Experimental Orthopaedics, Department of Clinical and Experimental Medicine, Faculty of Health Science, Linköping University, Linköping, Sweden.
J Appl Physiol (1985). 2012 Nov;113(9):1398-402. doi: 10.1152/japplphysiol.00491.2012. Epub 2012 Aug 30.
Treatment of tendon injuries often involves immobilization. However, immobilization might not prevent mild involuntary isometric muscle contraction. The effect of weak forces on tendon healing is therefore of clinical interest. Studies of tendon healing with various methods for load reduction in rat Achilles tendon models show a consistent reduction in tendon strength by at least half, compared with voluntary cage activity. Unloading was not complete in any of these models, and the healing tendon was therefore still exposed to mild mechanical stimulation. By reducing the forces acting on the tendon even further, we now studied the effects of this mild stimulation. Rat Achilles tendons were transected and allowed to heal spontaneously under four different loading conditions: 1) normal cage activity; 2) calf muscle paralysis induced by botulinum toxin A (Botox); 3) tail suspension; 4) Botox and tail suspension, combined, to eliminate even mild stimulation. Healing was evaluated by mechanical testing after 8 days. Botox alone and suspension alone both reduced tendon callus size (transverse area), thereby impairing its strength compared with normal cage activity. The combination of Botox and suspension did not further reduce tendon callus size but drastically impaired the material properties of the tendon callus compared with each treatment alone. The peak force was only a fifth of that in the normal cage activity group. The results indicate that also the mild loading that occurs with either Botox or suspension alone stimulates tendon healing. This stimulation appears to affect mainly tissue quality, whereas stronger stimulation also increases callus size.
治疗肌腱损伤通常涉及固定。然而，固定可能无法防止轻微的非自愿等长肌肉收缩。因此，弱力对肌腱愈合的影响具有临床意义。使用各种方法减少大鼠跟腱模型中的负荷来研究肌腱愈合的研究表明，与自愿笼活动相比，肌腱强度至少降低一半。在这些模型中，没有任何一种方法能完全卸除负荷，因此愈合的肌腱仍然会受到轻微的机械刺激。通过进一步降低作用于肌腱的力，我们现在研究了这种轻微刺激的效果。将大鼠跟腱切断，并在以下四种不同的加载条件下使其自发愈合：1）正常笼活动；2）用肉毒杆菌毒素 A（Botox）诱导的小腿肌肉麻痹；3）尾部悬吊；4）Botox 和尾部悬吊相结合，以消除甚至轻微的刺激。在 8 天后通过机械测试评估愈合情况。Botox 单独使用和悬吊单独使用都会减小肌腱骨痂的大小（横截面积），从而使其强度与正常笼活动相比受到损害。Botox 和悬吊的组合并未进一步减小肌腱骨痂的大小，但与每种单独治疗相比，严重损害了肌腱骨痂的材料特性。峰值力仅为正常笼活动组的五分之一。结果表明，即使是单独使用 Botox 或悬吊产生的轻微负荷也会刺激肌腱愈合。这种刺激似乎主要影响组织质量，而更强的刺激也会增加骨痂的大小。
