Ligament Length Research Articles

Imaging in Lisfranc injury: a systematic literature review.

To systematically review current diagnostic imaging options for assessment of the Lisfranc joint. PubMed and ScienceDirect were systematically searched. Thirty articles were subdivided by imaging modality: conventional radiography (17 articles), ultrasonography (six articles), computed tomography (CT) (four articles), and magnetic resonance imaging (MRI) (11 articles). Some articles discussed multiple modalities. The following data were extracted: imaging modality, measurement methods, participant number, sensitivity, specificity, and measurement technique accuracy. Methodological quality was assessed by the QUADAS-2 tool. Conventional radiography commonly assesses Lisfranc injuries by evaluating the distance between either the first and second metatarsal base (M1-M2) or the medial cuneiform and second metatarsal base (C1-M2) and the congruence between each metatarsal base and its connecting tarsal bone. For ultrasonography, C1-M2 distance and dorsal Lisfranc ligament (DLL) length and thickness are evaluated. CT clarifies tarsometatarsal (TMT) joint alignment and occult fractures obscured on radiographs. Most MRI studies assessed Lisfranc ligament integrity. Overall, included studies show low bias for all domains except patient selection and are applicable to daily practice. While conventional radiography can demonstrate frank diastasis at the TMT joints; applying weightbearing can improve the viewer's capacity to detect subtle Lisfranc injury by radiography. Although ultrasonography can evaluate the DLL, its accuracy for diagnosing Lisfranc instability remains unproven. CT is more beneficial than radiography for detecting non-displaced fractures and minimal osseous subluxation. MRI is clearly the best for detecting ligament abnormalities; however, its utility for detecting subtle Lisfranc instability needs further investigation. Overall, the available studies' methodological quality was satisfactory.

Effect of the Processing-Induced Morphology on the Mechanical Properties of Biodegradable Extruded Films Based on Poly(lactic acid) (PLA) Blends

Biodegradable films based on poly(lactic acid) blends were obtained by cast extrusion. Their tensile and fracture behavior was investigated and the effect of the processing conditions through the extrusion rolling speed on this behavior was analyzed. In uniaxial tensile tests, all films presented completely ductile behavior exhibiting a defined yield point, strain softening after this point and a plateau before fracture. Fracture behavior was determined through quasi-static fracture tests on deeply double edge notched tensile specimens. The film obtained at the lowest rolling speed exhibited completely ductile behavior hence, the Essential Work of Fracture methodology was applied to characterize its fracture. The film processed at intermediate rolling speed, on the other hand, presented ductile fracture or ductile instability depending on the ligament length and the film obtained with the highest rolling speed exhibited a transition regime fracture. In order to compare the fracture behavior of the different films, the J-integral at maximum load Jmax was adopted. Differences in the films fracture behavior were correlated to the processing-induced morphology.

Development and validation of subject-specific pediatric multibody knee kinematic models with ligamentous constraints

Computational knee models that replicate the joint motion are important tools to discern difficult-to-measure functional joint biomechanics. Numerous knee kinematic models of different complexity, with either generic or subject-specific anatomy, have been presented and used to predict three-dimensional tibiofemoral (TFJ) and patellofemoral (PFJ) joint kinematics of cadavers or healthy adults, but not pediatric populations.The aims of this study were: (i) to develop subject-specific TFJ and PFJ kinematic models, with TFJ models having either rigid or extensible ligament constraints, for eight healthy pediatric participants and (ii) to validate the estimated joint and ligament kinematics against in vivo kinematics measured from magnetic resonance imaging (MRI) at four TFJ flexion angles.Three different TFJ models were created from MRIs and used to solve the TFJ kinematics: (i) 5-rigid-link parallel mechanism with rigid surface contact and isometric anterior cruciate (ACL), posterior cruciate (PCL) and medial collateral (MCL) ligaments (ΔLnull), (ii) 6-link parallel mechanism with minimized ACL, PCL, MCL and lateral collateral ligament (LCL) length changes (ΔLmin) and (iii) 6-link parallel mechanism with prescribed ACL, PCL, MCL and LCL length variations (ΔLmatch). Each model’s geometrical parameters were optimized using a Multiple Objective Particle Swarm algorithm.When compared to MRI-measured data, ΔLnull and ΔLmatch performed the best, with average root mean square errors below 6.93° and 4.23 mm for TFJ and PFJ angles and displacements, respectively, and below 2.01 mm for ligament lengths (<4.32% ligament strain). Therefore, within these error ranges, ΔLnull and ΔLmatch can be used to estimate three-dimensional pediatric TFJ, PFJ and ligament kinematics and can be incorporated into lower-limb models to estimate joint kinematics and kinetics during dynamic tasks.

Correlation Analysis of the Anterolateral Ligament Length with the Anterior Cruciate Ligament Length and Patient\u2019s Height: An Anatomical Study

The aim of this study was to evaluate the anatomical characteristics of the anterolateral ligament of the knee (ALL) with the focus on potential gender differences. The ALL length and the length of the lateral collateral ligament (LCL) were taken in extension. The length of the anterior cruciate ligament (ACL) was measured at 120° flexion. We correlated the length of the ALL with the LCL and ACL with respect to potential gender differences. The ALL was significantly (p = 0.044) shorter in females (mean length: 32.8 mm) compared to males (mean length: 35.7 mm). The length of the ALL correlated significantly positively with the lengths of the ACL (p < 0.001) and the LCL (p < 0.001). There was no significant correlation with the total leg length (TLL) (p = 0.888) and body size (p = 0.046). Furthermore, TLL and donor size correlated significantly positively (p < 0.001). The ALL length correlated significantly positively with the ACL and the LCL length. The ALL length did neither correlate with the TLL nor the donor size. This fact may contribute to planning of graft harvesting in the upcoming techniques for ALL reconstruction.

Reliability of ultrasonography measurement of the anterior talofibular ligament (ATFL) length in healthy subjects (in vivo), based on examiner experience and patient positioning

BackgroundThe most common cause of ankle injury is the supination trauma, inflicting a partial or complete rupture of the anterior talofibular ligament (ATFL). Among conventional diagnostic tools and procedures of sports injuries, the method of stress-ultrasonography is reportedly a promising diagnostic tool for examining injuries of the lateral ligaments of the ankle. Preceding studies predominantly examined the comparability of stress-ultrasonography and other established diagnostic tools in terms of efficacy, viability and quality. The purpose of this study was to assess the reliability of stress-ultrasonography of the ATFL based on varying examiner experience and patient positioning.MethodSixteen healthy subjects were examined by four examiners with differing levels of skill and experience in ultrasonography, ranging from laymen to specialist. Measurements were recorded and interrater correlation coefficient (ICC) was applied in four positions, including a neutral position (A), medial rotation (B), plantar flexion (C) and inversion of the foot (D).ResultsThe length of the ATFL was 14.958 ± 2.145 mm in position A, 15.886 ± 1.994 mm in position B, 16.270 ± 1.858 mm in position C and 15.170 ± 1.781 mm in position D. The average length change was 0.928 ± 0.804 mm (6.656 ± 6.299%) in position B, 1.313 ± 1.266 mm (9.746 ± 9.484%) in position C and 0.213 ± 1.807 mm (2.604 ± 12.308%) in position D. The correlation of the combined results of all four investigators was 0.333 for position A, 0.386 for position B, 0.320 for position C and 0.517 for position D. The highest ICC (0.811) was recorded between the orthopedic specialist and the radiology specialist. The lowest ICC (0.299) was recorded between the laymen and the radiology specialist.ConclusionThe reliability of the ATFL examination seems to be exceedingly dependent on the examiner’s experience and skill in ultrasonographic (US) diagnostic. Moreover, the inversion positioning of the foot, described by the European Society of Musculoskeletal Radiology (ESSR) yielded the highest measurement reliability.

Study of Pterygospinous and Pterygoalar Bars in Relation to Foramen Ovale in Dry Human Skulls

Abstract Background Anatomical knowledge of bony bridges around the foramen ovale may be helpful for diagnostic and invasive neurosurgical procedures like electroencephalogram analysis, trigeminal rhizotomy, biopsy of cavernous sinus tumors, and mandibular nerve block.Lateral pterygoid plate forms an important landmark for mandibular anesthesia; therefore, any variation related to lateral pterygoid plate is likely to create confusion during the maneuver of anesthesia. Aims and Objective The aim of the study was to explore any bony obstacle within and around Foramen ovale. Obstacles in form of ossified complete or incomplete ligaments. Additional foramina formed by ligaments or any bony enlargement might disturb the structures passing through the Foramen ovale. Methods Around 530 dried crania (from medical colleges in Uttarakhand and Uttar Pradesh) were observed to find ossified ligaments and foramen formed by them. Crania associated with bilateral enlarged lateral pterygoid plate other than the average width of 1.5 cm were included in this study. Length of ligaments and width of pterygoid plate were measured by digital Vernier calipers. Results Out of 530 crania, unilateral 52 ossified pterygospinous ligament (incomplete 31 and complete 21) were observed. Among them some rare variation was found along with ossified pterygospinous and pterygoalar ligament, one cranium along with unilateral pterygospinous bar was also having bar within foramen ovale, forming an accessory osseous compartment, found to be rare kind of variation. Another unilateral complete pterygospinous bar was enclosing two foramens instead of one. Only single cranium was found to have pterygoalar bar, related medial to foramen ovale. One cranium was associated with bilateral enlarged lateral pterygoid plate (i.e., 2.5 cm) was also found to be obliterating the space, that is, retropharyngeal and parapharyngeal space for surgeons. Conclusion This study would provide the anatomical knowledge of these bony bridges around the foramen ovale and may be helpful for diagnostic and neurosurgical procedure like microvascular decompression by percutaneous trigeminal rhizotomy for trigeminal neuralgia, percuatneous biopsy of cavernous sinus tumor and mandibular nerve block by lateral subzygomatic route. Thus, lateral pterygoid plate forms an important landmark for mandibular anesthesia.

Anatomical variations of the inguinal morphometric features in patients with inguinal hernia and its association with the type of inguinal hernia: a prospective clinical study

Background: Variations of inguinal canal and inguinal nerves are not uncommon. Knowledge about those variations is important to avoid inadvertent injury to the vital structures and to prevent recurrence.Methods: This prospective clinical study included all patients undergoing open inguinal hernia repair. Laparoscopic hernia repair, emergency surgery for complication and recurrent inguinal hernia were excluded. Parameters studied include interspinous distance, length and obliquity of inguinal ligament, attachment of conjoint tendon, condition of transversalis fascia and position and variations of ilioinguinal nerve.Results: The study included 192 patients. The mean interspinous distance (ISD) was 22±3.45 cm (CI: 30-32). ISD was not significant different among the two types of hernia. The mean length of internal oblique on inguinal ligament from anterior superior iliac spine was significantly longer in patients with indirect inguinal hernia (4±0.791 vs. 4.27±1.34; p=0.000). Significant patients in the direct hernia had weak transversalis fascia ((95% vs. 43%). 80% of the patients with direct hernia had defect in the transversalis fascia compared to only 8.8% in the indirect hernia. The difference is statistically significant. The nerve variation was present in only 1.3% in direct hernia group compared to 3.5% in the indirect hernia group.Conclusions: It was observed that the type of hernia did not significantly influenced by the length of inguinal ligament, the mean distance of midinguinal point, obliquity of the inguinal ligament. The nerve variation was present in only 1.3% in direct hernia group compared to 3.5% in the indirect hernia group.

CADAVERIC STUDY OF MORPHOMETRIC ANALYSIS OF ANTERIOR CRUCIATE LIGAMENT AND ITS SIGNIFICANCE

Introduction: To determine the accurate morphometric data pertaining to the Anterior cruciate ligaments in relation to the south Indian population. Aims And Objectives: To analyse the following parameters of Anterior cruciate ligament of the knee joint. Length and Width of Anterior Cruciate Ligaments as well as the extent of their variations. Methods & Materials: The study was carried out in the Department of Anatomy of Govt. Mohan Kumaramangalam Medical College Hospital, Salem. Subjects having no obvious macroscopic deformities of their knee joints and ages ranging between 30 years to 60 years of both sexes were only chosen. 30 knee joints belonging to 15 cadavers matching the above criteria were dissected for the study. Result & Analysis: The mean length of the ACL of left side was recorded to be 28.06mm and the mean width of the ACL in its middle third was recorded to be 10.33mm in the Left side. The mean length of the ACL for the right side was found to be 28.53mm and mean width of the ACL in its middle third on the right side was found to be 10.23mm. Conclusion: This study will provide valuable information related to the length and width of the Anterior cruciate ligament in South Indian population for cruciate ligament reconstruction. Keywords: Morphometry, cruciate ligaments, knee joint

Radiographic evaluation of patellar ligament length after tibial plateau leveling osteotomy in dogs

To radiographically compare patellar ligament length (PLL) in dogs undergoing tibial plateau leveling osteotomy (TPLO) for unilateral cranial cruciate ligament rupture at preoperative, postoperative, and follow-up evaluations. 105 dogs that underwent TPLO for unilateral cranial cruciate ligament rupture at a referral veterinary hospital from October 1, 2008, through November 30, 2017. Medical records were reviewed to obtain information on dog signalment, surgical procedure, and radiographically measured PLL at preoperative, postoperative, and follow-up evaluations. Dogs undergoing TPLO had a shorter PLL at the postoperative and follow-up evaluations, compared with the PLL at the preoperative evaluation. Mean ± SD overall unadjusted PLL decreased significantly by 2.3 ± 3.4% between the preoperative and postoperative evaluation and by 2.8 ± 3.9% between the preoperative and follow-up evaluation. The PLL did not differ significantly between the postoperative and follow-up evaluation; mean PLL decreased by 0.4 ± 3.8% between the postoperative and follow-up evaluation. The PLL was shorter after TPLO in dogs, which was similar to changes observed for humans after high tibial osteotomy procedures. Further evaluation of clinical assessments, joint mobility, ultrasonographic assessments, and kinematic results are needed to determine the relevance of the PLL and whether a decrease in ligament length results in decreased mobility and persistent lameness in dogs, as has been reported for humans.

Accuracy of Ultrasound Imaging of the Lisfranc Joint Complex

Lisfranc injuries account for 1 in 55,000 injuries yearly and are associated with poor outcomes and high complication rates. Superficially connecting the medial cuneiform and second metatarsal, the dorsal Lisfranc ligament is easily visualized with ultrasound. Ultrasound can provide quick, cost effective diagnosis but is not currently standard in clinical practice. PURPOSE: This study sought to compare measurement accuracy of the dorsal Lisfranc ligament using ultrasound, external software, and gross anatomic dissection, with an additional anatomic study of the joint complex. METHODS: Ultrasound images of 22 embalmed cadaveric feet (13 male, 9 female, 79.5±13.3 years) were obtained using a 6-13MHz linear array. Dorsal Lisfranc ligament length and joint space were measured and compared between methodologies. Images were also re-measured using ImageJ software. Specimens were dissected to evaluate dorsal, interosseous, and plantar Lisfranc ligaments. Joint complex morphology was documented. RESULTS: Ultrasound (8.39±1.26 mm) and ImageJ measurements (8.26±1.76 mm) of the dorsal Lisfranc ligament did not differ significantly, but both were significantly different (p < 0.05) than gross dissection (10.8± 1.84 mm). There were no significant differences in dorsal joint space measures between ultrasound (2.19±0.49 mm) and ImageJ (2.05±0.52 mm), but both were significantly different (p < 0.05) than dissection measurements (1.04±0.24 mm). The dissected dorsal and interosseous ligaments had consistent morphology, whereas the plantar ligament demonstrated a Y- and a fan-shaped variant. A connection between the interosseous and plantar ligaments was present in 64% of dissections. CONCLUSION: The dorsal Lisfranc ligament is easily visualized on ultrasound with 23% of the ligament not clearly visible at the peripheral bony attachments. While visually underrepresented on ultrasound, measurements were consistent. Radiographic joint space measurement remains the diagnostic gold standard. Further research should focus on using ultrasound to measure both bony and ligament integrity. Ligament echogenicity provides additional diagnostic information to assess more subtle joint injuries. Additionally, the plantar Lisfranc ligament variability may impact the stability of the joint in some patients.

Linear type trait evaluation of firstborns of Ukrainian Black-and-White Dairy breed depending on the body build

It has been experimentally proven that the strength and direction of the connection between the linear type traits evaluation of the Ukrainian black-and-white dairy breed cows and their body build depends on the type of the build and the sign of the exterior. The study was conducted in 2018 on a breeding plant of the Ukrainian Black-and-White Dairy breed SPC named Shchorsa in Kiev region (n=89). Differentiation of cows on types of their body build was conducted by the method proposed by Chernenko (low-capacity, mid-capacity and high-capacity types) and Kolesnik (by the massiveness index – on the friable and dense, the bone index – delicate and rough, the wide-breast and wide-rump indices – on narrow-body and wide-body types). It was found that the cow-heiferswere well-developed, had intermediate stature and optimum body condition score, deep body, and wide, slight slope rump. They alsohad desirable rear legs, set and foot angle but some toe-out, the udder was well-balanced. Under the good total score of the exterior of studied cows there were some animals with short stature (134– 136 cm), very wide rump, straight rear legs side view and toe-out, extremely steep foot angle, loose fore udder attachment, deep udder below hocks and front teat placement inside of quarter. The degree of development of the studied linear traits of cow-heifers confirms their in-herd variability. The variability of the exterior traits varies from 10,7 % (body depth) to 38,6 % (stature). In addition to the stature of a significant variability was characterized of angularity (22,4 %), rear legs set (22,5 %), body condition score (21,8 %), as well as traits that describe udder: rear udder attachment (31,4 %), udder depth (32,6 %) and front and rear teat position (31,3 % and 25,1 %, respectively). The high variability of linear traits indicates the possibility of effective their selection. As a result of the research, it has been established that the strength and direction of the correlations between the linear type traits evaluation of Ukrainian Black-and-White Dairy breed cows and the type of their body build depends on the type of the body build and the linear trait. The low-, mid- and high-capacity bodies build types (according to Chernenko) reliably correlate with chest width (r=0,58) and body depth (r=0,48), rear legs rear view (r=0,30), the central ligament (r=0,28), udder depth (r =-0,22) and teat length (r=0,25), P˂0,01–0,001. Friable and dense bodies build (according to Kolesnik) were most strongly associated with stature (r=-0,28), chest width (r =-0,70), and body depth (r=-0,38), as well as with rear legs rear view (r=-0,23), P˂0,05...0,001; delicate and rough bodies build – with stature (r=-0,51), angularity (r=-0,22),rump width (r=-0,35), udder depth (r=-0,27) and rear udder attachment (r =0,20), P ˂ 0,05–0,001; narrow-body and wide-body types – with chest width (r=0,30) and rump width (r=0,23), P˂0,05–0,01. Linear type trait evaluation of cows depends on the body build. The strength and direction of the correlations between types of body build and linear traits showed that the most informative is the classification of the body build by low-, mid- and high-capacity according to Chernenko – on the average η2x=17,5 %. The less informative – by narrow-body and wide-body types according to Kolesnik – η2x=7,6 %. The classification of cows on delicate-rough, narrow-body and wide-body types (according to Kolesnik) according to informativeness and reliability can have the intermediate position – η2x=10,0–11,5 %. The strongest influence on the body build has the cows’ height (η2x=27,9 % on average for all studied types of body build), chest width (η2x=33,5 %), body depth (η2x=21,8 %), rump width (η2x=24,1 %) and rear legs (η2x=18,7 %). Key words: cows, linear type trait evaluation, body build, correlation, power of influence.

Age-related changes in inguinal region anatomy from 0 to 19 years of age.

Knowledge of the age-related changes in inguinal region anatomy is essential in pediatric urological and abdominal surgery, yet little is published. This study aimed to determine the position of inguinal region structures and growth of the surrounding pelvis and inguinal ligament in subjects from 0 to 19 years of age. Anonymized contrast-enhanced CT DICOM datasets of 103 patients (63 male: 40 female) aged from 0 to 19 years had left and right sides analyzed by three independent observers. Exclusion criteria were applied. Growth of the pelvis and inguinal ligament were determined using fixed bony reference points. The position of the deep inguinal ring and femoral vasculature were determined as ratio of inguinal ligament length, measured from the anterior superior iliac spine. Growth of the pelvis in vertical and horizontal dimensions and of the inguinal ligament followed a positive polynomial relationship with increasing age, with no observed increase in growth rate during puberty. From 0 to 19 years, the deep inguinal ring moved superolaterally with respect to the inguinal ligament (from 0.74 to 0.60 of the distance along the inguinal ligament) and the femoral artery and vein moved medially (from 0.50 to 0.58, and 0.61 to 0.65 of the distance along the inguinal ligament, respectively). The position of the femoral artery, vein, and deep inguinal ring followed a logarithmic relationship with age. No significant left:right side or male:female differences were observed. From 0 to 19 years of age the femoral vasculature and deep inguinal ring change position as the pelvis grows around them. Clin. Anat. 32:794-802, 2019. © 2019 Wiley Periodicals, Inc.

Three-Dimensional In Vivo Analysis of Malunited Distal Radius Fractures With Restricted Forearm Rotation.

Malunited distal radius fractures (DRFs) occasionally restrict forearm rotation, but the underlying pathology remains unclear. We aimed to elucidate the mechanism of rotational restriction by retrospective analysis of 23 patients with unilateral malunited DRFs who presented restricted forearm rotation. We conducted computed tomography during forearm rotation on both sides. Three-dimensional (3D) bone surface models of the forearm were created, and 3D deformity of the distal radius, translation of the distal radius relative to the ulna, distal radioulnar joint (DRUJ) contact area, and estimated path length (EPL) of distal radioulnar ligaments (DRUL) during forearm rotation were evaluated. In total, 18 patients had dorsal angular deformities (DA group) and five had volar angular deformities (VA group). In the DA group, the closest point between the distal radius and ulna on DRUJ was displaced to the volar side during supination and pronation (p < 0.001); DRUJ contact area was not significantly different between the DA and normal groups. In bone-ligament model simulation, the EPL of dorsal DRUL was longer in the DA group than in the normal group (p < 0.001); opposite phenomena were observed in the VA group. In the DA group, translation of the distal radius in a volar direction relative to the ulna during pronation was impaired presumably due to dorsal DRUL tightness. Anatomical normal reduction of the distal radius by corrective osteotomy may improve forearm rotation by improving triangular fibrocartilage complex tightness and normalizing translation of the distal radius relative to the ulna. © 2019 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 37:1881-1891, 2019.

Can the Etiopathogenesis of Chiari Malformation Be Craniocervical Junction Stabilization Difference? Morphometric Analysis of Craniocervical Junction Ligaments

The craniocervical junction permits a certain amount of mobility for the cervical spine. The biomechanical properties of occipital bone-atlas joint mainly depend on the bony structure, and atlas-axis joint biomechanical properties mainly depend on ligamentous structure. The underlying etiologic factor of Chiari malformation (CM) is debatable. Nowadays, some researchers argue that stabilization difference is one of the suspicious factors for etiopathogenesis. We aim to analyze the ligamentous morphometric differences of CM. Magnetic resonance images of 93 adult healthy subjects (n= 93) without any craniocervical junction development abnormalities and 25 (n= 25) adult patients with craniocervical junction development abnormalities (Arnold CM) were evaluated. Length, width, and length-width ratios of ligaments were evaluated. Length of transverse ligament (mean: 23 ± 3.6 [range: 12.1-31.4]) in the normal population was significantly longer than transverse ligament length in CM patients (mean: 21.3 ± 2.5 [range: 17.2-24.9]). Length of alar ligament (mean: 10.7 ± 2 [range: 5.1-15.4]) in the normal population was significantly longer than alar ligament length in CM patients (mean: 8.8 ± 3.8 [range: 1.1-16.6]) (P= 0.007). Craniocervical ligaments play an important role in maintaining stability and motion capacity of this region. This study promoted better understanding of craniocervical junction anomalies and provided data that facilitate performing more precise surgical treatment.

Three-dimensional computed tomography modeling for kinematic analysis of double-strand lateral ulnar collateral ligament reconstruction

When treating posterolateral rotatory instability, the lateral ulnar collateral ligament (LUCL) is more commonly reconstructed than the other dynamic stabilizer structures. Although numerous surgical techniques have been described for LUCL reconstruction, studies have been limited to static analyses of single-strand reconstructions. The aim of this study was to dynamically analyze the kinematics of double-strand LUCL reconstructions with 3 different configurations of graft placement: horizontal, vertical, and triangular. Five healthy elbow joints with no signs of pre-existing pathology were scanned by computed tomography, and the images were converted into 3-dimensional models. The humeral origin and ulnar insertions of the 2 ligament strands were registered in 3-matic software for the 3 graft placement configurations. A dynamic elbow joint was simulated at 1° increments throughout the motion arc. The ligament strand lengths and the difference between them were measured. The ligament lengths for each strand for the 3 graft configurations were as follows: horizontal, 31.0 ± 4.6 mm and 34.3 ± 5.0 mm; vertical, 32.5 ± 3.6 mm and 35.4 ± 4.2 mm; and triangular, 32.0 ± 4.0 mm and 33.7 ± 3.1 mm. The minimum length differences for the graft strands through the motion arc for the horizontal, vertical, and triangular graft configurations were 1.1, 0.0, and 1.0 mm, respectively. Dynamic analyses using a 3-dimensional elbow model showed that none of the configurations for double-strand LUCL reconstruction were isometric. However, the vertical double-strand configuration was nearly isometric and may therefore serve as a coequal option.

DEM modeling of crack coalescence between two parallel flaws in SiC ceramics

Abstract A discrete element model (DEM) of SiC ceramics containing two parallel flaws was used to study crack coalescence under uniaxial compression with different flaw inclination angles, ligament lengths, and ligament angles. A relationship is proposed between coalescence stress state, flaw inclination angle, and horizontal component of the ligament length during the failure process. The effects of coplanar flaws on various characteristics of the specimen, viz. compressive strength, Young's modulus, crack initiation stress, and Poisson's ratio, were studied. Coalescence modes between two parallel flaws observed in the DEM model were in good agreement with nine crack coalescence categories summarized in experimental studies. Meanwhile, the corresponding stress state at the moment of coalescence can be classified into three types – pre-peak, mid-peak, and post-peak. The results also showed that the horizontal component d of the ligament length of parallel flaws significantly influences the coalescence stress state. When parallel flaws overlap in the loading direction (d

Impact energy absorption performances of ordinary and hierarchical chiral structures

Auxetic chiral structures consisting of circular ring nodes and tangentially connected ligaments are engineered systems that exhibit excellent flexibility, vibration attenuation, impact resistance performances. In this paper, the out-of-plane dynamic crash behaviors of anti-tetrachiral, hexachiral and hierarchical chiral structures are studied. The energy absorption efficiency, plateau stress, peak stress of chiral structures with different ligament length, node radius, ligament thickness and level of structural hierarchy under different external crashing conditions are compared, and identical mass per area of different unit cell configurations are assumed. It is found that anti-tetrachiral structure is able to generate higher plateau stress and better energy absorption efficiency than hexachiral structures. Making use of the mechanical benefits of structural hierarchy, novel hierarchical chiral structures are proposed for improving the crash energy absorption abilities of chiral structures, and relations between crash energy absorption performances and unit cell geometries are explored, such as: energy absorption efficiency, plateau stress of chiral structures. Based on systematical analysis, optimized chiral and hierarchical chiral cellular structure can be designed for impact energy absorption in protective sandwich structures.

Visualization of periodic emission of drops with micro-dripping mode in electrohydrodynamic (EHD) atomization

Electrohydrodynamic (EHD) atomization could produce mono-dispersed drops in different spraying modes. The generation of drops of controllable size in the micrometer range in micro-dripping mode has been focused because of the important and broad practical applications. In present study, the periodic emission of drops from an electrified meniscus attached to the end of a capillary nozzle in micro-dripping mode and the dynamics of the ligament formation were investigated. The charge-to-mass ratio, the frequency of drops generation, dimensionless equivalent diameter, ligament length and width could be obtained under different dimensionless flow rates (q) and electric Bond numbers (BE), in which q is small but could be varied by a factor of around one hundred and BE is bound to a narrow range of order unity. The charge carried by each drop produced in present work is smaller than the fifty percent of critical value of the Rayleigh limit. Drop generation frequency with rang of a few to several hundred Hz obtained from offline analysis of time-resolved images captured by a high-speed digital camera with zoomed lens highly depends on q and BE, in which the drops produced are usually the smaller than one to ten times the diameter of the nozzle. The micro-dripping regime may be sustained and occur periodically within a certain ranges of flow rate and voltage, where the meniscus would be stretched by a tangential electric stress and further elongated by electric polarization stress and gravity, finally develops a drop ejected from the meniscus. The dimensionless equivalent diameter (dd) would increase as powers of dimensionless flow rate q, in which the correlation gives dd ∼ q0.32 for very small q and dd ∼ q0.45 for larger q. The dimensionless length ls and width ds would increase as powers of dimensionless flow rate q, in which the relation roughly could be given as ls ∼ q0.30–0.34 and ds ∼ q0.33–0.46 for very small q, while ls ∼ q0.43–0.45 and ds ∼ q0.52–0.62 for larger q. The results in present work were similar to previous studies and also existed some deviation, the possible reasons including electric field, liquid properties and viscosity and air resistance were discussed.

Effect of vitrectomy on lens suspensory ligament and depth of anterior chamber

Objective To analyze the effect of vitrectomy on lens suspensory ligament and depth of anterior chamber in cataract patients. Methods The data of 86 eyes of 80 patients with cataract from Jan.2014 to Dec.2016 were analyzed retrospectively. They were divided into operation group of 46 cases and control group of 40 cases according to the history of vitrectomy. The depth of anterior chamber was measured with ophthalmic optical biometrics, and the lens suspensory ligament was measured with panoramic ultrasound biomicroscopy. The differences were compared between the two groups. Results The average distance from ciliary process to equator of crystal and the anterior chamber depth in operation group were (1.08±0.22) mm, (3.22±0.37) mm, respectively and (0.77±0.22) mm, (3.50±0.41) mm in the control group respectively. The difference were statistically significant between the two groups (t=7.940, -3.876, P=0.000, 0.000). The difference in average length of the suspensory ligament in patients with different axial length was statistically significant (P=0.000). The difference in anterior chamber depth in patients with axial length ≥29 mm was statistically significant between the two groups (t=-4.931, P=0.000). But the difference in eye length < 29 mm was not statistically significant between the two groups (t=-0.983, -1.345, P=0.328, 0.182). Conclusion Vitrectomy can increase the length of lens suspensory ligament and reduce anterior chamber depth in cataract patients, and it has a certain relationship with the length of the eye. Key words: Cataract; Vitrectomy; Suspensory ligament, lens; Depth, anterior chamber; Axial length

Numerical modeling of essential work of fracture on ductile polymeric films

Essential work of fracture method has been successfully used to characterize the fracture behavior of ductile polymeric films. The observed essential and non-essential fracture process zones are related to the toughness of the films. Three-dimensional finite element method (FEM) modeling has been carried out in this study to elucidate the film fracture process based on the essential work of fracture concept. Experimental observation on a model linear low-density polyethylene (LLDPE) blown film was used to validate the FEM model. The numerical model facilitates an in-depth understanding of the development of stress and strain fields and the fracture process zones at different loading steps. The FEM findings show that film thickness and ligament length have significant influence on the development of stress and strain fields at and around the ligament area. Furthermore, the numerical analysis reveals how various material properties, such as yield stress and strain hardening slope, can influence the development of fracture process zones. Usefulness of FEM modeling for developing tough polymeric films is discussed.