Peripheral Nerve Healing: So Near and Yet So Far

Peripheral nerve injuries represent a considerable portion of chronic disability that especially affects the younger population. Prerequisites of proper peripheral nerve injury treatment include in-depth knowledge of the anatomy, pathophysiology, and options in surgical reconstruction. Our greater appreciation of nerve healing mechanisms and the development of different microsurgical techniques have significantly refined the outcomes in treatment for the past four decades. This work reviews the peripheral nerve regeneration process after an injury, provides an overview of various coaptation methods, and compares other available treatments such as autologous nerve graft, acellular nerve allograft, and synthetic nerve conduits. Furthermore, the formation of neuromas as well as their latest treatment options are discussed.

Acellular Nerve Allografts in Major Peripheral Nerve Repairs: An Analysis of Cases Presenting With Limited Recovery

Background: Acellular nerve allografts have been used successfully and with increasing frequency to reconstruct nerve injuries. As their use has been expanded to treat longer gap, larger diameter nerve injuries, some failed cases have been reported. We present the histomorphometry of 5 such cases illustrating these limitations and review the current literature of acellular nerve allografts. Methods: Between 2014 and 2019, 5 patients with iatrogenic nerve injuries to the median or ulnar nerve reconstructed with an AxoGen AVANCE nerve allograft at an outside hospital were treated in our center with allograft excision and alternative reconstruction. These patients had no clinical or electrophysiological evidence of recovery, and allograft specimens at the time of surgery were sent for histomorphological examination. Results: Three patients with a median and 2 with ulnar nerve injury were included. Histology demonstrated myelinated axons present in all proximal native nerve specimens. In 2 cases, axons failed to regenerate into the allograft and in 3 cases, axonal regeneration diminished or terminated within the allograft. Conclusions: The reported cases demonstrate the importance of evaluating the length and the function of nerves undergoing acellular nerve allograft repair. In long length, large-diameter nerves, the use of acellular nerve allografts should be carefully considered.

Analysis of human acellular nerve allograft combined with contralateral C7 nerve root transfer for restoration of shoulder abduction and elbow flexion in brachial plexus injury: a mean 4-year follow-up

OBJECTIVEHuman acellular nerve allograft applications have increased in clinical practice, but no studies have quantified their influence on reconstruction outcomes for high-level, greater, and mixed nerves, especially the brachial plexus. The authors investigated the functional outcomes of human acellular nerve allograft reconstruction for nerve gaps in patients with brachial plexus injury (BPI) undergoing contralateral C7 (CC7) nerve root transfer to innervate the upper trunk, and they determined the independent predictors of recovery in shoulder abduction and elbow flexion.METHODSForty-five patients with partial or total BPI were eligible for this retrospective study after CC7 nerve root transfer to the upper trunk using human acellular nerve allografts. Deltoid and biceps muscle strength, degree of shoulder abduction and elbow flexion, Semmes-Weinstein monofilament test, and static two-point discrimination (S2PD) were examined according to the modified British Medical Research Council (mBMRC) scoring system, and disabilities of the arm, shoulder, and hand (DASH) were scored to establish the function of the affected upper limb. Meaningful recovery was defined as grades of M3–M5 or S3–S4 based on the scoring system. Subgroup analysis and univariate and multivariate logistic regression analyses were conducted to identify predictors of human acellular nerve allograft reconstruction.RESULTSThe mean follow-up duration and the mean human acellular nerve allograft length were 48.1 ± 10.1 months and 30.9 ± 5.9 mm, respectively. Deltoid and biceps muscle strength was grade M4 or M3 in 71.1% and 60.0% of patients. Patients in the following groups achieved a higher rate of meaningful recovery in deltoid and biceps strength, as well as lower DASH scores (p < 0.01): age < 20 years and age 20–29 years; allograft lengths ≤ 30 mm; and patients in whom the interval between injury and surgery was < 90 days. The meaningful sensory recovery rate was approximately 70% in the Semmes-Weinstein monofilament test and S2PD. According to univariate and multivariate logistic regression analyses, age, interval between injury and surgery, and allograft length significantly influenced functional outcomes.CONCLUSIONSHuman acellular nerve allografts offered safe reconstruction for 20- to 50-mm nerve gaps in procedures for CC7 nerve root transfer to repair the upper trunk after BPI. The group in which allograft lengths were ≤ 30 mm achieved better functional outcome than others, and the recommended length of allograft in this procedure was less than 30 mm. Age, interval between injury and surgery, and allograft length were independent predictors of functional outcomes after human acellular nerve allograft reconstruction.