Barriers to Epineural Scarring: Role in Treatment of Traumatic Nerve Injury and Chronic Compressive Neuropathy

Optimizing Outcomes in Revision Peripheral Nerve Surgery of the Upper Extremity

Peripheral nerve surgeries for compressive neuropathy in the upper extremity are generally successful. However, cases that either fail or have complications requiring revision surgery are challenging. During revision consideration, surgeons should perform a comprehensive preoperative workup to understand the etiology of the patient's symptoms and categorize symptoms as persistent, recurrent, or new in relation to the index procedure. Revision surgery often requires an open, extensile approach with additional procedures to optimize outcomes. Even with proper workup and treatment, clinical outcomes of revision surgeries are inferior compared to primary surgeries and patients should be well informed prior to undergoing such procedures.

Porcine submucosal extracellular matrix wrapping of the ulnar nerve in revision cubital tunnel surgery

The wrapping technique aims to protect the nerve when the nerve bed is compromised or more commonly to prevent the recurrence of scar tethering following neurolysis. A wrap provides a physical barrier to scar and helps restore the paraneurial gliding layer. This study aimed to evaluate the results of the AxoGuard® nerve protector, a porcine-derived submucosal extracellular matrix (PECM), used as an adjunct in persistent or recurrent cubital tunnel syndrome (CuTS). This retrospective cohort study evaluated patients diagnosed, between 2012 and 2020, with neuropathic pain who underwent revision surgery. Patients were categorised into Group A (revision surgery only) and Group B (revision surgery and adjunctive PECM nerve wrapping). Disease severity was scored at the baseline and six months post-operatively using the McGowan classification. A linear regression model was used to assess the effect of wrapping the ulnar nerve on the clinical outcome at six months. Fifty-nine nerves were treated; among them, adjunctive PECM wrapping was used in 32 nerves. Disease severity at baseline was similar between the groups. After adjusting for differences in baseline characteristics, participants in Group B improved with a significant difference of 0.43 McGowan points over Group A (95% CI (0.01-0.86), p = 0.049). There were no implant-related complications. Group B improved with excellent or good outcomes in 84.4% patients at the final follow-up. Persistent or recurrent CuTS were associated with neuropathic pain and significant nerve scar tether. The use of PECM appears to lead to improved clinical symptoms, possibly by reducing adhesions and encouraging physiological glide. LEVEL OF EVIDENCE: Level III evidence.

Fibrin Glue Coating Limits Scar Tissue Formation around Peripheral Nerves

Scar tissue formation presents a significant barrier to peripheral nerve recovery in clinical practice. While different experimental methods have been described, there is no clinically available gold standard for its prevention. This study aims to determine the potential of fibrin glue (FG) to limit scarring around peripheral nerves. Thirty rats were divided into three groups: glutaraldehyde-induced sciatic nerve injury treated with FG (GA + FG), sciatic nerve injury with no treatment (GA), and no sciatic nerve injury (Sham). Neural regeneration was assessed with weekly measurements of the visual static sciatic index as a parameter for sciatic nerve function across a 12-week period. After 12 weeks, qualitative and quantitative histological analysis of scar tissue formation was performed. Furthermore, histomorphometric analysis and wet muscle weight analysis were performed after the postoperative observation period. The GA + FG group showed a faster functional recovery (6 versus 9 weeks) compared to the GA group. The FG-treated group showed significantly lower perineural scar tissue formation and significantly higher fiber density, myelin thickness, axon thickness, and myelinated fiber thickness than the GA group. A significantly higher wet muscle weight ratio of the tibialis anterior muscle was found in the GA + FG group compared to the GA group. Our results suggest that applying FG to injured nerves is a promising scar tissue prevention strategy associated with improved regeneration both at the microscopic and at the functional level. Our results can serve as a platform for innovation in the field of perineural regeneration with immense clinical potential.

Biodegradable Nerve Guide with Glial Cell Line-Derived Neurotrophic Factor Improves Recovery After Facial Nerve Injury in Rats

Background: Bioengineered nerve guides with glial cell line-derived neurotrophic factor (GDNF) support recovery after facial nerve injury by acting as regenerative scaffolds. Objective: To compare functional, electrophysiological, and histological outcomes after repair of rat facial nerve transection in control, empty nerve guide, and nerve guide with GDNF conditions. Methods: Rats underwent transection and primary repair of the buccal branch of the facial nerve and were divided into (1) transection and repair only, (2) transection and repair augmented with empty guide, (3) transection and repair augmented with GDNF-guide groups. Weekly measurements of the whisking movements were recorded. At 12 weeks, compound muscle action potentials (CMAPs) at the whisker pad were assessed, and samples were collected for histomorphometric analysis. Results: Rats in GDNF-guide group displayed the earliest peak in normalized whisking amplitude. CMAPs were significantly higher after GDNF-guide placement. Mean fiber surface area of the target muscle, axonal count of the injured branch, and the number of Schwann cells were highest with GDNF guides. Conclusion: The biodegradable nerve guide containing double-walled GDNF microspheres enhanced recovery after facial nerve transection and primary repair.

Shielding the Nerve: A Systematic Review of Nerve Wrapping to Prevent Adhesions in the Rat Sciatic Nerve Model

BACKGROUND

Peripheral nerve pathology is frequently encountered in clinical practice among peripheral nerve and extremity surgeons. One major factor limiting nerve regeneration and possibly leading to revision surgeries is the development of traumatic or postoperative adhesions and scarring around nerves. In experimental models, different materials have been studied to limit scar tissue formation when wrapped around nerves.

METHODS

A systematic review of studies describing nerve-wrapping materials in a non-transectional rat sciatic nerve model was performed following the PRISMA guidelines. Literature describing nerve-wrapping methods for the prevention of peripheral nerve scarring in rat sciatic nerve models was identified using PubMed and Web of Science, scanned for relevance and analyzed.

RESULTS

A total of 15 original articles describing 23 different materials or material combinations for nerve wrapping were included. The heterogeneity of the methods used did not allow a meta-analysis, thus, a systematic review was performed. Out of 28 intervention groups, 21 demonstrated a preventive effect on scar tissue formation in at least one qualitative or quantitative assessment method.

CONCLUSIONS

The analyzed literature describes a variety of materials from different origins to limit peripheral nerve scarring and adhesions. Thus, a scar-preventive effect by wrapping peripheral nerves as adhesion prophylaxis seems likely. However, a quantitative comparison of the studies to identify the optimal material or technique is not possible with the diversity of used models and study designs. Therefore, further research needs to be performed to identify the optimal nerve wraps to be used routinely in clinical practice.

Avoiding scar tissue formation of peripheral nerves with the help of an acellular collagen matrix

INTRODUCTION

Extensive scar tissue formation after peripheral nerve injury or surgery is a common problem. To avoid perineural scarring, implanting a mechanical barrier protecting the nerve from inflammation processes in the perineural environment has shown promising results for functional recovery. This study investigates the potential of an acellular collagen-elastin matrix wrapped around a peripheral nerve after induction of scar tissue formation.

MATERIALS AND METHODS

In the present study, 30 Lewis rats were separated into three groups and sciatic nerve scarring was induced with 2.5% glutaraldehyde (GA-CM) or 2.5% glutaraldehyde with a supplemental FDA-approved acellular collagen-elastin matrix application (GA+CM). Additionally, a sham group was included for control. Nerve regeneration was assessed by functional analysis using the Visual Statisc Sciatic Index (SSI) and MR neurography during the 12-week regeneration period. Histological and histomorphometry analysis were performed to evaluate the degree of postoperative scar tissue formation.

RESULTS

Histological analysis showed an extensive scar tissue formation for GA-CM. Connective tissue ratio was significantly (p < 0.009) reduced for GA+CM (1.347 ± 0.017) compared to GA-CM (1.518 ± 0.057). Similarly, compared to GA+CM, MR-Neurography revealed extensive scar tissue formation for GA-CM with a direct connection between nerve and paraneural environment. Distal to the injury site, quantitative analysis presented significantly higher axon density (p = 0.0145), thicker axon diameter (p = 0.0002) and thicker myelinated fiber thickness (p = 0.0008) for GA+CM compared to GA-CM. Evaluation of functional recovery revealed a significantly faster regeneration for GA+CM.

CONCLUSION

The supplemental application of an acellular collagen-elastin matrix showed beneficial effects in histological, radiological, and functional analysis. Therefore, applying a collagen-elastin matrix around the nerve after peripheral nerve injury or surgery may have beneficial effects on preventing scar tissue formation in the long run. This represents a feasible approach to avoid scar tissue formation in peripheral nerve surgery.

Compression Neuropathies: Revisions and Managing Expectations

Most compression neuropathies can be reliably treated with surgical decompression; however, in approximately 25% of the cases, this release fails, requiring revision surgery. Defining the correct diagnosis after a failed nerve decompression (ie, persistent, recurrent, or new symptoms) is of the utmost importance and guides toward the optimal treatment. This article describes the clinical categorization of secondary carpal tunnel syndrome and cubital tunnel syndrome, intraoperative principles of revision surgery and treatment options that are currently available.

Management of Failed Carpal and Cubital Tunnel Release: An Evidence-Based Guide to Success

Carpal tunnel and cubital tunnel syndromes are the most common compressive neuropathies of the upper extremity with surgical treatment having high success rates for both conditions. Although uncommon, persistent or recurrent carpal and cubital tunnel syndrome presents a challenge for patients and providers. Diagnosis of persistence versus recurrence of the pathology is key in establishing an appropriate treatment plan to provide the best possible patient outcomes. After an established diagnosis, a wide array of treatment options exist which varies based on previous procedures performed. This review discusses relevant anatomy, etiology, and clinical presentations of persistent and recurrent carpal and cubital tunnel syndromes. The range of treatment options is presented based on history and diagnostic findings. Treatment options span from revision of nerve decompression to the use of soft tissue rearrangement procedures. Some specific treatment options discussed include simple revision nerve decompression, external neurolysis, soft tissue rearrangement, such as the hypothenar fat flap or various transposition techniques, and the use of nerve wraps. Included is an evidence-based management guide for diagnosis and treatment of persistent versus recurrent carpal and cubital tunnel syndromes.

Photothermal Treatment of Polydopamine Nanoparticles@Hyaluronic Acid Methacryloyl Hydrogel Against Peripheral Nerve Adhesion in a Rat Model of Sciatic Nerve

Purpose

Peripheral nerve adhesion occurs following injury and surgery. Functional impairment leading by peripheral nerve adhesion remains challenging for surgeons. Local tissue overexpression of heat shock protein (HSP) 72 can reduce the occurrence of adhesion. This study aims to develop a photothermal material polydopamine nanoparticles@Hyaluronic acid methacryloyl hydrogel (PDA NPs@HAMA) and evaluate their efficacy for preventing peripheral nerve adhesion in a rat sciatic nerve adhesion model.

Materials and Methods

PDA NPs@HAMA was prepared and characterized. The safety of PDA NPs@HAMA was evaluated. Seventy-two rats were randomly assigned to one of the following four groups: the control group; the hyaluronic acid (HA) group; the polydopamine nanoparticles (PDA) group and the PDA NPs@HAMA group (n = 18 per group). Six weeks after surgery, the scar formation was evaluated by adhesion scores and biomechanical and histological examinations. Nerve function was assessed with electrophysiological examination, sensorimotor analysis and gastrocnemius muscle weight measurements.

Results

There were significant differences in the score on nerve adhesion between the groups (p < 0.001). Multiple comparisons indicated that the score was significantly lower in the PDA NPs@HAMA group (95% CI: 0.83, 1.42) compared with the control group (95% CI: 1.86, 2.64; p = 0.001). Motor nerve conduction velocity and muscle compound potential of the PDA NPs@HAMA group were higher than the control group's. According to immunohistochemical analysis, the PDA NPs@HAMA group expressed more HSP72, less α-smooth muscle actin (α-SMA), and had fewer inflammatory reactions than the control group.

Conclusion

In this study, a new type of photo-cured material with a photothermic effect was designed and synthesized-PDA NPs@HAMA. The photothermic effect of PDA NPs@HAMA protected the nerve from adhesion to preserve the nerve function in the rat sciatic nerve adhesion model. This effectively prevented adhesion-related damage.

Reoperative Brachial Plexus Neurolysis After Previous Anatomically Complete Supraclavicular Decompression for Neurogenic Thoracic Outlet Syndrome: A 10-Year Single-Center Case Series

BACKGROUND

Optimal management of recurrent neurogenic thoracic outlet syndrome (NTOS) remains a considerable challenge.

OBJECTIVE

To assess the safety and effectiveness of reoperative brachial plexus neurolysis in patients with recurrent NTOS.

METHODS

From 2009 to 2019, 85 patients underwent reoperative supraclavicular brachial plexus neurolysis for recurrent NTOS after a previous anatomically complete supraclavicular decompression. Data from a prospectively maintained database were analyzed retrospectively.

RESULTS

The mean patient age at reoperation was 36.9 ± 1.3 (range 15-64) years, 75% were female, and the interval after previous primary operation was 2.5 ± 0.2 years. Intervening injury had precipitated recurrent NTOS in 14 patients (16%), and the mean Disability of the Arm, Shoulder, and Hand (QuickDASH) score before reoperation was 65.2 ± 2.6, reflecting substantial disability. Operative findings consisted of dense fibrous scar tissue surrounding/encasing the brachial plexus. Compared with the previous primary operations, reoperations had a shorter operative time (198 ± 4 vs 161 ± 5 minutes, P < .01) and hospital stay (4.4 ± 0.2 vs 3.6 ± 0.1 days, P < .01), but there were no significant differences in the frequency of prolonged hospitalization (7.1% vs 4.7%), early reoperation (3.5% vs 1.2%), or 30-day hospital readmission (8.2% vs 7.1%). During a median follow-up of 4.8 years, QuickDASH scores improved by 23.3 ± 2.6 (34.2% ± 3.6%; P < .01) and patient-rated outcomes were excellent in 24%, good in 42%, fair in 26%, and poor in 8%.

CONCLUSION

Reoperative supraclavicular brachial plexus neurolysis is technically challenging but safe and effective treatment for recurrent NTOS, with significant improvements in symptoms and function. Diminishing perineural scar tissue development and avoiding secondary injury would likely decrease the need for reoperations.

Resorbable Nerve Wraps: Can They Be Overtightened?

BACKGROUND

 Nerve wrapping has been advocated to minimize scarring and adhesion following neurorrhaphy or neurolysis. A wrap should provide an enclosure that is snug enough to protect and support the affected nerve without strangulating the nerve. The degree to which resorbable wraps should be ": tightened" around the nerve is largely subjective with scant literature on the subject. The purpose of this study was to evaluate the effects of tightly fitting resorbable nerve wraps around intact rat sciatic nerves.

METHODS

 Twenty-four Sprague-Dawley rats underwent exposure and circumferential measurement of the right sciatic nerve. Porcine-derived extracellular matrix (ECM) wraps were trimmed and sutured to enclose the nerve with a tight (same as that of the nerve, n = 8) or loose (2.5x that of the nerve, n = 8) circumference. Sham-surgery control animals (n = 8) had no wrap treatment. Functional outcome was recorded biweekly by sciatic functional index (SFI) with walking track analysis and electrical stimulation. Animals were sacrificed at 12 weeks for histologic analyses.

RESULTS

 No withdrawal response could be evoked in the tight-wrap group until week 9, while significant improvement in SFI first occurred between weeks 5 and 7. By week 12, the tight-wrap group required 60% more current compared with baseline stimulation to produce a withdrawal response. They recovered 81% of SFI baseline values but also demonstrated significantly greater intraneural collagen content (p < 0.001) and lower axon density (p < 0.05) than in the loose-wrap and sham groups. The loose-wrap group had comparable functional and histologic outcomes to the sham control group.

CONCLUSION

 Resorbable ECM nerve wraps applied tightly around intact rat sciatic nerves caused significant functional impairment and histological changes characteristic of acute nerve compression. Significant but incomplete functional recovery was achieved by the tight-wrap group after 12 weeks, but such recovery may not apply in humans.

Revision of Carpal Tunnel Surgery

Carpal tunnel release is one of the most commonly performed upper extremity procedures. The majority of patients experience significant improvement or resolution of their symptoms. However, a small but important subset of patients will experience the failure of their initial surgery. These patients can be grouped into persistent, recurrent, and new symptom categories. The approach to these patients starts with a thorough clinical examination and is supplemented with electrodiagnostic studies. The step-wise surgical management of revision carpal tunnel surgery consists of the proximal exploration of the median nerve, Guyon’s release with neurolysis, the rerelease of the transverse retinaculum, evaluation of the nerve injury, treatment of secondary sites of compression, and potential ancillary procedures. The approach and management of failed carpal tunnel release are reviewed in this article.

Effect of glutaraldehyde-crosslinked cartilage acellular matrix film on anti-adhesion and nerve regeneration in a rat sciatic nerve injury model

Decellularized extra-cellular matrix (ECM) has been studied as an alternative to anti-adhesive biomaterials and cartilage acellular matrix (CAM) has been shown to inhibit postoperative adhesion in several organs. This study aimed to evaluate the suitability of glutaraldehyde (GA) crosslinked CAM-films as anti-adhesion barriers for peripheral nerve injury. The films were successfully fabricated and showed improved physical properties such as mechanical strength, swelling ratio, and lengthened degradation period while maintaining the microstructure and chemical composition after GA crosslinking. In the in vitro study of CAM-film, the dsDNA content met the recommended limit of decellularization and more than 70% of the major ECM components were preserved after decellularization. The adhesion and proliferation of seeded human umbilical vein endothelial cells and fibroblasts were significantly lower in CAM-film than in control, but similar with Seprafilm. However, the CAM-film extract did not show cytotoxicity. In the in vivo study, the peri-neural fibrosis was thicker, adhesion score higher, and peri-neural collagen fibers more abundant in the control group than in the CAM-film group. The total number of myelinated axons was significantly higher in the CAM-film group than in the control group. The inflammatory marker decreased with time in the CAM-film group compared to that in the control group, whereas the nerve regenerative marker expression was maintained. Moreover, the ankle angles at contracture and toe-off were higher in the CAM film-treated rats than in the control rats. GA-crosslinked CAM films may be used during peripheral nerve surgery to prevent peri-neural adhesion and enhance nerve functional recovery.

The management of failed cubital tunnel decompression

Cubital tunnel decompression is a commonly performed operation with a much higher failure rate than carpal tunnel release.

Failed cubital tunnel release generally occurs due to an inadequate decompression in the primary procedure, new symptoms due to an iatrogenic cause, or development of new areas of nerve irritation.

Our preferred technique for failed release is revision circumferential neurolysis with medial epicondylectomy, as this eliminates strain, removes the risk of subluxation, and avoids the creation of secondary compression points.

Adjuvant techniques including supercharging end-to-side nerve transfer and nerve wrapping show promise in improving the results of revision surgery.

Limited quality research exists in this subject, compounded by the lack of consensus on diagnostic criteria, classification, and outcome assessment.

Cite this article: EFORT Open Rev 2021;6:735-742. DOI: 10.1302/2058-5241.6.200135

The Effects of a Porcine Extracellular Matrix Nerve Wrap as an Adjunct to Primary Epineurial Repair

PURPOSE

Outcomes after end-to-end epineural suture repair remain poor. Nerve wraps have been advocated to improve regeneration across repair sites by potentially reducing axonal escape and scar ingrowth; however, limited evidence currently exists to support their use.

METHODS

Forty Lewis rats underwent median nerve division and immediate repair. Half were repaired with epineural suturing alone, and the others underwent epineural suture repair with the addition of a nerve wrap. Motor recovery was measured using weekly grip strength and nerve conduction testing for 15 weeks. Histomorphometric analyses were performed to assess intraneural collagen deposition, cellular infiltration, and axonal organization at the repair site, as well as axonal regeneration and neuromuscular junction reinnervation distal to the repair site.

RESULTS

The wrapped group demonstrated significantly less intraneural collagen deposition at 5 weeks. Axonal histomorphometry, cellular infiltration, neuromuscular junction reinnervation, and functional recovery did not differ between groups.

CONCLUSIONS

Nerve wraps reduced collagen deposition within the coaptation; however, no differences were observed in axonal regeneration, neuromuscular junction reinnervation, or functional recovery.

CLINICAL RELEVANCE

These findings suggest that extracellular matrix nerve wraps can attenuate scar deposition at the repair site. Any benefits that may exist with regards to axonal regeneration and functional recovery were not detected in our model.

Histologic and Functional Outcomes of Conduit Wrapping for Peripheral Nerve Repair: Early Results in a Rat Model

BACKGROUND

 The concept of utilizing a nerve conduit for augmentation of a primary nerve repair has been advocated as a method to prevent neural scarring and decrease adhesions. Despite clinical use, little is known about the effects of a nerve conduit wrapped around a primary repair. To better understand this, we investigated the histologic and functional effects of use of a nerve conduit wrapped around a rat sciatic nerve repair without tension.

METHODS

 Twenty Lewis' rats were divided into two groups of 10 rats each. In each group, unilateral sciatic nerve transection and repair were performed, with the opposite limb utilized as a matched control. In the first group, direct repair alone was performed; in the second group, this repair was augmented with a porcine submucosa conduit wrapped around the repair site. Sciatic functional index (SFI) was measured at 6 weeks with walking track analysis in both groups. Nonsurvival surgeries were then performed in all animals to harvest both the experimental and control nerves to measure histomorphometric parameters of recovery. Histomorphometric parameters assessed included total number of neurons, nerve fiber density, nerve fiber width, G-ratio, and percentage of debris. Unpaired t-test was used to compare outcomes between the two groups.

RESULTS

 All nerves healed uneventfully but compared with direct repair; conduit usage was associated with greater histologic debris, decreased axonal density, worse G-ratio, and worse SFI. No significant differences were found in total axon count or gastrocnemius weight.

CONCLUSION

 In the absence of segmental defects, conduit wrapping primary nerve repairs seem to be associated with worse functional and mixed histologic outcomes at 6 weeks, possibly due to debris from conduit resorption. While clinical implications are unclear, more basic science and clinical studies should be performed prior to widespread adoption of this practice.

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.

Potential Therapeutic Strategies and Substances for Facial Nerve Regeneration Based on Preclinical Studies

Despite advances in microsurgical technology and an improved understanding of nerve regeneration, obtaining satisfactory results after facial nerve injury remains a difficult clinical problem. Among existing peripheral nerve regeneration studies, relatively few have focused on the facial nerve, particularly how experimental studies of the facial nerve using animal models play an essential role in understanding functional outcomes and how such studies can lead to improved axon regeneration after nerve injury. The purpose of this article is to review current perspectives on strategies for applying potential therapeutic methods for facial nerve regeneration. To this end, we searched Embase, PubMed, and the Cochrane library using keywords, and after applying exclusion criteria, obtained a total of 31 qualifying experimental studies. We then summarize the fundamental experimental studies on facial nerve regeneration, highlighting recent bioengineering studies employing various strategies for supporting facial nerve regeneration, including nerve conduits with stem cells, neurotrophic factors, and/or other therapeutics. Our summary of the methods and results of these previous reports reveal a common feature among studies, showing that various neurotrophic factors arising from injured nerves contribute to a microenvironment that plays an important role in functional recovery. In most cases, histological examinations showed that this microenvironmental influence increased axonal diameter as well as myelination thickness. Such an analysis of available research on facial nerve injury and regeneration represents the first step toward future therapeutic strategies.

Safety and efficacy of a nerve matrix membrane as a collagen nerve wrapping: a randomized, single-blind, multicenter clinical trial

A new nerve matrix membrane derived from decellularized porcine nerves has been shown to retain the major extracellular matrix components, and to be effective in preventing adhesion between the nerve anastomosis sites and the surrounding tissues in a rat sciatic nerve transection model, thereby enhancing regeneration of the nerve. The effectiveness of the membrane may be attributed to its various bioactive components. In this prospective, randomized, single-blind, parallel-controlled multicenter clinical trial, we compared the safety and efficacy of the new nerve matrix membrane with a previously approved bovine tendon-derived type I collagen nerve wrapping. A total of 120 patients with peripheral nerve injury were recruited from Beijing Jishuitan Hospital, The First Bethune Hospital of Jilin University, and Yantai Yuhuangding Hospital, China. The patients were randomly assigned to undergo end-to-end and tension-free neurorrhaphy with nerve matrix membrane (n = 60, 52 male, 8 female, mean age 41.34 years, experimental group) or tendon-derived collagen nerve wrapping (n = 60, 42 male, 18 female, mean age 40.17 years, control group). Patients were followed-up at 14 ± 5, 30 ± 7, 90 ± 10 and 180 ± 20 days after the operation. Safety evaluation included analyses of local and systemic reactions, related laboratory tests, and adverse reactions. Efficacy evaluation included a static 2-point discrimination test, a moving 2-point discrimination test, and a Semmes–Weinstein monofilament examination. Sensory nerve function was evaluated with the British Medical Research Council Scale and Semmes–Weinstein monofilament examination. The ratio (percentage) of patients with excellent to good results in sensory nerve recovery 180 ± 20 days after the treatment was used as the primary effectiveness index. The percentages of patients with excellent to good results in the experimental and control groups were 98.00% and 94.44%, respectively, with no significant difference between the two groups. There were no significant differences in the results of routine blood tests, liver and renal function tests, coagulation function tests, or immunoglobulin tests at 14 and 180 days postoperatively between the two groups. These findings suggest that the novel nerve matrix membrane is similar in efficacy to the commercially-available bovine-derived collagen membrane in the repair of peripheral nerve injury, and it may therefore serve as an alternative in the clinical setting. The clinical trial was approved by the Institutional Ethics Committee of Beijing Jishuitan Hospital, China (approval No. 20160902) on October 8, 2016, the Institutional Ethics Committee of the First Bethune Hospital of Jilin University, China (approval No. 160518-088) on December 14, 2016, and the Institutional Ethics Committee of Yantai Yuhuangding Hospital, China (approval No. 2016-10-01) on December 9, 2016. The clinical trial was registered with the Chinese Clinical Trial Registry (registration number: ChiCTR2000033324) on May 28, 2020.

Electrospun polycaprolactone (PCL)-amnion nanofibrous membrane prevents adhesions and promotes nerve repair in a rat model of sciatic nerve compression

Adhesion and scarring after neural surgery are detrimental to nerve regeneration and functional recovery. Amniotic membranes have been used in tissue repair due to their immunogenicity and richness in cytokines. In this study, an electrospun polycaprolactone (PCL)-amnion nanofibrous membrane was prepared for the treatment of sciatic nerve compression in a rat model. The effects of the PCL-amnion nanofibrous membrane on the prevention of adhesion formation and nerve regeneration were evaluated using electrophysiology and histological analyses. Compared with the medical chitosan hydrogel dressing, the PCL-amnion nanofibrous membrane significantly reduced peripheral nerve adhesion and promoted the rapid recovery of nerve conduction. Moreover, the immunohistochemical analysis identified more Schwann cells and less pro-inflammatory M1 macrophages in the PCL-amnion group. Western blot and RT-PCR results showed that the expression levels of type-Ⅰ and Ⅲ collagen in the PCL-treated rats were half of those in the control group after 12 weeks, while the expression level of nerve growth factor was approximately 3.5 times that found in the rats treated with medical chitosan hydrogel. In summary, electrospun PCL-amnion nanofibrous membranes can effectively reduce adhesion after neural surgery and promote nerve repair and regeneration. The long-term retention in vivo and sustained release of cytokines make PCL-amnion a promising biomaterial for clinical application.

Benefits of a collagen membrane for recurrent ulnar nerve entrapment at the elbow: A series of 40 cases

The rate of failure or recurrence after ulnar nerve release at the elbow is up to 25%. Various biomaterials have been developed to protect nerves from postoperative adhesions. The aim of this study was to review a case series of 40 surgical revision procedures of the ulnar nerve at the elbow, protected by a collagen membrane (Cova™ ORTHO). Forty patients who had this revision surgery between January 2013 and December 2017 were reviewed: 34 were evaluated in person, 6 were evaluated over the phone. The operation consisted in release of the ulnar nerve, anterior subcutaneous transposition and nerve protection using a collagen membrane. We assessed the following parameters with an average follow-up of 4 years and 3 months: paresthesia, night awakening, quality of life (QuickDASH score) and neuropathic pain (DN4 questionnaire). The outcome was determined with the Gabel & Amadio score. The patients' satisfaction was evaluated. A significant decrease in paresthesia and night awakening was found (p < 0.05). The average Gabel & Amadio score improved from 4.4 to 6.7 with 5 excellent, 19 good, 9 fair, and 1 poor result. The average DN4 was 5/10 and the QuickDASH score was 40.1. Eighty percent of patients were satisfied or very satisfied with the outcome. Surgical revision of the ulnar nerve at the elbow remains a delicate operation without a gold standard. This case series found good or excellent results in 70% of patients. Surgical revision of the ulnar nerve with a collagen membrane is a reliable alternative among other possibilities for ulnar nerve release at the elbow.

Nerve wrapping for recurrent compression neuropathy: A systematic review

BACKGROUND

The recurrence of symptoms following primary nerve compression surgery can occur in up to 25% of cases. Nerve wrapping can be utilised for revision surgery. An ideal barrier should minimise the chance of fibrosis, scarring and allow for adequate nerve gliding. This review evaluates the use of autologous or commercially available allograft and xenograft options as barriers against nerve scarring following revision surgery.

METHODS

PubMed, Ovid Embase and Cochrane databases were searched using the All Fields Index. Nine hundred titles underwent title screening with 11 studies being included in the final analysis. The risk of bias was assessed using the Methodological Index for Non-Randomised Studies (MINORS) tool. PRISMA guidelines were followed at all stages and the review was registered with PROSPERO (CRD 42020182818).

RESULTS

The 11 studies comprised of all case series. In total, 114 patients were included, with ages ranging from 28 to 90. Previously, the number of revision surgeries ranged from 0 to 5. Autologous veins were used in 6 studies, collagen in 3 studies and human amniotic membrane in 2 studies. Improvements in subjective and objective outcomes were seen with all wrap types. Pain was the most common residual symptom (46% of patients). The most common complication was pain at the donor site following vein harvest (19% of patients).

CONCLUSION

This is the first systematic review to summarise the outcomes of nerve wraps for revision compression neuropathy. While improvements in outcomes were reported, further comparative studies are needed to determine the best nerve wrap.

Fatores de insucesso do tratamento cirúrgico da síndrome do túnel do carpo: Quando e como revisar a cirurgia de descompressão do túnel do carpo

Despite being a procedure widely used all over the world with high rates of symptom remission, surgical treatment of carpal tunnel syndrome may present unsatisfactory outcomes. Such outcomes may be manifested clinically by non-remission of symptoms, remission of symptoms with recurrence a time after surgery or appearance of different symptoms after surgery. Different factors are related to this unsuccessful surgical treatment of carpal tunnel syndrome. Prevention can be achieved through a thorough preoperative clinical evaluation of the patient. As such, the surgeon will be able to make differential or concomitant diagnoses, as well as determine factors related to patient dissatisfaction. Perioperative factors include the correct identification of anatomical structures for complete median nerve decompression. Numerous procedures have been described for managing postoperative factors. Among them, the most common is adhesion around the median nerve, which has been treated with relative success using different vascularized flaps or autologous or homologous tissue coverage. The approach to cases with unsuccessful surgical treatment of carpal tunnel syndrome is discussed in more detail in the text.

[Surgical treatment of carpal tunnel syndrome: open release of the flexor retinaculum and hypothenar fat flap for revision surgery]

OBJECTIVE

Decompression of the median nerve by complete release of the flexor retinaculum and the distal antebrachial fascia. In the case of revision surgery providing of a scar-free covering of the median nerve, if necessary.

INDICATIONS

Carpal tunnel release is indicated for symptomatic patients with painful paraesthesia or neurological deficits after adequate diagnostic evaluation. The hypothenar fat flap is indicated in revision surgery if a sufficient nerve bed of the median nerve is needed and to restore nerve gliding.

CONTRAINDICATIONS

General operative limitations. The hypothenar fat flap is not indicated in revision surgery if median nerve irritation is not caused by surrounding scaring but other reasons like tendonitis.

SURGICAL TECHNIQUE

Proximal longitudinal incision of the palm. Subcutaneous dissection and incision of the palmar aponeurosis. Careful ulnar incision of the transverse carpal ligament. Considerate release of the distal and proximal parts of the retinaculum as well as the distal part of the antebrachial fascia. Exploration of the median nerve and palpation of the carpal tunnel and resection of compressive structures, if necessary. In case of revision surgery, if required, the hypothenar fat flap is raised. The fat flap is transposed without tension palmar to the median nerve and fixed to the radial side of the carpal tunnel.

POSTOPERATIVE MANAGEMENT

Early functional mobilization. Immobilization for a short period is optional. After revision surgery and hypothenar fat flap, splinting for one week is recommended.

Evaluation of the Crushed Sciatic Nerve and Denervated Muscle with Multimodality Ultrasound Techniques: An Animal Study

This study was aimed at evaluating the value of multimodality ultrasound techniques in the detection of crushed sciatic nerve and denervated muscle in rabbits. Fifty healthy male New Zealand white rabbits were randomly divided into five groups (n = 10 in each group): four crushed injury groups at 1, 2, 4 and 8 wk post-sciatic nerve crushed injury, and a control group without crush injury. The crushed sciatic nerve and denervated muscle were measured with conventional ultrasound, shear wave elastography and contrast-enhanced ultrasonography, and the results were compared with the histopathological parameters. The inter- and intra-reader reliability of multimodality ultrasound was assessed with intra-class correlation coefficients. Our results revealed that the sciatic nerve thickened at 2 wk post-crushed injury (p < 0.01), but recovered to almost normal thickness at 8 wk post-injury. Stiffness of the crushed nerve gradually increased (p < 0.01), and intraneural blood volume decreased (area under the curve, peak intensity, time to peak, p < 0.01 each) over time. Histopathological evaluation revealed obvious collagen hyperplasia and poor regenerated microvascular and sparse axonal regeneration and remyelination. Compared with that of the control group, the elastic modulus of the denervated muscle significantly increased (p < 0.05), which may be related to the increased intramuscular collagen (p < 0.01) and decreased muscle fiber cross-sectional area (p < 0.01). There were no significant differences in contrast-enhanced ultrasonography parameters (area under the curve, peak intensity, time to peak) of the denervated muscle between the crush injury groups and the control group (p >0.05). All ultrasound results had excellent inter- and intra-reader consistency (intraclass correlation coefficient >0.80). In conclusion, multimodality ultrasound techniques could provide quantitative information on the morphologic changes, mechanical properties and blood perfusion of crushed nerve and denervated muscle, which may be of great importance in clinical practice.

A case series of seven patients with recurrent median nerve neuropathy treated by the revision surgery of median nerve neurolysis and wrapping with radial artery perforator adipose flap

Adhesion neuropathy of the median nerve with persistent pain can be a challenging problem. Currently, coverage of the median nerve with a well-vascularized soft tissue is deemed necessary after secondary neurolysis. Herein, we reviewed the outcomes of seven patients with a persistent median nerve neuropathy after a primary open carpal tunnel release or a median nerve repair, treated with neurolysis and median nerve wrapping with radial artery perforator adipose flaps. During the revision surgery, after a careful and complete neurolysis of the scarred median nerve, the distally based radial artery perforator adipose flap without its fascia was raised and rotated to wrap the median nerve. The mean size of the perforator flap was 1146 mm², which was enough to wrap the median nerve in all patients. At 26 months postsurgery, both the visual analog scale score for pain with tingling, and the patient-reported outcome measures improved. There was no recurrence of the median nerve adhesion neuropathy and no major complications were noted. Tinel's sign at the palmar wrist completely disappeared in four patients and was relieved in three patients. The median distal motor latency becomes recordable, and closer to a normal compound motor action potential postoperatively in all patients. Secondary neurolysis and median nerve wrapping with a radial artery perforator adipose flap, which was modified to be softer and thinner than the radial artery perforator adipofascial flap, was a successful treatment for the recurrent median nerve neuropathy in terms of both pain relief and restoration of the hand function.

Evaluation and Management of Unsuccessful Carpal Tunnel Release

Carpal tunnel release (CTR) is a routine and effective surgical treatment for carpal tunnel syndrome. Dissatisfied patients after CTR are uncommon but present diagnostic and therapeutic challenges. This article discusses the most common reasons for unsuccessful CTR, the appropriate ensuing workup, and current evidence regarding revision surgery. The authors' preferred treatment algorithm for the surgical management of the unsuccessful CTR is presented.

Inflammatory Reactions to Xenogenic Nerve Wraps: A Report of Three Cases

CASE

Recurrent carpal tunnel syndrome is a challenging problem. Nerve wraps have been introduced as a barrier to prevent scar traction neuritis for use during revision carpal tunnel surgery. We present 3 cases of inflammatory responses to bovine collagen and porcine subintestinal mucosal nerve wraps in patients undergoing revision carpal tunnel surgery. No patient had evidence of infection, and pathology revealed acute and chronic inflammation. All 3 patients responded favorably following wrap removal.

CONCLUSIONS

We recommend caution with the routine use of nerve wraps in the setting of revision carpal tunnel surgery.

Effect of chitosan combined with hyaluronate on promoting the recovery of postoperative facial nerve regeneration and function in rabbits

To determine better solutions for postoperative nerve functional recovery, the effects of chitosan and hyaluronate on perineural scar formation and neural function recovery were investigated in 40 rabbits. Rabbits were randomized into 4 groups: A (chitosan), B (chitosan + hyaluronate), C (hyaluronate) and D (control). The rabbits underwent the same parotidectomy surgery, but different materials were used to cover the operated nerves. By evaluating specific indicators, including vibrissae motion tests, neural electrophysiological examinations and extraneural examinations, it was revealed that the amplitude of vibrissae motion of all groups had increased 6 weeks after surgery. The recovery of Group B was superior compared with all other groups at 4 and 12 weeks post-surgery; however no significant differences were detected. Group B exhibited a great number of nerve fibers, thicker myelin sheath and greater nerve conduction velocity. In summary, the use of a chitosan conduit combined with sodium hyaluronate gel may prevent perineural scar formation in facial nerves and promote nerve functional recovery.