Agonist-antagonist myoneural interface amputation preserves proprioceptive sensorimotor neurophysiology in lower limbs.
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ABSTRACT:
SUBMITTER: Srinivasan SS
PROVIDER: S-EPMC7786239 | biostudies-literature |
REPOSITORIES: biostudies-literature
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Project description:BackgroundElucidating underlying mechanisms in subject-specific motor control and perception after amputation could guide development of advanced surgical and neuroprosthetic technologies. In this study, relationships between preserved agonist-antagonist muscle strain within the residual limb and preserved motor control and perception capacity are investigated.MethodsFourteen persons with unilateral transtibial amputations spanning a range of ages, etiologies, and surgical procedures underwent evaluations involving free-space mirrored motions of their lower limbs. Research has shown that varied motor control in biologically intact limbs is executed by the activation of muscle synergies. Here, we assess the naturalness of phantom joint motor control postamputation based on extracted muscle synergies and their activation profiles. Muscle synergy extraction, degree of agonist-antagonist muscle strain, and perception capacity are estimated from electromyography, ultrasonography, and goniometry, respectively.ResultsHere, we show significant positive correlations (P < 0.005-0.05) between sensorimotor responses and residual limb agonist-antagonist muscle strain. Identified trends indicate that preserving even 20-26% of agonist-antagonist muscle strain within the residuum compared to a biologically intact limb is effective in preserving natural motor control postamputation, though preserving limb perception capacity requires more (61%) agonist-antagonist muscle strain preservation.ConclusionsThe results suggest that agonist-antagonist muscle strain is a characteristic, readily ascertainable residual limb structural feature that can help explain variability in amputation outcome, and agonist-antagonist muscle strain preserving surgical amputation strategies are one way to enable more effective and biomimetic sensorimotor control postamputation.
| S-EPMC9356003 | biostudies-literature
Project description:BackgroundThe 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.MethodsModified 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.ResultsMean 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.ConclusionsThe 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.
| S-EPMC6414116 | biostudies-literature
Project description:With advanced age, there is a loss of reaction speed that may contribute to an increased risk of tripping and falling. Avoiding falls and injuries requires awareness of the threat, followed by selection and execution of the appropriate motor response. Using event-related potentials (ERPs) and a simple visual reaction task (RT), the goal of our study was to distinguish sensory and motor processing in the upper- and lower-limbs while attempting to uncover the main cause of age-related behavioral slowing. Strength (amplitudes) as well as timing and speed (latencies) of various stages of stimulus- and motor-related processing were analyzed in 48 healthy individuals (young adults, n = 24, mean age = 34 years; older adults, n = 24, mean age = 67 years). The behavioral results showed a significant age-related slowing, where the younger compared to older adults exhibited shorter RTs for the upper- (222 vs. 255 ms; p = 0.006, respectively) and the lower limb (257 vs. 274 ms; p = 0.048, respectively) as well as lower variability in both modalities (p = 0.001). Using ERP indices, age-related slowing of visual stimulus processing was characterized by overall larger amplitudes with delayed latencies of endogenous potentials in older compared with younger adults. While no differences were found in the P1 component, the later components of recorded potentials for visual stimuli processing were most affected by age. This was characterized by increased N1 and P2 amplitudes and delayed P2 latencies in both upper and lower extremities. The analysis of motor-related cortical potentials (MRCPs) revealed stronger MRCP amplitude for upper- and a non-significant trend for lower limbs in older adults. The MRCP amplitude was smaller and peaked closer to the actual motor response for the upper- than for the lower limb in both age groups. There were longer MRCP onset latencies for lower- compared to upper-limb in younger adults, and a non-significant trend was seen in older adults. Multiple regression analyses showed that the onset of the MRCP peak consistently predicted reaction time across both age groups and limbs tested. However, MRCP rise time and P2 latency were also significant predictors of simple reaction time, but only in older adults and only for the upper limbs. Our study suggests that motor cortical processes contribute most strongly to the slowing of simple reaction time in advanced age. However, late-stage cortical processing related to sensory stimuli also appears to play a role in upper limb responses in the elderly. This process most likely reflects less efficient recruitment of neuronal resources required for the upper and lower extremity response task in older adults.
| S-EPMC9119024 | biostudies-literature
Project description: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 ([Formula: see text]). Then, a neuromuscular modeling and optimization technique is advanced that allows unilateral AMI amputation subjects ([Formula: see text]) and standard amputation subjects ([Formula: see text]) 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, [Formula: see text]) while standard amputation subjects demonstrate significantly poorer performance (Kolmogorov-Smirnov test, [Formula: see text]).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.
| S-EPMC7891024 | biostudies-literature
Project description:Autotomy, self-induced limb loss, is an extreme trait observed throughout the animal kingdom; lizards drop their tails, crickets release their legs, and crabs drop their claws. These repeated evolutionary origins suggest that autotomy is adaptive. Yet, we do not have a firm understanding of the selective pressures that promote and maintain this extreme trait. Although multiple adaptive hypotheses exist, research has generally focused on autotomy's adaptive value as a form of predator escape. However, autotomy could also be selected to reduce the cost of an injured limb, which we investigate here. Previously, this alternative hypothesis has been challenging to directly test because when an injury occurs on an autotomizable limb, that limb is almost always dropped (i.e., autotomy is behaviorally fixed within populations). Recently, however, we have identified a species, Narnia femorata (Insecta: Hemiptera: Coreidae), where some individuals autotomize limbs in response to injury, but some do not. This natural variation allowed us to investigate both the survival costs of retaining an injured limb and the benefits of autotomizing it. In this study, we find a positive association between autotomizing injured limbs and survival, thereby quantifying a new and likely widespread benefit of autotomy-reducing the cost of injury.
| S-EPMC5873245 | biostudies-literature
Project description: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.
| S-EPMC6374452 | biostudies-literature
Project description:BackgroundThe results of lower limb amputation, especially in critically ill patients with severe endogenous intoxication, sepsis, multi-organ failure and severe concomitant diseases are still unsatisfactory. Guillotine amputation is a method routinely used to reduce wound complications associated with wet gangrene and severe cases of diabetic foot, however, it is unclear how well it could help to decrease mortality and improve functional outcome when dealing with critically ill patients.The objectiveof the study was to estimate the effectiveness of two-phase method of urgent low limb amputation among critically ill patients with high risk of complications. The effectiveness was evaluated in terms of perioperative mortality, frequency of early complications and ultimate level of limb loss.Materials and methodsTwo cohort groups of patients with acute lower limb gangrene were retrospectively matched. Approximately 25.8% of patients from the comparison (control) group (N = 240) died without surgery due to severity of their condition and ineffective pre-operative treatment. The remaining patients underwent one-phase high-level amputation after 48-72 h of pre-operative intensive care. The experimental group consisted of 153 patients who underwent guillotine amputation at the lower part of tibia (34.6%), knee disarticulation (32.0%), or open thigh amputation (33.3%), depending on the level of irreversible soft tissue necrosis. The reamputation with the stump shaping was performed later when their health status improved.ResultsThe assessment of treatment outcomes showed that the two-phase amputation in critically ill patients (i) decreased the mortality from 48.7 to 37.9%, (ii) reduced the risk of wound complications from 20.9 to 11.1%, and (iii) improved functional results by saving the knee joint in 34.6 versus 4.5% in comparison/control group.ConclusionThe method of two-phase amputation is recommended for critically ill patients.
| S-EPMC7708686 | biostudies-literature
Project description:Background:Lower limb amputation (LLA) is a complication of lower limb atherosclerosis, infection and tissue gangrene. Following ipsilateral LLA, the risk of major amputation of the contralateral limb or of death is unknown. The aim of this study was to determine the incidence of a contralateral major LLA, comparing those with a non-malignant/non-traumatic ipsilateral major vs. ipsilateral minor LLA. Methods:We used pre-existing linked administrative health databases for the study. Data were provided by the Institute for Clinical Evaluation Sciences (ICES), Toronto, Ontario. This is a retrospective population-based cohort study across Ontario, Canada, 2002-2012. Cause-specific Cox regression models were used to obtain hazard ratios. Cumulative incidence functions were used to calculate the risk of contralateral major LLA and the risk of the competing event death. Individuals who did not survive at least 30 days after their first ipsilateral LLA were excluded since they were ineligible to have a contralateral LLA. Results:5,816 adults underwent an ipsilateral major and 4,143 an ipsilateral minor LLA. The incidences of contralateral major LLA were 4.8 and 2.2 (adjusted HR 2.41, 95% CI 2.04-2.84) after ipsilateral major and minor LLA, respectively. Incidence of death was 18.9 and 11.4 (adjusted HR 1.22, 95% CI 1.13-1.31) following ipsilateral major and minor LLA, respectively. Conclusion:There is high incidence of a contralateral major LLA and even higher risk of death following the ipsilateral LLA. Healthcare professionals should develop strategies for contralateral limb preservation in individuals with existing ipsilateral LLA.
| S-EPMC6180416 | biostudies-literature
Project description:BackgroundFollowing an amputation, the human postural control system develops neuromuscular adaptations to regain an effective postural control. We investigated the compensatory mechanisms behind these adaptations and how sensorimotor integration is affected after a lower-limb transfemoral amputation.MethodsCenter of pressure (CoP) data of 12 unilateral transfemoral amputees and 12 age-matched able-bodied subjects were recorded during quiet standing with eyes open (EO) and closed (EC). CoP adjustments under each leg were recorded to study their contribution to posture control. The spatial structure of the CoP displacements was characterized by measuring the mean distance, the mean velocity of the CoP adjustments, and the sway area. The Entropic Half-Life (EnHL) quantifies the temporal structure of the CoP adjustments and was used to infer disrupted sensory feedback loops in amputees. We expanded the analysis with measures of weight-bearing imbalance and asymmetry, and with two standardized balance assessments, the Berg Balance Scale (BBS) and Timed Up-and-Go (TUG).ResultsThere was no difference in the EnHL values of amputees and controls when combining the contributions of both limbs (p = 0.754). However, amputees presented significant differences between the EnHL values of the intact and prosthetic limb (p < 0.001). Suppressing vision reduced the EnHL values of the intact (p = 0.001) and both legs (p = 0.028), but not in controls. Vision feedback in amputees also had a significant effect (increase) on the mean CoP distance (p < 0.001), CoP velocity (p < 0.001) and sway area (p = 0.007). Amputees presented an asymmetrical stance. The EnHL values of the intact limb in amputees were positively correlated to the BBS scores (EO: ρ = 0.43, EC: ρ = 0.44) and negatively correlated to the TUG times (EO: ρ = - 0.59, EC: ρ = - 0.69).ConclusionThese results suggest that besides the asymmetry in load distribution, there exist neuromuscular adaptations after an amputation, possibly related to the loss of sensory feedback and an altered sensorimotor integration. The EnHL values suggest that the somatosensory system predominates in the control of the intact leg. Further, suppressing the visual system caused instability in amputees, but had a minimal impact on the CoP dynamics of controls. These findings points toward the importance of providing somatosensory feedback in lower-limb prosthesis to reestablish a normal postural control.Trial registrationDRKS00015254 , registered on September 20th, 2018.
| S-EPMC6744715 | biostudies-literature
Project description:Participation in valued interpersonal and community activities is a key component of rehabilitation for Veterans with amputation. The purpose of this study was to identify specific factors that promote or inhibit participation to inform development of interventions that may facilitate participation in desired life activities. A convenience sample of 408 Veterans with at least one lower limb amputation and who had received outpatient care from the Regional Amputation Center (RAC) completed a mailed survey. Participation was measured using the Community Participation Indicators (CPI) Importance, Control, and Frequency scales and the Patient Reported Outcome Measurement Information System (PROMIS) Ability to Participate in Social Roles and Satisfaction with Social Participation scales. Multiple imputation procedures were used to address missing data. Correlates of participation were examined through multiple linear regression. A total of 235 participants completed the survey, a response rate of 58%. Levels of participation, measured with the PROMIS instruments, were 43.2 (SD = 8.1) for Ability and 46.4 (SD = 8.6) for Satisfaction. Regression analyses found robust amputation-specific correlates for participation, including body image and balance confidence. Generic (non-amputation specific) correlates for participation included depression and pain interference. Development of treatment approaches and devices that can address body image, balance confidence, pain, and mental health concerns such as depression have the potential to enhance the participation and rehabilitation of Veterans with lower limb amputation.
| S-EPMC9262244 | biostudies-literature