Peak Failure Load Research Articles

Fabric controls on fracture surface roughness of an architected rock material

Fluid flow through fractures is intimately linked to the fracture surfaces that define the void geometry through which fluids flow. Thus, an understanding of what controls fracture surface roughness is essential to the development of models for predicting fluid transport through fractured rock. The difficulty in predicting surface roughness arises from the complexity of rock which is inherently heterogeneous and nonuniform in composition, fabric, and structural components, even when samples are acquired from the same rock mass. Here, a benchmarked-simulation approach motivated from geo-architected 3D printed synthetic gypsum rocks is used to provide insight into the competing contributions from fabric and layering on fracture roughness formation. Simulation results from a discrete element model (Particle Flow Code, Itasca Consulting Group, Inc.) clearly indicate that the relative orientation between mineral layers and in-layer mineral fabric, and the variability in mineral bonding strengths determine whether anisotropic corrugated surfaces or isotropic surfaces are formed. Weak mineral layers oriented perpendicular to the applied load resulted in strong roughness anisotropy. Peak failure loads were found to vary up to 30% depending on the strength of the mineral fabric at the location of fracture initiation, which provides insight into the observed high variability in strength values of natural rock. The uniqueness of induced fracture roughness and peak failure load is intimately linked to layering, mineral fabric, and their distribution in the rock. These findings have important implications for any architected material fabricated through serial printing of layers with local compositional heterogeneity.

Thickness of simple calcaneal tuberosity avulsion fractures influences the optimal fixation method employed.

This study aimed to establish the optimal fixation methods for calcaneal tuberosity avulsion fractures with different fragment thicknesses in a porcine model. A total of 36 porcine calcanea were sawed to create simple avulsion fractures with three different fragment thicknesses (5, 10, and 15 mm). They were randomly fixed with either two suture anchors or one headless screw. Load-to-failure and cyclic loading tension tests were performed for the biomechanical analysis. This biomechanical study predicts that headless screw fixation is a better option if fragment thickness is over 15 mm in terms of the comparable peak failure load to suture anchor fixation (headless screw: 432.55 N (SD 62.25); suture anchor: 446.58 N (SD 84.97)), and less fracture fragment displacement after cyclic loading (headless screw: 3.94 N (SD 1.76); suture anchor: 8.68 N (SD 1.84)). Given that the fragment thickness is less than 10 mm, suture anchor fixation is a safer option. Fracture fragment thickness helps in making the decision of either using headless screw or suture anchor fixation in treating calcaneal tuberosity avulsion fracture, based on the regression models of our study.

Probabilistic investigation into brittle fracture of functionally graded materials using phase-field method

Modelling fracture using numerical techniques based on discrete modelling is complex as it requires tracking of progressing discontinuities in field parameters. Phase-field method for fracture is based on the variational framework and represents discontinuous crack surfaces by a damage variable that diffuses onto the crack surface. This approach offers the advantage of modelling crack where multiple crack nucleation, branching and coalescence can be determined without prior knowledge of the crack path. In this work, a probabilistic approach is used to predict the crack growth response in functionally graded material media when the mechanical properties and geometric parameters are random independent variables. Numerical implementation based on the standard phase-field method is employed in a finite element framework to model crack growth in functionally graded brittle materials. Peak failure loads are estimated within acceptable limits due to dispersion in system properties. Benchmark problems are solved to demonstrate the applicability of this technique. The proposed approach is advantageous as no further intensive computations are needed after the initial evaluation of probabilistic measures for predicting dispersion in fracture propagation when material and geometric properties exhibit scatter.

Mechanical performances of composite orthogrid stiffened cylinder manufactured by an improved method

With high specific strength and stiffness, composite orthogrid stiffened cylinder (COSC) possesses excellent potential in the aerospace industry. However, the traditional silicone mold preparation methods have poor manufacturing accuracy and a low reuse rate of the mold. This work presents an improved COSC manufacturing method based on a combined metal mold and prepreg laying process. High-precision COSCs with intersection fillets were manufactured by the improved method. Axial compression was performed to reveal the strength and failure mode of the cylinder. Rib fracture and end delamination are the primary failure modes of the COSC under compression. Compared with relevant cylinders, the peak failure load, specific compression strength, and compression stiffness of the cylinder are significantly improved. Fillets wrapped around the intersection can effectively protect the fragile intersection roots. On this basis, an explicit dynamic simulation method simultaneously considering linear buckling mode and Hashin failure criterion is proposed to predict the peak failure load and fracture behavior of the cylinder.

Influence of zinc coating on nugget development and mechanical properties in dissimilar welded joints DP600 – AISI304 obtained by the RSW process

This paper researches the influence of zinc coating of galvanized DP600 steel (DP600G) on the nugget development and mechanical properties of dissimilar DP600 - AISI304 welded joints obtained by resistance spot welding process (RSW). The RSW evaluations consisted of determining, from the dynamic resistance curves, the different stages involved in nugget formation. The experimental results showed that the zinc coating on the DP600G steel has a significant influence on the time needed for the start of the nugget formation, two times higher than that used for non-galvanized steel. The expulsion time was delayed by 1.12 times. The presence of Zn in the DP600G/AISI304 welded joints produced smaller nugget diameters compared to the DP600/AISI304 joints for the same experimental conditions, however higher peak failure load values were obtained for the first. The causes of this unusual behavior are also analyzed in this paper.

Bone Staples Provide Favorable Primary Stability in Cortical Fixation of Tendon Grafts for Medial Collateral Ligament Reconstruction: A Biomechanical Study.

Background:The use of the interference screw (IFS) for the cortical fixation of tendon grafts in knee ligament reconstruction may lead to converging tunnels in the multiligament reconstruction setting. It is unknown whether alternative techniques using modern suture anchor (SA) or bone staple (BS) fixation provide sufficient primary stability.Purpose:To assess the primary stability of cortical fixation of tendon grafts for medial collateral ligament (MCL) reconstruction using modern SA and BS methods in comparison with IFS fixation.Study Design:Controlled laboratory study.Methods:Cortical tendon graft fixation was performed in a porcine knee model at the tibial insertion area of the MCL using 3 different techniques: IFS (n = 10), SA (n = 10), and BS (n = 10). Specimens were mounted in a materials testing machine, and cyclic loading for 1000 cycles at up to 100 N was applied to the tendon graft, followed by load-to-failure testing. Statistical analysis was performed using 1-way analysis of variance.Results:There were no statistical differences in elongation during cyclic loading or peak failure load during load-to-failure testing between BS (mean ± standard deviation: 3.4 ± 1.0 mm and 376 ± 120 N, respectively) and IFS fixation (3.9 ± 1.2 mm and 313 ± 99.5 N, respectively). SA fixation was found to have significantly more elongation during cyclic loading (6.4 ± 0.9 mm; P < .0001) compared with BS and IFS fixation and lower peak failure load during ultimate failure testing (228 ± 49.0 N; P < .01) compared with BS fixation.Conclusion:BS and IFS fixation provided comparable primary stability in the cortical fixation of tendon grafts in MCL reconstruction, whereas a single SA fixation led to increased elongation with physiologic loads. However, load to failure of all 3 fixation techniques exceeded the loads expected to occur in the native MCL.Clinical Relevance:The use of BS as a reliable alternative to IFS fixation for peripheral ligament reconstruction in knee surgery can help to avoid the conflict of converging tunnels.

Progressive deformation and pore network attributes of sandstone at in-situ stress states using computed tomography

Understanding the mechanism of microscopic failure of sandstone is exceptionally crucial for various engineering projects. The current study investigates the real-time high-resolution micro-computed tomography (m-CT) based microscopic failure attributes of sandstone under unconfined axial compression. Specimens of sandstone were analysed under varying loading conditions (zero load, 25%, 50%, 75% of the peak loads, and at peak failure loads) for analysing their effects on various petrophysical properties such as total pores, connected pores, non-connected pores, development of microfractures, and different pore network attributes such as pore radius, pore-volume, pore coordination number (CN), throat radius and throat channel length. Such an investigation enables us to explore the evolution of failure within sandstone under in-situ compression. The results showed the appearance of macrofractures and an increasing pattern of various pore-network attributes in the sandstone after 50% of the peak load. However, the non-connected pores gradually decreased with the rising loading stages. Finally, a negative correlation was obtained between tortuosity of sandsone with effective porosity and coordination number.

Resistance Spot Welding of Aluminum to Aluminum Clad Steel Sheet: Experimental and Theoretical Analysis

Abstract In order to increase the cross-tension to the tensile-shear peak load ratio, aluminum clad steel sheet produced by roll bonding, was used for resistance spot welding to Al-Mg aluminum alloy. The results showed that the weld nugget formed between the aluminum clad layer and Al-Mg base sheet was the load bearing area. Presence of the metallurgical bond between the steel sheet and the aluminum clad layer led to the formation of the Al/Fe intermetallic compound with the thickness less than ∼3.5 μm. This narrow intermetallic layer did not play a detrimental role in the weld strength and therefore, the cross-tension to the tensile-shear peak load ratio reached up to ∼0.5 at the maximum tensile-shear peak load which was an advance compared to the results in the literature. Theoretical analysis was relatively successful for prediction of the critical nugget diameter and the tensile-shear peak failure loads. While the tensile-shear peak load increased with the welding current up to ∼4 kN, the peak load in the cross-tension test remained relatively constant at ∼2 kN.

Flatwise Compression and Local Indentation Response of 3D-Printed Strut-Reinforced Kagome with Polyurethane Filling

Additively manufactured lattice structures are finding wider applications as core materials because of their high specific strength, modulus, and energy absorption. Strut-reinforced Kagome (SRK) structures have been shown to have good compressive performance compared with many existing lattice structures. Herein, the performance of acrylonitrile butadiene styrene (ABS) SRK lattice structures fabricated by fused deposition modeling under flatwise compression and local loading was investigated with and without polyurethane foam fillers. The SRK structure demonstrated abrupt failure at the joints in the vicinity of the face sheet, thereby reducing the energy absorption of the structure. The SRK filled with low-density polyurethane foam had no significant effect on peak failure load and moduli, whereas energy absorption per unit mass was higher by 16.5%. The SRK filled with high-density foam showed 116% increase in energy absorption. Similarly, a stronger indentation response was observed with high-density foam-filled SRK sandwich structures.

Comparison of Enamel Preparations - Bevel, Chamfer and Stair Step Chamfer on Fracture Resistance of Nano Filled Resin Composites Using Bulk Pack Technique - An In Vitro Study.

AIM:To evaluate and compare the effect of enamel preparation designs bevel, chamfer and stair-step chamfer on the fracture resistance of nanocomposite.METHODS:The sample group of this study consisted of 72 non-carious permanent maxillary central incisors. The sample is divided into four groups of 18 each. Group, I control Group II bevel preparation, Group III chamfer preparation, group IV stair step chamfer preparation. After the specific preparation, each tooth is filled with nanocomposite using bulk pack technique. The teeth were subjected to fracture resistance test under Universal testing machine and then were examined under a stereomicroscope to evaluate the type of bond failure. The results were subjected to statistical analysis.RESULTS:Results of the One-Way ANOVA revealed a significant difference in the mean peak failure load values of the four different groups. (P < 0.001) Tukey’s Post-Hoc comparison test revealed that there was a significant difference in the mean peak failure load values of the bevel and chamfer preparation. But there was no significant difference between chamfer and stair-step chamfer preparation designs.CONCLUSION:Stair-step chamfer preparation demonstrated comparable values to Chamfer preparation but also involved the removal of less amount of tooth structure adjacent to the fractured edge and good esthetic technique.

Quadriceps augmentation of undersized hamstrings during ACL reconstruction

BackgroundDouble hamstring autograft for anterior cruciate ligament (ACL) reconstruction is a well-established graft option; however, a major concern with this method arises when the prepared graft is too small. Resorting to allograft can be a solution to this problem, but some surgeons prefer to use autograft in particular situations and some patients may refuse allograft. We investigate the merits of using autogenous quadriceps tendons to augment the insufficient hamstrings and compare the autograft composite graft to a standard hamstrings graft of equal size. MethodsSemitendinosus, gracilis, and quadriceps tendons were harvested from 10 matched pairs of human cadaver lower extremities. Within each pair, a routine hamstring ACL graft (control) consisting of the semitendinosus and gracilis tendons, and an quadriceps augmented hamstrings graft of equal size comprised of the semitendinosus and quadriceps tendons, were prepared. A freeze-clamp mount was used to biomechanically test each graft construct. Tensile failure load, displacement, energy absorbed, and stiffness were determined and statistically compared within each pair and mode of graft failure was established. ResultsNo statistically significant differences were found between the quadriceps augmented hamstrings graft versus standard control grafts. Average values for peak failure load and graft displacement at the point of first failure were nearly identical. All ACL graft constructs failed at the mid-substance. ConclusionsThis study demonstrates no statistical difference in the biomechanical properties of an isolated hamstring ACL autograft versus a quadriceps augmented ACL autograft of equal size at time zero. Clinical relevanceThis is a potentially new and reliable method for quadriceps tendon autograft augmentation of hamstring autograft for ACL reconstruction.

The V-Shaped Distal Triceps Tendon Repair: A Comparative Biomechanical Analysis

Background: Restoring footprint anatomy, minimizing gap formation, and maximizing the strength of distal triceps tendon repairs are essential factors for a successful healing process and return to sport. Hypothesis: The novel V-shaped distal triceps tendon repair technique with unicortical button fixation closely restores footprint anatomy, provides minimal gap formation and high ultimate failure load, and minimizes iatrogenic fracture risk in acute/subacute distal triceps tendon tears. Study Design: Controlled laboratory study. Methods: Twenty-four cadaveric elbows (mean ± SD age, 66 ± 5 years) were randomly assigned to 1 of 3 repair groups: the transosseous cruciate repair technique (gold standard), the knotless suture-bridge repair technique, and the V-shaped distal triceps tendon repair technique. Anatomic measurements of the central triceps tendon footprint were obtained in all specimens with a 3-dimensional digitizer before and after the repair. Cyclic loading was performed for a total of 1500 cycles at a rate of 0.25 Hz, pulling in the direction of the triceps. Displacements were measured on the medial and lateral tendon sites with 2 differential variable reluctance transducers. Load to failure and construct failure mode were recorded. Results: The mean triceps bony insertion area was 399.05 ± 81.23 mm2. The transosseous cruciate repair technique restored 36.6% ± 16.8% of the native tendon insertion area, which was significantly different when compared with the knotless suture-bridge repair technique (85.2% ± 14.8%, P = .001) and the V-shaped distal triceps tendon repair technique (88.9% ± 14.8%, P = .002). Mean displacement showed no significant difference between the V-shaped distal triceps tendon repair technique (medial side, 0.75 ± 0.56 mm; lateral side, 0.99 ± 0.59 mm) and the knotless suture-bridge repair technique (1.61 ± 0.97 mm and 1.29 ± 0.8 mm) but significance between the V-shaped distal triceps tendon repair technique and the transosseous cruciate repair technique (4.91 ± 1.12 mm and 5.78 ± 0.9 mm, P < .001). Mean peak failure load of the V-shaped distal triceps tendon repair technique (732.1 ± 156.0 N) was significantly higher than that of the knotless suture-bridge repair technique (505.4 ± 173.9 N, P = .011) and the transosseous cruciate repair technique (281.1 ± 74.8 N, P < .001). Mechanism of failure differed among the 3 repairs, with the only olecranon fracture occurring in the knotless suture-bridge repair technique at the level of the lateral row suture anchors. Conclusion: At time zero, the V-shaped distal triceps tendon repair technique and the knotless suture-bridge repair technique both provided anatomic footprint coverage. Ultimate load to failure was highest for the V-shaped distal triceps tendon repair technique, while gap formation was different only in comparison with the transosseous cruciate repair technique. Clinical Relevance: The V-shaped distal triceps tendon repair technique provides an alternative procedure to other established repairs for acute/subacute distal triceps tendon ruptures. The reduced repair site motion of the V-shaped distal triceps tendon repair technique and the knotless suture-bridge repair technique at the time of surgery may allow a more aggressive rehabilitation program in the early postoperative period.

Mechanical properties of joints in 5052 aluminum made with adhesive bonding and mechanical fasteners

In this work, the mechanical properties of joints made with a ridged tack only, one-part heat-curing epoxy only, and a combination of the two were evaluated. All samples were constructed using 1.6 mm thick 5052 aluminum. Testing was performed in lap shear, cross tension, and at 45°. A set of tests was also performed to investigate the mechanical strength of joints in lap shear under various surface preparation methods.It was found that the peak failure load was governed solely by the adhesive in hybrid joints. The performance gain from the inclusion of the ridged tack was greater energy absorption. The absorbed energy for a hybrid joint in lap shear configuration is closely approximated by the sum of energy absorbed with adhesive only and ridged tack only. The effect was much less pronounced for samples in cross tension and at 45°. Additionally, the adhesive strength was found to be completely unaffected by the surface preparation of the samples.

A Biomechanical Comparison of Fifth Metatarsal Jones Fracture Fixation Methods

Background: Fifth metatarsal base fractures of the metaphyseal-diaphyseal watershed junction (Jones fracture) are commonly treated with surgical fixation in athletes. Intramedullary screw fixation remains the most utilized construct, although plantar-lateral plating is an alternative. Purpose/Hypothesis: The purpose was to compare the mechanical strength of fracture fixation between an intramedullary screw and plantar-lateral plating. The hypothesis was that plantar-lateral plate fixation would allow for more cycles and higher peak loads before failure, as well as less fracture gapping, than would an intramedullary screw in cadaveric foot specimens with simulated Jones fractures exposed to cantilever bending. Study Design: Controlled laboratory study. Methods: Twelve pairs of male cadaver feet were separated into 2 groups (plate or screw) to conduct contralateral comparative testing of 2 devices with equally numbered right and left feet. For each fifth metatarsal, an osteotomy with a microsagittal saw was created to simulate a Jones fracture. The plate group underwent fixation with a 3.0-mm 4-hole low-profile titanium plate placed plantar-laterally with 3 locking screws and 1 nonlocking screw. The screw group underwent fixation with a 40- or 45-mm × 5.5-mm partially threaded solid titanium intramedullary screw. After fixation, the metatarsals were excised for biomechanical testing. Cyclic cantilever failure testing was conducted with a gradient-cycle method. Sinusoidal loading forces were applied, increasing by 5.0-pound-force increments per 10 cycles, until each specimen experienced mechanical failure of implant or bone. Failure mode, number of cycles to failure, peak failure load, gap width at the last mutual prefailure loading, and video data were recorded. Paired 2-tailed t test (α = 0.05) was used to compare groups (P < .05 set for significance). Results: Failure mode in both groups occurred predominantly at the bone-implant interface. Plate fixation resulted in significantly higher mean ± SD values for cycles to failure (63.9 ± 27.0 vs 37.3 ± 36.9, P = .01) and peak failure load (159.2 ± 60.5 N vs 96.5 ± 45.8 N, P = .01), with a significantly lower mean gap width (0.0 ± 0.0 mm vs 3.2 ± 2.4 mm, P < .01). Conclusion: As compared with intramedullary screw fixation, plantar-lateral plating allowed for greater cycles to failure and peak load before failure, as well as less gap width, when applied to cadaver foot specimens with simulated Jones fractures exposed to cantilever bending in a load frame. Clinical Relevance: Early return to play among athletes before Jones fracture union is associated with increased risk of failure. This study introduces a plantar-lateral plating construct that performed more favorably than intramedullary screw fixation when applied to simulated Jones fractures in cadaveric foot specimens. Further clinical comparative studies are needed to assess the clinical use of this construct.

Comparison between two post-dentin bond strength measurement methods

The push-out (PO) test and the diametral compression (DC) test were performed to compare the merits of two post-dentin bond strength measurement methods. Compared with the push-out test, the disk in DC provided post-dentin bond strength measurements that were more precise. The load-displacement curves from the DC test were much smoother and more linear up to the point of fracture when compared to those from the PO test. Compared to the PO test, DC is easier to perform for determining the bond strength between posts and dentin. No specimen alignment is needed in the DC test, and it produces a smaller standard deviation in the measured bond strength. The main disadvantage of the DC test, however, is that finite element analysis (FEA) is required to calculate the bond strength. The shear bond strength given by the PO test based on the simple formula is not valid, though, and the peak failure load is dependent on friction at the post-dentin interface.

Comparative Evaluation of the Fracture Resistance of Two Different Fiber-reinforced Composite Restorations with Particulate Filler Composite Restorations.

Uncomplicated crown fractures are the most common form of traumatic dental injuries (TDIs) in children affecting their personal and social well-being.AimTo evaluate the fracture resistance of fractured incisors restored with particulate filler composites, glass fiber-reinforced composites, and Polyethylene fiber-reinforced composite restorations.Materials and methodsStandardized incisal and mesio-incisal fractures with chamfer preparation were prepared on human maxillary central incisors. Test samples were restored using particulate filler composites (Filtek Z 250), glass fiber-reinforced composites (Fiber-Splint) and polyethylene-reinforced composites (Ribbond). Static load was applied to the test samples using Universal testing machine at a cross-head speed of 1 mm/min. Data were tabulated and analyzed using analysis of variance (ANOVA) (p = 0.05).ResultsDescriptive statistics of mean [standard deviation (SD)] peak failure load in incisal restorations for particular filler composite, glass fiber-reinforced composites, and polyethylene fiber-reinforced composites were 196.00 (± 67.46), 186.28 (± 66.44), and 246.71 (± 24.52) respectively, whereas for mesio-incisal restorations, mean (SD) peak failure loads were 169.28 (± 33.53), 218.57 (± 74.41), and 225.71 (± 57.52) respectively.ConclusionPolyethylene-reinforced composites showed an improved load-bearing capacity in incisal and mesio-incisal restorations when compared with particulate filler composites and glass fiber-reinforced composites.How to cite this article: Patnana AK, Rao VVN, Chandrabhatla SK, Rajasekhar VR. Comparative Evaluation of the Fracture Resistance of Two Different Fiber-reinforced Composite Restorations with Particulate Filler Composite Restorations. Int J Clin Pediatr Dent 2018;11(4):277-282.

Biomechanical Comparison of Transosseous Knotless Rotator Cuff Repair Versus Transosseous Equivalent Repair: Half The Anchors With Equivalent Biomechanics?

To compare the biomechanics of a transosseous equivalent (TOE) repair using medial and lateral anchors with tape to a transosseous knotless (TOK) tape repair with only laterally placed intraosseous anchors. One of 2 different repairs were performed on 8 paired specimens: (1) transosseous equivalent (TOE) tape repair or (2) transosseous knotless (TOK) tape repair. Specimens were mounted on a materials testing machine and loaded in uniaxial tension to measure cyclic construct gap formation, followed by failure testing. Paired t tests were used to compare gapping, ultimate stiffness, and failure loads. Fisher exact test was used to compare modes of failure (soft tissue failure vs construct failure). Peak cyclic gapping, failure stiffness, and ultimate failure loads did not differ between TOE and TOK repairs (P= .140 for gapping, P= .106 for stiffness, and P= .672 for peak failure loads). All TOK repairs failed via soft tissue failure medial to the medial suture line, with no construct failures. TOE repairs failed more often through construct failure (anchor migration or suture-bone interface cut through) than TOK repairs (P= .026). TOK repairs only failed through soft tissue whereas TOE repairs failed through both soft tissue and the repair construct. Despite 50% fewer suture anchors in the TOK repairs than the TOE repairs, cyclic gapping and ultimate stiffness and failure loads were not significantly different. The transosseous knotless construct presented is a 2-anchor construct that is equivalent in biomechanical function to a traditional 4-anchor construct, reducing anchor load in the tuberosity.

A Biomechanical Comparison of Fifth Metatarsal Jones Fracture Fixation Methods - What is the Ideal Construct?

Intramedullary screw fixation techniques remain as the most utilized construct for the treatment of Jones’ fractures despite reports of non-union and re-fracture. The authors are not aware of any other biomechanical studies comparing this plate construct to an intramedullary screw construct. Fifth metatarsal base fractures of the metaphyseal-diaphyseal watershed junction (Jones fractures) are commonly treated with surgical fixation in athletes. Intramedullary screw fixation remains the most utilized construct despite reports of non-union and refractures. This paper compares the biomechanical strength of an intramedullary screw with a plantar-lateral plating construct applied to simulated Jones fractures in paired cadaver foot specimens. Twelve pairs of male cadaver feet (mean age 58) were separated into 2 groups (plate or screw) to conduct contralateral comparative testing of two devices with equally numbered right and left feet in each group. For each fifth metatarsal, an osteotomy was created 2.5cm distal to the proximal tuberosity aimed for the articulation between the fourth and fifth metatarsals to simulate a Jones fracture. The plate group underwent fixation with a 3.0mm 4-hole low profile titanium locking plate placed plantar-laterally. The screw group underwent fixation with a 40 or 45mm X 5.5mm partially-threaded solid titanium intramedullary screw. The osteotomy and fixation were performed leaving all ligamentous and tendinous attachments in place to simulate a surgical procedure. After fixation, the metatarsals were excised for biomechanical testing. Cyclic cantilever failure testing was conducted using a gradient-fatigue method (force applied at gradually increasing peak-loads). Sinusoidal loading forces at a constant frequency of 0.25Hz were applied to the metatarsal increasing by 2.5 pound-force (lbf) increments per 10 cycles. Testing was concluded once each specimen had completed the prescribed cycles or experienced mechanical failure of the implant or bone. Failure mode, number of cycles to failure (CTF), peak-failure load (PFL), gap width (GW), and video data were recorded. The T-test was used to compare the two groups with a P<.05 set for clinical significance. The failure mode in both groups occurred at the bone-implant interface. No significant difference was found between the plate and screw groups with regard to CTF (21.5 vs 21 P=0.49), PFL (18.5 lbf vs 9 lbf, P=0.33), or GW (1.2mm vs 5.7mm, P=0.13) respectively reported as means. This biomechanical investigation suggests planter-lateral plating is a viable option for management of Jones fractures. Although not statistically significant, larger PFL and smaller GW were recognized in the plate group compared to the screw group. This may hold clinical importance in both primary and revision Jones fracture treatments. The authors are unaware of any prior biomechanical studies comparing plantar-lateral plating and screw fixation for the treatment Jones fractures. Intramedullary screw fixation techniques remain as the most utilized construct for the treatment of Jones’ fractures despite reports of non-union and re-fracture. The authors are not aware of any other biomechanical studies comparing this plate construct to an intramedullary screw construct.

Pectoralis Major Repair: A Biomechanical Analysis of Modern Repair Configurations Versus Traditional Repair Configuration

Background: Pectoralis major (PM) ruptures are increasingly common, and a variety of surgical techniques have been described. However, tested techniques have demonstrated diminished strength with inadequate restoration of the footprint and suture failure at relatively low loads. Purpose/Hypothesis: The purpose was to biomechanically compare PM transosseous suture repair (current gold standard) to modern PM repair techniques that use larger caliber sutures, suture tape, and unicortical button fixation (UBF). The null hypothesis was that there would be no mechanical difference between repair techniques and no difference in the amount of footprint restoration. Study Design: Controlled laboratory study. Methods: Twenty-four fresh-frozen cadaveric shoulders controlled for age and bone mineral density were randomized equally to 4 groups: (1) UBF, suture tape; (2) UBF, No. 5 suture, suture tape; (3) bone trough with No. 2 suture; and (4) native PM tendon group; all groups were tested to failure. The specimens were tested under cycling loads (10 N to 125 N) with a final load-to-failure test at 1 mm/s. Failure modes were classified by location and cause of rupture based on optical markers, while tendon footprint length was measured to determine amount of footprint restoration. Results: For fixation strength, the mean peak load was significantly greater in the native tendon (1816 ± 706 N) versus UBF/No. 5 suture/suture tape (794 ± 168 N), UBF/suture tape (502 ± 201 N), and bone trough (492 ± 151 N) (P < .001 for all). UBF/No. 5 suture/suture tape featured the lowest displacement superiorly (1.09 ± 0.47 mm) and inferiorly (1.14 ± 0.39 mm) with a significant difference compared with bone trough. With regard to tendon footprint reapproximation, cortical button fixation best approximated native tendon footprint length versus bone trough. Conclusion: Based on peak failure load, the UBF/No. 5 suture/suture tape construct demonstrated 61% greater construct strength than a traditional bone trough technique. Moreover, displacement after cyclic loading was by far smallest in the UBF/No. 5 suture/suture tape construct. Therefore, repair constructs with larger caliber suture and suture tape provide a measurable improvement in construct strength versus traditional PM repair techniques in a biomechanical model and may be advantageous for repair. Clinical Relevance: Cortical button fixation with larger caliber suture and suture tape allows for a significantly better PM repair than more traditional techniques at the time of surgery, which may ultimately result in improved clinical outcomes if implemented in surgical practice.

Fracture resistance of class IV fiber-reinforced composite resin restorations: An in vitro study

Objectives: The aim of this study was to evaluate fracture resistance of incisal edge fractures (Class IV) restored with a Glass Fiber-reinforced Composite (FRC). Materials and Methods: Twenty-four extracted sound maxillary central incisors were randomly divided into two groups. Group I (control) contained untreated teeth. Samples in experimental groups II were prepared by cutting the incisal (one-third) part of the crown horizontally and was subjected to enamel preparations, then restored with a Glass FRC. Fracture resistance was evaluated as Newton's for samples tested in a Hounsfield universal testing machine. Failure modes were examined microscopically. Results: Mean peak failure load (Newton's) observed in Glass Fiber-reinforced Nanocomposite was 863.50 ± 76.12. The experimental group showed similar types of failure modes with the majority occurring as cohesive and mixed type. 58% of the teeth in Glass FRC group fractured below the cementoenamel junction. Conclusion: Using Fiber reinforced composite substructure under conventional composites in Class IV restorations, the fracture resistance of the restored incisal edge could be increased.