Staff: Nick Donaldson, Tim Perkins, Jonathan Norton, (UCL), David Rushton, (KCL), Tony Tromans, Ian Swain, Duncan Wood, Carol McFadden, (SDH).

The Lumbo-sacral Anterior Root Stimulator Implant, LARSI, is a 12 channel implanted neuroprosthesis for the restoration of leg function in complete, mid-thoraic paraplegic patients. The implant is placed around the anterior, (ventral or motor) roots from L2 to S2 bilaterally. The implant is both powered and controlled through an RF, (radio frequency) coupled inductive link, meaning that there are no wires protruding through the skin and no implanted batteries. Although designed with the functions of standing and possibly stepping in mind this system has not proved ideal for standing because of the co-contraction of many muscle groups arising from root stimulation. However cycling using the system has been successfully demonstrated. Two patients have been implanted with this system. Stimulating nerve roots gives access to many more muscles than can be stimulated using surface systems and the skin condition and muscle bulk of these patients appears to have improved since they were implanted.

 

The electrodes are pseudo-tripolar, as in the group's previous implant, the Finetech/Brindley bladder controller, which stimulates the sacral anterior roots.

 

 

 

 

 

 

To map the responses to stimulation the group has developed the Multi-Moment Chair System, MMCS. The MMCS is capable of measuring the 14 isometric moments about the leg joints in response to stimulation. This is currently housed in Salisbury District Hospital.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

We are especially grateful to our patients for their patience on this project.