Allograft reconstruction for digital nerve loss

Treatment options for digital nerve injury: a systematic review and meta-analysis

BACKGROUND

Surgical treatment of finger nerve injury is common for hand trauma. However, there are various surgical options with different functional outcomes. The aims of this study are to compare the outcomes of various finger nerve surgeries and to identify factors associated with the postsurgical outcomes via a systematic review and meta-analysis.

METHODS

The literature related to digital nerve repairs were retrieved comprehensively by searching the online databases of PubMed from January 1, 1965, to August 31, 2021. Data extraction, assessment of bias risk and the quality evaluation were then performed. Meta-analysis was performed using the postoperative static 2-point discrimination (S2PD) value, moving 2-point discrimination (M2PD) value, and Semmes-Weinstein monofilament testing (SWMF) good rate, modified Highet classification of nerve recovery good rate. Statistical analysis was performed using the R (V.3.6.3) software. The random effects model was used for the analysis. A systematic review was also performed on the other influencing factors especially the type of injury and postoperative complications of digital nerve repair.

RESULTS

Sixty-six studies with 2446 cases were included in this study. The polyglycolic acid conduit group has the best S2PD value (6.71 mm), while the neurorrhaphy group has the best M2PD value (4.91 mm). End-to-side coaptation has the highest modified Highet's scoring (98%), and autologous nerve graft has the highest SWMF (91%). Age, the size of the gap, and the type of injury were factors that may affect recovery. The type of injury has an impact on the postoperative outcome of neurorrhaphy. Complications reported in the studies were mainly neuroma, cold sensitivity, paresthesia, postoperative infection, and pain.

CONCLUSION

Our study demonstrated that the results of surgical treatment of digital nerve injury are generally satisfactory; however, no nerve repair method has absolute advantages. When choosing a surgical approach to repair finger nerve injury, we must comprehensively consider various factors, especially the gap size of the nerve defect, and postoperative complications. Type of study/level of evidence Therapeutic IV.

Outcome After Reconstruction of 43 Digital Nerve Defects With Muscle-in-Vein Conduits

PURPOSE

Muscle-in-vein conduits provide an alternative for bridging digital nerve defects when tension-free suture is not possible. Low donor site morbidity and absence of additional costs are favorable advantages compared with autografts or conduits.

METHODS

We retrospectively reviewed 37 patients with 43 defects of proper palmar digital nerves. Primary repair by muscle-in-vein conduits was performed in 22 cases, whereas 21 cases underwent secondary reconstruction. Recovery of sensibility was assessed using static and moving 2-point discrimination and Semmes-Weinstein monofilament testing. Results were compared with the contralateral side serving as a control. Outcome data were stratified according to international guidelines and evaluated for differences in terms of age, gap length, time of reconstruction, and concomitant injuries.

RESULTS

The median gap length was 20 mm (range, 9-60 mm). After a median follow-up of 25.0 months (interquartile range, 29.0 months), the median static and moving 2-point discrimination were 7.0 mm and 5.0 mm (interquartile range, 3.0 mm), respectively. The evaluation with Semmes-Weinstein monofilament revealed a median reduction of sensibility of 2 levels compared with the contralateral side. According to the American Society for Surgery of the Hand guidelines, 81.4% of the results were classified as excellent or good, whereas fair and poor results were noted in 9.3% of the cases each. The modified Highet and Sander's criteria rated complete clinical recovery in 13 cases; 23 results were regarded as S3+.

CONCLUSIONS

Muscle-in-vein conduits can be considered for primary and secondary reconstruction of digital nerves. Successful sensory recovery in terms of measurable 2-point discrimination was achieved in 91% of all cases.

TYPE OF STUDY/LEVEL OF EVIDENCE

Therapeutic IV.

A Multicenter Prospective Randomized Comparison of Conduits Versus Decellularized Nerve Allograft for Digital Nerve Repairs

PURPOSE

While there are advantages and disadvantages to both processed nerve allografts (PNA) and conduits, a large, well-controlled prospective study is needed to compare the efficacy and to delineate how each of these repair tools can be best applied to digital nerve injuries. We hypothesized that PNA digital nerve repairs would achieve superior functional recovery for longer length gaps compared with conduit-based repairs.

METHODS

Patients (aged 18-69 years) presenting with suspected acute or subacute (less than 24 weeks old) digital nerve injuries were recruited to prticipate at 20 medical centers across the United States. After stratification to short (5-14 mm) and long (15-25 mm) gap subgroups, the patients were randomized (1:1) to repair with either a commercially available PNA or collagen conduit. Baseline and outcomes assessments were obtained either before or immediately after surgery and planned at 3-, 6-, 9-, and 12-months after surgery. All assessors and patients were blinded to the treatment arm.

RESULTS

In total, 220 patients were enrolled, and 183 patients completed an acceptable last evaluable visit (at least 6 months and not more than 15 months postrepair). At last follow-up, for the short gap repair groups, average static two-point discrimination was 7.3 ± 2.8 mm for PNA and 7.5 ± 3.1 mm for conduit repairs. For the long gap group, average static two-point discrimination was significantly lower at 6.1 ± 3.3 mm for PNA compared with 7.5 ± 2.4 mm for conduit repairs. Normal sensation (American Society for Surgery of the Hand scale) was achieved in 40% of PNA long gap repairs, which was significantly more than the 18% observed in long conduit patients. Long gap conduits had more clinical failures (lack of protective sensation) than short gap conduits.

CONCLUSIONS

Although supporting similar levels of nerve regeneration for short gap length digital nerve repairs, PNA was clinically superior to conduits for long gap reconstructions.

TYPE OF STUDY/LEVEL OF EVIDENCE

Therapeutic I.

Muscle-in-Vein Conduits for the Treatment of Symptomatic Neuroma of Sensory Digital Nerves

Background: Considering the debilitating burden of neuroma resulting in a significant loss of function and excruciating pain, the use of muscle-in-vein conduits (MVCs) for the reconstruction of painful neuroma of sensory nerves of the fingers was assessed. Methods: We retrospectively analyzed 10 patients who underwent secondary digital nerve repair by MVCs. The recovery of sensibility was evaluated by static and moving two-point discrimination (2PDs, 2PDm) and Semmes-Weinstein monofilament testing (SWM). The minimum follow-up was set 12 months after the operation. Results: The median period between trauma and nerve repair was 13.4 weeks (IQR 53.5). After neuroma resection, defects ranged from 10–35 mm (mean 17.7 mm, SD 0.75). The successful recovery of sensibility was achieved in 90% of patients after a median follow-up of 27.0 months (IQR 31.00). The mean 2PDs and 2PDm was 8.1 mm (SD 3.52) and 5.2 mm (SD 2.27), respectively. Assessment by SWM resulted in a mean value of 3.54 (SD 0.69). Reduction in pain was achieved among all patients; eight patients reported the complete relief of neuropathic pain. There was no recurrence of neuroma in any patient. Conclusions: Muscle-in-vein conduits provide an effective treatment for painful neuroma of digital nerves, resulting in satisfactory restoration of sensory function and relief of pain.

Digital Nerve Reconstruction

Tension-free primary digital nerve repair may be unachievable in the presence of a nerve defect and require digital nerve reconstruction. Multiple techniques are available for reconstruction of a digital nerve defect using conduits, autograft, and allograft. Multiple comparison studies exist in the literature, suggesting similar results with autograft and allograft reconstruction, with several comparison studies suggesting inferior outcomes with conduit repair.

A Retrospective Case Series of Peripheral Mixed Nerve Reconstruction Failures Using Processed Nerve Allografts

BACKGROUND

Favorable rates of meaningful recovery (≥M3/S3) of processed nerve allografts (PNAs) for mixed and motor nerve injuries have been reported, but there are few reports of patients having complete PNA failure (M0/S0). The purpose of this study was to describe the outcomes, including rate of complete failures, in a case series of patients who underwent PNA for peripheral mixed nerve reconstructions.

METHODS

A retrospective review of outcomes between May 2018 to September 2020 was performed. Consecutive patients who underwent nerve reconstruction (>15 mm) with PNA for a peripheral mixed nerve injury of the upper or lower extremity were eligible. Those who returned to clinic for a 10-month postoperative visit were included in this study. The primary outcome was whether the patient was defined as having a complete failure (M0/S0).

RESULTS

A total of 22 patients underwent a PNA during the time period; 14 patients participated in follow-up and were included (average age: 34.7 years) with a mean follow-up of 11.9 months. The average gap length was 46.4 mm (range 15-110 mm). At their 10-month postoperative visit, no patients had any motor or sensory improvement; all patients were deemed as having complete failure. Four patients underwent or were planned for subsequent revision surgery.

CONCLUSIONS

In this study, we demonstrated a high number of complete failures, with all 14 included patients sustaining a complete failure (100% failure rate) at a minimum 10-month follow-up visit. Failure in this case series was not observed to affect one nerve type, location, or be related to preoperative injury size.

Clinical Outcomes of Symptomatic Neuroma Resection and Reconstruction with Processed Nerve Allograft

Background:

Neuromas causing sensory disturbance can substantially affect nerve function and quality of life. Historically, passive termination of the nerve end and proximal relocation to muscle or bone has been performed after neuroma resection, but this method does not allow for neurologic recovery or prevent recurrent neuromas. The use of processed nerve allografts (PNAs) for intercalary reconstruction of nerve defects following neuroma resection is reasonable for neuroma management, although reported outcomes are limited. The purpose of this study was to assess the outcomes of pain reduction and functional recovery following neuroma resection and intercalary nerve reconstruction using PNA.

Methods:

Data on outcomes of PNA use for peripheral nerve reconstruction were collected from a multicenter registry study. The registry database was queried for upper extremity nerve reconstruction with PNA after resection of symptomatic neuroma. Patients completing both pain and quantitative sensory assessments were included in the analysis. Improvement in pain-related symptoms was determined via patient self-reported outcomes and/or the visual analog scale. Meaningful sensory recovery was defined as a score of at least S3 on the Medical Research Council Classification scale.

Results:

Twenty-five repairs involving 21 patients were included in this study. The median interval from injury to reconstruction was 386 days, and the average nerve defect length was 31 mm. Pain improved in 80% of repairs. Meaningful sensory recovery was achieved in 88% of repairs.

Conclusion:

Neuroma resection and nerve reconstruction using PNA can reduce or eliminate chronic peripheral nerve pain and provide meaningful sensory recovery.

Evidence-Based Approach to Timing of Nerve Surgery: A Review

ABSTRACT

Events causing acute stress to the health care system, such as the COVID-19 pandemic, place clinical decisions under increased scrutiny. The priority and timing of surgical procedures are critically evaluated under these conditions, yet the optimal timing of procedures is a key consideration in any clinical setting. There is currently no single article consolidating a large body of current evidence on timing of nerve surgery. MEDLINE and EMBASE databases were systematically reviewed for clinical data on nerve repair and reconstruction to define the current understanding of timing and other factors affecting outcomes. Special attention was given to sensory, mixed/motor, nerve compression syndromes, and nerve pain. The data presented in this review may assist surgeons in making sound, evidence-based clinical decisions regarding timing of nerve surgery.

Comparison of nerve conduits and nerve graft in digital nerve regeneration: A systematic review and meta-analysis

The goal of this systematic review and meta-analysis was to compare nerve conduits and nerve graft for peripheral nerve regeneration. This type of lesion frequently causes disability due to pain, paresthesia and motor deficit. On the PICO process, "P" corresponded to patients with peripheral digital nerve lesions of any age, gender or ethnicity, "I" to interventions with nerve conduits or nerve graft, "C" to the control group with no treatment, placebo or receiving other treatment, and "O" to outcome assessment of nerve regeneration. Initial search found in 3859 studies, including 2001 duplicates. The remaining 1858 studies were selected by title and/or abstract; 1798 articles were excluded, leaving 60 articles for full-text review. Thirty-nine of these 60 reports were excluded as not meeting our inclusion criteria, and 21 articles were ultimately included in the systematic review. For patients older than 40 years, there was a greater mean improvement on S2PD and M2PD tests with grafting, which seemed to be the better surgical technique, positively impacting prognosis. On the M2PD test, there was significantly greater improvement in 11-17.99 mm defects with grafting (P < 0.001); this finding should guide surgical strategy in peripheral nerve regeneration, to ensure better outcomes.

Immediate allograft reconstruction of the infraorbital nerve following resection of polyostotic fibrous dysplasia lesion

Processed nerve allografts (PNA) have increasingly been used as alternative to autogenous nerve grafts to repair nerve injuries in oral-maxillofacial surgeries. This case report describes an immediate PNA reconstruction of infraorbital nerve injury sustained during the ablation of a large expansile polyostotic fibrous dysplasia centered in the left maxilla.

A Multicenter Matched Cohort Study of Processed Nerve Allograft and Conduit in Digital Nerve Reconstruction

PURPOSE

Biomaterials used to restore digital nerve continuity after injury associated with a defect may influence ultimate outcomes. An evaluation of matched cohorts undergoing digital nerve gap reconstruction was conducted to compare processed nerve allograft (PNA) and conduits. Based on scientific evidence and historical controls, we hypothesized that outcomes of PNA would be better than for conduit reconstruction.

METHODS

We identified matched cohorts based on patient characteristics, medical history, mechanism of injury, and time to repair for digital nerve injuries with gaps up to 25 mm. Data were stratified into 2 gap length groups: short gaps of 14 mm or less and long gaps of 15 to 25 mm. Meaningful sensory recovery was defined as a Medical Research Council scale of S3 or greater. Comparisons of meaningful recovery were made by repair method between and across the gap length groups.

RESULTS

Eight institutions contributed matched data sets for 110 subjects with 162 injuries. Outcomes data were available in 113 PNA and 49 conduit repairs. Meaningful recovery was reported in 61% of the conduit group, compared with 88% in the PNA group. In the group with a 14-mm or less gap, conduit and PNA outcomes were 67% and 92% meaningful recovery, respectively. In the 15- to 25-mm gap length group, conduit and PNA outcomes were 45% and 85% meaningful recovery, respectively. There were no reported adverse events in either treatment group.

CONCLUSIONS

Outcomes of digital nerve reconstruction in this study using PNA were consistent and significantly better than those of conduits across all groups. As gap lengths increased, the proportion of patients in the conduit group with meaningful recovery decreased. This study supports the use of PNA for nerve gap reconstruction in digital nerve reconstructions up to 25 mm.

TYPE OF STUDY/LEVEL OF EVIDENCE

Therapeutic III.

Implantation of Acellular Nerve Allograft Using Nerve Connectors

Background: Nerve connectors are short nerve conduits used to approximate nerve ends. Acellular nerve allografts are viable alternatives when direct repair is not possible but do not produce exudate essential for fibrin clot formation. We hypothesize that acellular nerve allograft implanted using nerve connectors must have end-to-end contact with the in situ nerve stumps to support nerve regeneration. Methods: Sixty Sprague Dawley rats underwent a 14-mm unilateral tibial nerve injury and subsequent repair using various combinations of acellular nerve grafts and nerve connectors. Proximal repairs for all groups utilized direct contact with the nerve stump within connector. Variations in distal repair methods (allograft length, nerve gap, and connector length) defined our 4 groups-group A: 14 mm allograft, no distal gap, and distal connector; group B: 11.5 mm allograft, 2.5 mm distal gap, and distal connector; group C: 9 mm allograft, 5 mm distal gap, and distal connector; group D: 14 mm allograft, no distal gap, and no distal connector. At 3 months post-repair, function and histomorphology were assessed. Results: Developed muscle force was significantly lower in group C (0.073 ± 0.077 N) compared with the other 3 groups (group A = 0.529 ± 0.312 N, group B = 0.461 ± 0.462 N, and group D = 0.409 ± 0.327 N). Axon counts were significantly lower in group C (2121 ± 389) compared with group A (6401 ± 855), group B (4710 ± 755), and group D (4450 ± 126). There was no statistically significant difference in G-ratios (myelination) between groups (P > .05). Conclusion: Nerve regeneration was significantly impaired as the gap distance between the distal end of the allograft and the distal nerve stump increased to 5 mm.

Bench-to-Bedside Lessons Learned: Commercialization of an Acellular Nerve Graft

Peripheral nerve injury can result in debilitating outcomes including loss of function and neuropathic pain. Although nerve repair research and therapeutic development are widely studied, translation of these ideas into clinical interventions has not occurred at the same rate. At the turn of this century, approaches to peripheral nerve repair have included microsurgical techniques, hollow conduits, and autologous nerve grafts. These methods provide satisfactory results; however, they possess numerous limitations that can prevent effective surgical treatment. Commercialization of Avance, a processed nerve allograft, sought to address limitations of earlier approaches by providing an off-the-shelf alternative to hollow conduits while maintaining many proregenerative properties of autologous grafts. Since its launch in 2007, Avance has changed the landscape of the nerve repair market and is used to treat tens of thousands of patients. Although Avance has become an important addition to surgeon and patient clinical options, the product's journey from bench to bedside took over 20 years with many research and commercialization challenges. This article reviews the events that have brought a processed nerve allograft from the laboratory bench to the patient bedside. Additionally, this review provides a perspective on lessons and considerations that can assist in translation of future medical products.

Distal Digital Nerve Repair Using Nerve Allograft With a Dermal Substitute: A Case Report

Background: Distal digital nerve repairs can present unique challenges for hand surgeons due to their sensitive location and ongoing difficulty obtaining soft tissue coverage in this region. Although autografts and nerve conduits have been shown to be of benefit with nerve gaps, they can have morbidities associated with their use. Nerve allografts have become a viable option over the past decade as their use has increased and data are now showing similar outcomes, particularly in short gap segments. Flaps and skin grafts are traditional coverage options for full thickness wounds but can pose challenges with multiple digit involvement, depth of wound, and critical structures exposed. Methods: We present a case where nerve allograft was used for distal digital nerve repair. Due to the distal nature of the nerve repair in the index digit distal to the trifurcation, the distal end of the nerve graft was connected to multiple small nerve ends. Dermal substitute was placed to achieve distal coverage of the affected digits. Results: At 6-month follow-up, the patient demonstrated improved strength, normal sensation, and full return of digital function. Conclusion: Nerve allograft can be used in combination with dermal skin substitute to achieve normal sensation and return of digital function following distal digital nerve injuries.

Restoration of Neurological Function Following Peripheral Nerve Trauma

Following peripheral nerve trauma that damages a length of the nerve, recovery of function is generally limited. This is because no material tested for bridging nerve gaps promotes good axon regeneration across the gap under conditions associated with common nerve traumas. While many materials have been tested, sensory nerve grafts remain the clinical “gold standard” technique. This is despite the significant limitations in the conditions under which they restore function. Thus, they induce reliable and good recovery only for patients < 25 years old, when gaps are <2 cm in length, and when repairs are performed <2–3 months post trauma. Repairs performed when these values are larger result in a precipitous decrease in neurological recovery. Further, when patients have more than one parameter larger than these values, there is normally no functional recovery. Clinically, there has been little progress in developing new techniques that increase the level of functional recovery following peripheral nerve injury. This paper examines the efficacies and limitations of sensory nerve grafts and various other techniques used to induce functional neurological recovery, and how these might be improved to induce more extensive functional recovery. It also discusses preliminary data from the clinical application of a novel technique that restores neurological function across long nerve gaps, when repairs are performed at long times post-trauma, and in older patients, even under all three of these conditions. Thus, it appears that function can be restored under conditions where sensory nerve grafts are not effective.

Sensory Outcomes in Digital Nerve Repair Techniques: An Updated Meta-analysis and Systematic Review

Background: Injuries to digital nerves are common with trauma to the hand, often requiring surgery. Surgical management of these injuries can be performed using several techniques: direct repair (neurorrhaphy), autograft, allograft, and conduit repair. In light of increasing the availability and use of various digital nerve repair techniques, a new systematic review and meta-analysis was undertaken to comparatively review the available evidence to determine any differences in outcomes to better guide treatment in cases with digital nerve gaps. Methods: Current literature on sensory outcomes of various digital nerve repair techniques was reviewed using static 2-point discrimination (S2PD), moving 2-point discrimination (M2PD), Semmes-Weinstein monofilament testing (SWMF), and complication rates as outcomes of interest. After inclusion and exclusion criteria were applied, 15 articles were reviewed and 625 nerve repairs were analyzed. Results: The average gap length for allograft repair, autograft repair, and conduit repair was 15.4, 24.7, and 13.4 mm, respectively. For S2PD outcomes, autograft repair was statistically superior to all other forms of repair. Allograft trended higher than neurorrhaphy and conduit repair, but results were not statistically significant. For SWMF outcomes, autograft repair was statistically superior to conduit repair and neurorrhaphy; it was statistically comparable with allograft repair. Allograft performed statistically superior to conduit repair relative to M2PD. Conclusions: Based on the current updated meta-analysis using newer data and techniques, we found that all available techniques have reasonable outcomes. Yet when managing a digital nerve injury with a gap, thereby excluding direct neurorrhaphy, both autograft and allograft performed comparably and were superior to conduit repair.

Peripheral nerve repair throughout the body with processed nerve allografts: Results from a large multicenter study

BACKGROUND

Peripheral nerve damage resulting in pain, loss of sensation, or motor function may necessitate a reconstruction with a bridging material. The RANGER® Registry was designed to evaluate outcomes following nerve repair with processed nerve allograft (Avance® Nerve Graft; Axogen; Alachua, FL). Here we report on the results from the largest peripheral nerve registry to-date.

METHODS

This multicenter IRB-approved registry study collected data from patients repaired with processed nerve allograft (PNA). Sites followed their own standard of care for patient treatment and follow-up. Data were assessed for meaningful recovery, defined as ≥S3/M3 to remain consistent with previously published results, and comparisons were made to reference literature.

RESULTS

The study included 385 subjects and 624 nerve repairs. Overall, 82% meaningful recovery (MR) was achieved across sensory, mixed, and motor nerve repairs up to gaps of 70 mm. No related adverse events were reported. There were no significant differences in MR across the nerve type, age, time-to-repair, and smoking status subgroups in the upper extremity (p > .05). Significant differences were noted by the mechanism of injury subgroups between complex injures (74%) as compared to lacerations (85%) or neuroma resections (94%) (p = .03) and by gap length between the <15 mm and 50-70 mm gap subgroups, 91 and 69% MR, respectively (p = .01). Results were comparable to historical literature for nerve autograft and exceed that of conduit.

CONCLUSIONS

These findings provide clinical evidence to support the continued use of PNA up to 70 mm in sensory, mixed and motor nerve repair throughout the body and across a broad patient population.

Cadaver Nerve Grafts: Past, Present and Future

Nerve grafts represent an invaluable tool, when reconstructing nerve defects of more than 1 cm. Historically, the criterion standard use of autografts has relied on the premise of using nonessential sensory nerves to fulfill the principle of replacing "like with like," while simultaneously minimizing the infliction of undue morbidity on the patient. The reconstructive surgeon thus faces a dilemma when extensive nerve damage requires reconstruction, or when donor nerves are not available or limited such as in the pediatric population. Cadaver nerve grafts (CNG) uniquely allow for reconstruction of large nerve lesions without the presence of host morbidity. The following article reviews the use of CNG, its indications, advantages, and disadvantages, as well as provides some case studies of real-world application. In addition, an insight into the future perspectives of CNG is provided.

A Retrospective Case Series Reporting the Outcomes of Avance Nerve Allografts in the Treatment of Peripheral Nerve Injuries

BACKGROUND

Acellular nerve allografts are a viable treatment modality for bridging nerve gaps. Several small studies have demonstrated results equal to those of autologous grafts; however, there is information lacking with regard to outcomes for wider indications. The authors evaluated the outcomes of patients treated with a nerve allograft in a variety of clinical situations.

METHODS

A retrospective chart analysis was completed between April of 2009 and October of 2017. Inclusion criteria were age 18 years or older at the time of surgery and treatment with a nerve allograft. Patients were excluded if they had not been followed up for a minimum of 6 months. The modified Medical Research Council Classification was used to monitor motor and sensory changes in the postoperative period.

RESULTS

Two hundred seven nerve allografts were used in 156 patients; of these, 129 patients with 171 nerve allografts fulfilled the inclusion criteria. Seventy-seven percent of patients achieved a sensory outcome score of S3 or above and 36 percent achieved a motor score of M3 or above. All patients with chronic pain had improvement of their symptoms. Graft length and diameter were negatively correlated with reported outcomes. One patient elected to undergo revision surgery, and the original graft was shown histologically to have extensive central necrosis. Anatomically, allografts used for lower limb reconstruction yielded the poorest results. All chronic patients had a significantly lower postoperative requirement for analgesia, and allografts were effective in not only reducing pain but also restoring a functional level of sensation.

CONCLUSIONS

This study supports the wider application of allografts in managing nerve problems. However, caution must be applied to the use of long grafts with larger diameters.

CLINICAL QUESTION/LEVEL OF EVIDENCE

Therapeutic, IV.

Side-to-side supercharging nerve allograft enhances neurotrophic potential

INTRODUCTION

Critical limitations of processed acellular nerve allograft (PNA) are linked to Schwann cell function. Side-to-side bridge grafting may enhance PNA neurotrophic potential.

METHODS

Sprague-Dawley rats underwent tibial nerve transection and immediate repair with 20-mm PNA (n = 33) or isograft (ISO; n = 9) or 40-mm PNA (n = 33) or ISO (n = 9). Processed acellular nerve allograft groups received zero, one, or three side-to-side bridge grafts between the peroneal nerve and graft. Muscle weight, force generation, and nerve histomorphology were tested 20 weeks after repair. Selected animals underwent neuron back labeling with fluorescent dyes.

RESULTS

Inner axon diameters, g-ratios, and axon counts were smaller in the distal vs proximal aspect of each graft (P < .05). Schwann cell counts were greater, with a lower proportion of senescent cells for groups with bridges (P < .05). Retrograde labeling demonstrated that 6.6% to 17.7% of reinnervating neurons were from the peroneal pool.

DISCUSSION

Bridge grafting positively influenced muscle recovery and Schwann cell counts and senescence after long PNA nerve reconstruction.

Cadaveric Nerve Allograft: Single Center's Experience in a Variety of Peripheral Nerve Injuries

The purpose of this study is to report a single center's experience with cadaveric nerve allograft (CNA) for functional restoration after traumatic nerve injuries including the head and neck region. Sixteen patients were included in the current study. Ages ranged from 5 to 62 years, with a mean age of 35 years. The main indication for the use of CNA was nerve gaps of at least 10 mm in which both the proximal and distal stumps of the injured nerves were available. Only allografts from cadavers were used, and none of the patients underwent immunosuppressive treatment. Denervation time average was 12 weeks, with an average gap length of 65 mm. Most cases were located in the upper extremity (73%) and 80% were secondary to trauma. Most nerves involved were sensory, followed by mixed nerves and 2 patients with facial paralysis. Sensory recovery was graded as good and excellent in 91.7%. Motor recovery was graded as good in 33%. The results of the current study suggest that peripheral nerve injuries can successfully be treated by the use of CNA and may be used in larger nerve gaps and for unconventional uses, although caution should be used specifically in mixed or motor nerves and high level of injury. Avoiding donor site morbidity, minimizing operative time, and availability are the most important advantages of using CNA over autologous nerve grafts.

A Comparison Between Two Collagen Nerve Conduits and Nerve Autograft: A Rat Model of Motor Nerve Regeneration

PURPOSE

To compare recovery in a rat model of sciatic nerve injury using a novel polyglycolic acid (PGA) conduit, which contains collagen fibers within the tube, as compared with both a hollow collagen conduit and nerve autograft. We hypothesize that a conduit with a scaffold will provide improved nerve regeneration over hollow conduits and demonstrate no significant differences when compared with autograft.

METHODS

A total of 72 Sprague-Dawley rats were randomized into 3 experimental groups, in which a unilateral 10-mm sciatic defect was repaired using either nerve autograft, a hollow collagen conduit, or a PGA collagen-filled conduit. Outcomes were measured at 12 and 16 weeks after surgery, and included bilateral tibialis anterior muscle weight, voltage and force maximal contractility, assessment of ankle contracture, and nerve histology.

RESULTS

In all groups, outcomes improved between 12 and 16 weeks. On average, the autograft group outperformed both conduit groups, and the hollow conduit demonstrated improved outcomes when compared with the PGA collagen-filled conduit. Differences in contractile force, however, were significant only at 12 weeks (autograft > hollow collagen conduit > PGA collagen-filled conduit). At 16 weeks, contractile force demonstrated no significant difference but corroborated the same absolute results (autograft > hollow collagen conduit > PGA collagen-filled conduit).

CONCLUSIONS

Nerve repair using autograft provided superior motor nerve recovery over the 2 conduits for a 10-mm nerve gap in a murine acute transection injury model. The hollow collagen conduit demonstrated superior results when compared with the PGA collagen-filled conduit.

CLINICAL RELEVANCE

The use of a hollow collagen conduit provides superior motor nerve recovery as compared with a PGA collagen-filled conduit.

No Difference in Outcomes Detected Between Decellular Nerve Allograft and Cable Autograft in Rat Sciatic Nerve Defects

BACKGROUND

Nerve injuries with a gap/defect represent a clinical challenge without a clear solution. Reconstruction with cable autografts is a common treatment technique, and repair with decellular nerve allograft is a newer option. The purpose of this study was to compare the functional outcomes of reconstruction with cable autografts with those of matched-diameter decellular nerve allografts to evaluate the relative importance of diameter as well as the autograft-versus-allograft nature of the reconstruction.

METHODS

A unilateral 10-mm sciatic nerve defect was created in 81 genetically identical male Lewis rats and then repaired with a reverse autograft, 4 or 5 sural nerve cable autografts, or a matched-diameter decellular nerve allograft. In each group, at each time point (12, 16, and 20 weeks), all 9 animals underwent functional testing and 5 of the 9 underwent histologic analysis. Functional testing included bilateral measurements of the isometric tetanic force of the tibialis anterior (primary outcome), the weight of the tibialis anterior, and the gastrocnemius compound muscle action potential (CMAP) latency. Histologic evaluation included an axon count as well as measurement of the axon density, fiber diameter, myelin thickness, and G-ratio.

RESULTS

The repair groups did not differ significantly in terms of isometric tetanic force, muscle weight, or CMAP latency, but these measurements did differ significantly according to the time after surgery (p < 0.05). The isometric tetanic force percent recovery (width of the 95% confidence interval) for the reverse autograft, cable autograft, and decellular nerve allograft was 57.7% (15.6%), 57.0% (23.4%), and 56.0% (19.7%), respectively, at 12 weeks; 69.1% (14.7%), 65.6% (18.5%), and 65.9% (29.1%) at 16 weeks; and 72.5% (18.2%), 73.7% (25.6%), and 71.8% (22.4%) at 20 weeks. Isometric tetanic force and muscle weight recovery were greater and CMAP latency was shorter at 20 and 16 weeks after surgery than they were at 12 weeks. The treatment type did not affect any of the histologic outcomes.

CONCLUSIONS

In this animal study, we found that matched-diameter decellular nerve allograft was not significantly different from reverse autograft or cable graft reconstruction in terms of function and histologic outcomes. These findings support decellular nerve allograft as a viable treatment option for nerve reconstruction.

CLINICAL RELEVANCE

This study showed that decellular nerve allograft was no different from cable or reverse autograft in terms of outcome measures in a rat sciatic nerve defect model. If these results are applicable clinically, it would obviate the need for autograft nerve harvest and its ensuing donor site morbidity.

Effect of Reverse End-to-Side (Supercharging) Neurotization in Long Processed Acellular Nerve Allograft in a Rat Model

PURPOSE

Processed acellular nerve allograft (PNA) has been suggested as a convenient tool for overcoming short and medium nerve defects. Although the clinical implications are unclear, animal data suggest that PNA becomes less effective at longer lengths. Although reverse or supercharging end-to-side nerve transfer may improve the neurotrophic potential in chronically denervated nerve tissue, the application of this strategy to long acellular nerve allograft has not been previously investigated. We hypothesized that supercharging acellular nerve allograft would increase its effective length.

METHODS

Sprague-Dawley and Thy1-green fluorescent protein Sprague-Dawley rats underwent transection of the tibial nerve, followed by immediate repair with 20-, 40-, or 60-mm acellular nerve allografts processed identically to commercially available human acellular nerve allograft (AxoGen, Inc., Alachua, FL) or isograft. Half of the allograft group was supercharged with a reverse end-to-side transfer from the ipsilateral peroneal nerve. At 10 weeks, the reconstructed nerve in the Thy1-green fluorescent rat groups were exposed and examined under a fluorescence-enabled microscope. At 20 weeks, the remaining rats underwent motor testing and tissue harvest for morphological examination.

RESULTS

In comparison with a nonenhanced allograft, supercharging had a statistically significant positive impact on the reinnervated muscle normalized force generation and distal axon counts for all graft sizes. Muscles in the supercharged group were heavier than those in the allograft group for the 40-mm-length grafts and G-ratio measurements were higher in the supercharged allograft group for 60-mm-length grafts only.

CONCLUSIONS

This study supports that hypothesis that supercharging nerve transfer improves axon regeneration within PNA.

CLINICAL RELEVANCE

When an appropriate donor nerve is available, supercharging nerve transfer may improve nerve regeneration in PNA across long nerve defects.

Collagen Nerve Conduits and Processed Nerve Allografts for the Reconstruction of Digital Nerve Gaps: A Single-Institution Case Series and Review of the Literature

OBJECTIVE

A single-institution case series is reported and a review of the literature on the outcomes of digital nerve gap reconstruction with the NeuraGen type 1 collagen nerve conduit (Integra Life Sciences, Plainsboro New Jersey, USA) and the Avance Nerve Graft (Axogen Inc., Alachua, Florida, USA) is presented.

METHODS

Thirty-seven patients were included with a minimal follow-up of 12 months. Primary outcome was postoperative sensory recovery measured by static 2-point discrimination test or the Semmes-Weinstein monofilament test. Secondary outcome measurements were perioperative or postoperative complications. Final outcome data were stratified to grade results as excellent, good, or poor.

RESULTS

The mean nerve gap length was 14 ± 4.9 mm for the collagen conduits versus 18.4 ± 9.3 for nerve allografts. After 12 months, outcomes were graded as excellent sensory recovery in 48% of the collagen conduit repairs and 39% of the nerve allografts (P = 0.608), good in 26% of the conduits and 55% of the allografts (P = 0.074), and poor in 26% of the conduits versus 6% of the allografts (P = 0.091). One neuroma and 1 infection were reported. Graft rejection or extrusion was not observed.

CONCLUSIONS

Nerve conduits and processed nerve allografts offer convenient off-the-shelf options for digital nerve gap repair. Both techniques offer effective means of reconstructing a digital nerve gap <2.5 cm at a minimum of 12 months of follow-up. Future prospective randomized large sample size studies comparing nerve conduits with allografts are needed to perform subgroup analyses and to define their exact role in digital nerve injuries.

Recovery of Motor Function after Mixed and Motor Nerve Repair with Processed Nerve Allograft

Supplemental Digital Content is available in the text.

Background:

Severe trauma often results in the transection of major peripheral nerves. The RANGER Registry is an ongoing observational study on the use and outcomes of processed nerve allografts (PNAs; Avance Nerve Graft, AxoGen, Inc., Alachua, Fla.). Here, we report on motor recovery outcomes for nerve injuries repaired acutely or in a delayed fashion with PNA and comparisons to historical controls in the literature.

Methods:

The RANGER database was queried for mixed and motor nerve injuries in the upper extremities, head, and neck area having completed greater than 1 year of follow-up. All subjects with sufficient assessments to evaluate functional outcomes were included. Meaningful recovery was defined as ≥M3 on the Medical Research Council scale. Demographics, outcomes, and covariate analysis were performed to further characterize this subgroup.

Results:

The subgroup included 20 subjects with 22 nerve repairs. The mean ± SD (minimum–maximum) age was 38 ± 19 (16–77) years. The median repair time was 9 (0–133) days. The mean graft length was 33 ± 17 (10–70) mm with a mean follow-up of 779 ± 480 (371–2,423) days. Meaningful motor recovery was observed in 73%. Subgroup analysis showed no differences between gap lengths or mechanism of injury. There were no related adverse events.

Conclusions:

PNAs were safe and provided functional motor recovery in mixed and motor nerve repairs. Outcomes compare favorably to historical controls for nerve autograft and exceed those for hollow tube conduit. PNA may be considered as an option when reconstructing major peripheral nerve injuries.

Emerging Technologies in Upper Extremity Surgery: Polyvinyl Alcohol Hydrogel Implant for Thumb Carpometacarpal Arthroplasty and Processed Nerve Allograft and Nerve Conduit for Digital Nerve Repairs

In the field of upper extremity surgery there are myriad new and developing technologies. The purpose of this article is to highlight a few of the most compelling new technologies and review their background, indications for use, and most recently reported outcomes in clinical practice.

A Survey of the Prevalence and Practice Patterns of Human Acellular Nerve Allograft Use

Supplemental Digital Content is available in the text.

Background:

There have been many technical and scientific advances over the last decade in peripheral nerve surgery. Human acellular nerve graft (HANA) has become increasingly popular but current practice patterns among hand surgeons have yet to be defined. Coding practices may not have kept up with this innovation. A 26 question survey of hand surgeons was performed to evaluate the adoption of HANA, and current coding and billing practices. The survey was sent to hand surgeons trained in orthopedic, plastic, general, and neuro surgery. The survey was designed and implemented by the Mayo Clinic Survey Center.

Results:

Four hundred sixty-one responses to the survey were received. Most respondents currently use HANA (70%). Of those surgeons who do use HANA, nearly all use it less than 10 times per month (98%). There was no significant difference in the use of HANA across different specialties. There was a significant difference in HANA use depending on practice type with higher use by those in group private practice (57%) compared with academic practice (28%), solo practice (12%), and other practice environment (3%). There was a significant difference in HANA use depending on the number of years in practice. Those in practice less than 5 years used HANA the most (32%), followed by > 20 years in practice (27%), 6–10 years in practice (16%), 16–20 years in practice (14%), and 11–15 years in practice (11%). When asked the Current Procedural Terminology code they would use to bill for the procedure of choice, the most common response was 64910 (nerve repair with synthetic conduit or vein allograft).

Conclusions:

HANA has surpassed nerve conduit as the traditional gold standard in our study with nearly 70% of hand surgeons using HANA in their practice and a greater percentage of respondents choosing HANA as their first choice to repair as compared with nerve conduit, nerve autograft, or vein graft. There remains confusion regarding appropriate billing practices for the use of HANA. Due to its common use, a Current Procedural Terminology code should specifically designated for the use of HANA in the hand.

Biomimetic neural scaffolds: a crucial step towards optimal peripheral nerve regeneration

Peripheral nerve injury is a common disease that affects more than 20 million people in the United States alone and remains a major burden to society. The current gold standard treatment for critical-sized nerve defects is autologous nerve graft transplantation; however, this method is limited in many ways and does not always lead to satisfactory outcomes. The limitations of autografts have prompted investigations into artificial neural scaffolds as replacements, and some neural scaffold devices have progressed to widespread clinical use; scaffold technology overall has yet to be shown to be consistently on a par with or superior to autografts. Recent advances in biomimetic scaffold technologies have opened up many new and exciting opportunities, and novel improvements in material, fabrication technique, scaffold architecture, and lumen surface modifications that better reflect biological anatomy and physiology have independently been shown to benefit overall nerve regeneration. Furthermore, biomimetic features of neural scaffolds have also been shown to work synergistically with other nerve regeneration therapy strategies such as growth factor supplementation, stem cell transplantation, and cell surface glycoengineering. This review summarizes the current state of neural scaffolds, highlights major advances in biomimetic technologies, and discusses future opportunities in the field of peripheral nerve regeneration.

Nerve Repair with Nerve Conduits: Problems, Solutions, and Future Directions

Nerve conduits are becoming increasingly popular for the repair of peripheral nerve injuries. Their ease of application and lack of donor site morbidity make them an attractive option for nerve repair in many situations. Today, there are many different conduits to choose in different sizes and materials, giving the reconstructive surgeon many options for any given clinical problem. However, to properly utilize these unique reconstructive tools, the peripheral nerve surgeon must be familiar not only with their standard indications but also with their functional limitations. In this review, the authors identify the common applications of nerve conduits, expected results, and shortcomings of current techniques. Furthermore, future directions for nerve conduit use are identified.

The Role of Nerve Graft Substitutes in Motor and Mixed Motor/Sensory Peripheral Nerve Injuries

Alternatives to nerve autograft have been invented and approved for clinical use. The reported outcomes of these alternatives in mixed motor nerve repair in humans are scarce and marked by wide variabilities. The purpose of our Current Concepts review is to provide an evidence-based overview of the effectiveness of nerve conduits and allografts in motor and mixed sensory/motor nerve reconstruction. Nerve graft substitutes have good outcomes in mixed/motor nerves in gaps less than 6 mm and internal diameters between 3 and 7 mm. There is insufficient evidence for their use in larger-gap and -diameter nerves; the evidence remains that major segmental motor or mixed nerve injury is optimally treated with a cabled nerve autograft.

Analysis of the modifications of MRI signal of the brachial plexus of rats: Comparative study before and after freezing/thawing

The aim of this study was to compare the MRI signal of the brachial plexus and surrounding muscles before and after freezing/thawing on a murine model. A first MRI going through the brachial plexuses of 5 healthy Wistar rats was performed immediately post-mortem. A second MRI was performed after freezing at -30°C and then thawing at 20°C for 24hours. All MRI images were segmented to make nerve and muscular structures appear and calculate the average intensity of the MRI signal using the program ImageJ. The average nerve and muscular MRI signals were compared before and after freezing/thawing and rated in grayscale units between 0 and 255. The average intensity of the MRI signal of nerve structures was 40.315 grayscale units before freezing and 31.943 after freezing/thawing. The average intensity of the MRI signal of muscular structures was 25.44 grayscale units before freezing and 35.710 after freezing/thawing. Our results have shown that the intensity of the MRI signal of the brachial plexus was higher before freezing/thawing. The intensity of the MRI signal of muscles was lower than the intensity of the brachial plexus before freezing/thawing and higher after freezing/thawing in muscles than in brachial plexus. The MRI could be used in clinical practice to monitor the reinnervation after frozen nerve allografts.

A Preliminary Assessment of the Utility of Large-Caliber Processed Nerve Allografts for the Repair of Upper Extremity Nerve Injuries

Background: Cabled sensory nerve autografts are the historical gold standard for overcoming gaps in larger diameter nerves as repair utilizing large-diameter autograft risks central graft necrosis. Commercially available processed nerve allograft (PNA) is available in diameters up to 5 mm but represents an acellular 3-dimensional matrix as opposed to viable tissue. The purpose of this study is to specifically evaluate whether similar concerns regarding the use of large-caliber PNA are warranted. Methods: The RANGER Registry is an active database designed to collect injury, repair, safety, and outcomes data for PNAs (Avance® Nerve Graft; AxoGen, Inc, Alachua, Florida) according to an institutional review board-approved protocol. The database was queried for patients presenting with large-caliber nerve allograft repairs in the upper extremity. Identified patients reporting quantitative outcomes with a minimum of 9-month follow-up were included in the data set. Results: The large-caliber PNA subgroup included 13 patients with 15 injuries. The mean ± SD age was 36 ± 22 years. Large-caliber single-stranded repairs included twelve 4- to 5-mm-diameter grafts. Large-caliber cabled repairs included the combined use of 3- to 4-mm and 4- to 5-mm-diameter nerve allografts in 3 repairs. The mean nerve gap was 33 ± 10 mm with a mean follow-up time of 13 months. Available quantitative data reported meaningful recovery of sensory and motor function in 67% and 85% of the repairs, respectively. Conclusion: Although based on a small subset of patients, PNAs of up to 5 mm in diameter appear capable of supporting successful nerve regeneration.

A Multicenter, Prospective, Randomized, Pilot Study of Outcomes for Digital Nerve Repair in the Hand Using Hollow Conduit Compared With Processed Allograft Nerve

BACKGROUND

Current repair options for peripheral nerve injuries where tension-free gap closure is not possible include allograft, processed nerve allograft, and hollow tube conduit. Here we report on the outcomes from a multicenter prospective, randomized, patient- and evaluator-blinded, pilot study comparing processed nerve allograft and hollow conduit for digital nerve reconstructions in the hand.

METHODS

Across 4 centers, consented participants meeting inclusion criteria while not meeting exclusion criteria were randomized intraoperatively to either processed nerve allograft or hollow conduit. Standard sensory and safety assessments were conducted at baseline, 1, 3, 6, 9, and 12 months after reconstruction. The primary outcome was static 2-point discrimination (s2PD) testing. Participants and assessors were blinded to treatment. The contralateral digit served as the control.

RESULTS

We randomized 23 participants with 31 digital nerve injuries. Sixteen participants with 20 repairs had at least 6 months of follow-up while 12-month follow-up was available for 15 repairs. There were no significant differences in participant and baseline characteristics between treatment groups. The predominant nerve injury was laceration/sharp transection. The mean ± SD length of the nerve gap prior to repair was 12 ± 4 mm (5-20 mm) for both groups. The average s2PD for processed allograft was 5 ± 1 mm (n = 6) compared with 8 ± 5 mm (n = 9) for hollow conduits. The average moving 2PD for processed allograft was 5 ± 1 mm compared with 7 ± 5 mm for hollow conduits. All injuries randomized to processed nerve allograft returned some degree of s2PD as compared with 75% of the repairs in the conduit group. Two hollow conduits and one allograft were lost due to infection during the study.

CONCLUSIONS

In this pilot study, patients whose digital nerve reconstructions were performed with processed nerve allografts had significantly improved and more consistent functional sensory outcomes compared with hollow conduits.

Autograft Substitutes: Conduits and Processed Nerve Allografts

Manufactured conduits and allografts are viable alternatives to direct suture repair and nerve autograft. Manufactured tubes should have gaps less than 10 mm, and ideally should be considered as an aid to the coaptation. Processed nerve allograft has utility as a substitute for either conduit or autograft in sensory nerve repairs. There is also a growing body of evidence supporting their utility in major peripheral nerve repairs, gap repairs up to 70 mm in length, as an alternative source of tissue to bolster the diameter of a cable graft, and for the management of neuromas in non-reconstructable injuries.

Decellular Nerve Allografts

Multiple treatment options are available for patients who have peripheral nerve injuries with a gap. Decellular nerve allografts are one option and provide an extracellular scaffold for neuronal cells to migrate for axonal regrowth. Immunosuppression is not needed because improved nerve processing technologies have rendered decellular nerve allografts nonimmunogenic. These allografts have also shown promising results in both animal and human studies as an alternative repair option.

One-stage human acellular nerve allograft reconstruction for digital nerve defects

Human acellular nerve allografts have a wide range of donor origin and can effectively avoid nerve injury in the donor area. Very little is known about one-stage reconstruction of digital nerve defects. The present study observed the feasibility and effectiveness of human acellular nerve allograft in the reconstruction of < 5-cm digital nerve defects within 6 hours after injury. A total of 15 cases of nerve injury, combined with nerve defects in 18 digits from the Department of Emergency were enrolled in this study. After debridement, digital nerves were reconstructed using human acellular nerve allografts. The patients were followed up for 6–24 months after reconstruction. Mackinnon-Dellon static two-point discrimination results showed excellent and good rates of 89%. Semmes-Weinstein monofilament test demonstrated that light touch was normal, with an obvious improvement rate of 78%. These findings confirmed that human acellular nerve allograft for one-stage reconstruction of digital nerve defect after hand injury is feasible, which provides a novel trend for peripheral nerve reconstruction.

Clinical outcomes for Conduits and Scaffolds in peripheral nerve repair

The gold standard of peripheral nerve repair is nerve autograft when tensionless repair is not possible. Use of nerve autograft has several shortcomings, however. These include limited availability of donor tissue, sacrifice of a functional nerve, and possible neuroma formation. In order to address these deficiencies, researchers have developed a variety of biomaterials available for repair of peripheral nerve gaps. We review the clinical studies published in the English literature detailing outcomes and reconstructive options. Regardless of the material used or the type of nerve repaired, outcomes are generally similar to nerve autograft in gaps less than 3 cm. New biomaterials currently under preclinical evaluation may provide improvements in outcomes.

The influence of vascularization of transplanted processed allograft nerve on return of motor function in rats

Processed nerve allografts have become an alternative to repair segmental nerve defects, with results comparable with autografts regarding sensory recovery; however, they have failed to reproduce comparable motor recovery. The purpose of this study was to determine how revascularizaton of processed nerve allograft would affect motor recovery. Eighty-eight rats were divided in four groups of 22 animals each. A unilateral 10-mm sciatic nerve defect was repaired with allograft (group I), allograft wrapped with silicone conduit (group II), allograft augmented with vascular endothelial growth factor (group III), or autograft (group IV). Eight animals from each group were sacrificed at 3 days, and the remaining animals at 16 weeks. Revascularization was evaluated by measuring the graft capillary density at 3 days and 16 weeks. Measurements of ankle contracture, compound muscle action potential, tibialis anterior muscle weight and force, and nerve histomorphometry were performed at 16 weeks. All results were normalized to the contralateral side. The results of capillary density at 3 days were 0.99% ± 1.3% for group I, 0.33% ± 0.6% for group II, 0.05% ± 0.1% for group III, and 75.6% ± 45.7% for group IV. At 16 weeks, the results were 69.9% ± 22.4% for group I, 37.0% ± 16.6% for group II, 84.6% ± 46.6% for group III, and 108.3% ± 46.8% for group IV. The results of muscle force were 47.5% ± 14.4% for group I, 21.7% ± 13.5% for group II, 47.1% ± 7.9% for group III, and 54.4% ± 10.6% for group IV. The use of vascular endothelial growth factor in the fashion used in this study improved neither the nerve allograft short-term revascularization nor the functional motor recovery after 16 weeks. Blocking allograft vascularization from surrounding tissues was detrimental for motor recovery. The processed nerve allografts used in this study showed similar functional motor recovery compared with that of the autograft.

Sensory outcomes after reconstruction of lingual and inferior alveolar nerve discontinuities using processed nerve allograft--a case series

PURPOSE

The present study describes the results of using a processed nerve allograft, Avance Nerve Graft, as an extracellular matrix scaffold for the reconstruction of lingual nerve (LN) and inferior alveolar nerve (IAN) discontinuities.

PATIENTS AND METHODS

A retrospective analysis of the neurosensory outcomes for 26 subjects with 28 LN and IAN discontinuities reconstructed with a processed nerve allograft was conducted to determine the treatment effectiveness and safety. Sensory assessments were conducted preoperatively and 3, 6, and 12 months after surgical reconstruction. The outcomes population, those with at least 6 months of postoperative follow-up, included 21 subjects with 23 nerve defects. The neurosensory assessments included brush stroke directional sensation, static 2-point discrimination, contact detection, pressure pain threshold, and pressure pain tolerance. Using the clinical neurosensory testing scale, sensory impairment scores were assigned preoperatively and at each follow-up appointment. Improvement was defined as a score of normal, mild, or moderate.

RESULTS

The neurosensory outcomes from LNs and IANs that had been microsurgically repaired with a processed nerve allograft were promising. Of those with nerve discontinuities treated, 87% had improved neurosensory scores with no reported adverse experiences. Similar levels of improvement, 87% for the LNs and 88% for the IANs, were achieved for both nerve types. Also, 100% sensory improvement was achieved in injuries repaired within 90 days of the injury compared with 77% sensory improvement in injuries repaired after 90 days.

CONCLUSIONS

These results suggest that processed nerve allografts are an acceptable treatment option for reconstructing trigeminal nerve discontinuities. Additional studies will focus on reviewing the outcomes of additional cases.

Overcoming short gaps in peripheral nerve repair: conduits and human acellular nerve allograft

Nerve conduits and acellular nerve allograft offer efficient and convenient tools for overcoming unexpected gaps during nerve repair. Both techniques offer guidance for migrating Schwann cells and axonal regeneration though utilizing very different scaffolds. The substantially greater amount of animal and clinical data published on nerve conduits is marked by wide discrepancies in results that may be partly explained by a still poorly defined critical repair gap and diameter size. The available information on acellular allografts appears more consistently positive though this tool is also hampered by a longer but also limited critical length. This article reviews the current relative literature and examines pertinent parameters for application of both acellular allograft and nerve conduits in overcoming short nerve gaps.

The management of digital nerve injuries

A tension-free coaptation is a key factor for the successful outcome of any nerve repair. A variety of host factors influence the outcome of digital nerve repair more than the type of repair per se. Although autologous graft remains the reference standard for reconstruction of any critical digital nerve defect, allografts and conduits have assumed an increasing role.

Clinical applications of autografts, conduits, and allografts in repair of nerve defects in the hand: current guidelines

Traumatic nerve injuries are common conditions treated by hand surgeons, and the optimal treatment of a severed nerve requires providing a healthy wound bed, generous trimming to healthy nerve substance, and a minimal-tension approximation. The gold standard for repair of a critical nerve gap has been the nerve autograft. However, results are generally less favorable than direct suture. Autogenous and synthetic conduits and processed nerve allografts have been developed as less morbid and more convenient alternatives to autografts, but the reported outcomes have been uneven. Engineered neural tissues show great promise in inducing nerve regeneration across a gap.