Superior Part Research Articles

A Case of Simultaneous Sinus Augmentation and Oroantral Fistula Closure for Implant Preparation.

An oroantral communication (OAC) may form in the upper molar region after tooth extraction. The patient is a 59-year-old female, who is a non-smoker. At the initial visit, teeth #14, #15, and #17 were missing. After tooth #16 was extracted due to apical periodontitis, a bone defect with a diameter of approximately 4 mm was observed, leading to the formation of an oroantral fistula (OAF). Another window was created in the lateral wall adjacent to the superior part of the bone defect at the fistula site to achieve closure of the OAF through bone formation and simultaneously perform sinus floor elevation (lateral approach) for implant placement. Through this lateral window, instruments were inserted into the maxillary sinus towards the bone defect at the fistula site. During this process, the remaining bone between the lateral window and the bone defect at the fistula site was carefully removed with instruments, connecting the two bone defects to facilitate the manipulation of the instruments. The Schneiderian membrane was elevated without enlarging the tear. Six months after these surgeries, a CBCT scan confirmed the closure of the fistula with hard tissue and the elevation of the sinus floor. Subsequently, three implants were placed, and prosthetic treatment was completed. Follow-up data is provided, including periapical X-ray and CBCT images taken two years and three months after surgery (one year and three months after the placement of the final prosthetic structure). The progress so far has been favorable.

Feasibility and safety of preauricular incision for extracapsular dissection in benign parotid tumors.

Parotidectomy techniques continuously evolve to improve outcomes while minimizing morbidity. This study investigates the rationale behind developing and evaluating the feasibility and safety of extracapsular dissection (ECD) via preauricular incision for benign parotid tumors in the anterior or superior part of the parotid gland. The preauricular approach is developed to address the increasing demand for minimally invasive techniques that prioritize both functional and aesthetic outcomes. Minimizing visible scarring and preserving facial nerve function offers a compelling solution for patients seeking optimal cosmetic results without compromising surgical efficacy. Patient assessments included cosmetic contentment, functional repercussions, and disease management throughout the follow-up. Eight patients underwent ECD via the preauricular approach, demonstrating favorable outcomes with preserved facial nerve function and minimal complications. This study highlights the potential of the preauricular approach as a preferred option for managing benign parotid tumors in the anterior or superior parotid region, emphasizing aesthetic outcomes and preserving gland function. IV.

Superior approach to the glenoid for treating acromion fractures combined with ideberg type III scapular glenoid fractures: a technical note.

Scapular glenoid fractures, categorized based on the Ideberg classification, are commonly addressed surgically through approaches like the anterior deltoid-pectoral approach, posterior Judet approach, modified Judet approach, or posterior axillary approach. However, these methods present limitations in exposing the superior part of the glenoid. Therefore, we propose an approach for patients with concomitant acromion fractures, involving the anterior lateral flipping of the fractured acromion, allowing direct superior visualization of the superior and posterior superior parts of the glenoid. Retrospective analysis was conducted on the data of five patients with shoulder fractures combined with scapular Ideberg III fractures between June 2018 and May 2023. All patients were treated using the shoulder approach above the scapular spine. There were four males and one female, aged 23-54 years with an average age of 36.6 years. One case involved the left shoulder, and four cases involved the right shoulder. X-rays and CT were taken before and after surgery to assess the location of the fractures and the healing status. Clinical evaluation included the assessment of efficacy using the Constant-Murley scoring criteria and analysis of surgical complications. All five patients were followed up for a duration of 14-36 months. All fractures healed completely, with an average healing time of 4.3 months (range: 3-6 months). There were no complications such as suprascapular nerve injury, nonunion, wound infection, or shoulder joint instability observed postoperatively. At the final follow-up, the Constant-Murley shoulder joint function score ranged from 84 to 98 points, with an average of 91.4 points. Three patients achieved an excellent rating in shoulder joint function score, while two patients achieved a good rating. The shoulder approach above the scapular spine exhibits advantages such as easy exposure and reduction, minimal intraoperative trauma, and clear visualization.

Alterations in optical coherence tomography and optical coherence tomography angiography findings in children with partial biotinidase deficiency.

The aim of the study was to investigate whether retinal neurovascular structural impairment in children with partial biotinidase deficiency (BD) could be detected early via optical coherence tomography (OCT) and OCT angiography (OCTA). Eighty patients with partial BD and 80 control cases without any known systemic or ocular diseases were enrolled in this prospective study. Retinal neurovascular structures in the macular and optic disc regions were examined in using OCT and OCTA. Data from subjects with partial BD were compared with data from healthy controls. A statistically significant decrease in the vessel density (VD) was observed in both superior and inferior parts of the superficial capillary plexus (SCP) and the deep capillary plexus (DCP) in the partial BD patient group compared with the control group (p<0.05). A significant decrease in the VD was also observed in the superior and inferior peripapillary SCP-DCP regions of the optic disc area in the patients with partial BD (p<0.05). Both the superficial and deep foveal avascular zone (FAZ) areas were significantly enlarged in the partial BD group with respect to the control group (p=0.026, p=0.021 respectively). In the partial BD patients, the vascular density in the macula and optic disc region is decreased in childhood, when compared to the control group. In patients with partial BD, it would be very useful to detect the early neurovascular changes that may occur during the course of the disease by means of a noninvasive technique such as OCTA.

The classification of sacral foramina in a South African sample using cadaveric and osteological remains

Sacroiliac (SI) joint fixation is a technique used for SI joint fractures, SI joint dislocations and sacral fractures. Sacral screws can be placed either into the S1 or the S2 vertebrae if S1 is insufficient. Malpositioning of the screws is a common surgical complication as sacral variations exists amongst populations. Complications associated with the misposition of screws can lead to injury of the sacral venous plexus, iliac vessels, or sacral nerve roots. Therefore, this study aimed to evaluate sacral variations in a South African sample by determining distances between the first and second sacral foramina and classifying the common types of sacra found.A quantitative cross-sectional comparative study was conducted. One hundred and twenty (n = 120) dry human sacra and 11 formalin-fixed cadavers were measured to determine the linear distances between the first two anterior and posterior sacral foramina. Additionally, the dry human sacra were classified according to Mahato's classification system. A cadaver SI joint fixation simulation was performed by an orthopaedic surgeon.The mean sacral promontory height was found to be 31.81 mm and 37.52 mm in osteological and cadaver specimens, respectively. The mean anterior pedicle height was significantly different for the left (18.81 mm) and right (21.67 mm) side measurements. A statistically significant difference was found between cadavers and osteological samples for all measurements taken. In the osteological sample, ancestry and age mostly influenced the variations noted.Using Mahato's classification system, sacra with five sacral segments, auricular surfaces extending from the superior part of S1 to the middle of S3 and no accessory L5/S1 articulations had the highest prevalence of 59.17 %.The South African sample exhibited similarities but did not fully compare to other populations. The results in this study should be considered as a reference for surgeries involving the SI joint and sacral foramina. However, where possible, the exact anatomy with possible variations of the patient should be evaluated preoperatively using X-rays and angiograms.

2D and 3D microstructural analysis of the iliotibial tract.

The fascial system has gained recognition for its integral role in connecting skin, superficial and deep fasciae, and underlying muscles. However, consensus on its microstructure depending on its topography remains elusive as well as its implications in clinical practices, such as reconstructive surgery and physiotherapy techniques. This study focuses on the iliotibial tract (ITT) implicated in the iliotibial band syndrome. The goal is to describe microstructural characteristics using classical 2D histology and cryogenic contrast-enhanced microcomputed tomography (cryo-CECT) such as the total thickness, number of layers, layer thickness, fibre orientation and tortuosity, according to the specific topography. The total thickness of the ITT varied across topographic regions, with the superior part being on average thicker but non-significantly different from the other regions. The inferior part showed heterogeneity, with the anterior region (AI) being the thinnest and the posterior one (PI) the thickest. The ITT exhibited 1-3 layers, with no significant differences among regions. Most commonly, it consisted of two layers, except for the antero-superior (AS) and antero-middle (AM) regions, which sometimes had only one layer. The posterior regions frequently had 2 or 3 layers, with the PI region having the highest mean (2.7 layers). The intermediate layer was the thickest one, varying from the AI region (0.368 mm ± 0.114) to the PI region (0.640 mm ± 0.305). The superficial layer showed regional variability, with the AS region being the thinnest. The deep layer appeared thinner than the superficial one. Fibre orientation analysis indicated that the intermediate layer mainly consisted of oblique longitudinal fibres, orientated downward and forward, while the superficial and deep layers had transversal or oblique transversal fibres. Cryo-CECT 3D observations confirmed these findings, revealing distinct orientations for different layers. Fibre tortuosity exhibited differences based on orientation. Transversal fibres (>65°) were significantly less tortuous than longitudinal fibres (<25°) and oblique intermediate fibres (25°-65°), aligning with 3D plot observations. This quantitative study highlights various microstructural characteristics of the ITT, offering insights into its regional variations. The analysis accuracy is increased due to the novel technology of cryo-CECT which emerges as a valuable tool for precise assessment of 3D fibre orientation and tortuosity. These findings contribute to a deeper understanding of the ITT structure, useful in clinical practices, such as reconstructive surgery and physiotherapy, and future research endeavours.

The nociceptive inputs of the paraventricular hypothalamic nucleus in formalin stimulated mice

The paraventricular hypothalamic nucleus (PVH) is an important neuroendocrine center involved in pain regulation, but the nociceptive afferent routes for the nucleus are still unclear. We examined the profile of PVH receiving injurious information by a combination of retrograde tracing with Fluoro-Gold (FG) and FOS expression induced by formalin stimuli. The result showed that formalin injection induced significantly increased expression of FOS in the PVH, among which oxytocin containing neurons are one neuronal phenotype. Immunofluorescent staining of FG and FOS revealed that double labeled neurons were strikingly distributed in the area 2 of the cingulate cortex (Cg2), the lateral septal nucleus (LS), the periaqueductal gray (PAG), the posterior hypothalamic area (PH), and the lateral parabrachial nucleus (LPB). In the five regions, LPB had the biggest number and the highest ratio of FOS expression in FG labeled neurons, with main subnuclei distribution in the external, superior, dorsal, and central parts. Further immunofluorescent triple staining disclosed that about one third of FG and FOS double labeled neurons in the LPB were immunoreactive for calcitonin gene related peptide (CGRP). In conclusion, the present study demonstrates the nociceptive input profile of the PVH area under inflammatory pain and suggests that neurons in the LPB may play essential roles in transmitting noxious information to the PVH.

A Rare Case of Tentorial Sinus Thrombosis in a Patient with Sickle Cell Disease

Background: The reported incidence of venous thromboembolism in sickle cell disease patients is approximately 12% before the age of 40, accompanied by an additional 5-10% incidence of cerebral venous sinus thrombosis. Tentorial sinuses are venous structures in the posterior cranial fossa, draining the occipital and temporal lobes and the superior part of the cerebellum. Here, we describe a rare case of lateral tentorial sinus thrombosis in a patient with sickle cell disease. Methods: Case report and review of the available literature Results: A 26-year-old woman with sickle cell disease presented with a 2-day history of headache, nausea, and vomiting. Neurological exam was normal. CT brain revealed hyperdensity in the right occipital region and subtle area of hypodensity in the right medial occipital lobe. MRI/MRV brain showed right lateral tentorial sinus and occipitobasal vein thrombosis in addition to right medial occipital lobe venous infarct. The patient was started on therapeutic heparin initially, then transitioned to apixaban. Hemoglobin electrophoresis revealed a HbS fraction of 80.6% and HbF 16.6%. The patient received an exchange transfusion and was discharged home in stable condition. Conclusions: In patients with symptoms concerning for cerebral venous thrombosis, attention is usually directed to the traditional dural venous sinuses and cortical veins, while other venous structures can be overlooked. Although, in this particular case, it was clear on imaging, tentorial sinus thrombosis can easily be missed if not associated with brain edema or venous infarct.

Full SMAS: Endoscopic-Assisted Full Facial Rejuvenation.

Every region of the face may bear the signs of aging. Treating isolated areas without adequate anatomical knowledge can lead to incomplete or artificial-looking results and decrease patient satisfaction. Here, we describe a technique for complete rejuvenation, coined the "Full SMAS" technique, by addressing the anatomical continuity of the SMAS-Platysma to the deep-plane suspension of the face. This study aims to evaluate the contribution of endoscopic techniques combined with traditional facelift and neck lift procedures. The evaluation is conducted on procedures treating from the frontal and temporal regions of the superior part of the face to its mid and lower parts, including the cervical region. The treatment of the three sub-SMAS layers of the face was performed using endoscopy for repositioning the frontal region and midface. This procedure involves frontal and zygomatic-masseter ligament release, open treatment of the lower subplatysmal section, and the complete release of the retaining ligaments of the face and approach to the jowl. One hundred sixty-one patients underwent the Full SMAS technique, leading to long-lasting results, low complication rates, and high patient satisfaction. The Full SMAS is a systematic technique that provides complete facial rejuvenation by combining an endoscopic approach for the temporal and midface regions with traditional open approaches for the lower face and neck. Treating the temporal and midface regions using minimally invasive techniques (endoscopy) reduces the possibility of permanent nerve injuries, provides smaller scars, and creates more natural, long-lasting results.

Effect of Low-Intensity Transcranial Focused Ultrasound Stimulation in Patients With Major Depressive Disorder: A Randomized, Double-Blind, Sham-Controlled Clinical Trial.

Low-intensity transcranial focused ultrasound (tFUS) has emerged as a promising non-invasive brain stimulation modality with high spatial selectivity and the ability to reach deep brain areas. The present study aimed to investigate the safety and effectiveness of low-intensity tFUS in treating major depressive disorder. Participants were recruited in an outpatient clinic and randomly assigned to either the verum tFUS or sham stimulation group. The intervention group received six sessions of tFUS stimulation to the left dorsolateral prefrontal cortex over two weeks. Neuropsychological assessments were conducted before and after the sessions. Resting-state functional magnetic resonance imaging (rsfMRI) was also performed to evaluate changes in functional connectivity (FC). The primary outcome measure was the change in depressive symptoms, assessed with the Montgomery-Åsberg Depression Rating Scale (MADRS). The tFUS stimulation sessions were well tolerated without any undesirable side effects. The analysis revealed a significant main effect of session sequence on the MADRS scores and significant interactions between the session sequences and groups. The rsfMRI analysis showed a higher FC correlation between the right superior part of the subgenual anterior cingulate cortex (sgACC) and several other brain regions in the verum group compared with the sham group. Our results reveal that tFUS stimulation clinically improved MADRS scores with network-level modulation of a sgACC subregion. This randomized, sham-controlled clinical trial, the first study of its kind, demonstrated the safety and probable efficacy of tFUS stimulation for the treatment of depression.

Evaluation of cervical spinal cord atrophy using a modified SIENA approach

Spinal cord (SC) atrophy obtained from structural magnetic resonance imaging has gained relevance as an indicator of neurodegeneration in various neurological disorders. The common method to assess SC atrophy is by comparing numerical differences of the cross-sectional spinal cord area (CSA) between time points. However, this indirect approach leads to considerable variability in the obtained results. Studies showed that this limitation can be overcome by using a registration-based technique.The present study introduces the Structural Image Evaluation using Normalization of Atrophy on the Spinal Cord (SIENA-SC), which is an adapted version of the original SIENA method, designed to directly calculate the percentage of SC volume change over time from clinical brain MRI acquired with an extended field of view to cover the superior part of the cervical SC.In this work, we compared SIENA-SC with the Generalized Boundary Shift Integral (GBSI) and the CSA change. On a scan-rescan dataset, SIENA-SC was shown to have the lowest measurement error than the other two methods. When comparing a group of 190 Healthy Controls with a group of 65 Multiple Sclerosis patients, SIENA-SC provided significantly higher yearly rates of atrophy in patients than in controls and a lower sample size when measured for treatment effect sizes of 50%, 30% and 10%.Our findings indicate that SIENA-SC is a robust, reproducible, and sensitive approach for assessing longitudinal changes in spinal cord volume, providing neuroscientists with an accessible and automated tool able to reduce the need for manual intervention and minimize variability in measurements.

U shaped costal cartilage resection to reduce donor site morbidity

ObjectiveThe aim of our study is to reduce the complications of pain and chest wall deformity by modifying conventional costal cartilage graft harvesting. MethodIn this method while the superior part of the costal cartilage is removed completely, medial, lateral, and inferior parts are excised incompletely and used as a graft. Hence, continuity of the costal cartilage is maintained inferiorly. ResultsNineteen primary and 28 revision rhinoplasty patients were included in the study. There were no donor site complications in the early postoperative period or during one-year follow-up. ConclusionThe modified costal cartilage graft harvesting technique we described is a safe conservative surgical method.

Spatter transport in a laser powder-bed fusion build chamber

The adverse effects of spatter particles are well known in laser powder-bed fusion (LPBF) additive manufacturing. To prevent the deposition of spatter particles, an inert gas flow is commonly used to transport these spatters away from the build plate. However, the inert gas flow does not remove all spatters due to varying spatter sizes and ejection angles. Therefore, it is essential to understand and predict spatter trajectories to achieve superior LPBF parts. The present study focuses on numerical modelling of spatter trajectories in Renishaw AM250 using an Eulerian-Lagrangian discrete phase model. The argon velocity profile and spatter trajectories with and against the flow are computed for various materials, sizes and ejection angles. The simulation results are validated with experimental results and show a presence of uneven flow due to inlet geometry along with varying flow profiles across the build height due to inlet location. Spatter analysis shows three methods which result in spatter deposition. Spatter particles either fall directly on the build plate, are transported by the airflow or are re-directed in the recirculation zone. The findings presented in this work indicate the importance of build chamber design along with material-based parameter optimization that results in maximum spatter removal.

Anatomical analysis of the radial nerve and arcade of Frohse in the cubital fossa using human cadavers.

The radial nerve (RN) is a peripheral nerve that originates from the posterior bundle of the brachial plexus and carries C5-Th1 fibers. In the cubital fossa radial nerve divides into a superficial branch of the radial nerve (SBRN) and a deep branch of the radial nerve (DBRN). Next DBRN enters under the arcade of Frohse (AF) and changes its name to posterior interosseous nerve of antebrachii (PIN). The AF was first described in 1908 by Frohs and Frankel. It is the superior proximal part of the supinator muscle, which can be tendinous or membranous. Eight dissected upper limbs were examined to measure the distances and characteristics of the RN, DBRN, SBRN and AF, utilizing precise electronic caliper. The average distance from the point of branching of the RN into its terminal branches to the AF was 54.64 mm on average. In half of the cases DBRN divided before entering the AF. The average distance from the point of branching of the DBRN to the AF in these cases was 13.88 mm. The width of the AF averaged 8.60 mm. Five tendinous AF and three membranous AF were identified. A thorough understanding of the anatomy of the radial nerve and its branches in the cubital fossa, as well as the AF, is important for the development of anatomy and may also contribute to the reduction of surgical complications during procedures in this area.

Does the Extent of Tear Influence Pseudoparesis in Patients With Isolated Subscapularis Tears?

Surgeons tend to associate pseudoparesis with massive rotator cuff tears. However, little is known about the degree to which isolated subscapularis tears might be associated with pseudoparesis of the shoulder. Is the extent of subscapularis tears associated with pseudoparesis? A retrospective analysis identified all patients with subscapularis tears from 2010 to 2021 in the longitudinally maintained shoulder arthroscopy archive of one university hospital's shoulder section of the orthopaedic department. After exclusion, 106 of 152 patients with isolated subscapularis tears who underwent arthroscopic surgery were included in the study. Sixty percent of the patients were women, and the mean ± SD age was 52 ± 11 years. Patients who were scheduled for arthroscopic surgery were divided into two groups according to the presence or absence of pseudoparesis preoperatively. Pseudoparesis was considered to be active forward elevation > 45º but < 90º, which is a simple and reproducible measurement that can be taken using a goniometer, and demonstrated complete passive forward elevation. Pseudoparesis was present in 41% (43 of 106) of patients with an isolated subscapularis tear. Data on tear severity (according to Lafosse type, noted during arthroscopy), integrity of the subscapularis tendon (noted during arthroscopy), fatty degeneration (using the Goutallier grading system on MRI), arthroscopic findings of biceps disorder, superior labrum anterior to posterior (SLAP) lesions, and pain severity (measured by VAS score) were recorded. We used logistic regression analysis to examine the relationship between pseudoparesis and disruption of the tendinous part of the subscapularis. After accounting for potentially confounding factors such as biceps disorders and muscle atrophy, we found that pseudoparesis was associated with decreased tear severity according to the Lafosse classification (adjusted OR 0.2 [95% CI 0.1 to 0.7]; p = 0.01) and with disruption of the tendinous portion of the subscapularis (adjusted OR 21 [4 to 128]; p = 0.001). Patients with less severe tears (Lafosse type I) have lower odds of experiencing pseudoparesis compared with those with more severe tears (Lafosse types II, III, and IV), and patients with disruption of the tendinous portion of the subscapularis have substantially higher odds of pseudoparesis compared with those with an intact tendinous portion. No association was found between pseudoparesis and subscapularis fatty degeneration, biceps disorder, or SLAP lesions. This study provides initial evidence suggesting that isolated subscapularis tears are associated with pseudoparesis. The main finding of this study is that isolated subscapularis tears that involve the tendon extending to the inferior part of the subscapularis have higher odds of being found with pseudoparesis. These findings highlight the importance of maintaining the integrity of the superior tendinous part of the subscapularis for active forward elevation > 90°. Level III, therapeutic study.

Possible causes of vertigo attacks in Meniere’s disease

Various types of nystagmus during vertigo attacks in Meniere’s disease (MD) include direction-changing and non-direction-changing nystagmus. The direction-changing and non-direction-changing nystagmus may be associated with how the inner ear balance organs are influenced spatially and temporally. We hypothesized that the density difference inside the endolymph elicits the stereocilia inclination of the inner ear balance organs even if the density difference area does not directly touch the stereocilia. The direction of the nystagmus could change if the density difference area spreads around the inner ear balance organs. Numerous records of the nystagmus direction with new devices from the beginning of the nystagmus during the vertigo attacks will contribute to understanding how vertigo attacks appear in MD. The influence of the density difference may be associated with the degree of endolymphatic hydrops. Under significant endolymphatic hydrops, the volume effect due to the density difference becomes more prominent. The trabecular meshwork located in the perilymph in the superior part of the inner ear may maintain the perilymphatic space and prevent the enlargement of the endolymphatic space.

Specific pelvic shape in patients with developmental dysplasia of the hip on 3D morphometric homologous model analysis.

To clarify the morphological factors of the pelvis in patients with developmental dysplasia of the hip (DDH), three-dimensional (3D) pelvic morphology was analyzed using a template-fitting technique. Three-dimensional pelvic data of 50 patients with DDH (DDH group) and 3D pelvic data of 50 patients without obvious pelvic deformity (Normal group) were used. All patients were female. A template model was created by averaging the normal pelvises into a symmetrical and isotropic mesh. Next, 100 homologous models were generated by fitting the pelvic data of each group of patients to the template model. Principal component analysis was performed on the coordinates of each vertex (15,235 vertices) of the pelvic homologous model. In addition, a receiver-operating characteristic (ROC) curve was calculated from the sensitivity of DDH positivity for each principal component, and principal components for which the area under the curve was significantly large were extracted (p<0.05). Finally, which components of the pelvic morphology frequently seen in DDH patients are related to these extracted principal components was evaluated. The first, third, and sixth principal components showed significantly larger areas under the ROC curves. The morphology indicated by the first principal component was associated with a decrease in coxal inclination in both the coronal and horizontal planes. The third principal component was related to the sacral inclination in the sagittal plane. The sixth principal component was associated with narrowing of the superior part of the pelvis. The most important factor in the difference between normal and DDH pelvises was the change in the coxal angle in both the coronal and horizontal planes. That is, in the anterior and superior views, the normal pelvis is a triangle, whereas in DDH, it was more like a quadrilateral.

Bilateral effect of acupuncture on cerebrum and cerebellum in ischaemic stroke patients with hemiparesis: a randomised clinical and neuroimaging trial

BackgroundAcupuncture involving the limb region may be effective for stroke rehabilitation clinically, but the visualised and explanatory evidence is limited. Our objectives were to assess the specific effects of acupuncture...

Effect of adaptive control of cooling rate on microstructure and mechanical properties of laser additively manufactured Inconel 718 thin walls

Ni-alloy Inconel 718 (IN718) is finding ever-increasing applications in various industries like aviation and aerospace. IN718 is a precipitation-strengthened alloy which derives its strength mainly from the intermetallic phases, γ” (Ni3Nb) along with the γ’ (Ni3(Al, Ti)) phase which can be precipitated using standard heat treatment schedules. However, the consummation of Nb in Laves phase formation during solidification tends to deteriorate the strength of the material. During laser additive manufacturing (LAM) by directed energy deposition (DED), the cooling rate variation along the build direction causes variations in the microstructure, properties and Laves phase distribution. The study aims to minimize the heterogeneities along the build direction by monitoring and controlling the cooling rate during DED of IN718. The feedback control system involves the use of two pyrometers in tandem with a leading pyrometer measuring the molten pool temperature and a trailing pyrometer measuring the temperature at a distance behind the molten pool. Two sets of thin walls of 120 layers were fabricated with one set being of constant process parameters without feedback control and the other set being of adaptive-controlled process parameters. The adaptive control was aimed at maintaining the cooling rates above a desired limit by changing the process parameters, namely the laser scan speed and the powder feed rate. The Laves phase morphology, which affects the strength of the deposited part deleteriously was finer and more discrete in the adaptive-controlled walls which led to their easier dissolution during heat treatment. This in turn helped in the precipitation of more amount of strengthening phases during heat treatment which led to better mechanical properties. The characterizations of the two sets of walls reflected the superior part quality of the adaptive-controlled wall in terms of homogeneity of microstructure, enhanced microhardness and tensile strength, thereby validating the importance of adaptive control of cooling rate in ensuring better quality in LAM parts.

Radiofrequency catheter ablation for redo procedures after pulmonary vein isolation with the cryoballoon technique: 9-year outcome

Abstract Catheter ablation has become the first line of therapy in patients with symptomatic, recurrent, drug-refractory atrial fibrillation. Cryoablation has been shown to be a safe and effective technique for pulmonary vein isolation. However, there is a significant arrhythmia recurrence rate after cryoablation procedures and there are no established strategies for redo procedures in these patients. Therefore, we have summarized our experience with radiofrequency catheter ablation for redo procedures after pulmonary vein isolation with the cryoballoon technique (including an analysis of pulmonary vein conduction recovery patterns after procedures performed with the first or second generation cryoballoon). Methods Two hundred and twenty patients (paroxysmal AF: 140 patients, persistent AF: 80 patients) had to undergo a redo procedure after initially successful circumferential PV isolation with the cryoballoon technique (First generation: 110 patients (group A); second generation: 110 patients (group B)). The redo ablation procedures were performed using a segmental approach or a circumferential ablation strategy (three-dimensional mapping system) depending on the intra-procedural findings. Results During the redo procedure, a mean number of 1.6 re-conducting PVs were detected (using a circular mapping catheter; group A: 2.2 re-conducting PVs, group B: 1.0 re-conducting PVs). There was a slightly higher incidence of chronic PV reconnections related to the left-sided PV ostia than to the right-sided PVs in both groups. Furthermore, sites of chronic PV reconnection were found more frequently in the inferior parts of the PV ostia than in the superior parts. In 97 patients in group A, a segmental approach was sufficient to eliminate the residual PV conduction because there were only a few recovered PV fibers (1-3 reconnected PVs; group A1). In the remaining 13 patients in group A, a circumferential ablation strategy was used because of a complete recovery of the PV-LA conduction of all four pulmonary veins (group A2). In group B, a segmental approach was sufficient in nearly all patients (109/110) because there was only a minor reconnection of 1-2 PVs. All recovered PVs could be isolated sucessfully again. At 108-month follow-up, 69.1 % of all patients were free from an arrhythmia recurrence (152/220 patients; group A: 72/110 patients (65.5 %), group B: 80/110 patients (72.3 %)). There were no major complications in both groups. Conclusions In patients with an initial circumferential PVI using the cryoballoon technique, a repeat ablation procedure can be performed safely and effectively using radiofrequency catheter ablation. In most cases only a few re-conducting PV fibers were found and therefore, a segmental re-ablation approach seems to be sufficient in the majority of patients (especially in patients treated with the second generation cryoballoon).