Fine Wire Electrodes

bipolar finewire preparing for finewire insertion deep finewire insertion dual finewire insertion

Bi-polar fine-wire electrodes

We offer two different types of bi-polar fine wire electrode, manufactured to our specifications in the USA. Each electrode comprising of a pair of sterilized fine-wires with hooked ends suitable for intra muscular recordings. We offer to two different length needles - the shorter 30mm needles are used for shallow insertions, while the longer 50mm needles are suitable for placement in deeper muscles.

The physical differences between the two gauges are small (0.1mm). The 27ga needles have a 0.41mm outer diameter with a 0.1mm wall, versus 0.52mm outer diameter with a 0.13mm wall for the 25ga needles. As a result the 50mm needles are slightly stiffer than the 30mm needles, providing easier insertion for the deeper muscles.

Regulatory Approval

These fine-wire electrodes are only sold for human use with EMG systems that have regulatory approval for fine-wire use and incorporate the necessary protections to ensure that they are intrinsically safe. As part of the process of obtaining FDA 510(k) 21CFR890.1375 approval to market our EMG systems we have to show that even in the unlikely event of multiple failures within our systems, the subject would be protected from harm. EMG systems that are classified as biofeedback systems (21CFR882.5050) in the USA do not have FDA approvals to market for fine-wire use to the best of our knowledge.

If in doubt, you should contact your EMG system manufacturer before using these products to verify that your EMG system is designed and approved for fine-wire use with human subjects. We recommend obtaining this confirmation in writing.

Note that although Delsys sell EMG systems for fine wire recording, their web site states that Delsys “makes no assertions or recommendations on the type of recording electrode to use, or the method of its application. This responsibility befalls the electrode manufacturer, the client performing the study and the Institutional Review Board overseeing the study.” This statement, together with their the lack of FDA clearance to be marketed in the USA for clinical applications, suggests that the design of their systems has not been reviewed to ensure that they are intrinsically safe. Given the statement on the Delsys web site, we are unable to supply bi-polar fine-wire electrodes for use with this system, or any other manufacturer who does not have the appropriate regulatory clearances for fine-wire use.

Packaging

Both lengths of fine wire electrode are supplied in packages of twenty (20) electrodes - each electrode is supplied in an individual sterilized package, ready for use without requiring any preparation. Each wire has a 6mm, bare connection end, suitable for thumb-screw or spring connection to our fine-wire preamplifiers, and a 2mm exposed, insertion length. A brief guide to fine-wire needle usage is included with each shipment.

All fine-wire electrodes purchased from Motion Lab Systems have a minimum expiration period of at least one year from the date of purchase and have FDA510(k) approval for marketing for human use in the United States and are CE marked for sale and use within the European Union except Italy.

Specification

The completed fine-wire assemblies are sterilized by gamma radiation, minimum dose of 25kGy with the sterilization validated using the VD-max method (AAMI TIR 27). Nelson Labs in Salt Lake City, UT performs lab testing services for the electrode manufacturer in conjunction with Sterigenics (the contract irradiator).

Each wire is 200mm long, the individual wires are 0.051 mm diameter, 304 series stainless steel with green nylon insulation for improved visibility. Each pair of wires has bare hooked sensor ends with a 2mm exposed sensor (the insulation is offset to avoid short circuits) in the cannula resulting in an insulated tail approximately 130-150mm long, depending on the length of the cannula (50mm or 30mm). The EMG equipment connection to the wire electrode is made to the end of the wire that is clean and free of insulation for 5mm. These electrodes are suitable for connection to any EMG system that has been designed for intra-muscular, fine-wire recording and has the required regulatory approvals.