Enhanced Zone II Flexor Tendon Repair through a New Half Hitch Loop Suture Configuration

This study evaluated the impact of a new half hitch loop suture configuration on flexor tendon repair mechanics. Cadaver canine flexor digitorum profundus tendons were repaired with 4- or 8-strands, 4–0 or 3–0 suture, with and without half hitch loops. An additional group underwent repair with half hitch loops but without the terminal knot. Half hitch loops improved the strength of 8-strand repairs by 21% when 4–0, and 33% when 3–0 suture was used, and caused a shift in failure mode from suture pullout to suture breakage. 8-strand repairs with half hitch loops but without a terminal knot produced equivalent mechanical properties to those without half hitch loops but with a terminal knot. 4-strand repairs were limited by the strength of the suture in all groups and, as a result, the presence of half hitch loops did not alter the mechanical properties. Overall, half hitch loops improved repair mechanics, allowing failure strength to reach the full capability of suture strength. Improving the mechanical properties of flexor tendon repair with half hitch loops has the potential to reduce the postoperative risk of gap formation and catastrophic rupture in the early postoperative period.     

许旺细胞复合改性PLA\PGA的体外生物学研究

目的：评价小鼠许旺细胞体外复合改性聚乳酸\聚羟基乙酸（PLA\PGA）的细胞活性及生物相容性。方法：转绿色荧光蛋白基 因（GFP）小鼠的许旺细胞传代培养至第2 代,然后通过MTT 检测在不同改性技术（H2O2、NaOH、NaClO4、K2CrO4及超声波）处理 的PLA\PGA 浸提液中许旺细胞的增殖情况,检测许旺细胞在PLA\PGA表面的黏附及其细胞形态。结果：于培养1 d,3 d测得在 不同改性技术处理的PLA\PGA浸提液OD值,1 天时,各浸提液组和对照组相比无显著性差异,许旺细胞的活力及增殖无影响。3 天时,经NaClO4及K2CrO4处理的PLA\PGA 与对照组相比具有统计学差异,影响许旺细胞的增殖,对许旺细胞有毒性;荧光显微 镜下观察到许旺细胞在改性PLA\PGA 表面逐渐伸展,形成伪足,最终粘附在材料表面。结论：经H2O2、NaOH 及超声波改性 PLA\PGA无细胞毒性,具有良好的生物相容性和黏附性,可以用于组织工程化神经的构筑。     

通道辅助微创缝合与两种常用跟腱缝合方式的生物力学研究

目的:通过对比通道辅助跟腱微创缝合方式(CAMIR)与2种临床最常用的跟腱缝合方式的生物力学强度,验证CAMIR微创缝合方式同样能够达到常规缝合方式的力学强度,为临床推广应用提供可靠的理论依据。方法:将27支跟腱样本随机分为3组(每组9支),分别是CAMIR组、经典微创Ma-Griffith组、标准切开Krackow组。所有跟腱样本首先预加载50N,2min。然后以20N-100N,1Hz,循环1000次。如果缝合未失效,则以20 mm/s的速度将样本拉伸至失效。通过实验仪上的传感器自动记录循环1000次时整个缝合结构的伸长量,记录拉伸失效时整个缝合结构的伸长量以及最大负荷,并计算单纯拉伸阶段缝合结构的抗拉伸硬度。结果:CAMIR的循环1000次结束时伸长量(P=0.581)、缝合失效时伸长量(P=0.799)、缝合失效时最大负荷(P=0.278)、单纯拉伸过程中抗应变硬度(P=0.935)与常用的Ma-Griffith、Krackow缝合方式均无明显差异。结论:CAMIR缝合方式强度可靠,为术后进行早期功能康复训练提供力学保障,同时能够有效避免腓肠神经损伤,是临床上值得推荐的微创缝合方式。     

Bundles of Spider Silk,Braided into Sutures,Resist Basic Cyclic Tests: Potential Use for Flexor Tendon Repair

Repair success for injuries to the flexor tendon in the hand is often limited by the in vivo behaviour of the suture used for repair. Common problems associated with the choice of suture material include increased risk of infection, foreign body reactions, and inappropriate mechanical responses, particularly decreases in mechanical properties over time. Improved suture materials are therefore needed. As high-performance materials with excellent tensile strength, spider silk fibres are an extremely promising candidate for use in surgical sutures. However, the mechanical behaviour of sutures comprised of individual silk fibres braided together has not been thoroughly investigated. In the present study, we characterise the maximum tensile strength, stress, strain, elastic modulus, and fatigue response of silk sutures produced using different braiding methods to investigate the influence of braiding on the tensile properties of the sutures. The mechanical properties of conventional surgical sutures are also characterised to assess whether silk offers any advantages over conventional suture materials. The results demonstrate that braiding single spider silk fibres together produces strong sutures with excellent fatigue behaviour; the braided silk sutures exhibited tensile strengths comparable to those of conventional sutures and no loss of strength over 1000 fatigue cycles. In addition, the braiding technique had a significant influence on the tensile properties of the braided silk sutures. These results suggest that braided spider silk could be suitable for use as sutures in flexor tendon repair, providing similar tensile behaviour and improved fatigue properties compared with conventional suture materials.     

Mechanical properties of poly(lactic acid)/starch composites compatibilized by maleic anhydride

Blending poly(lactic acid) (PLA) with wheat starch compatibized by maleic anhydride (MA) was performed with a lab-scale co-extruder. An initiator, 2,5-bis(tert-butylperoxy)-2,5 dimethylhexane (L101), was used to improve compatability among PLA, starch and MA. Interfacial adhesion between PLA and starch was significantly improved. Mechanical properties increased markedly compared to the virgin composites of PLA/starch. The PLA/starch composites at a constant ratio of 55/45 compatibilized by 1% MA and initiated by 10% L101 (MA basis) resulted in the highest tensile strength and elongation.     

Parallel alternating sliding knots are effective for ligation of mesenteric arteries during resection and anastomosis of the equine jejunum

Background

In literature only one article describes and compares methods of achieving hemostasis in equine mesenteric arteries during jejunal resection and anastomosis, and most textbooks favor ligating-dividing mechanical devices. The latter method cannot always be used, not least because the devices are expensive and in some cases even contra-indicated. Various types of knots, including sliding knots, are widely used to provide hemostasis in laparoscopy.The objective of this study was to compare a triple ligature for mesenteric vessels composed of three sliding knots with a triple ligature composed of a modified transfixing and two surgeon’s knots.

Methods

Portions of jejunum with associated mesenteric vessels were collected from 12 horses at a local abattoir. These were divided into 24 specimens containing five mesenteric arteries each. Each artery was closed with a triple ligature. In group A, a surgeon’s knot was used to tie the ligatures (two circumferential and one modified transfixing) while in group B all ligatures (three circumferential) were tied with a parallel alternating sliding knot. Both groups were divided ino two subgroups depending on suture material used (multifilament or monofilament suture material). Time to perform ligatures for every specimen were recorded and compared between groups.After closure, arteries were cannulated and intraluminal pressures were increased until ligature failure. Leaking pressures were recorded and compared between groups.

Results

Ligation of mesenteric arteries was significantly faster to perform with sliding knots than with surgeon’s knots, both with monofilament and multifilament suture material. With multifilament suture material, the leaking pressure of sliding knot ligatures was significantly higher than that of surgeon’s knot ligatures. With monofilament suture, there were no statistically significant differences in leaking pressure between ligature methods. Both ligating methods were stronger with monofilament suture material than with multifilament suture material.

Conclusions

Regardless of the ligature used, monofilament suture material performed better than multifilament suture material to achieve hemostatic knots. Independently of the suture material, the sliding knot is comparable or better than the surgeon’s knot in providing hemostasis, and is faster to perform.

     

Morphology and properties of soy protein and polylactide blends

Blends of soy protein (SP) and a semicrystalline polylactide (PLA) were prepared using a twin-screw extruder. The melt rheology, phase morphology, mechanical properties, water resistance, and thermal and dynamic mechanical properties were investigated on specimens prepared by injection molding of these blends. The melt flowability of soy-based plastics was improved through blending with PLA. Scanning electron microscopy revealed that a co-continuous phase structure existed in the blends with soy protein concentrate (SPC) to PLA ratios ranging from 30:70 to 70:30. SPC/PLA blends showed fine co-continuous phase structures, while soy protein isolate (SPI)/PLA blends presented severe phase coarsening. At the same SP to PLA ratios, SPC/PLA blends demonstrated a higher tensile strength than SPI/PLA blends. The water absorption of soy plastics was greatly reduced by blending with PLA. The compatibility was improved by adding 1-5 phr poly(2-ethyl-2-oxazoline) (PEOX) in the blends, and the resulting blends showed an obvious increase in tensile strength and a reduction in water absorption for SPI/PLA blends. The compatibility between SP and PLA was evaluated by mechanical testing, dynamic mechanical analysis (DMA), water absorption, and scanning electron microscopy (SEM) experiments. Differential scanning calorimetry (DSC) revealed that PLA in the blends was mostly amorphous in the injection molded articles, and SP accelerated the cold crystallization and could increase the final crystallinity of PLA in the blends.     

Effects of composition, solvent, and salt particles on the physicochemical properties of polyglycolide/poly(lactide-co-glycolide) scaffolds

Polyglycolide (PGA)/poly(lactide-co-glycolide) (PLGA) scaffolds were fabricated by a solvent casting/particulate leaching method using hexafluoroisopropanol (HFIP) or acetone for material dissolution and NaCl particles as porogen. The results revealed that the mechanical strength increased as the PGA percentage in a HFIP-processed scaffold increased. Chemical ingredients did not substantially affect the mechanical strength of acetone-processed scaffolds. Large NaCl particles led to weak mechanical strength, low porosity, and small specific surface area. For a fixed composition, PGA crystals in a HFIP-processed scaffold were smaller than those in an acetone-processed scaffold. High PGA fractions yielded partly fused PGA/PLGA scaffolds. A faster degradation rate of a scaffold could result from a higher PGA percentage, smaller NaCl particles, or the existence of chondrocytes. The combination of PGA and PLGA, which compensated each other for bioactivity, would be beneficial to cartilage regeneration.     

Thermal knot fixation

Knots represent the weakest point in suture material. As a result of bending and tension, forces develop within the knot that exceed the strength of the suture material and lead to rupture. Furthermore, because of their relatively large surface area, the most pronounced reactions occur in the vicinity of knots. The results of in vitro experiments conducted with the aim of improving the strength of knots are reported. The knot holding capacity of polypropylene filaments (EP 5/USP 2) was determined at room temperature (22 degrees C) after exposure to temperatures of 63, 98 and 150 degrees C. Knots that were exposed to a temperature of 98 degrees C for 10 seconds had a 50% higher holding capacity than untreated knots. With a higher knot holding capacity, secure fixation can be achieved with fewer knots. Since fewer knots have a smaller surface area, a reduction in tissue reaction may be expected.     

聚乳酸材料在不同土壤环境中生物降解的菌群结构分析

【目的】评价聚乳酸(Polylactic acid,PLA)材料在不同土壤环境中自然降解的效果,通过对3种不同土壤菌群结构的分析,找到能够对聚乳酸材料有降解作用的优势菌群。【方法】通过扫描电镜、断裂拉伸强度和CO2释放量测定来评价3种土壤对PLA材料的降解效果,并运用高通量测序技术,对3种土壤细菌群落进行基因组测序分析,检测3个样本细菌群落的差异性。【结果】PLA材料在沼泽地、芒果林地和稻田中的生物降解率分别为13.7%、10.6%和4.5%。3种土壤的样品分别获得11 110、11 236和8 848个OTU,共涉及细菌域的9个主要门和16个主要科。其中沼泽地土壤的微生物群落丰富度和多样性最高,稻田土壤最低。【结论】结合土壤的降解效果,土壤中生物群落丰富度和多样性越高,对PLA材料的降解作用越好。同时变形菌门(Proteobacteria)和拟杆菌门(Bacteroidetes)是降解聚乳酸材料的优势菌群。在科水平上,黄杆菌科(Flavobacteriaceae)、丛毛单胞菌科(Comamonadaceae)和噬纤维菌科(Cytophagaceae)的微生物对聚乳酸材料的降解最有潜力。这一研究成果为能有效降解聚乳酸材料的微生物资源的开发提供了理论依据。     

Solid state microcellular foamed poly(lactic acid): morphology and property characterization

Poly(lactic acid) or PLA is a plant-based biodegrable plastic which exhibits many properties that are equivalent to or better than many petroleum-based plastics. However, there have been few commercial applications due to its lower impact resistance and higher cost than synthetic plastics. In this paper, the concept of creating microcellular foamed structures in PLA as a means to improve its shortcomings is presented. The effect of the foaming conditions (temperature and time) on the void fraction, volume expansion ratio, impact strength and tensile properties of foamed PLA is discussed. Each step of microcellular processing is addressed including: the manufacture of PLA film; the saturation of the samples with gas; the microcellular foaming of PLA; the void fraction determination, volume expansion ratio calculation, impact and tensile property characterization of foamed samples. The microcellular morphologies developed in PLA samples were a strong function of the foaming conditions. Due to the presence of foamed microcells, a twofold expansion ratio and significant improvements in the impact resistance (twofold increase over unfoamed PLA), strain at break (up to twofold increase over unfoamed PLA) and toughness (up to fourfold increase over unfoamed PLA) were achieved in PLA.     

Study of biodegradable polylactide/poly(butylene adipate-co-terephthalate) blends

Both polylactide (PLA) and poly(butylene adipate-co-terephthalate) (PBAT) are biodegradable polymers. They are thermoplastics which can be processed using most conventional polymer processing methods. PLA is high in strength and modulus (63 MPa and 3.4 GPa, respectively) but brittle (strain at break 3.8%) while PBAT is flexible and tough (strain at break approximately 710%). In view of their complementary properties, blending PLA with PBAT becomes a natural choice to improve PLA properties without compromising its biodegradability. In this study, PLA and PBAT were melt blended using a twin screw extruder. Melt elasticity and viscosity of the blends increased with the concentration of PBAT. Crystallization of the PLA component, phase morphology of the blend, mechanical properties, and toughening mechanism were investigated. The blend comprised an immiscible, two-phase system with the PBAT evenly dispersed in the form of approximately 300 nm domains within the PLA matrix. The PBAT component accelerated the crystallization rate of PLA but had little effect on its final degree of crystallinity. With the increase in PBAT content (5-20 wt %), the blend showed decreased tensile strength and modulus; however, elongation and toughness were dramatically increased. With the addition of PBAT, the failure mode changed from brittle fracture of the neat PLA to ductile fracture of the blend as demonstrated by tensile test and scanning electron microcopy (SEM) micrographs. Debonding between the PLA and PBAT domains induced large plastic deformation in PLA matrix ligaments.     

Mechanical and Morphological Properties of Wood Plastic Biocomposites Prepared from Toughened Poly（lactic acid） and Rubber Wood Sawdust （Hevea brasiliensis）

The present research aims to utilize the acrylic Core-Shell Rubber （CSR） particles to reduce the brittleness in Wood Plastic Composites （WPC） prepared from poly（lactic acid） （PLA） and rubber wood sawdust （Hevea brasiliensis）. Experimental works consisted of two major parts. The first part concentrated on toughening PLA by using CSR particles. Mechanical tests revealed that PLA had become tougher with a more than five times increment in the impact strength when the CSR was added at only 5 wt%. The modified PLA was less stiff with the significant reductions of both elastic and flexural moduli and strengths. The second part focused on producing WPC from the toughened PLA and rubber wood sawdust. The tensile moduli and the strengths of the PLA composites increased with rubber wood content. The composites turned out to be more brittle with reductions of both the impact strength and the tensile elongation at break at all the sawdust contents. Toughening PLA/wood flour with 5 wt% CSR improved both the impact strength and the tensile elongation at break. The toughness enhancement was also depicted by the plastic deformation observed on the surfaces of fractured PLA/CSR/wood sawdust composites.     

Effect of sealer coating on mechanical and physical properties of permanent soft lining materials

doi: 10.1111/j.1741‐2358.2011.00487.x
Effect of sealer coating on mechanical and physical properties of permanent soft lining materials Objective: To evaluate the long‐term effects of sealer coating on tensile bond strength and surface roughness of soft liners. Background: Failure of the bond between resilient liners and denture base significantly compromise the dentures’ longevity. In addition, surface roughness contributes to bacterial adherence on prosthetic materials, increasing the risk of oral infections. Methods: Specimens were manufactured from four reliners [Mucopren Soft (MS), Dentuflex (DF); Soft Comfort Denso (SC) and Ufi Gel SC (USC)], distributed into 10 groups (n = 10), according to material and coating treatment. Tensile bond strength was performed after one year of ageing, while surface roughness was evaluated at 0, 1, 3, 6 and 12 ageing months. Bond strength data were submitted to two‐way anova and Tukey‐HSD tests, while roughness data were submitted to mixed model analysis for repeated measurements (p ≤ 0.05). Results: MS and DF without sealer coating presented the highest tensile bond strength. After coating, DF and SC presented increased tensile bond strength. No surface roughness difference was observed in the non‐coated groups over time, acrylic‐based reliners presented higher roughness. Among coated groups, only SC presented increased surface roughness. Acrylic‐based materials presented reduced roughness at three months. Conclusion: Surface coating was effective for acrylic reliners in maintaining their initial properties. However, sealer coating should be re‐applied every 3 months.     

Silicone fouling-release coatings: effects of the molecular weight of poly(dimethylsiloxane) and tetraethyl orthosilicate on the magnitude of pseudobarnacle adhesion strength

A series of poly(dimethyl siloxane) (PDMS)/silica nanocomposites were synthesized utilizing a sol gel method. The samples were evaluated using pseudobarnacle adhesion and tensile strength tests. The effects of the molecular weight of the PDMS and the size and structure of the silica domains on biofouling release and the mechanical behavior of the PDMS/silica materials were investigated. Three different molecular weights (18,000, 49,000 and 79,000 g mol(-1)) of hydroxyl-terminated PDMS (HT-PDMS) were used to prepare the nanocomposites with three different weight ratios (1:1, 3:1 and 5:1) of HT-PDMS to tetraethyl orthosilicate (TEOS). TEOS served as a crosslinker to form PDMS networks and as a precursor to form silica domains. Two different variants of TEOS with regard to its degree of polymerization (n) (monomeric type: n ≈= 1 and oligomeric type: n ≈= 5) were used for in situ formation of silica particles via the sol-gel process. The mechanical properties of the composites were characterized using stress-strain isotherms. All the mechanical properties evaluated (Young's modulus, tensile strength, energy required for rupture, elongation at break) improved with increases in the molecular weight of the HT-PDMS and the silica content. The pseudobarnacle adhesion test was used to examine the fouling- release (FR) properties of coatings applied on aluminum plates. The rupture energy and tensile strength increased substantially when oligomeric TEOS was employed in the PDMS/silica composites. Scanning electron microscopy (SEM) was used to investigate the structure of the silica domains. It was found that the use of oligomeric TEOS in higher molecular weight PDMS samples with higher PDMS/TEOS weight ratios led to low pseudobarnacle adhesion strengths of ≈ 0.3 MPa, which is in the range of commercial FR coatings.     

Easy alignment and effective nucleation activity of ramie fibers in injection-molded poly(lactic acid) biocomposites

The poly(lactic acid) (PLA)/ramie fiber biocomposites were fabricated, which exhibited considerable reinforcement effect comparable to the glass fiber at the same loading. The attempts were made to understand the flow-induced morphology of ramie fibers and PLA crystals in the injection-molded PLA/ramie fiber biocomposites, thus revealing its relationship to biocomposite mechanical properties. The polarized optical microscopy (POM) and two-dimensional wide-angle X-ray diffraction (2D-WAXD) were for the first time used to determine the distribution of nature fibers, which interestingly showed the ramie fibers aligned well along the flow direction over the whole thickness of injection-molded parts, instead of skin-core structure. This easy alignment of ramie fibers during the common processing was ascribed to the intrinsically high flexibility of ramie fibers and strong interfacial interaction between PLA chains and cellulose molecules of ramie fibers. Both 2D-WAXD and differential scanning calorimeter (DSC) measurements suggested that the PLA matrix in its ramie biocomposites had rather high orientation degree and crystallinity, which was attributed to effective heterogeneous nucleation induced by ramie fibers and local shearing field in the vicinity of fiber surface. Remarkable improvement of mechanical and thermo-mechanical properties was achieved for PLA/ramie fiber biocomposites, without sacrifice of toughness and ductility. Addition of 30wt% ramie fibers increased the tensile strength and modulus of PLA/ramie fiber biocomposites from 65.6 and 1468 MPa for pure PLA to 91.3 and 2977 MPa, respectively. These superior mechanical properties were ascribed to easy alignment of ramie fibers, high crystallinity of PLA, and favorable interfacial adhesion as revealed by scanning electron microscopy (SEM) observation and theoretical analysis based on dynamic mechanical analysis (DMA) data.     

Preparation and characterization of wet spun silk fibroin/poly(vinyl alcohol) blend filaments

Silk fibroin (SF)/poly(vinyl alcohol) (PVA) blend filaments were prepared by a wet spinning process. Regenerated SF and PVA were dissolved in formic acid and the dope solution exhibited good fiber formation in a methanol coagulation bath. Due to the miscibility of SF/PVA in formic acid, the filament had a smooth surface and dense structure with a circular cross-section. The crystalline structure and thermal properties were varied with different SF/PVA ratios. The mechanical properties of the filament were also controlled by blending PVA with SF. Especially, the knot strength of the SF filament, which is a very important suture property, could be significantly improved by blending with PVA.     

Plasticization of poly(L-lactide) with poly(propylene glycol)

A new plasticizer for poly(L-lactide) (PLA)-poly(propylene glycol) (PPG) is proposed. The advantage of using PPG is that it does not crystallize, has low glass transition temperature, and is miscible with PLA. PLA was plasticized with PPGs with nominal Mw of 425 and 1000 g/mol. Poly(ethylene glycol) (PEG), long known as a plasticizer for PLA, with nominal Mw of 600 g/mol, was also used to plasticize PLA for comparison. The thermal and tensile properties of PLA and PLA with 5-12.5 wt % of the plasticizers were studied. In blends of PLA with PPGs the glass transition temperature was lower than that of neat PLA. Both PPGs enhanced the crystallizability of PLA albeit less than PEG. All of the plasticizers increased also the ability of PLA to plastic deformation which was reflected in a decrease of yield stress and in an increase of elongation at break. The effect was enhanced by the higher PPG content and also by lower molecular weight of PPG. A phase separation occurred only in the blend containing 12.5 wt % of PPG with higher molecular weight. The evidences of crazing were found in deformed samples of PLA with low plasticizer content, whereas the samples with higher content of plasticizers crystallized due to deformation.     

Preparation and properties of plasticized poly(lactic acid) films

Poly(lactic acid), PLA, was blended with monomeric and oligomeric plasticizers in order to enhance its flexibility and thereby overcome its inherent problem of brittleness. Differential scanning calorimetry, dynamic mechanical analysis, transmission electron microscopy, and tensile testing were used to investigate the properties of the blends. Monomeric plasticizers, such as tributyl citrate, TbC, and diethyl bishydroxymethyl malonate, DBM, drastically decreased the T(g) of PLA, but the blends showed no morphological stability over time since rapid cold crystallization caused a size reduction of the amorphous domains in PLA. Consequently, the ability of PLA to accommodate the plasticizer diminished with the increase in crystallinity and migration of the plasticizer occurred. Increasing the molecular weight of the plasticizers by synthesizing oligoesters and oligoesteramides resulted in blends that displayed T(g) depressions slightly smaller than with the monomeric plasticizers. The compatibility with PLA was dependent on the molecular weight of the oligomers and on the presence or not of polar amide groups that were able to positively interact with the PLA chains. Aging the materials at ambient temperature revealed that the enhanced flexibility as well as the morphological stability of the films plasticized with the oligomers could be maintained as a result of the higher molecular weight and the polar interactions with PLA.     

Effect of vascular endothelial growth factor on rat Achilles tendon healing

This study evaluated the effect of exogenous vascular endothelial growth factor (VEGF) on tendon healing and regulation of other growth factors in a rat Achilles tendon model. Fifty Sprague-Dawley rats were used. In the experimental group, the left Achilles tendon was transected and repaired with the modified Kessler suture technique, and the right Achilles tendon was transected and repaired with resection of plantaris tendon. VEGF, 100 mul (50 mug/ml), was injected into each tendon at the repair site. The same surgical procedures were performed in the control group, with the same volume of saline injected into the repair sites. At intervals of 1, 2, and 4 weeks, the animals were killed and the tendons were harvested and evaluated for tensile strength (1, 2, and 4 weeks) and gene expression (postoperative day 4). At 1 week postoperatively, when plantaris tendon was preserved, the tensile strength of the repaired tendons with VEGF treatment (3.63 +/- 0.62 MPa) was significantly higher than the tensile strength of the repaired tendons with saline treatment (2.20 +/- 0.36 MPa). There was no difference in tensile strength between the two groups without the plantaris tendon support. At 2 weeks postoperatively, the tensile strength was 11.34 +/- 3.89 MPa in the group with VEGF treatment and plantaris tendon preservation, which was significantly higher than the tensile strength in the other groups. There was no significant difference in tensile strength among the groups at 4 weeks postoperatively. The gene expression showed that transforming growth factor-beta in the VEGF-treated tendon was up-regulated in the early stage of tendon healing, whereas expression of platelet-derived growth factor, basic fibroblast growth factor, and insulin-like growth factor-1 was not significantly different among the groups. In conclusion, administration of exogenous VEGF can significantly improve tensile strength early in the course of the rat Achilles tendon healing and was associated with increased expression of transforming growth factor-beta.