In Vitro Fracture Testing of Submicron Diameter Collagen Fibril Specimens

Mechanical testing of collagenous tissues at different length scales will provide improved understanding of the mechanical behavior of structures such as skin, tendon, and bone, and also guide the development of multiscale mechanical models. Using a microelectromechanical-systems (MEMS) platform, stress-strain response curves up to failure of type I collagen fibril specimens isolated from the dermis of sea cucumbers were obtained in vitro. A majority of the fibril specimens showed brittle fracture. Some displayed linear behavior up to failure, while others displayed some nonlinearity. The fibril specimens showed an elastic modulus of 470 ± 410 MPa, a fracture strength of 230 ± 160 MPa, and a fracture strain of 80% ± 44%. The fibril specimens displayed significantly lower elastic modulus in vitro than previously measured in air. Fracture strength/strain obtained in vitro and in air are both significantly larger than those obtained in vacuo, indicating that the difference arises from the lack of intrafibrillar water molecules produced by vacuum drying. Furthermore, fracture strength/strain of fibril specimens were different from those reported for collagenous tissues of higher hierarchical levels, indicating the importance of obtaining these properties at the fibrillar level for multiscale modeling.     

Preparation and properties of carboxylated styrene-butadiene rubber/cellulose nanocrystals composites

A series of carboxylated styrene-butadiene rubber (XSBR)/cellulose nanocrystals (CNs) latex composites were successfully prepared. The vulcanization process, morphology, dynamic viscoelastic behavior, dynamic mechanical property, thermal and mechanical performance of the XSBR/CNs composites were investigated in detail. The results revealed that CNs were dispersed uniformly in the XSBR matrix and formed a strong filler–filler network. The dynamic mechanical analysis (DMA) showed that the glass transition temperature (T_g) of XSBR matrix was shifted from 48.45 to 50.64 °C with 3 phr CNs, but decreased from 50.64 to 46.28 °C when further increasing CNs content up to 15 phr. The composites exhibited a significant enhancement in tensile strength (from 16.9 to 24.1 MPa) and tear strength (from 43.5 to 65.2 MPa) with loading CNs from 0 to 15 phr. In addition, the thermo-gravimetric analysis (TGA) showed that the temperature at 5% weight loss of the XSBR/CNs composites decreased slightly with an increase of the CNs content.     

Development of films based on blends of Amaranthus cruentus flour and poly(vinyl alcohol)

The aim of this work was to develop biodegradable films based on blends of Amaranthus cruentus flour and poly(vinyl alcohol). Five different PVA types were tested. Blends with higher hydrolysis (HD) degree PVA were more resistant, showing greater tensile strength (TS) and puncture force (PF). However, the films with PVA with lower HD showed more flexibility, greater elongation at break (ELO) and greater puncture deformation (PD), with the exception of PVA 325. The latter was chosen due to it superior mechanical performance (TS = 10.2 MPa, ELO = 89.8%, PF = 9.4 N and PD = 16.3%). When films based on blends of amaranth flour and PVA 325 (10–50%) were evaluated, all mechanical properties were enhanced with increase in PVA 325 content. The solubility in water of the films made with PVA and amaranth flour decreased with increasing PVA content, reaching 44% of soluble matter for the 50% PVA film. The formation of hydrogen bonds between the blend components was confirmed by the FTIR spectra analysis.     

Mechanical properties of mineralized collagen fibrils as influenced by demineralization

Dentin and bone derive their mechanical properties from a complex arrangement of collagen type-I fibrils reinforced with nanocrystalline apatite mineral in extra- and intrafibrillar compartments. While mechanical properties have been determined for the bulk of the mineralized tissue, information on the mechanics of the individual fibril is limited. Here, atomic force microscopy was used on individual collagen fibrils to study structural and mechanical changes during acid etching. The characteristic 67 nm periodicity of gap zones was not observed on the mineralized fibril, but became apparent and increasingly pronounced with continuous demineralization. AFM-nanoindentation showed a decrease in modulus from 1.5 GPa to 50 MPa during acid etching of individual collagen fibrils and revealed that the modulus profile followed the axial periodicity. The nanomechanical data, Raman spectroscopy and SAXS support the hypothesis that intrafibrillar mineral etches at a substantially slower rate than the extrafibrillar mineral. These findings are relevant for understanding the biomechanics and design principles of calcified tissues derived from collagen matrices.     

The effect of citric acid on the structural properties and cytotoxicity of the polyvinyl alcohol/starch films when molding at high temperature

A series of starch/polyvinyl alcohol (PVA) films, denoted SP films, with varying concentrations (5–30 wt%) of citric acid (CA) were solvent cast at 140 °C. The effects of CA on the chemical structure, thermal properties, swelling degree, mechanical properties, crystallinity, and cytotoxicity were investigated. Fourier-transform infrared (FT-IR) spectroscopy showed that an esterification took place between CA and starch (or PVA) during molding at 140 °C. This esterification and the multi-carboxyl structure of CA resulted in a chemical cross-linking of the blended system. Furthermore, the esterification occurred more easily between starch and CA as opposed to between the PVA and CA. The residual-free CA acted as a plasticizer for the starch and PVA. As compared to the hydroxyl groups on glycerol, the carboxyl groups on CA were capable of forming stronger hydrogen bonds between CA and other components, and this cross-linking and strong hydrogen bonding enhanced the thermal stability of the SP films. Consequently, the water absorbance decreased from 33% to 20% as the CA percentage increased from 5 to 30 wt%. When 5 wt% CA was added, the tensile strength of the sample increased from 39 to 48 MPa, but when even more CA was added (from 5 to 30 wt%), the tensile strength decreased from 48 to 42 MPa and the elongation at break increased from 102% to 208%. This was caused by the plasticizing effect of the residual-free CA in the blend. The cell relative growth rates of samples with varying CA concentrations exceeded 80% after 7 days of incubation, and this demonstrated that there was no significant toxicity on the cells’ growth when the CA content was less than 20 wt%.     

Mechanical properties of cranial sutures

Many bones in mammalian skulls are linked together by cranial sutures, connective tissue joints that are morphologically variable and show different levels of interdigitation among and within species. The goal of this investigation was to determine whether sections of skull with cranial sutures have different mechanical properties than adjacent sections without sutures, and if these properties are enhanced with increased interdigitation. To test these hypotheses, bending strength and impact energy absorption were measured for samples of goat (Capra hircus) cranial bone without sutures and with sutures of different degrees of interdigitation. Bending strength was measured under both dynamic (9.7 mm displacement s-1) and relatively static (0.8 mm s-1) conditions, and at either speed, increased sutural interdigitation provided increased strength during three-point bending. However, except for very highly interdigitated sutures loaded slowly, sutures were not as strong in bending as bone. In contrast, sutures absorbed from 16% to 100% more energy per unit volume during impact loading than did bone. This five-fold increase in energy absorption by the sutures was significantly correlated with increased sutural interdigitation.     

Chitosan–caffeic acid–genipin films presenting enhanced antioxidant activity and stability in acidic media

The use of chitosan films has been limited due to their high degradability in aqueous acidic media. In order to produce chitosan films with high antioxidant activity and insoluble in acid solutions caffeic acid was grafted to chitosan by a radical mechanism using ammonium cerium (IV) nitrate (60 mM). Genipin was used as cross-linker. This methodology originated films with 80% higher antioxidant activity than the pristine film. Also, these films only lost 11% of their mass upon seven days immersion into an aqueous solution at pH 3.5 under stirring. The films surface wettability (contact angle 105°), mechanical properties (68 MPa of tensile strength and 4% of elongation at break), and thermal stability for temperatures lower than 300 °C were not significantly influenced by the covalent linkage of caffeic acid and genipin to chitosan. Due to their characteristics, mainly higher antioxidant activity and lower solubility, these are promising materials to be used as active films.     

Viscoelastic properties of isolated collagen fibrils

Understanding the viscoelastic behavior of collagenous tissues with complex hierarchical structures requires knowledge of the properties at each structural level. Whole tissues have been studied extensively, but less is known about the mechanical behavior at the submicron, fibrillar level. Using a microelectromechanical systems platform, in vitro coupled creep and stress relaxation tests were performed on collagen fibrils isolated from the sea cucumber dermis. Stress-strain-time data indicate that isolated fibrils exhibit viscoelastic behavior that could be fitted using the Maxwell-Weichert model. The fibrils showed an elastic modulus of 123 ± 46 MPa. The time-dependent behavior was well fit using the two-time-constant Maxwell-Weichert model with a fast time response of 7 ± 2 s and a slow time response of 102 ± 5 s. The fibrillar relaxation time was smaller than literature values for tissue-level relaxation time, suggesting that tissue relaxation is dominated by noncollagenous components (e.g., proteoglycans). Each specimen was tested three times, and the only statistically significant difference found was that the elastic modulus is larger in the first test than in the subsequent two tests, indicating that viscous properties of collagen fibrils are not sensitive to the history of previous tests.     

A Chitosan Based,Laser Activated Thin Film Surgical Adhesive, 'SurgiLux': Preparation and Demonstration

Sutures are a 4,000 year old technology that remain the ''gold-standard'' for wound closure by virtue of their repair strength (~100 KPa). However, sutures can act as a nidus for infection and in many procedures are unable to effect wound repair or interfere with functional tissue regeneration.¹ Surgical glues and adhesives, such as those based on fibrin and cyanoacrylates, have been developed as alternatives to sutures for the repair of such wounds. However, current commercial adhesives also have significant disadvantages, ranging from viral and prion transfer and a lack of repair strength as with the fibrin glues, to tissue toxicity and a lack of biocompatibility for the cyanoacrylate based adhesives. Furthermore, currently available surgical adhesives tend to be gel-based and can have extended curing times which limit their application.² Similarly, the use of UV lasers to facilitate cross-linking mechanisms in protein-based or albumin ''solders'' can lead to DNA damage while laser tissue welding (LTW) predisposes thermal damage to tissues.³ Despite their disadvantages, adhesives and LTW have captured approximately 30% of the wound closure market reported to be in excess of US $5 billion per annum, a significant testament to the need for sutureless technology.⁴In the pursuit of sutureless technology we have utilized chitosan as a biomaterial for the development of a flexible, thin film, laser-activated surgical adhesive termed ''SurgiLux''. This novel bioadhesive uses a unique combination of biomaterials and photonics that are FDA approved and successfully used in a variety of biomedical applications and products. SurgiLux overcomes all the disadvantages associated with sutures and current surgical adhesives (see Table 1).In this presentation we report the relatively simple protocol for the fabrication of SurgiLux and demonstrate its laser activation and tissue weld strength. SurgiLux films adhere to collagenous tissue without chemical modification such as cross-linking and through irradiation using a comparatively low-powered (120 mW) infrared laser instead of UV light. Chitosan films have a natural but weak adhesive attraction to collagen (~3 KPa), laser activation of the chitosan based SurgiLux films emphasizes the strength of this adhesion through polymer chain interactions as a consequence of transient thermal expansion.⁵ Without this ''activation'' process, SurgiLux films are readily removed.^6-9 SurgiLux has been tested both in vitro and in vivo on a variety of tissues including nerve, intestine, dura mater and cornea. In all cases it demonstrated good biocompatibility and negligible thermal damage as a consequence of irradiation.^6-10     

Thermal, Mechanical and Microstructures Properties of Cellulose Derivatives Films: A Comparative Study

The proposal in this study was to evaluate the physical properties of different biopolymers films. The materials used were: pectin, carboxyl methylcellulose, methylcellulose, hydroxyl propylcellulose, hydroxypropyl-methylcellulose, and corn waxy starch; from these polysaccharides aqueous dispersions were prepared to 3% (w/v) for obtained films. In these biopolymer films, the thermal diffusivities (α) was evaluated by the Open Photoacoustic Cell method; also, their mechanical properties as tensile strength, elongation, and Young’s modulus were measured, their crystallinity percentage was evaluated by X-ray diffraction and microstructure through atomic force microscopy in contact mode. From the polysaccharide films, it was observed that most of them were flexible and transparent. In the case of the films, mechanical properties were found that the highest value of tensile strength and Young’s modulus corresponded to carboxyl methylcellulose with 69.17 and 1,912.20 MPa values, respectively. Also, Open Photoacoustic Cell method and X-ray diffraction measurements showed that there exist a correlation between the thermal diffusivity values and the crystallinity measured in the biopolymer films. It was also observed that α values of cellulose derived was affected by the substitution group in the molecule, reaching the highest α value, the films of carboxyl methylcellulose. Regarding the microstructural of the films, starch showed the highest roughness value (88.6 nm) whereas hydroxypropyl-methylcellulose resulted with the lowest roughness value (7.67 nm).     

Bacterial attachment to stainless steel welds: Significance of substratum microstructure

AISI Type 304 L stainless steel (SS) is a widely used material in industry due to its strength and resistance to corrosion. However, corrosion on SS is reported largely at welds or adjacent areas. Bacteria were observed to colonize preferentially near welds as a result of surface roughness. In the present study, the influence of another important metal surface condition on bacterial adhesion has been evaluated, i.e. substratum microstructure. Type 304 L SS weld samples were prepared and machined to separate weld metal, the heat affected zone (HAZ) and base metal regions. The coupons were molded in resin so that only the surfaces polished to a 3 p.m finish were exposed to the experimental medium with Pseudomonas sp. isolated from a corrosive environment in Japan. The coupons were exposed for varying durations. The area of bacterial attachment showed significant differences with time of exposure and; the type of coupons. Generally, the weld metal samples showed more attachment whilst the base metal showed the least. The area of attachment was inversely proportional to the average grain size of the three samples. As the bacteria started colonizing, attachment mainly occurred on the grain boundaries of the base metal (after 8h, 84.62% and 15.38% of the total number of bacteria attached in the field of view (FOV) at the grain boundary and matrix, respectively) and on the austenite‐ferrite interface in the weld metal (after 8h, 88.33% and 11.77% of the total number of bacteria attached in the FOV at the boundary and matrix, respectively). The weld area had more grains and hence more grain boundary/ unit area than the base metal, resulting in more bacterial attachment. SEM observations showed this increased attachment of Pseudomonas sp. resulted in the initiation of microbiologically influenced corrosion (MIC) on the weld coupons by 16 d. Therefore, the results provide data to support the fact that substratum microstructure influences bacterial attachment, which in turn leads to corrosion.     

Novel CaO/polylactic acid nanoscaffold as dental resin nanocomposites and the investigation of physicochemical properties

In this study, for the first time, calcium oxide (CaO)/polylactic acid nanoscaffolds were synthesized by co‐precipitation assistant reverse micelles method. The physical and chemical (physicochemical) properties of the structures as dental resin composites were also studied. Nanocomposite materials as primary and basic dental compounds can be conveniently applied as dental filling materials with a high esthetic quality. In this research nanoscaffolds act as a bed for nanoparticles and improve the mechanical and chemical (mechanochemical) properties, CaO nanoparticles were loading in polylactic acid nanoscaffold as a bioactivity polymer for usage in the dental resin composites. Mechanical properties of the dental resin composite containing CaO/polylactic acid nanoscaffold were calculated: the flexural strength (137.2 MPa), modulus (12.9GPa) and compressive strength (344.2 MPa). Potential of the basic nanoparticle and the products were characterized by X‐ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), thermogravimetric analysis (TGA), dynamic light scattering (DLS), ultraviolet‐visible spectroscopy (UV‐visible) and atomic force microscopy (AFM) showed the size of the optimized nanostructures was about 85 to 120 nm. According to TGA results of polylactic acid nanofibers with thermal stability below 300°C these high thermal stability materials can be used as dental resin composites.     

香椿木材解剖构造及其物理力学性质

为扩大和培育香椿资源和填补国内经济建设及人民生活对优质木材的需求,为其开发和利用提供一定的基础数据及科学的理论指导,依照GB1927-91实验方法对其木材的解剖和物理力学性质做了系统研究。结果表明：香椿纤维13年生后形态均匀,长宽比46.18,双壁厚11.00μm,纤维壁腔比0.56,腔径比0.76;导管分子平均长度383.52μm,宽度143.98μm;基本密度和气干密度分别为0.415g/cm3和0.475g/cm3,属“轻”型;差异干缩为1.93;木材的抗弯强度、抗弯弹性模量和顺纹抗压强度分别为67.85MPa、6179.82MPa和38.23MPa,综合强度106.08MPa,均属“低”级,香椿的综合品质系数为2556.1×105 Pa,为高等级材。综合分析表明香椿材质优良。     

Effect of temperature on welding of metallic nanowires investigated using molecular dynamics simulations

The mechanism of welding of Au–Au, Ag–Ag and Au–Ag nanowires (NWs) with head-to-head contact is studied using molecular dynamics simulations based on the second-moment approximation of the many-body tight-binding potential. The effect of temperature in the range of 300–900 K is investigated. Simulation results show that at the initial welding, an incomplete jointing area forms through the interactions of the van der Waals attractive force, and that the jointing area increases with increasing the extent of contact between the two NWs during the welding process and temperature. Few defects form along the (1 1 1) close-packed plane during the welding process because the acting stress is quite low. Among the three NW pairs, the Au–Au NWs have the best cold-welding quality, whereas the Au–Ag NWs have the worst cold-welding quality due to the welding of different materials. With an increase in temperature, the weld stress and the mechanical strength of the NWs significantly decrease, and the number of disordered structures increases. The welding fails when the temperature exceeds the molten temperature of the NWs.     

Systematic review and meta-analysis of the biomechanical properties of the human dura mater applicable in computational human head models

Accurate biomechanical properties of the human dura mater are required for computational models and to fabricate artificial substitutes for transplantation and surgical training purposes. Here, a systematic literature review was performed to summarize the biomechanical properties of the human dura mater that are reported in the literature. Furthermore, anthropometric data, information regarding the mechanically tested samples, and specifications with respect to the used mechanical testing setup were extracted. A meta-analysis was performed to obtain the pooled mean estimate for the elastic modulus, ultimate tensile strength, and strain at maximum force. A total of 17 studies were deemed eligible, which focused on human cranial and spinal dura mater in 13 and 4 cases, respectively. Pooled mean estimates for the elastic modulus (n?=?448), the ultimate tensile strength (n?=?448), and the strain at maximum force (n?=?431) of 68.1 MPa, 7.3 MPa and 14.4% were observed for native cranial dura mater. Gaps in the literature related to the extracted data were identified and future directions for mechanical characterizations of human dura mater were formulated. The main conclusion is that the most commonly used elastic modulus value of 31.5 MPa for the simulation of the human cranial dura mater in computational head models is likely an underestimation and an oversimplification given the morphological diversity of the tissue in different brain regions. Based on the here provided meta-analysis, a stiffer linear elastic modulus of 68 MPa was observed instead. However, further experimental data are essential to confirm its validity.

     

Mechanical Properties of the Compass Depressors of the Sea-Urchin Paracentrotus lividus (Echinodermata,Echinoidea) and the Effects of Enzymes,Neurotransmitters and Synthetic Tensilin-Like Protein

The compass depressors (CDs) of the sea-urchin lantern are ligaments consisting mainly of discontinuous collagen fibrils associated with a small population of myocytes. They are mutable collagenous structures, which can change their mechanical properties rapidly and reversibly under nervous control. The aims of this investigation were to characterise the baseline (i.e. unmanipulated) static mechanical properties of the CDs of Paracentrotus lividus by means of creep tests and incremental force-extension tests, and to determine the effects on their mechanical behaviour of a range of agents. Under constant load the CDs exhibited a three-phase creep curve, the mean coefficient of viscosity being 561±365 MPa.s. The stress-strain curve showed toe, linear and yield regions; the mean strain at the toe-linear inflection was 0.86±0.61; the mean Young’s modulus was 18.62±10.30 MPa; and the mean tensile strength was 8.14±5.73 MPa. Hyaluronidase from Streptomyces hyalurolyticus had no effect on creep behaviour, whilst chondroitinase ABC prolonged primary creep but had no effect on secondary creep or on any force-extension parameters; it thus appears that neither hyaluronic acid nor sulphated glycosaminoglycans have an interfibrillar load transfer function in the CD. Acetylcholine, the muscarinic agonists arecoline and methacholine, and the nicotinic agonists nicotine and 1-[1-(3,4-dimethyl-phenyl)-ethyl]-piperazine produced an abrupt increase in CD viscosity; the CDs were not differentially sensitive to muscarinic or nicotinic agonists. CDs showed either no, or no consistent, response to adrenaline, L-glutamic acid, 5-hydroxytryptamine and γ-aminobutyric acid. Synthetic echinoid tensilin-like protein had a weak and inconsistent stiffening effect, indicating that, in contrast to holothurian tensilins, the echinoid molecule may not be involved in the regulation of collagenous tissue tensility. We compare in detail the mechanical behaviour of the CD with that of mammalian tendon and highlight its potential as a model system for investigating poorly understood aspects of the ontogeny and phylogeny of vertebrate collagenous tissues.     

Effects of <Superscript>60</Superscript>Co gamma radiation dose on initial structural biomechanical properties of ovine bone—patellar tendon—bone allografts

Gamma radiation is established as a procedure for inactivating bacteria, fungal spores and viruses. Sterilization of soft tissue allografts with high dose ⁶⁰Co gamma radiation has been shown to have adverse effects on allograft biomechanical properties. In the current study, bone-patellar tendon-bone (BPTB) allografts from 32 mature sheep were divided into two treatment groups: low-dose radiation at 15 kGy (n = 16) and high-dose radiation at 25 kGy (n = 16) with the contralateral limb serving as a 0 kGy (n = 32) non-irradiated control. Half of the tendons from all treatment groups were biomechanically tested to determine bulk BPTB mechanical properties, cancellous bone compressive properties, and interference screw pull-out strength. The remaining tissues were prepared, implanted, and mechanically tested in an acute in vitro anterior crucial ligament (ACL) reconstruction. Low-dose radiation did not adversely affect mechanical properties of the tendon allograft, bone, or ACL reconstruction compared to internal non-irradiated control. However, high-dose radiation compromised bulk tendon load at failure and ultimate strength by 26.9 and 28.9%, respectively (P < 0.05), but demonstrated no negative effect on the cancellous bone compressive properties or interference screw pull-out strength. Our findings suggest that low dose radiation (15 kGy) does not compromise the mechanical integrity of the allograft tissue, yet high dose radiation (25 kGy) significantly alters the biomechanical integrity of the soft tissue constituent.     

Laser tissue welding analyzed using fluorescence,Stokes shift spectroscopy,and Huang‐Rhys parameter

Near infrared (NIR) continuous wave laser radiation at the 1,450 nm wavelength was used to weld porcine aorta and skin samples via the absorption of combitional vibrational modes of native water in the tissues. The fluorescence spectra were measured from the key native molecules of welded and non‐welded tissues at specific excitation and emission wavelengths from collagen, elastin, and tryptophan. The changes in the fluorescence intensities and differences in Stokes shift (Δν_ss) of key native fluorophores were measured to differentiate the Huang‐Rhys parameter values (S) of the chromophores. The strength of coupling depends on the local electron‐vibration intra‐tissue molecular environment and the amount of polar solvent water surrounding the net charges on collagen, elastin, and tryptophan. The S values for both non‐welded and welded tissues were almost the same and less than 3, suggesting minimal changes in the local molecular environment as a result of welding. (© 2012 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Influence of silicone oil modification on properties of ramie fiber reinforced polypropylene composites

This paper focused on the analyses of the composition, microstructure, thermal stability and mechanical behavior of modified ramie fiber and its reinforced polypropylene composites. Ramie fiber (RF) was treated with epoxy-silicone oil (ESO) at 160 °C in argon gas. The FTIR and XRD analyses indicated that some silicone molecular chains were bonded on the surface of modified RF, which decreased the crystallinity of the fiber without changing the crystalline type of cellulose. The SEM results of fracture surface showed that the modified RF/PP composite had better interfacial bonding between RF and PP. The mechanical tests showed that the impact strength and the elongation at break of RF/PP were increased by 17.0% and 196% after modification, respectively. The tensile strength of 30RF/PP was improved from 18.95 MPa to 25.96 MPa compared to pure PP. The results of TGA showed that fiber treatment could improve the degradation temperature of RF/PP composites.     

Changing the convexity and concavity of nasal cartilages and cartilage grafts with horizontal mattress sutures: part I. Experimental results

Prior studies indicated that horizontal mattress sutures can control the curvature of a convex lateral crus. This study undertook to ascertain the ideal spacing for mattress sutures, determine what effect they have on the subsequent strength of the cartilage, and compare that to the resultant strength after scoring procedures used to control curvature. Curved fresh cadaver septa of various thicknesses (0.5, 1, and 1.5 mm) were used. The ideal spacing (gap between suture purchases) for the mattress suture was sought in 15 specimens. The consequent change in stiffness (modulus) of the cartilage was measured in nine other specimens before and after suture placement and after scoring. If the spacing was too large, instability resulted. If it was too small, curvature correction could not be obtained. An ideal mattress spacing (6 to 8 mm for 0.5-mm specimens and 8 to 10 mm for 1.5-mm specimens) removed most curvature and provided stability. The mattress suture increased the stiffness (modulus) above normal and far above that when the curvature was removed by scoring. The mean composite modulus before suturing was 4.6 MPa. After ideally spaced sutures, it was 6.2 MPa, a 35 percent increase in stiffness. After scoring to improve curvature, it was 2.4 MPa, a 48 percent reduction in stiffness (p = 0.02, Wilcoxon signed rank test). The horizontal mattress suture technique corrects cartilage curvature if the appropriate spacing is used. The corrected cartilage is stiffer/stronger than normal cartilage and much stiffer/stronger than if scored.