Refshauge K M, Kilbreath S L, Gandevia S C
School of Physiotherapy, The University of Sydney, Australia.
Exp Brain Res. 1998 Sep;122(1):85-92. doi: 10.1007/s002210050494.
To determine whether proprioceptive acuity is the same at all digits, particularly when postured as in a 'grasp', we imposed 10 degrees movements at the distal joint of the thumb, index and ring finger, at three velocities; 1.25 degrees/s, 2.5 degrees/s and 5 degrees/s. The test joint was initially flexed by 25 degrees and the joints proximal to the test joint were maintained in a standard posture for each study. When in a grasp posture that disengaged the extensor muscles at the distal joint of the finger, movement detection at the thumb was superior to that at the fingers for all velocities. However, when the fingers were positioned so that all proprioceptive inputs were able to contribute (i.e. cutaneous, joint and both flexor and extensor muscle afferents), proprioceptive acuity was similar for the three digits. Loss of local cutaneous (and joint) inputs by digital anaesthesia significantly impaired performance at all digits, suggesting a critical role for cutaneous input in normal proprioceptive sensibility at all distal joints of the digits. Anaesthesia of the extensor muscle afferents innervating the thumb did not affect its proprioceptive acuity. Thus, for the thumb, the extensor muscle afferents do not provide critical information. The greater change in muscle fascicle length for the thumb's long flexor muscle (3% per 10 degrees) compared with that in the finger flexor muscles (e.g. 0.1% per 10 degrees) could contribute to the thumb's performance. There appears to be less redundancy of muscle and non-muscle signals for the fingers than for the thumb, because a reduction in either cutaneous or muscle input significantly impaired acuity at the fingers. Overall, when the hand is in a grasping posture, irrespective of the contribution of local cutaneous inputs, the long flexor acting on the thumb may contribute more to its proprioceptive acuity than the long finger flexors contribute to acuity at the fingers.
为了确定本体感觉敏锐度在所有手指是否相同，尤其是在像“抓握”这样的姿势下，我们在拇指、食指和无名指的远端关节处施加了10度的运动，速度有三种：1.25度/秒、2.5度/秒和5度/秒。测试关节最初弯曲25度，并且在每项研究中，测试关节近端的关节保持在标准姿势。当处于使手指远端关节伸肌放松的抓握姿势时，在所有速度下，拇指的运动检测都优于手指。然而，当手指处于所有本体感觉输入都能起作用的位置时（即皮肤、关节以及屈肌和伸肌的传入神经），三个手指的本体感觉敏锐度相似。手指局部皮肤（和关节）输入的丧失会显著损害所有手指的表现，这表明皮肤输入在手指所有远端关节的正常本体感觉敏感度中起关键作用。支配拇指的伸肌传入神经的麻醉并不影响其本体感觉敏锐度。因此，对于拇指来说，伸肌传入神经不提供关键信息。与手指屈肌（例如每10度0.1%）相比，拇指长屈肌的肌束长度变化更大（每10度3%），这可能有助于拇指的表现。与拇指相比，手指的肌肉和非肌肉信号冗余似乎更少，因为皮肤或肌肉输入的减少都会显著损害手指的敏锐度。总体而言，当手处于抓握姿势时，无论局部皮肤输入的作用如何，作用于拇指的长屈肌对其本体感觉敏锐度的贡献可能比作用于手指的长屈肌对手指敏锐度的贡献更大。
