Muscle Activation After Transtibial Amputation: Clinical and Rehabilitation Insights

Myoelectric Activation Pattern Changes in the Involved Limb of Individuals With Transtibial Amputation During Locomotor State Transitions

Background/Objective: Postural control differs between individuals with lower limb amputation and the general population. Although previous studies examined the effects of unexpected surface perturbations on postural control in individuals with transtibial amputation (TTA) and individuals with transfemoral amputation (TFA), their impact on lower limb muscle activation remains unclear. This study aimed to assess postural control on a stable surface and to evaluate the effects of unexpected surface perturbations on lower limb muscle activation in unilateral TTAs, TFAs, and in a healthy control group (CG). Methods: The study included 10 TTAs, 9 TFAs, and 10 healthy controls. Postural control was assessed using a force platform, and lower limb muscle activity was recorded with surface electromyography during unexpected surface perturbations. Results: The TFAs showed the highest anteroposterior and lateral postural sway under compliant surface eyes closed and the highest lateral sway under normal surface eyes closed, whereas the CG showed the lowest values (p < 0.05). During forward perturbations, rectus femoris (RF) and tibialis anterior (TA) activations were significantly higher than biceps femoris (BF) and medial head of the gastrocnemius (GM) activations, respectively, across all groups (p < 0.05). During backward perturbations, GM activations exceeded TA activations in all groups, while BF activations were higher than RF only in TTAs (p < 0.05). Significant group effects were found for RF and BF during forward perturbations, and side effects for BF (forward) and RF (backward) activations (p < 0.05). Conclusions: Postural control responses vary with the level of lower limb amputation. TFAs relied more on visual input during quiet standing, whereas TTAs demonstrated greater reliance on thigh muscle activation during surface perturbations. These findings highlight the need to consider amputation level in balance and rehabilitation programs.

Objective. The goal of this study was to examine the effects of spinal cord stimulation (SCS) on muscle activity during walking after lower-limb amputation. Amputation results in a loss of sensory feedback and alterations in gait biomechanics, including co-contractions of antagonist muscles about the knee and ankle, and reduced pelvic obliquity range-of-motion and pelvic drop. SCS can restore sensation in the missing limb, but its effects on muscle activation and gait biomechanics have not been studied in people with lower-limb amputation.Approach. This case study included a participant with transtibial amputation who was implanted percutaneously with SCS electrodes over the lumbosacral enlargement for 84 d. SCS was used during in-lab experiments to provide somatosensory feedback from the missing limb, relaying a sense of plantar pressure when the prosthesis was in the stance phase of the gait cycle. We used electromyography (EMG) to record muscle activity from the residual and intact limbs, and 3D motion capture to measure pelvic obliquity and knee and ankle joint angles. EMG signals were recorded during walking with and without SCS at early (Day 30) and late (Day 63) time points across the implant duration.Main results. During walking, co-contraction of knee antagonist muscles was reduced following multiple sessions of SCS-mediated sensory restoration. Additionally, the activation of the hip abductor (tensor fasciae latae) muscle increased activity during gait with SCS-mediated sensory restoration, which corresponded to an increase in pelvic obliquity range-of-motion and pelvic drop, towards normal.Significance. Restoring sensation in the missing limb using SCS altered muscle activity during walking led to improved coordination and pelvic motion in an individual with lower-limb amputation.

The goal of this study was to examine the effects of spinal cord stimulation (SCS) on muscle activity during walking after lower-limb amputation. Amputation results in a loss of sensory feedback and alterations in gait biomechanics, including co-contractions of antagonist muscles about the knee and ankle, and reduced pelvic obliquity range-of-motion and pelvic drop. SCS can restore sensation in the missing limb, but its effects on muscle activation and gait biomechanics have not been studied in people with lower-limb amputation. This case study included a participant with transtibial amputation who was implanted percutaneously with SCS electrodes over the lumbosacral enlargement for 84 days. SCS was used during in-lab experiments to provide somatosensory feedback from the missing limb, relaying a sense of plantar pressure when the prosthesis was in the stance phase of the gait cycle. We used electromyography (EMG) to record muscle activity from the residual and intact limbs, and 3D motion capture to measure pelvic obliquity. EMG signals were recorded during walking with and without SCS at early and late time points across the implant duration. During walking, co-contraction of knee antagonist muscles was reduced following multiple sessions of SCS-mediated sensory restoration. Additionally, the activation of the hip abductor (tensor fasciae latae) muscle increased activity during gait with SCS-mediated sensory restoration, which corresponded to an increase in pelvic obliquity range-of-motion and pelvic drop, towards normal. Restoring sensation in the missing limb using SCS modulated muscle activity during walking leading to improved coordination and pelvic motion in an individual with lower-limb amputation.

Altering prosthetic alignment does not affect hip and low back joint loading during sit-to-stand in people with a transtibial amputation

The metabolic demand of walking generally increases following lower extremity amputation. This study used real-time visual feedback to modify biomechanical factors linked to an elevated metabolic demand of walking in individuals with transtibial amputation. Eight persons with unilateral, traumatic transtibial amputation and 8 uninjured controls participated. Two separate bouts of real-time visual feedback were provided during a single session of gait retraining to reduce 1) center of mass sway and 2) thigh muscle activation magnitudes and duration. Baseline and post-intervention data were collected. Metabolic rate, heart rate, frontal plane center of mass sway, quadriceps and hamstrings muscle activity, and co-contraction indices were evaluated during steady state walking at a standardized speed. Visual feedback successfully decreased center of mass sway 12% (p = 0.006) and quadriceps activity 12% (p = 0.041); however, thigh muscle co-contraction indices were unchanged. Neither condition significantly affected metabolic rate during walking and heart rate increased with center-of-mass feedback. Metabolic rate, center of mass sway, and integrated quadriceps muscle activity were all not significantly different from controls. Attempts to modify gait to decrease metabolic demand may actually adversely increase the physiological effort of walking in individuals with lower extremity amputation who are young, active and approximate metabolic rates of able-bodied adults.

BackgroundPeople with lower-limb amputation lack sensory inputs from their missing limb, which increases their risk of falling. We recently demonstrated that spinal cord stimulation (SCS) can restore sensation in the missing lower limb. Previous studies have shown that SCS can affect motor control by exciting spinal reflex pathways after stroke or spinal cord injury. The effects of SCS on spinal reflex activation have not been studied in people with lower-limb amputation. Furthermore, it is unknown if SCS-evoked spinal reflex activation would perturb walking. Therefore, the goal of this study was to characterize SCS-evoked spinal reflexes in people with lower-limb amputation and quantify effects on gait parameters, including step cycle duration and limb alternation symmetry.MethodsWe implanted percutaneous SCS electrodes over the lumbosacral enlargement in 3 people with transtibial amputation (2 diabetic neuropathy; 1 traumatic) for 28 or 84 days. SCS was delivered to restore sensation in the missing limb during walking based on signals from a pressure-sensing insole in the shoe under the prosthesis. We used electromyography (EMG) to record posterior root-muscle (PRM) reflexes in the residual limb while participants were seated, standing, or walking. We characterized rate-dependent depression and recruitment properties of the PRM reflexes. We used pressure data from instrumented insoles to measure the step cycle duration and limb alternation symmetry with and without SCS.ResultsSCS evoked PRM reflexes in the residual limb muscles in all participants, which was confirmed by the presence of rate-dependent depression at stimulation frequencies ≥ 2 Hz. Overall, there was broad activation of residual limb muscles with SCS that varied with the position of the stimulating electrode relative to the lumbar spinal cord. PRM reflexes were also activated during walking, as confirmed by the presence of rate-dependent depression. However, SCS-evoked PRM reflexes did not disrupt gait, with similar step cycle duration or limb alternation symmetry with and without SCS.ConclusionsRestoring sensation in the missing limb using SCS excites spinal reflexes according to the expected rostral-caudal myotomes but does not disrupt the step cycle duration or limb alternation symmetry in people with transtibial amputation. Therefore, SCS can restore sensory feedback in the missing limb without disrupting the existing motor activation of the residual limb muscles.

By 2020, over 2.2 million people in the United States will be living with an amputated lower limb. The functional impact of amputations presents significant challenges in daily living activities. While significant work has been done to develop smart prosthetics, for the long-term development of effective and robust myoelectric control systems for transtibial amputees, there is still much that needs to be understood regarding how extrinsic muscles of the lower limb are utilized post-amputation. In this study, we examined muscle activity between the intact and residual limbs of three transtibial amputees with the aim of identifying differences in voluntary recruitment patterns during a bilateral motor task. We report that while there is variability across subjects, there are consistencies in the muscle recruitment patterns for the same functional movement between the intact and the residual limb within each subject. These results provide insights for how symmetric activation in residual muscles can be characterized and used to develop myoelectric control strategies for prosthetic devices in transtibial amputees.

The aim of this study was to analyze the effect of the level of amputation and various prosthetic devices on the muscle activation of the sound limb in people with unilateral transfemoral and transtibial amputation. We calculated the global coactivation of 12 muscles using the time-varying multimuscle coactivation function method in 37 subjects with unilateral transfemoral amputation (10, 16, and 11 with mechanical, electronic, and bionic prostheses, respectively), 11 subjects with transtibial amputation, and 22 healthy subjects representing the control group. The results highlighted that people with amputation had a global coactivation temporal profile similar to that of healthy subjects. However, amputation increased the level of the simultaneous activation of many muscles during the loading response and push-off phases of the gait cycle and decreased it in the midstance and swing subphases. This increased coactivation probably plays a role in prosthetic gait asymmetry and energy consumption. Furthermore, people with amputation and wearing electronic prosthesis showed lower global coactivation when compared with people wearing mechanical and bionic prostheses. These findings suggest that the global lower limb coactivation behavior can be a useful tool to analyze the motor control strategies adopted and the ability to adapt to the prosthetic device.

Discrete, rapid (i.e., ballistic like) muscle activation patterns have been observed in ankle muscles (i.e., plantar flexors and dorsiflexors) of able-bodied individuals during voluntary posture control. This observation motivated us to investigate whether transtibial amputees are capable of generating such a ballistic-like activation pattern accurately using their residual ankle muscles in order to assess whether the volitional postural control of a powered ankle prosthesis using proportional myoelectric control via residual muscles could be feasible. In this paper, we asked ten transtibial amputees to generate ballistic-like activation patterns using their residual lateral gastrocnemius and residual tibialis anterior to control a computer cursor via proportional myoelectric control to hit targets positioned at 20% and 40% of maximum voluntary contraction of the corresponding residual muscle. During practice conditions, we asked amputees to hit a single target repeatedly. During testing conditions, we asked amputees to hit a random sequence of targets. We compared movement time to target and end-point accuracy. We also examined motor recruitment synchronization via time-frequency representations of residual muscle activation. The result showed that median end-point error ranged from -0.6% to 1% maximum voluntary contraction across subjects during practice, which was significantly lower compared to testing ( ). Average movement time for all amputees was 242 ms during practice and 272 ms during testing. Motor recruitment synchronization varied across subjects, and amputees with the highest synchronization achieved the fastest movement times. End-point accuracy was independent of movement time. Results suggest that it is feasible for transtibial amputees to generate ballistic control signals using their residual muscles. Future work on volitional control of powered power ankle prostheses might consider anticipatory postural control based on ballistic-like residual muscle activation patterns and direct continuous proportional myoelectric control.

Transtibial amputation can significantly impact an individual's quality of life including the completion of activities of daily living. Those with lower limb amputations can harness the electrical activity from their amputated limb muscles for myoelectric control of a powered prosthesis. While these devices use residual muscles from transtibial-amputated limb as an input to the controller, there is little research characterizing the changes in surface electromyography (sEMG) signal generated by the upper leg muscles. Traditional surface EMG is limited in the number of electrode sites while high-density surface EMG (HDsEMG) uses multiple electrode sites to gather more information from the muscle. This technique is promising for not only the development of myoelectric-controlled prostheses but also advancing our knowledge of muscle behavior with clinical populations, including post-amputation. The HDsEMG signal can be used to develop spatial activation maps and features of these maps can be used to gain valuable insight into muscle behavior. Spatial features of HDsEMG can provide information regarding muscle activation, muscle fiber heterogeneity, and changes in muscle distribution and can be used to estimate properties of both the amputated limb and intact limb. While there are a few studies that have examined HDsEMG in amputated lower limbs they have been limited to movements such as gait. The purpose of this study was to examine the quadriceps muscle during a slow, moderate and fast isokinetic knee extensions from a control group as well as a clinical patient with a transtibial amputation. HDsEMG was collected from the quadriceps of the dominant leg of 14 young, healthy males (mean age = 25.5 ± 7 years old). Signals were collected from both the intact and amputated limb muscle of a 23 year old clinical participant to examine differences between the affected and unaffected leg. It was found that there were differences between the intact and amputated limb limb of the clinical participant with respect to muscle activation and muscle heterogeneity. While this study was limited to one clinical participant, it is important to note the differences in muscle behavior between the intact and amputated limb limb. Understanding these differences will help to improve training protocols for those with amputation.

Transtibial amputation affects postural stability, requiring trunk muscle analysis to support balance and rehabilitation. This pilot study aimed to compare trunk muscle activations during postural sway and limits of stability in unilateral transtibial amputees with healthy controls and investigate the relationship between postural control and trunk muscle activations in transtibial amputees. Accordingly, it was hypothesised that transtibial amputees would exhibit altered postural control and trunk muscle activation, both compared to controls and between limbs. This preliminary observational cross-sectional study included a transtibial amputee group (n = 10) and a healthy control group (n = 10). Static and dynamic balance were assessed using a Bertec force platform. Trunk muscle activation was measured bilaterally using the Delsys wireless surface electromyography system while balance was assessed. Subsequently, group differences in postural control and trunk muscle activation were analyzed. Transtibial amputee group showed significantly greater limits of stability distance on the amputated side compared to controls’ non-dominant side (p < 0.05). Additionally, transtibial amputee group exhibited greater lateral postural sway under compliant surface conditions compared to healthy controls (p < 0.05). During limits of stability assesment, external oblique activation was higher on the intact side of transtibial amputee group compared to controls’ dominant side and higher than on the amputated side (p < 0.05). Multifidus activation on the amputated side during compliant surface with eyes open was greater than the intact side (p < 0.05). Longissimus dorsi activation on the intact side in amputee group exceeded controls’ dominant side under all conditions (p < 0.05). Moreover, longissimus dorsi activation on the amputated side was significantly higher than on the controls’ nondominant side during compliant surface with eyes closed (p < 0.05). Preliminary findings highlight disrupted postural control and trunk muscle activation in transtibial amputees, indicating the need for targeted rehabilitation and larger studies.

BackgroundPowered lower limb prostheses could be more functional if they had access to feedforward control signals from the user’s nervous system. Myoelectric signals are one potential control source. The purpose of this study was to determine if muscle activation signals could be recorded from residual lower limb muscles within the prosthetic socket-limb interface during walking.MethodsWe recorded surface electromyography from three lower leg muscles (tibilias anterior, gastrocnemius medial head, gastrocnemius lateral head) and four upper leg muscles (vastus lateralis, rectus femoris, biceps femoris, and gluteus medius) of 12 unilateral transtibial amputee subjects and 12 non-amputee subjects during treadmill walking at 0.7, 1.0, 1.3, and 1.6 m/s. Muscle signals were recorded from the amputated leg of amputee subjects and the right leg of control subjects. For amputee subjects, lower leg muscle signals were recorded from within the limb-socket interface and from muscles above the knee. We quantified differences in the muscle activation profile between amputee and control groups during treadmill walking using cross-correlation analyses. We also assessed the step-to-step inter-subject variability of these profiles by calculating variance-to-signal ratios.ResultsWe found that amputee subjects demonstrated reliable muscle recruitment signals from residual lower leg muscles recorded within the prosthetic socket during walking, which were locked to particular phases of the gait cycle. However, muscle activation profile variability was higher for amputee subjects than for control subjects.ConclusionRobotic lower limb prostheses could use myoelectric signals recorded from surface electrodes within the socket-limb interface to derive feedforward commands from the amputee’s nervous system.

This study investigates the structural and functional characteristics of residual muscles in transtibial amputees (TTAs) to improve electromyography (EMG)-based prosthetic control. Using ultrasonography, we measured the thickness of the Tibialis Anterior (TA), Peroneus Longus (PL), Gastrocnemius Medialis (GM), and Lateralis (GL) at rest and during contraction. Surface EMG was employed to assess muscle activation patterns, co-contraction levels, and accuracy in modulating submaximal contractions at 25%, 50%, and 75% of maximum voluntary contraction (MVC). Results revealed that muscle thickness on the amputated side was significantly lower than on the sound side (p <0.0001), with the TA and PL exhibiting the greatest atrophy. Despite this, all muscles demonstrated significant increases in thickness during contraction (p<0.0001), indicating preserved neuromuscular activity. GL showed the highest percentage increase in thickness (23.7%), followed by PL (20.5%) and GM (15.4%). EMG analysis demonstrated high co-contraction, particularly between TA and PL, which may complicate selective muscle activation for prosthetic control. During dorsiflexion, PL activation was nearly as high as TA, while TA also exhibited unintended activation during eversion, suggesting poor muscle differentiation. During plantarflexion, GM and GL exhibited dominant activation, while the PL showed substantial co-contraction. Accuracy in controlling submaximal contractions was inconsistent, with TA showing the lowest absolute error (0.17), while GM and GL exhibited the highest errors (0.26 and 0.27, respectively). These findings suggest that TTAs retain the ability to activate residual muscles but struggle with selective activation and intensity modulation, emphasizing the need for targeted training and prosthetic control strategies to optimize functional outcomes.

Introduction In this case series, distal residuum muscle activation during self-paced, fast-paced, and load-carrying walking gaits was compared by traditional transtibial amputation (TTA) or transtibial osteomyoplastic amputation (TOA) approach. Method The activities of the residual muscles (tibialis anterior [TA] and gastrocnemius [GA]) were recorded during the three types of gait that are typically encountered during work-related activities. Results The study shows that there was substantial muscle activity in both the TA and the GA muscles of a TOA subject. On the other hand, the TA in TTA subjects did not show any appreciable activity during any of the gaits. Although the GA muscle in the intact lower limb was active in the late stance phase in both TOA and TTA subjects, this muscle was also active in the loading phase and in the early swing phase in both the groups. This GA activation occurs consistently with supporting the body weight during early stance and preparing the limb for the swing phase during the gait cycle. Conclusions The results of this study lay the foundation for future studies that investigate the effect of muscle activity on the health of the residual transtibial limb.