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Journal articles on the topic 'Lever-arm offset'
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Chen, Guanxu, Yang Liu, Yanxiong Liu, Ziwen Tian, Jingnan Liu, and Menghao Li. "Adjustment of Transceiver Lever Arm Offset and Sound Speed Bias for GNSS-Acoustic Positioning." Remote Sensing 11, no. 13 (July 5, 2019): 1606. http://dx.doi.org/10.3390/rs11131606.
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Global Navigation Satellite System––Acoustic (GNSS-A) positioning is the main technique for seafloor geodetic positioning. A transceiver lever arm offset and sound velocity bias in seawater are the main systematic errors of the GNSS-A positioning technique. Based on data from a sea trial in shallow water, this paper studies the functional model of GNSS-A positioning. The impact of the two systematic errors on seafloor positioning is analysed and corresponding processing methods are proposed. The results show that the offset in the lever arm measurement should be parameterised in the observation equation. Given the high correlation between the vertical lever arm offset and the vertical coordinate of the seafloor station, a sample search method was introduced to fix the vertical offset correction. If the calibration of the sound velocity profiler cannot be ensured, the correction parameter of the sound velocity bias should be solved. According to the refined functional model and corrections, the position of a seafloor station in shallow water can be determined with a precision of better than 1 cm.
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Bjørdal, Filip, and Kristian Bjørgul. "The role of femoral offset and abductor lever arm in total hip arthroplasty." Journal of Orthopaedics and Traumatology 16, no. 4 (June 12, 2015): 325–30. http://dx.doi.org/10.1007/s10195-015-0358-7.
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Sakai, Takashi, Nobuhiko Sugano, Kenji Ohzono, Takashi Nishii, Keiji Haraguchi, and Hideki Yoshikawa. "Femoral anteversion, femoral offset, and abductor lever arm after total hip arthroplasty using a modular femoral neck system." Journal of Orthopaedic Science 7, no. 1 (January 2002): 62–67. http://dx.doi.org/10.1007/s776-002-8418-7.
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Daakir, M., M. Pierrot-Deseilligny, P. Bosser, F. Pichard, C. Thom, and Y. Rabot. "STUDY OF LEVER-ARM EFFECT USING EMBEDDED PHOTOGRAMMETRY AND ON-BOARD GPS RECEIVER ON UAV FOR METROLOGICAL MAPPING PURPOSE AND PROPOSAL OF A FREE GROUND MEASUREMENTS CALIBRATION PROCEDURE." ISPRS - International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences XL-3/W4 (March 17, 2016): 65–70. http://dx.doi.org/10.5194/isprs-archives-xl-3-w4-65-2016.
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Nowadays, Unmanned Aerial Vehicle (UAV) on-board photogrammetry knows a significant growth due to the democratization of using drones in the civilian sector. Also, due to changes in regulations laws governing the rules of inclusion of a UAV in the airspace which become suitable for the development of professional activities. Fields of application of photogrammetry are diverse, for instance: architecture, geology, archaeology, mapping, industrial metrology, etc. Our research concerns the latter area. <i>Vinci-Construction- Terrassement</i> is a private company specialized in public earthworks that uses UAVs for metrology applications. This article deals with maximum accuracy one can achieve with a coupled camera and GPS receiver system for direct-georeferencing of Digital Surface Models (DSMs) without relying on Ground Control Points (GCPs) measurements. This article focuses specially on the lever-arm calibration part. This proposed calibration method is based on two steps: a first step involves the proper calibration for each sensor, i.e. to determine the position of the optical center of the camera and the GPS antenna phase center in a local coordinate system relative to the sensor. A second step concerns a 3<i>d</i> modeling of the UAV with embedded sensors through a photogrammetric acquisition. Processing this acquisition allows to determine the value of the lever-arm offset without using GCPs.
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Daakir, M., M. Pierrot-Deseilligny, P. Bosser, F. Pichard, C. Thom, and Y. Rabot. "STUDY OF LEVER-ARM EFFECT USING EMBEDDED PHOTOGRAMMETRY AND ON-BOARD GPS RECEIVER ON UAV FOR METROLOGICAL MAPPING PURPOSE AND PROPOSAL OF A FREE GROUND MEASUREMENTS CALIBRATION PROCEDURE." ISPRS - International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences XL-3/W4 (March 17, 2016): 65–70. http://dx.doi.org/10.5194/isprsarchives-xl-3-w4-65-2016.
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Nowadays, Unmanned Aerial Vehicle (UAV) on-board photogrammetry knows a significant growth due to the democratization of using drones in the civilian sector. Also, due to changes in regulations laws governing the rules of inclusion of a UAV in the airspace which become suitable for the development of professional activities. Fields of application of photogrammetry are diverse, for instance: architecture, geology, archaeology, mapping, industrial metrology, etc. Our research concerns the latter area. <i>Vinci-Construction- Terrassement</i> is a private company specialized in public earthworks that uses UAVs for metrology applications. This article deals with maximum accuracy one can achieve with a coupled camera and GPS receiver system for direct-georeferencing of Digital Surface Models (DSMs) without relying on Ground Control Points (GCPs) measurements. This article focuses specially on the lever-arm calibration part. This proposed calibration method is based on two steps: a first step involves the proper calibration for each sensor, i.e. to determine the position of the optical center of the camera and the GPS antenna phase center in a local coordinate system relative to the sensor. A second step concerns a 3<i>d</i> modeling of the UAV with embedded sensors through a photogrammetric acquisition. Processing this acquisition allows to determine the value of the lever-arm offset without using GCPs.
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Dallal, Nancy L., Bin Yin, Tereza Nekovářová, Aleš Stuchlík, and Warren H. Meck. "Impact of Vestibular Lesions on Allocentric Navigation and Interval Timing: The Role of Self-Initiated Motion in Spatial-Temporal Integration." Timing & Time Perception 3, no. 3-4 (December 10, 2015): 269–305. http://dx.doi.org/10.1163/22134468-03002053.
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Bilateral intratympanic sodium arsenate injections (100 mg/ml in isotonic saline) in adult male Long Evans rats produced impairments in allocentric navigation using a 12-arm radial maze procedure as well as a motor test battery designed to evaluate vestibular function. In contrast, no impairments in the accuracy or precision of duration reproduction using 20-s and 80-s peak-interval procedures were observed when both target durations were associated with the same lever response, but distinguished by signal modality (e.g., light or sound). In contrast, an ordinal-reproduction procedure with 800, 3200, and 12,800 ms standards requiring the timing of self-initiated movements during the production phase revealed large impairments in the accuracy and precision of timing for vestibular lesioned rats. These impairments were greater on trials in which self-initiated body movements (e.g., holding down the response lever for a fixed duration) were required without the support of external stimuli signaling the onset and offset of the reproduced duration in contrast to trials in which such external support was provided. The conclusion is that space and time are separable entities and not simply the product of a generalized system, but they can be integrated into a common metric using gravity and self-initiated movement as a reference.
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Lestari, Surya, Syahrial Syahrial, and Bambang Suwarno. "LANGUAGE SKILLS, SUB-SKILLS AND VOCABULARIES NEEDED BY AUTOMOTIVE DEPARTMENT STUDENTS OF TECHNICAL HIGH SCHOOL: A NEED ANALYSIS STUDY." JOALL (Journal of Applied Linguistics & Literature) 2, no. 2 (December 10, 2017): 65–75. http://dx.doi.org/10.33369/joall.v2i2.5955.
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This study aimed to analyze specific English language skills and kind of technical vocabulary that are needed by the third year automotive students of SMKN 2 Kota Bengkulu. The sample for interview comprised of 12 alumni, they were teachers and various company officers who have a MOU with SMKN 2 Kota Bengkulu. In the interview was used saturation sample. The results of interview with alumni indicate that the English skill most needed in the workplace is reading, the second was speaking, the third was writing and the last place was listening. The automotive students/ alumni need to comprehend the technical terms associated with technical terms in English. Related to car, are kick lever, oil pump, water cooling system, trail and rolling roof. Related to heavy machine are rear body offset, over hung, road clearance, light van and rear engine. Related to motorcycle are swing arm, bottom link fork, drum brake and kick starter. General automotive vocabulary are disc brake, gasoline, head lamp, piston and tire. Mastery of technical terms greatly affect the practice of industrial work (prakerin) of students in the work place.
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Murphy, Jennifer, Jose Yusta-Zato, Anish Patel, A. Mark Davies, Steven L. James, Callum McBryde, and Rajesh Botchu. "The use of pelvic radiographs as a predictor for gluteal tendinopathy and bursitis." HIP International 30, no. 6 (September 26, 2019): 775–78. http://dx.doi.org/10.1177/1120700019878417.
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Aim: To evaluate the relationship between radiographic measurements of the hip and sonographic evidence of gluteal tendinopathy and bursitis in patients with lateral hip pain. Methods and materials: Patients with lateral hip pain referred for ultrasound of the hip in our institution over a 5-year period were identified. Findings of gluteal tendinopathy and subgluteal or trochanteric bursitis on ultrasound were recorded. Radiographs of the hip were also evaluated and femoral offset (FO), global offset (GO), abductor lever arm (ALA) and trochanteric impingement distance (TID) were recorded. The mean of each measurement was compared between patients with gluteal tendinopathy and subgluteal or trochanteric bursitis. Results: 273 patients were included in the study. 107 patients (39.2%) had a THA. In the asymptomatic hip, a range of normal measurements were obtained: FO 22.4–76.5 mm, GO 40.1–116.1 mm, ALA 45.0–98.4 mm and TID 13.8–63.1 mm. In the native hip and post THA, there was no statistically significant relationship between FO, GO, ALA and TID in patients with gluteal tendinopathy or trochanteric or subgluteal bursitis. Conclusions: Lateral hip pain is a common presenting complaint in patients with hip pain and is reported in a small proportion of patients post THA. No statistically significant relationship was found between radiographic measurements and ultrasound findings in our patient cohort. However, we describe the range of measurements obtained from the normal asymptomatic hip in this large cohort of patients, which may aid in the evaluation and management of patients with lateral hip pain.
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Horvath, Sabine, and Hans Neuner. "System identification of a robot arm with extended Kalman filter and artificial neural networks." Journal of Applied Geodesy 13, no. 2 (April 26, 2019): 135–50. http://dx.doi.org/10.1515/jag-2018-0045.
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Abstract The development of an algorithm to describe a dynamic system and to predict its future behaviour in further consequence is the aim of the present study. Non parametric models provide a general description of object dynamics and artificial neural networks (ANN), which are a very flexible and universal learning method, belong to it. However, the standard estimation procedures for ANN like Levenberg-Marquardt (LM) do not consider that data is observed and consequently is uncertain. The combination with the extended Kalman filter (EKF) enables the consideration of the uncertainty in the estimation process. The analogies between EKF and LM are discussed and thereon the advantages of the EKF are outlined. The integration of ANN into EKF will be evaluated on an industrial robot arm. At first, a simplified model is determined; the ANN describes the robot position deviations as a function of the joint encoder values. The robot reference positions are measured by a laser tracker. In order to compare it with the robot outputs, the observations need to be transformed to the robot frame and the offset between the end-effector and the robot flange has to be determined. A method to estimate both parameters simultaneously is developed and the results are verified on basis of simulated data. This paper comprises two novel approaches. First, uncertainty is considered in the ANN estimation on basis of the combination with the EKF. Considering the full covariance matrix of the robot deviations leads to a better prediction of the robot’s behaviour. Second, an integrated transformation and lever arm determination is introduced and the robot’s repeatability presents the limiting factor of the achievable parameter uncertainty.
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Rehak, M., and J. Skaloud. "PERFORMANCE ASSESSMENT OF INTEGRATED SENSOR ORIENTATION WITH A LOW-COST GNSS RECEIVER." ISPRS Annals of Photogrammetry, Remote Sensing and Spatial Information Sciences IV-2/W3 (August 18, 2017): 75–80. http://dx.doi.org/10.5194/isprs-annals-iv-2-w3-75-2017.
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Mapping with Micro Aerial Vehicles (MAVs whose weight does not exceed 5&thinsp;kg) is gaining importance in applications such as corridor mapping, road and pipeline inspections, or mapping of large areas with homogeneous surface structure, e.g. forest or agricultural fields. In these challenging scenarios, integrated sensor orientation (ISO) improves effectiveness and accuracy. Furthermore, in block geometry configurations, this mode of operation allows mapping without ground control points (GCPs). Accurate camera positions are traditionally determined by carrier-phase GNSS (Global Navigation Satellite System) positioning. However, such mode of positioning has strong requirements on receiver’s and antenna’s performance. In this article, we present a mapping project in which we employ a single-frequency, low-cost (<&thinsp;$100) GNSS receiver on a MAV. The performance of the low-cost receiver is assessed by comparing its trajectory with a reference trajectory obtained by a survey-grade, multi-frequency GNSS receiver. In addition, the camera positions derived from these two trajectories are used as observations in bundle adjustment (BA) projects and mapping accuracy is evaluated at check points (ChP). Several BA scenarios are considered with absolute and relative aerial position control. Additionally, the presented experiments show the possibility of BA to determine a camera-antenna spatial offset, so-called lever-arm.
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Perrier, David, and Karine Monteil. "Triathlon Wet Suit and Technical Parameters at the Start and End of a 1500-m Swim." Journal of Applied Biomechanics 20, no. 1 (February 2004): 3–13. http://dx.doi.org/10.1123/jab.20.1.3.
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The aim of this study was to determine the effect of wearing a triathlon wet suit on the technical parameters of the front crawl stroke. Eight highly trained male triathletes were filmed with underwater camcorders during two 1500-m swim tests: one with a wet suit (WS) and the other with a standard suit (SS). Two conditions were considered: Condition I (CI) and Condition XV (CXV), representing the 1st and the 15th 100-m, respectively. Views were synchronized and digitized using kinematic analysis software (Schleihauf, 1994) to obtain 3-D coordinates of the anatomical landmarks of the body. Results showed that the wet suit and duration of the exercise significantly influenced stroke parameters. The swim with WS was characterized by greater stroke length and a progressive increase in stroke frequency, resulting from a more extended elbow position during the stroke and from a decrease in the absolute and relative times of the propulsive phase. These changes indicated more efficient upper limb action. The duration of exercise modified the swim with WS and SS. The loss of velocity observed in CXV was related to a decrease in stroke length, or more precisely a reduction in lever arm length during the aquatic phase, insufficiently offset by a slight increase in stroke frequency. These two motor responses, a less extended elbow position and a stroke frequency increase, emerged as an easier motor solution for coping with the effect of fatigue. This solution could be regarded as an adaptation to the duration of the exercise.
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Jeyaseelan, Lucky, Nicholas Cullen, Andrew Goldberg, and Matthew Welck. "Tibiotalocalcaneal Arthrodesis Using a Straight Intramedullary Nail." Foot & Ankle Orthopaedics 3, no. 3 (July 1, 2018): 2473011418S0026. http://dx.doi.org/10.1177/2473011418s00269.
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Category: Hindfoot Introduction/Purpose: Tibiotalocalcaneal (TTC) arthrodesis using a hindfoot intramedullary nail has been shown to be a safe and reliable technique in patients with severe ankle and hindfoot disease. There is debate about the use of straight nails versus curved nails. Proponents of the curved nail argue that straight nails predispose to greater risk of lateral plantar nerve injury, poor calcaneal bone purchase and inability to maintain satisfactory hindfoot valgus alignment. However, the subtalar joint is a condyloid joint enabling rotation of the talus on the calcaneum to create varus/valgus position of the calcaneal tuberosity. We present a clinical series of patients undergoing TTC fusion using a straight nail assessed by clinical and radiological outcomes to establish whether theoretical risks of straight nails are reflected in clinical practice. Methods: This single centre, retrospective study of prospectively collected data on a sequential series of patients to undergo TTC fusion, with pre and post-operative weight bearing CT imaging. Data was collected on indication for procedure, co-morbidities, post-operative complications, union rate as well as clinical scores, EQ5D and MOXFQ. Weight bearing CT imaging was analysed using the validated TALUS™ (torque ankle lever arm system) method on weight bearing CT, providing calcaneal offset, hindfoot angle and hindfoot alignment. These were used as markers of hindfoot alignment. Results: 65 patients (37 males, 28 females) were included in the study, with an average age of 57 years. Average follow-up was 20 months. Indications for TTC fusion included Charcot arthropathy, talar avascular necrosis, post traumatic arthritis and non-union of previous arthrodeses. Union rate was 91% (59/65). Overall complication rate was 11% (7/65) and most were minor wound complications. There were no plantar nerve injuries noted. There were no nail cut outs from the calcaneum. On all markers of hindfoot alignment, cases showed a more physiological degree of hindfoot valgus compared to pre-operative measures. There were significant improvement in both EQ5D and MOXFQ scores (p<0.05). Conclusion: We present the largest series of TTC fusion using a straight intramedullary nail and the first series to analyse hindfoot alignment using weight bearing 3D CT imaging. Our data regarding correction of hindfoot alignment is supported by biomechanical theories of subtalar varus/valgus, being related to rotatory changes at the subtalar joint, questioning the perceived need for a curved nail. This is particularly at the level of the entry point of the nail. The principles of valgus hindfoot nails are based on biomechanical laboratory studies and cadaveric studies, neither of which reflect our findings in clinical practice.
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Hintermann, Beat, Patric Scheidegger, Tamara Horn Lang, and Lukas Zwicky. "Flecting Osteotomy of the Distal Tibia for Salvage of an Asymmetric Osteoarthritic Ankle Joint." Foot & Ankle Orthopaedics 3, no. 3 (July 1, 2018): 2473011418S0006. http://dx.doi.org/10.1177/2473011418s00063.
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Category: Ankle Arthritis Introduction/Purpose: Deformity of the distal tibia in the sagittal plane with increased posterior tilt of the articular surface (recurvatum deformity) results in altered biomechanics and high contact pressure in the anterior tibiotalar joint with consecutive osteoarthritis (OA). As the talus becomes anteriorly extruded out of ankle mortise, the distance between its center of rotation and longitudinal axis of tibia is typically seen to be increased. In an attempt to restore physiologic load of such misaligned ankles in the sagittal plane, we have started to use a correcting osteotomy of the distal tibia to realign the center of rotation of talus and tibial axis. The aim of this study was to analyze the radiological and clinical outcome in a consecutive series of patients. Methods: 39 patients (female, 12; male 27; age 47 [28 to 72, SD 10.6] years) were treated with a flecting osteotomy of the distal tibia for a symptomatic misalignment in the sagittal plane with the use of an anterior opening wedge osteotomy (n = 28), posterior closing wedge osteotomy (n = 9), or dome-shaped osteotomy from medially (n = 2). If necessary, simultaneous corrections in the frontal plane were performed to address additional valgus/varus deformities. Standard weight-bearing radiographs were used pre- and postoperatively to evaluate the tibial anterior surface angle (TAS), tibiotalar surface angle (TTS), tibial lateral surface angle (TLS), calcaneal pitch and talar offset ratio (TOR). A four-staged flecting score was used to classify the grade of OA of the tibiotalar joint in the sagittal plane, also taking the coronal joint congruency into account. Results: The cumulative survival rate of the joint was 77% (95% CI: 48-86%) after 3 years, with 9 patients needing a joint sacrificing procedure (total ankle arthroplasty, 7; ankle fusion, 2). In the remaining 30 patients, pain decreased 2.0 points on the VAS (p <0.001), and the AOFAS hindfoot score improved by 17 points (p<0.001). The ROM did not change significantly. Patient satisfaction with the outcome was good in 68% and moderate in 25%, 7% were not satisfied. The mean TLS increased by 6.6 (SD 5.84) degrees, the mean TOR decreased 0.239 (SD 0.1814). TAS, TTS and calcaneal pitch did not change significantly. Ten ankles (26%) showed an improvement, 22 (56%) no change and 7 (18%) a worsening in the flecting score. Conclusion: The flecting osteotomy of the distal tibia was found to be an effective method to restore the tibiotalar joint congruency through moving the tibia axis anteriorly to the center of rotation of the talus, and lengthening the lever arm of the Achilles tendon. Besides normalizing the joint reaction forces of the tibiotalar joint, the procedure was also found to be effective to stabilize the talus against anterior extrusion. However, with a failure rate of 23%, there is need for further studies to determine the indication and limitation of this procedure.
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Kerstinga, A. P., and P. Friess. "POST-MISSION QUALITY ASSURANCE PROCEDURE FOR SURVEY-GRADE MOBILE MAPPING SYSTEMS." ISPRS - International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences XLI-B1 (June 6, 2016): 647–52. http://dx.doi.org/10.5194/isprsarchives-xli-b1-647-2016.
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Mobile Mapping Systems (MMS) consist of terrestrial-based moving platforms that integrate a set of imaging sensors (typically digital cameras and laser scanners) and a Position and Orientation System (POS), designed to collect data of the surrounding environment. MMS can be classified as “mapping-grade” or “survey-grade” depending on the system’s attainable accuracy. Mapping-grade MMS produce geospatial data suitable for GIS applications (e.g., asset management) while survey-grade systems should satisfy high-accuracy applications such as engineering/design projects. The delivered accuracy of an MMS is dependent on several factors such as the accuracy of the system measurements and calibration parameters. It is critical, especially for survey-grade systems, to implement a robust Quality Assurance (QA) procedure to ensure the achievement of the expected accuracy. In this paper, a new post-mission QA procedure is presented. The presented method consists of a fully-automated self-calibration process that allows for the estimation of corrections to the system calibration parameters (e.g., boresight angles and lever-arm offsets relating the lidar sensor(s) to the IMU body frame) as well as corrections to the system measurements (e.g., post-processed trajectory position and orientation, scan angles and ranges). As for the system measurements, the major challenge for MMS is related to the trajectory determination in the presence of multipath signals and GNSS outages caused by buildings, underpasses and high vegetation. In the proposed self-calibration method, trajectory position errors are properly modelled while utilizing an efficient/meaningful trajectory segmentation technique. The validity of the proposed method is demonstrated using a dataset collected under unfavorable GNSS conditions.
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Kerstinga, A. P., and P. Friess. "POST-MISSION QUALITY ASSURANCE PROCEDURE FOR SURVEY-GRADE MOBILE MAPPING SYSTEMS." ISPRS - International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences XLI-B1 (June 6, 2016): 647–52. http://dx.doi.org/10.5194/isprs-archives-xli-b1-647-2016.
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Mobile Mapping Systems (MMS) consist of terrestrial-based moving platforms that integrate a set of imaging sensors (typically digital cameras and laser scanners) and a Position and Orientation System (POS), designed to collect data of the surrounding environment. MMS can be classified as “mapping-grade” or “survey-grade” depending on the system’s attainable accuracy. Mapping-grade MMS produce geospatial data suitable for GIS applications (e.g., asset management) while survey-grade systems should satisfy high-accuracy applications such as engineering/design projects. The delivered accuracy of an MMS is dependent on several factors such as the accuracy of the system measurements and calibration parameters. It is critical, especially for survey-grade systems, to implement a robust Quality Assurance (QA) procedure to ensure the achievement of the expected accuracy. In this paper, a new post-mission QA procedure is presented. The presented method consists of a fully-automated self-calibration process that allows for the estimation of corrections to the system calibration parameters (e.g., boresight angles and lever-arm offsets relating the lidar sensor(s) to the IMU body frame) as well as corrections to the system measurements (e.g., post-processed trajectory position and orientation, scan angles and ranges). As for the system measurements, the major challenge for MMS is related to the trajectory determination in the presence of multipath signals and GNSS outages caused by buildings, underpasses and high vegetation. In the proposed self-calibration method, trajectory position errors are properly modelled while utilizing an efficient/meaningful trajectory segmentation technique. The validity of the proposed method is demonstrated using a dataset collected under unfavorable GNSS conditions.
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Mitishita, E., R. Barrios, and J. Centeno. "The influence of the in situ camera calibration for direct georeferencing of aerial imagery." ISPRS - International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences XL-1 (November 7, 2014): 273–78. http://dx.doi.org/10.5194/isprsarchives-xl-1-273-2014.
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The direct determination of exterior orientation parameters (EOPs) of aerial images via GNSS/INS technologies is an essential prerequisite in photogrammetric mapping nowadays. Although direct sensor orientation technologies provide a high degree of automation in the process due to the GNSS/INS technologies, the accuracies of the obtained results depend on the quality of a group of parameters that models accurately the conditions of the system at the moment the job is performed. One sub-group of parameters (lever arm offsets and boresight misalignments) models the position and orientation of the sensors with respect to the IMU body frame due to the impossibility of having all sensors on the same position and orientation in the airborne platform. Another sub-group of parameters models the internal characteristics of the sensor (IOP). A system calibration procedure has been recommended by worldwide studies to obtain accurate parameters (mounting and sensor characteristics) for applications of the direct sensor orientation. Commonly, mounting and sensor characteristics are not stable; they can vary in different flight conditions. The system calibration requires a geometric arrangement of the flight and/or control points to decouple correlated parameters, which are not available in the conventional photogrammetric flight. Considering this difficulty, this study investigates the feasibility of the in situ camera calibration to improve the accuracy of the direct georeferencing of aerial images. The camera calibration uses a minimum image block, extracted from the conventional photogrammetric flight, and control point arrangement. A digital Vexcel UltraCam XP camera connected to POS AV TM system was used to get two photogrammetric image blocks. The blocks have different flight directions and opposite flight line. In situ calibration procedures to compute different sets of IOPs are performed and their results are analyzed and used in photogrammetric experiments. The IOPs from the in situ camera calibration improve significantly the accuracies of the direct georeferencing. The obtained results from the experiments are shown and discussed.
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De Pieri, Enrico, Federica Atzori, Stephen J. Ferguson, Sebastian Dendorfer, Michael Leunig, and Martin Aepli. "Contact force path in total hip arthroplasty: effect of cup medialisation in a whole-body simulation." HIP International, April 28, 2020, 112070002091732. http://dx.doi.org/10.1177/1120700020917321.
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Background: Cup medialisation down to the true acetabular floor in total hip arthroplasty with a compensatory femoral offset increase seems to be mechanically advantageous for the abductor muscles due to the relocation of the lever arms (body weight lever arm decreased, abductor lever arm increased). However, limited information is currently available about the effects of this reconstruction type at the head cup interface, compared to an anatomical reconstruction that maintains the natural lever arms. Through a whole-body simulation analysis, we compared medialised versus anatomical reconstruction in THA to analyse the effects on: (1) contact force magnitude at the head cup interface; (2) contact force path in the cup; and (3) abductor activity. Methods: Musculoskeletal simulations were performed to calculate the above-mentioned parameters using inverse dynamics analysis. The differences between the virtually implanted THAs were calculated to compare the medialised versus anatomical reconstruction. Results: Cup medialisation with compensatory femoral offset increase led to: (1) a reduction in contact force magnitude at the head cup interface up to 6.6%; (2) a similar contact force path in the cup in terms of sliding distance and aspect ratio; and (3) a reduction in abductor activity up to 17.2% (gluteus medius). Conclusions: In our opinion, these potential biomechanical gains do not generally justify a fully medialised reconstruction, especially in younger patients that are more likely to undergo revision surgery in their lifetime. Cup medialisation should be performed until sufficient press fit and bony coverage of a properly sized and oriented cup can be achieved.
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Sharma, Manish, Ramesh Kumar Sen, Sameer Aggarwal, and Mahesh Prakash. "ANALYSIS OF THE RADIOLOGICAL ASSESSMENT OF RECONSTRUCTION IN TOTAL HIP ARTHROPLASTY." International Journal of Medical and Biomedical Studies 4, no. 1 (January 16, 2020). http://dx.doi.org/10.32553/ijmbs.v4i1.875.
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Background: Total hip Arthroplasty (THA) is one of the most common interventions in Orthopaedic surgery. Increase in incidence of THA appears likely with the growing elderly population. THA has revolutionised the management of the patients suffering from pathologies of the hip. The common indications for THA today are osteoarthritis hip, avascular necrosis hip, ankylosing spondylitis, rheumatoid arthritis and in posttraumatic hip.
Methods: The study was carried as a retrospective study, from February 2013 to July 2014. After getting the approval from the Ethics Committee of the Institute (Annexure I) and the consent from the patients the study was conducted on 49 patients who underwent Total Hip Arthroplasty after fracture acetabulum.
Results: Based on the treatment received for fracture acetabulum, the vertical offset measurement was done for 47 patients. The affected side was compared with the un-affected side in the patient and a restoration of vertical offset on the affected side within 20% of the unaffected side was taken as acceptable. In 31 patients acceptable vertical offset was restored.
Conclusion: Radiological assessment of the patients was done using 4 parameters. Measurement of Vertical offset, Horizontal offset, Body lever arm and Acetabular cup inclination was done. The affected side was compared with the un-affected side in the patient and a restoration of parameters on the affected side within 20% of the unaffected side was taken acceptable.
Keywords: Radiological, Arthroplasty, Reconstruction
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Arndt, Christoph, Christian Voigt, Hanno Steinke, Georg v. Salis-Soglio, and Roger Scholz. "Experimental Evidence of Impingement Induced Strains at the Interface and the Periphery of an Embedded Acetabular Cup Implant." Journal of Biomechanical Engineering 134, no. 1 (January 1, 2012). http://dx.doi.org/10.1115/1.4005686.
Full textAbstract:
After total hip arthroplasty, impingement of implant components may occur during every-day patient activities causing increased shear stresses at the acetabular implant–bone interface. In the literature, impingement related lever-out moments were noted for a number of acetabular components. But there is little information about pelvic load transfer. The aim of the current study was to measure the three-dimensional strain distribution at the macrostructured hemispherical interface and in the periphery of a standard acetabular press-fit cup in an experimental implant-bone substitute model. An experimental setup was developed to simulate impingement loading via a lever arm representing the femoral component and the lower limb. In one experimental setup 12 strain gauges were embedded at predefined positions in the periphery of the acetabular cup implant inside a tray, using polyurethane composite resin as a bone substitute material. By incremental rotation of the implant tray in steps of 10 and 30 deg, respectively, the strains were measured at evenly distributed positions. With the described method 288 genuine strain values were measured in the periphery of an embedded acetabular cup implant in one experimental setup. In two additional setups the strains were evaluated at different distances from the implant interface. Both in radial and meridional interface directions strain magnitudes reach their peak near the rim of the cup below the impingement site. Values of equatorial strains vary near zero and reach their peaks near the rim of the cup on either side and in some distance from the impingement site. Interestingly, the maximum of averaged radial strains does not occur, as expected, close to the interface but at an interface offset of 5.6 mm. With the described experimental setup it is now possible to measure and display the three-dimensional strain distribution in the interface and the periphery of an embedded acetabular cup implant. The current study provides the first experimental proof of the high local stresses gradients in the direct vicinity of the impingement site. The results of the current study help for a better understanding of the impingement mechanism and its impact on acetabular cup stability.