Laser-assisted nerve repair. Laser-trimming of nerve ends with epineurial suture anastomosis

Comparison of microsuture, interpositional nerve graft, and laser solder weld repair of the rat inferior alveolar nerve

PURPOSE

Intraosseous repair of nerves involves difficulty of access and there is concern that bone healing may interfere with repair outcomes. The present report describes the effect of 3 separate repair techniques on recovery from section of the rat intraosseous inferior alveolar nerve, with reference to the mental nerve distal and the trigeminal ganglion proximal to the nerve section.

MATERIALS AND METHODS

Unilateral exposure of the inferior alveolar nerves of 28 rats was achieved through bone windows. Nerves were sectioned and rats were assigned to 1 of 4 groups (n = 7): untreated controls, microsuture repair, interpositional nerve grafts from the femoral nerve, or laser solder weld repair. Animals were sacrificed 1 year after surgery for histologic evaluation of the mental nerve, inferior alveolar nerve, and trigeminal ganglion compared with unoperated contralateral nerves.

RESULTS

Compared with the unoperated contralateral nerves, nerve section substantially decreased mental nerve fiber number, mental nerve myelination, mental nerve fiber diameter, inferior alveolar nerve vascularity, trigeminal neuron number, and trigeminal neuron horseradish peroxidase tracer uptake and increased trigeminal ganglion degenerate neurons (P < .001). All 3 forms of repair substantially decreased these effects (P < .05). Interpositional nerve graft was least effective (P < .05). Nonetheless, mental nerve fiber diameter was significantly decreased compared with unsectioned nerves after microsuture and laser solder weld repair (P < .05).

CONCLUSIONS

Intraosseous repair of the inferior alveolar nerve decreases peripheral and central signs of degeneration. Clinical hyperesthesia after repair may reflect a predominance of small fibers after recovery.

Conduction velocity of the rabbit facial nerve: a noninvasive functional evaluation

The aim of this study was to evaluate standardized conduction velocity data for uninjured facial nerve and facial nerve repaired with autologous graft nerves and synthetic materials. An evaluation was made measuring the preoperative differences in the facial nerve conduction velocities on either side, and ascertaining the existence of a positive correlation between facial nerve conduction velocity and the number of axons regenerated postoperatively. In 17 rabbits, bilateral facial nerve motor action potentials were recorded pre- and postoperatively. The stimulation surface electrodes were placed on the auricular pavilion (facial nerve trunk) and the recording surface electrodes were placed on the quadratus labii inferior muscle. The facial nerves were isolated, transected and separated 10 mm apart. The gap between the two nerve ends was repaired with autologous nerve grafts and PTFE-e (polytetrafluoroethylene) or collagen tubes. The mean of maximal conduction velocity of the facial nerve was 41.10 m/s. After 15 days no nerve conduction was evoked in the evaluated group. For the period of 2 and 4 months the mean conduction velocity was approximately 50% of the normal value in the subgroups assessed. A significant correlation was observed between the conduction velocity and the number of regenerated axons. Noninvasive functional evaluation with surface electrodes can be useful for stimulating and recording muscle action potentials and for assessing the functional state of the facial nerve.

Effect of the CO2 milliwatt laser on tensile strength of microsutures

BACKGROUND AND OBJECTIVE

Laser-assisted tissue repair is often accompanied by a high dehiscence rate, which may be due to alterations in suture material after laser exposure. The goal of this study was to investigate the effect of CO2 laser irradiation on the tensile strength of microsurgical suture material.

STUDY DESIGN/MATERIALS AND METHODS

10-0 nylon and 25 microns stainless steel threads were exposed to 12 combinations of power densities (62, 124, and 186 W/cm2) and pulse durations (0.5, 1, 2, 3 s) and tested on a tensometer for their tensile strength.

RESULTS

At power densities of 186 W/cm2, the 10-0 nylon thread disrupted during laser irradiation, regardless of pulse duration. This was also the case at power densities of 124 C/cm2 for 2 s and 3 s pulse duration. At 124 W/cm2 for 0.5 and 1 s, the tensile strength decreased with 70% relative to the control. At 62 W/cm2, the tensile strength gradually decreased from 100% (0.5 s pulse duration) to 50% (3 s pulse duration) relative to control. Stainless steel thread resisted all laser irradiations.

CONCLUSIONS

The 10-0 nylon thread is significantly compromised by irradiation with the CO2 milliwatt laser and therefore meticulous care should be taken not be irradiate the sutures during laser tissue welding.

Stabilization and accurate trimming of nerve ends: practical use of fibrin glue: technical note

OBJECTIVE

Peripheral nerve transection usually results in protrusion of the endoneurial contents ("mushrooming"). Trimming of the nerve ends before repair is often necessary to achieve cut nerve end planes. In this technical report, we describe a technique for stabilization and accurate trimming of nerve ends using fibrin glue.

SURGICAL TECHNIQUE

The nerve ends of divided peripheral nerves are coated with fibrin glue and subsequently trimmed using a razor blade before repair.

RESULTS

When fibrin glue is applied, a firm layer with a rubbery consistency is formed around the nerve. This layer stabilizes the nerve ends during trimming, and a clear-cut plane of the nerve can be achieved. Moreover, the fibrin glue stabilizes the nerve ends during manipulations caused by suturing of the nerve.

CONCLUSION

The technique results in easier handling of the nerve during trimming and manipulation, minimal tissue damage to the nerve, and a clear-cut plane of the nerve.