The effects of targeted muscle reinnervation on neuromas in a rabbit rectus abdominis flap model

Economic Cost-Benefit Analysis of Nerve Implanted into Muscle versus Targeted Muscle Reinnervation versus Regenerative Peripheral Nerve Interface, for Treatment of the Painful Neuroma

BACKGROUND

 This study investigated the relative cost utility of three techniques for the management of symptomatic neuromas after neuroma excision: (1) implantation of nerve into muscle, (2) targeted muscle reinnervation (TMR), and (3) regenerative peripheral nerve interface (RPNI).

METHODS

 The costs associated with each procedure were determined using Common Procedural Terminology codes in combination with data from the Centers for Medicaid and Medicare Services Physician and Facility 2020 Fee Schedules. The relative utility of the three procedures investigated was determined using changes in Patient-Reported Outcomes Measurement Information System (PROMIS) and Numeric Rating Scale (NRS) pain scores as reported per procedure. The relative utility of each procedure was reported in terms of quality-adjusted life years (QALYs), as is standard in the literature.

RESULTS

 The least expensive option for the surgical treatment of painful neuromas was nerve implantation into an adjacent muscle. In contrast, for the treatment of four neuromas, as is common postamputation, TMR without a microscope was found to cost $50,061.55 per QALY gained, TMR with a microscope was found to cost $51,996.80 per QALY gained, and RPNI was found to cost $14,069.28 per QALY gained. While RPNI was more expensive than nerve implantation into muscle, it was still below the standard willingness-to-pay threshold of $50,000 per QALY, while TMR was not.

CONCLUSION

 Evaluation of costs and utilities associated with the various surgical options for the management of painful neuromas suggest that nerve implantation into muscle is the least expensive option with the best improvement in QALY, while demonstrating comparable outcomes to TMR and RPNI with regard to pain symptoms.

Approaches to neuropathic amputation-related pain: narrative review of surgical, interventional, and medical treatments

BACKGROUND/IMPORTANCE

Neuropathic amputation-related pain can consist of phantom limb pain (PLP), residual limb pain (RLP), or a combination of both pathologies. Estimated of lifetime prevalence of pain and after amputation ranges between 8% and 72%.

OBJECTIVE

This narrative review aims to summarize the surgical and non-surgical treatment options for amputation-related neuropathic pain to aid in developing optimized multidisciplinary and multimodal treatment plans that leverage multidisciplinary care.

EVIDENCE REVIEW

A search of the English literature using the following keywords was performed: PLP, amputation pain, RLP. Abstract and full-text articles were evaluated for surgical treatments, medical management, regional anesthesia, peripheral block, neuromodulation, spinal cord stimulation, dorsal root ganglia, and peripheral nerve stimulation.

FINDINGS

The evidence supporting most if not all interventions for PLP are inconclusive and lack high certainty. Targeted muscle reinnervation and regional peripheral nerve interface are the leading surgical treatment options for reducing neuroma formation and reducing PLP. Non-surgical options include pharmaceutical therapy, regional interventional techniques and behavioral therapies that can benefit certain patients. There is a growing evidence that neuromodulation at the spinal cord or the dorsal root ganglia and/or peripheral nerves can be an adjuvant therapy for PLP.

CONCLUSIONS

Multimodal approaches combining pharmacotherapy, surgery and invasive neuromodulation procedures would appear to be the most promising strategy for preventive and treating PLP and RLP. Future efforts should focus on cross-disciplinary education to increase awareness of treatment options exploring best practices for preventing pain at the time of amputation and enhancing treatment of chronic postamputation pain.

TMR Using a Free Rectus Flap after Transhumeral Amputation

Targeted muscle reinnervation offers an approach to regain use of the affected extremity through electronic prosthesis while limiting phantom pain and neuroma limb production or pain. In this case report, we present the first reported case of leveraging the rectus flap for targeted muscle reinnervation. The case herein is of a 28-year-old woman who sustained a severe right upper extremity crush injury while being involved in a vehicular roll-over collision requiring right transhumeral amputation. Plastic surgery, orthopedic surgery, and vascular surgery were consulted to manage the right upper extremity injury.

Combining Surgical Innovations in Amputation Surgery-Robotic Harvest of the Rectus Abdominis Muscle, Transplantation and Targeted Muscle Reinnervation Improves Myocontrol Capability and Pain in a Transradial Amputee

Adding robotic surgery to bionic reconstruction might open a new dimension. The objective was to evaluate if a robotically harvested rectus abdominis (RA) transplant is a feasible procedure to improve soft-tissue coverage at the residual limb (RL) and serve as a recipient for up to three nerves due to its unique architecture and to allow the generation of additional signals for advanced myoelectric prosthesis control. A transradial amputee with insufficient soft-tissue coverage and painful neuromas underwent the interventions and was observed for 18 months. RA muscle was harvested using robotic-assisted surgery and transplanted to the RL, followed by end-to-end neurroraphy to the recipient nerves of the three muscle segments to reanimate radial, median, and ulnar nerve function. The transplanted muscle healed with partial necrosis of the skin mesh graft. Twelve months later, reliable, and spatially well-defined Hoffmann-Tinel signs were detectable at three segments of the RA muscle flap. No donor-site morbidities were present, and EMG activity could be detected in all three muscle segments. The linear discriminant analysis (LDA) classifier could reliably distinguish three classes within 1% error tolerance using only the three electrodes on the muscle transplant and up to five classes outside the muscle transplant. The combination of these surgical procedure advances with emerging (myo-)control technologies can easily be extended to different amputation levels to reduce RL complications and augment control sites with a limited surface area, thus facilitating the usability of advanced myoelectric prostheses.

Outcomes of Targeted Muscle Reinnervation and Regenerative Peripheral Nerve Interfaces for Chronic Pain Control in the Oncologic Amputee Population

BACKGROUND

Outcomes of targeted muscle reinnervation (TMR) and regenerative peripheral nerve interface (RPNI) in the oncologic population are limited. We sought to examine the safety and effectiveness of TMR and RPNI in controlling postamputation pain in the oncologic population.

STUDY DESIGN

A retrospective cohort study of consecutive patients who underwent oncologic amputation followed by immediate TMR or RPNI was conducted from November 2018 to May 2022. The primary study outcome was postamputation pain, assessed using the Numeric Pain Scale and Patient-Reported Outcomes Measurement Information System (PROMIS) for residual limb pain (RLP) and phantom limb pain (PLP). Secondary outcomes included postoperative complications, tumor recurrence, and opioid use.

RESULTS

Sixty-three patients were evaluated for a mean follow-up period of 11.3 months. The majority of patients (65.1%) had a history of previous limb salvage. At final follow-up, patients had an average Numeric Pain Scale score for RLP of 1.3 ± 2.2 and for PLP, 1.9 ± 2.6. The final average raw PROMIS measures were pain intensity 6.2 ± 2.9 (T-score 43.5), pain interference 14.6 ± 8.3 (T-score 55.0), and pain behavior 39.0 ± 22.1 (T-score 53.4). Patient opioid use decreased from 85.7% preoperatively to 37.7% postoperatively and morphine milligram equivalents decreased from a mean of 52.4 ± 53.0 preoperatively to 20.2 ± 38.4 postoperatively.

CONCLUSIONS

In the oncologic population TMR and RPNI are safe surgical techniques associated with significant reductions in RLP, PLP, and improvements in patient-reported outcomes. This study provides evidence for the routine incorporation of TMR and RPNI in the multidisciplinary care of oncologic amputees.

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.

Targeted muscle reinnervation prevents and reverses rat pain behaviors after nerve transection

ABSTRACT

Targeted muscle reinnervation (TMR) is a clinical intervention that is rapidly becoming common in major limb amputation to prevent or reduce amputation-related pain. However, TMR is much less effective when applied long after injury compared with acute TMR. Since the mechanisms governing pain relief in TMR of amputated nerves are unknown, we developed a preclinical model as a platform for mechanistic examination. Following spared nerve injury (SNI), rats underwent either TMR, simple neuroma excision, or a sham manipulation of the injury site. These interventions were performed immediately or delayed (3 or 12 weeks) after SNI. Pain behavior was measured as sensitivity to mechanical stimuli (pin, von Frey, and dynamic brush) and thermal stimuli (acetone and radiant heat). Spared nerve injury produced hypersensitivity to all mechanical stimuli and cold, which persisted after sham surgery. Targeted muscle reinnervation at the time of SNI prevented the development of pain behaviors and performing TMR 3 weeks after SNI reversed pain behaviors to baseline. By contrast, TMR performed at 12 weeks after SNI had no effect on pain behaviors. Neuroma excision resulted in significantly less reduction in hyperalgesia compared with TMR when performed 3 weeks after SNI but had no effect at 12 weeks after SNI. In this model, the pain phenotype induced by nerve transection is reduced by TMR when performed within 3 weeks after injury. However, TMR delayed 12 weeks after injury fails to reduce pain behaviors. This replicates clinical experience with limb amputation, supporting validity of this model for examining the mechanisms of TMR analgesia.

Traumatic neuromas of peripheral nerves: Diagnosis, management and future perspectives

Traumatic neuromas are infrequent in clinical settings but are prevalent following trauma or surgery. A traumatic neuroma is not a true malignancy, rather, it is a hyperplastic, reparative nerve reaction after injury and typically manifests as a nodular mass. The most common clinical manifestations include painful hypersensitivity and the presence of a trigger point that causes neuralgic pain, which could seriously decrease the living standards of patients. While various studies are conducted aiming to improve current diagnosis and management strategies via the induction of emerging imaging tools and surgical or conservative treatment. However, researchers and clinicians have yet to reach a consensus regarding traumatic neuromas. In this review, we aim to start with the possible underlying mechanisms of traumatic neuromas, elaborate on the diagnosis, treatment, and prevention schemes, and discuss the current experiment models and advances in research for the future management of traumatic neuromas.

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.

RPNI, TMR, and Reset Neurectomy/Relocation Nerve Grafting after Nerve Transection in Headache Surgery

In the context of headache surgery, greater occipital nerve (GON) transection is performed when the nerve appears severely damaged, if symptoms are recurrent or persistent, and when neuromas are excised. Lesser occipital nerve (LON) excision is commonly performed during the primary decompression surgery. Advanced techniques to address the proximal nerve stump after nerve transection such as regenerative peripheral nerve interface (RPNI), targeted muscle reinnervation (TMR), relocation nerve grafting, and reset neurectomy have been shown to improve chronic pain and neuroma formation. These techniques have not been described in the head and neck region.

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.

"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.

A sciatic nerve gap-injury model in the rabbit

There has been an increased number of studies of nerve transection injuries with the sciatic nerve gap-injury model in the rabbit in the past 2 years. We wanted to define in greater detail what is needed to test artificial nerve guides in a sciatic nerve gap-injury model in the rabbit. We hope that this will help investigators to fully exploit the robust translational potential of the rabbit sciatic nerve gap-injury model in its capacity to test devices whose diameter and length are in the range of those commonly applied in hand and wrist surgery (diameter ranging between 2 and 4 mm; length up to 30 mm). We suggest that the rabbit model should replace the less translational rat model in nerve regeneration research. The rabbit sciatic model, however, requires an effective strategy to prevent and control self-mutilation of the foot in the postoperative period, and to prevent pressure ulcers.

Higher incidences of neuropathic pain and altered sensation following radial forearm free flap: A systematic review

BACKGROUND

The radial forearm free flap (RFFF) has been used extensively for complex tissue defect reconstructions; however, the potential for significant donor-site morbidity remains a major drawback. Despite an abundance of literature on donor-site morbidities, no consensus has been reached on exact incidences of sensory morbidities that vary largely between 0% and 46%. Incidences of neuropathic pain in the donor site following RFFF still lack, even though clinical experience shows it often occurs. Therefore, the purpose of this systematic review was to identify the incidence of neuropathic pain and altered sensation in the hand following harvesting of a RFFF.

METHODS

A systematic search was performed in multiple databases (Embase, Medline, Cochrane, Web of Science, and Google Scholar). Studies from 1990 onwards that reported donor-site morbidities following harvest of the RFFF were included. Analyzed parameters included hand pain, hypoesthesia, cold intolerance, hyperesthesia, neuroma formation, paresthesia, sharp sensation loss, light sensation loss, and defect closure.

RESULTS

Of the 987 selected studies, 51 eligible articles were selected. The mean level of evidence was 3 (SD 0.6). Twenty articles reported pain as a donor-site morbidity, and the mean incidence of pain reported was 23% (SD 7.8). Hypoesthesia was reported by 37 articles and had a mean incidence of 34% (SD 25). Locations of pain and hypoesthesia included, amongst others, the area of the radial sensory nerve and the skin graft area. The mean incidences of cold intolerance and hyperesthesia were 13% (SD 13) and 16% (SD 15), respectively.

CONCLUSION

The results of this systematic review suggest that 23% of all patients are dealing with neuropathic pain in the donor-site following harvest of an RFFF. Future studies should therefore focus on the prognostic factors and preventive measures of neuropathic pain to further improve clinical outcomes of this widely used flap.

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.

Nerve Interface Strategies for Neuroma Management and Prevention: A Conceptual Approach Guided by Institutional Experience

In this article, the authors propose a strategy to manage and prevent symptomatic neuromas using a combination of nerve interface approaches. By using a reconstructive paradigm, these procedures provide the components integral to organized nerve regeneration, conferring both improvements in pain and potential for myoelectric control of prostheses in the future. Given the lack of evidence at this point indicating the advantage of any single nerve interface procedure, the authors propose a management approach that maximizes physiologic restoration while limiting morbidity where possible.

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.

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.

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.

Clinical updates on phantom limb pain

Phantom limb pain is highly prevalent after amputation. Treatment results will probably benefit from an interdisciplinary team and individually adapted surgical, prosthetic and pain medicine approaches.

Introduction:

Most patients with amputation (up to 80%) suffer from phantom limb pain postsurgery. These are often multimorbid patients who also have multiple risk factors for the development of chronic pain from a pain medicine perspective. Surgical removal of the body part and sectioning of peripheral nerves result in a lack of afferent feedback, followed by neuroplastic changes in the sensorimotor cortex. The experience of severe pain, peripheral, spinal, and cortical sensitization mechanisms, and changes in the body scheme contribute to chronic phantom limb pain. Psychosocial factors may also affect the course and the severity of the pain. Modern amputation medicine is an interdisciplinary responsibility.

Methods:

This review aims to provide an interdisciplinary overview of recent evidence-based and clinical knowledge.

Results:

The scientific evidence for best practice is weak and contrasted by various clinical reports describing the polypragmatic use of drugs and interventional techniques. Approaches to restore the body scheme and integration of sensorimotor input are of importance. Modern techniques, including apps and virtual reality, offer an exciting supplement to already established approaches based on mirror therapy. Targeted prosthesis care helps to obtain or restore limb function and at the same time plays an important role reshaping the body scheme.

Discussion:

Consequent prevention and treatment of severe postoperative pain and early integration of pharmacological and nonpharmacological interventions are required to reduce severe phantom limb pain. To obtain or restore body function, foresighted surgical planning and technique as well as an appropriate interdisciplinary management is needed.

Risk Factors for Neuropathic Pain Following Major Upper Extremity Amputation

BACKGROUND

 Active treatment (targeted muscle reinnervation [TMR] or regenerative peripheral nerve interfaces [RPNIs]) of the amputated nerve ends has gained momentum to mitigate neuropathic pain following amputation. Therefore, the aim of this study is to determine the predictors for the development of neuropathic pain after major upper extremity amputation.

METHODS

 Retrospectively, 142 adult patients who underwent 148 amputations of the upper extremity between 2000 and 2019 were identified through medical chart review. All upper extremity amputations proximal to the metacarpophalangeal joints were included. Patients with a follow-up of less than 6 months and those who underwent TMR or RPNI at the time of amputation were excluded. Neuropathic pain was defined as phantom limb pain or a symptomatic neuroma reported in the medical charts at 6 months postoperatively. Most common indications for amputation were oncology (n = 53, 37%) and trauma (n = 45, 32%), with transhumeral amputations (n = 44, 30%) and shoulder amputations (n = 37, 25%) being the most prevalent.

RESULTS

 Neuropathic pain occurred in 42% of patients, of which 48 (32%) had phantom limb pain, 8 (5.4%) had a symptomatic neuroma, and 6 (4.1%) had a combination of both. In multivariable analysis, traumatic amputations (odds ratio [OR]: 4.1, p = 0.015), transhumeral amputations (OR: 3.9, p = 0.024), and forequarter amputations (OR: 8.4, p = 0.003) were independently associated with the development of neuropathic pain.

CONCLUSION

 In patients with an upper extremity amputation proximal to the elbow or for trauma, there is an increased risk of developing neuropathic pain. In these patients, primary TMR/RPNI should be considered and this warrants a multidisciplinary approach involving general trauma surgeons, orthopaedic surgeons, plastic surgeons, and vascular surgeons.

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: Treatment and Prevention of Pain After Ray Amputation

Targeted muscle reinnervation (TMR), originally developed as an experimental technique for prosthetic control, has been shown to be safe and effective for the treatment and prevention of postamputation pain. Targeted muscle reinnervation involves coaptation of residual nerve ends to nearby motor nerve branches of healthy but expendable muscles proximal to an amputation. It has been shown to prevent and reduce residual limb pain and phantom limb pain after major upper and lower extremity amputation. However, the use of this technique has not been described distal to the forearm because bioprosthetic use is not a consideration at that level. The aim of this article was to (1) present 2 cases of TMR performed in the setting of ray amputation, and (2) provide technical strategies for maximizing success and efficiency.

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.

Patient-Reported Outcomes following Surgical Treatment of Symptomatic Digital Neuromas

BACKGROUND

Many surgical techniques are used to treat symptomatic neuroma, but options are limited for digital neuromas because of a paucity of soft-tissue coverage and/or the absence of the terminal nerve end. The authors assessed factors that influence patient-reported outcomes after surgery for symptomatic digital neuroma.

METHODS

The authors retrospectively identified 29 patients with 33 symptomatic digital neuromas that were treated surgically. Patients completed the Patient-Reported Outcomes Measurement Information System (PROMIS) Upper Extremity and Pain Interference scales, a numeric rating scale for pain, and the PROMIS Depression scale at a median follow-up of 7.6 years postoperatively (range, 3.2 to 16.8 years). Surgical treatment for neuroma included excision with nerve repair/reconstruction (n =13; 39 percent), neuroma excision alone (n =10; 30 percent), and excision and implantation (n =10; 30 percent). Multivariable linear regression was performed to identify the factors that independently influenced patient-reported outcomes.

RESULTS

The mean postoperative PROMIS Upper Extremity score was 45.2 ± 11.2, the mean Pain Interference score was 54.3 ± 10.7, and the mean numeric rating scale pain score was 3 (interquartile range, 1 to 5). Compared with other treatment techniques, neuroma excision with nerve repair/reconstruction was associated with lower numeric rating scale pain scores; lower Pain Interference scores, corresponding to less daily impact of pain; and higher Upper Extremity scores, reflecting better upper extremity function. Older age and higher Depression scores were associated with lower Upper Extremity scores and higher Pain Interference scores. Smoking was associated with higher Pain Interference and numeric rating scale pain scores.

CONCLUSIONS

Neuroma excision followed by nerve repair/reconstruction resulted in better outcomes compared with neuroma excision alone with or without implantation. Patient age and psychosocial factors influenced patient-reported outcomes.

CLINICAL QUESTION/LEVEL OF EVIDENCE

Risk, III.

Targeted Muscle Reinnervation at the Time of Major Limb Amputation in Traumatic Amputees: Early Experience of an Effective Treatment Strategy to Improve Pain

Background

Orthopaedic trauma etiologies are a common cause for amputation. Targeted muscle reinnervation (TMR) is a technique aimed at reducing or preventing pain and improving function. The purpose of this study was to examine postoperative phantom limb pain and residual limb pain following TMR in orthopaedic trauma amputees. In addition, postoperative rates of opioid and neuromodulator medication use were evaluated.

Methods

Twenty-five patients (60% male) prospectively enrolled in a single-institution study and underwent TMR at the time of major limb amputation (48% nonmilitary trauma, 32% infection secondary to previous nonmilitary trauma, and 20% other, also secondary to trauma). Phantom limb pain and residual limb pain scores, pain temporality, prosthetic use, and unemployment status were assessed at the time of follow-up. The use of opioid and neuromodulator medications both preoperatively and postoperatively was also examined.

Results

At a mean follow-up of 14.1 months, phantom limb pain and residual limb pain scores were low, with 92% of the patients reporting no pain or brief intermittent pain only. Pain scores were higher overall for male patients compared with female patients (p < 0.05) except for 1 subscore, and higher in patients who underwent amputation for infection (odds ratio, 9.75; p = 0.01). Sixteen percent of the patients reported opioid medication use at the time of the latest documented follow-up. Fifty percent of the patients who were taking opioids preoperatively discontinued use postoperatively, while 100% of the patients who were not taking opioids preoperatively discontinued postoperative use. None of the patients who were taking neuromodulator medication preoperatively discontinued use postoperatively (0 of 5). The median time to neuromodulator medication discontinuation was 14.6 months, with female patients taking longer than male patients (23 compared with 7 months; p = 0.02). At the time of the latest follow-up, the rate of reported prosthetic use was 85% for lower-extremity and 40% for upper-extremity amputees, with a rate of unemployment due to disability of 36%.

Conclusions

The use of TMR in orthopaedic trauma amputees was associated with low overall pain scores at 2-year follow-up, decreased overall opioid and neuromodulator medication use, and an overall high rate of daily prosthetic use.

Level of Evidence

Therapeutic Level IV. See Instructions for Authors for a complete description of levels of evidence.

Management of Sural Nerve Neuromas with Targeted Muscle Reinnervation

Neuromas are a debilitating peripheral nerve problem due to aberrant axon sprouting and inflammation after nerve injury. The surgical management of neuromas has for a long time been up for debate, largely due to lack of consistent, reliable outcomes with any one technique. We have found success utilizing targeted muscle reinnervation, a technique originally described in amputees that re-routes the proximal ends of cut sensory nerve stumps into the distal ends of motor nerves to nearby muscles. In doing so, the sensory nerve ending can regenerate along the length of the motor nerve, giving it a place to go and something to do. In this report, we describe our technique specifically for targeted muscle reinnervation of sural nerve neuromas that is applicable to both amputees and to patients with intact limbs. Sural nerve neuromas can occur after sural nerve harvest for reconstructive procedures and particularly after lateral malleolar incisions for orthopedic access to the calcaneus. By re-routing the sural nerve into a motor nerve of the lateral gastrocnemius muscle, we are able to manage a variety of sural nerve neuromas presenting anywhere along the course of the sural nerve and in a variety of clinical settings.

Treatment of Neuroma-induced Chronic Pain and Management of Nerve Defects with Processed Nerve Allografts

Symptomatic neuromas can cause significant chronic pain and negatively impact quality of life. Symptoms often persist despite narcotics and nonoperative interventions, which are largely ineffective. With the opioid crisis, treatments for chronic pain that limit narcotics are needed. Traditional surgical options may result in neuroma recurrence. Autograft reconstruction often results in donor-site morbidity. Processed nerve allografts facilitate axonal growth, nerve regeneration, and eliminate donor-site morbidity.

Methods

A literature review was performed to identify studies in which chronic neuroma pain was treated with excision and processed nerve allograft reconstruction. PubMed was queried, and data from the studies were grouped into treatment effective and ineffective groups. Statistical analyses were performed on these groups, and further subgroup analysis was performed on overall change of preoperative and postoperative pain scores using a paired t test.

Results

Seven studies fulfilled inclusion criteria yielding 42 patients. Greater than 90% of patients had improvement of pain postoperatively. The preoperative and postoperative pain scores could be determined for 40 patients. The mean preoperative score was 7.9, and the mean postoperative score was 3.54. These results were statistically significant using a paired t test with a P value of <0.001.

Conclusions

Chronic pain resulting from symptomatic neuromas can be treated with neuroma excision and nerve stump reconstruction with processed nerve allograft. This obviates autograft-associated donor-site morbidity and provides a platform to potentially restore sensation to the involved nerve whenever a distal nerve end is available. Addressing the root cause is an important paradigm shift for treating symptomatic neuromas.

Relocation Nerve Grafting: A Technique for Management of Symptomatic Digital Neuromas

Digital neuromas are a common problem following amputation, often severely impairing hand function. Surgical treatment of terminal digital nerve neuroma is challenging because of the lack of surrounding soft tissue in the hand. To help tackle this problem, we describe a novel technique, "relocation nerve grafting," to relocate the nerve ends into the interosseous muscles at the midcarpal level.

Relocation Nerve Grafting: A Technique for Management of Symptomatic Digital Neuromas

Digital neuromas are a common problem following amputation, often severely impairing hand function. Surgical treatment of terminal digital nerve neuroma is challenging because of the lack of surrounding soft tissue in the hand. To help tackle this problem, we describe a novel technique, "relocation nerve grafting," to relocate the nerve ends into the interosseous muscles at the midcarpal level.

Current State of the Surgical Treatment of Terminal Neuromas

Painful terminal neuromas resulting from nerve injury following amputation are common. However, there is currently no universally accepted gold standard of treatment for this condition. A comprehensive literature review is presented on the treatment of terminal neuromas. Four categories of terminal neuroma surgical procedures are assessed: epineurial closure; nerve transposition with implantation; neurorrhaphy, and alternate target reinnervation. Significant patient and case studies are highlighted in each section, focusing on surgical technique and patient outcome metrics. Studies presented consisted of a PubMed search for "terminal neuromas," without year limitation. The current available research supports the use of implantation into muscle for the surgical treatment of terminal neuromas. However, this technique has several fundamental flaws that limit its utility, as it does not address the underlying physiology behind neuroma formation. Regenerative peripheral nerve interfaces and targeted muscle reinnervation are 2 techniques that seem to offer the most promise in preventing and treating terminal neuroma formation. Both techniques are also capable of generating control signals which can be used for both motor and sensory prosthetic control. Such technology has the potential to lead to the future restoration of lost limb function in amputees. Further clinical research employing larger patient groups with high-quality control groups and reproducible outcome measures is needed to determine the most effective and beneficial surgical treatment for terminal neuromas. Primary focus should be placed on investigating techniques that most closely approximate the theoretically ideal neuroma treatment, including targeted muscle reinnervation and regenerative peripheral nerve interfaces.

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.

Targeted Muscle Reinnervation for Prosthesis Optimization and Neuroma Management in the Setting of Transradial Amputation

Targeted muscle reinnervation (TMR) is a surgical technique that improves modern myoelectric prosthesis functionality and plays an important role in the prevention and treatment of painful postamputation neuromas. Originally described for transhumeral amputations and shoulder disarticulations, the technique is being adapted for treatment of transtibial, transfemoral, transradial, and partial hand amputees. We describe a new technique for forearm TMR following transradial amputation with an emphasis on selecting nerve transfer patterns, managing sensory nerves, improving terminal soft tissue coverage, and employing pattern recognition technology.

Targeted Muscle Reinnervation Technique in Below-Knee Amputation

Approximately 25 percent of major limb amputees will develop chronic localized symptomatic neuromas and phantom limb pain in the residual limb. A method to treat and possibly prevent these pain symptoms is targeted reinnervation. Previous studies prove that targeted reinnervation successfully treats and, in some cases, resolves peripheral neuropathy and phantom limb pain in patients who have undergone previous amputation (i.e., secondary targeted reinnervation). This article seeks to share the authors' clinical indications and surgical technique for targeted muscle reinnervation in below-knee amputation, a surgical description currently absent from our literature. Targeted reinnervation for the below-knee amputee has been performed on 22 patients at the authors' institution. Each patient has been followed on an outpatient basis for 1 year to evaluate symptoms of neuroma or phantom limb pain, patient satisfaction, and functionality. All subjects have denied neuroma pain following amputation. The majority of subjects reported phantom pain at 1 month. However, at 3 months, all patients reported resolution of this pain. Dumanian et al. first noted the improvement of symptomatic neuroma and phantom limb pain in patients undergoing targeted reinnervation to provide intuitive control of upper limb prostheses. These findings have been substantiated by multiple previous studies at various amputation levels. This study extends the success of targeted muscle reinnervation to below-knee amputations and provides a description for this technique.

Preemptive Treatment of Phantom and Residual Limb Pain with Targeted Muscle Reinnervation at the Time of Major Limb Amputation

BACKGROUND

A majority of the nearly 2 million Americans living with limb loss suffer from chronic pain in the form of neuroma-related residual limb and phantom limb pain (PLP). Targeted muscle reinnervation (TMR) surgically transfers amputated nerves to nearby motor nerves for prevention of neuroma. The objective of this study was to determine whether TMR at the time of major limb amputation decreases the incidence and severity of PLP and residual limb pain.

STUDY DESIGN

A multi-institutional cohort study was conducted between 2012 and 2018. Fifty-one patients undergoing major limb amputation with immediate TMR were compared with 438 unselected major limb amputees. Primary outcomes included an 11-point Numerical Rating Scale (NRS) and Patient-Reported Outcomes Measurement Information System (PROMIS) pain intensity, behavior, and interference.

RESULTS

Patients who underwent TMR had less PLP and residual limb pain compared with untreated amputee controls, across all subgroups and by all measures. Median "worst pain in the past 24 hours" for the TMR cohort was 1 out of 10 compared to 5 (PLP) and 4 (residual) out of 10 in the control population (p = 0.003 and p < 0.001, respectively). Median PROMIS t-scores were lower in TMR patients for both PLP (pain intensity [36.3 vs 48.3], pain behavior [50.1 vs 56.6], and pain interference [40.7 vs 55.8]) and residual limb pain (pain intensity [30.7 vs 46.8], pain behavior [36.7 vs 57.3], and pain interference [40.7 vs 57.3]). Targeted muscle reinnervation was associated with 3.03 (PLP) and 3.92 (residual) times higher odds of decreasing pain severity compared with general amputee participants.

CONCLUSIONS

Preemptive surgical intervention of amputated nerves with TMR at the time of limb loss should be strongly considered to reduce pathologic phantom limb pain and symptomatic neuroma-related residual limb pain.

Surgical Algorithm for Neuroma Management: A Changing Treatment Paradigm

Successful treatment of the painful neuroma is a particular challenge to the nerve surgeon. Historically, symptomatic neuromas have primarily been treated with excision and implantation techniques, which are inherently passive and do not address the terminal end of the nerve. Over the past decade, the surgical management of neuromas has undergone a paradigm shift synchronous with the development of contemporary techniques aiming to satisfy the nerve end. In this article, we describe the important features of surgical treatment, including the approach to diagnosis with consideration of neuroma type and the decision of partial versus complete neuroma excision. A comprehensive list of the available surgical techniques for management following neuroma excision is presented, the choice of which is often predicated upon the availability of the terminal nerve end for reconstruction. Techniques for neuroma reconstruction in the presence of an intact terminal nerve end include hollow tube reconstruction and auto- or allograft nerve reconstruction. Techniques for neuroma management in the absence of an intact or identifiable terminal nerve end include submuscular or interosseous implantation, centro-central neurorrhaphy, relocation nerve grafting, nerve cap placement, use of regenerative peripheral nerve interface, "end-to-side" neurorrhaphy, and targeted muscle reinnervation. These techniques can be further categorized into passive/ablative and active/reconstructive modalities. The nerve surgeon must be aware of available treatment options and should carefully choose the most appropriate intervention for each patient. Comparative studies are lacking and will be necessary in the future to determine the relative effectiveness of each technique.

Surgical Algorithm for Neuroma Management: A Changing Treatment Paradigm

Successful treatment of the painful neuroma is a particular challenge to the nerve surgeon. Historically, symptomatic neuromas have primarily been treated with excision and implantation techniques, which are inherently passive and do not address the terminal end of the nerve. Over the past decade, the surgical management of neuromas has undergone a paradigm shift synchronous with the development of contemporary techniques aiming to satisfy the nerve end. In this article, we describe the important features of surgical treatment, including the approach to diagnosis with consideration of neuroma type and the decision of partial versus complete neuroma excision. A comprehensive list of the available surgical techniques for management following neuroma excision is presented, the choice of which is often predicated upon the availability of the terminal nerve end for reconstruction. Techniques for neuroma reconstruction in the presence of an intact terminal nerve end include hollow tube reconstruction and auto- or allograft nerve reconstruction. Techniques for neuroma management in the absence of an intact or identifiable terminal nerve end include submuscular or interosseous implantation, centro-central neurorrhaphy, relocation nerve grafting, nerve cap placement, use of regenerative peripheral nerve interface, “end-to-side” neurorrhaphy, and targeted muscle reinnervation. These techniques can be further categorized into passive/ablative and active/reconstructive modalities. The nerve surgeon must be aware of available treatment options and should carefully choose the most appropriate intervention for each patient. Comparative studies are lacking and will be necessary in the future to determine the relative effectiveness of each technique.

Targeted muscle reinnervation and prosthetic rehabilitation after limb loss

Over one million amputations occur annually world-wide. Often, amputation of the neoplastic limb is regarded as a surgical failure and the end of surgical care for the patient. Here, we highlight the advancements in extremity prostheses and surgical techniques that should change that mindset. Myoelectric prostheses, osseointegration, and targeted muscle reinnervation allow for more intuitive and easy to use devices, reduced pain, and greater quality of life for amputees.