Higher Angulation Research Articles

Computational Comparison of the Mechanical Behavior of Aortic Stent-Grafts Derived from Auxetic Unit Cells

PurposeInappropriate stent-graft (SG) flexibility has been frequently associated with endovascular aortic repair (EVAR) complications such as endoleaks, kinks, and SG migration, especially in tortuous arteries. Stents derived from auxetic unit cells have shown some potential to address these issues as they offer an optimum trade-off between radial stiffness and bending flexibility.MethodsIn this study, we utilized an established finite element (FE)-based approach to replicate the mechanical response of a SG iliac limb derived from auxetic unit cells in a virtual tortuous iliac aneurysm using a combination of a 180° U-bend and intraluminal pressurization. This study aimed to compare the mechanical performance (flexibility and durability) of SG limbs derived from auxetic unit cells and two commercial SG limbs (Z-stented SG and circular-stented SG models) in a virtual tortuous iliac aneurysm. Maximal graft strain and maximum stress in stents were employed as criteria to estimate the durability of SGs, whereas the maximal luminal reduction rate and the bending stiffness were used to assess the flexibility of the SGs.ResultsSG limbs derived from auxetic unit cells demonstrated low luminal reduction (range 4–12%) with no kink, in contrast to Z-stented SG, which had a kink in its central area alongside a high luminal reduction (44%).ConclusionsSG limbs derived from auxetic unit cells show great promise for EVAR applications even at high angulations such as 180°, with acceptable levels of durability and flexibility.

Multi-objective design optimization of bioresorbable braided stents

Background and objectivesBioresorbable braided stents, typically made of bioresorbable polymers such as poly-l-lactide (PLLA), have great potential in the treatment of critical limb ischemia, particularly in cases of long-segment occlusions and lesions with high angulation. However, the successful adoption of these devices is limited by their low radial stiffness and reduced elastic modulus of bioresorbable polymers. This study proposes a computational optimization procedure to enhance the mechanical performance of bioresorbable braided stents and consequently improve the treatment of critical limb ischemia. MethodsFinite element analyses were performed to replicate the radial crimping test and investigate the implantation procedure of PLLA braided stents. The stent geometry was characterized by four design parameters: number of wires, wire diameter, initial stent diameter, and braiding angle. Manufacturing constraints were considered to establish the design space. The mechanical performance of the stent was evaluated by defining the radial force, foreshortening, and peak maximum principal stress of the stent as objectives and constraint functions in the optimization problem. An approximate relationship between the objectives, constraint, and the design parameters was defined using design of experiment coupled with surrogate modelling. Surrogate models were then interrogated within the design space, and a multi-objective design optimization was conducted. ResultsThe simulation of radial crimping was successfully validated against experimental data. The radial force was found to be primarily influenced by the number of wires, wire diameter, and braiding angle, with the wire diameter having the most significant impact. Foreshortening was predominantly affected by the braiding angle. The peak maximum principal stress exhibited contrasting behaviour compared to the radial force for all parameters, with the exception of the number of wires. Among the Pareto-optimal design candidates, feasible peak maximum principal stress values were observed, with the braiding angle identified as the differentiating factor among these candidates. ConclusionsThe exploration of the design space enabled both the understanding of the impact of design parameters on the mechanical performance of bioresorbable braided stents and the successful identification of optimal design candidates. The optimization framework contributes to the advancement of innovative bioresorbable braided stents for the effective treatment of critical limb ischemia.

Is There an Advantage of Ultrathin-Strut Drug-Eluting Stents over Second- and Third-Generation Drug-Eluting Stents?

In patients undergoing percutaneous coronary intervention, the second-generation drug-eluting stents (DES) are considered the gold standard of care for revascularization. By reducing neointimal hyperplasia, drug-eluting coronary stents decrease the need for repeat revascularizations compared with conventional coronary stents without an antiproliferative drug coating. It is important to note that early-generation DESs were associated with an increased risk of very late stent thrombosis, most likely due to delayed endothelialization or a delayed hypersensitivity reaction to the polymer. Studies have shown a lower risk of very late stent thrombosis with developing second-generation DESs with biocompatible and biodegradable polymers or without polymers altogether. In addition, research has indicated that thinner struts are associated with a reduced risk of intrastent restenosis and angiographic and clinical results. A DES with ultrathin struts (strut thickness of 70 µm) is more flexible, facilitates better tracking, and is more crossable than a conventional second-generation DES. The question is whether ultrathin eluting drug stents suit all kinds of lesions. Several authors have reported that improved coverage with less thrombus protrusion reduced the risk of distal embolization in patients with ST-elevation myocardial infarction (STEMI). Others have described that an ultrathin stent might recoil due to low radial strength. This could lead to residual stenosis and repeated revascularization of the artery. In CTO patients, the ultrathin stent failed to prove non-inferiority regarding in-segment late lumen loss and showed statistically higher rates of restenosis. Ultrathin-strut DESs with biodegradable polymers have limitations when treating calcified (or ostial) lesions and CTOs. However, they also possess certain advantages regarding deliverability (tight stenosis, tortuous lesions, high angulation, etc.), ease of use in bifurcation lesions, better endothelialization and vascular healing, and reducing stent thrombosis risk. In light of this, ultrathin-strut stents present a promising alternative to existing DESs of the second and third generation. The aims of the study are to compare ultrathin eluting stents with second- and third-generation conventional stents regarding procedural performance and outcomes based on different lesion types and specific populations.

Comparison of accuracy of hexed and nonhexed pickup impression copings in a multiple variable impression setup for recording multiple straight and angulated implant positions: An in vitro study.

The aim of this study was to evaluate and compare the accuracy of hexed and nonhexed pickup impression copings with and without splinting using polyether (PE) and polyvinyl siloxane (PVS) impression materials in open-tray technique in recording multiple straight and angulated implant positions. An accurate impression results in an accurate definitive cast, thus minimizing the incidence of prosthesis misfit. The critical aspect is to record the three-dimensional location of the implant in bone rather than reproducing fine surface details. Precise fit of a fixed implant-supported prosthesis depends on the accuracy of the implant analog location within the definitive cast. Factors which affect impression accuracy include implant angulation, impression material, impression copings, technique, and splinting. A sample size of 80 study models fabricated from the impression of different groups was included. A reference master model based on All-on-4 implant concept with two parallel (implants 1 and 2) and two angulated (implant 3 at 17° and implant 4 at 30°) was fabricated using implant angulation guide. All impressions were recorded using open-tray impression technique. The groups were divided into two main groups of 40 samples each. Group A used hexed open-tray impression copings and Group B used nonhexed open-tray impression copings. Both the groups involved impression recording using splinted (Subgroup I) and nonsplinted impression copings (Subgroup II). Further, impressions in each subgroup were made using PE (Subsubgroups a) and PVS (Subsubgroup b). A total of eight subsubgroups with ten samples each were included. Impressions were recorded for each group and poured into Type IV die stone for fabrication of study models. After 24 h, the study models and reference master model were fitted with implant abutments for measurement with coordinate measuring machine. The mean differences of the interimplant distance R1 (1-2), R2 (1-3), R3 (2-4), and R4 (3-4) between the reference model and sample models in different subsubgroups were calculated and three-way analysis of variance test was applied with Tukey's post hoc tests. No significant difference was found in mean coronal deviations for distance R1, R2, and R3 (P > 0.05) between different study groups. P = 0.02 for R4 (distance between 17° and 30° implants) between impression materials subsubgroups suggested that significantly less distortion was created in location of highly angulated implants (>30°) using PVS impression material. Splinting and type of coping did not have a significant influence on impression accuracy. Increasing angulation decreased the accuracy. PVS was found equivalent in accuracy to rigid PE for recording parallel or angulated implants. Impressions of implants with higher angulations were recorded more accurately with PVS. The study found no difference in accuracy with or without splinting. Furthermore, nonhexed impression copings facilitate easier and accurate recording of multiple angulated implant location in bone.

Assessing the Effect of Interimplant Distance and Angle on Different Impression Techniques

We aimed to evaluate the trueness of digital and conventional impression techniques based on different angles and distances between implants and the deviation caused by the angle and distance parameters varying between implants. Eight implants were placed in a polyurethane edentulous mandibular model at different angles and distances. After obtaining a 3-dimensional (3D) reference model by using an optical scanner, the model was scanned with three intraoral scanners: Cerec Omnicam (DO), Trios 3 (DT), and Carestream 3500 (DC). Then, the master casts obtained from the conventional impressions (C) were also digitized, and all impression data were imported into reverse engineering software to be compared with the 3D reference model. Distance and angle measurements between adjacent implants were performed, and the data were analyzed with ANOVA–Tukey and Kruskal Wallis tests. The significance level was accepted as p < 0.05. While DT and C groups gave the best results for high interimplant distances, the trueness of intraoral scanners was found to be superior to the conventional method between closer implants. At higher angulations, the angular trueness of C group was found to be significantly lower. At short distances, digital groups showed superiority, and the trueness of conventional impression decreased with higher angulations.

Multicenter observational study of the gore excluder conformable endograft for endovascular abdominal aortic repair: Initial results

Abstract Objective Endovascular repair (EVAR) has become the standard of care for treatment of abdominal aortic aneurysms. However, a significant number of EVAR remains outside the IFU, especially in cases of severe proximal angulation (>60 degrees), resulting in failure. The new device GORE EXCLUDER Conformable AAA Endoprosthesis (W. L. Gore & Associates, Flagstaff, Ariz) has been designed to accommodate neck angulation, due to conformability and angulation control. The aim of this multicenter study is to report the initial results of this device. Methods From March 2019 to January 2021, the data of all consecutive patients with AAA treated with the Gore Excluder Conformable endograft at 4 vascular centers were reviewed. Patients were followed using a standardized protocol, with CT-scan at 1, 6 and 12 months, and then yearly. The primary endpoint was technical success and secondary outcomes were postoperative morbidity, rate of endoleak (EL) and any aneurysm-related re-interventions during follow-up. Results Among the 32 patients included, most were men with a mean age of 77 years old (range 60-92). Half of patients were smokers and 72% had hypertension. The mean diameter of AAA was 62 mm (47-90). The mean length of aortic neck was 26 mm (10-69), the mean diameter 23 mm (16-31) and the median neck angulation was 81 degrees (range 40-110). The mean procedural duration was 102 min (54-153) with a mean time of scopy of 24 min (8-47) and a total volume of contrast of 101 ml (40-165). Thirteen iliac branch device have been used in 7 patients. The technical success was 97% with 1 type Ia EL (3%). In the post-operative period, 4 medical and 3 surgical complications were observed. Two reinterventions were needed with an iliac stenting for a stenosis and a correction of a femoral false aneurysm. During the mean follow-up of 7 months, 2 type Ia ELs were observed. One spontaneously resolved and the other one was followed. One distal limb extension was succesfully implanted at 3 months for a type Ib EL for a total rate of reintervention of 9%. No migration was observed. No death occured. Conclusion The use of the Gore Excluder Conformable endograft seems to be safe and effective in difficult anatomies and especially high angulation. It allows for precise deployment without the need for additional contrast or operation time. Longer follow-up and more patients are required to confirm these excellent initials results.

Three-Dimensional Accuracy of Conventional Versus Digital Complete Arch Implant Impressions.

The accuracy of digital impressions is still controversial for complete arch implant cases. The aim of this study is to compare the accuracy of different intraoral scanners with the conventional technique in terms of trueness and precision in a complete arch implant model. Eight implants were inserted asymmetrically in a polyurethane edentulous mandibular model with different angulations. A 3-dimensional (3D) reference model was obtained by scanning this polyurethane model with an optical scanner. First, digital impressions were made by using 3 different intraoral scanners: Carestream 3500 (DC), Cerec Omnicam (DO) and 3Shape Trios 3 (DT). Subsequently, a nonsplinted open tray impression technique was used for conventional impression group (C) and then the master casts were digitalized with a lab scanner. Each 10 STL files belonging to 4 different impression groups were imported to a reverse engineering program, to measure distance and angle deviations from the reference model. All statistical analyses were performed after taking absolute values of the data. After comparing the impression groups with one-way ANOVA, the trueness and precision values were analyzed by Tukey post hoc test and 0.05 was used as the level of significance. The mean trueness of distance was 123.06 ± 89.83 µm for DC, 229.72 ± 121.34 µm for DO, 209.75± 47.07 µm for DT, and 345.32 ± 75.12 µm for C group (p < 0.0001). While DC showed significantly lower deviation compared to DO and C, no significant difference was found between DC and DT. C showed the highest distance deviation significantly in all groups; and no significant difference was found between DO and DT groups. In angle measurements; the trueness was 0.26° ± 0.07° for DC, 0.53° ± 0.42° for DO, 0.33° ± 0.30° for DT, and 0.74° ± 0.65° for C group. There was no significant difference between the groups in terms of angular trueness (p = 0.074). In terms of the precision for distance, the results of DC 80.43 ± 29.69µm, DO 94.06 ± 69.96 µm, DT 35.55 ± 28.46 µm and C 66.97 ± 36.69 µm were determined (p = 0.036). The significant difference was found only between DT and DO among all groups. Finally, angular precision was determined to be 0.19° ± 0.11° for DC, 0.30° ± 0.28° for DO, 0.22° ± 0.19° for DT, and 0.50° ± 0.38° for Group C. No significant difference was found between the groups, in terms of angular precision (p = 0.053). All digital impression groups yielded superior data compared to conventional technique in terms of trueness. DC formed the impression group with the highest trueness in both distance and angular measurements. The results of this in vitro study suggest the use of intraoral scanners compared to the conventional impression techniques in complete arch implant cases with high angulations.

Suitability of the Aortic Neck Anatomy for Endovascular Aneurysm Repair in Korean Patients with Abdominal Aortic Aneurysm.

PurposeTo evaluate the aortic neck anatomy in Korean patients with abdominal aortic aneurysms (AAAs).Materials and MethodsWe examined computed tomography scans of 343 patients with AAAs (≥5.5 cm for men or ≥5 cm for women) between 2009 and 2018. Eligibility of neck anatomy for endovascular aneurysm repair (EVAR) was assessed with the standard instructions for use (IFU) (length ≥15 mm, suprarenal angulation (SRA) ≤45°, infrarenal angulation (IRA) ≤60°, and diameter 18-32 mm) and the extended IFU (length ≥10 mm, SRA ≤60°, IRA ≤75°, and diameter 17-32 mm).ResultsThere were 71 women (20.7%), and 61 patients (17.8%) with rupture. Women had smaller neck diameters (21.3 vs. 23.4 mm, P<0.001 for proximal neck; 22.2 vs. 24.5 mm, P<0.001 for distal neck), and higher angulations (51.5° vs. 37.8°, P<0.001 for SRA; 77.7° vs. 57.0°, P<0.001 for IRA) than men. However, the neck length was not significantly different. Patients with ruptured AAAs had shorter neck lengths (21.0 vs. 26.8 mm, P=0.005) than those with intact AAAs. However, the neck diameters and angulations were not significantly different. EVAR eligibility for standard and extended IFUs was found in 37.5% and 55.1% of men, and 11.3% and 25.4% of women (P<0.001 for both IFUs); neck anatomy was eligible in 34.0% of intact AAAs and 23.0% of ruptured AAAs (P=0.098).ConclusionA significant proportion of the Korean patients did not meet the IFU for EVAR, mainly due to the angulated neck. Women, and patients with ruptured AAAs, were less likely to meet the IFU criteria.

Tortuosity of the Descending Thoracic Aorta in Patients with Aneurysm and Type B Dissection: A Quantitative Analysis

Introduction: Tortuosity in the descending thoracic aorta is becoming more important since thoracic endovascular aortic repair (TEVAR) is the gold standard for treating thoracic aortic disease. The literature reports that tortuosity has an influence on the occurrence of endoleaks1. There is some literature defining the angulation and tortuosity of the aortic arch. Recently, a new classification has been published, an extended version of the Ishimaru classification of the four landing zones in the aortic arch2,3. However, zone 4 of the Ishimaru classification and further distally have not been well described yet. The general insight is that tortuosity comes with aging in the descending thoracic aorta. With this report we want to define and classify the tortuosity in the diseased descending thoracic aorta. Methods: A total number of two hundred seven patients were divided into three groups. Sixty-nine healthy patients, with no vascular diseases, were compared with sixty-nine patients with descending thoracic aneurysm (DTA) and sixty-nine patients with type B aortic dissection (TBD). CTA scans, with thin cut slices (1.0 or 1.5 mm) were analyzed with 3Mensio Vascular software and the following measurements were collected; tortuosity index (length of the centre lumen line divided by the true length), curvature ratio (outer curvature length divided by length centre lumen line), the maximum and minimum angulation in degrees of the descending thoracic aorta and the level of vertebrae of the maximum and minimum angulation. The descending thoracic aorta was analyzed from two cm distal to the Left Subclavian Artery up to the Celiac Trunk and was divided into four zones of equal length, from proximal to distal, numbered one to four. Additionally, the maximum angulation was divided into three groups: low (< 30°), moderate (30° – 60°) and high angulation (> 60°). Results: The mean age of the Healthy group (HG) was 68.3 years old, in the Aneurysm group (AG) 72.2 and in the Dissection group (DG) 64.1. Compared to the HG, tortuosity was more pronounced in the DG, and even more in the AG, as evidenced by the tortuosity index (1.11 vs. 1.20 vs. 1.31, respectively; p < 0.001), curvature ratio (1.00 vs. 1.01 vs. 1.03; p < 0.001), maximum angulation in degrees (28.17 vs. 33.29 vs. 43.83; p < 0.001), and group of angulation (1.00 vs. 2.00 vs. 1.00; p < 0.001). Additionally, compared to HG, the location of maximum angulation was further distal for the DG and even further in the AG, as evidenced by the vertebral level of maximum angulation (5.00 vs. 7.00 vs. 8.00; p < 0.001), and zone of maximum angulation (1.00 vs. 2.00 vs. 2.00; p < 0.001). Conclusion: This study shows that tortuosity in the descending thoracic aorta becomes even more prominent in diseased aortas, especially for patients with aneurysmal diseases. The upcoming endovascular technology and interventions have to handle with this phenomenon in order to prevent aortic complications and to obtain positive long-term outcome.

Geometric Torsion in Adolescent Idiopathic Scoliosis: A Surgical Outcomes Study of Lenke Type 1 Patients.

Consecutive case series analysis. To evaluate the surgical outcomes of patients with thoracic adolescent idiopathic scoliosis (AIS) in relation to different degrees of geometric torsion. AIS is a three-dimensional (3D) deformity of the spine. A 3D classification of AIS, however, remains elusive because there is no widely accepted 3D parameter in the clinical practice. Recently, a new method of estimating geometric torsion has been proposed and detected two potential new 3D subgroups based on geometric torsion values. This is an analysis of 93 patients with Lenke type-1 deformity from our institution. 3D reconstructions were obtained using biplanar radiographs both pre- and postoperatively. Geometric torsion was computed using a novel technique by approximating local arc lengths at the neutral vertebra in the thoracolumbar segment. An inter- and intragroup statistical analysis was performed to compare clinical indices of patients with different torsion values. A qualitative assessment was also performed on each patient by two senior staff surgeons. Statistically significant differences were observed in clinical indices between high (2.85 mm) and low torsion (0.83 mm) Lenke type 1 subgroups. Preoperatively, the high torsion group showed higher Cobb angle values in the thoracic segment (71.18° vs. 63.74°), as well as higher angulation in the thoracolumbar plane of maximum deformity (67.79° vs. 53.30°). Postoperatively, a statistically significant difference was found in the orientation of the plane of maximum deformity in the thoracolumbar segment between the high and low torsion groups (47.95° vs. 30.03°). Results from the qualitative evaluation of surgical results showed different results between the two staff surgeons. These results suggest a link between preoperative torsion values and surgical outcomes within Lenke type 1 deformities. These results will need to be validated by an independent group, as it is a single-center study. 4.

Influence of implant-abutment angulations and crown material on stress distribution on central incisor: a 3D FEA

Aim: To investigate the effect of implant-abutment angulation and crown material on stress distribution of central incisors. Finite element method was used to simulate the clinical situation of a maxillary right central incisor restored by two different implant-abutment angulations, 15° and 25°, using two different crown materials (IPS E-Max CAD and zirconia). Methods: Two 3D finite element models were specially prepared for this research simulating the abutment angulations. Commercial engineering CAD/CAM package was used to model crown, implant abutment complex and bone (cortical and spongy) in 3D. Linear static analysis was performed by applying a 178 N oblique load. The obtained results were compared with former experimental results. Results: Implant Von Mises stress level was negligibly changed with increasing abutment angulation. The abutment with higher angulation is mechanically weaker and expected to fail at lower loading in comparison with the steeper one. Similarly, screw used with abutment angulation of 25° will fail at lower (about one-third) load value the failure load of similar screw used with abutment angulated by 15°. Conclusions: Bone (cortical and spongy) is insensitive to crown material. Increasing abutment angulation from 15° to 25°, increases stress on cortical bone by about 20% and reduces it by about 12% on spongy bone. Crown fracture resistance is dramatically reduced by increasing abutment angulation. Zirconia crown showed better performance than E-Max one.

Five-Year Results of the Valor II Trial of the Medtronic Valiant Thoracic Stent Graft

Five-Year Results of the Valor II Trial of the Medtronic Valiant Thoracic Stent Graft

High Angulation and Short Neck Length Do Not Impact AAA Sac Expansion After Repair Using the Lombard Aorfix Device

High Angulation and Short Neck Length Do Not Impact AAA Sac Expansion After Repair Using the Lombard Aorfix Device

BS2. High Angulation and Short Neck Length Do Not Impact AAA Sac Expansion After Repair Using the Lombard Aorfix Device

Angulated (≥60°) infrarenal aortic necks and short neck lengths, are associated with sac expansion following EVAR. Aorfix (Lombard Medical), a conformable stent graft designed for highly angulated necks, was investigated in the U.S. Pythagoras Trial. We hypothesized that sac expansion may be independent of neck angle and length after AAA repair with Aorfix grafts. Trial data were assessed with mutivariable modeling for factors associated with sac regression/expansion (R/E), defined as change in maximum aneurysm diameter of ≥5 mm on annual follow-up computed tomography (CT) compared with the last preoperative scan). Sac expansion after Aorfix implantation was compared in “standard angle” (<60°) and “high angle” (≥60°) proximal necks. Neck length measurements were performed per protocol by a core laboratory, M2S. A total of 210 patients with implants were followed up ≥30 days; neck angle was ≥60° in 151 (71.9%), < 60° in 59 (28.1%). Mean neck length was 23.1 mm. Follow-up, including CT imaging, was available at 1 year (n = 165), 2 years (n = 142), 3 years (n = 106), and 4 years (n = 70). Sac size decreased or was unchanged in 98.8% (1 year), 95.1% (2 years), 94.3% (3 years), and 92.9% (4 years; Fig 1). Factors associated with sac regression at 4 years include less calcified plaque in the proximal aortic neck (odds ratio [OR] 3.84; P = .02) and iliac arteries (OR, 3.36; P = .04), and length of neck apposition (OR, 2.21; P = .04). Longer distance from lowest renal artery to proximal graft was associated with sac expansion at 4 years (OR, 1.89; P = .001). Sac R/E was not related to neck length, neck diameter, internal iliac artery patency, maximal aneurysm diameter, patient age or gender, and nine other demographic variables (P > .05 for all). Absence of endoleak was associated with sac regression at 1 and 2 years (OR, 5.98; P = .02; OR, 17.6; P < .001) but not at 3 and 4 years (P > .05). Neck angle was not associated with sac R/E (P > .45 all timepoints). In distinction from previous reports, increased neck angulation and neck length do not predict sac R/E with Aorfix grafts.

Numerical Simulation for Design Evaluation of Thoracic Stent Graft to Investigate the Migration Phenomena and Type 1a Endoleak of Thoracic Aneurysm

Migration and endoleak phenomena are considered to be the principal reasons for Endovascular Aneurysm Repair failure. Wide differences of opinion exist regarding the nature of these critical complications. They occur when there is non-complete and ineffective contact between the endograft ends and the wall of the blood vessel. A major goal of present work is to investigate, using the Finite Element Method, the effect of nitinol stent design on the overall effectiveness of contact and radial force. The specific-patient aneurysmal thoracic aorta are challenging. The optimized stent results show better contact stability to resist the migration. They also show a good compromise of stent design requirements (flexibility and stiffness). Moreover, the new design can also prevent the risk of folding or the collapse of stent struts by mitigating the energy of eccentric deformation caused by high angulation and oversizing.

Evaluation of first metatarsal head declination through a modified distal osteotomy in hallux rigidus surgery. A cadaveric model.

First metatarsal osteotomies have been described for treatment of hallux rigidus. Most of these techniques result in declination of the first metatarsal head through shortening of the metatarsal and transfer metatarsalgia may result. Our objective was to evaluate the declination effect of a distal metatarsal osteotomy when different angulations and lateral translations are applied. A cadaveric study was conducted performing a modified distal oblique osteotomy, which produces head declination while limiting shortening. Several transverse inclination angles (0-10-20-30-40°) were used. Thereafter, plantar translation of the metatarsal head was registered at different lateral displacements (1, 3, 5mm). Twenty-two specimens were included. Three feet were operated on with a 0° of angulation in the transverse plane, 6 with 10°, 5 with 20°, 5 with 30°, and 3 with 40°. Head declination significantly increased with higher angulation and with greater lateral translations (p<0.001), but the interrelationship between these two variables did not achieve statistical significance (p=0.597). In regards to angulation, significant differences in head declination were found between 0° (0.1-0.7 mm), 10°-20° (0.5-1.2mm) and 30°-40° (1.3-2.4mm). The metatarsal sesamoid joint was compromised when the osteotomy was performed at a 40° inclination angle. Metatarsal head declination is determined by the inclination angle of the oblique limb of the osteotomy and lateral displacement of the metatarsal head. Our results suggest that the effect of lateral displacement is an independent factor from angulation. The latter may impact surgery planning and may improve clinical outcome by selecting a safer inclination angle when lateral displacement of the metatarsal head is being considered. Level II-A, systematic review with homogeneity of cohort studies.

What if you stretch the IFU? A mechanical insight into stent graft Instructions For Use in angulated proximal aneurysm necks

Endovascular treatment for patients with a proximal neck anatomy outside instructions for use is an ongoing topic of debate in endovascular aneurysm repair. This paper employs the finite element method to offer insight into possible adverse effects of deploying a stent graft into an angulated geometry. The effect of angulation, straight neck length and device oversize was investigated in a full factorial parametric analysis. Stent apposition, area reduction of the graft, asymmetry of contact forces and the ability to find a good seal were investigated. Most adverse effects are expected for combinations of high angulation and short straight landing zones. Higher oversize has a beneficiary effect, but not enough to compensate the adverse effects of (very) short and angulated angles. Our analysis shows that for an angle between the suprarenal aorta and proximal neck above 60°, proximal kinking of the device can occur. The method used offers a engineering view on the morphological limits of EVAR for a clinically used device.

Limb alignment, subluxation, and bone density relationship in the osteoarthritic varus knee.

Lower limb alignment, tibiofemoral (TF) subluxation, and bone density changes around the knee are significant factors related to the development of knee osteoarthritis (OA) and have great impact on its severity. The relation of each factor to knee OA was evaluated separately in previous studies; however, few studies have attempted to integrate their respective effects. The purpose of this study was to determine if an identifiable interaction exists between coronal limb alignment, TF subluxation, and bone density in the development of knee OA. A total of 120 patients with symptomatic, varus knee OA, with preoperative standing anteroposterior (AP) hip-to-ankle radiographs and a computed tomographic scan of the knee, were included in this study. Overall mechanical lower extremity alignment, and TF subluxation were measured on the AP radiographs, while trabecular bone density (TBD) was measured in four regions of interest for both the tibial plateau and distal femur in all patients. The patients were stratified into the following four cohorts: (A) high subluxation, high angulation; (B) high subluxation, low angulation; (C) low subluxation, high angulation; and (D) low subluxation, low angulation. The mean TBD in group B was significantly higher than in groups C and D (p = 0.003 and 0.03, respectively). In addition, the mean TBD in group A was significantly higher than in group C. This study highlights the relationship between limb alignment, knee subluxation, and bone density in the osteoarthritic knee. These preliminary results present a proof-of-principle, that bone mineral density affects the degree of coronal alignment and TF subluxation in OA.

Aortic endovascular repair modeling using the finite element method

Aim: The goal is to simulate different stages of the endovascular procedure in the preoperative phase. Methods: We have developed a numerical model of the endovascular treatment of abdominal aortic aneurysms (AAA) using finite element analysis (FEA), we took into account the geometry of the biological region reconstructed from scans, a local characterization of the guidewire/catheter mechanical properties, a mapping of material properties depending on the degree of calcification, a real behavior of the vascular walls, and a projection of the aorta environment. Results: Our results present the endovascular system navigation from the femoral artery to the neck of the aneurysm, predict the deformation of femoral, iliac and aortic arteries while driving flexible and stiff endovascular devices, and detect stress concentration due to tortuous and calcified artery zones. A given group of patients with very angulated and calcified arteries were validated, based on a tuning between clinical data and our endovascular simulation. Conclusion: Our model allows controlling with accuracy the delivery system rise during surgery, predicting the feasibility of the surgery with reliability as well as choose the best guide for each patient, taking into account the risk of rupture of calcified areas in the case of high angulations, and using planning simulated images with deformation of artery walls to propose stent sizing.

Final Results of the Prospective European Trial of the Endurant Stent Graft for Endovascular Abdominal Aortic Aneurysm Repair

Objectives The Endurant Stent Graft System (Medtronic Vascular, Santa Rosa, CA) is specifically designed to treat patients with abdominal aortic aneurysm, including those with difficult anatomies. This is the 1-year report of a prospective, non-randomised, open-label trial at 10 European centres. Methods Between November 2007 and August 2008, 80 patients were enrolled for elective endovascular aneurysm repair (EVAR) with the Endurant; 71 with moderate (≤60°) and nine with high (60–75°) infrarenal aortic neck angulation. Safety and stent-graft performance were assessed throughout a 1-year follow-up period. Results The device was successfully delivered and deployed in all cases. All-cause mortality was 5% (4/80), with one possibly device-related death. Serious adverse events were comparable between the high and moderate angulation groups. There were no device migrations, stent fractures, aortic ruptures or conversions to open repair. Maximal aneurysm diameter decreased >5 mm in 42.7% of cases. A total of 28 endoleaks were observed (26 type II, two undetermined). Three secondary endovascular procedures were performed for outflow vessel stenosis, graft limb occlusion and iliac extension, resulting in a secondary patency rate of 100%. No re-interventions were required in the high angulation group. Conclusions The Endurant Stent Graft was successfully delivered and deployed in all cases and performed safely and effectively in all patients, including those with unfavourable proximal neck anatomy.