. These results suggest that two distinct, fully assembled conformations of the SNARE complex drive transitions leading to open fusion pores. In contrast, a smaller number of mutations that were scattered through the SNARE complex but were somewhat concentrated in the membrane-distal half stabilized open fusion pores. These results suggest that a structural transition within a partially disassembled complex drives the dilation of open fusion pores. The dependence of these three rate processes on position within the SNARE complex does not support vectorial SNARE complex zipping during exocytosis.

1399 POSTER A comparison of Gross Tumor Volumes segmented on diagnostic MRI and planning CT with or without post-operative open low-field MRI fusion for 3-D conformal radiotherapy of glioblastomas

1399 POSTER A comparison of Gross Tumor Volumes segmented on diagnostic MRI and planning CT with or without post-operative open low-field MRI fusion for 3-D conformal radiotherapy of glioblastomas

Concentration-Dependent Staining of Lactotroph Vesicles by FM 4-64

Hormones are released from neuroendocrine cells by passing through an exocytotic pore that forms after vesicle and plasma membrane fusion. An elegant way to study this process at the single-vesicle level is to use styryl dyes, which stain not only the membrane, but also the matrix of individual vesicles in some neuroendocrine cells. However, the mechanism by which the vesicle matrix is stained is not completely clear. One possibility is that molecules of the styryl dye in the bath solution dissolve first in the plasma membrane and are then transported into the vesicle by lateral diffusion in the plane of the membrane, and finally the vesicle matrix is stained from the vesicle membrane. On the other hand, these molecules may enter the vesicle lumen and reach the vesicle matrix by permeation through an open aqueous fusion pore. To address these questions, we exposed pituitary lactotrophs to different concentrations of FM 4-64 to monitor the fluorescence increase of single vesicles by confocal microscopy after the stimulation of cells by high K +. The results show that the membrane and the vesicle matrix exhibit different concentration-dependent properties: the plasma membrane staining by FM 4-64 has a higher affinity in comparison to the vesicle matrix. Moreover, the kinetics of vesicle loading by FM 4-64 exhibited a concentration-dependent process, which indicates that FM 4-64 molecules stain the vesicle matrix by aqueous permeation through an open fusion pore.

Synaptotagmin modulation of fusion pore kinetics in regulated exocytosis of dense-core vesicles.

In the exocytosis of neurotransmitter, fusion pore opening represents the first instant of fluid contact between the vesicle lumen and extracellular space. The existence of the fusion pore has been established by electrical measurements, but its molecular composition is unknown. The possibility that synaptotagmin regulates fusion pores was investigated with amperometry to monitor exocytosis of single dense-core vesicles. Overexpression of synaptotagmin I prolonged the time from fusion pore opening to dilation, whereas synaptotagmin IV shortened this time. Both synaptotagmin isoforms reduced norepinephrine flux through open fusion pores. Thus, synaptotagmin interacts with fusion pores, possibly by associating with a core complex of membrane proteins and/or lipid.

Video-Assisted Thoracoscopic Release, Diskectomy, and Fusion

ABSTRACT The use of the video-assisted thoracoscopic approach for anterior release, diskectomy, and fusion in children with kyphosis or scoliosis has evolved with recent advances in minimally invasive surgery. To date, 30 consecutive patients have undergone the video-assisted thoracoscopic approach for anterior release, diskectomy, and fusion, followed by open posterior fusion and instrumentation. The principles behind this approach and the operative experience are described.

The fusion kinetics of influenza hemagglutinin expressing cells to planar bilayer membranes is affected by HA density and host cell surface.

Time-resolved admittance measurements were used to follow formation of individual fusion pores connecting influenza virus hemagglutinin (HA)-expressing cells to planar bilayer membranes. By measuring in-phase, out-of-phase, and dc components of currents, pore conductances were resolved with millisecond time resolution. Fusion pores developed in stages, from small pores flickering open and closed, to small successful pores that remained open until enlarging their lumens to sizes greater than those of viral nucleocapsids. The kinetics of fusion and the properties of fusion pores were studied as functions of density of the fusion protein HA. The consequences of treating cell surfaces with proteases that do not affect HA were also investigated. Fusion kinetics were described by waiting time distributions from triggering fusion, by lowering pH, to the moment of pore formation. The kinetics of pore formation became faster as the density of active HA was made greater or when cell surface proteins were extensively cleaved with proteases. In accord with this faster kinetics, the intervals between transient pore openings within the flickering stage were shorter for higher HA density and more extensive cell surface treatment. Whereas the kinetics of fusion depended on HA density, the lifetimes of open fusion pores were independent of HA density. However, the lifetimes of open pores were affected by the proteolytic treatment of the cells. Faster fusion kinetics correlated with shorter pore openings. We conclude that the density of fusion protein strongly affects the kinetics of fusion pore formation, but that once formed, pore evolution is not under control of fusion proteins but rather under the influence of mechanical forces, such as membrane bending and tension.

Unilateral dislocation of the lumbosacral facet joint: Imaging features

Unilateral dislocation at the lumbosacral junction is a rare injury associated with severe hyperflexion and rotation of the lumbar spine. Plain film findings suggesting facet dislocation are usually confirmed with computed tomography. Most surgeons advocate early open reduction, internal fixation, and fusion.