Lumbar root stimulation for restoring leg function: stimulator and measurement of muscle actions.

We are studying the feasibility of restoring lower limb functions to paraplegics by stimulating their lumbar anterior roots (L2-S2). The potential advantages of placing electrodes at the roots, at the cauda equina, were set out by Rushton (1), and our results so far are in a companion paper by Rushton et al. In this paper, we describe briefly the stimulator system and a special apparatus we call the multimoment chair. The stimulator is a development from an earlier design of an implantable peripheral nerve stimulator (2) and has features that make it easier to use. The multimoment chair enables us to gather simultaneously isometric joint moments for 14 axes of the legs during stimulation while the body is fixed in a posture between sitting and full extension. Such rapid data collection is essential to discover the effects of multiple-root stimulation and its functional possibilities.