Region Of Ligament Research Articles

Dynamic Deformation Behavior of the Porcine Anterior Cruciate Ligament Enthesis Under Anterior Tibial Loading.

This study determined the insertion angle at the porcine anterior cruciate ligament (ACL) enthesis under joint loading to provide information on the structure and mechanical function of the enthesis. Ten intact porcine knee joints were harvested, and an anterior tibial load was applied using a robotic testing system. After dissecting a portion of the ACL enthesis along ligament fibers, the remaining enthesis was imaged using a digital microscope while reproducing the three-dimensional intact knee motion. Fiber orientation angles (FOAs) in the enthesis region (0-300µm from the ligament-bone boundary) and the ligament region (500-2000µm from the ligament-bone boundary) were analyzed in the femoral and tibial entheses of the anteromedial bundle (AMB) of the ACL under loading. On the femoral side, the FOA in the enthesis region was significantly higher than that in the ligament region by approximately 10 degrees under loading (n = 5, p < 0.05 in paired t-test). In contrast, the FOAs in the enthesis and ligament regions on the tibial side were nearly equal under loading, with no significant difference (n = 5, p > 0.15 in paired t-test). Histological examination indicated that uncalcified fibrocartilage (UF) was abundant in the enthesis region of the AMB femoral enthesis while the UF was not observed in the enthesis region of the AMB tibial enthesis. Thus, the current data suggest that the regional dependence and independence in FOA are caused by the presence or absence of UF and contributes to a moderate and subtle load-transduction in the ACL enthesis.

Biomechanical effects of anew crimpable gate spring combined with conventional rectangular archwires for torque adjustment of individual anterior teeth : Acomparative finite element study.

Precise root torque adjustment of anterior teeth is indispensable for optimizing dental esthetics and occlusal stability in orthodontics. The efficiency of traditional rectangular archwire manipulation within bracket slots seems to be limited. The crimpable gate spring, anovel device, has emerged as apromising alternative. Yet, there is apaucity of guidelines for its optimal clinical application. This study used finite element analysis (FEA) to investigate the biomechanical impact of the gate spring on torque adjustment of individual anterior teeth and to elucidate the most effective application strategy. AFEA model was constructed by amaxillary central incisor affixed with an edgewise bracket featuring a0.022 × 0.028 inch (in) slot. Arange of stainless steel rectangular archwires, in conjunction with agate spring, were modeled and simulated within the bracket slots. Acontrol group utilized aconventional rectangular wire devoid of agate spring. Palatal root moments were standardized to 9, 18, and 36 Nmm for both experimental and control groups. The gate spring significantly amplified palatal root movement, notably with the 0.019 × 0.025 in archwire. However, this was accompanied by an increase in stress on the tooth and periodontal ligament, particularly in the cervical regions. The synergistic use of a0.019 × 0.025 in rectangular archwire with agate spring in a0.022 × 0.028 in bracket slot was identified as most efficacious for torque control of individual anterior teeth. The gate spring is aviable auxiliary device for enhancing torque adjustment on individual teeth. However, caution is advised as excessive initial stress may concentrate in the cervical and apical regions of the periodontal ligament and tooth.

Regulation of TGF-β1-induced fibroblast differentiation of human periodontal ligament stem cells through the mutually antagonistic action of ectonucleotide pyrophosphatase/phosphodiesterase 1 and 2.

Human periodontal ligament stem cells (hPDLSCs) differentiate into periodontal ligament (PDL) fibroblasts, osteoblasts, and cementoblasts. To identify inducers of PDL fibroblastic differentiation, monoclonal antibody series were developed a series of against membrane/extracellular matrix (ECM) molecules through decoy immunization. The anti-PDL13 antibody targets ectonucleotide pyrophosphatase/phosphodiesterase 1 (ENPP1), renowned for regulating skeletal and soft tissue mineralization. ENPP1 accumulates in the periodontal ligament region of tooth roots, and specifically localizes to the cell boundaries and elongated processes of the fibroblastic cells. As ENPP1 expression increases during fibroblastic differentiation, mineralization induced by tissue-nonspecific alkaline phosphatase (TNAP), a pyrophosphate-degrading enzyme, is completely inhibited. This is consistent with ENPP1 and TNAP acting in opposition, and TGF-β1-induced ENPP1 expression creates an essential environment for PDL fibroblast differentiation. Representative fibroblastic differentiation markers decrease with endogenous ENPP1 inhibition by siRNA and antibody blocking. ENPP2 generates lipid signaling molecules. In contrast to ENPP1, ENPP2 disappears in TGF-β1-induced PDL fibroblasts. Ectopic expression of ENPP2 hinders TGF-β1-induced PDL fibroblastic differentiation. Suppression of ENPP1 and ENPP2 leads to severe defects in undifferentiated and differentiated cells, demonstrating that these two factors play opposing roles in soft and hard tissue differentiation but can complement each other for cell survival. In conclusion, increased ENPP1 is crucial for TGF-β1-induced PDL differentiation, while ENPP2 and TNAP can inhibit ENPP1. ENPP1 and ENPP2 exhibit complementary functions in the cell survival.

Enzymatic activity of fibroblast activation protein-α is essential for TGF-β1-induced fibroblastic differentiation of human periodontal ligament cells

Human periodontal ligament cells (hPDLCs) contain multipotent postnatal stem cells that can differentiate into PDL fibroblasts, osteoblasts, and cementoblasts. Interaction between the extracellular environment and stem cells is an important factor for differentiation into other progenitor cells. To identify cell surface molecules that induce PDL fibroblastic differentiation, we developed a series of monoclonal antibodies against membrane/ECM molecules. One of these antibodies, an anti-PDL25 antibody, recognizes approximately a 100 kDa protein, and this antigenic molecule accumulates in the periodontal ligament region of tooth roots. By mass spectrometric analysis, we found that the antigenic molecule recognized by the anti-PDL25 antibody is fibroblast activation protein α (FAPα). The expression level of FAPα/PDL25 increased in TGF-β1-induced PDL fibroblasts, and this protein was localized in the cell boundaries and elongated processes of the fibroblastic cells. Ectopic expression of FAPα induced fibroblastic differentiation. In contrast, expression of representative markers for PDL differentiation was decreased by knock down and antibody blocking of FAPα/PDL25. Inhibition of dipeptidyl peptidase activity by a potent FAPα inhibitor dramatically inhibited PDL fibroblastic marker expression but did not affect in cell proliferation and migration.

Position and frequency of lateral canals in carnassial teeth of dogs

Carnassial teeth, as one of the most important teeth in dogs, are commonly affected by different types of injuries and pathological disorders, which require endodontic treatment. Lateral canals, which leave the main root canal, and apical deltas are present in the root canal system of dogs. These canals represent small branches that leave the main root canal at a sharp angle and terminate in a region of the periodontal ligament on the external root surface. In this study, 200 teeth were included, of which 100 were superior fourth premolars and 100 were inferior first molars. Lateral canals were present in a total of 30 roots of superior fourth premolar teeth, whereas in inferior first molars, these canals were found in 3% of roots. In superior fourth premolars, lateral canals were mostly present in the apical third, 86%, while 14% were present in the middle third of the root. In inferior first molars, lateral canals were found in 3% of the roots, 2% in the apical third and 1% in the middle third of the roots. The knowledge of the complex root canal morphology is essential for any endodontic treatment. Due to the presence and frequency of lateral canals, it is imperative to perform more thorough cleaning and instrumentation while performing endodontic treatment on superior fourth premolars compared to inferior first molars.

Relationship Between Hip Capsular Thickness and Instability After Previous Hip Arthroscopic Surgery: A Matched-Cohort Analysis.

Thinner anterior hip capsules are associated with hip laxity, but there is little known about the impact of capsular thickness on the development of instability after primary hip arthroscopic surgery. To investigate the relationship between hip capsular thickness as measured on preoperative magnetic resonance imaging (MRI) and the development of hip instability after hip arthroscopic surgery for femoroacetabular impingement. Case-control study; Level of evidence, 3. We reviewed revision hip arthroscopic procedures performed between January 1, 2019, and May 1, 2021, at a single institution. Inclusion criteria were preoperative MRI/magnetic resonance arthrography, completion of the study traction protocol, and asymmetric distraction between the hips of ≥3 mm on examination under anesthesia. A comparison group of patients treated for femoroacetabular impingement with primary hip arthroscopic surgery who did not develop capsular instability were matched 1:1 to the patients with instability. Superolateral hip capsular thickness was measured on MRI before index surgery. Analysis was conducted using independent-samples t tests and multivariable linear regression. A total of 44 patients were included, with 22 patients each in the instability and no-instability groups. The mean capsular thickness was lower in the patients with hip instability than in those without (1.9 ± 0.6 vs 3.4 ± 1.1 mm, respectively; P < .001). Decreased capsular thickness was significantly associated with hips with instability versus no-instability (β = -1.468 [95% CI, -2.049 to -0.887]; P < .001). Thinner preoperative hip capsules in the region of the iliofemoral ligament were seen in patients who subsequently underwent revision arthroscopic surgery for hip instability compared to patients who underwent primary hip arthroscopic surgery without subsequent revision. Patients at a higher risk for the development of postoperative hip instability had a superolateral hip capsular thickness of <2 mm.

Fracture behavior of double edge notch AlSi10Mg alloy fabricated by laser powder bed fusion

In the present study, the fracture behavior of additively manufactured (AM) metal parts has been investigated. To this aim, double edge notch tension (DENT) specimens have been printed using AlSi10Mg alloy based on the laser powder bed fusion (PBF) technique. Particularly, DENT specimens have been fabricated with three different ligament lengths and three different printing directions for each ligament length. In this study, we used the concept of essential work of fracture to describe the fracture behavior AMed parts. According to a series of tests under static loading conditions, influences of the ligament length and printing direction on the structural integrity of the DENT specimens have been determined. According to the experimental practices, levels of ductility and size of plastic zone in the ligament region have been documented. Here, we utilized digital image correlation technique to measure strain fields on the surface of the examined samples. Moreover, numerical simulations have been conducted to simulate the stress distribution from DENT specimens. In addition, visual inspection of the fracture surfaces has been conducted using a free-angle observation system. The outcome of this study can be used for future designs of PBF printed parts with a better structural performance.

Imaging Characteristics of Nonrheumatoid Arthritis Patients With Retro-odontoid Pseudotumor: A Multicenter Case-control Study.

Multicenter case-control study. To identify imaging characteristics of the cervical spine in patients with retro-odontoid pseudotumor (ROP) without rheumatoid arthritis (RA) and determine the pathogenesis of ROP. ROP results from proliferative changes in the soft tissue of the atlantoaxial junction surrounding the region of the transverse ligament, and is commonly seen in RA patients. However, the pathogenesis of ROP caused by mechanical instability of the upper cervical spine in patients without RA is yet to be explained. We collected imaging data [preoperative radiographs, magnetic resonance imaging (MRI), and computed tomography (CT)] of patients who underwent surgery between April 2011 and March 2022 at the three university hospitals for ROP (cases) and cervical spondylotic myelopathy (as age, sex, and institution matched controls). The two groups were compared for different parameters on cervical dynamic radiographs, MRI, and CT. The ROP group consisted of 42 patients, and the control group comprised 168 patients. C2-C7 range of motion was significantly smaller in the ROP group (25.8 ± 2.6°) compared with the control group (33.0 ± 1.0°). C2-C7 sagittal vertical axis was significantly larger in the ROP group than the control group (39.3 ± 3.6 vs. 32.2 ± 1.3mm). MRI and CT assessment showed progressive degeneration at all intervertebral levels in the ROP group. A significant positive correlation was observed between the thickness of the soft tissue posterior to the dental process and the atlantodental interval in the flexion position ( r = 0.501). The development of ROP was associated with degeneration of facet joints and intervertebral disks in the middle and lower cervical spine. Our findings suggest that decreased mobility of the middle and lower cervical spine may cause instability in the upper cervical spine, leading to the formation of ROP.

Enthesis maturation in engineered ligaments is differentially driven by loads that mimic slow growth elongation and rapid cyclic muscle movement

Entheses are complex attachments that translate load between elastic-ligaments and stiff-bone via organizational and compositional gradients. Neither natural healing, repair, nor engineered replacements restore these gradients, contributing to high re-tear rates. Previously, we developed a culture system which guides ligament fibroblasts in high-density collagen gels to develop early postnatal-like entheses, however further maturation is needed. Mechanical cues, including slow growth elongation and cyclic muscle activity, are critical to enthesis development in vivo but these cues have not been widely explored in engineered entheses and their individual contribution to maturation is largely unknown. Our objective here was to investigate how slow stretch, mimicking ACL growth rates, and intermittent cyclic loading, mimicking muscle activity, individually drive enthesis maturation in our system so to shed light on the cues governing enthesis development, while further developing our tissue engineered replacements. Interestingly, we found these loads differentially drive organizational maturation, with slow stretch driving improvements in the interface/enthesis region, and cyclic load improving the ligament region. However, despite differentially affecting organization, both loads produced improvements to interface mechanics and zonal composition. This study provides insight into how mechanical cues differentially affect enthesis development, while producing some of the most organized engineered enthesis to date. Statement of significanceEntheses attach ligaments to bone and are critical to load transfer; however, entheses do not regenerate with repair or replacement, contributing to high re-tear rates. Mechanical cues are critical to enthesis development in vivo but their individual contribution to maturation is largely unknown and they have not been widely explored in engineered replacements. Here, using a novel culture system, we provide new insight into how slow stretch, mimicking ACL growth rates, and intermittent cyclic loading, mimicking muscle activity, differentially affect enthesis maturation in engineered ligament-to-bone tissues, ultimately producing some of the most organized entheses to date. This system is a promising platform to explore cues regulating enthesis formation so to produce functional engineered replacements and better drive regeneration following repair.

Effects of different designs of orthodontic clear aligners on the maxillary central incisors in the tooth extraction cases: a biomechanical study

BackgroundControlling the 3D movement of central incisors during tooth extraction cases with clear aligners is important but challenging in invisible orthodontic treatment. This study aimed to explore the biomechanical effects of central incisors in tooth extraction cases with clear aligners under different power ridge design schemes and propose appropriate advice for orthodontic clinic.MethodsA series of Finite Element models was constructed to simulate anterior teeth retraction or no retraction with different power ridge designs. These models all consisted of maxillary dentition with extracted first premolars, alveolar bone, periodontal ligaments and clear aligner. And the biomechanical effects were analysed and compared in each model.ResultsFor the model of anterior teeth retraction without power ridge and for the model of anterior teeth no retraction with a single power ridge, the central incisors exhibited crown lingual inclination and relative extrusion. For the model of anterior teeth no retraction with double power ridges, the central incisors tended to have crown labial inclination and relative intrusion. For the model of anterior tooth retraction with double power ridges, the central incisors exhibited a similar trend to the first kind of model, but as the depth of the power ridge increased, there was a gradual decrease in crown retraction value and an increase in crown extrusion value. The simulated results showed that von-Mises stress concentration was observed in the cervical and apical regions of the periodontal ligaments of the central incisors. The clear aligner connection areas of adjacent teeth and power ridge areas also exhibited von-Mises stress concentration and the addition of power ridge caused the clear aligner to spread out on the labial and lingual sides.ConclusionsThe central incisors are prone to losing torque and extruding in tooth extraction cases. Double power ridges have a certain root torque effect when there are no auxiliary designs, but they still cannot rescue tooth inclination during tooth retraction period. For tooth translation, it may be a better clinical procedure to change the one-step aligner design to two-step process: tilting retraction and root control.

High-frequency near-infrared semiconductor laser irradiation suppressed experimental tooth movement-induced inflammatory pain markers in the periodontal ligament tissues of rats

High-frequency near-infrared (NIR) semiconductor laser-irradiation has an unclear effect on nociception in the compressed lateral periodontal ligament region, a peripheral nerve region. This study aimed to investigate the effects of NIR semiconductor laser irradiation, with a power of 120J, on inflammatory pain markers and neuropeptides induced in the compressed lateral periodontal ligament area during ETM. A NIR semiconductor laser [910nm wavelength, 45 W maximum output power, 300 mW average output power, 30kHz frequency, and 200ns pulse width (Lumix 2; Fisioline, Verduno, Italy)] was used. A nickel-titanium closed coil that generated a 50-g force was applied to the maxillary left-side first molars and incisors in 7-week-old Sprague-Dawley (280-300g) rats to induce experimental tooth movement (ETM) for 24h. Ten rats were divided into two groups (ETM + laser, n = 5; ETM, n = 5). The right side of the ETM group (i.e., the side without induced ETM) was evaluated as the untreated group. We performed immunofluorescent histochemistry analysis to quantify the interleukin (IL)-1β, cyclooxygenase-2 (COX2), prostaglandin E2 (PGE2), and neuropeptide [calcitonin gene-related peptide (CGRP)] expression in the compressed region of the periodontal tissue. Post-hoc Tukey-Kramer tests were used to compare the groups. Compared with the ETM group, the ETM + laser group showed significant suppression in IL-1β (176.2 ± 12.3 vs. 310.8 ± 29.5; P < 0.01), PGE2 (104.4 ± 14.34 vs. 329.6 ± 36.52; P < 0.01), and CGRP (36.8 ± 4.88 vs. 78.0 ± 7.13; P < 0.01) expression. High-frequency NIR semiconductor laser irradiation exerts significant effects on ETM-induced inflammation. High-frequency NIR semiconductor laser irradiation can reduce periodontal inflammation during orthodontic tooth movement.

Composite Graded Melt Electrowritten Scaffolds for Regeneration of the Periodontal Ligament-to-Bone Interface.

Periodontitis is a ubiquitous chronic inflammatory, bacteria-triggered oral disease affecting the adult population. If left untreated, periodontitis can lead to severe tissue destruction, eventually resulting in tooth loss. Despite previous efforts in clinically managing the disease, therapeutic strategies are still lacking. Herein, melt electrowriting (MEW) is utilized to develop a compositionally and structurally tailored graded scaffold for regeneration of the periodontal ligament-to-bone interface. The composite scaffolds, consisting of fibers of polycaprolactone (PCL) and fibers of PCL-containing magnesium phosphate (MgP) were fabricated using MEW. To maximize the bond between bone (MgP) and ligament (PCL) regions, we evaluated two different fiber architectures in the interface area. These were a crosshatch pattern at a 0/90° angle and a random pattern. MgP fibrous scaffolds were able to promote in vitro bone formation even in culture media devoid of osteogenic supplements. Mechanical properties after MgP incorporation resulted in an increase of the elastic modulus and yield stress of the scaffolds, and fiber orientation in the interfacial zone affected the interfacial toughness. Composite graded MEW scaffolds enhanced bone fill when they were implanted in an in vivo periodontal fenestration defect model in rats. The presence of an interfacial zone allows coordinated regeneration of multitissues, as indicated by higher expression of bone, ligament, and cementoblastic markers compared to empty defects. Collectively, MEW-fabricated scaffolds having compositionally and structurally tailored zones exhibit a good mimicry of the periodontal complex, with excellent regenerative capacity and great potential as a defect-specific treatment strategy.

Development of a 3D-immunofluorescence analysis for sensory nerve endings in human ligaments

BackgroundThe analysis of ligamentous mechanoreceptors is difficult due to a high amount of unclassifiable mechanoreceptors, which result from incomplete visualization through limited microscopic techniques. New methodThe method was developed using dorsal intercarpal ligaments and dorsal regions of the scapholunate interosseous ligament from human cadaver wrists. Consecutive 70 µm thick cryosections were stained with immunofluorescence markers for protein S100B, neurotrophin receptor p75 (p75), protein gene product 9.5 (PGP 9.5) and 4′,6-diamidino-2-phenylindole (DAPI). 3D images of sensory nerve endings were obtained using a confocal laser scanning microscope. Experimental point spread functions (PSF) were used to deconvolve images. Sensory nerve endings were localised in each section plane and classified according to Freeman and Wyke. Finally, confocal data was visualized as 3D-images. ResultsThe method produced excellent image quality, revealing detailed three-dimensional structures. The created 3D-model of sensory nerve endings could be analyzed in all three dimensions, augmenting visualization of the form and immunoreactive pattern of sensory nerve endings. Deconvolution with experimentally measured PSFs aided in enhancing image quality. Comparison with existing methodsUsing a triple immunofluorescent staining method allows to visualize the structure of sensory nerve endings more precisely than techniques with serial analysis of different monostaining of neural markers. Imaging in three dimensions enhances morphologic details, which are limited in 2D-microscopy. Conclusion3D-triple immunofluorescence produces high quality visualization of mechanoreceptors, thereby improving their analysis. As an elaborate technique, it is ideal for defined research questions concerning the microstructure of sensory nerve endings.

Dunbar Syndrome Treated by Laparoscopic Surgery

Median arcuate ligament syndrome (MALS) or Dunbar syndrome is a rare condition resulting from compression of the celiac trunk by the median ligament at the level of the diaphragmatic crus. Abdominal tomography contributes to the diagnosis by demonstrating the level of obstruction and the presence of collateral arterial circulation in the gastroduodenal region, typical of the disease in chronic cases. The therapeutic options, although few, find in the laparoscopic surgical treatment the best option for releasing the muscle fibers in the arcuate ligament region. We report a rare case of a 38-year-old woman diagnosed with MALS successfully treated laparoscopically.

Essential work of fracture studies of 3D Printed PEEK (Poly-ether-ether-ketone) polymer

The concept of essential work of fracture is implemented for characterizing the raster-orientation-dependent fracture behavior of 3D printed PEEK polymer for the first time. The fracture tests are carried out on various 3D printed double-edge-notched-tension specimens of constant thickness but different raster orientations. It is observed that the fracture initiation energy has a strong dependence on the raster orientation and attains the highest value for 0° raster orientation (printing direction perpendicular to the crack plane) and the lowest value for 90° raster orientation (printing direction parallel to crack plane). The fracture tests have indicated that the ductility levels of the samples and size of plastic zone developed within the ligament region are also controlled by the raster orientation. In addition to fracture tests, the fractured surfaces of the test samples are also examined to identify the dominant failure mechanisms. The detailed analysis carried out in this study provide guidelines in making fracture resistant 3D printed PEEK components.

Resection of Giant Cemento-Ossifying Fibroma of Jaws by Intraoral Approach—A Case Report and Review

Introduction: The World Health Organization in 1971 first classified fibro-osseous lesions (FOLs) as cementum forming tumors of jaws as ossifying fibroma (OF), cement-osseous dysplasia, and fibrous dysplasia. Various theories have been put forward regarding the origin of cemento-ossifying fibroma (COF) but current interests are oriented toward traumatic and developmental etiologies. The COFs are a slow-growing osteoexpansile tumor which grows to a considerable size. The tumor usually arises from tooth bearing and periodontal ligament region basically of odontogenic origin. Background: An inordinate, bony hard swelling, present united in both the jaws showing radiopaque-radiolucent mass, corticated margins, with expansion of buccal as well as lingual cortex gives a delusional image for the provisional diagnosis for surgeon, particularly to decide the surgical approach. These traits showing similarity with FOLs, more particularly cemento-OF, owing to its odontogenic or periodontal origin. Case Report: In this case, a 42-year-old female presented with abovementioned features was first taken for biopsy and then planned for simultaneous surgical resection of pathology for both jaws, from an intraoral approach giving a scar-free result. Preclusion of immediate complications was dealt with reconstruction of mandible with 2.5-mm titanium reconstruction plate. Conclusion: The diagnosis of cement-OF is based on clinical-radiographic-histopathologic evaluation. If remain untreated, these tumor can grow up to an average size of 80 mm, therefore, demanding an early surgical intervention. In our case, intraoral approach leads to almost no residual fibrosed tissue. The patient is further being planned for rehabilitation with either free fibula graft or 3-dimensional mandibular prosthesis.

A generalized solution to the combo-crack problem—II. Remote load

In Part I, we studied the combo-crack problem, which contains an interior penny-shaped crack (PSC) and a coplanar and concentric externally circular crack (ECC), under pressure load applied to the surface of the interior PSC. In fact, a more common type of loading experienced by cracked media might be remote tension normal to the crack plane. For a combo crack under remote tension, a reliable solution remains deficient. In this paper, we extend our discussion to the case of remote tension in the theoretical framework developed in Part I. We for the first time formulate the concerned mixed boundary value problem into a single inhomogeneous Fredholm integral equation, which is then solved numerically with a Gauss-Lobatto quadrature-based algorithm. The normal stress in the ligament (bonded) region on the plane of the crack, the stress intensity factors at the tips of PSC and ECC, and the critical force load for trigging crack propagation are determined, showing an excellent agreement with the finite element results. Our work provides a high-precision numerical solution to the combo-crack problem for the most basic loading case. The obtained results should be of general value to the resolution of a bunch of fracture and adhesion problems in combo-crack configuration in engineering and deserve to be absorbed into the updated handbook for basic crack problems.

Morphometrics of nuchal ligament in greyhound in different neck and body positions

This study was conducted to describe the morphometrics of nuchal ligament and investigate the effects of different neck and body positions on the nuchal ligament in greyhounds. Nine adult greyhounds cadavers without any locomotion abnormalities were dissected through the neck musculature on the left side to expose the nuchal ligament. Three pins were placed to mark regions of interest on the nuchal ligament: at one cm cranial to the site of origin (the most dorsal point of the spinous process of the first thoracic vertebra), at the midpoint of the nuchal ligament and one cm caudal to the nuchal ligament site of insertion (close to the caudal aspect of the spinous process of the axis). Each cadaver was positioned on a masonite board and placed on a table on the floor in their lateral recumbency and seven different standardized body positions; P1-P7 were mimicked using goniometers and metal wires. Photographs were taken by positioning and fixing the camera above the nuchal ligament region. The length and widths (W1, W2 and W3) of nuchal ligament were measured using Image Pro software (Image-Pro Express version 5.0) on standardized photographs of each of seven different body and neck positions. The length of nuchal ligament in relation to the neutral position (P1) was less (- 7%, p>0·05) in P6 (neck elevated) and increased in all other positions (+1%, p>0·05 for P2, +19%, p<0·05 for P3, +37%, p<0·05 for P4, +1%, p>0·05 for P5, +40%, p<0·05 for P7). Nuchal ligament width at the middle (W2) decreased significantly with P4 (- 26%, p<0·05), and P7 (- 32%, p<0·05). Also, nuchal ligament width at the site of origin (W3) decreased significantly with P4 (- 24%, p < 0·05) and P7 (-35%, p<0·05). These findings reflect the need for clinical and biomechanical studies to describe in-depth the gross anatomy of the nuchal ligament in greyhounds. They suggest that different neck and body positions change the shape, and hence, the function of the nuchal ligament during movement.

A DOUBLE-EDGED SWORD: CPR COMPLICATED BY FATAL HEPATIC LACERATION

TOPIC: Critical Care TYPE: Medical Student/Resident Case Reports INTRODUCTION: While cardiopulmonary resuscitation (CPR) is a life-sustaining measure, it is accompanied by a litany of risks. Complications of CPR are commonly observed relative to the thoracic cavity, with frequently reported injuries to the sternum, ribs, heart, and lungs (1). Intra-abdominal injury during CPR is rare (1). Case reports of liver laceration during CPR have been sporadically reported in academic discourse. Retrospective studies suggest an estimated incidence of 0.6-3% (1). CASE PRESENTATION: A 60-year-old female with a past medical history of type 2 diabetes and hypertension presented with right hip pain secondary to mechanical fall. She was subsequently admitted for right comminuted hip fracture and treated with open reduction and internal fixation. The surgery was complicated by acute blood loss. On postoperative day 11, the patient went into cardiac arrest. Chest compressions were initiated; ROSC was achieved in 18 minutes. Subsequent laboratory investigations were notable for a downward trend in hemoglobin from 8.6 to 5.7. Three units of packed red blood cells were transfused without improvement. CT scan of the abdomen showed a large intraperitoneal hematoma in the region of gastro-hepatic ligament; these findings were new compared to prior studies (see figure 1). An exploratory laparotomy was completed emergently, which showed a laceration of left lobe of liver with capsular rupture and persistent bleeding from the raw surface of the liver with a 1.5 L hematoma. On the day of operation, a meeting was held between the family, palliative care and ICU team. After discussion with the family, the patient was made DNR/DNI and terminally extubated. DISCUSSION: Hepatic laceration should be routinely considered in patients who have undergone CPR. The incidence of hepatic laceration in CPR is likely underreported, as hemorrhagic shock may be masked by vasopressor support after cardiac arrest (2). Liver injury in CPR is most commonly observed in the left lobe of the liver due to the proximity of the lobe to the sternum. Once more, the liver is at risk of being pierced by the "sword-shaped" sternum during chest compressions (1). CPR technique may be considered when assessing the risk of intra-abdominal injury, however research remains mixed on if training may be related to risk of injury (1). Careful monitoring of hemodynamic status, serial clinical examination, and hematologic laboratory parameters such as hemoglobin, is essential to evaluating for CPR-associated injury (3). CONCLUSIONS: While CPR has obvious utility in cardiac arrest, it is a traumatic intervention with risks that should be carefully considered. Further research is required on how CPR technique may be improved to reduce the risk of intra-abdominal injury. REFERENCE #1: Beydilli, H., Balci, Y., Erbas, M., Acar, E., Isik, S., & Savran, B. (2016). Liver laceration related to cardiopulmonary resuscitation. Turkish journal of emergency medicine, 16(2), 77–79. REFERENCE #2: Beloncle, F., Meziani, F., Lerolle, N., Radermacher, P., & Asfar, P. (2013). Does vasopressor therapy have an indication in hemorrhagic shock?. Annals of intensive care, 3(1), 13. REFERENCE #3: Biswas, S., Alpert, A., Lyon, M., & Kaufmann, C. (2017). Cardiopulmonary Resuscitation Complicated by Traumatic Hepatic Laceration: A Case Report and Review of Literature. Journal Of Medical Cases, 8(3), 93-97. DISCLOSURES: No relevant relationships by Guy Aristide, source=Web Response No relevant relationships by Haris Asif, source=Web Response No relevant relationships by Johnathan Kirupakaran, source=Web Response No relevant relationships by Paula Bianca Rodriguez, source=Web Response No relevant relationships by Dhiviyan Valentine, source=Web Response

Clay-Based Polymer Nanocomposites: Essential Work of Fracture.

This work details the general structure of the clays used as a reinforcement phase in polymer nanocomposites. Clays are formed by the molecular arrangement of atomic planes described through diagrams to improve their visualization. The molecular knowledge of clays can facilitate the selection of the polymer matrix and achieve a suitable process to obtain clay-based polymer nanocomposite systems. This work highlights the development of polymer nanocomposites using the melt intercalation method. The essential work of fracture (EWF) technique has been used to characterize the fracture behavior of materials that show ductility and where complete yielding of the ligament region occurs before the crack propagation. In this sense, the EWF technique characterizes the post-yielding fracture mechanics, determining two parameters: the specific essential work of fracture (we), related to the surface where the actual fracture process occurs, and the specific non-essential work of fracture (wp), related to the plastic work carried out in the outer zone of the fracture zone. The EWF technique has been used successfully in nano-reinforced polymers to study the influence of different variables on fracture behavior. In this work, the fundamentals of the EWF technique are described, and some examples of its application are compiled, presenting a summary of the most relevant contributions in recent years.