External Reference Frame Research Articles

Contribution of external reference frame to tactile localization.

The purpose of the present study was to elucidate whether an external reference frame contributes to tactile localization in blindfolded healthy humans. In a session, the right forearm was passively moved until the elbow finally reached to the target angle, and participants reached the left index finger to the right middle fingertip. The locus of the right middle fingertip indicated by the participants deviated in the direction of the elbow extension when vibration was provided to the biceps brachii muscle during the passive movement. This finding indicates that proprioception contributes to the identification of the spatial coordinate of the specific body part in an external reference frame. In another session, the tactile stimulus was provided to the dorsal of the right hand during the passive movement, and the participants reached the left index finger to the spatial locus at which the tactile stimulus was provided. Vibration to the biceps brachii muscle did not change the perceived locus of the tactile stimulus indicated by the left index finger. This finding indicates that an external reference frame does not contribute to tactile localization during the passive movement. Humans may estimate the spatial coordinate of the tactile stimulus based on the time between the movement onset and the time at which the tactile stimulus is provided.

Structured residual sparsity for video compressive sensing reconstruction

Recent advancements in the residual sparsity strategy have garnered widespread attention in video compressive sensing (CS) reconstruction. However, most of the existing residual sparsity-based video CS reconstruction methods usually suffer from some limitations that lead to undesired visual artifacts. Firstly, these methods only rely on a patch sparsity scheme that is limited by their focus on the local structures of each video frame, neglecting the nonlocal self-similarity (NSS) property inherent to each video frame. Secondly, these methods concentrate on utilizing the NSS property of external reference frames for multi-hypothesis (MH) prediction while disregarding the internal NSS property of the current frame. In this paper, we propose a new structured residual sparsity (SRS) approach for video CS reconstruction, which jointly exploits the NSS properties of the current frame and its reference frames. Specifically, due to the unavailability of the original video frames, we first devise an effective intraframe CS (EICS) reconstruction method that leverages the internal NSS property of each frame. This approach enables us to obtain initial recovery frames, which then facilitate the execution of MH prediction. Following this, we generate a residual frame for the current frame by employing the MH prediction. Then, we propose a novel SRS model jointly using the NSS properties of the current frame and its reference frames to explore both the correlations of intraframe and interframe for reconstructing the current frame. Furthermore, for the sake of optimization feasibility, we develop an effective alternating direction method of multipliers (ADMM) algorithm to address the objective. Our experimental findings reveal that the proposed SRS not only yields superior quantitative results, but also uncovers finer details and causes fewer visual artifacts compared to many popular or state-of-the-art video CS reconstruction approaches.

The Motion-Silencing Illusion Depends on Object-Centered Representation.

Motion silencing is a striking and unexplained visual illusion wherein changes that are otherwise salient become difficult to perceive when the changing elements also move. We develop a new method for quantifying illusion strength (Experiments 1a and 1b), and we demonstrate a privileged role for rotational motion on illusion strength compared with highly controlled stimuli that lack rotation (Experiments 2a to 3b). These contrasts make it difficult to explain the illusion in terms of lower-level detection limits. Instead, we explain the illusion as a failure to attribute changes to locations. Rotation exacerbates the illusion because its perception relies upon structured object representations. This aggravates the difficulty of attributing changes by demanding that locations are referenced relative to both an object-internal frame and an external frame. Two final experiments (4a and 4b) add support to this account by employing a synchronously rotating external frame of reference that diminishes otherwise strong motion silencing. All participants were Johns Hopkins University undergraduates.

Superposed transpressional tectonics of an intraterrane shear zone resulted in Shillong plateau evolution, NE India

The analysis of shear zone kinematics plays a crucial role in understanding the tectonics at micro-, meso-, and regional scales within a given terrane. This study focuses on investigating the kinematics of prominent asymmetric structural features preserved within the Barapani Shear Zone (BSZ). These features are utilized to establish vorticity numbers in relation to the reference frames of the BSZ. Typically, shear zones provide finite values for kinematics and vorticity numbers. The BSZ is identified as an intraterrane, multiply deformed shear zone within the Shillong Plateau, which exhibits varying kinematics and vorticity numbers measured across different deformation zones.The research reveals that the BSZ underwent successive D1, D2, D3, and D4 events, resulting in preserved S1, S2, and S3 planar fabrics, with D4 evidenced by brittle deformation features. However, determining shear zone kinematics purely based on the orientation of these planar fabrics and mineral lineation with respect to the external reference frame is insufficient. Consequently, this study calculates vorticity numbers and kinematics by considering both the external and internal reference frames of the BSZ. The study suggests that superposed transpressional tectonics prevailed during D2 and D3 events.

A novel method for the remote measurement of trismus in clinical trials using mobile phone cameras

ObjectiveTo evaluate the reliability and validity of a novel method for remotely measuring trismus.Materials and methodsWe recruited 60 volunteers who took three types of photographs at a fixed restricted jaw position mimicking limited mouth opening, including one selfie and one portrait with or without a reference frame. Additionally, the interincisal distance and the width of the upper central incisors were measured with a ruler, as per common practice. Measurements of trismus were made using image analysis software comparing different types of photos and calibration methods. Intraclass correlation coefficient (ICC) and 95% limits of agreement (LoA) with 95% confidence interval were calculated to evaluate reliability and validity.ResultsThe proposed method demonstrated high reliability (ICC 0.998; 95% CI 0.997, 0.999). Calibration of photographs using at least a baseline photograph with an external reference frame yielded unbiased measurements and minimised variability. The use of selfies compared to portrait photos also increased variability.ConclusionThe measurement of trismus can be performed using images taken remotely by patients using their mobile phone cameras. The proposed method is highly accurate, with best results obtained by using a reference frame for calibration of portrait photographs.Clinical relevanceWe propose an easy, cheap, and accurate method that allows for remote and frequent monitoring of trismus in clinical studies using patients’ mobile phones.

Temporal and spatial reference frames in visual working memory are defined by ordinal and relational properties.

Natural environments provide a rich spatiotemporal context that allows for visual objects to be differentiated based on different types of information: their absolute or relative spatial or temporal coordinates, or their ordinal positions in a spatial or temporal sequence. Here, we investigated which spatial and temporal properties are incidentally encoded along with to-be-remembered features to provide reference frames in visual working memory (VWM). We tested the different possibilities in a spatiotemporal color change-detection task by transforming spatial and/or temporal structures of item presentation at retrieval relative to encoding. More precisely, spatial and/or temporal coordinates were (a) switched, changing the order of items in a spatial or temporal sequence (ordinal transformation); (b) multiplied by different factors, changing interitem distances (relational transformation); or (c) multiplied by a constant factor, expanding or shrinking the entire configuration (global transformation). Such transformations of the external reference frame at retrieval should only interfere with VWM if the internal reference frame relies on the spatial or temporal properties affected by the respective transformation. We found that ordinal and relational transformations of either the spatial or temporal structure impaired performance, whereas global transformations did not. Thus, reference frames appear to be primarily defined by interitem relations-including relative distances between items as well as their order-rather than absolute positions in space or time. These results corroborate and extend previous findings for the spatial domain, and highlight functional similarities of the spatial and temporal dimensions in VWM by revealing the same metrical properties for temporal reference frames. (PsycInfo Database Record (c) 2022 APA, all rights reserved).

A syntactic analysis of a complex motor action: the octopus arm ‘slap’

The analysis of a natural motor action is always difficult, especially when different motor programs are combined within the same interaction with the environment. We analyzed the behavior of an octopus, Abdopus sp., filmed in tidal pools in Okinawa, Japan, which used the kinematic primitives of rotation and translation of its hydrostatic arms, and combined these kinematic behaviors serially and in parallel to ‘slap’ at fish in the wild. In total, 19 slaps were analyzed. The kinematics of arm movement were measured in both external and animal-centered reference frames, while the octopus was slapping at the fish. By combining these primitives, the octopus is able to maintain flexibility while controlling only a few degrees of freedom, a concept we term ‘flexible rigidity’. This slapping action supports Flash and Hochner’s embodied organization view of motor behavior, as well as their idea that motor primitives can combine syntactically to form a complex action. The octopus’s ability to use sensory feedback from the position of a moving fish target, along with the feed-forward motor primitives, allows for the building of complex actions at dynamic equilibrium with the environment. Over all, these findings lead to a more realistic view of how a complex behavior allows an animal to coordinate with its environment.

Energy cost of localization of relational quantum information

Entanglement of spatially separated quantum states is usually defined with respect to a reference frame provided by some external observer. Thus, if one wishes to localize the quantum information within a spatially separated entangled state, one must enact an entanglement extraction protocol also defined with respect to that external frame. Entanglement extraction for Gaussian ground states in such an external frame construction has been shown to require a minimum energy and is hence an interesting process for gravitational physics, where examinations of localization vs energy cost have a long history. General covariance, however, precludes dependence on external frames. In order to enact an extraction protocol in a generally covariant theory, dependence on the external reference frame must first be removed and the states made relational. We examine the implementation of an extraction protocol for Gaussian states, whose center of mass and relational degrees of freedom are entangled, in a relational toy model where translation invariance stands in for full diffeomorphism invariance. Constructing fully relational states and the corresponding extraction/localization can, in principle, be done in two ways. External frame position information can be removed through $G$-twirling over translations or one can spontaneously break the translation symmetry via the gradient of an auxiliary field, or $Z$-model. We determine the energetics of quantum information localization after the states have been made fully relational via both the $G$-twirl and $Z$-model. We also show one can obtain the $G$-twirl construction from a $Z$-model as a limit of positive operator valued measurements.

Visual-Spatial Skills, Strategies, and Challenges to Extract, Represent, and Predict Stereochemical Outcomes of Cycloadditions Using a Hexagonal Prism Reference Frame

The perception of 3D features from 2D representations depend on their number of salient features, recognizable canonical axes, and orientations. Informed by form-perception literature, we proposed a hexagonal prism as an external reference frame to identify positions of elements in relation to each other and the observer when studying Diels–Alder and other cycloaddition reactions. The hexagonal prism reference model (HPRM) provides three-dimensional features to cycloaddition transition states and an external reference to facilitate analysis of their stereochemical characteristics. A study to characterize the visual-spatial skills (VSS) and spatial challenges associated with extracting spatial information, representing spatial relations, and predicting stereochemical outcomes was completed with six graduate and six undergraduate students. Our findings show that different VSS predominate when solving different spatial tasks and that the patterns of VSS utilized by both graduate and undergraduates groups can be used to provide a more in-depth subcategorization of spatial strategies. The HPRM not only provides a resource for students to practice VSS and learn cycloaddition stereoselectivity, but also for instructors to promote effective strategies to predict stereochemistry. Since this study did not identify any nonspatial strategy, the HPRM proved to be effective in promoting students’ visuospatial thinking to solve spatial tasks.

Non-Violations in Bell's Inequality

Intuitively, violations of Bell's inequality make no sense because one cannot violate a mathematical relationship unless it is wrong, or has been misused. However, the rotating polarizer experiment has been argued to provide such violations, and it is asserted this requires non-locality. It is shown here that at least one form of the inequality is violated because the results violate a condition used in deriving the inequality. The problem arises from mixed frames of reference being utilized, and if an external reference frame is employed, such as a polarized source, the inequality should be complied with. This could be verified by experiment. It is also important to resolve this as entanglement is to be potentially involved equipment such as quantum computing. Correct understanding may assist in such design.

Full-field input generated from right visual field information for healthy participants reproduces performance simulating left unilateral spatial neglect in line bisection.

Patients with left unilateral spatial neglect (USN) typically place the subjective midpoint to the right of the objective centre when bisecting a horizontal line. This pathological phenomenon may be explained as a result of greater dependence on the right endpoint in the external reference frame (Koyama et al., Brain Cogn, 35, 1997, 271; McIntosh et al., Cogn Brain Res, 25, 2005, 833). Ishiai et al. (Brain, 112, 1989, 1485) reported that once patients with USN fixated on a certain point on the right part of the presented line, they persisted with this point and marked the subjective midpoint there without leftward searches. Ishiai et al.'s interpretation was that the patients saw a totalised line representation that extended equidistantly to the right and left sides, based on the information of the attended rightward extent from the subjective midpoint. Accordingly, we used virtual reality goggles (VRG) and devised a mirror-image viewing (MV) condition that showed a full-field view based on the right visual field information to test whether healthy participants would thereby show neglect-like bisection performance. The participants were 30 healthy adults (22-37 years old; 15 women and 15 men). In this condition, 96.7% (29/30) of participants were judged to exhibit USN-like performance of line bisection, indicating the effectiveness of MV condition to simulate USN. The novelty of the present study lies in the use of a task-specific intervention of neglect-like visuospatial processing during line bisection without attempting to modify the direction of spatial attention. This approach may contribute to the understanding of the pathological visuospatial processing of USN.

A direct numerical simulation display of the rotational frame preference of turbulence

An elementary observation of a laminar cylindrical Poiseuille–Couette flow profile reveals no distinction in the parabolic streamwise profile, from one without a cross-stream flow, in whatever reference frame the observation is made. This is because the laminar flow is in solid-body rotation and there is no fluid intrinsic rotation. Hence, the main streamwise Poiseuille flow is unaffected. On the contrary, in turbulent (unsteady) cylindrical axial-Couette flow, the rotational reference frame must be considered, and any observation from an external inertial reference frame can give outright incorrect results. However, even in axial turbulent pipe flow with axial rotation, the resultant effect of azimuthal velocity on the flow profile is still usually too low. Hence, the importance of consideration in the rotational frame is often overlooked. A common misconception in the study of fluid mechanics is that the position of the observer does not matter. In this direct numerical simulation study, firstly turbulent flow in a pipe with axial rotation is established. Then turbulent flow in the concentric pipe, with inner wall rotation, is used to show how tilted wall streak direction is oriented by the rotational reference frame and not the inertial reference frame.

Skin stretch modulates tactile distance perception without central correction mechanisms.

Tactile distance perception is influenced by stimulus orientation. On the hands or face, effects of orientation may originate from the mostly oval shape of receptive fields (RF) of which the long axis aligns with the proximodistal body axis. As tactile distance estimation relies on the number of RFs between stimuli, their alignment leads to a distortion of perception with distances being perceived as shorter in the proximodistal than the mediolateral body axis. It is however unknown, how physical manipulations such as skin stretch affect distance perception. Participants judged which of two distances aligned with the mediolateral or proximodistal axis on their dorsal dominant hand felt larger in two conditions: without physical manipulation and with proximodistal skin stretch. Distances were perceived shorter in proximodistal direction in both the nonstretch and the stretch condition, which was significantly pronounced in the stretch condition. Skin stretch led to perception of tactile distances as smaller, possibly related to the removal of afferent nerve endings and corresponding somatosensory RFs in the same external reference frame between the two touches. Though skin stretch is represented centrally, our results likely show that no correctional top-down mechanism corrects for skin stretch when estimating tactile distances. (PsycInfo Database Record (c) 2023 APA, all rights reserved).

A dinâmica do autoconceito da fala de um aluno de EFL: percepções a partir de experiências auto-relatadas e dados de observação em sala de aula

Abstract: This case study explores the dynamics of the English as a Foreign Language (EFL) speaking self-concept of a female university student. The study focuses on the participant’s internal and external frames of reference ( MERCER, 2011b) to analyze how her EFL speaking self-concept has been constructed throughout her years of English language instruction, and how it is re-constructed and developed in the current course. Findings show that such self-concept originates from beliefs systems, emotions, learner characteristics, previous English language learning context/method, critical experiences and experiences of success/failure using the oral language. Results indicate that critical positive experiences and perceived experiences of success appear to influence positively the learner’s self-efficacy beliefs and emotional experiences about the oral task.

Superimposed structures, incremental strain and deformation path from field data to modelling: A case study from the Alpi Apuane metamorphic core complex (NW Tuscany, Italy).

In this study, superimposed folds and antitaxial strain fringes are investigated to unravel the deformation path of the core zones of the Alpi Apuane metamorphic complex (northwest Tuscany Italy). Detailed field mapping combined with microstructural analyses is used together with computer-modelling of a complex strain fringe system to disclose the main steps of the Alpi Apuane syn-metamorphic deformation history. A comparison between natural investigated fibres and those produced by paraffine wax experiments provides details of the relative core-object-fringe rotation allowing new insight on the growth kinematics of strain fringes. The results of our analyses show that our composite fringe system is characterized by a first set of fibres to be related with the main composite axial planar foliation of regional scale isoclinal non-cylindric folds. This first set of fibre fringes records a local non-coaxial strain with an absolute core-object rotation (relative to an external reference frame represented by the main foliation) of 140° and a calculated shear strain (γ) of about 4. The second set of fringes, developed after the tilting of the main foliation and the first fringe-set in a sub-vertical orientation, records a lower absolute rotation of the core-object (25°), a lower shear strain (γ) of about 1.4 and a coaxial strain associated with the vertical shortening. This part of the composite fringe system and the related structures may relate to the switch from the crustal scale contractional regime to the extensional one, which characterized the development of the inner northern Apennines orogen.

Self-concept of EFL preservice teachers as reflected in their teaching performance

A number of studies discussing the significant role of self-concept in the educational field are evident. However, research investigating the self-concept of English as a Foreign Language (EFL) preservice teachers and how the self-concept is reflected in the teaching performance is limited. Thus, this study was aimed at investigating the portrait of the self-concept of English preservice teachers in the Indonesian context and how the self-concept is reflected in their teaching performance. A qualitative research paradigm, especially an explanatory case study design was employed to figure them out. The study found that first, diverse portraits of self-concept i.e. highly positive, moderate, and low or negative self-concept were captured in the participants’ academic self-concept (pedagogic and professional self-concept) with the inclination of higher portrayal in the non-academic sub-aspects of self-concept (social and emotional self-concept). Second, the congruent and incongruent reflection of self-concept were identified. The findings imply that academic aspects of self-concept (pedagogic and professional competence) seem to be contributing factors to the participants’ negative self-perception of their self-concept. Moreover, reflexivity, internal and external frames of reference, and emotion regulation strategies seem to be contributing factors to the construction of the participants’ self-concept. This study concludes that the construction of the participants’ self-concept dynamic during the practicum and its manifestation in the teaching performance is affected by internal and external factors.

Remote Data Collection During a Pandemic: A New Approach for Assessing and Coding Multisensory Attention Skills in Infants and Young Children.

In early 2020, in-person data collection dramatically slowed or was completely halted across the world as many labs were forced to close due to the COVID-19 pandemic. Developmental researchers who assess looking time (especially those who rely heavily on in-lab eye-tracking or live coding techniques) were forced to re-think their methods of data collection. While a variety of remote or online platforms are available for gathering behavioral data outside of the typical lab setting, few are specifically designed for collecting and processing looking time data in infants and young children. To address these challenges, our lab developed several novel approaches for continuing data collection and coding for a remotely administered audiovisual looking time protocol. First, we detail a comprehensive approach for successfully administering the Multisensory Attention Assessment Protocol (MAAP), developed by our lab to assess multisensory attention skills (MASks; duration of looking, speed of shifting/disengaging, accuracy of audiovisual matching). The MAAP is administered from a distance (remotely) by using Zoom, Gorilla Experiment Builder, an internet connection, and a home computer. This new data collection approach has the advantage that participants can be tested in their homes. We discuss challenges and successes in implementing our approach for remote testing and data collection during an ongoing longitudinal project. Second, we detail an approach for estimating gaze direction and duration collected remotely from webcam recordings using a post processing toolkit (OpenFace) and demonstrate its effectiveness and precision. However, because OpenFace derives gaze estimates without translating them to an external frame of reference (i.e., the participant's screen), we developed a machine learning (ML) approach to overcome this limitation. Thus, third, we trained a ML algorithm [(artificial neural network (ANN)] to classify gaze estimates from OpenFace with respect to areas of interest (AOI) on the participant's screen (i.e., left, right, and center). We then demonstrate reliability between this approach and traditional coding approaches (e.g., coding gaze live). The combination of OpenFace and ML will provide a method to automate the coding of looking time for data collected remotely. Finally, we outline a series of best practices for developmental researchers conducting remote data collection for looking time studies.

Target-free calibration of flat refractive imaging systems using two-view geometry

Imaging through refractive media is challenged by the alteration of light trajectory from their linear path, thus incurring severe distortions. These distortions are depth-dependent, non-linear, and, more importantly, alter the standard single viewpoint geometry into an axial form. Though modeling such imaging systems has been studied in the past, an in-depth analysis of their two-view geometry is still lacking. We demonstrate in this paper that the value of such form is not limited to the estimation of the relative motion as it allows to calibrate the system independent of any scene knowledge. Therefore, we relieve the establishment of external reference frames and estimate the system parameters through the course of the mission and on-the-fly. In our development, we identify relations among the parameters that allow us to separate them into two orthogonal groups. Using these relations we calibrate the system and solve the pose components. Only a minimal set of five corresponding points is needed for that purpose. We also show that while existing solutions constrain subsets of the parameters or apply hardware installations, our model requires no additional information, still estimating all parameters simultaneously and directly. In the paper, the formulation of two common imaging setups are developed, the first is of a single camera acquiring data through motion, and the other is of a stereo-rig, where the relative pose is fixed but where the system model is more involved. Numerical and experimental results demonstrate that the proposed calibration model exhibits stability to the presence of high levels of noise and achieves high levels of accuracy. Furthermore, we demonstrate how our modeling improves the accuracy by an order of magnitude or more compared to the state-of-the-art.

Imagine Your Crossed Hands as Uncrossed: Visual Imagery Impacts the Crossed-Hands Deficit.

Successful interaction with our environment requires accurate tactile localization. Although we seem to localize tactile stimuli effortlessly, the processes underlying this ability are complex. This is evidenced by the crossed-hands deficit, in which tactile localization performance suffers when the hands are crossed. The deficit results from the conflict between an internal reference frame, based in somatotopic coordinates, and an external reference frame, based in external spatial coordinates. Previous evidence in favour of the integration model employed manipulations to the external reference frame (e.g., blindfolding participants), which reduced the deficit by reducing conflict between the two reference frames. The present study extends this finding by asking blindfolded participants to visually imagine their crossed arms as uncrossed. This imagery manipulation further decreased the magnitude of the crossed-hands deficit by bringing information in the two reference frames into alignment. This imagery manipulation differentially affected males and females, which was consistent with the previously observed sex difference in this effect: females tend to show a larger crossed-hands deficit than males and females were more impacted by the imagery manipulation. Results are discussed in terms of the integration model of the crossed-hands deficit.

148. Sacroiliac joint fusion navigation: how accurate is pin placement?

BACKGROUND CONTEXT Percutaneous pin placement is used in a variety of orthopedic surgery settings. These include, but are not limited to, external fixator placement, fracture fixation, and reference frame application for navigation. Although pin placement typically is uncomplicated, it can become more difficult with the need for obliquely angled pins and the potential for the pin to slip off the bone. For spine and pelvic cases with intraoperative navigation, often a standard reference frame is placed using a percutaneous pin. The goal is for this pin to be placed into the posterior ilium, which is an oblique surface. Proper placement of this pin helps to ensure the correct placement of the sacroiliac joint (SIJ) fusion implants. To date, there is no literature specifically examining the accuracy of pin placement. PURPOSE The purpose of our study was to evaluate the occurrence of ideal percutaneous pin placement into the iliac wing during navigated SIJ fusion surgery. STUDY DESIGN/SETTING IRB approved retrospective chart review study completed at an academic medical institution. PATIENT SAMPLE Patients who underwent navigated SIJ fusion by the senior author between 10/2013 and 1/2020. OUTCOME MEASURES Pin placement accuracy graded in concordance with a scheme developed and tested by the authors. METHODS Following IRB approval, we reviewed the charts and intraoperative CT imaging of patients who underwent navigated SIJ fusion by the senior author between 10/2013 and 1/2020. A pin placement grading scheme was developed initially and tested. The definition of ‘ideal’ placement was a concept developed by the authors. A modification was made and found to be acceptable to attending surgeons. This was then used for two rounds of grading. Six attending surgeons completed two rounds of pin placement grading. RESULTS Of the 95 eligible patients, 54.7% had ‘ideal’ pin placement. There were no observed complications from pin placement. There was no relationship between BMI and ideal placement. Male patients were 3.6 times more likely to have ideal placement than females. Additionally, patients undergoing right-sided fusion were 2.9 times more likely to have ideal placement than those with left-sided fusion. Interobserver reliability was rated as 0.48 and 0.47 in the first and second rounds defined as ‘moderate agreement.’ The measured intraobserver reliability ranged from 0.62 to 0.74 defined as ‘substantial agreement.’ Conclusions This study shows that even in the hands of an experienced surgeon, nonideal pin placement occurs 45.3% of the time. However, engagement of the lateral or medial cortex may make the pin more rigid. Though pin placement does not meet our preconceived ‘ideal’, it is only rarely a true ‘miss’ where it is placed into the sacrum. Male patients and patients undergoing right-sided fusion were more likely to have ‘ideal’ pin placement. When placing percutaneous pins, regardless of the location, it is important to be aware of factors that can decrease the accuracy of pin placement. FDA DEVICE/DRUG STATUS This abstract does not discuss or include any applicable devices or drugs.