Does an ulnar nerve lesion influence the motion of the index finger?

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

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.

Effects of inertia and wrist oscillations on contralateral neurological postural tremor using the wristalyzer, a new myohaptic device

Upper limb postural tremor consists of mechanical-reflex and central-neurogenic oscillations, superimposed upon a background of irregular fluctuations in muscle force. Muscle spindles play key-roles in the information flow to supra-spinal and spinal generators. Oscillations were delivered using a new generation portable myohaptic device, called ldquowristalyzer,rdquo taking into account the ergonomy of upper limbs and allowing a fine adjustment to each configuration of upper limb segments. The nominal torque of the first generation device is 4 Nm, with a maximal rotation velocity of 300 degrees/s and a range of motion of plusmn45 degrees. Reliability was assessed in basal condition and during loading conditions. We assessed the effects of the addition of inertia on postural tremor of the finger in a group of 26 neurological patients and the effects of wrist oscillations upon contralateral postural tremor in 6 control subjects and in 7 neurological patients exhibiting a postural tremor. Patients showed two different behaviors in response to inertia and exhibited an increased variability of postural tremor during fast oscillations (13.3 Hz). One patient with overactivity of the olivocerebellar pathways exhibited a drop in the peak frequency of more than 20%. The relative power of the 8-12 Hz subband was significantly higher in controls both in basal condition and during oscillations (p = 0.028 and p = 0.015, respectively). The second generation wristalyzer allows to investigate the effects of mechanical oscillations up to frequency of 50 Hz. This mechatronic device can assess the responsiveness of tremor generators to stimulation of muscle spindles and biomechanical loading. Potential applications are the monitoring of dysmetria under various inertial or damping conditions, the assessment of rigidity in Parkinson's disease and the characterization of voluntary muscle force.