Change in the temporal coordination of the finger joints with ulnar nerve block during different power grips analyzed with a sensor glove

  • Nanz Medico
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Ulnar nerve injuries can cause deficient hand movement patterns. Their assessment is important for diagnosis and rehabilitation in hand surgery cases. The purpose of this study was to quantify the changes in temporal coordination of the finger joints during different power grips with an ulnar nerve block by means of a sensor glove. In 21 healthy subjects, the onset and end of the active flexion of the 14 finger joints when gripping objects of different diameters was recorded by a sensor glove. The measurement was repeated after an ulnar nerve block was applied in a standardized setting. The change in the temporal coordination of the metacarpophalangeal (MCP), proximal interphalangeal (PIP) and distal interphalangeal (DIP) joints with and without the nerve block was calculated within the same subject. In healthy subjects, the MCP joints started their movement prior to the PIP joints in the middle and ring finger, whereas this occurred in the reverse order at the index and little finger. The DIP joint onset was significantly delayed (P<0.01). With the ulnar nerve block, this coordination shifted towards simultaneous onset of all joints, independent of the grip diameter. The thumb and index finger were affected the least. With an ulnar nerve block, the PIP joints completed their movement prior to the MCP joints when gripping small objects (G1 and G2), whereas the order was reversed with larger objects (G3 and G4). The alterations with ulnar nerve block affected mainly the little finger when gripping small objects. With larger diameter objects, all fingers had a significant delay at the end of the PIP joint movement relative to the MCP and DIP joints, and the PIP and DIP joint sequence was reversed (P<0.01). Based on the significant changes in temporal coordination of finger flexion during different power grips, there are biomechanical effects of loss of function of the intrinsic muscles caused by an ulnar nerve block on the fine motor skills of the hand. This can be important for the diagnosis and rehabilitation of ulnar nerve lesions of the hand.

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Muscular weakness tends to increase very rapidly due to various medical illnesses such as stroke, paralysis, fibromyalgia, etc. In order to keep tracks of the rehabilitative progress of patients who are suffering from such diseases, it is necessary to acquire data pertaining to finger movements including flexion and extension. Along with range of motions of proximal interphalangeal (PIP), distal interphalangeal (DIP) and meta-capo phalangeal joints, pinching strength is also vital in assessing the progress of rehabilitative therapies. Hence, our objective is to develop an assistive technology in the form of a smart glove comprising of flex and force sensors for measuring flexion and extension movements as well as the pinching strength. To the best of author’s knowledge, commercially available rehabilitation gloves are expensive and have some limitations such as being non-portable, having an antenna mount on the gloves facing upward and so on. The smart glove was able to measure the flexion and extension of finger movements and pinch strength with low-power requirements and low cost associated with production. The flexion and extension of finger movements along with pinching strength of stroke survivors was measured with the aid of the glove and showed promising outcomes. Through the results achieved by our developed glove, we were able to analyze the rehabilitative progress of stroke survivors. Moreover, the data is monitored continuously through liquid crystal display for rehabilitation purposes. Notably, this low cost glove was designed with the aid of flex sensors and force sensors that enabled the effective measurement of flexion, extension and pinching strength of stroke survivors.
Three-dimensional fingertip trajectory was examined under different force levels of the lumbrical muscle to clarify the function of the lumbrical muscle in free index finger motion. The metacarpophalangeal joint balancing effect of the lumbrical muscle in the thumb-up position was also examined. The motions of the finger bones were recorded during simulated contraction of flexor digitorum profundus when different forces (0.000-1.960 N) were applied to the lumbrical muscle in cadaveric specimens. The greater the force with which the lumbrical muscle was pulled, the larger the arc formed by the fingertip, and the greater the rebalancing influence on the metacarpophalangeal joint. This result indicates that the lumbrical muscle functions simultaneously to enlarge the fingertip trajectory and to balance the metacarpophalangeal joint against gravity in the axial plane. A 0.980 N force was ideal for maximal finger movement. The lumbrical muscle rebalanced the metacarpophalangeal joint against gravity in the thumb-up position with a force ⩾0.980 N. © The Author(s) 2015.