Identification of functional programmable mechanical stimulation (PMS) on tendon not only provides the insight of the tendon homeostasis under physical/pathological condition, but also guides a better engineering strategy for tendon regeneration. The aims of the study are to design a bioreactor system with PMS to mimic the in vivo loading conditions, and to define the impact of different cyclic tensile strain on tendon. Rabbit Achilles tendons were loaded in the bioreactor with/without cyclic tensile loading (0.25 Hz for 8 h/day, 0-9% for 6 days). Tendons without loading lost its structure integrity as evidenced by disorientated collagen fiber, increased type III collagen expression, and increased cell apoptosis. Tendons with 3% of cyclic tensile loading had moderate matrix deterioration and elevated expression levels of MMP-1, 3, and 12, whilst exceeded loading regime of 9% caused massive rupture of collagen bundle. However, 6% of cyclic tensile strain was able to maintain the structural integrity and cellular function. Our data indicated that an optimal PMS is required to maintain the tendon homeostasis and there is only a narrow range of tensile strain that can induce the anabolic action. The clinical impact of this study is that optimized eccentric training program is needed to achieve maximum beneficial effects on chronic tendinopathy management.

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The AB may be preferable to square knots in continuous closures. As many body fluids contain lipid, surgeons should tie knot configurations considered secure in fat. We advise tying a 4+1 AB and placing a minimum of 5 throws to tie SS and SE knots using 3 metric polydioxanone.

Physiotherapy is one of the effective treatments for tendinopathy, whereby symptoms are relieved by changing the biomechanical environment of the pathological tendon. However, the underlying mechanism remains unclear. In this study, we first established a model of progressive tendinopathy-like degeneration in the rabbit Achilles. Following ex vivo loading deprivation culture in a bioreactor system for 6 and 12 days, tendons exhibited progressive degenerative changes, abnormal collagen type III production, increased cell apoptosis, and weakened mechanical properties. When intervention was applied at day 7 for another 6 days by using cyclic tensile mechanical stimulation (6% strain, 0.25 Hz, 8 h/day) in a bioreactor, the pathological changes and mechanical properties were almost restored to levels seen in healthy tendon. Our results indicated that a proper biomechanical environment was able to rescue early-stage pathological changes by increased collagen type I production, decreased collagen degradation and cell apoptosis. The ex vivo model developed in this study allows systematic study on the effect of mechanical stimulation on tendon biology. Keywords: bioreactor; degeneration; ex vivo; tendon; mechanical stimulationTendons are force-transmitting tissues connecting muscle to bone, which have the ability to sense and respond to different mechanical loading. [1][2][3][4][5] Because of this physiological function, biomechanics play an essential role in maintaining tendon homeostasis. [2][3][4][5] Normal healthy tenocytes are long spindle-shaped cells that bind to extracellular matrix proteins including collagen. 6 When tendon is subjected to physiological loading in vivo, the deformation of the cytoskeleton and cellular membrane attached to the collagen fibers can be sensed by cells, which initiate signaling cascades. 6-9 Accumulated evidence shows that in order to maintain normal tendon homeostasis, mechanical stimulation is required. 10-14 Yang et al. have reported that mechanical stretching can modulate proliferation of human tendon fibroblasts in the absence of serum and increase the cellular production of collagen type I, which is at least in part mediated via TGF-b. 15 Zeichen et al. reported that mechanical stress promotes tendon fibroblasts proliferation depending on the stress time. 16 These studies have demonstrated that mechanical loading can increase the diameter of the healed tendons by stimulating tenocyte proliferation and collagen synthesis, and so increase tensile strength. However, the precise physiological levels of strain, frequency, and duration to affect such a response are not well understood.Tendinopathy is a degenerative condition of uncertain etiology, although it is generally considered to be the result of tendon overuse. 17 However, there is increasing evidence that microtearing of tendon caused by general overuse might in fact lead to local understimulation of tenocytes and trigger the degenerative cascade of the tendon. 13,18,19 Clinical findings of tendon degeneration and c...

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Purpose -The purpose of this paper is to describe a preliminary investigation into the heat treatment of Ti-6Al-7Nb components that had been produced via selective laser melting (SLM). Design/methodology/approach -Bars of Ti-6Al-7Nb were produced using SLM by MCP-HEK Tooling GmbH in Lubeck, Germany. These bars were then subjected to a range of heat treatments and the resultant microstructure evaluated with respect to its likely effect on fatigue. Findings -It was found that the as received material consisted of an a 0 martensitic structure in a metastable b matrix. Evidence of the layer-wise thermal history was present, as were large (up to ,500 mm) pores. Solution treatment at 9558C (below the b transus) did not completely disrupt this layered structure and is therefore not recommended. When solution treatment was performed at 1,0558C (above the b transus) a homogeneous structure was produced, with a morphology that depended on the post-solution treatment cooling rate. It was concluded that the most promising heat treatment consisted of a moderate cooling rate after solution treatment at 1,0558C.Research limitations/implications -The study had only limited material and therefore it was not possible to perform any mechanical property testing. Practical implications -The paper presents the initial findings of a project which is aimed at optimising the mechanical properties of Ti-6Al-7Nb components produced using SLM. Originality/value -Currently, little is known about the heat treatment and subsequent mechanical properties of this Ti-6Al-7Nb alloy when produced using rapid manufacturing techniques. Such lack of knowledge limits the potential applications, especially in the biomedical field where the consequences of implant failure are high. The paper presents the first step in developing this understanding.

The estimation of vertebral fracture risk in individuals with suspected osteopenia is commonly based on measurements of lumbar spine bone density. The efficacy of vertebral size and deformity, as assessed by vertebral morphometry, in the prediction of fractures has been less studied. In an ex vivo investigation the regional relationships between vertebral size, vertebral deformity, bone density and compressive strength throughout the thoracolumbar spine were examined. In 16 vertebral columns (T1-L5) the bone mineral content (BMC) and bone mineral density (BMD) of each segment were measured using lateral projection dual-energy X-ray absorptiometry, and the vertebral cancellous density (VCD) and mid-vertebral cross-sectional area (CSA) measured using quantitative computed tomography. Vertebral body heights were determined from mid-sagittal CT scans, and vertical height ratios calculated for each segment. The failure load and failure stress of the isolated vertebral bodies were determined using a material testing device. Separate analyses were performed for the upper (T1-4), middle (T5-8) and lower (T9-12) thoracic, and lumbar (L1-5) segments. In all regions, failure load was strongly correlated with BMD (r = 0.82-0.86), moderately correlated with VCD (r = 0.60-0.71) and vertebral height (r = 0.22-0.49), and poorly correlated with the height ratios (r = 0.04-0.33). Failure stress was best predicted by BMD (r = 0.73-0.78) and VCD (r = 0.70-0.78) but was poorly correlated with all morphometric variables (r = 0.01-0.33). The segmental correlations between BMD and VCD ranged form r = 0.49 to r = 0.79. For all regions, BMD and VCD were included in the stepwise regression models for predicting failure load and failure stress. Either the mid-vertebral height or CSA were included in all the failure load models, while mid-vertebral height was included in only one of the failure stress models. The results suggest that vertebral deformity and size (as assessed by vertebral morphometry) make only a minor contribution to the prediction of vertebral strength additional to that provided by bone densitometry alone. The consistent regional relationships between variables appear to support the practice of global fracture risk assessment based on lumbar spine densitometry.