Processed Nerve Allograft for Trigeminal Nerve Repair: Safety and Effectiveness in Sensory Nerve Reconstruction

The processed nerve allograft, chondroitinase-treated, decellularized Avance (AxoGen, Alachua, FL), has become a popular alternative to an autograft for the repair of nerve injuries, including the trigeminal nerve (1, 2).  Clinical outcome data on their safety and effectiveness in restoring sensory function of the trigeminal nerve is needed.

Sensory assessments of trigeminal nerve injuries were conducted at pre-surgical, 3, 6, and 12 months post-surgical reconstruction with Avance® Nerve Graft (AxoGen, Inc.).  Subjects with at least 6 months of follow-up were included in this analysis.  Assessments included brush stroke directional sensation (BSDS), static 2-point discrimination (s2PD), contact detection (CD), pressure pain threshold, and pressure pain tolerance. Sensory impairment scores via clinical Neurosensory Testing (NST) methods, classified as normal, mild, moderate, severe, or complete,  were assigned preoperatively and at the most recent follow-up visit. NST consists of a 3-level (A, B, and C) dropout algorithm. Level A includes BSDS and s2PD tests, level B consists of the CD test, and level C includes pain threshold and pain tolerance tests.  Adverse events such as infection, graft rejection, wound dehiscence and neuropathic pain were assessed.

The study consisted of 18 subjects with 20 trigeminal nerve reconstructions, 2 subjects had 2 reconstructions. All injuries were reconstructed with processed nerve allograft.  Fourteen subjects with 16 reconstructions had sufficient follow-up data for outcomes analysis.  The subjects were 7 males and 7 females with 12 lingual nerve, and 4 inferior alveolar nerve reconstructions. The mean age was 31 + 15 (9, 67) years old and the mean time between injury and surgery was 217 + 199 (0, 527) days. Twelve of the 16 reconstructions reported the gap length of injury, giving an average of 30 + 24 (15, 70) mm. The etiology of the injuries was reported as 10 injuries from 3^rdmolar extractions, 2 from bilateral sagittal split osteotomy (BSSO), 2 from implants, 2 from a benign tumor resection with immediate repair.

Improvements in sensory function were reported in 13 out of the 16 reconstructions with processed nerve allograft (81%).  Six repairs reported within normative limits at level A with a gap range of 15-70 mm.  Seven repairs were within normative limits at level B and 13 repairs were within normative limits at level C. NST sensory impairment scores, reported at the last follow-up visit, included 6 normal, 2 mild, 5 moderate, and 3 severe. There were no repairs reporting complete sensory impairment.  There were no adverse events recorded.  Those patients with no neuropathic pain before reported no neuropathic pain after and those patients with neuropathic pain before reported neuropathic pain after.

Processed nerve allografts were found to be safe and effective in Trigeminal sensory nerve defects between 15 and 70mm in either immediate or delayed nerve reconstruction.  These results are similar to those reported using processed nerve allografts in non-trigeminal  nerve repairs (2)

1.  Shanti RM, Ziccardi VB:  Use of Decellularized Nerve Allograft for Inferior Alveolar Nerve Reconstruction: A Case Report. JOMS 69:550-553, 2011
2. Brooks DV, Weber RV, Chao JJ, et al: Processed Nerve Allografts for Peripheral Nerve Reconstruction: A Multicenter Study of Utilization and Outcomes in Sensory, Mixed, and Motor Nerve Reconstructions.  Microsurgery  1-14, 2011