Two ways to improve myoelectric control for a transhumeral amputee after targeted muscle reinnervation: a case study

Online Muscle Activation Onset Detection Using Likelihood of Conditional Heteroskedasticity of Electromyography Signals

Surface electromyography (sEMG) signals are crucial in developing human-machine interfaces, as they contain rich information about human neuromuscular activities.

OBJECTIVE

The real-time, accurate detection of muscle activation onset (MAO) is significant for EMG-triggered control strategies in embedded applications like prostheses and exoskeletons.

METHODS

This paper investigates sEMG signals using the generalized autoregressive conditional heteroskedasticity (GARCH) model, focusing on variance. A novel feature, the likelihood of conditional heteroskedasticity (LCH) extracted from the maximum likelihood estimation of GARCH parameters, is proposed. This feature effectively distinguishes signal from noise based on heteroskedasticity, allowing for the detection of MAO through the LCH feature and a basic threshold classifier. For online calculation, the model parameter estimation is simplified, enabling direct calculation of the LCH value using fixed parameters.

RESULTS

The proposed method was validated on two open-source datasets and demonstrated superior performance over existing methods. The mean absolute error of onset detection, compared with visual detection results, is approximately 65 ms under online conditions, showcasing high accuracy, universality, and noise insensitivity.

CONCLUSION

The results indicate that the proposed method using the LCH feature from the GARCH model is highly effective for real-time detection of muscle activation onset in sEMG signals.

SIGNIFICANCE

This novel approach shows great potential and possibility for real-world applications, reflecting its superior performance in accuracy, universality, and insensitivity to noise.

Pain and Functional Outcomes following Targeted Muscle Reinnervation: A Systematic Review

BACKGROUND

It is estimated that by 2050, a total of 3.6 million patients will be living with an amputation in the United States. The objective of this systematic review is to evaluate the effect of targeted muscle reinnervation (TMR) on pain and physical functioning in amputees.

METHODS

A literature search was performed on PubMed, Embase, and MEDLINE up to November 28, 2021. Clinical studies assessing the outcomes of TMR (pain, prosthesis control, life quality, limb function, and disability) were included.

RESULTS

Thirty-nine articles were included. The total number of patients who underwent TMR was 449, and 716 were controls. Mean follow-up was 25 months. A total of 309 (66%) lower-limb and 159 (34%) upper-limb amputations took place in the TMR group, the most common being below-knee amputations (39%). The control group included a total of 557 (84%) lower-limb and 108 (16%) upper-limb amputations; the greatest proportion being below-knee amputations in this group as well (54%). Trauma was the most common indication for amputation. Phantom limb pain scores were lower by 10.2 points for intensity ( P = 0.01), 4.67 points for behavior ( P = 0.01), and 8.9 points for interference ( P = 0.09). Similarly, residual limb pain measures were lower for cases for intensity, behavior, and interference, but they failed to reach significance. Neuroma symptoms occurred less frequently, and functional and prosthesis control outcomes improved following TMR.

CONCLUSION

The literature evidence suggests that TMR is a promising therapy for improving pain, prosthesis use, and functional outcomes after limb amputation.

Targeted Muscle Reinnervation: A Systematic Review of Nerve Transfers for the Upper Extremity

INTRODUCTION/BACKGROUND

Despite inspiring improvements in postamputation pain and prosthetic control, targeted muscle reinnervation (TMR) continues to be underused. With some consistency for recommended nerve transfers developing in the literature, it is necessary to systematize these techniques and simplify their incorporation into routine amputation and neuroma care. This systematic review explores the coaptations reported in the literature to date.

METHODS

A systematic review of the literature was performed to collect all reports describing nerve transfers in the upper extremity. The preference was directed toward original studies presenting surgical techniques and coaptations used in TMR. All target muscle options were presented for each nerve transfer in the upper extremity.

RESULTS

Twenty-one original studies describing TMR nerve transfers throughout the upper extremity met inclusion criteria. A comprehensive list of transfers reported for major peripheral nerves at each upper extremity amputation level was included in tables. Ideal nerve transfers were suggested based on convenience and frequency with which certain coaptations were reported.

CONCLUSIONS

Increasingly frequent studies are published with convincing outcomes with TMR and numerous options for nerve transfers and target muscles. It is prudent to appraise these options to provide patients with optimal outcomes. Certain muscles are more consistently targeted and can serve as a baseline plan for the reconstructive surgeon interested in incorporating these techniques.

Targeted Muscle Reinnervation in Partial Hand Amputations

Targeted muscle reinnervation (TMR) surgery has been shown to aid in prevention and treatment of neuropathic pain. Technical and anatomical descriptions of TMR surgery for upper extremity amputees (including transradial, transhumeral, and forequarter amputations) have been reported, yet such descriptions of TMR surgery for partial hand amputations are currently lacking. Herein we outline the technique of different types of partial hand amputation TMR surgeries to serve as a reference and guide. A retrospective review was performed by our multi-institutional team to identify clinical cases where partial hand TMR surgeries were performed. Patient demographics, characteristics, amputation subtype, nerve transfer, pain score, pain outcome, and functional outcome data were collected and analyzed. From January 2018 to September 2019, 13 patients underwent partial hand TMR procedures. Eight cases resulted from trauma, and 6 were secondary to oncologic procedures. The amputations consisted of 8 ray, 2 trans-metacarpal, 2 radial-sided hand, and 1 index finger amputation with recurrent painful neuromas. Twelve patients were weaned off narcotics completely and only 3 remained on a neuromodulator for ongoing pain control. Technical considerations for partial hand TMR surgery have been outlined, with early pilot data showing beneficial pain control outcomes.

The War after War: Volumetric Muscle Loss Incidence, Implication, Current Therapies and Emerging Reconstructive Strategies, a Comprehensive Review

Volumetric muscle loss (VML) is the massive wasting of skeletal muscle tissue due to traumatic events or surgical ablation. This pathological condition exceeds the physiological healing process carried out by the muscle itself, which owns remarkable capacity to restore damages but only when limited in dimensions. Upon VML occurring, the affected area is severely compromised, heavily influencing the affected a person’s quality of life. Overall, this condition is often associated with chronic disability, which makes the return to duty of highly specialized professional figures (e.g., military personnel or athletes) almost impossible. The actual treatment for VML is based on surgical conservative treatment followed by physical exercise; nevertheless, the results, in terms of either lost mass and/or functionality recovery, are still poor. On the other hand, the efforts of the scientific community are focusing on reconstructive therapy aiming at muscular tissue void volume replenishment by exploiting biomimetic matrix or artificial tissue implantation. Reconstructing strategies represent a valid option to build new muscular tissue not only to recover damaged muscles, but also to better socket prosthesis in terms of anchorage surfaces and reinnervation substrates for reconstructed mass.

Control Strategies and Performance Assessment of Upper-Limb TMR Prostheses: A Review

The evolution of technological and surgical techniques has made it possible to obtain an even more intuitive control of multiple joints using advanced prosthetic systems. Targeted Muscle Reinnervation (TMR) is considered to be an innovative and relevant surgical technique for improving the prosthetic control for people with different amputation levels of the limb. Indeed, TMR surgery makes it possible to obtain reinnervated areas that act as biological amplifiers of the motor control. On the technological side, a great deal of research has been conducted in order to evaluate various types of myoelectric prosthetic control strategies, whether direct control or pattern recognition-based control. In the literature, different control performance metrics, which have been evaluated on TMR subjects, have been introduced, but no accepted reference standard defines the better strategy for evaluating the prosthetic control. Indeed, the presence of several evaluation tests that are based on different metrics makes it difficult the definition of standard guidelines for comprehending the potentiality of the proposed control systems. Additionally, there is a lack of evidence about the comparison of different evaluation approaches or the presence of guidelines on the most suitable test to proceed for a TMR patients case study. Thus, this review aims at identifying these limitations by examining the several studies in the literature on TMR subjects, with different amputation levels, and proposing a standard method for evaluating the control performance metrics.

Prosthetic Rehabilitation and Vascularized Composite Allotransplantation following Upper Limb Loss

BACKGROUND

Upper limb loss is a devastating condition with dramatic physical, psychological, financial, and social consequences. Improvements in the fields of prosthetics and vascularized composite allotransplantation have opened exciting new frontiers for treatment and rehabilitation following upper limb loss. Each modality offers a unique set of advantages and limitations with regard to the restoration of hand function following amputation.

METHODS

Presented in this article is a discussion outlining the complex considerations and decisions encountered when determining patient appropriateness for either prosthetic rehabilitation or vascularized composite allotransplantation following upper limb loss. In this review, the authors examine how psychosocial factors, nature of injury, rehabilitation course, functional outcomes, and risks and benefits may affect overall patient selection for either rehabilitative approach.

RESULTS

This review summarizes the current state of the literature. Advancements in both prosthetic and biological strategies demonstrate promise with regard to facilitating rehabilitation following upper limb loss. However, there remains a dearth of research directly comparing outcomes in prosthetic rehabilitation to that following upper extremity transplantation.

CONCLUSIONS

Few studies have performed a direct comparison between patients undergoing vascularized composite allotransplantation and those undergoing prosthetic rehabilitation. Upper extremity transplantation and prosthetic reconstruction should not be viewed as competing options, but rather as two treatment modalities with different risk-to-benefit profiles and indications.