Implantation Angle Research Articles

Determining the Rotational Orientation of Directional Deep Brain Stimulation Leads Employing Flat-Panel Computed Tomography.

Directional deep brain stimulation (DBS) constitutes an emerging technology that allows selective stimulation of target structures via partitioned electrode contacts. In order to effectively perform target-tailored stimulation, knowledge of the rotational orientation of the segmented leads is imperative. To develop a universally applicable and reliable method for determination of lead orientation angles in DBS using flat-panel computed tomography (fpCT). A binary template of directional leads DB-2202-30 (Boston Scientific, Natick, Massachusetts) and 6170 (Abbott, Plano, Texas) was imported into the 2-dimensional raw data set of a conventional fpCT scan. The template was aligned with and manually rotated around the predetermined lead trajectory. The overall orientation of the segmented lead can be deduced by transferring position and orientation of the lead orientation marker into the 3-dimensional volume. Accuracy of the method was investigated by two raters in a phantom study. Accuracy were 5.4°±4.1° (range: 0.4°-11.9°) for rater 1 and 5.2°±3.0° (range: 0.3°-10.2°) for rater 2, when investigating DB-2202-30. For 6170 observed deviations were 2.5°±1.7° (range: 0.2°-5.2°) and 4.3°±3.6° (range: 0.2°-11.2°) for raters 1 and 2, respectively. fpCT imaging constitutes a precise and accurate means to determine the rotational orientation of directional leads. The approach is universally transferable to different electrode designs as the template can easily be adjusted to the electrodes' specific measures. The approach is independent from polar implantation angles owing to fpCT- and methodological features.

Sustainability of Individual EndoAnchor Implants in Therapeutic Use to Treat Type Ia Endoleak After Endovascular Aneurysm Repair

Purpose: To investigate changes in penetration depths and angles of EndoAnchor implants with initially good penetration after therapeutic use in endovascular aneurysm repair. Materials and Methods: Patients were selected from the Aneurysm Treatment Using the Heli-FX Aortic Securement System Global Registry (ANCHOR; ClinicalTrials.gov identifier NCT01534819). Inclusion criteria were (1) EndoAnchor implantation to treat intraoperative or late type Ia endoleak and (2) at least 2 postoperative computed tomography angiography (CTA) scans. Exclusion criteria were the use of adjunct procedures. Based on these criteria, 54 patients (44 men) with 360 EndoAnchor implants were eligible for this analysis. Penetration depth of each EndoAnchor implant into the aortic wall was judged as (1) good (≥2-mm penetration), (2) borderline (<2 mm or when there was a gap between the endograft and the aortic wall), or (3) no penetration. The penetration depth and longitudinal angles of EndoAnchors with good penetration were investigated on the last available postprocedure CTA scan. Endoleaks were also analyzed. Results: EndoAnchor penetration on the first postprocedure CTA scan was good in 187 (51.9%), borderline in 69 (19.2%), and missing in 104 (28.9%). On the last CTA scan, 182 (97.4%) of the 187 initially well-positioned EndoAnchors remained good. Five (2.6%) EndoAnchors in 4 patients changed configuration over time (4 became borderline and 1 became nonpenetrating), all without any clinical sequelae. The median orthogonal angles of the EndoAnchor implants with good penetration on the first and last CTA scans were 92° [interquartile range (IQR) 85, 98] and 90° (IQR 84, 97), respectively (p=0.822); for longitudinal angles, medians of 85° (IQR 71, 96) and 84° (IQR 70, 96) were found (p=0.043). Of the 18 (33%) patients who had a type Ia endoleak on the first postprocedure CTA, 6 resolved over time. Median follow-up was 13 months, during which no new type Ia endoleak was found. Conclusion: Despite the small number of EndoAnchors analyzed, this study showed that the sustainability of EndoAnchor implants with initially good penetration is satisfactory at 1-year follow-up. The vast majority of EndoAnchor implants with good penetration initially remained in good position; <3% of implants became borderline or nonpenetrating, without any clinical consequence.

Inverted Aortic Prosthesis in the Mitral Position: Is Upside Down Always the Right Side Up?

Evaluation of prosthetic valve function is a challenging task. The clinician has to employ multiple parameters to quantify dysfunction (if present), the results of which can be mutually discrepant. This results from heterogeneity in the design of the valves themselves, implantation techniques, and both intra- and interpatient hemodynamic variability. Specifically, the location and angle of valve implantation can have a profound impact on its flow characteristics that can lead to symptoms despite satisfactory mechanical function. The authors present the case of inverted implantation of a prosthesis designed for the aortic position in the mitral annulus and resultant mitral stenosis. What follows is an examination of how the flow characteristics, such as pressure recovery, energy loss, and vortex formation, create a gradient that could not be explained by valve size alone.

Biomechanical comparison of implant inclinations and load times with the all-on-4 treatment concept: a three-dimensional finite element analysis

The purpose of this study was to compare the effects of implant inclinations and load times on stress distributions in the peri-implant bone based on immediate- and delayed-loading models. Four 3D FEA models with different inclination angle of the posterior implants (0°, 15°, 30°, 45°) were constructed. A static load of 150 N in the multivectoral direction was applied unilaterally to the cantilever region. The stress distributions in the peri-implant bone were evaluated before and after osseointegration. The principal tensile stress (σmax), mean principal tensile stress (σmax), principal compressive stress (σmin) and mean principal compressive stress (σmin) of the bone and micromotion at the contact interface between the bone and implants were calculated. In all the models, peak principal stresses occurred in the bone surrounding the left tilted implant. The highest σmax and σmin were all observed in the 0° model for both immediate- and delayed-loading models. And the 0° and 15° models showed higher σmax and σmin values. The 0°models showed the largest micromotion. The observed stress distribution was better in the 30° and 45° models than in the 0° and 15° models.

Computer-aided dynamic navigation: a novel method for guided endodontics.

To investigate the novel use of computer-aided dynamic navigation for guided endodontics. Dental casts were fabricated from sets of extracted human teeth. A cone beam computed tomography (CBCT) scan of each cast, with a molded thermoplastic stent and a radiographic marker attached, was obtained and imported into the planning software of a dynamic navigation implant surgery system. Simulating implant surgery but for guided endodontics, the drilling entry point, angle, pathway, and depth of virtual implants were planned for 29 selected teeth. The radiographic marker was replaced with a jaw tag and mounted in a phantom head. A drill tag was attached to the drill handpiece. Following calibration, guided by the stereoscopic motion-tracking camera via the tags and images on a computer monitor providing real-time dynamic plus visual intraoperative feedback, the handpiece was aligned accordingly and endodontic access cavity preparation carried out. Successful root canal location was confirmed using periapical radiographs and CBCT. Conservative access cavities were achieved and all the expected canals were successfully located in 26 teeth (n = 29). Due to tracking difficulties, only one canal was located in two maxillary second molars; in a maxillary first molar, only two canals were located and the access preparation for the third canal was misaligned and off-target. The results of this study demonstrate the potential of using computer-aided dynamic navigation technology in guided endodontics in clinical practice.

Morphometric Analysis of the Lumbar Vertebrae Concerning the Optimal Screw Selection for Transpedicular Stabilization.

Transpedicular stabilization is a frequently used spinal surgery for fractures, degenerative changes, or neoplastic processes. Improper screw fixation may cause substantial vascular or neurological complications. This study seeks to define detailed morphometric measurements of the pedicle (height, width, and surface area) in the aspects of screw length and girth selection and the trajectory of its implantation, i.e., sagittal and transverse angle of placement. The study was based on CT examinations of 100 Caucasian patients (51 women and 49 men) aged 27-75 with no anatomical, degenerative, or post-traumatic spine changes. The results were stratified by gender and body side, and they were counter compared with the available literature database. Pedicle height decreased from L1 to L4, ranging from 15.9 to 13.3mm. Pedicle width increased from L1 to L5, extending from 6.1 to 13.2mm. Pedicle surface area increased from L1 to L5, ranging from 63 to 140mm2. Distance from the point of entry into the pedicle to the anterior surface of the vertebral body, defining the maximum length of a transpedicular screw, varied from 54.0 to 50.2mm. Variations concerning body sides were inappreciable. A transverse angle of screw trajectory extended from 20° to 32°, shifting caudally from L1 to L5, with statistical differences in the L3-L5 segments. A sagittal angle varied from 10° to 12°, without such definite relations. We conclude that the L1 and L2 segments display the most distinct morphometric similarities, while the greatest differences, in both genders, are noted for L3, L4, and L5. The findings enable the recommendation of the following screw diameters: 4mm for L1-L2, 5mm for L3, 6mm for L4-L5, and the length of 50mm. We believe the study has extended clinical knowledge on lumbar spine morphometry, essential in the training physicians engaged in transpedicular stabilization.

Accuracy of acetabular cup placement using CT-based navigation in total hip arthroplasty: Comparison between obese and non-obese patients

BackgroundIn obese patients, malpositioning of the acetabular cup increases the risk of dislocation in total hip arthroplasty (THA). The aim of this study was to determine whether obesity affects the accuracy of acetabular cup positioning using a computed tomography (CT)-based navigation system. MethodsWe retrospectively evaluated 226 consecutive patients who underwent cementless primary THAs assisted by the CT-based hip navigation system. We divided the patients into three groups according to body mass index (BMI) and examined the difference between preoperative planning and postoperative implantation angles from CT data. ResultsThere was no significant correlation between BMI and both inclination and anteversion differences (R = 0.028 and R = 0.045, respectively). There were no significant differences among the BMI < 25, 25 ≦ BMI < 30, and BMI ≧ 30 groups (p value: 0.725, 0.934, respectively); between the BMI < 25 and BMI ≧ 25 groups (p value: 0.542, 0.697, respectively); and between the BMI < 30 and BMI ≧ 30 groups with regard to inclination and anteversion (p value: 0.859, 0.456, respectively). Moreover, similar findings were observed with regard to the distance between the preoperative planning and postoperative cup positioning for the transverse, anteroposterior, and craniocaudal axes of the pelvis. ConclusionWe found that the accuracy of acetabular cup placement using CT based-navigation in THA was not affected in obese patients. Therefore, THAs with a CT-based navigation system are considered useful in obese patients.

DiODe: Directional Orientation Detection of Segmented Deep Brain Stimulation Leads: A Sequential Algorithm Based on CT Imaging

Background: Directional deep brain stimulation (DBS) allows steering the stimulation in an axial direction which offers greater flexibility in programming. However, accurate anatomical visualization of the lead orientation is required for interpreting the observed stimulation effects and to guide programming. Objectives: In this study we aimed to develop and test an accurate and robust algorithm for determining the orientation of segmented electrodes based on standard postoperative CT imaging used in DBS. Methods: Orientation angles of directional leads (Cartesia^TM; Boston Scientific, Marlborough, MA, USA) were determined using CT imaging. Therefore, a sequential algorithm was developed that quantitatively compares the similarity of the observed CT artifacts with calculated artifact patterns based on the lead’s orientation marker and a geometric model of the segmented electrodes. Measurements of seven ground truth phantoms and three leads with 60 different configurations of lead implantation and orientation angles were analyzed for validation. Results: The accuracy of the determined electrode orientation angles was –0.6 ± 1.5° (range: –5.4 to 4.2°). This accuracy proved to be sufficiently high to resolve even subtle differences between individual leads. Conclusions: The presented algorithm is user independent and provides highly accurate results for the orientation of the segmented electrodes for all angular constellations that typically occur in clinical cases.

Mechanical Study of Optimal Implant Position for Maxillary Implant-Supported Overdentures Using Three-Dimensional Simulation Software.

The purpose of this study was to determine the optimal positioning of implants for maxillary implant-supported overdentures (MIODs) using finite element analysis (FEA). Three-dimensional (3D) finite element models were built incorporating the maxilla, mucous membrane, removable denture, and artificial teeth using FEA software. Four models were prepared: one without an implant; one with two implants in the region of the lateral incisor; one with two implants in the first premolar region; and one with four implants in the lateral incisor and first premolar regions. Occlusal load was applied to the model, and denture displacement and the distribution of stress in the surrounding bone and mucous membrane were observed and measured. The maximum equivalent stresses to the bone and mucous membrane were highest in the premolar and anterior areas, respectively. Stress to the bone was concentrated around the implants, whereas stress in the mucous membrane was concentrated along the posterior margin. Denture displacement in the anterior direction was highest in the model without implants, while denture displacement in the posterior direction was less affected by the presence of implants. Overall, denture displacement in the four-implant model was smaller than that in the other models. Implant angle affected the stress distribution, with highest stress to the bone when the implant was positioned in a palatal direction and highest stress to the mucous membrane when placed mesially. However, implant angle had little impact on denture displacement, with almost the same stress for implants at all tested angles. Optimal implant position can stabilize overdentures and reduce stress to the bone and mucous membrane. Stress is reduced when implants are inserted in the premolar area and when the direction of the implant is perpendicular to the occlusal plane.

Measurement System for Attitude of Anterior Pelvic Plane and Implantation of Prothesis in THR Surgery

With the average age of population increasing in the world, the number of total hip replacement (THR) surgeries increases year by year. However, the failure rate of THR surgeries is up to 10% following primary surgery and 28% after revision arthroplasty, which has direct correlation to the implantation angles between prosthesis and pelvis. To improve the implanting accuracy of the prosthesis, we propose a measurement system and estimation algorithms. The system includes three parts: an initial attitude measurement instrument, which is used to determine the initial attitude of the anterior pelvic plane (APP), a real-time attitude measurement instrument, which aims to acquire the real-time attitude of the APP, and an acetabular cup angle measurement instrument, which obtains the relative angles between prosthesis and pelvis. Each of them is based on inertial measurement unit (IMU) and magnetometer. A quaternion-based extended Kalman filter is adopted to fuse the data from IMU and magnetometer to estimate the orientation, and the algorithm calculating the attitude of pelvis and relative angles between pelvis and prosthesis is designed in this paper. The reliability of this system, from the measurement point of view, has been verified by experiments. The experimental results show that the root-mean-square errors of APP attitude and acetabular cup implanting orientation are less than 1.6° and 3° with standard uncertainty of less than 0.22° and 0.17°, respectively. The accuracy of our system meets the requirement of the THR surgeries.

Osteochondral resurfacing implantation angle is more important than implant material stiffness.

ABSTRACTOsteochondral resurfacing implants are a promising treatment for focal cartilage defects. Several implant‐factors may affect the clinical outcome of this treatment, such as the implant material stiffness and the accuracy of implant placement, known to be challenging. In general, softer implants are expected to be more accommodating for implant misalignment than stiffer implants, and motion is expected to increase effects from implant misalignment and stiffness. 3D finite element models of cartilage/cartilage contact were employed in which implantation angle (0°, 5°, 10°) and implant material stiffness (E = 5 MPa, 100 MPa, 2 GPa) were varied. A creep loading (0.6 MPa) was simulated, followed by a sliding motion. Creep loading resulted in low maximum collagen strains of 2.5% in the intact case compared to 11.7% with an empty defect. Implants mostly positively affected collagen strains, deviatoric strains, and hydrostatic pressures in the adjacent cartilage, but these effects were superior for correct alignment (0°). The main effect of implant misalignment was bulging of opposing cartilage tissue into the gap caused by the misalignment. This increased collagen strains and hydrostatic pressures. Deviatoric strains were increased adjacent to the gap. Subsequent sliding initially increased strains for a stiff, misaligned implant, but generally sliding decreased strains. In conclusion, implants can decrease the detrimental effect of defects, but correct implant alignment is crucial, more than implant material stiffness. Implant misalignment causes a gap, causing potentially damaging cartilage deformation during prolonged loading, for example, standing, even for soft implants. Mild motion may positively affect the cartilage. © 2018 The Authors. Journal of Orthopaedic Research® published by Wiley Periodicals, Inc. on behalf of Orthopaedic Research Society. J Orthop Res 36:2911–2922, 2018.

Accuracy of predicted orthogonal projection angles for valve deployment during transcatheter aortic valve replacement

BackgroundMulti-detector computed tomography (MDCT) predicted orthogonal projection angles have been introduced to guide valve deployment during transcatheter aortic valve replacement (TAVR). Our aim was to investigate the accuracy of MDCT prediction methods versus actual angiographic deployment angles. MethodsRetrospective analysis of 2 currently used MDCT methods: manual multiplanar reformations (MR) and the semiautomatic optimal angle graph (OAG). Paired analysis was used to compare the 2-dimensional distributions and means. ResultsWe included 101 patients with a mean (±SD) age of 81 ± 9 years. The MR and OAG methods were used in 46 and 55 patients, respectively. A ≥5% change from the predicted MDCT range in left anterior oblique/right anterior oblique (LAO/RAO) and the cranial/caudal (CRA/CAU) angle occurred in 42% and 58% of patients, respectively. The mean predicted versus actual deployment angles were significantly different (CRA/CAU: -2.6 ± 11.5 vs. -7.6 ± 10.7, p < 0.001; RAO/LAO 8.1 ± 10.9 vs. 9.5 ± 10.6, p = 0.048; respectively). The MR method resulted in a more accurate CRA/CAU angle (CRA/CAU: -4.6 ± 11.1 vs. -6.5 ± 11.8, p = 0.139; RAO/LAO 7.4 ± 11.2 vs. 10.4 ± 11.2, p = 0.008; respectively), whereas the use of the OAG resulted in a more accurate RAO/LAO angle (CRA/CAU: -0.9 ± 10.8 vs. -9±11.2, p < 0.001; RAO/LAO 9.05 ± 10.6 vs. 8.5 ± 9.9, p = 0.458; respectively). For the entire cohort, the 2-dimensional distributions and means of the predicted versus the actual angles were significantly different from each other (p < 0.001). We repeated our analysis using both MDCT methods and demonstrated similar results with each method. ConclusionsCurrently used MDCT methods for TAVR implantation angles are significantly modified before actual valve deployment. Thus, further refinement of these prediction methods is required.

Rod Lengthening With the Magnetically Controlled Growing Rod: Factors Influencing Rod Slippage and Reduced Gains During Distractions.

Prospective study. To identify the factors that are associated with rod slippage and to study the pattern of achieved length gain with a standard distraction methodology. Ability to achieve successful magnetically controlled growing rod (MCGR) distraction is crucial for gradual spine lengthening. Rod slippage has been described as a failure of internal magnet rotation leading to a slippage and an inability to distract the rod. However, its onset, significance, and risk factors are currently unknown. In addition, how this phenomenon pertains to actual distracted lengths is also unknown. A total of 22 patients with MCGR and at least six distraction episodes were prospectively studied. Patients with rod slippage occurring less than six distraction episodes were considered early rod slippage whereas those with more than six episodes or have yet to slip were grouped as late rod slippage. The association of parameters including body habitus, maturity status, age of implantation, total number of distractions, months of distraction from initial implantation, initial and postoperative Cobb angle, T1-T12, T1-S1, T5-T12 kyphosis, curve flexibility, instrumented length, and distance between magnets in dual rods and between the magnets and apex of the curve with early or late onset of rod slippage were studied. Differences between expected and achieved distraction lengths were assessed with reference to rod slippage episodes and rod exchanges to determine any patterns of diminishing returns. Patients had mean age of 7.1 years at diagnosis with mean follow-up of 49.8 months. A mean 32.4 distractions were performed per patient. Early rod slippage occurred in 14 patients and late rod slippage occurred in eight patients. Increased height, weight, body mass index, older age, increased T1-12 and T1-S1 lengths, and less distance between magnets were significantly associated with early rod slippage. Expected distraction lengths did not translate to achieve distraction lengths and reduced gains were only observed after achieving one-third of the allowable distracted length in the MCGR. Length gains return to baseline after rod exchange. This is the first study to specifically analyze the impact of rod slippage on distraction lengths and the risk factors associated with its onset and frequency. Increased body habitus and reduced distance between internal magnets significantly influenced rod slippage events. Diminishing returns in distracted length gains were only observed after a period of usage. 3.

Improving patient safety during introduction of novel medical devices through cumulative summation analysis.

OBJECTIVE The aim of this study was to implement cumulative summation (CUSUM) analysis as an early-warning detection and quality assurance system for preclinical testing of the iSYS1 novel robotic trajectory guidance system. METHODS Anatomically accurate 3D-printed skull phantoms were created for 3 patients who underwent implantation of 21 stereoelectroencephalography electrodes by surgeons using the current standard of care (frameless technique). Implantation schema were recreated using the iSYS1 system, and paired accuracy measures were compared with the previous frameless implantations. Entry point, target point, and implantation angle accuracy were measured on postimplantation CT scans. CUSUM analysis was undertaken prospectively. RESULTS The iSYS1 trajectory guidance system significantly improved electrode entry point accuracies from 1.90 ± 0.96 mm (mean ± SD) to 0.76 ± 0.57 mm (mean ± SD) without increasing implantation risk. CUSUM analysis was successful as a continuous measure of surgical performance and acted as an early-warning detection system. The surgical learning curve, although minimal, showed improvement after insertion of the eighth electrode. CONCLUSIONS The iSYS1 trajectory guidance system did not show any increased risk during phantom preclinical testing when used by neurosurgeons who had no experience with its use. CUSUM analysis is a simple technique that can be applied to all stages of the IDEAL (idea, development, exploration, assessment) framework as an extra patient safety mechanism. Further clinical trials are required to prove the efficacy of the device.

A new species of Xotodon (Notoungulata, Toxodontidae) from northwestern Argentina

ABSTRACTXotodon caravela, a new species of toxodontid from northwestern Argentina, is presented. The material studied consists of a well-preserved and nearly complete mandible and a maxillary fragment, recovered in the Aconquija Formation (late Miocene-early Pliocene) at the El Molino locality (Tucumán Province, Argentina). The fossil diversity of the levels is concordant with an early Pliocene fauna. The general features of the dentition and mandible (e.g., concave ectoloph and single lingual fold on upper molars, anterior fold mesially displaced relative to the hypoflexid in the lower molars, sigmoid lateral outline of chin, and continuous enamel on M3) allow the inclusion of this specimen in the genus Xotodon. In turn, some traits indicate unequivocally that this is a new species, such as the anterior region without constriction at the premolar level, the approximately 13° angle of implantation of the i3 in relation to the ventral edge of the mandibular body (without lateral divergence), and the presence of an intra-alveolar projection of the incisive crown extending laterally below the premolars to the level of the p4 and forming a robust projection or lateral ledge. The new taxon was included in a matrix of 59 characters and compared with 32 notoungulate genera. The phylogenetic position and comparative analysis support the taxonomic interpretation of the studied specimen as a new species of Xotodon. This represents the first record of a toxodontid in the Neogene lowlands of northwestern Argentina and contributes to our knowledge of this family in the region.Citation for this article: Armella, M. A., D. A. García-López, and L. Dominguez. 2018. A new species of Xotodon (Notoungulata, Toxodontidae) from northwestern Argentina. Journal of Vertebrate Paleontology. DOI: 10.1080/02724634.2017.1425882.

Controlling room temperature ferromagnetism and band gap in ZnO nanostructured thin films by varying angle of implantation.

The defects in the host lattice play a major role in tuning the surface roughness, optical band gap and the room temperature ferromagnetism (RTFM) of ZnO thin films. Herein, we report a novel approach to tailor the band gap and RTFM of a ZnO nanostructure by varying the angle of implantation of 60 keV N ions keeping the ion fluence of 1 × 1016 ions per cm2 and the beam size of 3 mm constant. The implantation was performed by changing the thin films' orientations at 30°, 60° and 90° with respect to the incident beams. Remarkably, an enhancement of ∼6 times in RTFM, tuning in band gap from 3.27 to 3.21 eV and ∼60% reduction in surface roughness were noticed when the ion implantation was done at 60° to the normal. This novel technique may be suitable for tuning the physical properties of nanostructures for their application in the spintronics, semiconductor and solar cell industries.

Control of polysilicon nanowires conductivity by angle-dependent ion implantation

Boron doped polysilicon nanowire devices were fabricated using lithography-based top-down method. The devices, implanted by boron ions at different angles (0°,20°,30°,45°), exhibited significant dependence of electrical conductivity on incident implantation angle. Monte Carlo simulations of the dopant distribution, show that the projected range of boron implant increase with decreasing incident angle, in agreement with literature SRIM (Stopping and Range of Ion in Matter) reported data. The simulations and electrical measurements, show that geometrical shadowing reduce the device conductivity, while lower incident implantation angles increase it. This implies that Polysilicon Nanowires conductivity can be controlled by changing the implant angle, and this is beneficial for ‘top=down’ fabrication of SiNW sensors based on accumulation and depletion.

Digital Assessment of the Implantation Angle of Proximal Femoral Nail Antirotation Helical Blade Using CT Three-dimensional Reconstruction

ABSTRACTObjectives: To facilitate simple and safe manipulation during proximal femoral nail antirotation (PFNA) operation, we studied the range of safe implantation angle of the helical blade of the PFNA system by using a digital-based three-dimensional reconstruction model of CT images. Methods: Thirty-five healthy volunteers were recruited. Original multilayer helical CT scan data of the left femur were collected and imported into Mimics software. Anatomic features of the femur, including the safe implantation angle, anterior and posterior angle, were measured. Differences in each angle between male and female subjects were compared using Student's t test, and the determinants of each angle were analyzed by linear regression. Results: The mean safe implantation angle was 30.09° ± 4.73°, the mean anterior angle was 15.82° ± 2.07°, and the mean posterior angle was 14.27° ± 3.19°. All the three angles were greater in males than females (P < 0.05). Neck shaft angle and the diameter of the femoral neck and head were linearly correlated with the safe implantation angle, the anterior and posterior angle, respectively. Femoral neck diameter was a significant determinant of the safe implantation angle and posterior angle, respectively. Moreover, femoral neck diameter and femoral head diameter were significant determinants of the anterior angle. Conclusions: The study has introduced and delineated a novel parameter, the safe implantation angle, for FPNA surgery, which may help orthopedic surgeons in deciding a safe range of PFNA operation and improve the accuracy of PFNA helical blade implantation.

Factors Affecting Stereotactic Accuracy in Image-Guided Deep Brain Stimulator Electrode Placement

Background/Aims: Intraoperative imaging allows near-real-time assessment of stereotactic accuracy during implantation of deep brain stimulation (DBS) electrodes. Such technology can be used to examine factors impacting stereotactic error. Methods: Intraoperative CT imaging was reviewed in patients undergoing DBS placement at Oregon Health and Sciences University. Coordinates of the target electrode were compared to the operative plan to characterize the magnitude and direction of stereotactic error with respect to side of implantation, target, and electrode approach angles. Results: One hundred sixty-nine leads in 94 patients were examined. Targets were GPi (n = 86), STN (n = 31), and Vim (n = 52). The average Euclidean error was 1.63 mm (SD 0.87). The error magnitude was higher for Vim (1.95 mm) than for GPi (1.44 mm), while STN (1.65 mm) did not differ from either Vim or GPi (ANOVA: F = 6.15, p = 0.003). Electrodes targeting Vim and STN were significantly more likely to deviate medially compared to those targeting GPi (ANOVA: F = 9.13, p < 0.001). The coronal approach angle affected the error when targeting Vim (ρ = 0.338, p = 0.01). These findings were confirmed during multivariate analyses. Conclusions: This study shows a significant effect of target on the accuracy of electrode placement for DBS. Targeting Vim results in a greater Euclidean error and a greater medial deviation off target. These systematic deviations should be taken into account during electrode implantation.

Investigations on mechanical and electrical properties of N+ ions implanted TiN thin films

In the present work, we have grown titanium (Ti) thin films using DC sputtering system in argon atmosphere. Ti films are implanted using low energy ion beam(having 70 keV energy) at a fluence of 2 × 1016 ions cm−2 by varying the implantation angles from 15° to 45°. TiN films were then characterized for their structural, mechanical, optical and electrical properties. XRD measurements show an enhancement in the (1 1 1) peak with increase in implantation angle indicating the improvement in the crystallinity due to deeper implantation of N ions in host lattice. Also, a small shift in this peak towards higher angle side is noticed with the implantation angle which confirms that strain is modified depending upon the implantation angle. The change in the strain value in turn is responsible for the variation in various physical properties. UV–Vis measurements show decrease in optical band gap (from 2.41 eV to 2.39 eV) while improvement in electrical conductivity with implantation angle. Furthermore, increase in implantation angle leads to enhancement in mechanical hardness of the TiN thin films from pristine 3.0 GPa–19.6 GPa for 30° angle.