Nuri Leila, Obst Steven J, Newsham-West Richard, Barrett Rod S
School of Allied Health Sciences, Menzies Health Institute Queensland, Griffith University, Gold Coast, QLD 4222, Australia
School of Health, Medical and Applied Sciences, Central Queensland University, Bundaberg, QLD 4670, Australia.
J Exp Biol. 2017 Sep 1;220(Pt 17):3053-3061. doi: 10.1242/jeb.159764. Epub 2017 Jun 15.
Mid-portion Achilles tendinopathy (MAT) alters the normal three-dimensional (3D) morphology of the Achilles tendon (AT) at rest and under a single tensile load. However, how MAT changes the 3D morphology of the AT during repeated loading remains unclear. This study compared the AT longitudinal, transverse and volume strains during repeated loading of the tendinopathic AT with those of the contralateral tendon in people with unilateral MAT. Ten adults with unilateral MAT performed 10 successive 25 s submaximal (50%) voluntary isometric plantarflexion contractions with both legs. Freehand 3D ultrasound scans were recorded and used to measure whole AT, free AT and proximal AT longitudinal strains and free AT cross-sectional area (CSA) and volume strains. The free AT experienced higher longitudinal and CSA strain and reached steady state following a greater number of contractions (five contractions) in the tendinopathic AT compared with the contralateral tendon (three contractions). Further, free tendon CSA and volume strain were greater in the tendinopathic AT than in the contralateral tendon from the first contraction, whereas free AT longitudinal strain was not greater than that of the contralateral tendon until the fourth contraction. Volume loss from the tendon core therefore preceded the greater longitudinal strain in the tendinopathic AT. Overall, these findings suggest that the tendinopathic free AT experiences an exaggerated longitudinal and transverse strain response under repeated loading that is underpinned by an altered interaction between solid and fluid tendon matrix components. These alterations are indicative of accentuated poroelasticity and an altered local stress-strain environment within the tendinopathic free tendon matrix, which could affect tendon remodelling via mechanobiological pathways.
中段跟腱病（MAT）会改变跟腱（AT）在静息状态和单一拉伸负荷下的正常三维（3D）形态。然而，MAT如何在反复加载过程中改变AT的3D形态仍不清楚。本研究比较了单侧MAT患者患侧跟腱在反复加载过程中的纵向、横向和体积应变与对侧跟腱的相应应变。10名单侧MAT成年患者双腿进行10次连续的25秒次最大强度（50%）自主等长跖屈收缩。记录徒手3D超声扫描图像，并用于测量整个跟腱、游离跟腱和近端跟腱的纵向应变，以及游离跟腱的横截面积（CSA）和体积应变。与对侧跟腱相比（三次收缩），患侧游离跟腱经历了更高的纵向和CSA应变，并且在更多次收缩（五次收缩）后达到稳态。此外，从第一次收缩开始，患侧游离跟腱的CSA和体积应变就大于对侧跟腱，而患侧游离跟腱的纵向应变直到第四次收缩时才大于对侧跟腱。因此，跟腱病患者的跟腱核心体积损失先于更大的纵向应变出现。总体而言，这些发现表明，在反复加载下，患侧游离跟腱经历了夸张的纵向和横向应变反应，这是由固体和流体跟腱基质成分之间改变的相互作用所支撑的。这些改变表明患侧游离跟腱基质内的多孔弹性增强，局部应力应变环境改变，这可能通过机械生物学途径影响跟腱重塑。
