Targeted muscle reinnervation at the time of amputation in the management of complex regional pain syndrome of the lower extremity

Targeted Muscle Reinnervation and Regenerative Peripheral Nerve Interfaces Versus Standard Management in the Treatment of Limb Amputation: A Systematic Review and Meta-Analysis

Introduction: Painful neuromas are a common postoperative complication of limb amputation often treated with secondary reinnervation. Surgical reinnervation include Targeted Muscle Reinnervation (TMR) and Regenerative Peripheral Nerve Interface (RPNI), and can be primary and secondary. The aim of this review is to assess the effects of primary TMR/RPNI at the time of limb amputation on the incidence and intensity of post-operative neuroma and pain. Methods: This review was registered a priori on PROSPERO (CRD42021264360). A search of the following databases was performed in June 2021: Medline, EMBASE, and CENTRAL. Unpublished trials were searched using clinicaltrials.gov. All randomized and non-randomized studies assessing amputation with a reinnervation strategy (TMR, RPNI) were included. Outcomes evaluated included the incidences of painful neuroma, phantom limb pain (PLP), residual limb pain (RLP), as well as severity of pain, and Pain intensity, behavior, and interference (PROMIS). Results: Eleven studies were included in this systematic review, and five observational studies for quantitative synthesis. Observational study evidence suggests that TMR/RPNI results in a statistically significant reduction in incidence, pain scores and PROMIS scores of PLP and RLP. Decreased incidence of neuromas favored primary TMR/RPNI, but this did not achieve statistical significance (p = 0.07). Included studies had moderate to critical risk of bias. Conclusion: The observational data suggests that primary TMR/RPNI reduces incidence, pain scores and PROMIS scores of PLP and RLP. Going forward, randomized trials are warranted to evaluate this research question, particularly to improve the certainty of evidence.

The effectiveness of targeted muscle reinnervation in reducing pain and improving quality of life for patients following lower limb amputation

BACKGROUND

Globally, over 1 million lower limb amputations are performed annually, with approximately 75% of patients experiencing significant pain, profoundly impacting their quality of life and functional capabilities. Targeted muscle reinnervation (TMR) has emerged as a surgical solution involving the rerouting of amputated nerves to specific muscle targets. Originally introduced to enhance signal amplification for myoelectric prosthesis control, TMR has expanded its applications to include neuroma management and pain relief. However, the literature assessing patient outcomes is lacking, specifically for lower limb amputees. This systematic review aims to assess the effectiveness of TMR in reducing pain and enhancing functional outcomes for patients who have undergone lower limb amputation.

METHODS

A systematic review was performed by examining relevant studies between 2010 and 2023, focusing on pain reduction, functional outcomes and patient-reported quality of life measures.

RESULTS

In total, 20 studies were eligible encompassing a total of 778 extremities, of which 75.06% (n = 584) were lower limb amputees. Average age was 46.66 years and patients were predominantly male (n = 70.67%). Seven studies (35%) reported functional outcomes. Patients who underwent primary TMR exhibited lower average patient-reported outcome measurement information system (PROMIS) scores for phantom limb pain (PLP) and residual limb pain (RLP). Secondary TMR led to improvements in PLP, RLP and general limb pain as indicated by average numeric rating scale and PROMIS scores.

CONCLUSION

The systematic review underscores TMR's potential benefits in alleviating pain, fostering post-amputation rehabilitation and enhancing overall well-being for lower limb amputees.

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

BACKGROUND

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

METHODS

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

RESULTS

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

CONCLUSION

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

Targeted muscle reinnervation and regenerative peripheral nerve interfaces for pain prophylaxis and treatment: A systematic review

OBJECTIVE

Nerve pain frequently develops following amputations and peripheral nerve injuries. Two innovative surgical techniques, targeted muscle reinnervation (TMR) and regenerative peripheral nerve interfaces (RPNI), are rapidly gaining popularity as alternatives to traditional nerve management, but their effectiveness is unclear.

LITERATURE SURVEY

A review of literature pertaining to TMR and RPNI pain results was conducted. PubMed and MEDLINE electronic databases were queried.

METHODOLOGY

Studies were included if pain outcomes were assessed after TMR or RPNI in the upper or lower extremity, both for prophylaxis performed at the time of amputation and for treatment of postamputation pain. Data were extracted for evaluation.

SYNTHESIS

Seventeen studies were included, with 14 evaluating TMR (366 patients) and three evaluating RPNI (75 patients). Of these, one study was a randomized controlled trial. Nine studies had a mean follow-up time of at least 1 year (range 4-27.6 months). For pain treatment, TMR and RPNI improved neuroma pain in 75%-100% of patients and phantom limb pain in 45%-80% of patients, averaging a 2.4-6.2-point reduction in pain scores on the numeric rating scale postoperatively. When TMR or RPNI was performed prophylactically, many patients reported no neuroma pain (48%-100%) or phantom limb pain (45%-87%) at time of follow-up. Six TMR studies reported Patient-Reported Outcomes Measurement Information System (PROMIS) scores assessing pain intensity, behavior, and interference, which consistently showed a benefit for all measures. Complication rates ranged from 13% to 31%, most frequently delayed wound healing.

CONCLUSIONS

Both TMR and RPNI may be beneficial for preventing and treating pain originating from peripheral nerve dysfunction compared to traditional techniques. Randomized trials with longer term follow-up are needed to directly compare the effectiveness of TMR and RPNI with traditional nerve management techniques.

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

BACKGROUND

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

METHODS

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

RESULTS

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

CONCLUSIONS

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

Management of complex regional pain syndrome in trauma and orthopaedic surgery-a systematic review

INTRODUCTION

Complex regional pain syndrome (CRPS) is a neurological pain disorder that is challenging to diagnose and manage, resulting in increased morbidity and costs. It most commonly occurs following traumatic injury, such as a fracture, crush injury or surgery. Recent research has evaluated the efficacy of treatments which have contradicted previous hypotheses. This systematic review summarizes these findings to improve clinician's decision-making.

SOURCES OF DATA

A comprehensive search of PubMed, MEDLINE and Embase databases from inception through January 2021 was performed in accordance with Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines. Two reviewers independently screened relevant articles discussing the management of CRPS in adult trauma patients. All prospective and retrospective studies, non-randomized comparison studies and case series were considered for inclusion. Data extraction was performed by populating a predefined data abstraction sheet.

AREAS OF AGREEMENT

There is strong evidence to suggest the efficacy of prompt physiotherapy, lidocaine, ketamine, bisphosphonates, sympathectomy and brachial plexus blocks in the management of CRPS.

AREAS OF CONTROVERSY

The latest evidence suggests that vitamin C has no significant role to play in the treatment or prevention of CRPS.

GROWING POINTS

A multidisciplinary team approach and early diagnosis are imperative for successful treatment of CRPS. The Budapest criteria and the British Orthopaedic Association Standards for Trauma and Orthopaedics (BOAST) guidelines should be used when diagnosing CRPS. There is currently no clear evidence of superiority in any treatment.

AREAS TIMELY FOR DEVELOPING RESEARCH

There are few high-quality studies that inform the best treatment modalities for CRPS. Though emerging treatments show promise, further research is needed.

Feasibility for Immediate Targeted Muscle Reinnervation Based on Lower Extremity Amputations Trends

Targeted muscle reinnervation has been adopted as a strategy for the management and prevention of phantom limb pain and symptomatic neuroma formation for patients undergoing lower extremity amputation. The procedure is often performed by surgeons different from those performing the amputation, creating scheduling dilemmas. The purpose of this study was to analyze historic trends in lower extremity amputation scheduling in a single hospital system to evaluate if offering routine immediate targeted muscle reinnervation is practical.

Methods

De-identified data over a five-year period for all patients undergoing lower extremity amputation were collected. The data gathered included the specialty performing the amputation, weekly distribution of cases, start time, and end time, among others.

Results

A total of 1549 lower extremity amputations were performed. There was no statistically significant difference in average number of below-the-knee amputations (172.8) and above-the-knee amputations (137.4) per year. Top specialties performing amputations were vascular surgery (47.8%), orthopedic surgery (34.5%), and general surgery (13.85%). No significant difference was noted in the average number of amputations across the week, per year. Most cases started between 6 am and 6 pm (96.4%). The average length of stay after surgery was 8.26 days.

Conclusions

In a large, nontrauma hospital system, most lower extremity amputations are performed during typical working hours and are evenly distributed throughout the week. Understanding peak timing of amputations may allow for targeted muscle reinnervation to be performed concurrently with amputation procedure. Data presented will be a first step to optimizing amputation scheduling for patients in a large nontrauma health system.

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

Targeted muscle reinnervation (TMR) outcome studies reveal the benefit amputees experience and the potential functional improvement by optimizing neurocutaneous signaling for myoelectric prosthesis control. However, there are still many settings where these techniques are not offered to patients requiring lower extremity amputations or neuroma reconstruction. With growing consistency in the literature, it is helpful to systematize the nerve transfers described for lower extremity TMR and to simplify its integration into reconstructive care.

Methods

A systematic literature review was performed and contained the following inclusion criteria: original cases of primary or secondary lower extremity amputation defects or nerve-related pain that underwent TMR with clearly described target muscles for each nerve transfer. Studies were excluded if the cases had been previously described or contained incomplete data. The primary outcomes were nerves transferred and muscles targeted. Target muscle options were presented in tables specific to anatomic region, and cross-sectional schematics were created for intraoperative assistance.

Results

Seventeen studies presenting original cases with clearly described nerve transfers and target muscles in the lower extremity were included in the review. Target muscle selection for all nerve transfers at the transfemoral and transtibial levels were presented in separate tables.

Conclusions

Reports of early experience at multiple institutions identify trends in the selection of certain target muscles for nerve transfers in transfemoral and transtibial TMR. Familiarity with these common target muscles and nerve transfers can simplify intraoperative decision-making and enhance integration of lower extremity TMR in amputation care and in the treatment of nerve-related pain.

The Current State of Targeted Muscle Reinnervation: A Systematic Review

BACKGROUND

 Targeted muscle reinnervation (TMR) is growing in popularity; however, literature evaluating patient characteristics and outcomes is limited.

METHODS

 The EMBASE database was queried with the search terms "targeted muscle reinnervation" OR "TMR" AND "outcomes" OR "patient outcomes." Clinical human studies in English were eligible for inclusion, yielding 89 articles. After rigorous exclusion criteria, a total of 13 articles were included in this review. Study data including geographic location, patient demographics, TMR indication, amputation level, number of nerve transfers performed, length of follow-up, and reported outcomes were extracted and analyzed.

RESULTS

 The included articles represent 338 patients (341 limbs). Average patient age was 47.4 years. Indication for amputation included trauma (n = 125), infection (n = 76) cancer/tumor resection (n = 71), ischemia (n = 18), failed Charcot reconstruction (n = 15), failed hardware (n = 9), burn (n = 4), and CRPS (n = 4). Five studies included upper extremity TMR only, two included lower extremity TMR only, and six included both upper and lower extremity TMR. TMR was performed in an immediate or delayed fashion, with an average of 2.2 nerve transfers performed per limb overall. Average length of follow-up was 22.3 months. In three studies, patients with phantom limb pain undergoing delayed TMR were found to have significant or trending toward significant reduction in pain after TMR using numeric rating scale and patient-reported outcomes measurement information system scales. One article reported 9/10 patients with improved or complete resolution of phantom limb pain after delayed TMR. Three studies found that patients undergoing immediate TMR had lower pain scores compared with non-TMR controls.

CONCLUSION

 While there is evidence that TMR reduces neuroma-related pain and improves the quality of life for amputees, further outcomes studies are needed to study the patient experience with TMR on a larger scale. Establishing standardized, validated patient-reported outcomes assessment tools is critical to future investigation in this field.

Controlling axonal regeneration with acellular nerve allograft limits neuroma formation in peripheral nerve transection: An experimental study in a swine model

BACKGROUND

Symptomatic neuromata are a common indication for revision surgery following amputation. Previously described treatments, including traction neurectomy, nerve transposition, targeted muscle re-innervation, and nerve capping, have provided inconsistent results or are technically challenging. Prior research using acellular nerve allografts (ANA) has shown controlled termination of axonal regrowth in long grafts. The purpose of this study was to determine the ability of a long ANA to prevent neuroma formation following transection of a peripheral nerve in a swine model.

MATERIALS AND METHODS

Twenty-two adult female Yucatan miniature swine (Sus scrofa; 4-6 months, 15-25 kg) were assigned to control (ulnar nerve transection only, n = 10), treatment (ulnar transection and coaptation of 50 mm ANA, n = 10), or donor (n = 2) groups. Nerves harvested from donor group animals were treated to create the ANA. After 20 weeks, the transected nerves including any neuroma or graft were harvested. Both qualitative (nerve architecture, axonal sprouting) and quantitative histologic analyses (myelinated axon number, cross sectional area of nerve tissue) were performed.

RESULTS

Qualitative histologic analysis of control specimens revealed robust axon growth into dense scar tissue. In contrast, the treatment group revealed dwindling axons in the terminal tissue, consistent with attenuated neuroma formation. Quantitative analysis revealed a significantly decreased number of myelinated axons in the treatment group (1232 ± 540) compared to the control group (44,380 ± 7204) (p < .0001). Cross sectional area of nerve tissue was significantly smaller in treatment group (2.83 ± 1.53 mm² ) compared to the control group (9.14 ± 1.19 mm² ) (p = .0012).

CONCLUSIONS

Aberrant axonal growth is controlled to termination with coaptation of a 50 mm ANA in a swine model of nerve injury. These early results suggest further investigation of this technique to prevent and/or treat neuroma formation.

An Algorithm for Elective Amputation Combined with Targeted Muscle Reinnervation in Complex Regional Pain Syndrome—A Perspective

Complex regional pain syndrome (CRPS) can result in a devastating condition. For a small number of patients, there is a non-response to any existing multimodal therapies and they ultimately request amputation. Such a drastic and final decision is not easy to take for both the patient and the surgeon and requires careful and interdisciplinary assessments and considerations. Furthermore, new surgical procedures, such as targeted muscle reinnervation (TMR) and hybrid prosthetic fitting, and multidisciplinary board advice should be included when considering amputation. In order to help other therapeutic teams in decision making for such rare but more than demanding cases, we aimed to propose an advanced algorithm for amputation indications in CRPS patients combining all these new factors. This algorithm consists of extensive pre-operative psychiatric assessment, diagnostic hybrid prosthetic fitting including fMRI analyses, multidisciplinary board advice as well as targeted muscle reinnervation and amputation procedures with final prosthetic fitting and rehabilitation. By involving multiple disciplines, this algorithm should provide optimized and individualized patient treatment on the one hand and a reliable base for decision making for therapists on the other.

Five-year outcome in chronic regional pain syndrome patient with below knee amputation, implanting nerves into muscle: A case report

Persistent, disabling lower extremity pain, outside the distribution of a single nerve, is termed chronic regional pain syndrome (CRPS), but, in reality, this chronic pain is often due to multiple peripheral nerve injuries. It is the purpose of this report to describe the first application of the "traditional," nerve implantation into muscle, usually used in the treatment of a painful neuroma, as a pre-emptive surgical technique in doing a below knee amputation (BKA). In 2011, a 51-year-old woman developed severe, disabling CRPS, after a series of operations to treat an enchondroma of the left fifth metatarsal. When appropriate peripheral nerve surgeries failed to relieve distal pain, a BKA was elected. The approach to the BKA included implantation of each transected peripheral nerve directly into an adjacent muscle. At 5.0 years after the patient's BKA, the woman reported full use of this extremity, using the prosthesis, and was free of phantom limb and residual limb pain. This anecdotal experience gives insight that long-term relief of lower extremity CRPS can be achieved by a traditional BKA utilizing the approach of implanting each transected nerve into an adjacent muscle.

Biologic Augmentation of Tibiotalocalcaneal Arthrodesis With Allogeneic Bone Block Is Associated With High Rates of Fusion

BACKGROUND

The orthopaedic conditions and systemic comorbidities that occur in patients who require bone block tibiotalocalcaneal (TTC) arthrodesis have made this procedure associated with a higher-than-normal risk of nonunion, graft collapse, hardware failure, and amputation. Here, we present a novel approach to bone block TTC arthrodesis using adjunctive osteoinductive agents and a prolonged course of protected weightbearing to assess if we could improve on historical outcomes. We also evaluated the efficacy of a vascularized medial femoral condyle (MFC) free flap to augment TTC arthrodesis.

METHODS

Fourteen adult patients underwent bone block TTC arthrodesis biologically augmented with fresh-frozen femoral head allograft, bone marrow aspirate concentrate, and demineralized bone matrix cortical fibers. Three patients with soft tissue defects underwent vascularized reconstruction with an MFC free flap. Radiographic union, the Foot Function Index (FFI), and PROMIS pain interference (PI), and physical function (PF) scores were assessed at follow-up.

RESULTS

TTC fusion was documented on plain radiograph in 13 of 14 patients (92.9%) and CT in 10 of 11 patients (90.9%). Mean time to fusion was 183.2 ± 83.2 days. One patient (7.1%) experienced nonunion and persistent infection requiring amputation. Patients who underwent vascularized bone grafting had significantly shorter time to fusion (112.3 ± 31.7 days vs 204.4 ± 82.7 days, P = .05). Patient-reported outcomes revealed mild to moderate pain and dysfunction after 1 year (mean FFI = 41.0% ± 23.1%, PROMIS PI = 58.3 ± 1.8, PROMIS PF = 39.0 ± 2.2).

CONCLUSION

In this relatively small series, the biologic augmentation of bone block TTC arthrodesis with osteoinductive agents and protective weightbearing resulted in excellent rates of fusion, modest pain, and preserved function of the lower extremity in almost all those treated. Osseous healing appears to be enhanced and accelerated with application of an MFC flap. We believe that this approach offers a viable salvage option for these challenging clinical problems.

LEVEL OF EVIDENCE

Level IV, case series.

Complex Regional Pain Syndrome: A Comprehensive Review

Complex regional pain syndrome (CRPS) is a chronic pain condition often involving hyperalgesia and allodynia of the extremities. CRPS is divided into CRPS-I and CRPS-II. Type I occurs when there is no confirmed nerve injury. Type II is when there is known associated nerve injury. Female gender is a risk factor for developing CRPS. Other risk factors include fibromyalgia and rheumatoid arthritis. Unfortunately, the pathogenesis of CRPS is not yet clarified. Some studies have demonstrated different potential pathways. Neuropathic inflammation, specifically activation of peripheral nociceptors of C-fibers, has been shown to play a critical role in developing CRPS. The autonomic nervous system (ANS) is involved. Depending on whether it is acute or chronic CRPS, norepinephrine levels are either decreased or increased, respectively. Some studies have suggested the importance of genetics in developing CRPS. More consideration is being given to the role of psychological factors. Some association between a history of depression and/or post-traumatic stress disorder (PTSD) and the diagnosis of CRPS has been demonstrated. Treatment modalities available range from physical therapy, pharmacotherapy, and interventional techniques. Physical and occupational therapies include mirror therapy and graded motor imagery. Medical management with non-steroidal anti-inflammatory drugs (NSAIDs) has not shown significant improvement. There have been supporting findings in the use of short-course steroids, bisphosphonates, gabapentin, and ketamine. Antioxidant treatment has also shown some promise. Other pharmacotherapies include low-dose naltrexone and Botulinum toxin A (BTX-A). Sympathetic blocks are routinely used, even if their short- and long-term effects are not clear. Finally, spinal cord stimulation (SCS) has been used for decades. In conclusion, CRPS is a multifactorial condition that still requires further studying to better understand its pathogenesis, epidemiology, genetic involvement, psychological implications, and treatment options. Future studies are warranted to better understand this syndrome. This will provide an opportunity for better prevention, diagnosis, and treatment of CRPS.