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

Current perspectives on peripheral nerve repair and management of the nerve gap

From the first surgical repair of a nerve in the 6th century, progress in the field of peripheral nerve surgery has marched on; at first slowly but today at great pace. Whether performing primary neurorrhaphy or managing multiple large nerve defects, the modern nerve surgeon has an extensive range of tools, techniques and choices available to them. Continuous innovation in surgical equipment and technique has enabled the maturation of autografting as a gold standard for reconstruction and welcomed the era of nerve transfer techniques all while bioengineers have continued to add to our armamentarium with implantable devices, such as conduits and acellular allografts. We provide the reader a concise and up-to-date summary of the techniques available to them, and the evidence base for their use when managing nerve transection including current use and applicability of nerve transfer procedures.

Nerve grafts in head and neck reconstruction

PURPOSE OF REVIEW

This article reviews recent literature on repair of peripheral nerve injuries in the head and neck with a focus on autografts, allografts, nerve conduits, and technical considerations.

RECENT FINDINGS

Contemporary nerve grafting techniques offer the potential to improve peripheral nerve outcomes and reduce donor site morbidity. A variety of donor nerves autografts have been described that offer favorable outcomes for segmental reconstruction of facial nerve defects. Recent studies have demonstrated promising results in repair of inferior alveolar nerve injuries with human allografts. Animal models describe successful reinnervation of small defects with neural conduits. The latest data do not favor protocolled nerve graft polarity or use of a motor versus sensory donor nerves.

SUMMARY

Interposition nerve grafting is the gold standard for repair of peripheral nerve injuries when a tension-free primary neurorrhaphy is not possible. Autografts are the work-horse for the majority of head and neck neural defects, however, can result in some degree of donor site morbidity. Recent developments in allografting and neural conduits have the potential to further diversify the head and neck reconstructive surgeon's armamentarium. It is unclear if nerve graft makeup or polarity affect functional outcome.

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.

Advances in the repair of segmental nerve injuries and trends in reconstruction

Despite advances in surgery, the reconstruction of segmental nerve injuries continues to pose challenges. In this review, current neurobiology regarding regeneration across a nerve defect is discussed in detail. Recent findings include the complex roles of nonneuronal cells in nerve defect regeneration, such as the role of the innate immune system in angiogenesis and how Schwann cells migrate within the defect. Clinically, the repair of nerve defects is still best served by using nerve autografts with the exception of small, noncritical sensory nerve defects, which can be repaired using autograft alternatives, such as processed or acellular nerve allografts. Given current clinical limits for when alternatives can be used, advanced solutions to repair nerve defects demonstrated in animals are highlighted. These highlights include alternatives designed with novel topology and materials, delivery of drugs specifically known to accelerate axon growth, and greater attention to the role of the immune system.

Hand Surgeon Perspectives on Upper Extremity Allograft: A Survey of the American Society for Surgery of the Hand

INTRODUCTION

Allograft tissue products have widespread applications across surgical specialties, but little data exist about surgeon attitudes toward the use of these products in the upper extremity.

METHODS

Using a web-based survey, we sought to investigate the use of and feelings toward allograft products among hand surgeons. A short questionnaire was distributed to all active members of American Society for Surgery of the Hand as of October 2015 (N = 2,578). Demographic and practice setting information was collected. Additionally, questions concerning the use of human allograft tissue products of various types including bone, skin, and soft tissues were asked.

RESULTS

Of 2,578 American Society for Surgery of the Hand members, 406 hand surgeons (15.8%) responded to the survey. A large majority (92%) reported having used allograft products in the upper extremity. Orthopedic-trained surgeons were more likely to have used bone and tendon allograft, whereas plastic and general surgery-trained surgeons were more likely to have used nerve and dermis allograft. Reduced donor site morbidity and complication rates were factors motivating surgeons to use allograft tissue.

CONCLUSIONS

In spite of variation with respect to their use, allograft tissue products are popular and interest in new products, especially to improve flexor tendon pulley reconstruction, is high.