Spinopelvic mobility affects accuracy of acetabular anteversion measurements on cross-table lateral radiographs

Aims Cross-table lateral (CTL) radiographs are commonly used to measure acetabular component anteversion after total hip arthroplasty (THA). The CTL measurements may differ by > 10° from CT scan measurements but the reasons for this discrepancy are poorly understood. Anteversion measurements from CTL radiographs and CT scans are compared to identify spinopelvic parameters predictive of inaccuracy. Methods THA patients (n = 47; 27 males, 20 females; mean age 62.9 years (SD 6.95)) with preoperative spinopelvic mobility, radiological analysis, and postoperative CT scans were retrospectively reviewed. Acetabular component anteversion was measured on postoperative CTL radiographs and CT scans using 3D reconstructions of the pelvis. Two cohorts were identified based on a CTL-CT error of ≥ 10° (n = 11) or < 10° (n = 36). Spinopelvic mobility parameters were compared using independent-samples t-tests. Correlation between error and mobility parameters were assessed with Pearson’s coefficient. Results Patients with CTL error > 10° (10° to 14°) had stiffer lumbar spines with less mean lumbar flexion (38.9°(SD 11.6°) vs 47.4° (SD 13.1°); p = 0.030), different sagittal balance measured by pelvic incidence-lumbar lordosis mismatch (5.9° (SD 18.8°) vs -1.7° (SD 9.8°); p = 0.042), more pelvic extension when seated (pelvic tilt -9.7° (SD 14.1°) vs -2.2° (SD 13.2°); p = 0.050), and greater change in pelvic tilt between supine and seated positions (12.6° (SD 12.1°) vs 4.7° (SD 12.5°); p = 0.036). The CTL measurement error showed a positive correlation with increased CTL anteversion ( r = 0.5; p = 0.001), standing lordosis ( r = 0.23; p = 0.050), seated lordosis ( r = 0.4; p = 0.009), and pelvic tilt change between supine and step-up positions ( r = 0.34; p = 0.010). Conclusion Differences in spinopelvic mobility may explain the variability of acetabular anteversion measurements made on CTL radiographs. Patients with stiff spines and increased compensatory pelvic movement have less accurate measurements on CTL radiographs. Flexion of the contralateral hip is required to obtain clear CTL radiographs. In patients with lumbar stiffness, this movement may extend the pelvis and increase anteversion of the acetabulum on CTL views. Reliable analysis of acetabular component anteversion in this patient population may require advanced imaging with a CT scan. Cite this article: Bone Joint J 2021;103-B(7 Supple B):59–65.

Effect of Decreasing the Anterior Pelvic Tilt on Range of Motion in Femoroacetabular Impingement: A Computer-Simulation Study

Background: The influence of pelvic tilt mobility, which can be reproduced in computer-simulation models, is an important subject to be addressed in the understanding of femoroacetabular impingement (FAI) pathophysiology. Purpose: To use computer-simulation models of FAI cases to evaluate the optimum improvement in hip range of motion (ROM) achieved by decreasing the anterior pelvic tilt and compare the results with the improvement in ROM achieved after cam resection surgery. Study Design: Controlled laboratory study. Methods: The pre- and postoperative computed tomography (CT) images from 28 patients with FAI treated with arthroscopic cam resection were evaluated. Using a dynamic computer-simulation program, 3-dimensional models with a 5° and a 10° decrease in anterior pelvic tilt from the supine functional pelvic plane (baseline) were created from the preoperative CT scans. Similar models were constructed for hips before (at baseline) and after cam resection. Improvements from baseline in maximum internal rotation at 45°, 70°, and 90° of flexion were assessed for the 5° change in pelvic tilt, 10° change in pelvic tilt, and cam resection models, and the results were compared for all conditions. Results: The combination of a 10° change in pelvic tilt and cam resection showed the largest ROM improvement from baseline ( P < .001). Improvement in internal rotation in the cam resection model was significantly higher compared with the 5° pelvic tilt change model ( P < .001), while there was no significant difference between the cam resection model and the 10° pelvic tilt change model. Conclusion: Decreasing anterior pelvic tilt by 10° in the preoperative computer simulation model resulted in an equivalent effect to cam resection, while a 5° change in pelvic tilt was inferior to cam resection in terms of ROM improvement. Clinical Relevance: Enough of a decrease in anterior pelvic tilt may contribute to ROM improvement that is as effective as that of cam resection surgery.

Tilt and strain change during the explosion at Minami-dake, Sakurajima, on November 13, 2017

We herein propose an alternative model for deformation caused by an eruption at Sakurajima, which has been previously interpreted as being due to a Mogi-type spherical point source beneath Minami-dake. On November 13, 2017, a large explosion with a plume height of 4200 m occurred at Minami-dake. During the 3 min following the onset of the explosion (November 13, 2017, 22:07–22:10 (Japan standard time (UTC + 9); the same hereinafter), phase 1, a large strain with changes up to 120 nstrain was detected at the Arimura observation tunnel (AVOT) located approximately 2.1 km southeast from the Minami-dake crater. After the peak of the explosion (November 13, 2017, 22:10–24:00), phase 2, a large deflation was detected at every monitoring station due to the continuous Strombolian eruption. Subsidence toward Minami-dake was detected at five out of six stations, whereas subsidence toward the north of Sakurajima was detected at the newly installed Komen observation tunnel (KMT), located approximately 4.0 km northeast from the Minami-dake crater. The large strain change at AVOT as well as small tilt changes at all stations and small strain changes at the Harutayama observation tunnel (HVOT) and KMT during phase 1 can be explained by a very shallow deflation source beneath Minami-dake at 0.1 km below sea level (bsl). For phase 2, a deeper deflation source beneath Minami-dake at a depth of 3.3 km bsl was found in addition to the shallow source beneath Minami-dake, which turned inflation after the deflation that occurred during phase 1. However, this model cannot explain the tilt change of KMT. Adding a spherical deflation source beneath Kita-dake at a depth of 3.2 km bsl can explain the tilt and strain change at KMT and the other stations. The Kita-dake source was also found in a previous study of long-term ground deformation. Not only the deeper Minami-dake source MD, but also the Kita-dake source deflated due to the Minami-dake explosion.

Tilt and strain change during the explosion at Minami-dake, Sakurajima, on November 13, 2017

We herein propose an alternative model for deformation caused by an eruption at Sakurajima, which have been previously interpreted as being due to a Mogi-type spherical point source beneath Minami-dake. On November 13, 2017, a large explosion with a plume height of 4,200 m occurred at Minami-dake. During the three minutes following the onset of the explosion (November 13, 2017, 22:07–22:10 (Japan standard time (UTC+9); the same hereinafter), phase 1, a large strain change was detected at the Arimura observation tunnel (AVOT) located approximately 2.1 km southeast from the Minami-dake crater. After the peak of the explosion (November 13, 2017, 22:10–24:00), phase 2, a large deflation was detected at every monitoring station due to the continuous Strombolian eruption. Subsidence toward Minami-dake was detected at five out of six stations whereas subsidence toward the north of Sakurajima was detected at the newly installed Komen observation tunnel (KMT), located approximately 4.0 km northeast from the Minami-dake crater. The large strain change at AVOT as well as small tilt changes of all stations and small strain changes at HVOT and KMT during phase 1 can be explained by a very shallow deflation source beneath Minami-dake at 0.1 km below sea level (bsl). For phase 2, a deeper deflation source beneath Minami-dake at a depth of 3.3 km bsl was found in addition to the shallow source beneath Minami-dake which turned inflation after the deflation obtained during phase 1. However, this model cannot explain the tilt change of KMT. Adding a spherical deflation source beneath Kita-dake at a depth of 3.2 km bsl can explain the tilt and strain change at KMT and the other stations. The Kita-dake source was also found in a previous study of long-term ground deformation. Not only the deeper Minami-dake source MD but also the Kita-dake source deflated due to the Minami-dake explosion.

Tilt and Strain Change During the Explosion at Minami-dake, Sakurajima, on November 13, 2017

We herein proposed an alternative model for deformation caused by each eruption at Sakurajima, which have been previously interpreted as being due to a Mogi-type source beneath Minami-dake. On November 13, 2017, a large explosion with a plume height of 4,200 m occurred at Minami-dake. During the three minutes following the onset of the explosion (November 13, 2017, 22:07–22:10 (Japan standard time (UTC+9); the same hereinafter), phase 1, a large strain change was detected at the Arimura observation tunnel (AVOT) located approximately 2.1 km southeast from the Minami-dake crater. After the climax of the explosion (November 13, 2017, 22:10–24:00), phase 2, a large deflation was detected at every monitoring stations due to the continuous Strombolian eruption. Subsidence toward Minami-dake was detected at five out of six stations whereas subsidence toward the north of Sakurajima was detected at the newly installed Komen observation tunnel (KMT), located approximately 4.0 km northeast from the Minami-dake crater. The large strain change at AVOT during phase 1 can be explained by a very shallow deflation source beneath Minami-dake at 0.1 km below sea level (bsl). For phase 2, a deeper source beneath Minami-dake at a depth of 3.3 km bsl deflated in addition to the shallow source beneath Minami-dake, which turned inflationary after the deflation obtained during phase 1. However, this model cannot explain the tilt change of KMT. Adding a spherical deflation source beneath Kita-dake at a depth of 3.2 km bsl can be explain the tilt and strain change at KMT and the other stations. The Kita-dake source was also found in a previous study of long-term ground deformation events. Not only the deeper Minami-dake source M D but also the Kita-dake source deflated due to the Minami-dake explosion.

The new tiltmetric network of Tenerife: technical and scientific issues

&lt;p&gt;Since 2004, the Instituto Tecnol&amp;#243;gico y de Energ&amp;#237;as Renovables (ITER) in collaboration, since 2011, with the Instituto Volcanol&amp;#243;gico de Canarias (INVOLCAN), are monitoring Canary Islands archipelago with a network of more than 30 differential GPS stations. Specifically, in Tenerife island alone there are 12 permanent GPS receivers. Data are processed automatically using Bernese software, constituting an important tool for the geodetic monitoring of Tenerife.&lt;/p&gt;&lt;p&gt;Since 2016, the volcanic system of Tenerife is experiencing a hydrothermal unrest, with a marked increase of the diffuse CO&lt;sub&gt;2&lt;/sub&gt; flux from the crater of Mt. Teide, the major volcanic edifice of the island. This increased flux is likely to be related to the injection of fluids of magmatic origin within the hydrothermal system of Tenerife. The subsequent pressurization of this system is reflected also by the increase in the background microseismicity observed since July 2017. Until now, the GPS network has not recorded significant ground deformation above the instrumental error.&lt;/p&gt;&lt;p&gt;With the aim of improving the geodetic monitoring of Tenerife, detecting possible small ground deformation below the sensitivity of the GPS network, INVOLCAN has recently started deploying, since June 2019, high-gain tiltmeters (Jewell Instruments A603-C) in the surrounding of Mt. Teide. Currently the tiltmetric network consists of 3 tiltmeters, located close to existing seismic or GPS stations. Data are automatically downloaded via UMTS connection and processed daily.&lt;/p&gt;&lt;p&gt;The nominal sensitivity of such instruments is less than 2.5 nradians, hence their installation and calibration require very careful operations. The sensors are equipped with leveling worm-gear feet to guarantee a perfect levelling. However, the high sensitivity of the instrumentation makes adjustments made manually totally useless. The tilt change caused by the weight of the human operator during the levelling is enough to drive the instrument out of scale. For this reason, INVOLCAN developed a robotic system to perform the required adjustments from remote. The system is based on Arduino Mega 2560, driving two servomotors to adjust the leveling worm-gears. Another servomotor allows switching the gain level. The system can be accessed and operated through an internal web page, which allows driving the servomotors and checking the leveling of the tiltmeter platform by using an Arduino Ethernet.&lt;/p&gt;

Mobile Controlled Automated wheelchair for Disabilities

As the usage of the Android smart phones has been considerably increasing, a lot of applications have been developed for the benefits of mobile users. In the past, many applications have been designed aiming to help physically disabled persons. This paper presents an android application which providers several options for controlling the movement of wheelchairs effectively. The proposed application enables People with Disabilities (PWDs) to operate the wheel chair with minimum effort. Apart from voice commands, the proposed application detects and measures the tilt change, and moves the wheelchair based on the degree of the tilt. It also provides a soft joystick as in mobile games to ease the operation of the wheelchairs. Furthermore, sensors that are fixed in the wheelchair can detect and avoid obstacles when the chair is on the move. Hence, it ensures the safety while using the wheelchairs. The proposed application will help both physically challenged persons and elders to operate the wheelchairs more comfortably.