A computational model to design neural interfaces for lower-limb sensory neuroprostheses.
Marek Zelechowski, Giacomo Valle, Stanisa Raspopovic
PMID 32075654WHAT IT FOUND
Computer models of two sciatic nerve shapes suggest a TIME with 20 sites or a FINE with 16 or 20 sites could activate more separate nerve bundles, three TIME implants may be enough, and bipolar stimulation gave better model results.
No patient outcomes were tested.
Key findings
01The model selected 20 active sites as optimal for TIME and 16 or 20 active sites as optimal for FINE, depending on nerve location.
02In the proximal anatomy model, one TIME selectively activated 20.54 ± 7.7% of fascicles, two activated 38.38 ± 14.7%, three activated 54.05 ± 18.9%, and four did not significantly add.
03Bipolar stimulation improved modeled selective recruitment over monopolar by 12.29 ± 4.7% for TIME and 8.9 ± 2.07% for FINE.
STILL TO COME
How it was doneWhat they foundWhat it means for PTs
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What it does not show
This was a computational model, not a clinical trial, so it does not show that lower-limb amputees will feel sensations, walk better, or have fewer falls. The model used only two sciatic nerve anatomies and was not patient-specific. It did not model nerve compression by FINE or the outer paraneurium layer. FINE results were not validated against human FINE data because such data were not available. Validation used upper-limb TIME thresholds, not lower-limb sciatic sensory outcomes. Selectivity was judged by modeled fascicle activation, not by reported sensations or function.
Declared interests
Funded by FP7 Ideas: European Research Council and H2020 Future and Emerging Technologies. The supplied text does not include an author conflict-of-interest declaration.
The easy way to misread this
Do not read the simulated selectivity gains as evidence that lower-limb amputees will walk better or feel natural sensations. The study tested computer models of two nerve anatomies, not patients, and the threshold validation used upper-limb TIME data, not lower-limb sensory outcomes.