Agonist-antagonist Myoneural Interface Research Articles

Using Electrical Muscle Stimulation to Enhance Electrophysiological Performance of Agonist-Antagonist Myoneural Interface.

The agonist-antagonist myoneural interface (AMI), a surgical method to reinnervate physiologically-relevant proprioceptive feedback for control of limb prostheses, has demonstrated the ability to provide natural afferent sensations for limb amputees when actuating their prostheses. Following AMI surgery, one potential challenge is atrophy of the disused muscles, which would weaken the reinnervation efficacy of AMI. It is well known that electrical muscle stimulus (EMS) can reduce muscle atrophy. In this study, we conducted an animal investigation to explore whether the EMS can significantly improve the electrophysiological performance of AMI. AMI surgery was performed in 14 rats, in which the distal tendons of bilateral solei donors were connected and positioned on the surface of the left biceps femoris. Subsequently, the left tibial nerve and the common peroneus nerve were sutured onto the ends of the connected donor solei. Two stimulation electrodes were affixed onto the ends of the donor solei for EMS delivery. The AMI rats were randomly divided into two groups. One group received the EMS treatment (designated as EMS_on) regularly for eight weeks and another received no EMS (designated as EMS_off). Two physiological parameters, nerve conduction velocity (NCV) and motor unit number, were derived from the electrically evoked compound action potential (CAP) signals to assess the electrophysiological performance of AMI. Our experimental results demonstrated that the reinnervated muscles of the EMS_on group generated higher CAP signals in comparison to the EMS_off group. Both NCV and motor unit number were significantly elevated in the EMS_on group. Moreover, the EMS_on group displayed statistically higher CAP signals on the indirectly activated proprioceptive afferents than the EMS_off group. These findings suggested that EMS treatment would be promising in enhancing the electrophysiological performance and facilitating the reinnervation process of AMI.

Agonist-antagonist myoneural interface surgery on the proprioceptive reconstruction of rat hind limb

Currently, prosthesis users rely on visual cues to control their prosthesis. One reason for this is that prostheses cannot provide users with proprioceptive functional signals. For this reason, we propose an agonist-antagonist myoneural interface (AMI) surgery. We examined how this surgery affects the restoration of motor function and proprioceptive reconstruction in the hind limb of Sprague–Dawley rats. The procedure entails grafting the soleus muscle, suturing the two tendon ends of the soleus muscle, and anastomosing the tibial and common peroneal nerves to the soleus muscle. We found that, following surgery, AMI rats exhibited improved neurological repair, shorter walking swings, braking, propulsion, and stance times, and greater compound action potentials than control rats. This means that in rats with neurological impairment of the hind limb, the proposed AMI surgical method significantly improves postoperative walking stability and muscle synergy. AMI surgery may become an option for regaining proprioception in the lost limb.

Resting state neurophysiology of agonist–antagonist myoneural interface in persons with transtibial amputation

The agonist–antagonist myoneural interface (AMI) is an amputation surgery that preserves sensorimotor signaling mechanisms of the central-peripheral nervous systems. Our first neuroimaging study investigating AMI subjects conducted by Srinivasan et al. (2020) focused on task-based neural signatures, and showed evidence of proprioceptive feedback to the central nervous system. The study of resting state neural activity helps non-invasively characterize the neural patterns that prime task response. In this study on resting state functional magnetic resonance imaging in AMI subjects, we compared functional connectivity in patients with transtibial AMI (n = 12) and traditional (n = 7) amputations (TA). To test our hypothesis that we would find significant neurophysiological differences between AMI and TA subjects, we performed a whole-brain exploratory analysis to identify a seed region; namely, we conducted ANOVA, followed by t-test statistics to locate a seed in the salience network. Then, we implemented a seed-based connectivity analysis to gather cluster-level inferences contrasting our subject groups. We show evidence supporting our hypothesis that the AMI surgery induces functional network reorganization resulting in a neural configuration that significantly differs from the neural configuration after TA surgery. AMI subjects show significantly less coupling with regions functionally dedicated to selecting where to focus attention when it comes to salient stimuli. Our findings provide researchers and clinicians with a critical mechanistic understanding of the effect of AMI amputation on brain networks at rest, which has promising implications for improved neurorehabilitation and prosthetic control.

Coupled simulations and parameter inversion for neural system and electrophysiological muscle models

AbstractThe functioning of the neuromuscular system is an important factor for quality of life. With the aim of restoring neuromuscular function after limb amputation, novel clinical techniques such as the agonist‐antagonist myoneural interface (AMI) are being developed. In this technique, the residual muscles of an agonist‐antagonist pair are (re‐)connected via a tendon in order to restore their mechanical and neural interaction. Due to the complexity of the system, the AMI can substantially profit from in silico analysis, in particular to determine the prestretch of the residual muscles that is applied during the procedure and determines the range of motion of the residual muscle pair. We present our computational approach to facilitate this. We extend a detailed multi‐X model for single muscles to the AMI setup, that is, a two‐muscle‐one‐tendon system. The model considers subcellular processes as well as 3D muscle and tendon mechanics and is prepared for neural process simulation. It is solved on high performance computing systems. We present simulation results that show (i) the performance of our numerical coupling between muscles and tendon and (ii) a qualitatively correct dependence of the range of motion of muscles on their prestretch. Simultaneously, we pursue a Bayesian parameter inference approach to invert for parameters of interest. Our approach is independent of the underlying muscle model and represents a first step toward parameter optimization, for instance, finding the prestretch, to be applied during surgery, that maximizes the resulting range of motion. Since our multi‐X fine‐grained model is computationally expensive, we present inversion results for reduced Hill‐type models. Our numerical results for cases with known ground truth show the convergence and robustness of our approach.

A Novel Approach to Lower Extremity Residual Limb Revision to Augment Volitional Motor Control, Restore Proprioception and Reverse Limb Atrophy; The Regenerative Agonist-Antagonist Myoneural Interface

A Novel Approach to Lower Extremity Residual Limb Revision to Augment Volitional Motor Control, Restore Proprioception and Reverse Limb Atrophy; The Regenerative Agonist-Antagonist Myoneural Interface

Transfemoral Amputation Incorporating eOPRA and Agonist-Antagonist Myoneural Interface (AMI) Design: Surgical Technique and Perioperative Care

Transfemoral Amputation Incorporating eOPRA and Agonist-Antagonist Myoneural Interface (AMI) Design: Surgical Technique and Perioperative Care

Clinical, Functional, and Sensorial Outcomes of the Agonist-Antagonist Myoneural Interface (AMI) Ewing Amputation

Clinical, Functional, and Sensorial Outcomes of the Agonist-Antagonist Myoneural Interface (AMI) Ewing Amputation

Experience to date with elective transfemoral amputations incorporating agonist-antagonist myoneural interface (AMI) design

IntroductionThe agonist-antagonist myoneural interface (AMI) is a surgical construct that, when incorporated into limb amputation, offers to potential to preserve or restore proprioception, augment functionality, reduce neuropathic pain and enhance overall limb stability. We here present our experience to date with AMI construction in the context of transfemoral amputation (TFA). MethodsPatients were recruited for TFA with AMI construction at Brigham & Women’s and Brigham & Women’s Faulkner Hospital between June 2018 and June 2023. Data collection included demographic information, intraoperative parameters, clinical recovery metrics and complications. All data was then collated and analyzed. ResultsSeven TFA procedures were performed on seven patients during the study period. The operative technique employed evolved significantly over time, and included the development of both native and regenerative AMI models. Four patients were biological males (57%), and mean patient age was 42.0 ± 14.6 years. The etiology of conditions necessitating amputation included traumatic (43%), oncologic (29%), iatrogenic (14%) and congenital (14%). Mean operative time was 566 ± 97 min and average length of stay was 11.7 ± 8.4 days. Average postoperative follow-up was 2.19 ± 1.57 years (range 0.81–4.30 years). Postoperative imaging of AMI constructs demonstrated average muscle excursions of 6±3 mm, and total average limb volume preservation over time was 102 ± 14%. All patients demonstrated a complete wean from narcotic pain medications, with a mean time to wean of 86 ± 79 days. Minimal neuropathic pain was reported after the acute postoperative period. All seven (100%) of the subjects reported functional phantom limb sensation over the same time. Complications included significant soft tissue necrosis in two (29%) patients and minor wound healing issues in one (14%) patient. ConclusionsTFA incorporating AMI construction appears to offer promising benefits similar to those previously reported in patients undergoing similar interventions at the transtibial level.

Patient Reported Outcome Measures (PROMs) Amongst Lower Extremity Agonist–Antagonist Myoneural Interface (AMI) Amputees

(1) Background: The standard surgical approach to amputation has failed to evolve significantly over the past century. Consequently, standard amputations often fall short with regard to improving the quality of life (QoL) for patients. A modified lower extremity amputation technique incorporating agonist–antagonist myoneural interface (AMI) constructs provides patients with a novel alternative to standard amputation and, to-date, has demonstrated overall significant improvements in their physical and mental wellbeing. (2) Methods: Five PROMs surveys, (1) EQ-5D-3L, (2) Lower Extremity Functional Scale (LEFS), (3) PROMIS-57, (4) Short Form-36 (SF-36), and (5) Sickness Impact Profile (SIP), were administered to our research cohort pre-operatively (baseline) and at various timepoints post-operatively. (3) Results: The cohort’s baseline and 12-month post-operative responses were compared to determine score improvement. Significant improvements were demonstrated across all survey domains (p < 0.05). (4) Conclusions: Modified lower extremity amputation with AMI construction has the potential to provide amputees with increased quality of life when compared to the pre-operative state. However, further investigation is necessary to determine whether the patient-reported outcome measures of the AMI amputee cohort are superior to those who receive a standard amputation.

The Agonist-Antagonist Myoneural Interface in a Transtibial Amputation.

The agonist-antagonist myoneural interface (AMI) technique at the time of transtibial amputation involves the use of agonist-antagonist muscle pairs to restore natural contraction-stretch relationships and to improve proprioceptive feedback when utilizing a prosthetic limb1. Utilizing the standard incision for a long posterior myofasciocutaneous flap, the lateral and medial aspects of the limb are dissected, identifying and preserving the superficial peroneal and saphenous nerve, respectively. The tendons of the tibialis anterior and peroneus longus are transected distally to allow adequate length for the AMI constructs. After ligation of the anterior tibial vessels, the deep peroneal nerve is identified and tagged to create a regenerative peripheral nerve interface (RPNI). The tibia and fibula are cut approximately 15 cm from the medial joint line, facilitating dissection of the deep posterior compartment and ligation of the peroneal and posterior tibial vessels. The tendons of the lateral gastrocnemius and tibialis posterior are transected distally, and the amputation is completed. The extensor retinaculum is harvested from the residual limb along with multiple 2 × 3-cm free muscle grafts, which will be used for the RPNI constructs. The retinaculum is secured to the tibia with suture anchors, and AMI pairs of the lateral gastrocnemius and tibialis anterior as well as the tibialis posterior and peroneus longus are constructed. Separate RPNIs of the major lower-extremity nerves are performed, and the wound is closed in a standard layered fashion. An isometric myodesis of the gastrocnemius without coaptation of agonist-antagonist muscle pairs can be performed at the time of transtibial amputation. The AMI technique restores natural agonist-antagonist relationships at the time of transtibial amputation to increase proprioceptive feedback and improve prosthetic control. These outcomes contrast with those of a traditional isometric myodesis, which prevents proprioceptive communication from the residual limb musculature to the central nervous system. Additionally, the AMI technique allows for concentric and eccentric muscular contractions, which may contribute to the maintenance of limb volume and aid with prosthetic fitting, as opposed to the typical limb atrophy observed following standard transtibial amputation1,2. With the development and availability of more advanced prostheses, the AMI technique offers more precise control and increases the functionality of these innovative devices. Early clinical outcomes of the AMI technique at the time of transtibial amputation have been promising. In a case series of the first 3 patients who underwent the procedure, complications were minor and consisted of 2 episodes of cellulitis and 1 case of delayed wound healing1. Muscle activation measured through electromyography demonstrated an improved ability to limit unintended muscular co-contraction with attempted movement of the phantom limb, as compared with patients who underwent a standard transtibial amputation1. Additionally, residual limb volume was maintained postoperatively without the need for substantial prosthetic modifications. The tendons of the tibialis anterior, peroneus longus, tibialis posterior, and lateral gastrocnemius should be transected as distal as possible to allow adequate length for creation of the AMI constructs.Approximately 2 × 3-cm free muscle grafts are harvested from the amputated extremity for RPNI3.Smooth tendon-gliding through the synovial tunnels should be confirmed before closure. If necessary, muscle debulking can improve gliding and decrease the size of the residual limb.Harvesting the extensor retinaculum for synovial tunnels has been our preferred method, although we acknowledge that other grafts options such as the tarsal tunnel are available1. RPNI = regenerative peripheral nerve interfaceAMI = agonist-antagonist myoneural interfaceEMG = electromyographic.

Beyond Limb Salvage: Limb Restoration Efforts Following Remote Combat-Related Extremity Injuries Optimize Outcomes and Support Sustained Surgical Readiness.

As the combat operational tempo of the military conflicts in Iraq and Afghanistan has declined over the last decade, there has been a decrease in the number of patients requiring acute limb salvage. In their place, a growing population of patients with persistent functional deficits, pain, and inadequate soft tissue coverage stemming from prior limb salvage strategies have returned to our institution seeking revision surgery. Herein, we examine our institution's evolving surgical approach to extremity reconstruction from 2011 through 2019, culminating in the development of our limb restoration concept. We also discuss the impact of this orthoplastic approach on the acute management of complex extremity trauma and its role in providing sustained surgical readiness during interwar years. We retrospectively reviewed all limb reconstructive procedures performed at our tertiary care military treatment facility between September 1, 2011 to December 31, 2019 to characterize the trends in extremity reconstruction procedures performed at our institution. Cases were identified as limb restoration procedures if they involved secondary/revision reconstructive procedures designed to optimize function, treat pain, or improve the durability of the injured extremity following initial reconstruction efforts. Nearly 500 limb restoration procedures were performed during the study period. These procedures steadily increased since 2011, reaching a maximum of 120 in 2018. Orthoplastic procedures such as osseointegration, targeted muscle reinnervation, regenerative peripheral nerve interface, agonist-antagonist myoneural interface, and soft tissue resurfacing flap reconstruction accounted for the rise in secondary/revision reconstruction performed during this time period. Limb restoration is a collaborative orthoplastic approach that utilizes state-of-the-art surgical techniques for treating complex extremity trauma. Although limb restoration originally developed in response to managing the long-term sequelae of combat extremity trauma, the concept can be adapted to the acute management setting. Moreover, limb restoration provides military surgeons with a means for maintaining critical war-time surgical skills during the current low casualty rate era. Level of Evidence: V, therapeutic.

The Agonist-Antagonist Myoneural Interface.

The agonist-antagonist myoneural interface is a novel surgical construct and neural interfacing approach designed to augment volitional control of adapted prostheses, preserve proprioception, and prevent limb atrophy in the setting of limb amputation.

The Agonist-antagonist Myoneural Interface.

Scientist and technologist have long sought to advance limb prostheses that connect directly to the peripheral nervous system, enabling a person with amputation to volitionally control synthetic actuators that move, stiffen and power the prosthesis, as well as to experience natural afferent sensations from the prosthesis. Recently, the agonist-antagonist myoneural interface (AMI) was developed, a mechanoneural transduction architecture and neural interface system designed to provide persons with amputation improved muscle-tendon proprioception and neuroprosthetic control. In this paper, we provide an overview of the AMI, including its conceptual framing and preclinical science, surgical techniques for its construction, and clinical efficacy related to pain mitigation, phantom limb range of motion, fascicle dynamics, central brain proprioceptive sensorimotor preservation, and prosthetic controllability. Following this broad overview, we end with a discussion of current limitations of the AMI and potential resolutions to such challenges.

Restoration of bilateral motor coordination from preserved agonist-antagonist coupling in amputation musculature

BackgroundNeuroprosthetic devices controlled by persons with standard limb amputation often lack the dexterity of the physiological limb due to limitations of both the user’s ability to output accurate control signals and the control system’s ability to formulate dynamic trajectories from those signals. To restore full limb functionality to persons with amputation, it is necessary to first deduce and quantify the motor performance of the missing limbs, then meet these performance requirements through direct, volitional control of neuroprosthetic devices.MethodsWe develop a neuromuscular modeling and optimization paradigm for the agonist-antagonist myoneural interface, a novel tissue architecture and neural interface for the control of myoelectric prostheses, that enables it to generate virtual joint trajectories coordinated with an intact biological joint at full physiologically-relevant movement bandwidth. In this investigation, a baseline of performance is first established in a population of non-amputee control subjects (n = 8). Then, a neuromuscular modeling and optimization technique is advanced that allows unilateral AMI amputation subjects (n = 5) and standard amputation subjects (n = 4) to generate virtual subtalar prosthetic joint kinematics using measured surface electromyography (sEMG) signals generated by musculature within the affected leg residuum.ResultsUsing their optimized neuromuscular subtalar models under blindfolded conditions with only proprioceptive feedback, AMI amputation subjects demonstrate bilateral subtalar coordination accuracy not significantly different from that of the non-amputee control group (Kolmogorov-Smirnov test, P ge 0.052) while standard amputation subjects demonstrate significantly poorer performance (Kolmogorov-Smirnov test, P < 0.001).ConclusionsThese results suggest that the absence of an intact biological joint does not necessarily remove the ability to produce neurophysical signals with sufficient information to reconstruct physiological movements. Further, the seamless manner in which virtual and intact biological joints are shown to coordinate reinforces the theory that desired movement trajectories are mentally formulated in an abstract task space which does not depend on physical limb configurations.

Agonist-antagonist myoneural interface amputation preserves proprioceptive sensorimotor neurophysiology in lower limbs.

The brain undergoes marked changes in function and functional connectivity after limb amputation. The agonist-antagonist myoneural interface (AMI) amputation is a procedure that restores physiological agonist-antagonist muscle relationships responsible for proprioceptive sensory feedback to enable greater motor control. We compared results from the functional neuroimaging of individuals (n = 29) with AMI amputation, traditional amputation, and no amputation. Individuals with traditional amputation demonstrated a significant decrease in proprioceptive activity, measured by activation of Brodmann area 3a, whereas functional activation in individuals with AMIs was not significantly different from controls with no amputation (P < 0.05). The degree of proprioceptive activity in the brain strongly correlated with fascicle activity in the peripheral muscles and performance on motor tasks (P < 0.05), supporting the mechanistic basis of the AMI procedure. These results suggest that surgical techniques designed to restore proprioceptive peripheral neuromuscular constructs result in desirable central sensorimotor plasticity.

Proprioceptive Feedback from AMI Amputation Modulates Cortical and Subcortical Reorganization

Maladaptive cerebral neuroplasticity is a well-established consequence of limb amputation. However, little is known about the potentially causal role of neuromuscular feedback in preserving the cortical and subcortical structures essential for sensation and motor planning, or modulating phantom limb sensation and pain. In this investigation, we study the impact of the agonist-antagonist myoneural interface (AMI) amputation procedure, which preserves proprioceptive neuromuscular feedback, on subcortical and cortical reorganization. We perform neuroimaging on subjects with AMI amputation (AA, n = 10), traditional amputation (TA, n = 10) and no amputation (NA, controls, n = 10). While TAs demonstrate diminished subcortical gray matter volume in the pallidum, accumbens and thalamus (p < 0.05) as compared to NAs, AAs had no significant changes when compared to NAs (p < 0.05). Cortical thickness of Broadmann area 3a and 3b were also significantly increased in TAs, but remained unchanged in AAs, as compared to NAs (p < 0.05). Further, we find phantom limb sensation to be significantly correlated with the reorganization of the accumbens, thalamus, Broadmann area 3a and 3b, suggesting a potential mechanistic linkage to sensorimotor reorganization. The AMI amputation, by preserving afferent proprioceptive feedback, may minimize reorganization and promote conventional sensorimotor neurophysiological pathways.

Towards functional restoration for persons with limb amputation: A dual-stage implementation of regenerative agonist-antagonist myoneural interfaces

While amputation has traditionally been viewed as a failure of therapy, recent developments in amputation surgery and neural interfacing demonstrate improved functionality and bidirectional communication with prosthetic devices. The agonist antagonist myoneural interface (AMI) is one such bi-directional neural communication model comprised of two muscles, an agonist and an antagonist, surgically connected in series within the amputated residuum such that contraction of one muscle stretches the other. By preserving agonist-antagonist muscle dynamics, the AMI allows proprioceptive signals from mechanoreceptors within both muscles to be communicated to the central nervous system. Preliminary human evidence suggests that AMIs have the capacity to provide high fidelity control of a prosthetic device, force feedback, and natural proprioception. However, AMIs have been implemented only in planned amputations and require healthy distal tissues, whereas the majority of amputations occur in patients who do not have healthy distal tissues. Through the use of a dual-stage surgical procedure which leverages existent tissues, this study proposes a revision model for implementation of the AMI in patients who are undergoing traumatic amputation or have already undergone a standard amputation. This paper validates the resulting AMI’s physiology, revealing robust viability and mechanical and electrophysiological function. We demonstrate the presence of H-waves in regenerative grafts, indicating the incorporation of the AMI into physiological reflexive loops.

The Ewing Amputation: The First Human Implementation of the Agonist-Antagonist Myoneural Interface.

The agonist-antagonist myoneural interface (AMI) comprises a surgical construct and neural control architecture designed to serve as a bidirectional interface, capable of reflecting proprioceptive sensation of prosthetic joint position, speed, and torque from and advanced limb prosthesis onto the central nervous system. The AMI surgical procedure has previously been vetted in animal models; we here present the surgical results of its translation to human subjects. Modified unilateral below knee amputations were performed in the elective setting in 3 human subjects between July 2016 and April 2017. AMIs were constructed in each subject to control and interpret proprioception from the bionic ankle and subtalar joints. Intraoperative, perioperative, and postoperative residual-limb outcome measures were recorded and analyzed, including electromyographic and radiographic imaging of AMI musculature. Mean subject age was 38 ± 13 years, and mean body mass index was 29.5 ± 5.5 kg/m2. Mean operative time was 346 ± 87 minutes, including 120 minutes of tourniquet time per subject. Complications were minor and included transient cellulitis and one instance of delayed wound healing. All subjects demonstrated mild limb hypertrophy postoperatively, and intact construct excursion with volitional muscle activation. All patients reported a high degree of phantom limb position perception with no reports of phantom pain. The AMI offers the possibility of improved prosthetic control and restoration of muscle-tendon proprioception. Initial results in this first cohort of human patients are promising and provide evidence as to the potential role of AMIs in the care of patients requiring below knee amputation.

On prosthetic control: A regenerative agonist-antagonist myoneural interface.

Prosthetic limb control is fundamentally constrained by the current amputation procedure. Since the U.S. Civil War, the external prosthesis has benefited from a pronounced level of innovation, but amputation technique has not significantly changed. During a standard amputation, nerves are transected without the reintroduction of proper neural targets, causing painful neuromas and rendering efferent recordings infeasible. Furthermore, the physiological agonist-antagonist muscle relationships are severed, precluding the generation of musculotendinous proprioception, an afferent feedback modality critical for joint stability, trajectory planning, and fine motor control. We establish an agonist-antagonist myoneural interface (AMI), a unique surgical paradigm for amputation. Regenerated free muscle grafts innervated with transected nerves are linked in agonist-antagonist relationships, emulating the dynamic interactions found within an intact limb. Using biomechanical, electrophysiological, and histological evaluations, we demonstrate a viable architecture for bidirectional signaling with transected motor nerves. Upon neural activation, the agonist muscle contracts, generating electromyographic signal. This contraction in the agonist creates a stretch in the mechanically linked antagonist muscle, producing afferent feedback, which is transmitted through its motor nerve. Histological results demonstrate regeneration and the presence of the spindle fibers responsible for afferent signal generation. These results suggest that the AMI will not only produce robust signals for the efferent control of an external prosthesis but also provide an amputee's central nervous system with critical musculotendinous proprioception, offering the potential for an enhanced prosthetic controllability and sensation.

A murine model of a novel surgical architecture for proprioceptive muscle feedback and its potential application to control of advanced limb prostheses

Objective. Proprioceptive mechanisms play a critical role in both reflexive and volitional lower extremity control. Significant strides have been made in the development of bionic limbs that are capable of bi-directional communication with the peripheral nervous system, but none of these systems have been capable of providing physiologically-relevant muscle-based proprioceptive feedback through natural neural pathways. In this study, we present the agonist–antagonist myoneural interface (AMI), a surgical approach with the capacity to provide graded kinesthetic feedback from a prosthesis through mechanical activation of native mechanoreceptors within residual agonist–antagonist muscle pairs. Approach. (1) Sonomicrometery and electroneurography measurement systems were validated using a servo-based muscle tensioning system. (2) A heuristic controller was implemented to modulate functional electrical stimulation of an agonist muscle, using sonomicrometric measurements of stretch from a mechanically-coupled antagonist muscle as feedback. (3) One AMI was surgically constructed in the hindlimb of each rat. (4) The gastrocnemius-soleus complex of the rat was cycled through a series of ramp-and-hold stretches in two different muscle architectures: native (physiologically-intact) and AMI (modified). Integrated electroneurography from the tibial nerve was compared across the two architectures. Main results. Correlation between stretch and afferent signal demonstrated that the AMI is capable of provoking graded afferent signals in response to ramp-and-hold stretches, in a manner similar to the native muscle architecture. The response magnitude in the AMI was reduced when compared to the native architecture, likely due to lower stretch amplitudes. The closed-loop control system showed robustness at high stretch magnitudes, with some oscillation at low stretch magnitudes. Significance. These results indicate that the AMI has the potential to communicate meaningful kinesthetic feedback from a prosthetic limb by replicating the agonist–antagonist relationships that are fundamental to physiological proprioception.