Mean Migration Distance Research Articles

Analysis of clinical and radiographic outcomes at least 5 years after coronectomy for deeply impacted mandibular third molars

ObjectiveCoronectomy is an alternative to traditional mandibular third molar extraction when the inferior alveolar nerve (IAN) is closely associated with the roots of these molars. Given the paucity of research on the long-term outcomes after coronectomy, we conducted this study to evaluate clinical and radiographic outcomes at least 5 years post-coronectomy. MethodsThis retrospective study enrolled all patients with impacted mandibular third molars treated with coronectomy at our institution who were willing to return for follow-up evaluation 5 years or more after their original procedure. Patient data were obtained retrospectively from hospital records and during oral examinations at the follow-up study appointment. We assessed the following postoperative clinical outcomes: injury to the IAN, root migration distance, root exposure in the oral cavity, non-healing sockets, pain or sensitivity in the coronectomy area, and the presence of periapical pathology. ResultsOf the 196 patients invited to participate, 66 patients (male, 32%; female, 68%) who underwent a total of 75 coronectomies were included in this study. No persistent hypoesthesia of the lower lip were reported during follow-up. Two patients required reoperation because of root eruption into the oral cavity. Approximately two-thirds of residual roots migrated from their position on preoperative radiographs; the mean migration distance was 3.2 ± 1.3 mm. Two patients (2.6%) had pain in the soft tissues around the coronectomy site. ConclusionOur findings confirm that coronectomy is an effective treatment option for preventing IAN injury when the nerve is in close proximity to the roots of these molars.

Migratory Ecology of Pseudoplatystoma fasciatum in the Amazon Basin Revealed by Otolith Microchemistry

Fish migrate for varied reasons, including to avoid predators and to access feeding, spawning, and nursery habitats, behaviors that enhance their survival and reproductive rates. However, the migratory ecology of many important fishes, especially those in river–floodplain ecosystems, remains poorly understood. One fish of the Amazon Basin whose migratory behavior is poorly understood is the catfish Pseudoplatystoma fasciatum. Here, we used otolith elemental microchemistry to characterize the migration ecology of P. fasciatum in the Amazon Basin. The main research questions of this study were: (1) does P. fasciatum move between waters with different Sr isotopic signatures (87Sr/86Sr) and chemical compositions? (2) What distance do they migrate? (3) Is the migration of P. fasciatum related to age? And (4) does P. fasciatum migrate mainly upstream, downstream, or in both directions? We assessed whether P. fasciatum migrates between waters with different 87Sr/86Sr values, comparing the Sr isotopic signature of otolith transects of each individual with the range of Sr isotopic signatures within the respective rivers. We found that 34% of the 71 fish analyzed migrated between rivers with different Sr isotopic signatures and 66% did not. The mean migration distance migrated was 126 km, with most specimens migrating between 72 and 237 km. Apparently, no fish of age one or age six or older migrated. All fish that migrated were between two and five years of age, with 20% of the specimens that migrated being two years old, 40% three years old, 30% four years old, and 20% five years old. Sixty-six percent of all individuals that migrated between rivers with different Sr signatures did so bidirectionally, while 33% moved unidirectionally. According to our definition of homing behavior in which fish migrated back to the same river where they were born, 41% of all fish that migrated displayed apparent homing behavior. Our findings provide insights into the migratory ecology of P. fasciatum, corroborating and refining knowledge reported in the literature. Our results on the migratory ecology of P. fasciatum have implications for sustainable fisheries conservation and management: conserving P. fasciatum requires habitat maintenance and suitable fishing practices in spawning and nursery habitats, and managers must consider large geographic areas for effective fishery management and conservation.

Modelling the spread of cystic fibrosis in Brittany using genealogical data over five centuries

BackgroundThe French region of Brittany presents one of the highest cystic fibrosis (CF)-causing allele frequency in Europe. Here, we tested two hypotheses: i) CF-causing allele carriers arrived by sea in the middle of the 1st millennium AD, and ii) a selective advantage for healthy carriers explains this high rate. MethodsFrom the census of cystic fibrosis patients, frequency maps of the most widespread alleles were established. A mathematical model was developed, based on birth date and place of the ancestors of these patients over 5 centuries, to determine the distribution of local migrations and their parameters for inter-generational intervals of 32 years. This model was applied to simulate the spread of CF-causing variant carriers, according to different scenarios that corresponded to the immigration of a given number of variant carriers at different times (year) and places, and to compare their results to current frequency maps. ResultsMigrants carrying a CFTR variant settled in several locations, around which they spread, notably in Central Brittany (F508del variant), Léon (G551D variant) and Cornouaille (1078delT variant). Until the end of the 18th century, the spreading of disease-causing allele carriers was relatively slow, and allele frequencies progressively increased. Then, the mean migration distances increased rapidly, leading to a decline in local frequencies. ConclusionsThe main CFTR variants could only have reached their current frequencies through a selective advantage for healthy carriers of the order of 4–6 % at each generation. For the most widespread variant (F508del), the model supports the hypothesis that it appeared around 190 generations ago.

Adjacent tooth migration after maxillary first molar loss in patients with sinus augmentation: A retrospective research.

The objectives of this study are to: (1) investigate the extent of antagonistic and distal neighboring tooth migration in the maxillary posterior single tooth-missing site during the healing period of bone augmentation and implant surgery; (2) identify factors associated with tooth migration. One hundred and forty-three cases that lost the maxillary first molar were included, and their CBCT data during the edentulous period were obtained. Dentition models were reconstructed from CBCT, and superimpositions were performed, followed by measuring migration distances and calculating migration rates of antagonistic and distal neighboring teeth. Factors were analyzed using multivariate generalized estimating equations (GEE). The mean migration distances were 208 ± 137 μm and 403 ± 605 μm for antagonistic teeth and distal teeth, and the mean migration rates were 26.8 ± 21.2 μm/month and 48.5 ± 76.7 μm/month, respectively. One hundred and nineteen out of 143 distal neighboring teeth migrated toward the edentulous site, and all antagonistic teeth migrated occlusally. Occlusal contact loss and chronic apical periodontitis both significantly accelerated antagonistic tooth migration (p < 0.05), the latter also accelerated distal tooth migration (p < 0.05). Besides, the displacement of the distal teeth was somewhat accelerated by the impacted adjacent third molar and root protrusion into the sinus. The neighboring teeth tend to migrate toward the edentulous gap in the maxillary posterior region. Occlusal contact loss and chronic apical periodontitis are two significant risk factors for accelerating antagonistic tooth migration, and for distal teeth, chronic apical periodontitis is the risk factor. The impacted adjacent third molar and root protrusion into the sinus are also potential risk factors for accelerating the migration of the maxillary distal tooth. Thus, to prevent maxillary edentulous gap reduction, the factors mentioned above should be taken into consideration when planning treatment flow.

Radiographic lead migration in percutaneous spinal cord stimulator trials

IntroductionLead migration during spinal cord stimulator (SCS) trials is relatively neglected in the literature and presents a different set of challenges compared with fully implanted leads. There is no consensus...

Temporal sampling and network analysis reveal rapid population turnover and dynamic migration pattern in overwintering regions of a cosmopolitan pest.

Genetic makeup of insect pest is informative for source-sink dynamics, spreading of insecticide resistant genes, and effective management. However, collecting samples from field populations without considering temporal resolution and calculating parameters related to historical gene flow may not capture contemporary genetic pattern and metapopulation dynamics of highly dispersive pests. Plutella xylostella (L.), the most widely distributed Lepidopteran pest that developed resistance to almost all current insecticides, migrates heterogeneously across space and time. To investigate its real-time genetic pattern and dynamics, we executed four samplings over two consecutive years across Southern China and Southeast Asia, and constructed population network based on contemporary gene flow. Across 48 populations, genetic structure analysis identified two differentiated insect swarms, of which the one with higher genetic variation was replaced by the other over time. We further inferred gene flow by estimation of kinship relationship and constructed migration network in each sampling time. Interestingly, we found mean migration distance at around 1,000 km. Such distance might have contributed to the formation of step-stone migration and migration circuit over large geographical scale. Probing network clustering across sampling times, we found a dynamic P. xylostella metapopulation with more active migration in spring than in winter, and identified a consistent pattern that some regions are sources (e.g., Yunnan in China, Myanmar and Vietnam) while several others are sinks (e.g., Guangdong and Fujian in China) over 2 years. Rapid turnover of insect swarms and highly dynamic metapopulation highlight the importance of temporal sampling and network analysis in investigation of source-sink relationships and thus effective pest management of P. xylostella, and other highly dispersive insect pests.

Incidence and Risk Factors for Spinal Cord Stimulator Lead Migration With or Without Loss of Efficacy: A Retrospective Review of 91 Consecutive Thoracic Lead Implants

ObjectiveLead migration after spinal cord stimulator (SCS) implant is a commonly reported complication and the most common reason for revision surgery in cases of loss of efficacy. The primary aims of this study are to describe the incidence and degree of lead migration in the subacute postoperative period after SCS implant and to report potential risk factors for lead migration. Materials and MethodsWe performed a retrospective chart review of all patients at a single academic center who received an SCS implant from January 1, 2020, to December 31, 2020. Information on patient (age, sex, weight, and height) and operative factors (device manufacturer, epidural access level and method, and implantable pulse generator location) were extracted from medical records. Intraoperative imaging was compared to subacute follow-up imaging obtained less than 20 days postimplant to measure lead migration distance. Regression models were fitted to determine associations between lead migration distance and potential clinical risk factors. ResultsA total of 91 cases (182 leads) were included in the study. Within 20 days of implantation, 88.5% of leads had migrated (86.3% caudal and 2.2% cephalad). Mean migration distance for leads with caudal migration only was 12.34 ± 12.19 mm based on anteroposterior radiographs and 16.95 ± 15.68 mm on lateral radiographs. There was an association of greater caudal lead migration as patient body mass index increased (β-coefficient 0.07 [95% confidence interval 0.01–0.13], p = 0.031). Within the entire cohort, one patient (1.1%) required lead revision for loss of efficacy. ConclusionsIn the subacute postoperative period after SCS implant, the majority of SCS leads migrated caudally with an average of two lead contacts. Knowledge of this expected migration and risk factors can better inform implanting physicians intraoperatively when deciding final lead placement location. The finding of high likelihood of caudal lead migration in the subacute postoperative period brings the need for a well-designed prospective study to the forefront of our field. This will allow implanting providers to make well-informed decisions for intraoperative lead placement.

Assessing migration strategies and cause specific mortality of adult female White-tailed Deer (&lt;i&gt;Odocoileus virginianus&lt;/i&gt;) in North Dakota, USA

Life-history characteristics of White-tailed Deer (Odocoileus virginianus) have been documented in areas of the Northern Great Plains, but limited information is available in grassland dominated regions. We documented migration strategy, home range use, and survival of adult female White-tailed Deer in central North Dakota. We monitored 62 radio-collared adult (&gt;1.5 year-old) female White-tailed Deer from February 2010 to December 2012. We documented 86 summer home ranges and classified deer as resident, migratory, or exhibiting a late season movement. Mean migration distance between non-overlapping summer and winter home ranges was 11.76 km (SE 0.86, n = 21). Mean late season movements were 20.69 km (SE 2.94, n = 7) and were likely the result of deer exhausting food resources throughout winter. We also developed five competing models that represented variation in survival among time periods (e.g., pre-hunt, hunt, and post-hunt in 2010 and 2011). Our top model indicated that survival (S) was similar between hunt 2010 and post-hunt 2011 periods but was lower (S = 0.82; SE 0.04, 95% CI 0.73–0.89) than the remaining time periods (S = 0.97; SE 0.01, 95% CI 0.93–0.99). Our results suggest that deer migration strategies and survival are likely influenced by a combination of winter severity and food availability. Mortalities attributed to hunter harvest were low during our study, which may indicate that increased recreational opportunities could be made available, even after severe winters.

Differing migration patterns and year-round habitat-use of allopatric nesting Eastern Tundra Bean Geese (Anser fabalis serrirostris) in East Asia

Sympatric Chinese-wintering Eastern Tundra Bean Geese (Anser fabalis serrirostris, ETBG) breed in two widely separated Arctic areas (Central Russian Arctic and Anadyr region); South Korean-wintering birds (Chaun-South Korea) breed in a third discrete area between these two. Such winter/summer segregation likely structures the population, potentially resulting in distinct migration patterns and habitat-use throughout the annual cycle. We tracked individuals using GPS-GSM transmitters from all three of these geographically discrete ETBG subpopulations to see whether this was the case, testing for differences in migration patterns, seasonal and diurnal habitat-use using remotely sensed land-cover mapping. Mean migration distance of Central Arctic-China and Chaun-South Korea individuals did not differ significantly, but Anadyr-China birds travelled 15–24% further (mean: 1140 ​km, P ​< ​0.001). Despite this, mean spring migration durations were longest among Central Arctic-China ETBG, significantly longer than Anadyr-China geese, due to significantly longer stopovers, which were significantly longer than Chaun-South Korea birds. Autumn migration duration of Central Arctic-China and Chaun-South Korea individuals was significantly shorter than in spring, with fewer, shorter stopovers. Lack of significant differences in migration and stopover duration or numbers of stopovers between spring and autumn among Anadyr-China ETBG confirms this is a plastic trait, differing between subpopulations responding to prevailing conditions. Migration patterns and habitat-use differed significantly between all three ETBG subpopulations, although all tended to use wetlands more at night and croplands more in daytime in winter, suggesting specific adaptations and responses to differing conditions encountered along their different migration routes. Although untestable, we speculate that differences in habitat-use may affect fitness levels and genetic exchange between subpopulations, but based on our observations, conclude clear differences in migration and foraging ecology between these elements of the same subspecies, even in winter sympatry.

Preoperative evaluation of pleural adhesion in patients with lung tumors using four-dimensional computed tomography performed during natural breathing.

The presence of pleural adhesions increases blood loss, occurrence of pulmonary fistulation due to lung injury, and operative time and may complicate thoracoscopic surgery. Recently, it has been reported that four-dimensional computed tomography (4D-CT) synchronized with breathing predicts pleural adhesion. These studies have been performed by asking the patients to maintain a constant respiratory rhythm at the time of scanning. However, many patients face difficulty in doing so, particularly elderly individuals and patients with respiratory dysfunction. We examined the utility of 4D-CT performed while maintaining a natural breathing pattern, which reduces patient burden, in detecting pleural adhesions.A total of 36 patients with a lung tumor near the pleura underwent 4D-CT during free breathing. The migration distance between the lesion and the nearest point on the chest wall on 4D-CT was measured. A sufficient distance indicated the absence of adhesion in that area. The presence of actual adhesions was evaluated and confirmed by intraoperative thoracoscopic findings.There were 7 cases determined to have adhesion by 4D-CT, and 4 of them had actual adhesions confirmed during surgery. The sensitivity and specificity were 80.0% and 90.3%, respectively. The mean migration distance of tumors was 0.8 ± 0.2 cm in the 5 cases with adhesion and 2.6 ± 1.8 cm in the 31 cases without adhesion (P = .01).These results suggest that 4D-CT is a convenient and useful technique for the preoperative assessment of pleural adhesion.

Staphylococcusaureus protein A as a means of assessing sperm penetrability in cervical mucus in vitro.

Objective The effectiveness of Staphylococcus protein A (SPA) in improving the penetration ability of sperm and reducing antisperm antibody (ASA) titers in immunologically infertile males was evaluated.Methods Seminal fluid samples were obtained from 15 infertile men, and ASA titers were assessed with the latex agglutination test. Identification of immunoglobulin (Ig) classes and characterization of the antigens involved in the immune response were performed using indirect immunofluorescence. Local ASAs typically present as a mixture of IgG and IgA classes. The capillary tube penetration method was used to assess the capability of spermatozoa to penetrate the cervical mucus (CM).Results ASAs associated with the neck region of sperm showed a significantly lower migration distance in the CM of infertile females than ASAs associated with the head or tail segments. ASA-positive seminal fluid exhibited significant increases in the mean migration distance (2.6 ± 1.4 cm vs. 1.54 ± 1.1 cm, respectively; p< 0.001) and sperm concentration (174 ± 121.0 × 10³/mL vs. 101 ± 93.7 × 10³/mL, respectively; p= 0.033) after treatment with SPA compared to pre-treated samples. A significant reduction (p< 0.01) in the recorded ASA titer was detected.Conclusion These results indicate that SPA can be used as a sorting regimen for insemination programs. However, further studies are warranted to assess its influence on pregnancy rate.

The chemotactic properties of various topical brimonidine tartrate ophthalmic preparations

BackgroundThe study aimed to evaluate and compare the leukocyte chemotactic activities of various brimonidine tartrate (BT) eye drop formulations.MethodsA 96-well dot-blot platet using a Boyden-style well was used to study the chemotactic effects of BT ophthalmic preparations. A modification was made to create blind wells where the tested agents were placed. Leukocytes were isolated from the peripheral blood of healthy volunteers. As positive controls, we used diluted drugs, benzalkonium chloride solution (BAK), zymosan-activated serum, and formyl-methionine-leucine-phenylalanine peptides. The negative control in our study was a phosphate-buffered saline solution. For each experimental condition, we measured leukocyte migration through a Millipore membrane. The differences in the mean migration distance between groups were compared using the analysis of variance (ANOVA).ResultsThe measured migration distances (in μm ± SD) were 62.14 ± 3.71 for BT 0.2% with BAK (Alcon Laboratories Inc.); 63.61 ± 3.81 for BT 0.2% with BAK (Allergan Inc); 40.36 ± 3.17 for BT 0.15% without BAK; and 41.02 ± 2.17 for BAK alone. The negative controls showed no chemotactic activity, while the positive controls showed the highest neutrophil migration of all experimental conditions. The differences between BT 0.15% without BAK and the other commercial formulations were statistically significant.ConclusionCommercial ophthalmic preparations of BT 0.2% with BAK 0.005% had higher chemotactic properties than the alternative of a lower concentration of BT and without the preservative BAK. Therefore, the latter should be considered for patients with glaucoma or ocular hypertension in order to minimize iatrogenic ocular inflammation.

Retrospective assessment of a single fiducial marker tracking regimen with robotic stereotactic body radiation therapy for liver tumours

To investigate tumour motion tracking uncertainties in the CyberKnife Synchrony system with single fiducial marker in liver tumours. In the fiducial-based CyberKnife real-time tumour motion tracking system, multiple fiducial markers are generally used to enable translation and rotation corrections during tracking. However, sometimes a single fiducial marker is employed when rotation corrections are not estimated during treatment. Data were analysed for 32 patients with liver tumours where one fiducial marker was implanted. Four-dimensional computed tomography (CT) scans were performed to determine the internal target volume (ITV). Before the first treatment fraction, the CT scans were repeated and the marker migration was determined. Log files generated by the Synchrony system were obtained after each treatment and the correlation model errors were calculated. Intra-fractional spine rotations were examined on the spine alignment images before and after each treatment. The mean (standard deviation) ITV margin was 4.1 (2.3)mm, which correlated weakly with the distance between the fiducial marker and the tumour. The mean migration distance of the marker was 1.5 (0.7)mm. The overall mean correlation model error was 1.03 (0.37)mm in the radial direction. The overall mean spine rotations were 0.27° (0.31), 0.25° (0.22), and 0.23° (0.26) for roll, pitch, and yaw, respectively. The treatment time was moderately associated with the correlation model errors and weakly related to spine rotation in the roll and yaw planes. More caution and an additional safety margins are required when tracking a single fiducial marker.

Analysis of the Basic Characteristics of Osteogenic and Chondrogenic Cell Lines Important for Tissue Engineering Implants.

We isolated and characterized cultures of bone and cartilage tissue cells of laboratory minipigs. The size and morphological features of adherent osteogenic and chondrogenic cells were specified. During long-term culturing under standard conditions, the studied cultures expressed specific markers that were detected by immunohistochemical staining: alkaline phosphatase and calcium deposits in osteoblasts and type II collagen and cartilage extracellular matrix in chondrogenic cells. Proliferative potential (mitotic index) of both cell types was 4.64% of the total cell number. Cell motility, i.e. the mean velocity of cell motion was 49 pixels/h for osteoblasts and 47 pixels/h for chondroblasts; the mean migration distance was 2045 and 2118 pixels for chondroblasts and osteoblasts, respectively. The obtained cell lines are now used as the control for evaluation of optimal biocompatibility of scaffold materials in various models. Characteristics of the motility of the bone and cartilage tissue cells can be used for modeling and estimation of the rate of cells population of 3D scaffolds made of synthetic and biological polymers with different internal structure and physicochemical properties during designing in vitro tissue implants.

Anterior discectomy could still be an alternative to corpectomy in highly migrated cervical disc herniation

Objective: For cases of cervical disc herniation, highly migrated cervical disc (HMCD) is clinically rare and usually treated with anterior cervical corpectomy and fusion (ACCF). This study aims to analyze the feasibility of anterior cervical discectomy and fusion (ACDF) for the patients with HMCD.Method: Clinical data of 32 patients with HMCD treated with ACDF or ACCF were retrospectively reviewed. Migration distances of the disc prolapses were measured. The mJOA score was used to evaluate surgical effect.Results: ACDF was successful in 27 patients while ACCF was used for the remaining 5 because of epidural disc prolapse adhesion or unreachable migrated fragments. Complete spinal cord decompression without residual disc fragments was observed in postoperative MRI of all cases. The mean migration distance of the disc prolapses in ACDF group was 7.3 mm, comparing to 11.4 mm in ACCF group. No disc prolapse in ACDF group exceeded the axial length of the vertebral bodies while three of five in ACCF group did. Preoperative mean mJOA scores in ACDF group and ACCF group were 8.20 ± 2.75 and 6.10 ± 2.15, respectively. Postoperative mean mJOA scores in those two groups were significantly improved to 14.70 ± 1.55 (p < .001) and 12.80 ± 1.72 (p < .001), with an improvement rate of 72.80 ± 4.76% and 62.90 ± 9.46%, respectively.Conclusion: ACDF is feasible for patients with HMCD except for cases of epidural disc prolapse adhesion or huge disc prolapse which migrates over the axial length of the vertebral body. Clinical symptoms can be significantly improved with few serious complications in those patients including ones underwent alternative ACCF due to a failed ACDF.

Challenges in developing a reseeded, tissue-engineered aortic valve prosthesis

Biological heart valve prostheses are characterized by a limited durability due to the degenerative processes after implantation. Tissue engineering may provide new approaches in the development of optimized valvular grafts. While re-endothelialization of decellularized heart valves has already been successfully implemented, interstitial repopulation still remains an unaccomplished objective although it is essential for valvular functionality and regeneration potential. The aim of this study was to compare different concepts for an improved in vitro interstitial repopulation of decellularized heart valves. A novel 3D heart valve model has been developed to investigate the cell behaviour of valvular interstitial cells (VIC) in their physiological environment and to evaluate the potential of in vitro repopulation of acellular heart valves. Ovine aortic heart valves were decellularized by detergent solutions and additionally treated with trypsin or laser perforation. Subsequently, the decellularized extracellular matrices (dECM) were reseeded with ovine VIC using reseeding devices to provide a repopulation of the matrix on a defined area under controlled conditions. After an initial attachment of the VIC, reseeded dECM were transferred into a transwell system to improve the nutrient supply inside the valvular matrix. Cell migration and expression of cell markers were analysed histologically. The results were compared with VIC cultivation in a biological scaffold. VIC did not migrate into the matrix of untreated dECM and reseeding in laser perforated dECM showed inconsistent results. However, trypsinization increased the susceptibility of the valvular cusps to VIC penetration and repopulation of superficial areas. Additionally, the cultivation of reseeded dECM in a transwell system significantly increased the total number of cells repopulating the valvular matrix and their mean migration distance, representing the best repopulation results. Immunohistological analysis and in situ zymography revealed a low activation status of repopulating VIC after 7 days of culture. A comparison of different techniques for increasing interstitial repopulation of detergent dECM revealed that an additional limited trypsin treatment was most effective. Nevertheless, a complete interstitial repopulation of decellularized heart valves remains a challenging endeavour. Additional experimental fine-tuning may improve the in vitro results of heart valve tissue engineering.

Internal migration around the world: comparing distance travelled and its frictional effect

This paper examines how internal migration distance and its frictional effect vary between countries. Such comparisons are hampered by differences in the number and configuration of spatial units for which data are available − the modifiable area unit problem (MAUP). We use the flexible aggregation routines embedded in the IMAGE Studio, a bespoke software platform which incorporates a spatial interaction model, to elucidate these scale and pattern effects in a set of countries for which finely grained origin-destination matrices are available. We model the relationship between mean migration distance and mean area size and we show that the frictional effect of distance remains remarkably stable across spatial scale, except where zones have small populations and are poorly connected. This stability allows robust comparisons between countries even though zonal systems differ. We find that mean migration distances vary widely, being highest in large, low-density countries and positively associated with urbanisation, HDI and GDP per capita. This suggests a positive link between development and migration distance, paralleling that between development and migration intensity. We find less variation in the beta parameter that measures distance friction but identify clear spatial divisions between more developed countries, with lower friction in larger, less dense countries undergoing rapid population growth.

A 'through-and-through bowing technique' for antegrade thoracic endovascular aneurysm repair with total arch debranching: a technical note and the initial results.

The aim of this study was to evaluate the deployment accuracy of a new 'through-and-through bowing technique' that involves the deployment of the stent graft with total arch debranching via median sternotomy. The migration distance, patients' demographic characteristics, operative values and the postoperative complications were examined retrospectively. From November 2012 to February 2013, 5 patients with an aortic arch aneurysm underwent total debranching and antegrade thoracic endovascular aneurysm repair (TEVAR) (control group). Fifteen patients underwent placement using the 'through-and-through bowing technique' (bowing group) from March to November 2013. The device was deployed as follows. A stiff guide wire was passed through the debranching prosthesis via the femoral artery. By pushing the bilateral ends of the wire against the aortic arch, the device was located along the greater curvature and bent like a bow. The migration distance, defined as the distance between the pre- and post-deployment positions of the distal end of the stent graft, was measured using fluoroscopic images. There were no significant differences with respect to the patients' demographics or the operative variables between the two groups. The mean migration distance in the control group (9.4 ± 8.7 mm) was significantly longer than that in the bowing group (1.3 ± 1.5 mm). Although one major stroke occurred in the bowing group, there was no operative mortality in either group. The present paper demonstrated the precise positioning of a GORE TAG deployment using a 'through-and-through bowing technique' with total arch debranching.

Gradual spinal cord decompression through migration of floated plaques after anterior decompression via a posterolateral approach for OPLL in the thoracic spine.

Several surgical procedures have been developed to treat thoracic OPLL (ossification of the posterior longitudinal ligament). However, favorable surgical results are not always achieved, and consistent protocols and procedures for surgical treatment of OPLL in this region have not been established. Beak-type OPLL in the thoracic spine is known to be the most complicated form of OPLL to treat surgically. In this study, the authors examine the clinical outcomes after anterior decompression via a posterolateral approach for beak-type OPLL in the thoracic spine and address the gradual spinal cord decompression caused by migration of the floated plaques after surgery. Between 2011 and 2013, a total of 12 patients with thoracic myelopathy due to OPLL were surgically treated at the authors' institute. The study group for this paper comprises 6 of those 12 patients. These 6 patients, who had beak-type OPLL, underwent with anterior decompression and instrumented fusion via the authors' posterolateral approach-based surgical technique. The other 6 patients, who exhibited other types of OPLL, underwent posterior decompression and instrumented fusion. In the study group (the 6 patients with beak-type OPLL), half of the patients (the 3 patients who were treated first) were treated with removal of the ossified ligament. These patients are referred to as the removal group. The other 3 patients were treated by means of "floating" the OPLL plaques and are referred to as the floating group. Clinical and radiographic outcomes were evaluated in these 6 cases. The recovery rates were 52.4% in the removal group and 60.0% in the floating group. Two patients in the removal group had operative complications, including a dural tear and temporary neurological deterioration. No operative complications were encountered in the floating group. In all 3 cases in the floating group, floating of the ossified ligament was completely achieved, and the floated plaque gradually migrated into the ventral bone resection areas. The mean migration distances of the floated plaque were 2.4 mm, 4.3 mm, 4.7 mm, and 4.8 mm at 1, 3, 6, and 12 months after surgery. Treatment of beak-type OPLL in the thoracic spine via the posterolateral approach-based floating plaque technique was safe and effective in this small case series. Gradual migration of the floated plaques provided additional spinal cord decompression during the postoperative course.

Radiological evaluation of anterior lumbar fusion using PEEK cages with adjacent vertebral autograft in spinal deformity long fusion surgeries.

The aim of this study was to evaluate the radiographic characteristics of polyetheretherketone (PEEK) cages packed with adjacent vertebral autograft material in lumbar anterior lumbar interbody fusion (ALIF) in spinal deformity long fusion surgeries. This is a retrospective radiographic study. From April 2008 to April 2012, 40 patients (5 males and 35 females, mean age 67 ± 9 years) with coronal and/or sagittal spine deformities underwent staged corrective surgery combined with lumbar ALIF using PEEK cages at the L3-L4, L4-L5 or L5-S1 segment with posterior long (≥ 4 levels) instrumentation. The mean follow-up time was 27.5 months (13-49 months). We examined the interbody fusion rate and cage subsidence at 3 months postoperatively and final follow-up. Additionally, we evaluated the distance of cage migration at final follow-up and the improvement in lumbar lordosis. The rate of "collapse" of the adjacent vertebra where the autograft was harvested was assessed at the final follow-up. Finally, we examined the cage-related postoperative complications in this series. Solid interbody fusion was achieved in 96.4 % (81/84) of the levels at the final follow-up. A mild forward cage migration was observed, and the mean migration distance at final follow-up was 0.83 mm in L3/4, 0.36 mm in L4/5 and 0.55 mm in L5/S1. There was cage subsidence observed in 8.3 % (7/84) of the levels. In all patients, the PEEK cage maintained a significant increase in segmental lordosis at all postoperative visits. However, a mild reduction in segmental lordosis still occurred with time. The adjacent lumbar vertebral bodies where the autografts were harvested appeared to be intact in height radiologically at the final follow-up. There were no postoperative complications due to bone harvesting or cage insertion. Proximal junctional kyphosis was found in one patient who underwent a subsequent revision surgery. The use of lumbar ALIF with PEEK cages and adjacent vertebral autografts in spinal deformity long fusion surgeries is an effective and safe procedure. The allograft filler is safe and effective in maintaining the shape of harvested vertebrae. Additional long-term follow-up studies are needed to further justify its use.