Mersmann Falk, Seynnes Olivier R, Legerlotz Kirsten, Arampatzis Adamantios
Department of Training and Movement Sciences, Humboldt-Universität zu Berlin, Berlin, Germany; Berlin School of Movement Science, Berlin, Germany.
Department of Physical Performance, Norwegian School of Sports Sciences, Oslo, Norway.
J Biomech. 2018 Apr 11;71:176-182. doi: 10.1016/j.jbiomech.2018.02.005. Epub 2018 Feb 11.
The different methods used to assess patellar tendon elongation in vivo may partly explain the large variation of mechanical properties reported in the literature. The present study investigated the effects of tracking landmark position and tibial point of resistive force application during leg extensions in a dynamometer. Nineteen adults performed isometric contractions with a proximal and distal dynamometer shank pad position. Knee joint moments were calculated employing an inverse dynamics approach. Tendon elongation was measured using the patellar apex and either the tibial tuberosity (T) or plateau (P) as tracking landmark. Using P for tracking introduced a bias towards greater values of tendon elongation at all force levels from 100 N to maximum tendon force (TFmax; p < 0.05). The differences between landmarks considering maximum tendon strain were greater at the proximal shank pad position (p < 0.05). Tendon stiffness was lower for P compared with T, but only in intervals up to 50% of TFmax (p < 0.05). The agreement between T and P for stiffness calculated between 50% and TFmax was acceptable with the distal, but poor with the proximal pad position. We demonstrated that using the tibia plateau and not the insertion as tracking landmark clearly affects the assessment of the force-elongation curve of the patellar tendon. However, using a distal point of resistive force application and calculating tendon stiffness between 50% and TFmax seems to yield an acceptable agreement between landmarks. These findings have important implications for the assessment of tendon properties in vivo and cross-study comparisons.
用于在体内评估髌腱伸长的不同方法可能部分解释了文献中报道的力学性能的巨大差异。本研究调查了在测力计中进行腿部伸展时跟踪标志点位置和阻力施加的胫骨点的影响。19名成年人在测力计近端和远端小腿垫位置进行等长收缩。采用逆动力学方法计算膝关节力矩。使用髌尖以及胫骨结节（T）或平台（P）作为跟踪标志点来测量肌腱伸长。在从100 N到最大肌腱力（TFmax）的所有力水平下，使用P进行跟踪会导致肌腱伸长值偏大（p < 0.05）。在近端小腿垫位置，考虑最大肌腱应变时标志点之间的差异更大（p < 0.05）。与T相比，P的肌腱刚度较低，但仅在达到TFmax的50%的区间内如此（p < 0.05）。在50%到TFmax之间计算的刚度，T和P之间在远端垫位置时一致性尚可，但在近端垫位置时较差。我们证明，使用胫骨平台而非附着点作为跟踪标志点会明显影响髌腱力 - 伸长曲线的评估。然而，使用阻力施加的远端点并在50%到TFmax之间计算肌腱刚度，标志点之间似乎能达成可接受的一致性。这些发现对体内肌腱特性评估和跨研究比较具有重要意义。
