Targeted Muscle Reinnervation Research Articles

Targeted Muscle Reinnervation in the Hand: A Technical Roadmap

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

Targeted Muscle Reinnervation in Partial Hand Amputations.

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

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

Where Are We Now? Surgeons have changed how they manage patients with malignant tumors of the extremities over the last four decades, with the largest transition being the switch to limb salvage rather than amputation for the large majority of patients with bone sarcomas [8, 10, 12]. Indeed, modern day decision-making generally favors limb salvage in the absence of a specific contraindication [8]. Still, because some patients will undergo amputations, surgeons continue to try to improve how we perform these procedures. Areas of focus include amputation techniques as well as methods of preventing phantom limb pain and neuromas; generally, these studies focus on patient-reported outcomes and healthcare-related quality of life [3, 13]. Some of the more exciting discoveries have been on the topic of preventing nerve-related pain using targeted muscle reinnervation (TMR) [6], regenerative peripheral nerve interfaces (RPNI) [5], as well as other neuroma revision and prevention concepts. The current study by Döring et al. [2] is important because it focuses on the long-term outcomes and complications from the subset of patients who may not be good candidates for limb salvage. Where Do We Need To Go? Nerve-associated pain and associated sequelae can lead to poor functional outcomes and decreased mobility and prosthetic use. Research focused on minimizing these complications is an essential next step to improving function and quality of life for patients with sarcoma and limb loss. Although TMR was originally conceived of to allow autonomous zones for myoelectric prosthesis use in the upper extremity, the added benefit of decreased phantom limb pain and neuroma formation has made it an appealing technique for the lower extremity as well. A concern for TMR is that a specialized team is usually required to complete the procedure and it can increase OR time [5, 6]. RPNI has also shown excellent potential for prevention of these same nerve-related sequelae [5], and it is technically simpler and potentially easier for a wider range of surgeons. While TMR seems to have the best outcomes, it may not be a reality for widespread clinical use (due to the need for specialized teams to perform the procedure). In contrast, RPNI may be more practical because it can be performed by a non-hand surgery–trained surgeon. Well-designed studies looking at the two techniques prospectively are still needed. We also need to determine the impact each technique has on long-term pain and amputee function. Döring et al. [2] provide long-term functional and quality-of-life data for patients with amputation, which can serve as a baseline for future studies focused on amputation techniques. A large proportion of amputation-related studies focus on populations with the highest rates of amputation. This includes older patients with diabetes- or peripheral vascular disease–related complications [3, 13] as well as military and traumatic amputations [4, 11]. While these data are valuable, younger patients with sarcoma are quite different than those patient populations. Therefore, future research should focus on this younger patient group since those who survive their tumors would be expected to have both long life expectancy and high functional demands [9]. How Do We Get There? Due to the rarity of amputation for sarcoma in a younger population, a well-designed multicenter study comparing TMR and RPNI techniques would be a valuable collaborative effort. One study [1], which was the largest oncologic cohort to date (31 patients from a single institution treated with TMR for oncologic amputation), found that on short-term follow-up (1 year), the study group compared favorably to the control group, whose data were collected from a national amputee database. Building off of this study, researchers should compare TMR versus RPNI in a prospective study and include patient-reported as well as functional outcomes with a focus on prosthesis use [7]. Patient-reported outcomes and prosthesis use can be compared at 1, 3, and 5 years to definitively compare the techniques. Modern day prosthetic fitting and technology use should be integrated into this study, as well as a detailed cost analysis that examines the differences in resource requirements for the two techniques.

Surgical Treatment of Abdominal Wall Neuromas.

Background:Neuromas are an under-recognized contributor to chronic abdominal pain. Other than after mesh inguinal hernia repair, surgical management of painful abdominal wall neuromas has not been well established in the literature.Methods:All patients who underwent surgical treatment for painful abdominal wall neuromas by the senior author at Northwestern Memorial Hospital were reviewed. Patients were treated with neuroma excision and allograft nerve reconstruction and/or with targeted muscle reinnervation (TMR). Follow-up pain surveys were issued to assess pain levels, activities of daily living, and pain medication usage.Results:Twenty patients met inclusion criteria. Eighteen (90%) patients reported improvement in neuropathic pain postoperatively. Two (10%) patients had TMR following failed nerve allograft reconstruction, which led to complete pain resolution. Twenty-seven nerves were treated surgically, the majority of which were abdominal intercostal (13), followed by ilioinguinal (10), genitofemoral (3), and iliohypogastric (1). Nerve allograft reconstruction was used alone for 18 procedures, in combination with TMR for 2, and TMR was used alone in 8. In all cases of TMR, the freshened nerve ending after neuroma excision was coapted to a motor nerve of the internal oblique. The mean length of follow-up was 18.9 months (SD ±14.5).Conclusions:This retrospective review demonstrated that 90% (18) of the patients had significant improvement in abdominal neuroma pain postoperatively. These results may help guide providers toward effective management of abdominal wall neuropathic pain.

Efficacy of targeted muscle reinnervation is directly affected by timing of intervention in a neuropathic pain model

Purpose Targeted muscle reinnervation (TMR) coapts amputated nerves to small motor nerves to power a prosthetic limb. Additionally, clinical studies have shown TMR performed within 3 months of major limb amputation prevents or reduces phantom and residual limb pain. However, TMR delayed over 3 months is much less effective. We have previously shown that TMR performed 3 weeks following SNI returned pain behaviors to baseline. This study examined the effect of TMR performed at the time of TMR versus a delay of 12 weeks following SNI to determine whether this model reflects clinical findings. SNI was performed in male rats and interventions were applied at the time of SNI, 3 weeks, and 12 weeks following SNI. Pain behaviors were assessed with von Frey threshold, pin testing, dynamic brush testing and acetone testing prior to intervention and at 1, 3, 6, and 12 weeks following intervention. Simple neuroma excision (NE) was used as a control intervention. TMR performed immediately at the time of SNI prevented the development of a pain phenotype. Animals tested 3 and 12 weeks following SNI showed a robust pain phenotype: increased hyperalgesic responses, reduced Von Frey thresholds, and increased cold sensitivity. TMR at 3 weeks following SNI successfully reversed the pain behaviors to baseline. In contrast, if TMR or NE was delayed 12 weeks after SNI, the pain behaviors persisted. The neuropathic pain phenotype generated by SNI can be treated with TMR performed immediately and 3 weeks following development of a pain phenotype. In contrast, delayed TMR provides no relief of pain behaviors. This model closely corresponds to clinical experience in patients with limb amputation and will facilitate further understanding of the mechanisms behind TMR and how the intervention may be modified to help chronic amputation-related pain. Medical College of Wisconsin Neurosciences Research Center Plastic Surgery Foundation- American Association for Hand Surgery Pilot Grant 628811.

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.

Cautious Enthusiasm: The Role of Targeted Muscle Reinnervation and Regenerative Peripheral Nerve Interface in the Treatment of Nerve-Related Amputation Pain: Commentary on an article by Benjamin W. Hoyt, MD, et al.: "Practice Patterns and Pain Outcomes for Targeted Muscle Reinnervation. An Informed Approach to Targeted Muscle Reinnervation Use in the Acute Amputation Setting".

Cautious Enthusiasm: The Role of Targeted Muscle Reinnervation and Regenerative Peripheral Nerve Interface in the Treatment of Nerve-Related Amputation Pain: Commentary on an article by Benjamin W. Hoyt, MD, et al.: "Practice Patterns and Pain Outcomes for Targeted Muscle Reinnervation. An Informed Approach to Targeted Muscle Reinnervation Use in the Acute Amputation Setting".

Targeted Peripheral Nerve Interface: Case Report with Literature Review

SummaryNerve transection injuries can result in painful neuromas that adversely affect patient recovery. This is especially significant following amputation surgeries in the setting of prosthetic wear and function. Targeted Muscle Reinnervation and Regenerative Peripheral Nerve Interface (RPNI) are 2 modern surgical techniques that provide neuromuscular targets for these transected nerve endings to reinnervate. These strategies have been previously shown to reduce phantom limb pain, residual limb pain, and neuroma-related pain.1,2,7,11 Two recent articles described technical adaptations of combining targeted muscle reinnervation and RPNI to create a hybrid procedure.3,12 In this article, we propose a different modification of targeted muscle reinnervation and RPNI, where the transected nerve stump is coapted to a recipient unit consisting of an intact distal nerve branch with its associated muscle graft. We called this recipient unit a targeted peripheral nerve interface because it contains a distal nerve branch for nerve coaptation and can guide axonal regeneration from the donor nerve to its target muscle graft. We theorize that targeted peripheral nerve interface may lead to more even distribution of regenerating axons with potentially less pain and stronger signals for prosthetic control when compared with standard RPNI.

Expeditionary Plastic Surgery: Reconstruction Pearls for the Non-plastic Surgeon Managing Injured Host Nationals

This review focuses on techniques for reconstructing soft tissue injuries in host nationals that can be performed by non-plastic surgeons in a deployed environment. Advances in wound care technology and techniques have created opportunities to bring world-class care to injured host nationals. Negative pressure wound therapy with instillation can reduce bacterial bioburden, decrease the number of operative debridements, and decrease time to wound closure, saving scarce resources in a deployed setting. Perforator-based pedicle flaps can be utilized to cover large soft tissue defects with minimal donor site morbidity and excellent flap survival. Targeted muscle reinnervation can be performed at the time of an amputation to decrease chronic neuropathic pain. Techniques from simple to complex can be learned and successfully performed by the general, trauma, and orthopedic surgeons in austere locations in order to effectively leverage limited resources for the best outcomes for host nationals.

561 Bilateral Upper Extremity Amputation After High Voltage Electrical Injury: A Case Report

Abstract Introduction Electrical injuries represent 0.4–3.2% of admissions to burn units and are responsible for >500 deaths per year in the United States. Approximately half occur in the workplace and are the fourth leading cause of work-related-traumatic death. The extent of injury can be drastically underestimated by total body surface area percentage (TBSA). Along with cutaneous burns, high voltage electrical injuries can lead to necrosis of muscle, bone, nervous tissue, and blood vessels. Aggressive management allows for patient survival, but at significant cost. Newer technologic advances help improve functional outcomes. Methods This case-report was conducted via retrospective chart review of the case presented. Results A 43-year-old male sustained a HVEI (>10, 000 V) after contacting an active wire while working as a linesman for an electric company. He presented after less than 15-minute transport from an outside hospital with full thickness burns and auto-amputation to all fingers on both hands and the distal third of the left hand (Images 1 and 2). There were full thickness circumferential burns to the entire left and right upper extremities with contractures, with the burns extending into the axilla, and chest wall musculature. The patient had 4th degree burns and a large wound to the left shoulder with posterior extension to the scapula, flank and back with approximately 25% TBSA (Image 3). Compartments were tense in both upper extremities. Patient was sedated and intubated to protect the airway and placed on mechanical ventilation. A femoral central line was then placed, and the patient was given pain control, continued fluid resuscitation, and blood products. Dark red colored urine from a foley catheter that was immediately identified as rhabdomyolysis induced myoglobinuria. Labs drawn demonstrated elevated troponin I, CK >40,000. BUN 18, creatinine 1.0, K+ 5.2 and phosphate 5.6. Decision was made immediately for operative intervention with emergent amputation of both upper extremities in the light of rhabdomyolysis secondary to tissue necrosis and oliguria. During the patient’s hospital course, he underwent multiple operations for further debridement with vacuum-assisted closure therapy and skin grafting of sites, as well as targeted muscle reinnervation (TMR) 6 months later at an outside hospital. Conclusions Although HVEI only account for a small percentage of burn admissions, they are associated with greater morbidity than low-voltage injuries. Patients with HVEI often incur multiple injuries, more surgical procedures, have higher rates of complications, and more long term psychological and rehabilitative difficulties. Despite the need for amputation in some of these critically ill patients, options exist that allow for them to obtain long term functional success.

Osseointegrated prostheses for lower limb amputees

Background: Traditional socket-based prostheses are an important rehabilitation tool in lower limb amputation, however, patients often experience skin-related problems, pain, stump volume fluctuations and poor suspension. Osseointegration offers a suitable alternative by providing direct skeletal attachment for limb prosthesis. This study aims to review the complications following osseointegration for lower limb amputation, with attention to mechanical abutment failure. Method: A retrospective chart review was undertaken of all patients who underwent transfemoral osseointegration between January 2000 and June 2019 through the osseointegration and targeted muscle reinnervation surgical and rehabilitation program at The Alfred in Victoria, Australia. Ethics approval was obtained through The Alfred’s ethics committee (414/16). In 2016 this program was redesigned and in 2017 the osseointegration implant system was modified. Patients underwent a two-stage surgical procedure followed by a rehabilitation protocol that gradually increased their activity. Results: A total of 19 limbs were osseointegrated in 18 patients during the study period. Two patients had their implant removed due to failure of osseointegration. The most common complication was a mechanical abutment failure, occurring 46 times in 11 patients. Patients who suffered an abutment failure reported higher levels of postoperative activity. Soft-tissue infections occurred in five patients: three superficial skin infections and two collections. There were no mechanical abutment failures noted in the updated program.Conclusion: Osseointegration is a good option for patients who may have difficulties with traditional socket prosthesis. However, complications such as abutment fracture can occur, and appropriate patient selection and counselling are required

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

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

Extended home use of an advanced osseointegrated prosthetic arm improves function, performance, and control efficiency

Objective. Full restoration of arm function using a prosthesis remains a grand challenge; however, advances in robotic hardware, surgical interventions, and machine learning are bringing seamless human-machine interfacing closer to reality. Approach. Through extensive data logging over 1 year, we monitored at-home use of the dexterous Modular Prosthetic Limb controlled through pattern recognition of electromyography (EMG) by an individual with a transhumeral amputation, targeted muscle reinnervation, and osseointegration (OI). Main results. Throughout the study, continuous prosthesis usage increased (1% per week, p < 0.001) and functional metrics improved up to 26% on control assessments and 76% on perceived workload evaluations. We observed increases in torque loading on the OI implant (up to 12.5% every month, p < 0.001) and prosthesis control performance (0.5% every month, p < 0.005), indicating enhanced user integration, acceptance, and proficiency. More importantly, the EMG signal magnitude necessary for prosthesis control decreased, up to 34.7% (p < 0.001), over time without degrading performance, demonstrating improved control efficiency with a machine learning-based myoelectric pattern recognition algorithm. The participant controlled the prosthesis up to one month without updating the pattern recognition algorithm. The participant customized prosthesis movements to perform specific tasks, such as individual finger control for piano playing and hand gestures for communication, which likely contributed to continued usage. Significance. This work demonstrates, in a single participant, the functional benefit of unconstrained use of a highly anthropomorphic prosthetic limb over an extended period. While hurdles remain for widespread use, including device reliability, results replication, and technical maturity beyond a prototype, this study offers insight as an example of the impact of advanced prosthesis technology for rehabilitation outside the laboratory.

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 J2021;103-B(3):430-439.

Practice Patterns and Pain Outcomes for Targeted Muscle Reinnervation

Targeted muscle reinnervation (TMR) and regenerative peripheral nerve interface (RPNI) procedures have been shown to improve patient-reported outcomes for the treatment of symptomatic neuromas after amputation; however, the specific indications and comparative outcomes of each are unclear. The primary research questions were what complement of nerves most frequently requires secondary pain intervention after conventional amputation, whether this information can guide the focused application of TMR and RPNI to the primary amputation setting, and how the outcomes compare in both settings. We performed a retrospective review of records for patients who had undergone lower-extremity TMR and/or RPNI at our institution. Eighty-seven procedures were performed: 59 for the secondary treatment of symptomatic neuroma pain after amputation and 28 for primary prophylaxis during amputation. We reviewed records for the amputation level, TMR and/or RPNI timing, pain scores, patient-reported resolution of nerve-related symptoms, and complications or revisions. We evaluated the relationship between the amputation level and the frequency with which each transected nerve required neurologic intervention for pain symptoms. The mean pain score decreased after delayed TMR or RPNI procedures from 4.3 points to 1.7 points (p < 0.001), and the mean final pain score (and standard deviation) was 1.0 ± 1.9 points at the time of follow-up for acute procedures. Symptom resolution was achieved in 92% of patients. The sciatic nerve most commonly required intervention for symptomatic neuroma above the knee, and the tibial nerve and common or superficial peroneal nerve were most problematic following transtibial amputation. None of our patients required a revision pain treatment procedure after primary TMR targeting these commonly symptomatic nerves. Failure to address the tibial nerve during a delayed procedure was associated with an increased risk of unsuccessful TMR, resulting in a revision surgical procedure (odds ratio, 26 [95% confidence interval, 1.8 to 368]; p = 0.02). There is a consistent pattern of symptomatic nerves that require secondary surgical intervention for the management of pain after amputation. TMR and RPNI were translated to the primary amputation setting by using this predictable pattern to devise a surgical strategy that prevents symptomatic neuroma pain. Therapeutic Level IV. See Instructions for Authors for a complete description of levels of evidence.

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

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

Defining the relative impact of muscle versus Schwann cell denervation on functional recovery after delayed nerve repair

Functional recovery following peripheral nerve injury worsens with increasing durations of delay prior to repair. From the time of injury until re-innervation occurs, denervated muscle undergoes progressive atrophy that limits the extent to which motor function can be restored. Similarly, Schwann cells (SC) in the distal nerve lacking axonal interaction progressively lose their capacity to proliferate and support regenerating axons. The relative contributions of these processes to diminished functional recovery is unclear.We developed a novel rat model to isolate the effects of SC vs. muscle denervation on functional recovery. Four different groups underwent the following interventions for 12 weeks prior to nerve transfer: 1) muscle denervation; 2) SC denervation; 3) muscle + SC denervation (negative control); 4) no denervation (positive control). Functional recovery was measured weekly using the stimulated grip strength testing (SGST). Animals were sacrificed 13 weeks post nerve transfer. Retrograde labeling was used to assess the number of motor neurons that regenerated their axons. Immunofluorescence was performed to evaluate target muscle re-innervation and atrophy, and to assess the phenotype of the SC within the distal nerve segment.Functional recovery in the muscle denervation and SC denervation groups mirrored that of the negative and positive control groups, respectively. The SC denervation group achieved better functional recovery, with a greater number of reinnervated motor endplates and less muscle atrophy, than the muscle denervation group. Retrograde labeling suggested a higher number of neurons contributing to muscle reinnervation in the muscle denervation group as compared to SC denervation (p > 0.05). The distal nerve segment in the muscle denervation group had a greater proportion of SCs expressing the proliferation marker Ki67 as compared to the SC denervation group (p < 0.05). Conversely, the SC denervation group had a higher percentage of senescent SCs expressing p16 as compared to the muscle denervation group (p < 0.05).The deleterious effects of muscle denervation are more consequential than the effects of SC denervation on functional recovery. The effects of 12 weeks of SC denervation on functional outcome were negligible. Future studies are needed to determine whether longer periods of SC denervation negatively impact functional recovery.

Amputation Revision Surgery – Refining the surgical approach. Ten years of experience and 250 cases, impressions, outcomes, and thoughts for the future

Introduction: The decision for revision amputation surgery requires a multi-disciplinary approach and the evidence on outcome data available in the current literature is limited. The aim of this observational, retrospective study was to investigate in patients undergoing stump revision, whether factors such as pathology and reason for the revision surgery affect surgical ‘success’ rates as primary outcomes. Secondary outcomes of interest include rehabilitation outcomes and complication rates.Methods: From December 2008 to November 2018, 250 amputation revision procedures were performed at our centre. Surgical and rehabilitation outcomes and indication for revision surgery were measured for each patient.Results: There was an overall surgical success rate of 81% and an overall rehabilitation success rate of 63%, with variable outcomes related to the indication for surgery. Revisions for bony pathology had excellent results from a surgical perspective (100%) and good results from a rehabilitation perspective (71%). Revisions for soft tissue pathology and neuroma had satisfactory results from a surgical perspective (81% and 74% respectively) and rehabilitation perspective (56% and 71% respectively). Surgical success rates for those undergoing revision surgery due to non-neuroma pain were poor.Conclusions: We found that revision surgery for defined anatomical abnormalities, such as bone pathology or neuromata are associated with good outcomes. Surgical techniques, specifically related to the management of neuromas are continuing to develop, with promising results from the application of targeted muscle reinnervation (TMR) in the treatment of neuromata. The primary amputation surgeon should exercise caution when considering compromising bone length for soft tissue or skin coverage, as revision surgery can address the excision of skin graft or refashioning of the soft tissue envelope at a later stage. Careful patient selection is key to ensure we advocate offering our patients the right operation at the right time, for the right pathology.

Application of Spare Parts in Combination with Targeted Muscle Reinnervation Surgery.

Targeted muscle reinnervation is a contemporary technique designed to enhance an amputee's ability to operate a myoelectric prosthesis. This technique has been shown to decrease neuropathic pain, including neuroma and phantom limb pain. In certain amputations, especially forequarter and hindlimb levels, there may be no nearby recipient muscle sites, or the residual nerve may be too short to perform targeted muscle reinnervation. Applying the spare parts concept can help solve this problem by providing nerve autograft or additional muscle recipient sites within the spare parts flap for successful targeted muscle reinnervation surgery procedures. A retrospective review of all patients that underwent spare parts targeted muscle reinnervation reconstructions between 2016 and 2019 at two institutions was performed. Patients were assessed for healing, neuroma and phantom limb pain, and function. Twelve patients underwent targeted muscle reinnervation during spare parts reconstruction; eight were male and four were female. The mean patient age was 55.3 years (range, 16 to 72 years). For those with known soft-tissue deficit size, the surface area of the donor site spared by using spare parts reconstruction ranged from 216 to 856 cm2. None of the 12 patients subsequently experienced neuroma, and 75 percent had no phantom limb pain after 3 months. Three patients have obtained insurance-approved myoelectric prosthetics, and all three demonstrated intuitive control of targeted muscles. Using a spare parts reconstruction in conjunction with targeted muscle reinnervation may optimize reconstructive efforts in the setting of major limb amputations and aid in decreasing phantom limb and neuroma pain, and facilitate the possibility of functional prosthetic and/or myoelectric prosthesis use. Therapeutic, IV.