Translation Distance Research Articles

Novel posterior artificial atlanto-odontoid joint for atlantoaxial instability: a biomechanical study.

OBJECTIVE Atlantoaxial instability is usually corrected by anterior and/or posterior C1-2 fusion. However, fusion can lead to considerable loss of movement at the C1-2 level, which can adversely impact a patient's quality of life. In this study, the authors investigated the stability and function of a novel posterior artificial atlanto-odontoid joint (NPAAJ) by using cadaveric cervical spines. METHODS The Oc-C7 regions from 10 cadaveric spines were used for anteroposterior (AP) translation and range of motion (ROM) tests while intact and after destabilization, NPAAJ implantation, and double-rod fixation. RESULTS The mean AP C1-2 translational distances in the intact, destabilization, and double-rod groups were 6.53 ± 1.07 mm, 11.54 ± 1.59 mm, and 3.24 ± 0.99 mm, respectively, and the AP translational distance in the NPAAJ group was significantly different from that in the intact group (p < 0.05). The AP translational distance in the NPAAJ group was not significantly different from that in the double-rod group (p = 0.24). The mean flexion, extension, and axial rotation ROM values of the NPAAJ group were 9.87° ± 0.91°, 8.75° ± 0.99°, and 61.93° ± 2.93°, respectively, and these were lower than the corresponding values in the intact group (p < 0.05). The mean lateral bending ROM in the NPAAJ group (9.26° ± 0.86°) was not significantly different from that in the intact group (p = 0.23), and the flexion, extension, and rotation ranges in the NPAAJ group were 79.5%, 85.2%, and 82.3%, respectively, of those in the intact group. CONCLUSIONS Use of NPAAJ for correction of atlantoaxial instability disorders caused by congenital odontoid dysplasia, odontoid fracture nonunion, and C-1 transverse ligament disruption (IA, IB, and IIB) may restore the stability and preserve most of the ROM of C1-2. Additionally, the NPAAJ may prevent soft tissue from embedding within the joint. However, additional studies should be performed before the NPAAJ is used clinically.

Evaluation of the Translation Distance of the Glenohumeral Joint and the Function of the Rotator Cuff on Its Translation: A Cadaveric Study

To evaluate the distance and position of humeral head translation during glenohumeral motion and to investigate the function of the rotator cuff in glenohumeral translation. Using 9 cadavers, glenohumeral translation during passive pendulum motion was tracked by an optical motion capture system. Tension was applied to 5 compartments of the rotator cuff muscles, and 7 different conditions of rotator cuff dysfunction were sequentially simulated. Three-dimensional glenohumeral structure was reconstructed from the computed tomography images of the specimens, and the distance and position of glenohumeral translation were compared among the conditions. The average radius of glenohumeral translation was 10.6 ± 4.3mm when static loading was applied to all rotator cuff muscles. The radius increased significantly in the models without traction force on the supraspinatus and total subscapularis tendons (P= .030). The position of the translation center did not change in the mediolateral direction (P=.587) and in the anteroposterior direction (P= .138), but it moved significantly superiorly in the models without supraspinatus and infraspinatus loading (P= .011) and in those without supraspinatus, infraspinatus, and teres minor loading (P < .001). The distance and position of humeral head translation during glenohumeral motion changed with rotator cuff deficiency. The present study indicated that the subscapularis plays an important role in maintaining the central position of the humeral head, and that the infraspinatus acts as a major depressor of the humeral head during shoulder motion. The results of this study suggest that extension of a tear into the subscapularis should be avoided to maintain the centering function of the glenohumeral joint in cases with rotator cuff tear.

Freeform lens design to eliminate retroreflection for optical systems.

This paper presents an effective approach to alleviate the cat-eye effect by inserting a freeform single lens into the original optical system. By shifting the image of the given optical system transversely on the original image plane, the reflected beams originating from the sensor are subsequently blocked by the optical aperture, substantially eliminating retroreflections from the system. The influence of incident angle on retroreflected beams is analyzed in detail, and the optimal image translation distance for completely eliminating the cat-eye effect is also proposed via numerical simulations. According to the translation requirement, a freeform single lens comprised of two different freeform surfaces is designed for the given system as the only translation element. The design recipe is elaborated on the basis of phase pupil function. Furthermore, a design example is demonstrated to verify the feasibility of our proposal. After optimization with optical design software, the modulation transfer function (MTF) of the modified system after translation is close to the diffraction limit, and the cat-eye reflected beam could be eliminated thoroughly.

Fundamental Limits of Optical Tweezer Nanoparticle Manipulation Speeds.

Optical tweezers are a noncontact method of 3D positioning applicable to the fields of micro- and nanomanipulation and assembly, among others. In these applications, the ability to manipulate particles over relatively long distances at high speed is essential in determining overall process efficiency and throughput. In order to maximize manipulation speeds, it is necessary to increase the trapping laser power, which is often accompanied by undesirable heating effects due to material absorption. As such, the majority of previous studies focus primarily on trapping large dielectric microspheres using slow movement speeds at low laser powers, over relatively short translation distances. In contrast, we push nanoparticle manipulation beyond the region in which maximum lateral movement speed is linearly proportional to laser power, and investigate the fundamental limits imposed by material absorption, thus quantifying maximum possible speeds attainable with optical tweezers. We find that gold and silver nanospheres of diameter 100 nm are limited to manipulation speeds of ∼0.15 mm/s, while polystyrene spheres of diameter 160 nm can reach speeds up to ∼0.17 mm/s, over distances ranging from 0.1 to 1 mm. When the laser power is increased beyond the values used for these maximum manipulation speeds, the nanoparticles are no longer stably trapped in 3D due to weak confinement as a result of material absorption, heating, microbubble formation, and enhanced Brownian motion. We compared this result to our theoretical model, incorporating optical forces in the Rayleigh regime, Stokes' drag, and absorption effects, and found good agreement. These results show that optical tweezers can be fast enough to compete with other common, serial rapid prototyping and nanofabrication approaches.

Contribution of the Ligamentum Teres to Hip Stability in the Presence of an Intact Capsule: A Cadaveric Study

To determine the contribution of the ligamentum teres (LT) to hip stability in the presence of an intact capsule with special attention to the change in range of motion and femoral head translation. Seven fresh-frozen cadaveric pelvises were used. Following visual inspection of the LT at different hip positions, internal rotation angles were measured at 10° of extension and at 0° of flexion, while external rotation was measured at 60°, 90°, and 110° of flexion with different hip abduction angles using electromagnetic motion tracking sensor. Femoral head translations were measured simultaneously. The tests were repeated after resection of the LT. The capsule was left intact for all test conditions. The results were compared between intact and LT resected conditions when torque of 2 and 4Nm was applied. Compared with the intact hip, the LT resected hip showed no significant difference when 2Nm torque was applied in all scenarios. With 4 Nm torque application, significant increase in external rotation was found at 60° and at 90° of flexion (1.7° ± 0.8° and 2.1° ± 1.0°, respectively). Significant difference was also noted at 60°, 90°, and 110° of flexion when the hip was in the adducted position while at 90° in the abducted hip. However, LT resection did not show significant change in internal rotation. There was no significant difference in the translation distance of the femoral head in the intact hip compared with the LT resected hip (0.77-1.11mm vs 0.79-1.29mm). Our results indicate that within the physiologic range of motion, LT can minimally limit external rotation when the hip is in the flexed position but does not contribute to translation stability. In the hip with intact capsule, LT deficiency can result in a slight increase in range of motion, but its contribution to stability is questionable.

Analysis and research of polarization aberration in rapid space angle measuring system

The precise angle measurement and transmission technology have been widely used in the precision measurement, aerospace, military, biomedicine and other devices, which are based on the polarized light and magneto-optical modulation. This method has the characteristics of no rigid connection required, long distance transmission, high precision, etc. However, the azimuth information measurement method needs the assistance of complex servo tracking system according to the orthogonal extinction principle of polarization prism, meanwhile, the measurement time is longer, which reduces reliability and reaction sensitivity of the system. In order to improve the measurement accuracy and fast response capability of the system, a fast space goniometry method is proposed through the Wollaston prism polarizing beam splitter, with which the azimuth is directly calculated according to the two light intensities. The measurement time can be shortened, and the accuracy is improved by the use of magneto-optical modulation technology. The rapid space angle measuring system needs to realize the measurement function in a certain translation range, which requires the beam to have a certain coverage area in the receiving unit. However, the system is limited by size and volume of the device; we can only choose to expand the incident beam. Therefore, when the beam is incident onto the receiving unit, some incident angle and azimuth, that is, non-vertical incidence will be produced. However, the polarization of the non-vertically incident light passing through the system will change and polarization aberration exists, which will lead to measurement error. In this paper, the beam passes through the polarizing prism in a certain range of azimuths and incident angles, and the polarized light tracing method and the boundary condition of the electromagnetic field are used to study and simulate the polarization change and distribution of the outgoing beam. The changes of different incident azimuths and angles can be simulated through the translation of receiving unit, and the azimuths can be measured indirectly by using self-collimation theodolite and right angle prism. By comparing the measured azimuths under the translational and centering conditions, the influence of polarization aberration on the angle measuring system and the correctness of the theoretical analysis are verified. It is concluded that when the azimuth angle is 0, the measurement error is small; when the azimuth is 90, the measurement error is largest, meanwhile the measurement error will increase with the translation distance becoming longer (i.e., the incident angle). According to the comparison between the experimental data and the simulation results, the existing problems are pointed out, and the corresponding improvement measures are proposed. The results of this work have some significance in guiding the optimization of the system structure, and the further improvement inthe performance of the system.

Aerodynamic characteristics along the wing span of a dragonfly Pantala flavescens.

We investigated the characteristics of interwing aerodynamic interactions across the span of the high aspect ratio, flexible wings of dragonflies under tethered and free-flying conditions. This revealed that the effects of the interactions on the hindwings vary across four spanwise regions. (i) Close to the wing root, a trailing-edge vortex (TEV) is formed by each stroke, while the formation of a leading-edge vortex (LEV) is limited by the short translational distance of the hindwing and suppressed by the forewing-induced flow. (ii) In the region away from the wing root but not quite up to midspan, the formation of the hindwing LEV is influenced by that of the forewing LEV. This vortex synergy can increase the circulation of the hindwing LEV in the corresponding cross-section by 22% versus that of the hindwing in isolation. (iii) In the region about half-way between the wing root and wing tip there is a transition dominated by downwash from the forewing resulting in flow attached to the hindwing. (iv) A LEV is developed in the remaining, outer region of the wing at the end of a stroke when the hindwing captures the vortex shed by the forewing. The interaction effects depend not only on the wing phasing but also on the flapping offset and flight direction. The aerodynamics of the hindwings vary substantially from the wing root to the wing tip. For a given phasing, this spanwise variation in the aerodynamics can be exploited in the design of artificial wings to achieve greater agility and higher efficiency.

Layered ferrimagnets constructed from charge-transferred paddlewheel [Ru2] units and TCNQ derivatives: the importance of interlayer translational distance in determining magnetic ground state.

A donor (D)/acceptor (A) assembly reaction using the paddlewheel-type diruthenium(ii,ii) complex [Ru2(3,5-F2PhCO2)4(THF)2] (3,5-F2PhCO2- = 3,5-difluorobenzoate; abbreviated hereafter as [Ru2]) as D and 7,7,8,8-tetracyano-p-quinodimethane derivatives (TCNQRx; 2,5-R-substituted TCNQ) as A in a DCM/TCE or DCE solvent system (DCM = dichloromethane, TCE = 1,1,2,2-tetrachloroethane, DCE = 1,2-dichloroethane) led to the formation of D2A-type two-dimensional layered compounds [{Ru2(3,5-F2PhCO2)4}2{TCNQRx}]·nsolv (Rx = H2 (1), Rx = Me2, (2), and Rx = (OEt)2 (3)). All the compounds had similar two-dimensional fishnet-type structures, where the two [Ru2] units were fully coordinated with the four cyano groups of TCNQRx. The compounds 1-3 were categorized as a one-electron transferred ionic state (1e-I) with D+-A--D formulation (D+[triple bond, length as m-dash][RuII,III2]+; A-[triple bond, length as m-dash]TCNQRx˙-). This subunit state formally derived a ferrimagnetically ordered state composed of up-spins with S = 1 for [RuII,II2] and S = 3/2 for [RuII,III2]+ and a down-spin of S = 1/2 for TCNQRx˙-, with antiferromagnetic superexchange interactions in each layer. Eventually, 1-3 became three-dimensional ferrimagnets with Curie temperatures TC = 93, 93, and 92 K, respectively, owing to the presence of interlayer ferromagnetic interactions. The interlayer translational distances (l2) for the three compounds were 10.56, 10.54, and 10.84 Å, respectively, which agreed with the empirical prediction based on the threshold value of l2 > 10.3 Å for a valid ferromagnetic interaction.

Geometric Comparison of Second Metatarsal Shortening Osteotomy Variations Using 3D Printed Patient-Specific Models

Category: Midfoot/Forefoot Introduction/Purpose: Second metatarsal shortening osteotomy is frequently used in the treatment of metatarsalgia and aims to decrease metatarsophalangeal joint and plantar pressures. Although various proximal, midshaft, and distal metatarsal osteotomy methods have been described for surgical treatment of metatarsalgia, to our knowledge no studies quantitatively compared their resulting geometric corrections. The purpose of our study was to investigate how much each osteotomy variation changed the length of the metatarsal as well as the height and relative location of the metatarsal head (MH) itself. Methods: Following Institutional Review Board approval, three-dimensional computer models of second metatarsals of 5 deidentified clinic patients were extracted from CT scans using Mimics software. Fixed points were plotted on the printed models and a 3D coordinate digitizing arm (Microscribe) was used for precisely determining the 3D (x-y-z) coordinates of each point before and after the osteotomies. Six variations of second metatarsal osteotomies were performed using microsagittal saw and fixed using a 2.4 mm cannulated screw. The following osteotomy variations were performed with 3 and 5 mm translation or wedge resection for each patient model: (1) Classic Weil osteotomy performed at 15° and 25° to the plantar surface; (2) Classic Weil osteotomy performed at 15° and 25° using a double saw blade technique; (3) Classic Weil osteotomy performed at 25° and then a parallel block of 3 or 5 mm was removed; (4) Distal closing wedge osteotomy of the MH at 25°; (5) Proximal closing wedge osteotomy of the MH made at 45° removing a 3 and 5 mm wedge; (6) 45 degree oblique, midshaft, metatarsal osteotomy with 3 and 5 mm of translation. The change in the length of the metatarsal, and vertical and medio-lateral translation of the metatarsal head was calculated then normalized by the osteotomy translation distance. A general linear model with correlated errors and Bonferroni correction was used to assess differences between osteotomies. Results: The maximum metatarsal length shortening per millimeter translation was observed in osteotomy 3- 5 mm block (2.6 mm STD=2.1), while osteotomy 1- 15° caused the least (1.1 mm STD=0.6). Maximum dorsiflexion of the MH occurred with osteotomy 5- 5 mm wedge, 13.2 mm (STD= 4.9 mm) and minimum with osteotomy1- 25°, 0.5 mm (STD= 1.4 mm). No MH plantarflexion was noted with any of the osteotomies. The oblique midshaft osteotomies caused lateral translation of the metatarsal head significantly different from the controls (P &lt;0.05) although not statistically different from one another (2.4 mm vs 4.3 mm). Conclusion: Discussion: Our data shows maximal change in length/millimeter translation by performing a classic Weil osteotomy at 25° to the plantar surface of the foot, 5 mm block resection and then translating 4 mm. This osteotomy also caused the most effective dorsal translation of the MH, thereby making it the most effective osteotomy in terms of affecting both length and MH vertical orientation. Should dorsiflexion of the MH be the surgeon’s only goal, then the proximal closing wedge osteotomy had the greatest impact while minimally changing overall length. With this knowledge, surgeons can tailor operations based on the direction and degree of correction needed to be achieved.

Lateral talocalcaneal ligament substitution for calcaneofibular ligament difficient chronic ankle lateral instability

Category: Ankle, Hindfoot, Sports, Trauma Introduction/Purpose: Introduction: Treatment of chronic ankle lateral instability associated with defective calcaneofibular ligament via tendon reconstruction or artificial grafts has several disadvantages. The method of substitution with lateral talocalcaneal ligament has never been reported. Purpose: To investigate the role of lateral talocalcaneal ligament substitution for the treatment of chronic ankle lateral instability associated with defective calcaneofibular ligament. Methods: Repair of ankle lateral ligament was performed on 32 patients with chronic ankle instability. The mean age was 26.4±8.7 years. The calcaneofibular ligament was absent in all the patients and was confirmed surgically. The calcaneofibular ligament was repaired via transfer of talar insertion of the lateral talocalcaneal ligament. Patients were followed up for an average of 22.3±4.0 months. AOFAS, Mazur and Tegner scores, objective examinations (anterior drawer test and varus stress test) and re-injury were assessed before and after the operation. The anterior translation distance of the talus and the talar tilt angle were also measured. Results: In all the patients, postoperative AOFAS, Mazur and Tegner scores were significantly improved. Postoperative evaluation (drawer test and lateral stress test) yielded negative results. The anterior translation distance was reduced from 4.9±1.0 mm to 2.0±0.8 mm. The talar tilt angle was reduced from 12.7º±2.5º to 5.0º±1.4º. The average satisfaction score was 7.4. No subjective instability or re-injury, subtalar joint (tarsal sinus) pain or/and instability occurred. Conclusion: Lateral talocalcaneal ligament substitution was effective against chronic ankle lateral instability associated with the absence of calcaneofibular ligament, without any significant effect on subtalar joint clinically.

First-in-human Phase 1 CRISPR Gene Editing Cancer Trials: Are We Ready?

A prospective first-in-human Phase 1 CRISPR gene editing trial in the United States for pa-tients with melanoma, synovial sarcoma, and multiple myeloma offers hope that gene editing tools may usefully treat human disease. An overarching ethical challenge with first-in-human Phase 1 clinical trials, however, is knowing when it is ethically acceptable to initiate such trials on the basis of safety and effi-cacy data obtained from pre-clinical studies. If the pre-clinical studies that inform trial design are them-selves poorly designed – as a result of which the quality of pre-clinical evidence is deficient – then the ethical requirement of scientific validity for clinical research may not be satisfied. In turn, this could mean that the Phase 1 clinical trial will be unsafe and that trial participants will be exposed to risk for no potential benefit. To assist sponsors, researchers, clinical investigators and reviewers in deciding when it is ethically acceptable to initiate first-in-human Phase 1 CRISPR gene editing clinical trials, structured processes have been developed to assess and minimize translational distance between pre-clinical and clinical research. These processes draw attention to various features of internal validity, construct validi-ty, and external validity. As well, the credibility of supporting evidence is to be critically assessed with particular attention to optimism bias, financial conflicts of interest and publication bias. We critically ex-amine the pre-clinical evidence used to justify the first-in-human Phase 1 CRISPR gene editing cancer trial in the United States using these tools.We conclude that the proposed trial cannot satisfy the ethical requirement of scientific validity because the supporting pre-clinical evidence used to inform trial design is deficient.

In Response

We read the letter by Liang et al1 with intense interest for which, in addition to their insightful comments, we thank them. The anatomical and physiological mechanisms underlying difficult laryngoscopy remain poorly understood. Mandibular condylar mobility, mouth opening, and angle of mouth opening may be influenced by one another2 and may have influence on laryngoscopy.3,4 However, the most dominant factor among the 3 remains undetermined. As Liang et al have deduced, with the same angle of mouth opening, the larger condylar translation results in a smaller mouth opening. However, whether the angles are equal during this process has yet to be ascertained. The occurrence and degree of extra condylar translation during laryngoscopy remain unknown. In addition, whether condylar translations remain the same when the mouth is maximally opened, or lower jaw protruded (without mouth opening), or during laryngoscopy has yet to be determined. We conducted an observational study to address these questions. The mouth opening and the angles of mouth opening of 10 volunteers were measured under the following conditions: (i) with the lower jaw actively withdrawn and the mouth opened; and (ii) with the mouth maximally opened (Figure). Condylar translations were measured when the mouth was in a maximally opened position and when the lower jaw was protruded (without the mouth opening). We also observed 20 patients and measured their mouth opening when their mouths were opened voluntarily to the maximum and when they were undergoing laryngoscopy. We asked the volunteers to protrude their lower jaw under the same degree of mouth opening as in laryngoscopy (a thick tube was kept between incisors, and the thickness was equal to the average distance of mouth opening of the patients). We observed the maximum condylar translations of the volunteers under this condition. The data were tested by 1-way analysis of variance and least significant difference testing (Table).Table.: Results and Comparisons of MeasurementsFigure.: The angle measuring method of mouth opening. A, Natural position; B, position of lower jaw actively withdrawn and mouth opened; C, mouth maximally opened. Black cross: location of condyle. Angle of mouth opening in lower jaw actively withdrawn and mouth opened: angle b minus angle a; angle of mouth opening in mouth maximally opened: angle c minus angle a.Interestingly, we observed a larger angle when the mouth was opened maximally. The condylar translation distances varied when the mouth was opened under different conditions. The condylar translation distances were slightly different when the mouths of the volunteers were in a maximally opened position and under a simulated mouth opening (27 mm) as during laryngoscopy. The condylar translation distances of the volunteers were limited when the lower jaw was protruded without opening the mouth. The present data revealed that mandibular condylar mobility, mouth opening, and angle of mouth opening can be influenced by one another. Without condylar translation, the largest angle of mouth opening cannot be obtained. Likewise, without mouth opening, the largest condylar translation distance cannot be obtained. Data from the previous study2 indicate a significant positive correlation (r = 0.41, 99% confidence interval, 0.31–0.50) between the mouth opening and the condylar translation distance, even though the correlation was not high. This finding can be used to support the aforementioned statement. This result may partly explain the concern raised by Liang et al, that is, with anterior or inferior condylar translation, the angle of mouth opening can increase. The present data also reveal that the condylar translation distance under simulated mouth opening as during laryngoscopy is similar to that under the condition of a maximally opened mouth. However, the question remains whether the mandibular condyle can achieve further translation when patients are undergoing laryngoscopy and are paralyzed. Unfortunately, we did not accurately measure the condylar translation distance under the laryngoscopy condition. The measurement results were inconclusive because probe stability during laryngoscopy was difficult to maintain. To the best of our knowledge, further condylar translation is not likely to occur when patients are undergoing laryngoscopy and paralyzed, except for the patients suffering from temporomandibular joint pain. We agree with Liang et al1 that clinicians need to understand the anatomical and physiological mechanisms underlying each predicting variable. We also thank them for providing an in-depth discussion, which was not present in the original article. Weidong Yao, MDBin Wang, MDXiaoju Jin, MDDepartment of AnesthesiologyThe First Affiliated Hospital of Wannan Medical CollegeWuhu, China Yuanhai Li, MD, PhDDepartment of AnesthesiologyThe First Affiliated Hospital of Anhui Medical UniversityHefei, China[email protected]

Geometric compactification of moduli spaces of half-translation structures on surfaces

In this paper, we give an equivariant compactification of the space $${\mathbb {P}}{\text {Flat}}(\Sigma )$$ of homothety classes of half-translation structures on a compact, connected, orientable surface $$\Sigma $$ . We introduce the space $${\mathbb {P}}{\text {Mix}}(\Sigma )$$ of homothety classes of mixed structures on $$\Sigma $$ , that are $${\text {CAT}}(0)$$ tree-graded spaces in the sense of Drutu and Sapir, with pieces which are $${\mathbb {R}}$$ -trees and completions of surfaces endowed with half-translation structures. Endowing $${\text {Mix}}(\Sigma )$$ with the equivariant Gromov topology, and using asymptotic cone techniques, we prove that $${\mathbb {P}}{\text {Mix}}(\Sigma )$$ is an equivariant compactification of $${\mathbb {P}}{\text {Flat}}(\Sigma )$$ , thus allowing us to understand in a geometric way the degenerations of half-translation structures on $$\Sigma $$ . We finally compare our compactification to the one of Duchin–Leininger–Rafi, based on geodesic currents on $$\Sigma $$ , by the mean of the translation distances of the elements of the covering group of $$\Sigma $$ .

Distance of translation as a predictor of failure of fixation in paediatric supracondylar fractures.

Introduction This study investigates the influence of incomplete reduction of supracondylar fractures on the incidence of loss of reduction requiring reoperation Materials and methods A review of 107 consecutive patients presenting with supracondylar fractures treated with closed reduction and Kirschner wire stabilisation, between January 2011 and March 2013, was conducted. The mean age was 5 years (range 10 months to 12 years). Pre-, intra- and postoperative radiographs were reviewed. All patients who had failure of fixation requiring revision surgery were identified. Results Ninety-nine patients had an initial adequate radiographic reduction. Of these, one (1%) required revision surgery. Eight patients had an initial incomplete radiographic reduction and, of these, six (75%) required revision surgery (P<0.0001). Discussion Supracondylar fractures treated with closed reduction and K wire stabilisation require adequate intraoperative reduction. Incomplete reduction should not be accepted, as despite the bones potential to remodel, the risk of further loss of reduction is high, requiring reoperation.

Evaluation of techniques for navigation of higher-order ambisonics

Metrics are presented that assess spectral coloration and localization errors incurred by navigational techniques for higher-order ambisonics. Previous studies on the coloration induced by such navigational techniques have been largely qualitative, and the accuracy of previously-used localization models in this context is unclear. The presented metrics are applied in numerical simulations of navigation over a range of translation distances. Coloration is predicted using an auditory filter bank to compute the spectral energy differences between the test and reference signals in critical bands, and localization is predicted using a precedence-effect-based localization model. Coloration and localization errors are also measured through corresponding binaural-synthesis-based listening tests, wherein subjects are first asked to rate the induced coloration relative to reference and low-pass-filtered “anchor“ signals, and subsequently judge source position. Relationships are drawn between the metrics and the results of the listening tests in order to validate the predictive capabilities of the metrics.

Evaluation of a new method to determine the tibial tuberosity advancement distance required to reduce the patellar tendon-tibial plateau angle to 90° with the modified Maquet technique in dogs.

OBJECTIVE To assess use of a new radiographic method to determine the distance by which the tibial tuberosity should be advanced to reduce the patellar tendon-tibial plateau angle (PTA) to 90° by means of the modified Maquet technique (MMT) in dogs. SAMPLE 24 pelvic limbs from 12 adult medium-sized to large-breed canine cadavers. PROCEDURES Radiographs of stifle joints at 135° extension in true lateral position were used to determine tibial tuberosity advancement distances for use in the MMT. A method was devised to incorporate the planned osteotomy axis; distal patellar translations of 0, 3, 5, or 10 mm; and advancement cage implant application level along the osteotomy site in advancement planning measurements. Concordance correlation coefficients (CCCs) were calculated to compare these adjusted advancement measurements with true advancement measurements obtained for the same joints in another study after treatment by MMT. Intraobserver, interobserver, and total agreement for selected measurements were determined by assessment of CCCs for results obtained by 3 blinded observers. RESULTS Agreement between true advancement measurements and measurements obtained with osteotomy axis and cage position method calculations that incorporated a 5-mm distal patellar translation distance was excellent (CCC, 0.96). Intraobserver and interobserver agreements for the planning measurements evaluated were good to excellent (CCC, 0.83 to 0.96). CONCLUSIONS AND CLINICAL RELEVANCE Results suggested that the osteotomy axis and cage position method incorporating a 5-mm distal patellar translation distance has the potential to improve success rates for achieving a PTA of 90° in medium-sized to large-breed dogs undergoing MMT for treatment of cranial cruciate ligament rupture. Further research is warranted.

Analysis of the cranio-cervical curvatures in subjects with migraine with and without neck pain

ObjectiveTo investigate the differences in head and cervical spine alignment between subjects with migraine and healthy people. DesignA cross-sectional, observational study. ParticipantsFifty subjects with migraine and 50 matched healthy controls. Main outcomes measuresThe presence of neck pain and neck pain-related disability was assessed. Four angles (high cervical angle, low cervical angle, atlas plane angle and cervical lordosis Cobb angle) as well as four distances (anterior translation distance, C0 to C1 distance, C2 to C7 posterior translation and hyoid triangle) were calculated using digitalised radiographs and analysed using K-Pacs® software. ResultsSubjects with migraine reported a longer history of neck pain symptoms, and higher pain intensity and neck-pain-related disability than controls (P<0.01). Patients exhibited a smaller anterior translation distance (mean difference: 4.9mm, 95% confidence interval 1.8 to 8.8; P<0.001) and hyoid triangle (difference: 3.0mm, 95% confidence interval 1.0 to 5.0; P=0.02) than healthy controls. When the presence or the absence of neck pain was included in the analysis, the differences did not change. Differences in anterior translation and hyoid triangle distances were considered clinically relevant for subjects with migraine suffering from neck pain. ConclusionSubjects with migraine exhibited straightening of cervical lordosis curvature. The presence of neck pain did not influence head posture in subjects with and without migraine.

Tumor motion changes in stereotactic body radiotherapy for liver tumors: an evaluation based on four-dimensional cone-beam computed tomography and fiducial markers

BackgroundFor stereotactic body radiation therapy (SBRT) of liver tumors, tumor motion induced by respiration must be taken into account in planning and treatment. We evaluated whether liver tumor motion at the planning simulation represents liver tumor motion during SBRT, and estimated inter- and intrafractional tumor motion changes in patients undergoing liver SBRT.MethodsTen patients underwent four-dimensional cone-beam computed tomography (4D-CBCT) image-guided liver SBRT with abdominal compression (AC) and fiducial markers. 4D-CBCT was performed to evaluate liver tumor motion at the planning simulation, pre-, and post-SBRT. The translational distances at the center position of the fiducial markers from all 10 phases on the 4D-CBCT images were measured as the extent of the liver tumor motion in the left-right (LR), anterior-posterior (AP), and superior-inferior (SI) directions. Pearson correlation coefficients were calculated to evaluate the correlation between liver tumor motion of the planning simulation and the mean liver tumor motion of the pre-SBRT. Inter- and intrafractional liver tumor motion changes were measured based on the 4D-CBCT of planning simulation, pre-, and post-SBRT. Significant inter- and intrafractional changes in liver tumor motion were defined as a change of >3 mm.ResultsThe mean (± SD) liver tumor motion of the planning simulation 4D-CBCT was 1.7 ± 0.8 mm, 2.4 ± 2.2 mm, and 5.3 ± 3.3 mm, in the LR, AP, and SI directions, respectively. Those of the pre-SBRT 4D-CBCT were 1.2 ± 0.7 mm, 2.3 ± 2.3 mm, and 4.5 ± 3.8 mm, in the LR, AP, and SI directions, respectively. There was a strong significant correlation between liver tumor motion of the planning simulation and pre-SBRT in the LR (R = 0.7, P < 0.01), AP (R = 0.9, P < 0.01), and SI (R = 0.9, P < 0.01) directions. Significant inter- and intrafractional liver tumor motion changes occurred in 10 and 2% of treatment fractions, respectively.ConclusionsLiver tumor motion at the planning simulation represents liver tumor motion during SBRT. Inter- and intrafractional liver tumor motion changes were small in patients with AC.

Investigation of friction induced vibration in lead screw system using FE model and its experimental validation

Finite Element Method (FEM) is proposed to model the friction-induced vibration in the gear system with a lead screw and nut. In order to validate it, the experiment was conducted by using the lead screw test set-up. In the frequency spectrogram, there were two distinctively different patterns of the unstable modes: a mode where the frequency significantly changed and another where the frequency remained almost unchanged. Under a constant friction coefficient, the complex eigenvalue analysis in the FE model demonstrated that the system frequencies altered with respect to the transfer distance of the nut. The unstable modes were found to occur due to mode-coupling between the paired bending modes of the screw. Meanwhile, an unstable mode in which the frequency showed little changes in relation to the translation distance of the nut, was found to be an unstable torsion mode, which was caused by the negative friction-velocity slope.

TMJ energy densities in healthy men and women.

Cartilage fatigue, due to mechanical work, may account for the early development of degenerative joint disease (DJD) in the temporomandibular joint (TMJ), and why women are three times more likely to be afflicted. This study tested for gender differences in mechanical energy densities in women and men with healthy TMJs. Eighteen women and eighteen men gave informed consent. Research diagnostic criteria including imaging were used to ensure that subjects' TMJs were normal, without disc displacement or signs of DJD. Numerical modeling determined TMJ loads (Fnormal). Jaw tracking and three-dimensional dynamic stereometry characterized individual-specific data of stress-field dynamic mechanics during 10 symmetrical jaw closing cycles. These data were used to estimate tractional forces (Ftraction). Energy densities were then calculated, where: Energy Density=W/Q (W=work done or mechanical energy input=Ftraction*distance of stress-field translation, Q=volume of cartilage). Two-way analysis of variance (ANOVA) and follow-up two-group comparisons tested mean energy densities for ipsilateral and contralateral TMJs in women vs men. Mean energy densities ± standard deviations in ipsilateral and contralateral TMJs in women were 9.0±9.7 and 8.4±5.5mJ/mm3, respectively, and were significantly larger (P=0.004 and 0.001, respectively) compared to ipsilateral and contralateral TMJs in men, which were 5.6±4.2 and 6.3±4.2mJ/mm3, respectively. Energy densities were significantly larger in healthy TMJs of women than men. Larger TMJ energy densities during normal jaw functions could predispose earlier mechanical fatigue of the TMJ disc.