Ultimate Failure Load Research Articles

Role of low-intensity pulsed ultrasound in regulating macrophage polarization to accelerate tendon-bone interface repair.

Low-intensity pulsed ultrasound (LIPUS) has been proven to accelerate the healing of the tendon-bone interface (TBI), and macrophages are considered to play an important regulatory role. This study was designed to explore the polarization of macrophages during treatment of TBI injury with LIPUS. In a rat model of rotator cuff tear, LIPUS or mock sonication (controls) was administered from 1 week postoperatively. The supraspinatus-supraspinatus tendon-humerus complexes were harvested for further evaluation at different time points for measures such as new bone formation, TBI maturity, ultimate failure load and stiffness, and types of macrophages. In vitro, bone marrow-derived macrophageswere cultured, and polarization was identified after stimulation with or without LIPUS (the LIPUS or control groups, respectively). Two weeks posttreatment, the LIPUS group showed higher bone volume/total volume ratios and better TBI maturity scores. Six weeks posttreatment, the failure load of the LIPUS group was significantly higher than that of the control group. LIPUS also accelerated initial inflammatory macrophage accumulation and facilitated anti-inflammatory macrophage polarization (M2) in the late period. In the in vitro macrophage polarization model, the LIPUS group showed a higher proportion of M2 macrophages and mRNA expression of anti-inflammatory genes than the control group, while there was no significant difference in the proinflammatory macrophages between the two groups. Our observations revealed that macrophage polarization may be a potential mechanism of LIPUS treatment for TBI repair.

A Meta-Analysis of Biomechanical Studies for Suture Button Pullout Versus Suture Anchor Repair of Flexor Digitorum Profundus Avulsions.

There is no current consensus on which of the two most common flexor digitorum profundus (FDP) avulsion repair constructs, via suture button pullout (SBP) or suture anchor (SA), is biomechanically superior. Our purpose was to compare these repair methods via systematic review and meta-analysis of available literature. We performed a Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA)-guided systematic review of PubMed, the Cochrane library, and Embase. We only included studies with direct comparison data for both techniques. We performed a meta-analysis comparing the reported biomechanical results using pooled data for initial repair stiffness (N/mm), gap formation (mm), and ultimate load to failure (N). Seven studies met inclusion criteria, including a total of 201 cadaveric specimens. Four studies reported initial construct stiffness, with pooled analysis showing superiority for SA repairs (P < .05). Four studies evaluated gap formation, with pooled analysis demonstrating less gapping with SA repair (P < .05). Mean gap formation was 2.4 (±1.4) mm and 3.9 (±2.0) mm for the SA and SBP groups, respectively. All 7 studies assessed load to failure, with pooled analysis revealing no significant difference between groups (P > .05). We lacked statistical power to determine equivalence between techniques for load to failure. Both groups had failure values significantly lower than the native FDP. Via meta-analysis, there was increased initial construct stiffness and less gap formation for SA compared to SBP for FDP reinsertion, with no significant differences for ultimate failure load.

An investigation of shear failure in welded channel and angle brace members

Shear yielding (SY) and shear rupture (SR) are base metal failure modes in welded connections of brace members to gusset plates. Although gusset plated connections have been extensively investigated in the past nonetheless, the shear failure limit states of welded brace members have not received significant attention. This paper aims to shed some light on the shear failure mechanism and strength of welded brace members consisting of single and double channels and angles. For this purpose, a nonlinear finite element (FE) model with ductile damage simulation is developed and validated against the authors’ experiments and other available test results. Then an extensive parametric study using 432 models is performed. The yield and ultimate failure loads of the members have been determined. The results show that the code-specified approach to predict the shear strength of members is very conservative and does not consider the existing tensile strength contribution of the members. In addition, the commonly assumed failure patterns are inaccurate. FE findings show that the SY limit state always occurs prior to SR with about 50% less strength. Moreover, it is found that the yielding mechanism in the SY limit state is limited to the connection region. The shear failure behavior under compression loading and the effects of connection geometry have also been examined. Based on extensive FE analyses, it is recommended to ignore the SY limit check in designing brace members. Moreover, a modification is proposed to the conventional SR formula using a block shear (BS) framework that includes tensile areas to predict the member’s strength more accurately. Application of the proposed recommendations in the seismic design of brace-to-gusset connections results in a more economical connection.

Comparison of biomechanical analysis of four different tibial tunnel fixations in a bovine model

BackgroundTo determine the ideal fixation technique for an ACL reconstruction with a hamstring graft, multiple studies have been undertaken to define the initial biomechanical properties of tibial fixation. PurposeThe aim of this study was to compare the biomechanical properties of tibial fixation methods by creating single or hybrid systems. MethodsBovine tibias and forefoot digital extensor tendons were prepared with four different tibial anterior cruciate ligament fixation methods and compared biomechanically. Fixation materials included polyethylene Ultrabraid high-strength sutures, Biosure interference screws (Smith and Nephew, Memphis, TN, USA), staples (Smith and Nephew, Richards Regular Fixation Staples without Spikes, Memphis, TN, USA), and knotless suture anchors (Multifix-S PEEK) (Smith and Nephew, Memphis, TN, USA). Four groups (n = 5 specimens) were established – group I: single fixation with interference screws; group II: single fixation with knotless anchors; group III: hybrid fixation with interference screws and staples; group IV: hybrid fixation with interference screws and knotless anchors. Each specimen underwent evaluations for cyclic displacement, cyclic stiffness, initial loading strength, ultimate failure load, pull-out displacement, and pull-out stiffness. ResultsAll specimens completed cyclic loading and load-to-failure. The cyclic displacement in group II, which had a single fixation, indicated significantly greater elongation compared with the other groups (P = 0.002). The hybrid systems were more rigid than the single systems in terms of cyclic stiffness, and no statistically significant difference was observed between the hybrid systems (P = 0.461). Group IV was significantly superior in terms of the ultimate failure load (P = 0.004). No statistically significant differences were noted between the groups for pull-out displacement or pull-out stiffness. ConclusionSingle fixation with bioscrews as an in-tunnel tibia fixation method was as successful as hybrid systems. Multifix-S PEEK knotless suture anchors, which can be combined with bioscrews, can be a superior fixation alternative due to its flexibility and ultimate failure load values.

Biomechanical Study of Arthroscopic All-Inside Anterior Talofibular Ligament Suture Augmentation Repair, Plus Suture Augmentation Repair and Anterior Tibiofibular Ligament's Distal Fascicle Transfer Augmentation Repair.

Objective: To explore the biomechanical efficacy of arthroscopic all-inside anterior talofibular ligament (ATFL) suture augmentation repair, plus suture augmentation repair and anterior tibiofibular ligament-distal fascicle (ATiFL-DF) transfer augmentation repair, so as to provide a basis for the accurate selection of ATFL repair in clinical practice. Methods: Twenty-four (12 pairs) fresh frozen human cadaver ankle specimens were used. Six of the ankle specimens were set as the normal group, and the other 18 ankle specimens were used to establish ATFL injury models. The ATFL was then repaired using arthroscopic all-inside ATFL suture augmentation repair (suture augmentation group), plus suture augmentation repair (plus suture augmentation group) and ATiFL-DF transfer augmentation repair (biological augmentation group), respectively. After the repaired ATFL was separated, the ankle specimens were fixed on an electronic universal testing machine with a customized fixture for the tensile test, and the ultimate failure load (N) and stiffness (N/mm) of the ankle specimens were compared. Results: The ultimate failure load of the plus suture augmentation group (229.3 ± 66.7 N) was significantly higher than that in the normal group (148.2 ± 39.4 N, p = 0.045) and the biological augmentation group (131.3 ± 38.8 N, p = 0.013). There was no statistical difference in ultimate failure load between the suture augmentation group (167.2 ± 47.2 N), the normal group and the biological augmentation group. The stiffness of the plus suture augmentation group (26.2 ± 8.2 N/mm) was significantly higher than that in the normal group (12.1 ± 3.8 N/mm, p = 0.005) and the biological augmentation group (12.7 ± 5.2 N/mm, p = 0.007). The stiffness of the suture augmentation group (23.6 ± 7.0 N/mm) was significantly higher than that in the normal group (p = 0.024) and the biological augmentation group (p = 0.033). There was no statistical difference in stiffness between the plus suture augmentation group and the suture augmentation group, and no statistical difference in stiffness between the normal group and the biological augmentation group. Conclusions: The tensile strength and rigidity of plus suture augmentation repair were significantly better than those of normal ATFL, suture augmentation repair and ATiFL-DF transfer augmentation repair. Suture augmentation repair can obtain tensile strength similar to normal ATFL and ATiFL-DF transfer augmentation repair, and suture augmentation repair can obtain rigidity significantly better than normal ATFL and ATiFL-DF transfer augmentation repair. ATiFL-DF transfer augmentation repair can obtain tensile strength and rigidity similar to normal ATFL.

Biomechanical comparison between various screw fixation angles for Latarjet procedure: a cadaveric biomechanical study.

The Latarjet procedure is a reliable treatment for the management of anterior glenohumeral instability with glenoid bone loss. However, the biomechanical properties of different fixation angles between screw and glenoid surface (α angle) have rarely been studied. The aim of the study was to investigate and compare the fixation stability, failure load, and failure mechanism between different α angles for Latarjet procedures, which were performed on cadaver specimens. Twenty-four shoulder specimens (8 in each of 3 groups) were dissected free of all soft tissue, and a 25% glenoid defect was created. The coracoid process was osteomized and fixed with 2 screws at 3 different α angles: 0° (group A), 15° (group B), and 30° (group C). Specimens were mounted to a testing apparatus, and cyclic loading (100 cycles at 1Hz) was applied with a staircase protocol (50, 100, 150, and 200N). Gross graft displacement and interface displacement were measured. The ultimate failure loads and failure mechanisms were recorded. There was no significant difference in gross displacement under any cyclic load between 3 groups. However, a significant larger interface displacement was noted in group C than in group A in 150-N cyclic loading (P=.017). Under failure strength testing, all 24 specimens failed because of screw cutout from the glenoid, and the ultimate failure load was similar among the three groups. Compared with the 0° α angle, the displacement after cyclic loading did not significantly increase when the α angle was increased to 15° but significantly increased at 30° for Latarjet procedures, which were performed on cadaver specimens. The results suggest that surgeons should apply the screws as parallel as possible to the glenoid surface when performing the Latarjet procedure. Although mild deviation may not reduce fixation stability, α angles greater than 30° should be avoided.

Effects of a graphene oxide-alginate sheet scaffold on rotator cuff tendon healing in a rat model

Natural polymer scaffolds used to promote rotator cuff healing have limitations in terms of their mechanical and biochemical properties. This animal study aimed to investigate the effects of combined graphene oxide (GO) and alginate scaffold and the toxicity of GO on rotator cuff healing in a rat model. First, the mechanical properties of a GO/alginate scaffold and a pure alginate scaffold were compared. The in vitro cytotoxicity of and proliferation of human tenocytes with the GO/alginate scaffold were evaluated by CCK-8 assay. For the in vivo experiment, 20 male rats were randomly divided into two groups (n = 10 each), and supraspinatus repair was performed: group 1 underwent supraspinatus repair alone, and group 2 underwent supraspinatus repair with the GO/alginate scaffold. Biomechanical and histological analyses were performed to evaluate the quality of tendon-to-bone healing 8weeks after rotator cuff repair. The GO/alginate scaffold exhibited an increased maximum load (p = .001) and tensile strength (p = .001). In the cytotoxicity test, the cell survival rate with the GO/alginate scaffold was 102.08%. The proliferation rate of human tenocytes was no significant difference between the GO/alginate and alginate groups for 1, 3, 5, and 7days. Biomechanically, group 2 exhibited a significantly greater ultimate failure load (p < .001), ultimate stress (p < .001), and stiffness (p < .001) than group 1. The histological analysis revealed that the tendon-to-bone interface in group 2 showed more collagen fibers bridging, tendon-to-bone integration, longitudinally oriented collagen fibers, and fibrocartilage formation than in group 1. A small amount of GO added to alginate improved the mechanical properties of the scaffold without evidence of cytotoxicity. At 8 weeks after rotator cuff repair, the GO/alginate scaffold improved tendon-to-bone healing without causing any signs of toxicity in a rat model.

Behavior of Waste Glass Powder in Concrete Deep Beams with Web Openings

Waste Glass Powder (WGP) could be used as a cement replacement additive to manufacture concrete and solving the problem of environmental pollution. The experimental program was made up of ten simply supported reinforced High-Strength Concrete (HSC) deep beams tested under static loadings. Five beams were with WGP, while the other five beams were without WGP. Eight beams had web openings while two reference beams were without openings. The principal studied parameters were the effect of using WGP, and the location and size of web openings. Using the three-dimensional finite element computer program ABAQUS, a numerical simulation for comparing the shear strength and behavior of tested deep beams has been suggested. The comparison between experimental failure loads of studied beams with that estimated by the Strut-and-Tie model was carried out. Three codes of practice were used to make this comparison: the American Concrete Institute (ACI 318-19), the New Zealand Code (NZS-06), and the Japan Society of Civil Engineering (JSCE-07). The results showed that using WGP in similar deep beams with web openings enhances the cracking shear strength (by about 17–25%) and the ultimate shear strength (by about 12–41%). The improvement in the ultimate failure load could be attributed to the developed concrete microstructures caused by WGP’s very fine grains, producing further gel, and decreasing the number of voids in the concrete matrix. The suggested finite element simulation accurately predicts the behavior of HSC deep beams with and without WGP beams and with web openings.

The recombinant human fibroblast growth factor-18 (sprifermin) improves tendon-to-bone healing by promoting chondrogenesis in a rat rotator cuff repair model.

Rotator cuff healing is improved by reconstructing the fibrocartilaginous structure of the tendon-to-bone enthesis. Fibroblast growth factor (FGF)-18 (sprifermin) is a well-known growth factor that improves articular cartilage repair via its anabolic effect. This study aimed to investigate the effect of recombinant human FGF-18 (rhFGF-18) on the chondrogenic differentiation of human bone marrow mesenchymal stem cells (hBMSCs) invitro and tendon-to-bone healing in a rat model of rotator cuff repair. Histological and reverse transcription-quantitative real-time polymerase chain reaction analyses of chondral pellets cultured with different concentrations of rhFGF-18 were performed. Bilateral detachment and repair of the supraspinatus tendon were performed on rats. The rats were administered 0.2mL of sodium alginate (SA) hydrogel with (rhFGF-18/SA group, n=12) or without (SA group, n=12) 20μg of rhFGF-18 into the repaired side. The simple repair group (n=12) served as a control. At 4 and 8weeks after surgery, histological analysis and biomechanical tests were performed. After chondrogenesis induction, compared with the control group, 10ng/mL of rhFGF-18 increased pellet volume significantly (P=.002), with improved histological staining. It was noted that 10ng/mL of rhFGF-18 upregulated the mRNA expression (relative ratio to control) of aggrecan (2.59±0.29, P<.001), SRY-box transcription factor 9 (1.88±0.05, P<.001), and type II collagen (1.46±0.18, P=.009). At 4 and 8weeks after surgery, more fibrocartilage and cartilaginous extracellular matrix was observed in rhFGF-18/SA-treated rats. The semiquantitative data from picrosirius red staining test were 31.1±4.5 vs. 61.2±4.1 at 4weeks (P<.001) and 61.5±2.8 vs. 80.5±10.5 at 8weeks (P=.002) (control vs. rhFGF-18/SA). Ultimate failure load (25.42±3.61N vs. 18.87±2.71N at 4weeks and 28.63±5.22N vs. 22.15±3.11N at 8weeks; P=.006 and P=.03, respectively) and stiffness (18.49±1.38N/mm vs. 14.48±2.01N/mm at 8weeks, P=.01) were higher in the rhFGF-18/SA group than in the control group. rhFGF-18 promoted chondrogenesis in the hBMSCs invitro. rhFGF-18/SA improved tendon-to-bone healing in the rats by promoting regeneration of the fibrocartilage enthesis. rhFGF-18 (sprifermin) may be beneficial in improving tendon-to-bone healing after rotator cuff repair.

Computational analysis of bidirectional carbon fibre/epoxy nanocomposites using different failure criteria

Numerical analysis provides an opportunity to solve complex problems using mathematical models. The increasing trend of numerical simulations supports many industries and research organisations to reduce the experimental work. In the present study, considering the positive aspects of numerical analysis, investigations have been done using different failure criteria on the carbon fibre/epoxy composites. Various failure criteria have been discussed that can be used for unidirectional and bidirectional fibre reinforced polymer composites. In this study, the best-suited failure criteria, i.e. Maximum stress, Tsai-Wu and Hashin criteria were combined with the progressive damage analysis to investigate the failure of bidirectional woven carbon fiber/epoxy polymer composites. The experimental validations were also done for numerical predictions. It was found that the Hashin failure criterion gave the results closest to the experimental failure analysis of pin joints. In pin joints prepared from carbon fiber/epoxy composite laminates, Hashin failure criteria predicted the increment in ultimate failure loads in the range of 12–16% for higher values of width to diameter (W/D) and edge to diameter (E/D) ratios. For pin joints prepared from multiwalled carbon nanotubes (MWCNTs) added carbon fiber/epoxy composite laminates, the prediction given by Hashin failure criteria was in the range of 15–19%.

Anterior to Posterior Bone Plug Suture Tunnels Provide Optimal Biomechanics for Bone−Patellar Tendon−Bone Anterior Cruciate Ligament Graft

PurposeTo evaluate different bone−patellar tendon−bone (BPTB) plug suture configurations for pull through strength, stiffness, and elongation at failure in a biomechanical model of suspensory fixation.MethodsForty nonpaired, fresh-frozen human cadaveric BPTB allografts with an average age of 65.6 years were tested. Tensile testing was performed with the use of a custom-designed fixture mounted in a dynamic tensile testing machine. A preload of 90 N was applied to the graft and held for 5 minutes. Following this, a tensile load-to-failure test was performed. The ultimate failure load, elongation at failure, and mode of failure were recorded, and the resulting load–elongation curve was documented.ResultsThe drill tunnel through the cortical surface (anterior to posterior) was found to be significantly stronger than the drill tunnel through the cancellous surface (medial to lateral). There were no significant differences found when comparing the strength of the suture augmentation through the tendon and the drill tunnel alone (P = .13 among cancellous groups, P = .09 among cortical groups). The cortical drill tunnel with suture augmentation through the tendon showed significantly greater elongation values (13.7 ± 3.2) at failure when compared with either the cancellous or cortical drill tunnel only test groups (P = .0003 compared with cancellous alone, P = .009 when compared with cortical alone). Conclusions: The BPTB suture configuration with an anterior to posterior–directed suture tunnel without a suture through tendon augmentation provides the optimal strength and stiffness while minimizing graft elongation after fixation in a biomechanical model. This configuration is best for preventing suture pull through and failure when passing sutures through the BPTB plug.Clinical RelevanceThis study biomechanically evaluates the optimal suture configuration in the proximal bone plug for suspensory fixation in the setting of BPTB grafts.

Arthroscopic Meniscal Healing following Medial Meniscus Posterior Root Repair: A Comparison between Two Suture Materials.

Recently, transtibial pullout repair of the medial meniscus (MM) posterior root tear (PRT) has become widely accepted and provides satisfactory clinical outcomes. Widening after cyclic loading or ultimate failure load using different suture materials and configurations has been studied. However, no study has compared the clinical outcomes using different suture materials. This study aimed to evaluate the clinical outcomes after performing MMPRT pullout repair using different suture materials. We hypothesized that better clinical outcomes would be achieved using ultra-high molecular weight polyethylene (UHMWPE) tape compared with a normal polyester suture. Thirty-seven patients who underwent MM posterior root repair between November 2019 and May 2020 were retrospectively investigated. Pullout repair was performed using a hollow no. 0 polyester suture (n = 14) and UHMWPE tape (n = 23). Clinical outcomes were assessed preoperatively and at 1 year postoperatively, using the Lysholm knee score, Knee Injury and Osteoarthritis Outcome Score, and visual analogue scale (VAS) pain score. The meniscal healing status was assessed using an arthroscopic scoring system (range: 0-10). All clinical scores were improved significantly in both groups. However, significantly higher meniscal healing scores and decreased VAS pain scores were observed in the UHMWPE group (7.3 ± 0.9 and 7.7 ± 11.3, respectively) than in the polyester group (5.6 ± 2.1 and 18.4 ± 18.6, respectively; p < 0.01). Suture cut-out and loss of the root continuity were observed in some cases (three cases [21.4%] in the polyester suture group and one case [4.3%] in the UHMWPE tape group). Both suture materials led to satisfactory clinical outcomes at 1 year postoperatively, whereas the UHMWPE tape was useful for obtaining good meniscal healing and decreasing the VAS pain score.

UPGRADING THE PERFORMANCE OF DEFECTED BEAMS BY USING SLURRY INFILTRATION FIBER-REINFORCED CONCRETE AS A STRENGTHENING SOLUTION

One of the ways to increase the service life or upgrade the concrete buildings is by strengthening and repairing techniques. There are many methods of strengthening, such as using slurry infiltration fiber-reinforced concrete (SIFCON). This study cast eight normal reinforced concrete beams of 100 × 150 × 1000 mm. Seven are pre-loaded to 60% of their ultimate load, and the eighth is loaded to its ultimate load. Six beams are repaired with fresh and precast SIFCON layers in different configurations (bottom and jacketing). However, for comparison reasons, two beams are repaired with carbon fiber-reinforced polymer (CFRP) and steel fiber concrete. All beams are tested under a two-point flexural load. The parameters (ultimate load, ductility, toughness, stiffness, crack width, residual strength, and mode of failure) are investigated. The purpose of the study is to use a compatible cement-based material with new techniques for strengthening or repairing concrete members. The results showed that the new techniques significantly improved the behavior of the pre-loaded beams, and SIFCON layers (fresh or precast) could compensate for the failure in the steel reinforcement and be used as external reinforcement.

Optimizing the Pulvertaft Weave Technique: A Comprehensive Systematic Review of Comparative Biomechanical Studies.

The Pulvertaft weave continues as a staple technique for tendon coaptations. Many have proposed minor alterations to the original technique to improve its strength, although a lack of consensus exists. The authors' aim was to explore how the number of weaves and suture characteristics contribute to the overall strength of the coaptation. A comprehensive electronic search was conducted using the PubMed, Cochrane Library, and Scopus databases. Criteria for inclusion consisted of cadaveric human or animal biomechanical studies evaluating ultimate failure load (in newtons) and the number of weaves, suture characteristics, tendon source, and number of coaptations. Weaves with minimum averages of 75 N were deemed successful, and those with greater than 120 N were considered high performing. A total of 347 tendon coaptations from 15 studies met inclusion criteria. Average strength by number of weaves was 36.4 N ( n = 52) for one weave, 54.2 N ( n = 58) for two weaves, 115.9 N ( n = 174) for three weaves, and 81.7 N ( n = 63) for four weaves. Statistical differences were observed between one and two weaves ( p < 0.0001); two and three weaves ( p < 0.0001); three and four weaves ( p < 0.003); and two and four weaves ( p < 0.0001). High-performing tendon transfers used three weaves, 3-0 or 4-0 braided sutures, and figure-of-eight or mattress core sutures. Contrary to the current dogma of "the more the better," the authors' findings show that Pulvertaft weave strength is optimized when three weaves are used to combine donor and recipient tendons. Braided sutures with either figure-of-eight or mattress sutures were associated with the highest strength of repair.

Structural behavior of MDF beams reinforced by unidirectional glass fiber reinforced thermoset polyurethane outer layers

In this study, the structural behavior of medium density fiber board (MDF) beams reinforced by unidirectional glass fiber reinforced thermoset polyurethane outer layers is investigated by conducting beam bending and vibration tests followed by a parametric study. First, the MDF material properties are determined by 3 point bending and cantilever beam vibration tests. Then the same tests are conducted on the composite sandwich beam specimens produced by hand layup technique and the level of increase in overall stiffness and the ultimate failure loads are determined. The experimental results obtained are found out to be in good agreement with the analytical results and the numerical results obtained using a 1D shear deformable beam model. Finally, a parametric study is conducted to determine the influence of FRP reinforcement for different span lengths and fiber volume ratios. The results obtained from this study show that reinforcing MDF beams by FRP outer layers may considerably increase the flexural stiffness for all span lengths but the ultimate failure load may not be increased for short span lengths due to core shear failure, especially when there is no constraint on maximum displacement.

Biomechanical Comparison of a Horizontal Mattress, Cross Suture and Vertical Mattress for Repair of a Tendon Weave in a Porcine Model.

Background: An effective suture method enables early active motion exercises and optimal post-surgical outcomes. The aim of this study is to evaluate the tensile strength of three suture configurations - horizontal mattress (HM), vertical mattress (VM) and a cross suture for repair of a tendon weave. We hypothesised that the direction of mattress sutures relative to the tendon fibres would affect the tensile strength of tendon repair. Methods: Using porcine flexor tendons and the same number of surgical sutures, three tendon weave constructs differing in the method of suture were compared: HM suture configuration (conventional technique), cross-stitch (CS) configuration (conventional technique) and VM suture configuration (novel technique). Ten pairs of each group were mounted in a material testing machine and subjected to a simple tensile test and a cyclic loading test for their biomechanical comparison. Results: The VM group and CS group had significantly higher ultimate failure load, linear stiffness and fatigue strength as compared to the HM group. The failure mode was suture breakage or tendon rupture for the VM and the CS group, while the suture pullout of the tendon only occurred in the HM group. Conclusion: Among the three techniques used for repair of a tendon weave, the VM suture technique was demonstrated to have the greatest tensile strength and least associated with suture pull-out. The direction of the mattress suture in relation the direction of tendon fibres affects the strength of repair.

Biomechanical Evaluation of Suture Tape Internal Brace Reinforcement of Soft Tissue Allografts for ACL Reconstruction Using a Porcine Model.

Background:Internal bracing of anterior cruciate ligament (ACL) surgery is a newer concept gaining popularity.Purpose/Hypothesis:To assess the biomechanical performance of soft tissue ACL reconstruction allografts reinforced with suture tape. It was hypothesized that load to failure would increase and cyclic displacement would decrease at time zero in the constructs reinforced with internal brace suture tape compared with those without suture tape augmentation.Study Design:Controlled laboratory study.Methods:We performed ACL reconstruction on porcine knees using bovine extensor tendon soft tissue allografts: 10 knees without (control) and 10 knees with (reinforced) suture tape reinforcement. An all-inside reconstruction technique was utilized with retrograde tunnel creation. An adjustable-loop device was used for femoral and tibial fixation of all grafts. The suture tape was placed through the tension loop in the femoral fixation construct and independently fixed in the tibia with an interference screw anchor. For each specimen, the authors recorded ultimate load, yield load, stiffness, cyclic displacement, and mode of failure. Outcomes between groups were compared using the Student t test.Results:There was a 33% decrease in mean cyclic displacement in the specimens with reinforced grafts (reinforced vs control: 3.9 ± 0.7 vs 5.8 ± 1.5 mm; P = .001). The reinforced grafts also had a 22% higher mean ultimate load (921 ± 180 vs 717 ± 122 N; P = .008) and a 25% higher mean yield load (808 ± 201 vs 602 ± 155 N; P = .020). There was no significant difference in stiffness between the reinforced versus nonreinforced grafts (136 ± 16 vs 132 ± 18 N/mm; P = .617). Three of the 10 control specimens failed at the graft, compared with 1 of 10 reinforced grafts. All other constructs in both groups failed at the tibial fixation site.Conclusion:Suture tape reinforcement of soft tissue grafts significantly decreased cyclic displacement while significantly increasing ultimate and yield loads without increasing graft construct stiffness during biomechanical testing at time zero in a porcine animal model.Clinical Relevance:The improved biomechanical performance of suture tape–reinforced graft constructs could allow patients to participate in earlier advancement of aggressive rehabilitation and potentially reduce failure rates as graft remodeling progresses.

The double-lasso loop technique of Biceps tenodesis has lower displacement after cyclic loading, compared to interference screw fixation: Biomechanical analysis in an ovine model.

Biceps tenodesis is an effective treatment for symptomatic long head of biceps tendon pathology. Recently the arthroscopic "double lasso-loop" suture anchor (DLSA) technique was described, advantaged by reduced cost, complexity, and operative time. We aimed to compare the in vitro strength of DLSA with conventional interference screws (IS). A biomechanical analysis was conducted on 14 sheep shoulders (8 DLSA, 6 IS), consisting of a 500-cycle cyclic loading experiment of 5-70 N and ultimate failure load (UFL) test where each specimen was pulled until failure. Displacement (mm) was recorded every 100 cycles, while stiffness and UFL were observed. Cyclic displacement was significantly lower with DLSA at 100 cycles, but not above. During the UFL test, IS was stiffer (27.68 ± 6.56 N/mm versus 14.10 ± 5.80 N/mm, p = .005) and had higher UFL (453.67 ± 148.55 N versus 234.22 ± 44.57 N, p = .001) than DLSA. All DLSA failures occurred with suture/anchor pull-out, while all IS constructs failed at the muscle/tendon. Comparison of the novel DLSA technique with a traditional IS method found lower initial displacement. While our IS constructs could withstand higher UFL, peak load characteristics of DLSA were similar to previous ovine studies. Hence, the DLSA technique is a viable alternative to IS for biceps tenodesis with its purported non-biomechanical advantages.

Numerical Investigation on Shear Performance of Reinforced Concrete Beam by Using Ferrocement Composite

This study presents an extensive analytical investigation of the shear performance of reinforced concrete beams by using ferrocement composite as transverse reinforcement. Nonlinear finite element simulation was conducted in Abaqus 6.14 software package. Fifteen beam models were selected under two-point loading. The main parameters considered includes the diameter, spacing, number of layers of wire mesh, and its combination with stirrups. The results testified that as the diameter and number of layers of wire mesh increased, the ultimate failure load, shear capacity, and stiffness of the model specimen also increased. However, as the number of layers becomes greater than three, no significant change happens in the shear performance of the beam. In another way, the failure load, shear capacity, and stiffness of the beam models are decreased, as the spacing between wire mesh is increased. Furthermore, the study confirmed that under the same weight criteria, the shear performance of RC beam specimens with wire mesh and its combination with stirrups as shear reinforcement is greater than specimens with stirrups only. Finally, the sensitivity analysis is conducted in MS excel to access the effect of each independent variable on the ultimate failure load of the RC beam.

Nonlinear numerical simulation and experimental verification of bondline strength of CFRP strips embedded in concrete for NSM strengthening applications

AbstractThis article presents results of an investigation that focuses on assessing bondline strength of carbon/epoxy fiber reinforced polymeric (CFRP) precured strips embedded in concrete for near‐surface‐mounting (NSM) strengthening applications. In this study, experimental evaluation and nonlinear numerical analysis of CFRP/concrete interfacial bond behavior are investigated. In this study, 15 pull‐out tests were performed on different reinforced concrete (RC) U‐shaped column specimens with different NSM groove configurations to evaluate the effect of groove size, groove depth, and adhesive bondline thickness on overall performance of the CFRP‐NSM system and to identify the optimum groove dimensions. Experimental results indicated that changing groove geometries of the NSM‐FRP reinforcements significantly affect bondline strength and associated mode of failures of NSM‐CFRP system. It was also shown that increasing bondline length lead to an increase in ultimate failure load and CFRP rupture strain. Based on results of this study, NSM materials with lower longitudinal moduli and higher rupture strains (e.g., E‐glass/epoxy or basalt/epoxy), may increase toughness and enhance performance of the NSM strengthening system.