[Diagnostic ability of power measurement of different grip forms for distal median nerve lesion]. / Stellenwert der Kraftmessung verschiedener Greifformen zur Diagnostik der peripheren Medianusläsion.

BACKGROUND: Peripheral lesions of the median nerve cause characteristic changes of the grip function of the hand. For evaluating grip force changes, measurement by dynamometers (JAMAR dynamometer and pinch dynamometer) is of high relevance. In this study the ability of grip force measurements of different grip forms was evaluated to discriminate between a simulated median nerve lesion and healthy subjects. MATERIAL AND METHODS: In 21 healthy subjects, the grip force of power grip was measured by the JAMAR dynamometer at the second stage including measurement of force at the fingertips and the thenar by a sensor glove. With a pinch dynamometer the power of palmar abduction, precision grip, pincer grip and pinch grip was determined. Measurements were performed with and without median nerve block at the wrist. RESULTS: In power grip of the JAMAR dynamometer at the second stage a significant reduction of the grip force of 13.4% was found (p < 0.03). The power distribution between the fingers D2-D5 did not change with median nerve block. The most relevant reduction of grip force in median nerve block compared with the healthy control was measured in palmar abduction (72.1%, p < 0.0002), followed by precision grip 31.0% (p < 0.0001), pincer grip 23.6% (p < 0.0004) and pinch grip 18.8% (p < 0.0002). CONCLUSIONS: For the discrimination between healthy subjects and subjects with a median nerve block there was a limited relevance of the measurement of the power grip and force distribution at the fingers by the JAMAR dynamometer. However, the best distinction was observed by dynamometric measurement of other grips than power grip, such as palmar abduction, precision grip, pincer grip and pinch grip. The results could be relevant for the clinical diagnostics and rehabilitation of median nerve lesion, complementing the widespread measurement of the power grip by other grip forms.

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.

Improved performance characteristics of the von Willebrand factor ristocetin cofactor activity assay using a novel automated assay protocol.

UNLABELLED: BACKGROUND, OBJECTIVES AND METHODS: An accurate, sensitive and precise assay for reliable determination of the ristocetin cofactor activity of von Willebrand factor (VWF:RCo) in plasma and von Willebrand Factor (VWF)-containing concentrates has been evaluated. The assay is based on a commercially available automated protocol with modifications including a combination of adding additional ristocetin and the use of two calibration curves for the high and low measuring ranges. RESULTS: Addition of extra ristocetin resulted in improved measurement of VWF recoveries from various VWF-containing concentrates that were underestimated using the standard automated protocol. The modifications resulted in improved assay performance over an extended measuring range (2.00-0.03 IUmL(-1) ). Accuracy was tested using VWF deficiency plasma spiked with the 1st international standard (IS) for VWF concentrate. Seven dilutions, ranging from 1.80 to 0.05IUmL(-1) , were analyzed and resulted in measured concentrations between 80% and 100% of the assigned potency of the standard. Linearity was determined from the regression plot of the same concentrate dilutions and resulted in a correlation coefficient of 0.998. The repeatability, expressed as coefficient of variation, was 2% in the normal range (0.90IUmL(-1) ) and 8% at the level of 0.05IUmL(-1) . The corresponding reproducibility results were 2% and 15% at the normal and low measuring ranges, respectively. CONCLUSIONS: Analysis of patients with von Willebrand disease (VWD) indicates that the modified automated BCS(®) protocol has a superior discrimination power compared with the standard protocol. This is especially true in samples with low VWF, as in patients with type 3 VWD.