Ligament Specimens Research Articles

Analysis of biomechanical properties of patellar ligament graft and quadruple hamstring tendon graft.

Two types of transplant are commonly used in the surgical management of anterior cruciate ligament lesions: the central part of the patellar ligament and quadruple tendons of the gracilis muscle and semitendinosus muscle. The aim of this study was to determine the biomechanical characteristics of patellar ligament transplants and transplants of the quadruple tendons of the hamstring muscles under tensile force in the laboratory, and to compare the results in each group of samples. The study comprised 160 specimens: 40 specimens of gracilis muscle tendons, 40 of semitendinosus muscle tendons, 40 of quadruple tendons and 40 of the patellar ligament, approximately equally distributed according to sex, age (50-70 years) and the side of the body from which the specimen had been taken. The working curve analysis of the specimens under tensile load of a maximum force of 30N showed the least elongation (0.31%) in the quadruple tendon, followed by the gracilis muscle tendon (1.48%) and patellar ligament tendon (3.91%). The quadruple tendon specimen showed greater strength and higher elasticity compared with the patellar ligament specimen, which proved the starting hypothesis.

Biomechanical Evaluation of the Stabilizing Function of Three Atlantoaxial Implants Under Shear Loading: A Canine Cadaveric Study.

To compare the biomechanical properties of a ventral transarticular lag screw fixation technique, a new dorsal atlantoaxial instability (AAI) clamp, and a new ventral AAI hook plate under sagittal shear loading after transection of the ligaments of the atlantoaxial joint. Cadaveric biomechanical study. Canine cadavers (n = 10). The occipitoatlantoaxial region of Beagles euthanatized for reasons unrelated to the study was prepared leaving only ligamentous structures and the joint capsules between the first 2 cervical vertebrae (C1 and C2). The atlanto-occipital joints were stabilized with 2 transarticular diverging positive threaded K-wires. The occipital bone and the caudal end of C2 were embedded in polymethylmethacrylate and loaded in shear to a force of 50 Newtons. The range of motion (ROM) and neutral zone (NZ) of the atlantoaxial joint were determined after 3 loading cycles with atlantoaxial ligaments intact, after ligament transection, and after fixation with each implant. The testing order of implants was randomly assigned. The implants tested last were subjected to failure testing. All stabilization procedures decreased the ROM and NZ of the atlantoaxial joint compared to transected ligament specimens. Only stabilization with transarticular lag screws and ventral plates produced a significant reduction of ROM compare to intact specimens. Fixation with transarticular lag screws and a ventral hook plate was biomechanically similar and provided more rigidity compared to dorsal clamp fixation. Further load cycling to failure tests and clinical studies are required before making clinical recommendations.

In Vivo Measurement of Mesokinesis in Gekko gecko: The Role of Cranial Kinesis during Gape Display, Feeding and Biting.

Cranial kinesis refers to movements of skeletal sub-units relative to one another at mobile sutures within the skull. The presence and functional significance of cranial kinesis has been investigated in various vertebrates, with much of our understanding coming from comparative studies and manipulation of ligamentous specimens. Drawing on these studies, cranial kinesis in lizards has been modeled as a four-bar linkage system involving streptostyly (rotation of the quadrate), hypokinesis (dorsoventral flexion and extension of the palato-maxillary sub-unit), mesokinesis (dorsoventral flexion and extension of the snout at the fronto-parietal suture) and metakinesis (sliding movements between parietal and supraocciptal bones). In vivo studies, although limited, suggest that cranial kinesis serves an important role during routine behaviors such as feeding. Here, we use X-ray Reconstruction Of Moving Morphology to further quantify mesokinesis in vivo in Gekko gecko during three routine behaviors: gape display, biting and post-ingestion feeding. During gape display, the snout rotates dorsally above rest position, with mesokinesis accounting for a 10% increase in maximum gape over that achieved solely by the depression of the lower jaw. During defensive biting, the snout rotates ventrally below rest position to participate in gape closure. Finally, ventroflexion of the snout also occurs during post-ingestion feeding, accounting for 42% of gape closure during intra-oral transport, 86% during puncture-crushing, and 61% during pharyngeal packing. Mesokinesis thus appears to facilitate prey puncturing by allowing the snout to rotate ventrally so that the upper teeth pierce the prey item, thus limiting the need for large movements of the lower jaw. This is suggested to maintain a firm grip on the prey and reduce the possibility of prey escape. More generally, this study demonstrates that mesokinesis is a key component of defensive biting and gape display behaviors, as well as post-ingestion feeding, all of which are linked to organismal fitness.

Importance of IL-6, MMP-1, IGF-1, and BAX Levels in Lumbar Herniated Disks and Posterior Longitudinal Ligament in Patients with Sciatic Pain

The aim of this study was to evaluate prognostic importance of interleukin-6 (IL-6), matrix metalloproteinase (MMP)-1, insulin-like growth factor (IGF)-1, and Bcl-2-associated X protein (BAX) levels in biopsy specimens taken from the intervertebral disk specimens and the posterior longitudinal ligaments of patients with sciatic pain. The specimens of the intervertebral disk and the posterior longitudinal ligament were obtained from 52 patients undergoing herniectomy and diskectomy at the Neurosurgery Department of the Abant Izzet Baysal University Izzet Baysal Training and Research Hospital between April 2012 and February 2014. The immunohistochemical expressions of IL-6, MMP-1, IGF-1, and BAX were evaluated in three categories: mild, moderate, and intense. The IL-6 expression in the intervertebral disk specimens was intense in the sequestration group when compared with that of the "protrusion" and "extrusion" groups. The intervertebral disk specimens in "extrusion" and "sequestration" groups were stained intensely for MMP-1. The IGF-1 expression was stained intensely in the intervertebral disk tissue of the extrude group patients. For the "extrusion" and "sequestration" groups, the intervertebral disk specimens were stained intensely for BAX compared with the protrude group. The IL-6 expression in the posterior longitudinal ligament specimens was more intense in the "sequestration" and "extrusion" groups when compared with that of the protrude group. The MMP-1 expressions were milder in the sequestration group when compared with that of the "extrusion" and "protrusion" groups. Our findings suggest that the cytokines, enzymes, growth factors, and proapoptotic proteins, such as IL-6, MMP-1, IGF-1, and BAX, may be critical factors in the pathophysiology of the degeneration of the intervertebral disks in patients with symptomatic degenerative disk disease.

An update on the constitutive relation of ligament tissues with the effects of collagen types

The musculoskeletal ligament is a kind of multiscale composite material with collagen fibers embedded in a ground matrix. As the major constituent in ligaments to bear external loads, collagens are composed mainly of two collagen contents with different mechanical properties, i.e., types I and III collagen. The constitutive relation of ligaments plays a critical role in the stability and normal function of human joints. However, collagen types have not been distinguished in the previous constitutive relations. In this paper a constitutive relation for ligament tissues was modified based on the previous constitutive relation by considering the effects of collagen types. Both the collagen contents and the mechanical properties of sixteen ligament specimens from four cadaveric human knee joints were measured for determining their material coefficients in the constitutive relation. The mechanical behaviors of ligaments were obtained from both the uniaxial tensile and simple shear tests. A linear regression between joint kinematic results from in vitro and in silico experiments was made to validate the accuracy of this constitutive relation. The high correlation coefficient (R2=0.93) and significance (P<0.0001) of the regression equation revealed that this modified constitutive relation of ligaments was accurate to be used in studying joint biomechanics. Another finite element analysis with collagen contents changing demonstrated that the effect of variations in collagen ratios on both joint kinematics and ligament biomechanics could be simulated by this constitutive relation.

Immunohistochemical analysis of the neural structures of the posterior cruciate ligament in osteoarthritis patients submitted to total knee arthroplasty: an analysis of thirty-four cases

OBJECTIVES:Many authors recommend posterior cruciate ligament-retaining arthroplasty with the intention to maintain the proprioception properties of this ligament. Preservation of the neuroreceptors and nervous fibers may be essential for retaining the proprioception function of the posterior cruciate ligament. The present study was thus developed to evaluate the presence of neural structures in the posterior cruciate ligament resected during posterior stabilized arthroplasty in osteoarthritis patients. In particular, clinical, radiographic and histological parameters were correlated with the presence or absence of neural structures in the posterior cruciate ligament.METHODS:In total, 34 posterior cruciate ligament specimens were stained with hematoxylin-eosin and Gomori trichrome. An immunohistochemical analysis using antibodies against the S100 protein and neurofilaments was also performed. The presence of neural structures was correlated with parameters such as tibiofemoral angulation, histological degeneration of the posterior cruciate ligament, Ahlbäck radiological classification, age, gender and the histologic pattern of the synovial neurovascular bundle around the posterior cruciate ligament.RESULTS:In total, 67.5% of the cases presented neural structures in the posterior cruciate ligament. In 65% of the cases, the neurovascular bundle was degenerated. Nervous structures were more commonly detected in varus knees than in valgus knees (77% versus 50%). Additionally, severe histologic degeneration of the posterior cruciate ligament was related to neurovascular bundle degeneration.CONCLUSIONS:Severe posterior cruciate ligament degeneration was related to neurovascular bundle compromise. Neural structures were more commonly detected in varus knees. Intrinsic neural structures were detected in the majority of the posterior cruciate ligaments of patients submitted to knee arthroplasty for osteoarthritis.

Shape and size of the medial patellofemoral ligament for the best surgical reconstruction: a human cadaveric study.

The aim of this study was to investigate the shape and the attachments of the medial patellofemoral ligament (MPFL) in cadaver specimens to determine an anatomical basis for the best MPFL reconstruction. Twenty fresh-frozen knees were used. Dissection protocol implied performing dissections from within the knee joint. We investigated the shape and the attachments between the MPFL and the quadriceps tendon, the patellar and femur insertions, and all the other relationships with the medial soft tissues of the knee. The distal fibers of MPFL were interdigitated with the deep layer of the medial retinaculum. All isolated ligament had a sail-like shape with the patellar side bigger than the femoral side. The femoral insertion, distinct both from medial epicondyle and adductor tubercle, was located at 9.5 mm (range 4-22) distal and anterior respect to adductor tubercle and proximal and posterior to epicondyle. The medial third of the thickness of patella was involved in the insertion. The proximal third of the patella is always involved in the MPFL attachment; in 45% of the cases, it was extended to the medial third and in one case, an extension at the distal third was found. Additionally in 35% (7 cases), it extended to the quadriceps tendon and it were inconstantly attached at the vastus medialis obliques (VMO) tendon and at the vastus intermedius (VI) tendon in an aponeurotic structure. The MPFL is a distinct structure that goes from patella to femur with a sail-like shape; its patellar insertion, that mostly occur via an aponeurosis tissue with VMO and VI, is at the proximal third of the patella but it may extend in some cases to the medial third patella or to the quadriceps tendon, or very rarely to the distal third of the patella. In the femoral side, the MPFL is inserted in its own site, in most cases distinct both from epicondyle and adductor tubercle, located on average at a 9.5 mm distance distally and anteriorly in respect to the adductor tubercle. Its lower margin was difficult to define. Given the importance of this structure, it must be reconstructed as anatomically as possible in its insertion and in its shape. Many attempts have been made to make functional reconstructions with less than excellent results.

Investigation of Selected Physical Parameters of Cementitious Composite during Sequential Fracture Test

The paper is focusing on the investigation of the effective crack length obtained from bending test on concrete notched beams with the complementary measurements of ultrasound passing time through the tested concrete specimen. The ultrasound passing time measurements are performed on several stages of the fracture process along the specimen ligament for each tested notched beam. Gained results of the time of ultrasound pulse needed to pass through specimens' failure zone, i.e. its dependence on the crack length or opening, provide information which may help to identify the process of crack formation without the visible indications. The fracture tests are conducted for a set of specimens differing in the notch length. Changes of the ultrasound passing times with increasing effective crack length are observed and discussed.

Collagen microstructure in the vocal ligament: Initial results on the potential effects of smoking

This investigation quantitatively characterizes the collagenous microstructure of human vocal ligament specimens excised postmortem from nonsmokers and smokers. Retrospective cohort study. Second harmonic generation (SHG) imaging was performed at three anatomical locations of vocal ligament specimens: anterior, mid-membranous, and posterior regions. Two microstructural parameters were extracted from the SHG images: (1) normalized fiber density, and (2) fiber dispersion coefficient, quantifying the degree of collagen fiber dispersion about a preferred direction. For both the nonsmoker and smoker subjects, the fiber dispersion coefficient was heterogeneous. Differences in the collagenous structure of nonsmokers and smoker subjects were pronounced at the mid-membranous location. However, the directionality of the heterogeneity in the smoker subjects was opposite to that in the nonsmoker subjects. Specifically, the fiber dispersion coefficient in the nonsmoker subjects was lower in the mid-membranous region (indicating more fiber alignment) than at the anterior/posterior regions, but for the smoker subjects the fiber dispersion coefficient was higher at the mid-membranous region. The normalized fiber density was near constant in the nonsmoker subjects, but the smoker subjects had fewer fibers in the mid-membranous region than at the anterior/posterior regions. Spatial microstructural variations may exist in the vocal fold ligament both in nonsmokers and smokers. Smoking appears to influence the degree and direction of microstructure heterogeneity in the vocal fold ligament.

Numerical Simulation of Flat-to-slant Ductile Fracture Transition in Notched Plate

The effort of this study is to develop a damage model for simulating large ductile crack extension accompanied by a flat and a slant surface observed in the hydrostatic full-scale tests up to rupture for API X80 line pipes with an axial through-wall notch. A small and thin specimen with a shallow through-thickness notch having a large ligament (sub-sized Charpy V-notch (Sub-CVN) specimen subjected to 3-point bending) is used for a fundamental verification study. The Sub-CVN specimen provided the similar macroscopic process as well as micro-mechanism for ductile cracking, where a flat-to-slant fracture transition accompanied by a transition from an equi-axed dimple mode to a shear-slip mode fracture is presented. On the basis of the observed mechanism of ductile crack growth, a numerical ductile damage model for predicting the large ductile crack growth resistance is proposed taking into account an effect of the Lode parameter on ductile fracture into the present damage model proposed by authors. The crucial consideration is that the damage parameters to be identified can be correlated to the material properties. In this model, the shear-dominated stress state is assumed to advance the acceleration of damage evolution due to a shear localization mechanism at lower damage level even at the same stress triaxiality condition, so that the critical damage fraction dependent on the Lode parameter is phenomenologically employed in this model. The modified damage model reproduces the same ductile crack profile together with the same micro-mechanisms for forming the chevron-shaped flat surface as those observed in the experiment. The possibility to reproduce the flat-to-slant fracture transition is also demonstrated by the simulation.

Investigation of Fracture and Electrical Resistivity Parameters of Cementitious Composite for their Utilization in Deterioration Models

The paper is focusing on the investigation of the effective crack length obtained from bending test on concrete notched beams with the complementary measurements of electrical resistivity of the tested concrete. The electrical resistivity measurements are performed on several stages of the fracture process along the specimen ligament for each tested notched beam. Gained results of the concrete resistivity during the fracture process, i.e. its dependence on the crack length or opening, provide information which should be taken into account in structural durability analyses. The fracture tests are conducted for a set of specimens differing in the notch length. Changes of the concrete resistivity with increasing effective crack length are observed and discussed.

The anisotropic hyperelastic biomechanical response of the vocal ligament and implications for frequency regulation: A case study

One of the primary mechanisms to vary one's vocal frequency is through vocal fold length changes. As stress and deformation are linked to each other, it is hypothesized that the anisotropy in the biomechanical properties of the vocal fold tissue would affect the phonation characteristics. A biomechanical model of vibrational frequency rise during vocal fold elongation is developed which combines an advanced biomechanical characterization protocol of the vocal fold tissue with continuum beam models. Biomechanical response of the tissue is related to a microstructurally informed, anisotropic, nonlinear hyperelastic constitutive model. A microstructural characteristic (the dispersion of collagen) was represented through a statistical orientation function acquired from a second harmonic generation image of the vocal ligament. Continuum models of vibration were constructed based upon Euler-Bernoulli and Timoshenko beam theories, and applied to the study of the vibration of a vocal ligament specimen. From the natural frequency predictions in dependence of elongation, two competing processes in frequency control emerged, i.e., the applied tension raises the frequency while simultaneously shear deformation lowers the frequency. Shear becomes much more substantial at higher modes of vibration and for highly anisotropic tissues. The analysis was developed as a case study based on a human vocal ligament specimen.

Carpal Tunnel Release Surgery and Venous Hypertension in Early Hemodialysis Patients without Amyloid Deposits

Aim. Carpal tunnel syndrome (CTS) is one of the frequent problems of the patients who underwent hemodialysis (HD). The role of venous hypertension due to arteriovenous fistula (AVF) has not been clarified completely; therefore, we aimed to investigate the role of venous hypertension due to AVF in hemodialysis patients who had CTS. Patients and Methods. We included 12 patients who had been receiving HD treatment for less than 8 years and the newly diagnosed CTS patients with the same arm of AVF. All patients were diagnosed clinically and the results were confirmed by both nerve conduction studies and electromyography. Open carpal tunnel release surgery was performed on all of them. Venous pressure was measured in all patients before and after two weeks of surgery. Results. There were significant differences before and after the surgery with regard to pressures (P > 0.05). After the surgery, all carpal ligament specimens of the patients were not stained with Congo red for the presence of amyloid deposition. Conclusion. Increased venous pressure on the same arm with AVF could be responsible for CTS in hemodialysis patients. Carpal tunnel release surgery is the main treatment of this disease by reducing the compression on the nerve.

A deformation-mechanism-based energy partitioning approach for measurement of plane-stress fracture toughness of low-density polyethylene

A previously proposed energy partitioning approach, based on deformation mechanisms involved in the fracture process, is applied to double-edge-notched tensile (DENT) test to determine plane-stress fracture toughness for a commercial low-density polyethylene (LDPE). Test results show that mechanical behaviour of LDPE is affected by unloading–reloading cycles introduced in the DENT test. Therefore, modification is made for determining the residual elastic energy. The modified energy partitioning approach yields much lower specific energy consumption for fracture than that from the essential work of fracture (EWF) method. Support to this approach comes from the close agreement between the specific energy consumption for necking in the DENT test and the specific deformation energy in the simple tensile test at the same strain level. The paper also analyzes the energy consumption for each mechanism involved in the fracture process and its dependence on the specimen ligament length. The analysis suggests that the non-essential part of energy consumption for crack growth is not purely a function of the square of ligament length. Therefore, the EWF method should not be used to determine fracture toughness for polymers when necking is involved during the crack growth.

Three-Dimensional Elastic-Plastic Constraint Analysis for Side Crack Tension Specimen

A in-plane stress constraint factor Ciand a out-of-plane stress constraint factor Coare introduced to study the three-dimensional stress state and the elastic-plastic constraint effect of the crack tip. The deep crack specimens(a/W=0.5) and the shallow crack specimens(a/W=0.1) with different thicknesses are performed in the present study. By using the finite element analysis, the result shows that the thickness effect of the deep crack specimens is more obvious than that of the shallow crack specimens. For the deep crack specimens, the crack constraint enhances with the specimen thickness increase. When the specimen thickness is equal to the specimen width, the constraint levels in the middle 2/3 thickness of the specimen approach to those from the plane strain analyse. For the shallow crack specimens, the crack constraint is almost fixedness when the specimen thickness changes from three times of a crack length to a specimen ligament length. Namely, increased thickness is helpless to enhance the crack constraint effect. Therefore, a shallow crack specimen may be designed by the lesser thickness than the standard deep crack specimen.

Comparison of stability in the operative treatment of pelvic injuries in a finite element model

The comparison of the stability of four surgical methods for the treatment of vertically and rotationally unstable type C pelvic ring injuries. We produced a type C pelvic ring injury (type Denis II fracture of the sacrum and symphysiolysis) on a finite element model, in the case of standing on both feet. We stabilized the symphysiolysis with a five-hole reconstruction plate; the sacrum fracture was fixed in the first experiment with two, two-hole reconstruction plates on the ventral surface, in the second one we applied dorsally the transsacral, narrow DC plate, in the third one with KFI-H plate, and in the last one with iliosacral screw. Finite element modeling was performed by the use of the ALGOR software. Not only bones and joints, but joints and mechanically important ligaments were modeled as well. We measured the shift between the two surfaces of the fracture gap, compared to the results of measurements accomplished on cadaver models. Larger shift could be elicited after transsacral plating than after direct plating. These results correspond to those of the parallel investigation of the bony ligamentous cadaver pelvis specimens. The shift values after KFI-H plating and iliosacral screw fixation are larger than after direct plating, but smaller than after transsacral plating. The tension created in the implants is less than the allowed values; therefore, the choice of operation should depend on the type of injury. The finite element model may be utilized for the comparison of different methods of osteosynthesis for the treatment of injuries described above. Due to several difficulties in investigations performed on cadaver specimens, this model has undoubted utility.

The effects of modeling simplifications on craniofacial finite element models: The alveoli (tooth sockets) and periodontal ligaments

Several finite element models of a primate cranium were used to investigate the biomechanical effects of the tooth sockets and the material behavior of the periodontal ligament (PDL) on stress and strain patterns associated with feeding. For examining the effect of tooth sockets, the unloaded sockets were modeled as devoid of teeth and PDL, filled with teeth and PDLs, or simply filled with cortical bone. The third premolar on the left side of the cranium was loaded and the PDL was treated as an isotropic, linear elastic material using published values for Young's modulus and Poisson's ratio. The remaining models, along with one of the socket models, were used to determine the effect of the PDL's material behavior on stress and strain distributions under static premolar biting and dynamic tooth loading conditions. Two models (one static and the other dynamic) treated the PDL as cortical bone. The other two models treated it as a ligament with isotropic, linear elastic material properties. Two models treated the PDL as a ligament with hyperelastic properties, and the other two as a ligament with viscoelastic properties. Both behaviors were defined using published stress–strain data obtained from in vitro experiments on porcine ligament specimens. Von Mises stress and strain contour plots indicate that the effects of the sockets and PDL material behavior are local. Results from this study suggest that modeling the sockets and the PDL in finite element analyses of skulls is project dependent and can be ignored if values of stress and strain within the alveolar region are not required.

Relationship of ankle joint proprioceptor injury with chronic ankle instability: a preliminary study

Objective To analyze the effect of ankle joint proprioceptor injury on the functional ankle instability. Methods The study enrolled 18 ( 13 males) with chronic ankle instability treated with ligament reconstruction operation. The American Orthopaedic Foot and Ankle Surgeons (AOFAS)score was used for evaluation of the function before and after operation and the balance system evaluate the proprioception function. The two ankle ligament specimens from fresh frozen body and the tissue samples from operation were used for investigation of the structure and distribution of the sensory corpuscles by using histology and immunohistoehemical staining. Results The sections were evaluated with a microscope and an image analyzer. Labeled nerve endings were mapped, measured and categorized. Type Ⅰ ( Ruffini-like ending) , type Ⅱ ( Pacinin-like corpuscle ) and type Ⅳ- (noncorpuscular) nerve endings could be identified in all the lateral ankle ligaments, with majority of types Ⅰ and Ⅱ nerve endings.These receptors were distributed primarily over the superficial ligament and near the bony attachments.There was statistical difference between preoperative and postoperative sway distance as well as between preoperative and postoperative AOFAS score. Conclusions This study suggests that the longer history,severer symptoms and lower AOFAS score may lead to the severer injury of the mechanical proprioceptors.The proprioceptor injury is correlated with ankle joint instability and the ligament reconstruction is effective to avoid the repeated injury of the proprioceptor. Key words: Ankle joint; Ligaments; Mechanoreceptors; Proprioception; Immunohistochemistry

Wild-type transthyretin-derived amyloidosis in various ligaments and tendons

Transthyretin-derived amyloid deposition is commonly found in intercarpal ligaments of patients with senile systemic amyloidosis. However, the frequency of transthyretin-derived amyloid deposits in ligaments of other tissues remains to be elucidated. This study aimed to determine the frequency of amyloid deposition and the precursor proteins of amyloid found in orthopedic disorders. We studied 111 specimens from patients with carpal tunnel syndrome (flexor tenosynovium specimens), rotator cuff tears (rotator cuff tendon specimens), and lumbar canal stenosis (yellow ligament specimens). To identify amyloid precursor proteins, we used immunohistochemical staining with antibodies that react with transthyretin, immunoglobulin light chain, amyloid A protein, and β(2)-microglobulin. By means of Congo red staining, we identified 47 (42.3%) amyloid-positive samples, 39 of which contained transthyretin-derived amyloid (18 flexor tenosynovium specimens, 5 rotator cuff tendon specimens, and 16 yellow ligament specimens). Genetic testing and/or clinical findings suggested that all patients with transthyretin amyloid deposits did not have familial amyloidotic polyneuropathy. The occurrence of amyloid deposition in those tissues depended on age. These results suggest that transthyretin-derived amyloid deposits may occur more frequently in various ligaments and tendons than originally expected. In the future, such amyloid deposits may aid determination of the pathogenesis of ligament and tendon disorders in older patients.

Notch Radius and Specimen Size Effects on Fracture Toughness of Low Alloy Steel

The present work is amid to investigate the effect of notch root radius ρ and specimen size (thickness B and ligament b) on the apparent fracture toughness KI,app. Series of fracture tests on non standard compact tension CT specimen of AISI 4340 low alloy steel with different values of notch root radius (ρ=0.08 mm-3 mm) and ligament size/crack length to the specimen width ratio (a/W=0.1-0.9) have been conducted to measure the apparent fracture toughness KI,app. The experimental results show that KI,app depends on ρ and specimen size (B and b). There is a critical notch root radius ρc under which the apparent fracture toughness becomes independent of the notch radius ρ. Two empirical models have been proposed to transfer the data among specimens of different notch radii and predict the experimental values of KI,app considering the effect of ρ value. Also, Two models have been developed to transfer the data among specimens with different sizes and predict KI,app considering the effect of specimen thickness B, specimen ligament band the combined effect of B and b values. The combined effec –based model is developed by modifying the E 1921 standard equation (that is usually used to predict the thickness effect only). The models predictions are in good agreement with the present work experimental results and results reported in the literature.