Vascularized Denervated Muscle Targets Deliver High Quality Signal Amplification
Nicholas von Guionneau, MD1, Connor Glass, BS1, Alexis Lowe, BA1, Alison Wong, MD1, Thomas G.W. Harris, MBChB1, Nitish V. Thakor, PhD2 and Sami Tuffaha, MD3, (1)Johns Hopkins School of Medicine, Baltimore, MD, (2)Biomedical Engineering, Johns Hopkins University School of Medicine, Baltimore, MD, (3)Department of Plastic and Reconstructive Surgery, Johns Hopkins University School of Medicine, Baltimore, MD
Introduction
Vascularized denervated muscle targets (VDMTs) offer a novel approach to achieve signal amplification and intuitive prosthetic control. The surgical approach involves raising (and thereby denervating) a portion of muscle on a vascular leash to act as regenerative target for a nearby transected nerve. VDMTs are similar to regenerative peripheral nerve interphases (RPNIs), but they maintain vascularity. We therefore hypothesize that VDMTs will (a) undergo less fibrosis and resorption; and (b) provide greater signal amplification than occurs with existing techniques.
Methods
In Sprague-Dawley rats, the common peroneal (CP) nerve was transected and implanted into the lateral gastrocnemius muscle that was either 1) vascularized and innervated by native tibial nerve (representing burying nerve into in situ muscle; BIM); 2) devascularized and denervated (RPNI), or 3) vascularized and denervated (VDMT). 4) In untreated controls, the CP nerve was transected without implantation into muscle; (n=5/group). Signal amplification was assessed 100 days post-operatively by stimulating the sciatic nerve and measuring compound motor action potentials (CMAPs) within the lateral gastrocnemius both before and after tibial nerve transection. Fibrosis was assessed by picrosirius red collagen staining. Data were analyzed using Shapiro-Wilk, ANOVA with Tukey post-hoc and T-tests.
Results
Total collagen was significantly less in BIM and VDMT groups (mean +/-SD; 11% +/-4 and 25% +/-6) than in RPNIs (44% +/-12) (p<0.003). VDMTs grossly maintained muscle bulk whereas RPNIs had largely resorbed (Fig.1). CMAPs were present in all groups following sciatic nerve stimulation. After tibial nerve transection - thereby isolating stimulation to the common peroneal pathway - VDMTs maintained robust CMAPs greater than those in all other groups (mean +/-SD; 0.98mV +/-0.19) (p<0.027), while CMAPs in the BIM (0.07mV +/-0.04) and RPNI (0.06mV +/-0.04) groups were no different to CMAPs in the negative control group (0.05mV +/-0.03) (p>0.81). VDMTs demonstrated superior waveform signal-to-noise ratio quality (Fig.2).
Conclusions
VDMTs offer a readily-translatable approach to improve intuitive prosthesis control. Compared to RPNIs, VDMTs:
- Undergo less fibrosis.
- Deliver greater signal amplitude with a higher quality waveform.
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