The influence of timing on the functional and morphological result after nerve grafting: an experimental study in rabbits

The Tinel Sign and Myelinated Axons in the Cross-Face Nerve Graft: Predictors of Smile Reanimation Outcome for Free Gracilis Muscle Transfer?

Introduction: During a two-stage free gracilis muscle transfer (FGMT) to restore smile to patients with facial paralysis, some surgeons assess nerve regeneration through the cross-face nerve graft (CFNG) with the Tinel sign and a nerve biopsy. Objective: To test whether ultimate smile reanimation outcomes are correlated with (1) the Tinel sign or (2) myelinated axons of the biopsied CFNG at the time of FGMT. Methods: Retrospective case series was performed at a tertiary care facial nerve center. Dynamic smile outcomes were quantified with Emotrics analysis of pre- and postoperative photographs. Results: Of the 113 FGMT surgeries by CFNG performed since 2002, 92 patients had pre- and postoperative photo-documentation. Most patients (89%, N = 82) had a positive Tinel sign at the time of FGMT; however, 14 patients with positive Tinel signs were deemed failures. Interestingly, 4 patients with a negative Tinel sign went on to have successful dynamic outcomes and 16 patients lacking myelinated axons in their CFNG biopsy ultimately achieved successful smile outcomes. Conclusion: Although the majority of patients had a positive Tinel sign and myelinated axons in the CFNG at the time of FGMT, the presence or absence of either factor did not predict ultimate smile outcome in this series.

Comparison of results utilizing one-step and two-step triple innervation techniques

A retrospective comparison between two groups of patients who underwent one-step or two-step triple innervation was performed to reveal the role of scar tissue in axonal regeneration. The surgical technique used was the same in all cases, but the first group underwent a one-time triple innervation procedure, while patients in the second group underwent delayed performance of neurorrhaphies between the distal ends of the cross-face grafts and the terminal branches of the injured facial nerve. The Wilcoxon signed-rank test for paired groups showed a statistically significant improvement in both facial symmetry and voluntary movements in both groups of patients. Separately, the Mann-Whitney test confirmed no statistically significant difference between the two groups regarding the restoration of facial symmetry and voluntary movements, and the development of postoperative synkinesis. A comparison of median values for each spontaneous parameter between the groups revealed greater effectiveness of the two-step surgery, with both blinking and laughing demonstrating better results. The greater effectiveness of the double-step technique in restoring spontaneous movements strongly supports the use of a two-stage triple innervation technique in patients with facial palsy.

Pre-implanted Sensory Nerve Could Enhance the Neurotization in Tissue-Engineered Bone Graft

In our previous study, it was found that implanting the sensory nerve tract into the tissue-engineered bone to repair large bone defects can significantly result in better osteogenesis effect than tissue-engineered bone graft (TEBG) alone. To study the behavior of the preimplanted sensory nerve in the TEBG, the TEBG was constructed by seeding bone mesenchymal stem cells into β-tricalcium phosphate scaffold with (treatment group) or without (blank group) implantation of the sensory nerve. The expression of calcitonin gene-related peptide (CGRP), which helps in the healing of bone defect in the treatment group was significantly higher than the blank group at 4, 8, and 12 weeks. The expression of growth-associated protein 43 (GAP43), which might be expressed during nerve healing in the treatment group, was significantly higher than the blank group at 4 and 8 weeks. The nerve tracts of the preimplanted sensory nerve were found in the scaffold by the nerve tracing technique. The implanted sensory nerve tracts grew into the pores of scaffolds much earlier than the vascular. The implanted sensory nerve tracts traced by Dil could be observed at 4 weeks, but at the same time, no vascular was observed. In conclusion, the TEBG could be benefited from the preimplanted sensory nerve through the healing behavior of the sensory nerve. The sensory nerve fibers could grow into the pores of the TEBG rapidly, and increase the expression of CGRP, which is helpful in regulating the bone formation and the blood flow.

Muscle reinnervation in one or two stages?: experimental study in rats with end-to-side nerve graft

PURPOSE: To compare muscle reinnervation in one and two surgical stages using end-to-side neurorrhaphy (ESN) without donor nerve injury. METHODS: The experiment was performed on four groups of 20 rats. Group 1 (G1), one stage, received the graft which was sutured to the tibial nerve, with ESN, and its free stump was sutured end-to-end to the distal stump of the sectioned peroneal nerve (PN), all in the same operation. In Group 2 (G2), two stages, the nerve graft was sutured to the tibial nerve, with ESN. Two months later the PN was sectioned and its distal stump connected to the distal stump of the graft as in G1. Normal control group (Gn) received the graft only sutured to the tibial nerve, with ESN. Denervated control group (Gd), as well received the graft and had the PN sectioned and its two stumps buried in adjacent musculature, with the aim of denervating the cranial tibial muscle (CTM), the target of this study. The parameters used to evaluate CTM reinnervation were muscle mass, muscle fiber's minimum diameter and area. RESULTS: The mean CTM mass, the average of the muscular fibers areas and the average of the muscular fiber minimum diameters was higher (all p<0.0001) in G2 than in G1. Comparing the four groups, these parameters had their maximum expression in Gn and the minimum in Gd, as expected. CONCLUSION: The two stages showed better muscle reinnervation than one stage.

Long-term outcomes of free-muscle transfer for smile restoration in adults

BACKGROUND

The cross-facial nerve grafting/free-muscle transfer strategy for smile restoration is superior to static reconstruction or regional muscle transposition. The purpose of this study was to evaluate the long-term outcomes of this technique in adult patients.

METHODS

Eighty-one adult patients received a free-muscle transfer for midface reanimation in the authors' center. Of this group, the authors identified 24 cases with follow-up of 5 years or longer. Smile symmetry and function were evaluated at three points: preoperatively, early postoperatively, and at long-term follow-up. To better evaluate the effect of time, patients were divided into groups according to the length of follow-up: group A, 5 to 6 years; group B, 7 to 10 years; group C, 11 to 15 years; and group D, more than 15 years. Four independent observers rated each patient's smile using a five-category scale ranging from poor to excellent. Panelists were asked to comment on whether the patient's smile weakened over time.

RESULTS

All patients obtained higher scores at 2 years from free-muscle transfer in comparison with their preoperative rates (p < 0.0001). Late outcomes demonstrated that muscle regeneration continues beyond the initial 2 years, with a further increase of the scores and motor units on electromyography at the late follow-up (p < 0.0001, p = 0.0313). No significance was found when comparing both variables among the four groups, indicating that time does not have a differential effect on muscle function. In 80 percent of the evaluations, the four observers agreed on maintained smile symmetry over time.

CONCLUSIONS

Cross-facial nerve grafting/free-muscle transfer is an effective technique for smile restoration in late facial paralysis. These data indicate maintenance of effective muscle function and progressive improvement with time.

Anatomy of the motor nerve to the gracilis muscle and its implications in a one-stage microneurovascular gracilis transfer for facial reanimation

BACKGROUND

The present study was conducted to investigate the anatomy of the motor nerve to the gracilis muscle (MNG) to provide the anatomical basis for harvesting a one-stage gracilis transfer with a long nerve for re-animation of the paralysed face.

METHODS

An anatomical study was performed on 24 lower-limb specimens (from the pelvis down to the knee) from 12 embalmed cadavers. The MNG was dissected from the surface of the muscle to the obturator foramen. Two anatomical regions were defined in the course of the nerve. The first region includes the part of the nerve that can easily be reached through a standard incision in the medial aspect of the thigh, that is, from the surface of the muscle to the posterior border of the adductor brevis muscle and the second region from there to the obturator foramen. Measurements of both anatomical regions and the maximum length of the nerve were taken with a calliper. The anatomical relations of the nerve were also noted and photo-documented.

RESULTS

The median maximum length of the MNG from the surface of gracilis to the posterior border of adductor brevis ('first anatomical region') was 7.7 cm (Range 6.3-10.5 cm); from there to the obturator foramen ('second anatomical region') the length was 3.7 cm (Range 2-6 cm), giving a median length of dissection of the nerve as 11.5 cm (Range 9.9-13.6 cm). Intraneural dissection of the MNG has to be performed proximally in the course of the nerve (the part corresponding to the second anatomical region), just where it runs inside the fascia over the obturator externus muscle.

CONCLUSIONS

Over 10-cm length of the MNG can be obtained when dissected along the course of the nerve up to the obturator foramen. To achieve the maximum length, intraneural dissection must normally be performed after the nerve passes the posterior border of the adductor brevis. An endoscopic approach or extended proximal incision is recommended to easily reach the proximal part of the nerve as far as the obturator foramen.

Free functional muscle transplantation for facial reanimation: experimental comparison between the one- and two-stage approach

To investigate functional results of either one- or two-staged free muscle transplantation the scutuloauricularis model in the New Zealand white rabbit was used. Thirty rabbits were allocated to two groups with 15 animals each. In Group 1 (one-stage approach) peroneus brevis (PB) was harvested as a free muscle graft with a 7cm long motor branch. The graft was positioned instead of right scutuloauricularis (SCUT) and its vascular supply microsurgically re-established. The motor branch was transferred to the contralateral side and its proximal end coapted to the cut facial motor branch to left SCUT. Before nerve coaptation biopsies were harvested from the cut motor branch for morphological analysis. In Group 2 (two-stage approach) a 7cm long saphenous nerve graft was taken and coapted to the cut motor branch of SCUT and crossed over to the contralateral side. Nerve specimens from the cut motor branch were taken. Eight months later the free transplantation of PB was performed and its motor branch coapted to the distal end of the cross-over nerve graft. After a total time period of 13 months the final experiments were carried out in each group. Maximal tetanic tensions in reinnervated PB were measured and biopsies of muscle grafts together with nerve biopsies from the distal part of the motor branch were harvested for morphological analysis. Muscle grafts of Group 1 revealed tetanic tension values of 12.5N (SD 3.1) in comparison to 10.6N (SD 3.5) obtained in Group 2. This difference was not statistically significant (p=0.303). In Group 1, the amount of regenerated nerve fibers counted at the distal motor branch site (mean: 2798, SD 1242) was significantly higher (p=0.008) than in Group 2 (mean: 1138, SD 1004). Muscle graft morphology revealed significantly less Type I fibers (p=0.016) and more Type IIb/d fibers (p=0.011) in Group 1 compared to Group 2. However, the overall amount of perimysial connective tissue showed no significant difference in both groups (p=0.478). Free muscle transplantation in a one-stage approach offers similar functional results in comparison to the two-stage approach. Although muscle grafts of the one-stage transplantation underwent a longer period of denervation similar contents of perimysial connective tissue could be observed.

Successful intramuscular neurotization is dependent on the denervation period. A histomorphological study of the gracilis muscle in rats

To characterize the extent to which reinnervation potential depends on the duration of denervation, intramuscular neurotization of the gracilis muscle was performed either immediately or 2, 4, 6, and 8 weeks after transection of the obturator nerve. For neurotization, the sciatic nerve was split into three fascicle groups and fixed intramuscularly. Muscle morphology after 6 weeks of regeneration was identified with anti-myosin immunohistochemistry and NADH staining. Newly formed motor endplates were characterized using acetylcholinesterase staining and electron microscopy. Wet muscle weight ratio indicated the functional state of synapses. Depending on the denervation period, three levels of regenerative outcome were evident. Best results were seen after immediate neurotization or after 2 weeks of denervation. Regeneration, although at a significantly lower level, also occurred after denervation periods of 4 and 6 weeks. Regeneration following neurotization after 8 weeks of denervation was negligible. Quantity and quality of motor endplate formation depended on the denervation period. Thus, in special clinical situations intramuscular neurotization within a distinct time window provides a good reconstructive option.