Research ArticlePROSTHETICS

On prosthetic control: A regenerative agonist-antagonist myoneural interface

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Science Robotics  31 May 2017:
Vol. 2, Issue 6, eaan2971
DOI: 10.1126/scirobotics.aan2971
  • Fig. 1 AMI.

    AMI consists of two free muscle grafts linked in agonist-antagonist architecture and placed subdermally on underlying fascia. In the envisioned implementation, efferent control EMG signals from either muscle will be used to control the external prosthesis (position and impedance). Contraction of the agonist muscle will induce stretch and generate proprioceptive afferent signals in the antagonist muscle, which will provide the CNS with valuable information to improve motor control. Prosthetic feedback will be communicated to peripheral nervous system through FES of the antagonist muscle to control the position or force applied on the mechanically linked agonist muscle.

  • Fig. 2 Independently generated EMG.

    Action potentials (blue) are generated in the agonist muscle (top) upon 4-mA electrical stimulation pulses (black) but absent in the antagonist muscle (bottom) from a representative animal. Either muscle is electrically isolated by the insulation of the fascia and tendon-tendon coaptation, and therefore, contraction of the agonist does not cause co-contraction or electrical artifact in the antagonist muscle.

  • Fig. 3 Average strains generated by muscle grafts in the AMI.

    As contraction in the agonist increases in response to electrical stimulation (n = 7), stretch of the antagonist increases. Error bars represent SD.

  • Fig. 4 Electrophysiological testing setup.

    A hook electrode is placed over both nerves to perform either stimulation or afferent ENG signal recording. Two EMG electrodes are placed in each muscle to record bipolar EMG. Under stimulation, we expect the agonist muscle to contract (left), generating EMG signal, and the antagonist muscle to stretch (right), generating ENG signal.

  • Fig. 5 Evoked potentials from agonist muscle grade with stimulation.

    Average peak EMG amplitude for each stimulation amplitude from a representative animal’s agonist muscle demonstrates strong, positive, linear correlation (r2 = 0.85) within the linear range. Stimulation amplitudes above 4 mA were supramaximal and were not regressed. No EMG spikes were generated in the antagonist muscle. Error bars represent SD.

  • Fig. 6 Afferent signals generated from antagonist correlate with muscle strain.

    (Left) The average rectified ENG (rENG) amplitudes in response to increasing antagonist stretch amplitudes from n = 7 animals are shown and correlate linearly (r2 = 0.96). (Center) Raw afferent activity originating from stretch response in the antagonist muscle demonstrates gradation. (Right) As a control case, in which the agonist-antagonist is severed, no afferent signals result, even when agonist muscle is stimulated. Stimulation pulses were delivered at 0.5, 1, and 2 mA (white). Error bars represent SD.

  • Fig. 7 Histology demonstrates reinnervation, regeneration, and revascularization.

    (A) Nerve staining in a cross section of the AMI shows innervating tracts and multiple synapses onto neuromuscular junctions in the muscle graft, as indicated by arrows. Scale bar, 1 mm. (B) H&E stain shows myocytes with centrally located nuclei in a train-line fashion (indicated by arrows), suggesting ongoing regeneration of myocytes. Scale bar, 100 μm. (C) Angioblasts found near the periphery demonstrate regenerating vascular vessels. Scale bar, 200 μm. (D) Regenerated spindle fibers and spindle capsule in a cross section of the muscle graft. Scale bar, 50 μm.

Supplementary Materials

  • robotics.sciencemag.org/cgi/content/full/2/6/eaan2971/DC1

    Fig. S1. AMI structure at surgery and harvest.

    Fig. S2. Time course of denervation.

    Fig. S3. Staining (s46) for spindle fibers.

    Fig. S4. AMI structure (left) and surgery in murine model (right).

    Movie S1. Antagonist-agonist muscles demonstrate coupled motion.

    Movie S2. Insertional needle EMG recording procedure.

  • Supplementary Materials

    Supplementary Material for:

    On prosthetic control: A regenerative agonist-antagonist myoneural interface

    S. S. Srinivasan, M. J. Carty, P. W. Calvaresi, T. R. Clites, B. E. Maimon, C. R. Taylor, A. N. Zorzos, H. Herr*

    *Corresponding author. Email: hherr{at}media.mit.edu

    Published 31 May 2017, Sci. Robot. 2, eaan2971 (2017)
    DOI: 10.1126/scirobotics.aan2971

    This PDF file includes:

    • Fig. S1. AMI structure at surgery and harvest.
    • Fig. S2. Time course of denervation.
    • Fig. S3. Staining (s46) for spindle fibers.
    • Fig. S4. AMI structure (left) and surgery in murine model (right).

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    Other Supplementary Material for this manuscript includes the following:

    • Movie S1 (.mp4 format). Antagonist-agonist muscles demonstrate coupled motion.
    • Movie S2 (.mp4 format). Insertional needle EMG recording procedure.

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