Targeted muscle reinnervation and prosthetic rehabilitation after limb loss

A World Update of Progress in Lower Extremity Transplantation: What's Hot and What's Not

ABSTRACT

The field of vascularized composite allotransplantation (VCA) is the new frontier of solid organ transplantation (SOT). VCA spans life-enhancing/life-changing procedures such as upper extremity, craniofacial (including eye), laryngeal, tracheal, abdominal wall, penis, and lower extremity transplants. VCAs such as uterus transplants are life giving unlike any other SOT. Of all VCAs that have shown successful intermediate- to long-term graft survival with functional and immunologic outcomes, lower extremity VCAs have remained largely underexplored. Lower extremity transplantation (LET) can offer patients with improved function compared to the use of conventional prostheses, reducing concerns of phantom limb pain and stump complications, and offer an option for eligible amputees that either fail prosthetic rehabilitation or do not adapt to prosthetics. Nevertheless, these benefits must be carefully weighed against the risks of VCA, which are not trivial, including the adverse effects of lifelong immunosuppression, extremely challenging perioperative care, and delayed nerve regeneration. There have been 5 lower extremity transplants to date, ranging from unilateral or bilateral to quadrimembral, progressively increasing in risk that resulted in fatalities in 3 of the 5 cases, emphasizing the inherent risks. The advantages of LET over prosthetics must be carefully weighed, demanding rigorous candidate selection for optimal outcomes.

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.

Primary Targeted Muscle Reinnervation in Above-Knee Amputations in Patients with Unsalvageable Limbs from Limb-Threatening Ischemia or Infection

BACKGROUND

 Amputees frequently suffer from chronic pain in both their residual limbs (RLP) and phantom limbs (PLP) following their amputation. Targeted muscle reinnervation (TMR) is a nerve transfer technique that has been demonstrated to improve pain secondarily and at time of amputation. The goal of this study is to report on the efficacy of primary TMR at time of above-knee level amputations in the setting of limb-threatening ischemia or infection.

METHODS

 This is a retrospective review of a single-surgeon experience with TMR in patients undergoing through- or above-knee level amputations from January 2018 to June 2021. Patient charts were reviewed for the comorbidities in the Charlson Comorbidity Index. Postoperative notes were assayed for presence and absence of RLP and PLP, overall pain severity, chronic narcotic use, ambulatory status, and complications. A control group of patients undergoing lower limb amputation who did not receive TMR from January 2014 to December 2017 was used for comparison.

RESULTS

 Forty-one patients with through- or above-knee level amputations and primary TMR were included in this study. The tibial and common peroneal nerves were transferred in all cases to motor branches to the gastrocnemius, semimembranosus, semitendinosus, and biceps femoris. Fifty-eight patients with through- or above-knee level amputations without TMR were included for comparison. The TMR group had significantly less overall pain (41.5 vs. 67.2%, p = 0.01), RLP (26.8 vs. 44.8%, p = 0.04), and PLP (19.5 vs. 43.1%, p = 0.02). There were no significant differences in complication rates.

CONCLUSION

 TMR can safely and effectively be performed at time of a through- and above-knee level amputation and improves pain outcomes.

Targeted muscle reinnervation: A narrative review of a novel tool for the management of neuropathic pathology in major lower extremity amputations

OBJECTIVE

The purpose of this narrative review is to provide the vascular surgery community with updated recommendations and information regarding the use of Targeted Muscle Reinnervation (TMR) for both the prevention and treatment of chronic pain and phantom limb pain occurring in patients after undergoing lower extremity amputation for peripheral artery disease.

METHODS

Current available literature discussing TMR is reviewed and included in the article in order to provide a succinct overview on the indications, clinical applications, and surgical technique for TMR. Additionally, early studies showing favorable long-term results after TMR are discussed. Patient consent for publication was obtained for this investigation.

RESULTS

TMR has been demonstrated to be an effective means of both treating and preventing neuroma-related symptoms including chronic pain and phantom limb pain. It has been proven to be technically feasible, and can help patients to have improved utilization of prostheses for ambulation, which can conceivably lead to a reduction in mortality.

CONCLUSIONS

TMR is an important tool to consider for any patient undergoing lower extremity amputation for a vascular-related indication. A vascular-plastic surgeon dual team approach is an effective means to prevent and reduce neuromas and associated chronic pain in this patient population.

Clinical outcomes of peripheral nerve interfaces for rehabilitation in paralysis and amputation: a literature review

Peripheral nerve interfaces (PNIs) are electrical systems designed to integrate with peripheral nerves in patients, such as following central nervous system (CNS) injuries to augment or replace CNS control and restore function. We review the literature for clinical trials and studies containing clinical outcome measures to explore the utility of human applications of PNIs. We discuss the various types of electrodes currently used for PNI systems and their functionalities and limitations. We discuss important design characteristics of PNI systems, including biocompatibility, resolution and specificity, efficacy, and longevity, to highlight their importance in the current and future development of PNIs. The clinical outcomes of PNI systems are also discussed. Finally, we review relevant PNI clinical trials that were conducted, up to the present date, to restore the sensory and motor function of upper or lower limbs in amputees, spinal cord injury patients, or intact individuals and describe their significant findings. This review highlights the current progress in the field of PNIs and serves as a foundation for future development and application of PNI systems.

The application of targeted muscle reinnervation in lower extremity amputations: A systematic review

BACKGROUND

Targeted muscle reinnervation (TMR) is a promising surgical modality for reducing post-amputation pain. We sought to provide a succinct overview of TMR specific to the lower extremity (LE) amputation population.

METHODS

A systematic review was performed per PRISMA guidelines. Ovid MEDLINE, PubMed, and Web of Science were queried for records using various combinations of Medical Subject Heading (MeSH) terms such as "LE "amputation," "below-knee amputation" (BKA), "above-knee amputation" (AKA), and "TMR." Primary outcomes included (1) operative techniques, (2) changes in neuroma, phantom limb pain (PLP), or residual limb pain (RLP), and (3) postoperative complications. Studies were only included if outcomes data were discretely provided for LE patients.

RESULTS

Eleven articles examining 318 patients were identified. Average patient age was 47.5 ± 9.3 years, and most patients were male (n = 246, 77.4%). Eight manuscripts (72.7%) described TMR at the index amputation. The average number of nerve transfers performed per TMR case was 2.1 ± 0.8, and the most commonly employed nerve was the tibial (178/498; 35.7%). Nine (81.8%) articles incorporated patient-reported outcomes after TMR, with common methods including the Numerical Rating Scale (NRS) and questionnaires. Four studies (33.3%) reported functional outcomes such as ambulation ability and prosthesis tolerance. Complications were described in seven manuscripts (58.3%), with postoperative neuroma development being the most common (21/371; 7.2%).

CONCLUSIONS

The application of TMR to LE amputations is effective in reducing PLP and RLP with limited complications. Continued investigations are warranted to better understand patient outcomes specific to anatomic location using validated patient-reported outcome measures (PROM).

Current Concepts in Lower Extremity Amputation: A Primer for Plastic Surgeons

LEARNING OBJECTIVES

After studying this article, the participant should be able to: 1. Understand the goals of lower extremity reconstruction and identify clinical scenarios favoring amputation. 2. Understand lower extremity amputation physiology and biomechanics. 3. Review soft-tissue considerations to achieve durable coverage. 4. Appreciate the evolving management of transected nerves. 5. Highlight emerging applications of osseointegration and strategies to improve myoelectric prosthetic control.

SUMMARY

Plastic surgeons are well versed in lower extremity reconstruction for traumatic, oncologic, and ischemic causes. Limb amputation is an increasingly sophisticated component of the reconstructive algorithm and is indicated when the residual limb is predicted to be more functional than a salvaged limb. Although plastic surgeons have traditionally focused on limb salvage, they play an increasingly vital role in optimizing outcomes from amputation. This warrants a review of core concepts and an update on emerging reconstructive techniques in amputee care.

Targeted muscle reinnervation in upper extremity amputation in military hand surgery: A systematic review

INTRODUCTION

Targeted Muscle Reinnervation (TMR) is a surgical technique utilized to alleviate post-amputation neuroma pain, reduce reliance on narcotic pain medication, and enhance control of prosthetic devices. Motor targets for upper extremity TMR vary depending on injury patterns and amputation levels, with conventional transfer patterns serving as general guides. This study aims to summarize the common patterns of TMR in transradial and transhumeral amputations, focusing on anatomic and surgical considerations.

METHODS

A comprehensive systematic review of TMR literature was conducted by two independent physician reviewers (M.H.A. and D.M.G.R.) to identify the prevailing motor targets, while considering injury patterns and amputation levels.

INCLUSION CRITERIA

1) TMR techniques, outcomes, or advancements; 2) Original research, systematic reviews, meta-analyses, or clinical trials; 3) Peer-reviewed journal articles or reputable conference proceedings.

EXCLUSION CRITERIA

non-English resources, editorials, opinion pieces, and case reports. The databases utilized include MEDLINE (PubMed), EMBASE (Scopus) and Cochrane CENTRAL, last searched 01APR2023.

RESULTS

The reviewed literature revealed multiple motor targets described for upper extremity TMR out of our included 51 studies. However, the selection of motor targets is influenced by the availability of viable options based on injury patterns and amputation levels. Conventional transfer patterns provide useful guidance for determining appropriate motor targets in transradial and transhumeral amputations.

DISCUSSION

TMR has played a significant role in military medicine, particularly in addressing the impact of blast-related injuries. The energy associated with such injuries often results in substantial soft tissue defects, higher amputation levels, and increased post-amputation pain. TMR, in conjunction with advancements in prosthetic technology and ongoing military research, offers improved outcomes to help achieve the goals of active-duty service members. The capabilities and applications of TMR continue to expand rapidly due to its high surgical success rate, technological innovations in prosthetic care, and favorable patient outcomes. As technology evolves to include implantable devices, osseointegration techniques, and bidirectional neuroprosthetic devices, the future of amputation surgery and TMR holds immense promise, offering innovative solutions to optimize patient outcomes. It is important to note, this review was limited to the data available in the included resources which was mostly qualitative; thus, it did not involve primary data analysis.

Free Fillet Flap of Lower Extremity: 38 Amputations with Seven Examples of Targeted Muscle Reinnervation and Regenerative Peripheral Nerve Interfaces

BACKGROUND

Extremely high-level lower extremity amputations are rare procedures that require significant soft-tissue and bony reconstruction. This study describes the use of fillet flaps for oncologic reconstruction and the incorporation of targeted muscle reinnervation (TMR) and regenerative peripheral nerve interfaces (RPNIs) for chronic pain prevention.

METHODS

The authors performed a retrospective review of patients who underwent lower extremity fillet flaps at MD Anderson Cancer Center from January of 2004 through April of 2021. Surgical outcomes were summarized and compared. Numeric rating scale and patient-reported outcomes measures were collected.

RESULTS

Thirty-eight fillet flaps were performed for lower extremity reconstruction. Extirpative surgery included external hemipelvectomy (42%), external hemipelvectomy with sacrectomy (32%), and supratrochanteric above-knee amputation (26%). Median defect size was 600 cm 2 , and 50% included a bony component. Twenty-one patients (55%) experienced postoperative complications, with 16 requiring operative intervention. There was an increased trend toward complications in patients with preoperative radiotherapy, although this was not significant (44% versus 65%; P = 0.203). Seven patients underwent TMR or RPNI. In these patients, the mean numeric rating scale residual limb pain score was 2.8 ± 3.4 ( n = 5; range, 0 to 4/10) and phantom limb pain was 4 ± 3.2 ( n = 6; range, 0 to 7/10). The mean Patient-Reported Outcomes Measures Information Systems T scores were as follows: pain intensity, 50.8 ± 10.6 ( n = 6; range, 30.7 to 60.5); pain interference, 59.2 ± 12.1 ( n = 5; range, 40.7 to 70.1); and pain behavior, 62.3 ± 6.7 ( n = 3; range, 54.6 to 67.2).

CONCLUSIONS

Lower limb fillet flaps are reliable sources of bone, soft tissue, and nerve for reconstruction of oncologic amputation. TMR or RPNI are important new treatment adjuncts that should be considered during every amputation.

CLINICAL QUESTION/LEVEL OF EVIDENCE

Therapeutic, IV.

Phantom limb therapy improves cortical efficiency of the sensorimotor network in a targeted muscle reinnervation amputee: a case report

Targeted muscle reinnervation (TMR) surgery involves the coaptation of amputated nerves to nearby motor nerve branches with the purpose of reclosing the neuromuscular loop in order to reduce phantom limb pain. The purpose of this case study was to create a phantom limb therapy protocol for an amputee after undergoing TMR surgery, where the four main nerves of his right arm were reinnervated into the chest muscles. The goal of this phantom limb therapy was to further strengthen these newly formed neuromuscular closed loops. The case participant (male, 21- years of age, height = 5'8″ and weight = 134 lbs) presented 1- year after a trans-humeral amputation of the right arm along with TMR surgery and participated in phantom limb therapy for 3 months. Data collections for the subject occurred every 2 weeks for 3 months. During the data collections, the subject performed various movements of the phantom and intact limb specific to each reinnervated nerve and a gross manual dexterity task (Box and Block Test) while measuring brain activity and recording qualitative feedback from the subject. The results demonstrated that phantom limb therapy produced significant changes of cortical activity, reduced fatigue, fluctuation in phantom pain, improved limb synchronization, increased sensory sensation, and decreased correlation strength between intra-hemispheric and inter-hemispheric channels. These results suggest an overall improved cortical efficiency of the sensorimotor network. These results add to the growing knowledge of cortical reorganization after TMR surgery, which is becoming more common to aid in the recovery after amputation. More importantly, the results of this study suggest that the phantom limb therapy may have accelerated the decoupling process, which provides direct clinical benefits to the patient such as reduced fatigue and improved limb synchronization.

Osseointegration for Lower Limb Amputation: Understanding the Risk Factors and Time Courses of Soft Tissue Complications

PURPOSE

Lower-limb osseointegrated prostheses are a novel alternative to traditional socket-suspended prostheses, which are often associated with poor fit, soft tissue damage, and pain. Osseointegration eliminates the socket-skin interface and allows for weight-bearing directly on the skeletal system. However, these prostheses can also be complicated by postoperative issues that can negatively impact mobility and quality of life. Little is known about the incidence of or risk factors for these complications as few centers currently perform the procedure.

METHODS

A retrospective analysis was performed on all patients who underwent single-stage lower limb osseointegration at our institution between 2017 and 2021. Patient demographics, medical history, operative data, and outcomes were collected. Fisher exact test and unpaired t tests were performed to identify risk factors for each adverse outcome, and time-to-event survival curves were generated.

RESULTS

Sixty patients met our study criteria: 42 males and 18 females with 35 transfemoral and 25 transtibial amputations. The cohort had an average age of 48 years (range, 25-70 years) and follow-up period of 22 months (range, 6-47 months). Indications for amputation were trauma (50), prior surgical complication (5), cancer (4), and infection (1). Postoperatively, 25 patients developed soft tissue infections, 5 developed osteomyelitis, 6 had symptomatic neuromas, and 7 required soft tissue revisions. Soft tissue infections were positively correlated with obesity and female sex. Neuroma development was associated with increased age at osseointegration. Neuromas and osteomyelitis were both associated with decreased center experience. Subgroup analysis by amputation etiology and anatomic location did not show significant differences in outcomes. Notably, hypertension (15), tobacco use (27), and prior site infection (23) did not correlate with worse outcomes. Forty-seven percent of soft tissue infections occurred in the 1 month after implantation, and 76% occurred in the first 4 months.

CONCLUSIONS

These data provide preliminary insights into risk factors for postoperative complications arising from lower limb osseointegration. These factors are both modifiable (body mass index, center experience), and unmodifiable (sex, age). As this procedure continues to expand in popularity, such results are necessary to inform best practice guidelines and optimize outcomes. Further prospective studies are needed to confirm the above trends.

Targeted Muscle Reinnervation in the Setting of Traumatic Bilateral Above-Knee Amputations: A Case Report

CASE

We present the case of a 20-year-old man who was pedestrian struck and sustained bilateral traumatic above-knee amputations. Targeted muscle reinnervation (TMR) was performed with nerve transfers, including tibial nerve to semitendinosus (bilateral), superficial peroneal nerve to biceps femoris (left), deep peroneal nerve to biceps femoris (left), and common peroneal nerve to biceps femoris (right).

CONCLUSIONS

Less than 1 year postoperatively, the patient was ambulating on his myoelectric prosthesis and experienced no Tinel or neuroma-type pain. This case is a testament to the impact TMR, an innovative surgical technique, can have on the quality of life of patients sustaining devastating limb injuries.

Osseointegration for Lower-Extremity Amputees: Operative Considerations from the Plastic Surgeon's Perspective

➢

Osseointegration for lower-extremity amputees, while increasing in frequency, remains in its relative infancy compared with traditional socket-based prostheses.

➢

Ideal candidates for osseointegration have documented failure of a traditional prosthesis and should be skeletally mature, have adequate bone stock, demonstrate an ability to adhere to a longitudinal rehabilitation protocol, and be in an otherwise good state of health.

➢

Lowering the reoperation rate for soft-tissue complications depends heavily on surgical technique and on the implant device itself; the current gold standard involves a smooth implant surface for dermal contact as well as maximal skin resection to prevent skin breakdown against the prosthesis. This may include the need for thighplasty to optimize skin reduction.

➢

Interdisciplinary peripheral nerve management, such as targeted muscle reinnervation, performed in tandem with a plastic surgery team can treat existing and prevent future symptomatic neuromas, ultimately improving pain outcomes.

Agonist-antagonist muscle strain in the residual limb preserves motor control and perception after amputation

Background

Elucidating 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.

Methods

Fourteen 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.

Results

Here, 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.

Conclusions

The 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.

People who undergo limb amputation can have issues with controlling movement and perception of residual limbs. This, in turn, can impact the success of neuroprosthetic strategies, which use signals from the body to control a prosthetic limb. Here, we wanted to understand how sensory signals within the muscle help to preserve movement and limb perception following amputation. We used ultrasound imaging and other methods to measure muscle activity and limb perception in fourteen people who have undergone lower limb amputations. We show that the level at which the relationship between pairs of related muscles is preserved is associated with more natural control of limb movement after amputation. Developing surgical techniques that preserve this relationship may help people living with amputations to naturally perceive and control their residual limbs, and ultimately may improve controllability of assistive prosthetic devices.

Song et al. study the relationship between agonist-antagonist muscle strain (AMS) and motor control and perception in lower limb amputees, with some receiving a myoneural interface intervention. The authors report that the degree of AMS within the residual limb is associated with preserved motor control and perception.

Primary Targeted Muscle Reinnervation after Below Knee Amputation is Not Associated with An Increased Risk of Major or Minor Surgical Complications: A Multi-Institutional, Propensity Score-Matched Analysis

BACKGROUND

Targeted muscle reinnervation (TMR) has emerged as a technique to reduce neuroma and phantom limb pain after below knee amputation (BKA); however, the incidence of post-operative complications remains unknown. This multi-institutional study assessed the risk of post-operative complications among patients who underwent TMR at the time of BKA (BKA+TMR).

STUDY DESIGN

Patients who underwent BKA+TMR were propensity score-matched 1:3 to patients who underwent BKA only. Study outcomes included the incidence of major or minor complications within 60 days. Regression models were utilized to estimate the relative risk (RR) of major and minor complications.

RESULTS

Overall, 96 patients were matched including 31 BKA+TMR and 65 BKA only. In the matched sample, a higher incidence of major complications (29% vs. 24.6%), readmission (25.8% vs. 18.5%) and reoperation (19.4% vs. 10.8%) was seen after BKA+TMR compared to BKA only. Furthermore, patients who underwent BKA+TMR displayed a higher incidence of minor complications (25.8% versus 20.0%), blood transfusion (22.6% vs. 18.5%), wound healing complications (45.2% vs. 33.8%), and longer operative time (mean [standard deviation] 188.5 [63.6] vs. 88 [28.2] minutes). However, there was no statistically significant difference in the risk of major (RR:1.20, 90% confidence interval (CI):0.68, 2.11) or minor (RR:1.21, 90% CI:0.61, 2.41) complications between the two cohorts.

CONCLUSION

Despite an increased incidence of post-operative complications, undergoing BKA+TMR does not confer a statistically significant increased risk of major or minor complications. Future studies are needed to delineate patient selection criteria when assessing the suitability of TMR at the time of major limb amputation.

Physiological and Neural Changes with Rehabilitation Training in a 53-Year Amputee: A Case Study

Many people who received amputation wear sEMG prostheses to assist in their daily lives. How these prostheses promote muscle growth and change neural activity remains elusive. We recruited a subject who had his left hand amputated for over 53 years to participate in a six-week rehabilitation training using an sEMG prosthesis. We tracked the muscle growth of his left forearm and changes in neural activity over six weeks. The subject showed an increase in fast muscle fiber in his left forearm during the training period. In an analysis of complex networks of neural activity, we observed that the α-band network decreased in efficiency but increased in its capability to integrate information. This could be due to an expansion of the network to accommodate new movements enabled by rehabilitation training. Differently, we found that in the β-band network, a band frequency related to motor functions, the efficiency of the network initially decreased but started to increase after approximately three weeks. The ability to integrate network information showed an opposite trend compared with its efficiency. rMT values, a measure that negatively correlates with cortical excitability, showed a sharp decrease in the first three weeks, suggesting an increase in cortical excitability. In the last three weeks, there was little to no change. These data indicate that rehabilitation training promoted fast muscle fiber growth and introduced neural activity changes in the subject during the first three weeks of training. Our study gave insights into how rehabilitation training with an sEMG prosthesis could lead to physiological and neural changes in amputees.

Defect Coverage after Forequarter Amputation—A Systematic Review Assessing Different Surgical Approaches

Autologous fillet flaps are a common reconstructive option for large defects after forequarter amputation (FQA) due to advanced local malignancy or trauma. The inclusion of osseous structures into these has several advantages. This article therefore systematically reviews reconstructive options after FQA, using osteomusculocutaneous fillet flaps, with emphasis on personalized surgical technique and outcome. Additionally, we report on a case with an alternative surgical technique, which included targeted muscle reinnervation (TMR) of the flap. Our literature search was conducted in the PubMed and Cochrane databases. Studies that were identified were thoroughly scrutinized with regard to relevance, resulting in the inclusion of four studies (10 cases). FQA was predominantly a consequence of local malignancy. For vascular supply, the brachial artery was predominantly anastomosed to the subclavian artery and the brachial or cephalic vein to the subclavian or external jugular vein. Furthermore, we report on a case of a large osteosarcoma of the humerus. Extended FQA required the use of the forearm for defect coverage and shoulder contour reconstruction. Moreover, we performed TMR. Follow-up showed a satisfactory result and no phantom limb pain. In case of the need for free flap reconstruction after FQA, this review demonstrates the safety and advantage of osteomusculocutaneous fillet flaps. If the inclusion of the elbow joint into the flap is not possible, we recommend the use of the forearm, as described. Additionally, we advocate for the additional implementation of TMR, as it can be performed quickly and is likely to reduce phantom limb and neuroma pain.

Total Talar and Navicular Extrusions: A Case Report

CASE

A 15-year-old adolescent boy sustained both talar and navicular extrusions after a dirt-bike accident. The talus and navicular were discarded during initial debridement because of contamination. Given extensive soft-tissue injury and bone loss, the patient's family opted for transtibial amputation, as described by Ertl, over limb salvage. Simultaneous osteomyoplastic reconstruction and acute targeted muscle reinnervation were performed.

CONCLUSION

Transtibial amputation is a viable treatment option for total talar and navicular extrusions, particularly if an optimal functional outcome is unachievable with limb salvage. Simultaneous osteomyoplastic reconstruction and acute targeted muscle reinnervation can potentially decrease neuroma formation and phantom limb pain.

"The Feasibility of Targeted Muscle Reinnervation for the Management of Morton's Neuroma"

BACKGROUND

Despite multiple surgical modalities available for the management of Morton's neuroma, complications remain common. Targeted muscle reinnervation (TMR) has yet to be explored as an option for the prevention of recurrence of Morton's neuroma. The purpose of the present investigation was to determine the consistency of the relevant foot neurovascular and muscle anatomy and to demonstrate the feasibility of TMR as an option for Morton's neuroma.

METHODS

The anatomy of 5 fresh-tissue donor cadaver feet was studied, including the course and location of the medial and lateral plantar nerves (MPNs and LPNs), motor branches to abductor hallucis (AH) and flexor digitorum brevis (FDB), as well as the course of sensory plantar digital nerves. Measurements for the locations of the muscular and sensory branches were taken relative to landmarks including the navicular tuberosity (NT), AH, FDB, and the third metatarsophalangeal joint (third MTPJ).

RESULTS

The mean number of nerve branches to FDB identified was 2. These branch points occurred at an average of 8.6 cm down the MPN or LPN, 9.0 cm from the third MTPJ, 3.0 cm distal to AH distal edge, and 4.8 cm from the NT. The mean number of nerves to AH was 2.2. These branch points occurred at an average of 6.3 cm down the MPN, 11.9 cm from the third MTPJ, 0.8 cm from the AH distal edge, and 3.8 cm from the NT.

CONCLUSIONS

Recurrent interdigital neuroma, painful scar, and neuropathic pain are common complications of operative management for Morton's neuroma. Targeted muscle reinnervation is a technique that has demonstrated efficacy for the prevention and treatment of neuroma, neuropathic pain, and phantom limb pain in amputees. Herein, we have described the neuromuscular anatomy for the application of TMR for the management of Morton's neuroma. Target muscles, including the AH and FDB, have consistent innervation patterns in the foot, and consequently, TMR represents a viable option to consider for the management of recalcitrant Morton's neuroma.

LEVELS OF EVIDENCE

V.

Indications and outcomes of palliative major amputation in patients with metastatic cancer

BACKGROUND

Patients with stage IV cancer often experience diminished quality of life and pain. Although palliative amputation (PA) can reduce pain, it is infrequently performed because of the morbidity associated with amputation and the limited life expectancy in this population. Here, we describe the indications for PA in patients with stage IV carcinoma or sarcoma and discuss their clinical courses and outcomes. We hypothesized that PA would be associated with reduced pain and improved quality of life in these patients.

METHODS

We retrospectively reviewed medical records of all patients who underwent major amputation (proximal to the ankle or wrist) for metastatic sarcoma or carcinoma from January 1995 to April 2021. We excluded patients who underwent amputation for indications other than palliation. Cox proportional hazards regression analysis was used to determine factors associated with survival after PA.

RESULTS

Twenty-six patients underwent PA (11 for carcinoma, 15 for sarcoma). The most common indications for PA were pain (all patients) and fungating tumor (16 patients). PA was the initial surgery in 7 patients. Forequarter amputations were the most common procedure (6 patients). All patients reported reduced pain after PA, with the mean (±standard deviation) visual analog pain score (on a 10-point scale) decreasing from 5.7 ± 2.9 preoperatively to 0.43 ± 1.3 postoperatively (p < 0.001). The mean preoperative ECOG score was 1.9 ± 0.2 compared with 1.3 ± 0.1 postoperatively (p < 0.001). Fourteen patients were fitted for prostheses (6 upper extremity, 8 lower extremity). Two patients had local recurrence, both within 6 months after PA. The mean survival time after PA was 13 ± 12 months, and mean follow-up was 28 ± 29 months. Mean survival time after PA was not significantly different between patients with sarcoma (11 ± 11 months) versus carcinoma (15 ± 14 months) (p = 0.51). Adjuvant chemotherapy was positively associated with survival; no other factors were associated with survival.

CONCLUSIONS

PA was associated with significantly reduced pain in all patients with stage IV cancer. PA should be considered for those with intractable pain, fungating tumors, or symptoms that diminish quality of life.

LEVEL OF EVIDENCE

Level III.

How Common Are Chronic Residual Limb Pain, Phantom Pain, and Back Pain More Than 20 Years After Lower Limb Amputation for Malignant Tumors?

BACKGROUND

After major lower limb amputation, persistent pain is common, with up to 85% of patients reporting recurring phantom or residual-limb pain. Although pain management is an important factor of quality of life in patients with lower limb amputations, there are few long-term data regarding the frequency of persistent pain and how it impacts prosthesis use.

QUESTIONS/PURPOSES

(1) How prevalent are different types of pain at long-term follow-up after amputation for malignant tumors? (2) What association do different pain types have with daily prosthesis use?

METHODS

Between 1961 and 1995, 124 major amputations for malignant tumors were performed at one center in Austria in patients (1) who spoke German and (2) whose surgical date resulted in the possibility of a minimum follow-up time of 20 years at the time of this survey; those patients were considered potentially eligible for this retrospective study. The indications for major amputation were to achieve local tumor control in limbs that the surgeon deemed unsalvageable without amputation. Of those 124 patients, 71% (88) had died, 9% (11) could not be reached, and 3% (4) declined to participate. Thus, 58% (21 of 36) of those living at the time of this study and who underwent lower limb amputation between 1961 and 1993 with a median (range) follow-up duration of 41 years (23 to 55) completed a standardized questionnaire, including an assessment of pain and daily prosthesis use during the year before the survey. Phantom pain, residual limb pain, and back pain were each further subclassified into pain frequency, intensity, and restrictions in activities of daily living (ADL) due to the specific pain form and rated on a 5- (pain frequency) and 10-point (pain intensity, restrictions in ADL) numerical rating scale. Before multivariate regression analysis, daily prosthesis use was correlated with pain parameters using Spearman correlation testing.

RESULTS

Seventeen of 21 patients reported phantom limb and back pain, and 15 patients reported residual limb pain in the past year. Median (range) phantom pain intensity was 7 (1 to 10) points, median residual limb pain intensity was 4 (1 to 9) points, and median back pain intensity was 5 (1 to 10) points. After controlling for relevant confounding variables such as age at amputation, age at survey, and stump length, we found that less intense residual limb pain (defined on a 10-point scale with 1 representing no pain at all and 10 representing extremely strong pain [95% CI 0.3 to 1.0]; r = 0.8; p = 0.003) was associated with greater daily prosthesis use. Higher amputation levels showed a decreased daily prosthesis use compared with patients with lower amputation levels (defined as transfemoral amputation versus knee disarticulation versus transtibial amputation [95% CI 0.3 to 5.1]; r = 0.5; p = 0.03).

CONCLUSION

Decades after surgery, many patients with lower limb amputations experience pain that restricts them in terms of ADLs and decreases their daily prosthesis use. This information supports the need for regular residual limb inspections and careful prosthesis fitting even at long-term follow-up, as effective prosthesis fitting is a modifiable cause of residual limb pain. Future studies evaluating long-term treatment effects of pain relief surgery and therapeutic alternatives to conservative pain treatments should be performed, as these approaches may help alleviate pain in patients with refractory postamputation pain.

LEVEL OF EVIDENCE

Level IV, therapeutic study.

Targeted Muscle Reinnervation Improves Pain and Ambulation Outcomes in Highly Comorbid Amputees

BACKGROUND

Approximately 200,000 people undergo a lower extremity amputation each year. Following amputation, patients suffer from chronic pain, inability to ambulate, and high mortality rates. Targeted muscle reinnervation is a nerve transfer procedure that redirects transected sensory and mixed nerves into motor nerves to treat neuroma and phantom limb pain. This study evaluates outcomes with prophylactic targeted muscle reinnervation at the time of below-knee amputation.

METHODS

This is a cohort study comparing 100 patients undergoing below-knee amputation with primary targeted muscle reinnervation and 100 patients undergoing below-knee amputation with standard traction neurectomy and muscle implantation. Outcome metrics included the presence of residual and phantom limb pain, pain severity, opioid use, ambulation ability, and mortality rates.

RESULTS

The targeted muscle reinnervation group was on average 60 years old with a body mass index of 29 kg/m2. Eighty-four percent had diabetes, 55 percent had peripheral vascular disease, and 43 percent had end-stage renal disease. Average follow-up was 9.6 months for the targeted muscle reinnervation group and 18.5 months for the nontargeted muscle reinnervation group. Seventy-one percent of targeted muscle reinnervation patients were pain free, compared with 36 percent (p < 0.01). Fourteen percent of targeted muscle reinnervation patients had residual limb pain, compared with 57 percent (p < 0.01). Nineteen percent of targeted muscle reinnervation patients had phantom limb pain, compared with 47 percent (p < 0.01). Six percent of targeted muscle reinnervation patients were on opioids, compared with 26 percent (p < 0.01); and 90.9 percent of targeted muscle reinnervation patients were ambulatory, compared with 70.5 percent (p < 0.01).

CONCLUSION

Targeted muscle reinnervation reduces pain and improves ambulation in patients undergoing below-knee amputation, which may be critical in improving morbidity and mortality rates in this comorbid patient population.

CLINICAL QUESTION/LEVEL OF EVIDENCE

Therapeutic, III.

The Need to Work Arm in Arm: Calling for Collaboration in Delivering Neuroprosthetic Limb Replacements

Over the last few decades there has been a push to enhance the use of advanced prosthetics within the fields of biomedical engineering, neuroscience, and surgery. Through the development of peripheral neural interfaces and invasive electrodes, an individual's own nervous system can be used to control a prosthesis. With novel improvements in neural recording and signal decoding, this intimate communication has paved the way for bidirectional and intuitive control of prostheses. While various collaborations between engineers and surgeons have led to considerable success with motor control and pain management, it has been significantly more challenging to restore sensation. Many of the existing peripheral neural interfaces have demonstrated success in one of these modalities; however, none are currently able to fully restore limb function. Though this is in part due to the complexity of the human somatosensory system and stability of bioelectronics, the fragmentary and as-yet uncoordinated nature of the neuroprosthetic industry further complicates this advancement. In this review, we provide a comprehensive overview of the current field of neuroprosthetics and explore potential strategies to address its unique challenges. These include exploration of electrodes, surgical techniques, control methods, and prosthetic technology. Additionally, we propose a new approach to optimizing prosthetic limb function and facilitating clinical application by capitalizing on available resources. It is incumbent upon academia and industry to encourage collaboration and utilization of different peripheral neural interfaces in combination with each other to create versatile limbs that not only improve function but quality of life. Despite the rapidly evolving technology, if the field continues to work in divided "silos," we will delay achieving the critical, valuable outcome: creating a prosthetic limb that is right for the patient and positively affects their life.

Surgical prevention of terminal neuroma and phantom limb pain: a literature review

The incidence of extremity amputation is estimated at about 200,000 cases annually. Over 25% of patients suffer from terminal neuroma or phantom limb pain (TNPLP), resulting in pain, inability to wear a prosthetic device, and lost work. Once TNPLP develops, there is no definitive cure. Therefore, there has been an emerging focus on TNPLP prevention. We examined the current literature on TNPLP prevention in patients undergoing extremity amputation. A literature review was performed using Ovid Medline, Cochrane Collaboration Library, and Google Scholar to identify all original studies that addressed surgical prophylaxis against TNPLP. The search was conducted using both Medical Subject Headings and free-text using the terms “phantom limb pain,” “amputation neuroma,” and “surgical prevention of amputation neuroma.” Fifteen studies met the inclusion criteria, including six prospective trials, two comprehensive literature reviews, four retrospective chart reviews, and three case series/technique reviews. Five techniques were identified, and each was incorporated into a target-based classification system. A small but growing body of literature exists regarding the surgical prevention of TNPLP. Targeted muscle reinnervation (TMR), a form of physiologic target reassignment, has the greatest momentum in the academic surgical community, with multiple recent prospective studies demonstrating superior prevention of TNPLP. Neurorrhaphy and transposition with implantation are supported by less robust evidence, but merit future study as alternatives to TMR.

Improving the Selectivity of an Osseointegrated Neural Interface: Proof of Concept For Housing Sieve Electrode Arrays in the Medullary Canal of Long Bones

Sieve electrodes stand poised to deliver the selectivity required for driving advanced prosthetics but are considered inherently invasive and lack the stability required for a chronic solution. This proof of concept experiment investigates the potential for the housing and engagement of a sieve electrode within the medullary canal as part of an osseointegrated neural interface (ONI) for greater selectivity toward improving prosthetic control. The working hypotheses are that (A) the addition of a sieve interface to a cuff electrode housed within the medullary canal of the femur as part of an ONI would be capable of measuring efferent and afferent compound nerve action potentials (CNAPs) through a greater number of channels; (B) that signaling improves over time; and (C) that stimulation at this interface generates measurable cortical somatosensory evoked potentials through a greater number of channels. The modified ONI was tested in a rabbit (n = 1) amputation model over 12 weeks, comparing the sieve component to the cuff, and subsequently compared to historical data. Efferent CNAPs were successfully recorded from the sieve demonstrating physiological improvements in CNAPs between weeks 3 and 5, and somatosensory cortical responses recorded at 12 weeks postoperatively. This demonstrates that sieve electrodes can be housed and function within the medullary canal, demonstrated by improved nerve engagement and distinct cortical sensory feedback. This data presents the conceptual framework for housing more sophisticated sieve electrodes in bone as part of an ONI for improving selectivity with percutaneous connectivity toward improved prosthetic control.

Targeted Muscle Reinnervation to Expendable Motor Nerves for the Treatment of Refractory Symptomatic Neuromas in Nonamputees

Symptomatic neuromas can cause debilitating pain, significantly impairing patients’ quality of life. There are numerous medical and surgical options for management. Targeted muscle reinnervation (TMR) is a nerve transfer procedure that is now commonly used to prevent or treat symptomatic neuromas or phantom limb pain in amputees. There are a few reports in the current literature about performing TMR in the nonamputee, but no cohort studies to date that report pain outcomes. This study evaluates TMR to treat symptomatic neuromas in nonamputee patients. This is a retrospective cohort study of all patients with symptomatic neuromas treated with TMR over a 1-year period from January 1,2019, to January 1, 2020, at MedStar Georgetown University Hospital. The neuromas are excised to healthy nerve fascicles, and a redundant donor motor fascicle is selected for nerve transfer. Patients were asked in clinic or via telephone about their preoperative and postoperative pain, function, and quality of life, and postoperative clinic notes were reviewed for complications and motor deficits. Fifteen patients were included in this study. Patients had symptomatic neuromas involving the upper extremity, lower extremity, and trunk. Pain frequency decreased from 6.7 times per week to 3.9 (P < 0.01) and from 9.1 times per day to 5.1 (P < 0.01). Pain severity decreased from an average of 7.9/10 to 4.3/10 (P < 0.01). Overall physical function increased from 3.7/10 to 5.8/10 (P = 0.01), and overall quality of life increased from 4.9/10 to 7.0/10 (P < 0.01). No patients had demonstrable weakness of the motor function of the donor nerve. Targeted muscle reinnervation is a viable surgical option for the treatment of symptomatic neuromas, particularly in those patients who have previously failed prior neuroma excisions.

Restoring Form and Function to the Partial Hand Amputee: Prosthetic Options from the Fingertip to the Palm

Partial hand amputations are the most common upper extremity amputations and affect individuals across a spectrum of socioeconomic and geographic backgrounds. Prosthetic devices can provide straightforward solutions to the devastating aesthetic, functional, psychological, and social deficits caused by these injuries. However, because of the recent development of multiple partial hand prosthetic devices, many hand providers remain unaware of their applicability in practice. This article highlights the various classes of partial hand prostheses currently available, including passive functional, body-powered, and externally powered options. Familiarity with these partial hand prostheses will better enable providers to care for partial hand amputees.

Managing Neuroma and Phantom Limb Pain in Ontario: The Status of Targeted Muscle Reinnervation

Supplemental Digital Content is available in the text.

Background:

Painful neuromas (PN) and phantom limb pain (PLP) are common following amputation and are unreliably treated, which impacts quality of life. Targeted muscle reinnervation (TMR) is a microsurgical technique that repairs the severed proximal nerve end to a redundant motor nerve in the amputated stump. Evidence supports TMR as effective in treating PN and PLP; however, its adoption has been slow. This study aimed to characterize: (1) the populations experiencing post-amputation PN/PLP; (2) current trends in managing PN/PLP; and (3) attitudes toward routine use of TMR to manage PN/PLP.

Methods:

A cross-sectional survey was distributed to all orthopedic surgeons, plastic surgeons, and physiatrists practicing in Ontario, via publicly available emails and specialty associations. Data were collected on demographics, experience with amputation, managing post-amputation pain, and attitudes toward routine use of TMR.

Results:

Sixty-six of 698 eligible participants submitted complete surveys (9.5% response rate). Respondents had a greater experience with surgical management of PN (71% PN versus 10% PLP). However, surgery was considered a 3rd-line option for PN and not an option for PLP in 57% and 59% of respondents, respectively. Thirty participants (45%) were unaware of TMR as an option, and only 8 respondents have currently incorporated TMR into their practice. Many (76%) would be willing to incorporate TMR into their practice as either an immediate or delayed surgical technique.

Conclusions:

Despite its promise in managing post-amputation pain, awareness of TMR as a surgical option is generally poor. Several barriers to the widespread adoption of this technique are defined.

Experimental Basis for Creating an Osseointegrated Neural Interface for Prosthetic Control: A Pilot Study in Rabbits

INTRODUCTION

While debate persists over how to best prevent or treat amputation neuromas, the more pressing question of how to best marry residual nerves to state-of-the-art robotic prostheses for naturalistic control of a replacement limb has come to the fore. One potential solution involves the transposition of terminal nerve ends into the medullary canal of long bones, creating the neural interface within the bone. Nerve transposition into bone is a long-practiced, clinically relevant treatment for painful neuromas. Despite neuropathic pain relief, the physiological capacity of transposed nerves to conduct motor and sensory signals required for prosthesis control remains unknown. This pilot study addresses the hypotheses that (1) bone provides stability to transposed nerves and (2) nerves transposed into bone remain physiologically active, as they relate to the creation of an osseointegrated neural interface.

METHODS

New Zealand white rabbits received transfemoral amputation, with the sciatic nerve transposed into the femur.

RESULTS

Morphological examination demonstrates that nerves remain stable within the medullary canal, while compound nerve action potentials evoked by electrical stimulation of the residual nerve within the bone could be achieved at 12 weeks (p < 0.0005).

CONCLUSION

Transposed nerves retain a degree of physiological function suitable for creating an osseointegrated neural interface.

Osseointegration of Extremity Prostheses: A Primer for the Plastic Surgeon

Interest in amputation surgery has increased in conjunction with rising public awareness about amputee care. To date, plastic surgeons have impacted the quality of life and functional potential of amputees through novel strategies for sensory feedback and prosthesis control and various techniques for neuroma treatment and prevention. Osseointegration, which involves the direct skeletal attachment of a prosthesis to bone, has the ability to further maximize amputee function. There exists a critical role for plastic surgeons to help optimize techniques for extremity osseointegration through improved wound care and soft-tissue management. An overview of current osseointegrated prostheses and their associated limitations, and potential avenues through which plastic surgeons can help mitigate these challenges, are discussed in this article.

Technological Advances in Prosthesis Design and Rehabilitation Following Upper Extremity Limb Loss

PURPOSE OF REVIEW

The complexity of the human extremity, particularly the upper extremity and the hand, allows us to interact with the world. Prosthetists have struggled to recreate the intuitive motor control, light touch sensation, and proprioception of the innate limb in a manner that reflects the complexity of its native form and function. Nevertheless, recent advances in prosthesis technology, surgical innovations, and enhanced rehabilitation appear promising for patients with limb loss who hope to return to their pre-injury level of function. The purpose of this review is to illustrate recent technological advances that are moving us one step closer to the goal of multi-functional, self-identifiable, durable, and intuitive prostheses.

RECENT FINDINGS

Surgical advances such as targeted muscle reinnervation, regenerative peripheral nerve interfaces, agonist-antagonist myoneural interfaces, and targeted sensory reinnervation; development of technology designed to restore sensation, such as implanted sensors and haptic devices; and evolution of osseointegrated (bone-anchored) prostheses show great promise. Augmented and virtual reality platforms have the potential to enhance prosthesis design, pre-prosthetic training, incorporation, and use. Emerging technologies move surgeons, rehabilitation physicians, therapists, and prosthetists closer to the goal of creating highly functional prostheses with elevated sensory and motor control. Collaboration between medical teams, scientists, and industry stakeholders will be required to keep pace with patients who require durable, high-functioning prostheses.

Soft Tissue Contouring at the Time of Osseointegrated Implant Reconstruction for Lower Extremity Amputation

INTRODUCTION

Patients with lower extremity amputations using a classic socket prosthesis face many challenges related to the socket-limb interface. The adaptation of osseointegration has allowed for the attachment of a prosthesis directly to bone, eliminating this interface and providing mechanical benefits. Contrary to the socket prosthesis, the osseointegrated prosthesis requires reducing and minimizing the soft tissue envelope. Studies have shown that patients who have undergone placement of these implants have high rates of reoperation for soft tissue redundancy. The purpose of our study was to evaluate complication rates and need for revisional surgery using our technique of soft tissue closure around the prosthesis at the time of implant placement.

METHODS

An institutional review board-approved, retrospective chart review was performed on all patients who underwent implantation of an osseointegrated prosthesis for lower extremity amputation with concomitant plastic surgery closure at our institution during a 2-year period from June 2017 to June 2019. Patient demographics, health status descriptors, operative data, length of admission, and rates of postoperative complications were gathered from the electronic medical record and coded into a HIPAA-compliant database. Specific outcomes tracked included minor and major infection, osteomyelitis, implant failure, hematoma, seroma, delayed wound healing, and rates of reoperation and readmission.

RESULTS

There were a total of 14 patients who underwent osseointegrated implant placement with concomitant plastic surgical coverage of the prosthesis during the study period. The average patient age was 50 years (range, 26-70 years), and average body mass index was 32.2 kg/m (range, 19.7-44.8 kg/m). Average follow-up time was 28 weeks (range, 10-73 weeks). There were 2 cases of local infection resolved with a course of oral antibiotics. There were no instances of infection requiring procedural intervention or hospital admission, nor any cases of osteomyelitis. Two patients required outpatient surgery for exchange of implant abutment, one required revision of a prosthesis for hardware loosening, and one required targeted muscle reinnervation of a sciatic nerve neuroma. There were no patients who required revisional surgery for soft tissue redundancy and no cases of delayed wound healing.

CONCLUSIONS

Adequate planning of incisions and soft tissue contouring is important in the care of osseointegrated patients. Plastic surgery involvement can decrease soft tissue complications and lead to improved patient outcomes.

Interfaces with the peripheral nervous system for the control of a neuroprosthetic limb: a review

The field of prosthetics has been evolving and advancing over the past decade, as patients with missing extremities are expecting to control their prostheses in as normal a way as possible. Scientists have attempted to satisfy this expectation by designing a connection between the nervous system of the patient and the prosthetic limb, creating the field of neuroprosthetics. In this paper, we broadly review the techniques used to bridge the patient's peripheral nervous system to a prosthetic limb. First, we describe the electrical methods including myoelectric systems, surgical innovations and the role of nerve electrodes. We then describe non-electrical methods used alone or in combination with electrical methods. Design concerns from an engineering point of view are explored, and novel improvements to obtain a more stable interface are described. Finally, a critique of the methods with respect to their long-term impacts is provided. In this review, nerve electrodes are found to be one of the most promising interfaces in the future for intuitive user control. Clinical trials with larger patient populations, and for longer periods of time for certain interfaces, will help to evaluate the clinical application of nerve electrodes.

Methodology for creating a chronic osseointegrated neural interface for prosthetic control in rabbits

BACKGROUND

Chronic stability and high degrees of selectivity are both essential but somewhat juxtaposed components for creating an implantable bi-directional PNI capable of controlling of a prosthetic limb. While the more invasive implantable electrode arrays provide greater specificity, they are less stable over time due to compliance mismatch with the dynamic soft tissue environment in which the interface is created.

NEW METHOD

This paper takes the surgical approach of transposing nerves into bone to create neural interface within the medullary canal of long bones, an osseointegrated neural interface, to provide greater stability for implantable electrodes. In this context, we describe the surgical model for transfemoral amputation with transposition of the sciatic nerve into the medullary canal in rabbits. We investigate the capacity to create a neural interface within the medullary canal histolomorphologically. In a separate proof of concept experiment, we quantify the chronic physiological capacity of transposed nerves to conduct compound nerve action potentials evoked via an Osseointegrated Neural Interface.

COMPARISON WITH EXISTING METHOD(S)

The rabbit serves as an important animal model for both amputation neuroma and osseointegration research, but is underutilized for the exploration neural interfacing in an amputation setting.

RESULTS

Our findings demonstrate that transposed nerves remain stable over 12 weeks. Creating a neural interface within the medullary canal is possible and does not impede nerve regeneration or physiological capacity.

CONCLUSIONS

This article represents the first evidence that an Osseointegrated Neural Interface can be surgically created, capable of chronic stimulation/recording from amputated nerves required for future prosthetic control.

Myoelectric Control for Upper Limb Prostheses

State-of-the-art high-end prostheses are electro-mechanically able to provide a great variety of movements. Nevertheless, in order to functionally replace a human limb, it is essential that each movement is properly controlled. This is the goal of prosthesis control, which has become a growing research field in the last decades, with the ultimate goal of reproducing biological limb control. Therefore, exploration and development of prosthesis control are crucial to improve many aspects of an amputee’s life. Nowadays, a large divergence between academia and industry has become evident in commercial systems. Although several studies propose more natural control systems with promising results, basic one degree of freedom (DoF), a control switching system is the most widely used option in industry because of simplicity, robustness and inertia. A few classification controlled prostheses have emerged in the last years but they are still a low percentage of the used ones. One of the factors that generate this situation is the lack of robustness of more advanced control algorithms in daily life activities outside of laboratory conditions. Because of this, research has shifted towards more functional prosthesis control. This work reviews the most recent literature in upper limb prosthetic control. It covers commonly used variants of possible biological inputs, its processing and translation to actual control, mostly focusing on electromyograms as well as the problems it will have to overcome in near future.

Targeted muscle reinnervation in oncologic amputees: Early experience of a novel institutional protocol

BACKGROUND

We describe a multidisciplinary approach for comprehensive care of amputees with concurrent targeted muscle reinnervation (TMR) at the time of amputation.

METHODS

Our TMR cohort was compared to a cross-sectional sample of unselected oncologic amputees not treated at our institution (N = 58). Patient-Reported Outcomes Measurement Information System (NRS, PROMIS) were used to assess postamputation pain.

RESULTS

Thirty-one patients underwent amputation with concurrent TMR during the study; 27 patients completed pain surveys; 15 had greater than 1 year follow-up (mean follow-up 14.7 months). Neuroma symptoms occurred significantly less frequently and with less intensity among the TMR cohort. Mean differences for PROMIS pain intensity, behavior, and interference for phantom limb pain (PLP) were 5.855 (95%CI 1.159-10.55; P = .015), 5.896 (95%CI 0.492-11.30; P = .033), and 7.435 (95%CI 1.797-13.07; P = .011) respectively, with lower scores for TMR cohort. For residual limb pain, PROMIS pain intensity, behavior, and interference mean differences were 5.477 (95%CI 0.528-10.42; P = .031), 6.195 (95%CI 0.705-11.69; P = .028), and 6.816 (95%CI 1.438-12.2; P = .014), respectively. Fifty-six percent took opioids before amputation compared to 22% at 1 year postoperatively.

CONCLUSIONS

Multidisciplinary care of amputees including concurrent amputation and TMR, multimodal postoperative pain management, amputee-centered rehabilitation, and peer support demonstrates reduced incidence and severity of neuroma and PLP.