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Selective Activation: Part 1: Page 7

Threshold and Torque Gain

The threshold current, Ithresh, was defined as the current required to achieve 10% of the above defined maximum torque output. The torque gains for the monopolar and tripolar configurations were defined as the slope of the torque recruitment curve between the points that produced 10% and 90% of the maximum torque output.
The torque gains for the monopolar and tripolar configurations in the example shown in the Figure, are –0.4 and –0.2 N-cm/µA respectively.

 

Summary

Summaries for the ratio of monopolar to tripolar threshold current, maximum torque output before spillover and torque output gain, across six experiments, are shown in the Figure.
The histograms are the ratio of monopolar to tripolar threshold current, maximum torque before spillover and torque output gain. Data located on the left side (less than 1) indicate monopolar values that were smaller than the value measured using a tripolar configuration. Data located on the right side (greater than 1) indicate that monopolar values were larger than tripolar values. Monopolar current required to produce 10% of the maximum torque output (threshold) was found to be less than tripolar threshold at a 99% significance level. The mean of the ratio of maximum torque outputs before spillover was found to be between 0.85 and 1.2 with a ratio equal to 1.0 +/- 0.2 at a 99% significance level. The torque output gain of monopolar stimulation was found to be greater than tripolar stimulation at a 99% significance level.
The results of these tests indicate that, provided one can accommodate a higher gain and a lower threshold, a monopolar cuff electrode will perform as well as a tripolar cuff. An advantage of the monopolar configuration over the tripolar configuration is that it has fewer electrode contacts and requiring fewer separate lead wires, making them simpler to manufacture.

 

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Updated : September 07, 2012