Targeted Muscle Reinnervation in the Upper Extremity Amputee: A Technical Roadmap

Phantom Limb Pain Management

With an estimated 2 million major limb amputees and projections reaching 3.6 million by 2050, the increasing prevalence of limb loss in the United States underscores the importance of addressing complications associated with limb loss. Phantom limb pain (PLP) is a common and often chronic condition affecting 40% to 80% of amputees. The heterogeneous pathology of PLP encompasses cortical, spinal, and peripheral mechanisms that present a challenge to providing effective treatments. The spectrum of available treatments spans pharmacologic interventions, noninvasive modalities like mirror therapy, and surgical techniques. A review of the current body of evidence on the treatment of PLP favors novel methods of surgical management. Nonetheless, a majority of literature pushes for the evaluation of other methods of ameliorating PLP as imperative to offering patient-centered options that address the myriad of etiologies that contribute to this pathology. More extensive research, especially randomized controlled trials, is needed to establish the long-term efficacy of interventions, compare the impact of different treatments, and identify which modalities are most effective in various patient populations.

Targeted muscle reinnervation in upper extremity amputations

PURPOSE

Targeted muscle reinnervation (TMR) is a relatively recent surgical innovation that involves the coaptation of major peripheral nerves to a recipient motor branch that innervates an expendable muscle target. The original indication for TMR was augmentation and optimization of myoelectric signals in the amputated limb for use of myoelectric prosthetics. Incidentally, surgeons and patients discovered that the technique also could treat and prevent phantom and residual limb pain. TMR is performed at the time of amputation or delayed any time after the amputation, and TMR can also be performed at any level of amputation. In the upper extremity, studies have detailed the various techniques and coaptations possible at each amputation level to create intuitive myoelectric signals and treat neurogenic pain. Treatment of peripheral nerves in the amputee with TMR should be a consideration for all patients with major upper extremity amputations, especially at large institutions able to support multidisciplinary limb salvage teams. This review article summarizes the current literature and authors' techniques and recommendations surrounding TMR in the upper extremity amputee including techniques relevant to each level of upper extremity amputation.

Managing Major Peripheral Nerves in Forearm-Level Amputations With TMR and RPNI: What's the Best Recipe?

BACKGROUND

Targeted muscle reinnervation (TMR) and regenerative peripheral nerve interface (RPNI) prevent symptomatic neuroma formation in amputees. Forearm-level amputations present multiple muscular targets, making it challenging to determine the ideal treatment. The purpose of this study was to evaluate the best TMR targets, role of RPNI, and appropriate patient-selection criteria in forearm-level amputations. We hypothesized that deep and distal TMR targets would best prevent symptomatic neuromas, RPNI would prove a success adjunct, and patients with poorly controlled diabetes would not develop symptomatic neuromas regardless of nerve management.

METHODS

We retrospectively identified forearm-level amputations performed between 2017 and 2022. Patients with TMR by outside providers, follow-up <6 months, or insufficient documentation were excluded. Demographics, surgical nerve management, and postoperative complications were collected. The primary outcome was development of a painful neuroma determined by the Eberlin criteria. Patients undergoing TMR were divided a priori into two groups, superficial and proximal versus deep and distal TMR targets, and were compared.

RESULTS

Thirty-nine patients met inclusion criteria, and 16 developed a symptomatic neuroma. No patients with a deep or distal TMR target developed a symptomatic neuroma. One nerve out of 12 treated with RPNI developed a symptomatic neuroma. No patient with poorly controlled diabetes developed a symptomatic neuroma, despite no advanced nerve management.

CONCLUSIONS

In a case series of forearm amputations, deep and distal TMR targets prevented symptomatic neuroma formation more than superficial and proximal targets. Regenerative peripheral nerve interface is a useful adjunct for neuroma control, especially for the radial sensory nerve. Patients with poorly controlled diabetes may not require advanced nerve management.

LEVEL OF EVIDENCE

Level IV retrospective case series.

Surgical treatment of painful neuroma in amputated and non-amputated patients: does the level of neurotomy affect clinical outcomes?

PURPOSE

To compare the outcomes of distal neurotomy (DN) versus proximal neurotomy (PN) for the surgical management of painful neuromas in amputees and non-amputees, whether used in passive or active treatment.

METHODS

A retrospective study was conducted on patients who underwent surgery for painful traumatic neuromas between 2019 and 2022. DN with neuroma excision was performed at the level of the injury or amputation. PN was performed using a separate proximal approach without neuroma excision. Outcomes included a Numerical Rating Scale (NRS) score and Patient-Reported Outcomes Measurement Information System (PROMIS) scores, as well as patients' subjective assessments.

RESULTS

A total of 33 patients were included: 17 amputees and 16 non-amputees. They totalized 43 neuromas treated by DN in 21 cases and PN in 22 cases. At the median follow-up time of 13 months, there were significant decreases in all NRS and PROMIS scores in the whole series. The decrease in limb pain scores was not significantly different between groups, except for the decrease in pain interference and patient satisfaction which were higher in the DN group. Sub-group analyses found the same significant differences in amputees. Targeted muscle reinnervation (TMR) was associated with a higher decrease in PROMIS scores.

CONCLUSION

DN seemed to give better results in amputees but there were confusing factors related to associated lesions. In other situations, the non-inferiority of PN was demonstrated. PN could be of interest for treating neuromas of superficial sensory nerves, for avoiding direct revision of a well-fitted stump and in conjunction with TMR.

Targeted muscle reinnervation in bionic upper limb reconstruction: current status and future directions

Selective nerve transfers are used in the setting of upper limb amputation to improve myoelectric prosthesis control. This surgical concept is referred to as targeted muscle reinnervation (TMR) and describes the rerouting of the major nerves of the arm onto the motor branches of the residual limb musculature. Aside from providing additional myosignals for prosthetic control, TMR can treat and prevent neuroma pain and possibly also phantom limb pain. This article reviews the history and current applications of TMR in upper limb amputation, with a focus on practical considerations. It further explores and identifies technological innovations to improve the man-machine interface in amputation care, particularly regarding implantable interfaces, such as muscle electrodes and osseointegration. Finally, future clinical directions and possible scientific avenues in this field are presented and critically discussed.

Building a Multidisciplinary Clinic Dedicated to Upper-Extremity Limb Loss

Complete care of the patient with upper limb loss mandates a long-term, multifaceted approach. Increased functionality and quality of life require collaborative efforts between the patient's surgeon, prosthetist, hand therapists, mental health professionals, and peers. An individual surgeon may find that initiating and maintaining a practice offering total integrated treatment for upper-extremity amputees is a formidable task, but with specific, actionable recommendations, the process can be demystified. The upper-extremity surgeon must be facile with operative techniques such as targeted muscle reinnervation (TMR), regenerative peripheral nerve interface (RPNI), and soft tissue reconstruction and focus on team recruitment strategy and promotion of the clinic within the community. Consistent communication and team decision-making shape each patient's preoperative and postoperative course. We aim to relay effective interventions at each step of recovery from each clinic member and describe clinic workflow designed to reinforce holistic care. We present a blueprint for creating a functional and comprehensive multidisciplinary center for patients with upper-extremity limb loss for those providers interested in providing care, but who are missing the logistical roadmap for how to do so.

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.

TMR for Peripheral Sensory Nerve Neuroma around the Wrist Utilizing the Distal Anterior Interosseous Nerve

Injury to the peripheral sensory nerves of the hand and wrist is common and can lead to debilitating neuromas and significantly impair patients' quality of life. Target-muscle reinnervation (TMR) is a novel method for treating neuromas that can result in significant clinical improvement. However, TMR for the peripheral sensory nerves in the hand and wrist is restricted by the limited options for motor branches. The adaptability of the anterior interosseous nerve (AIN) as a target for TMR treating peripheral sensory neuroma has not been thoroughly investigated or implemented therapeutically. This study aimed to evaluate the use of AIN as a viable recipient of TMR for treating peripheral sensory neuromas around the wrist. In this retrospective study, eight patients were included over 18 months from June 2021 to January 2023 at Hamad Medical Corporation. The average follow-up time after TMR was 13 months. The peripheral sensory nerves involved were the radial sensory nerve in five cases, the palmar cutaneous branch of the median nerve in one case, and the median nerve in one case. The preoperative average VAS pain score was 7 of 10 compared with the postoperative pain score of 2 of 10. In conclusion, the AIN can be used as a first-choice motor target for all peripheral sensory neuromas around the wrist for the following reasons: first, it can be reached by the peripheral sensory nerves around the wrist; second, the pronator quadratus muscle is expandable; and third, the AIN can be taken with a long proximal tail for flexible coaptation with the peripheral sensory nerves.

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.

Regenerative Peripheral Nerve Interface Surgery: Anatomic and Technical Guide

Regenerative peripheral nerve interface (RPNI) surgery has been demonstrated to be an effective tool as an interface for neuroprosthetics. Additionally, it has been shown to be a reproducible and reliable strategy for the active treatment and for prevention of neuromas. The purpose of this article is to provide a comprehensive review of RPNI surgery to demonstrate its simplicity and empower reconstructive surgeons to add this to their armamentarium. This article discusses the basic science of neuroma formation and prevention, as well as the theory of RPNI. An anatomic review and discussion of surgical technique for each level of amputation and considerations for other etiologies of traumatic neuromas are included. Lastly, the authors discuss the future of RPNI surgery and compare this with other active techniques for the treatment of neuromas.

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.

Neuroma Treatment With the Acellular Nerve Allograft Reconstruction Technique

Treatment of a painful neuroma is a challenging problem for both the patient and the providers. Current surgical treatment options typically include excision of the neuroma and stump relation. However, with both treatment options, patients have high rates of persistent pain and rates of neuroma recurrence. We describe two patients with neuromas treated with our acellular nerve allograft reconstruction technique. This technique involves the excision of the neuroma and bridging the proximal nerve end to the surrounding tissue with an acellular nerve allograft. Both patients had immediate resolution of their neuropathic pain that was maintained at their final follow-up. Acellular nerve allograft reconstruction is a promising treatment option for the treatment of painful neuromas.

A Consensus Approach for Targeted Muscle Reinnervation in Amputees

Amputations have been performed with few modifications since the dawn of surgery. Blood vessels are ligated, bones are shortened, and nerves are cut. In a percentage of people, this can result in severe neuropathic, residual limb, and phantom limb pain. Targeted muscle reinnervation is a surgical procedure initially conceived to optimize function for myoelectric prostheses in amputees. Recently, it has been adopted more widely by surgeons for the prevention and treatment of neuropathic pain. Perhaps as a function of its relatively recent development, many authors perform this operation differently, and there has been no overall agreement regarding the principles, indications, technical specifics, and postoperative management guidelines. This article is written as a consensus statement by surgeons focused on the treatment of neuropathic pain and those with extensive experience performing targeted muscle reinnervation. It is designed to serve as a roadmap and template for extremity surgeons to consider when performing targeted muscle reinnervation.

Soft Tissue Management of Partial Hand Amputation

Conventional teaching in the management of partial hand amputations prioritizes residual limb length, often through local, regional, or distant flaps. While multiple options exist to provide durable soft tissue coverage, only a few flaps are thin and pliable enough to match that of the dorsal hand skin. Despite debulking, excessive soft tissues from previous flap reconstructions can interfere with residual limb function, prosthesis fit, and surface electrode recording for myoelectric prostheses. With rapid advances in prosthetic technology and nerve transfer techniques, patients can achieve very high levels of function following prosthetic rehabilitation that rival, or even outpace, traditional soft tissue reconstruction. Therefore, our reconstruction algorithm for partial hand amputations has evolved to the thinnest coverage possible, providing adequate durability. This evolution has provided our patients with faster and more secure prosthesis fitting with better surface electrode detection, enabling earlier and improved use of simple and advanced partial hand prostheses.

Radial Nerve Fascicular Transfer Preserving Long Head through Anterior Incision for Transhumeral Targeted Muscle Reinnervation

New developments in targeted muscle reinnervation promise better options for treatment of neuropathic pain and improved prosthetic control. For transhumeral amputations, the traditional approach involves an anterior incision to access the median and ulnar nerves and a second posterior incision to access the radial nerve. This is necessitated as exposure of motor branches of the radial nerve distal to the branch to the long head of the triceps is difficult from the anterior approach. Herein, we describe a technique for transferring the radial nerve proper distal to the long head branch to a motor branch to the medial or lateral head of the triceps through internal neurolysis and fascicular transfer. This allows all surgical steps to be performed through a single incision while preserving native motor branches to the biceps and triceps muscles.

Management of conflict injuries to the upper limb. Part 1: assessment and early surgical care

Upper limb injuries are common in conflict zones. The functions of the upper limb are impossible to replicate with prosthetic replacement and wherever possible attempts should be made to preserve the limb with further secondary reconstruction aimed at restoration of function. Casualty assessment, haemorrhage control and resuscitation are simultaneously undertaken at the receiving medical facility. Primary surgical management involves decontamination and debridement, skeletal stabilization, restoration of vascularity, compartment fasciotomy where indicated and wound temporization with dressings. Operative findings and interventions should be documented and if evacuation of the casualty is possible, copies should be provided in the medical records to facilitate communication in the chain of care. Secondary procedures are required for further assessment and debridement prior to planning reconstruction and definitive fracture stabilization, nerve repair, wound cover or closure.

Variation on a technique for the intra-muscular insertion of nerve endings to minimise neuropathic and residual pain in lower limb amputees: a retrospective cohort study

INTRODUCTION

A major cause of morbidity in lower limb amputees is phantom limb pain (PLP) and residual limb pain (RLP). This study aimed to determine whether a variation of the surgical technique of inserting nerve endings into adjacent muscle bellies at the time of lower limb amputation can decrease the incidence and severity of PLP and RLP.

METHODS

Data were retrospectively collected from January 2015 to January 2021, including eight patients that underwent nerve insertion (NI) and 36 that received standard treatment. Primary outcomes included the 11-point Numerical Rating Scale (NRS) for pain severity, and Patient-Reported Outcomes Measurement Information System (PROMIS) pain intensity, behaviour, and interference. Secondary outcome included Neuro-QoL Lower Extremity Function assessing mobility. Cumulative scores were transformed to standardised t scores.

RESULTS

Across all primary and secondary outcomes, NI patients had lower PLP and RLP. Mean 'worst pain' score was 3.5 out of 10 for PLP in the NI cohort, compared to 4.89 in the control cohort (p = 0.298), and 2.6 out of 10 for RLP in the NI cohort, compared to 4.44 in the control cohort (p = 0.035). Mean 'best pain' and 'current pain' scores were also superior in the NI cohort for PLP (p = 0.003, p = 0.022), and RLP (p = 0.018, p = 0.134). Mean PROMIS t scores were lower for the NI cohort for RLP (40.1 vs 49.4 for pain intensity; p = 0.014, 44.4 vs 48.2 for pain interference; p = 0.085, 42.5 vs 49.9 for pain behaviour; p = 0.025). Mean PROMIS t scores were also lower for the NI cohort for PLP (42.5 vs 52.7 for pain intensity; p = 0.018); 45.0 vs 51.5 for pain interference; p = 0.015, 46.3 vs 51.1 for pain behaviour; p = 0.569). Mean Neuro-QoL t score was lower in NI cohort (45.4 vs 41.9; p = 0.03).

CONCLUSION

Surgical insertion of nerve endings into adjacent muscle bellies during lower limb amputation is a simple yet effective way of minimising PLP and RLP, improving patients' subsequent quality of life. Additional comparisons with targeted muscle reinnervation should be performed to determine the optimal treatment option.

Failed Targeted Muscle Reinnervation: Findings at Revision Surgery and Concepts for Success

Although it was initially described for improved myoelectric control, targeted muscle reinnervation (TMR) has quickly gained popularity as a technique for neuroma control. With this rapid increase in utilization has come broadening indications and variability in the described technique. As a result, it becomes difficult to interpret published outcomes. Furthermore, there is no literature discussing the management of failed cases which are undoubtedly occurring.

Peripheral Nerve Management in Extremity Amputations

The effective management of peripheral nerves in amputation surgery is critical to optimizing patient outcomes. Nerve-related pain after amputation is common, maybe a source of dissatisfaction and functional impairment, and should be considered in all amputees presenting with pain and dysfunction. While traction neurectomy or transposition has long been the standard of care, both regenerative peripheral nerve interface (RPNI) and targeted muscle reinnervation (TMR) have emerged as promising techniques to improve neuroma-related and phantom pain. A multi-disciplinary and multi-modal approach is essential for the optimal management of amputees both acutely and in the delayed or chronic setting.

Achieving Functional Outcomes after Surgical Management of Catastrophic Vasopressor-induced Limb Ischemia

Vasopressor-induced limb ischemia is an unfortunate complication that can occur in patients treated for septic shock. Current literature lacks surgical treatment recommendations for this condition, besides amputation. We describe various reconstructive surgeries and functional outcomes in patients treated surgically for vasopressor-induced limb ischemia.

Methods

We retrospectively reviewed patients who were treated for septic shock and developed vasopressor-induced limb ischemia at our tertiary referral academic medical center. We reviewed presentation, treatment, surgical outcomes, and long-term functional outcomes.

Results

We present three previously healthy patients who developed gangrene of multiple limbs following the use of vasopressors to treat septic shock. Each patient underwent amputations or limb salvage procedures.

Conclusions

Limb ischemia is a devastating complication that can occur after prolonged vasopressor use. The decision to proceed with limb salvage versus amputation of ischemic extremities should be tailored to the individual patient. The main objective should be for the patient to obtain optimal function and quality of life, regardless of the type of surgery.

Targeted Muscle Reinnervation in the Hand: A Technical Roadmap

PURPOSE

Targeted muscle reinnervation (TMR) transfers cut the nerve endings to the motor nerves of the nearby muscles to reduce neuroma pain and/or enhance prosthetic function. To guide surgeons, anatomic "roadmaps" describe nerve transfer options for TMR at various locations. This study aimed to landmark and measure motor entry points (MEPs) to the hand interossei muscles in the context of TMR for digital nerve neuroma management.

METHODS

Ten fresh-frozen cadaveric hands were dissected to describe the innervation arising from the deep branch of the ulnar nerve to the dorsal interossei (DIs) and palmar interossei (PIs) muscles. The location of MEPs relative to the bone and soft tissue landmarks and the size of the target nerves were measured.

RESULTS

The MEPs for the DIs and PIs were found in the central third of the metacarpal. The MEPs to the PIs averaged 23.3-24.7 mm from the median nerve. The length of nerve proximal to the MEP was limited, ranging between 6.5 ± 2.6 mm for the first PI and 10.5 ± 2.7 mm for the second PI. Similarly, minimal nerve proximal to the MEP of the DI was available for mobilization. Access to the first PI innervation required substantial release of the thenar musculature. Motor nerve diameter averaged 0.85-0.97 mm.

CONCLUSIONS

In considering TMR for the management or prevention of digital nerve neuromas, the motor branches to the second and third PIs are the most accessible and best approached volarly, whereas motor branches to the DIs take more direct routes into the muscle, making volar exposure difficult. Nerve length proximal to the MEP is short, requiring that most of the nerve length for neurorrhaphy comes from the digital nerve. Size mismatch at the neurorrhaphy site is favorable compared to more proximal TMR.

CLINICAL RELEVANCE

Targeted muscle reinnervation in the hand is technically feasible for a patient with a symptomatic neuroma after digital amputation.

[Targeted muscle reinnervation and targeted sensory reinnervation : Role of complex neurotization after amputation]

In association with major amputations of the upper and lower extremities, surgical procedures with nerve transfer are increasingly being introduced. In order to examine the value of these procedures the currently available data were analyzed and related to the corresponding insights from conventional amputation surgery as well as confirmed aspects of microsurgery of peripheral nerves. Mainly retrospective observations of low case numbers and sometimes individually different surgical approaches can be found. Risk analysis and sufficient long-term follow-up periods are lacking as well as comparisons with appropriate control groups. The published results on operative procedures with selected nerve transfers after or during amputation do not currently allow any conclusions about the advantages. Systematic influences in the assessment of the results are probable. Implementation of these treatment options outside controlled clinical trials cannot be recommended.

Treatment of Refractory Radial Sensory Neuroma With Function-Sparing Targeted Muscle Reinnervation to the Extensor Carpi Radialis Brevis

The radial sensory nerve can be injured during many common procedures, including intravenous cannulation, first extensor compartment release, and radial-sided wrist surgery. Injury to the nerve may result in neuroma formation that can lead to chronic and debilitating pain. Nonsurgical treatments and surgical interventions, including excision of the neuroma and burying the nerve into local muscle, are frequently ineffective. Here, we present a technique for treating recalcitrant neuromas of the radial sensory nerve with targeted muscle reinnervation to a redundant motor nerve branch of the extensor carpi radialis brevis.

Challenges and Potential in Targeted Muscle Reinnervation in Pediatric Amputees

Targeted muscle reinnervation (TMR) is a powerful new tool in preventing and treating residual limb and phantom limb pain. In the adult population, TMR is rapidly becoming standard of care; however, there is a paucity of literature regarding indications and outcomes of TMR in the pediatric population. We present 2 cases of pediatric patients who sustained amputations and the relevant challenges associated with TMR in their cases. One is a 7-year-old patient who developed severe phantom and residual limb pain after a posttraumatic above-knee amputation. He failed pharmacologic measures and underwent TMR. He obtained complete relief of his symptoms and is continuing to do well 1.5 years postoperatively. The other is a 2-year-old boy with bilateral wrist and below-knee amputations as sequelae of sepsis. TMR was not performed because the patient never demonstrated evidence of phantom limb pain or symptomatic neuroma formation. We use these 2 cases to explore the challenges particular to pediatric patients when considering treatment with TMR, including capacity to report pain, risks of anesthesia, and cortical plasticity. These issues will be critical in determining how TMR will be applied to pediatric patients.

Revision Targeted Muscle Reinnervation Improves Secondary Pain Insult in an Upper Extremity Amputee: A Case Report

Targeted muscle reinnervation (TMR) has been shown to improve phantom and neuropathic pain in both the acute and chronic amputee population. Through rerouting of major peripheral nerves into a newly denervated muscle, TMR harnesses the plasticity of the brain, helping to revert the sensory cortex back toward the preinsult state, effectively reducing pain. We highlight a unique case of an above-elbow amputee for sarcoma who was initially treated with successful transhumeral TMR. Following inadvertent nerve biopsy of a TMR coaptation site, his pain returned, and he was unable to don his prosthetic. Revision of his TMR to a more proximal level was performed, providing improved pain and function of the amputated arm. This is the first report to highlight the concept of secondary neuroplasticity and successful proximal TMR revision in the setting of multiple insults to the same extremity.

A consecutive series of targeted muscle reinnervation (TMR) cases for relief of neuroma and phantom limb pain: UK perspective

BACKGROUND

Studies have suggested that targeted muscle reinnervation (TMR) can improve symptoms of neuroma pain (NP) and phantom limb pain (PLP) in patients.

OBJECTIVES

Our primary objective was to measure changes in NP and PLP levels following TMR surgery at 4-time points (baseline, 3, 6- and 12-months postoperatively). Secondary aims included identification of the character and rate of any surgical complications and patients' satisfaction with TMR.

METHODS

A retrospective review of outcomes of 36 patients who underwent TMR surgery to treat intractable NP and/or PLP after major amputation of an upper (UL) or lower limb (LL) at a single centre in London, UK over 7 years. The surgical techniques, complications, and satisfaction with TMR are described.

RESULTS

Forty TMR procedures were performed on 36 patients. Thirty patients had complete data for NP and PLP levels at all pre-defined time points. Significant improvements (p<0.01) in both types of pain were observed for both upper and LL amputees. However, there were varying patterns of recovery. For example, UL amputees experienced worsening of PLP in the first few months post-operatively whereas surgical complications were more common in LL cases. Patients were overwhelmingly satisfied with the improvements in their symptoms (90%).

CONCLUSIONS

TMR surgery appeared to relieve both NP and PLP although the retrospective nature of this study limits the strength of this conclusion. However, complication rates were high, and it is crucial for surgeons and patients to fully understand the course and outcomes of this novel surgery prior to undertaking treatment.

Targeted Muscle Reinnervation for the Treatment of Neuroma

Targeted muscle reinnervation (TMR) is the surgical rerouting of severed nerve endings to nearby expendable motor nerve branches. These nerve transfers provide a pathway for axonal growth, limiting the amputated nerve ends' disorganized attempt at regeneration that leads to neuroma formation. In the amputee population, TMR is successful in the treatment and prevention of chronic phantom limb pain and residual limb pain. In the nonamputee population, applications of TMR are ever expanding in the treatment of chronic neuroma pain owing to trauma, compression, or surgery. This article reviews the indications for TMR, preoperative evaluation, and various surgical techniques.

Regenerative Peripheral Nerve Interfaces for the Treatment and Prevention of Neuromas and Neuroma Pain

A neuroma occurs when a regenerating transected peripheral nerve has no distal target to reinnervate. This situation can result in a hypersensitive free nerve ending that causes debilitating pain to affected patients. No techniques to treat symptomatic neuromas have shown consistent results. One novel physiologic solution is the regenerative peripheral nerve interface (RPNI). RPNI consists of a transected peripheral nerve that is implanted into an autologous free skeletal muscle graft. Early clinical studies have shown promising results in the use of RPNIs to treat and prevent symptomatic neuromas. This review article describes the rationale behind the success of RPNIs and its clinical applications.

Myoelectric control of robotic lower limb prostheses: a review of electromyography interfaces, control paradigms, challenges and future directions

Objective.Advanced robotic lower limb prostheses are mainly controlled autonomously. Although the existing control can assist cyclic movements during locomotion of amputee users, the function of these modern devices is still limited due to the lack of neuromuscular control (i.e. control based on human efferent neural signals from the central nervous system to peripheral muscles for movement production). Neuromuscular control signals can be recorded from muscles, called electromyographic (EMG) or myoelectric signals. In fact, using EMG signals for robotic lower limb prostheses control has been an emerging research topic in the field for the past decade to address novel prosthesis functionality and adaptability to different environments and task contexts. The objective of this paper is to review robotic lower limb Prosthesis control via EMG signals recorded from residual muscles in individuals with lower limb amputations.Approach.We performed a literature review on surgical techniques for enhanced EMG interfaces, EMG sensors, decoding algorithms, and control paradigms for robotic lower limb prostheses.Main results.This review highlights the promise of EMG control for enabling new functionalities in robotic lower limb prostheses, as well as the existing challenges, knowledge gaps, and opportunities on this research topic from human motor control and clinical practice perspectives.Significance.This review may guide the future collaborations among researchers in neuromechanics, neural engineering, assistive technologies, and amputee clinics in order to build and translate true bionic lower limbs to individuals with lower limb amputations for improved motor function.

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.

Revision Peripheral Nerve Surgery of the Upper Extremity

Peripheral nerve injuries of the upper extremity can result from a wide array of etiologies, with the two most common being compression neuropathy and traumatic injuries. These types of injuries are common and can be psychologically, functionally, and financially devastating to the patient. A detailed preoperative evaluation is imperative for appropriate management. Traumatic injuries can typically be treated with local burial techniques, targeted muscle reinnervation, and regenerative peripheral nerve interfaces. Median nerve compression is frequently managed with complete release of the antebrachial fascia/transverse carpal ligament and/or use of flap coverage such as the hypothenar fat pad flap and local muscle flaps. Ulnar nerve compression is commonly managed via submuscular transposition, subcutaneous transposition, neurolysis, and nerve wrapping. In this review, we discuss the preoperative evaluation, surgical techniques, and advantages and disadvantages of each treatment modality for patients with compressive and traumatic upper extremity nerve injuries.

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.

Targeted Muscle Reinnervation: A Paradigm Shift for Neuroma Management and Improved Prosthesis Control in Major Limb Amputees

Targeted muscle reinnervation (TMR) is a procedure that redirects nerves severed by amputation to new muscle targets. In tandem with advances in myoelectric prosthetics, TMR surgery provides amputees with improved control of myoelectric prostheses and simultaneously prevents or treats painful neuromas. TMR also has an emerging role in the management of neuromas in a nonamputation setting, and it seems to be a powerful strategy to treat a wide variety of neuromas. Because the pattern of nerve transfers varies based on the availability of donor nerves and muscle targets, TMR is inherently nonprescriptive, and thus, an understanding of the principles of TMR is essential for its successful application. This review describes the rationale for and principles of TMR, and outlines techniques for TMR, which can be used at various amputation levels and for the management of neuromas in nonamputees.

Surgical and technological advances in the management of upper limb amputees

Upper limb amputations, ranging from transhumeral to partial hand, can be devastating for patients, their families, and society. Modern paradigm shifts have focused on reconstructive options after upper extremity limb loss, rather than considering the amputation an ablative procedure. Surgical advancements such as targeted muscle reinnervation and regenerative peripheral nerve interface, in combination with technological development of modern prosthetics, have expanded options for patients after amputation. In the near future, advances such as osseointegration, implantable myoelectric sensors, and implantable nerve cuffs may become more widely used and may expand the options for prosthetic integration, myoelectric signal detection, and restoration of sensation. This review summarizes the current advancements in surgical techniques and prosthetics for upper limb amputees. Cite this article: Bone Joint J 2021;103-B(3):430-439.

Complex Microsurgical Reconstruction After Tumor Resection in the Trunk and Extremities

Reconstruction of soft tissue defects following tumor ablation procedures in the trunk and extremities can challenge the microsurgeon. The goal is not just to provide adequate soft tissue coverage but also to restore form and function and minimize donor site morbidity. Although the principles of the reconstructive ladder still apply in the trunk and extremities, free tissue transfer is used in many cases to optimally restore form and function. Microsurgery has changed the practice in soft tissue tumors, and amputation is less frequently necessary.

Targeted Muscle Reinnervation at the Time of Upper-Extremity Amputation for the Treatment of Pain Severity and Symptoms

PURPOSE

Targeted muscle reinnervation (TMR) is a technique for the management of peripheral nerves in amputation. Phantom limb pain (PLP) and residual limb pain (RLP) trouble many patients after amputation, and TMR has been shown to reduce this pain when performed after the initial amputation. We hypothesize that TMR at the time of amputation may improve pain for patients after major upper-extremity amputation.

METHODS

We conducted a retrospective review of patients who underwent major upper-extremity amputation with TMR performed at the time of the index amputation (early TMR). Phantom limb pain and RLP intensity and associated symptoms were assessed using the numeric rating scale (NRS), the Patient-Reported Outcome Measurement Information System (PROMIS) Pain Intensity Short-Form 3a, the Pain Behavior Short-Form 7a, and the Pain Interference Short-Form 8a. The TMR cohort was compared with benchmarked data from a sample of upper-extremity amputees.

RESULTS

Sixteen patients underwent early TMR and were compared with 55 benchmark patients. More than half of early TMR patients were without PLP (62%) compared with 24% of controls. Furthermore, half of all patients were free of RLP compared with 36% of controls. The median PROMIS PLP intensity score for the general sample was 47 versus 38 in the early TMR sample. Patients who underwent early TMR reported reduced pain behaviors and interference specific to PLP (50 vs 53 and 41 vs 50, respectively). The PROMIS RLP intensity score was lower in patients with early TMR (36 vs 47).

CONCLUSIONS

This study demonstrates that early TMR is a promising strategy for treating pain and improving the quality of life in the upper-extremity amputee. Early TMR may preclude the need for additional surgery and represents an important technique for peripheral nerve surgery.

TYPE OF STUDY/LEVEL OF EVIDENCE

Therapeutic IV.

Treatment of Neuroma of the Dorsal Branch of the Ulnar Nerve With Transfer to the Distal Anterior Interosseous Nerve

Painful neuromas of the dorsal branch of the ulnar nerve may be difficult to treat. Proximal transposition is the standard treatment, but pain may recur. Sensory-to-motor nerve transfer as an evolution of targeted muscle reinnervation is a recently described technique to reduce neuroma formation in the treatment of painful neuromas. This report describes sensory-to-motor transfer of the dorsal branch of the ulnar nerve to the distal anterior interosseous nerve to treat a painful neuroma.

TMRpni: Combining Two Peripheral Nerve Management Techniques

Amputee patients suffer high rates of chronic neuropathic pain, residual limb dysfunction, and disability. Recently, targeted muscle reinnervation (TMR) and regenerative peripheral nerve interface (RPNI) are 2 techniques that have been advocated for such patients, given their ability to maximize intuitive prosthetic function while also minimizing neuropathic pain, such as residual and phantom limb pain. However, there remains room to further improve outcomes for our residual limb patients and patients suffering from symptomatic end neuromas. "TMRpni" is a nerve management technique that leverages beneficial elements described for both TMR and RPNI. TMRpni involves coaptation of a sensory or mixed sensory/motor nerve to a nearby motor nerve branch (ie, a nerve transfer), as performed in traditional TMR surgeries. Additionally, the typically mismatched nerve coaptation is wrapped with an autologous free muscle graft that is akin to an RPNI. The authors herein describe the "TMRpni" technique and illustrate a case where this technique was employed.

Targeted muscle reinnervation for the management of pain in the setting of major limb amputation

The life altering nature of major limb amputations may be further complicated by neuroma formation in up to 60% of the estimated 2 million major limb amputees in the United States. This can be a source of pain and functional limitation of the residual limb. Pain associated with neuromas may limit prosthetic limb use, require reoperation, lead to opioid dependence, and dramatically reduce quality of life. A number of management options have been described including excision alone, excision with repair, excision with transposition, and targeted muscle reinnervation. Targeted muscle reinnervation has been shown to reduce phantom limb and neuroma pain for patients with upper and lower extremity amputations. It may be performed at the time of initial amputation to prevent pain development or secondarily for the treatment of established pain. Encouraging outcomes have been reported, and targeted muscle reinnervation is emerging as a leading surgical technique for pain prevention in patients undergoing major limb amputations and pain management in patients with pre-existing amputations.

Targeted Muscle Reinnervation in the Hand: An Anatomical Feasibility Study for Neuroma Treatment and Prevention

PURPOSE

Targeted muscle reinnervation (TMR) has emerged as a treatment for, and prevention of, symptomatic neuromas and has been reported to be of benefit in the hand. Anatomical studies establishing landmarks for consistent identification of the motor entry points (MEPs) to the intrinsic muscles have not been performed. The purpose of this study was to provide details regarding the MEPs to the intrinsic muscles, determine which MEPs are identifiable dorsally, and develop recommended sensory to MEP nerve coaptations for prophylactic TMR at the time of ray amputation or for management of symptomatic neuromas.

METHODS

Motor entry points to the intrinsic hand muscles were dissected in 5 fresh latex-injected cadavers. Number of MEPs, diameter, surface of entry, and distance from dorsal (Lister tubercle) and volar (hamate hook) landmarks were recorded for each target muscle. The digital sensory nerve diameters were measured for size comparison.

RESULTS

Motor entry points were identified to all 19 intrinsic muscles through a volar approach and 12 through a dorsal approach. For all fingers, at least 2 MEPs were consistently identified dorsally at the base of each amputation site innervating expendable muscles. Motor entry points to the thenar muscles were only reliably identified through a volar approach. Two recommended nerve coaptations for each digit amputation were identified. All had a favorable sensory-to-MEP diameter ratio less than 2:1.

CONCLUSIONS

The intrinsic hand muscles have MEPs at consistent distances from bony landmarks both dorsally and volarly.

CLINICAL RELEVANCE

These results can be applied clinically to assist surgeons in identifying the locations of MEPs to the intrinsic muscles when performing TMR in the hand for both neuroma treatment and prevention.

Surgical Technique for Below-knee Amputation with Concurrent Targeted Muscle Reinnervation

Targeted muscle reinnervation (TMR) is beneficial for decreasing pain following below-knee amputation (BKA). While most current literature describes the principles behind primary TMR, they provide few principles key to the amputation, as the BKA is usually performed by another surgeon. When the BKA and TMR are performed by the same surgeon, it can be performed through the same surgical access as needed for both procedures. The purpose of this article is to describe our anatomically based BKA technique in the setting of planned primary TMR as performed by 3, single, peripheral nerve plastic surgeons at 2 institutions. Advantages of the single-surgeon technique include efficiency in dissection, preservation of donor nerve length, limited proximal dissection, early identification of recipient motor nerves for coaptation, ability to stimulate these while still under tourniquet, and decreased tourniquet and operative time. This technique is quick, reliable, and reproducible to help promote widespread adoption of TMR at the time of BKA.